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Materials, Volume 10, Issue 7 (July 2017) – 163 articles

Cover Story (view full-size image): Structural health monitoring often leverages on strain wave analysis for the reconstruction of passive impact force and the identification of active Lamb wave impact damage. A fiber optic-based interferometric architecture associated to an innovative coherent detection scheme is proposed in this paper for high frequency dynamics detection. Different sensor configurations are tested and the signals are validated with a piezoelectric transducer. A finite element model is also used for verification. View the paper
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4154 KiB  
Article
Construction of a Novel Three-Dimensional PEDOT/RVC Electrode Structure for Capacitive Deionization: Testing and Performance
by Ali Aldalbahi, Mostafizur Rahaman, Periyasami Govindasami, Mohammed Almoiqli, Tariq Altalhi and Amine Mezni
Materials 2017, 10(7), 847; https://doi.org/10.3390/ma10070847 - 24 Jul 2017
Cited by 9 | Viewed by 4490
Abstract
This article discusses the deposition of different amount of microstuctured poly(3,4-ethylenedioxythiophene) (PEDOT) on reticulated vitreous carbon (RVC) by electrochemical method to prepare three-dimensional (3D) PEDOT/RVC electrodes aimed to be used in capacitive deionization (CDI) technology. A CDI unit cell has been constructed here [...] Read more.
This article discusses the deposition of different amount of microstuctured poly(3,4-ethylenedioxythiophene) (PEDOT) on reticulated vitreous carbon (RVC) by electrochemical method to prepare three-dimensional (3D) PEDOT/RVC electrodes aimed to be used in capacitive deionization (CDI) technology. A CDI unit cell has been constructed here in this study. The performance of CDI cell in the ion removal of NaCl onto the sites of PEDOT/RVC electrode has been systematically investigated in terms of flow-rate, applied electrical voltage, and increasing PEDOT loading on PEDOT/RVC electrodes. It is observed that the increase in flow-rate, electric voltage, and PEDOT loading up to a certain level improve the ion removal performance of electrode in the CDI cell. The result shows that these electrodes can be used effectively for desalination technology, as the electrosorption capacity/desalination performance of these electrodes is quite high compared to carbon materials. Moreover, the stability of the electrodes has been tested and it is reported that these electrodes are regenerative. The effect of increasing NaCl concentration on the electrosorption capacity has also been investigated for these electrodes. Finally, it has been shown that 1 m3 PEDOT-120 min/RVC electrodes from 75 mg/L NaCl feed solution produce 421, 978 L water per day of 20 mg/L NaCl final concentration. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic diagram of a capacitive deionization (CDI) cell (<b>a</b>) unit cell; (<b>b</b>) flow through cell; and (<b>c</b>) top of the cell.</p> Full article ">Figure 2
<p>(<b>a</b>) Effect of applied voltage on electrosorption at a PEDOT-20 min/RVC composite electrode using a 35 mL/min flow-rate and 75 mg/L NaCl feed solution; (<b>b</b>) Plot of electrosorption capacity as a function of electrical voltage.</p> Full article ">Figure 3
<p>Effect of flow-rate on the electrosorption behaviour of PEDOT-20 min/RVC composite electrode. Applied voltage: 0.8 V; Concentration of NaCl feed solution: 75 mg/L.</p> Full article ">Figure 4
<p>Effect of PEDOT loading of PEDOT/RVC electrode on ions removal efficiency using a CDI system. Applied voltage: 0.8 V; NaCl feed solution concentration: 75 mg/L; Flow-rate: 80 mL/min.</p> Full article ">Figure 5
<p>Effect of PEDOT loading of PEDOT/RVC electrodes on electrosorption as reported in terms of mass of PEDOT, and geometric volume of the PEDOT/RVC electrode.</p> Full article ">Figure 6
<p>Multiple electrosorption–desorption and current response cycles for PEDOT-120 min/RVC electrode upon polarization and depolarization at 0.8 and 0.0 V, respectively. NaCl feed solution concentration: 75 mg/L.</p> Full article ">Figure 7
<p>Electrosorption capacity of PEDOT-120 min/RVC composite electrode at varous concentrations of NaCl feed solution. Applied voltage: 0.8 V; Flow-rate: 80 mL/min.</p> Full article ">Figure 8
<p>(<b>a</b>) Calibration curve of electrosorption vs. concentration of NaCl feed solution; (<b>b</b>) Concentration of feed solution vs. desalination cycles number for full desalination process to produce water of less than 1 mg/L NaCl concentration.</p> Full article ">
2720 KiB  
Article
Quantitative Immobilization of Phthalocyanine onto Bacterial Cellulose for Construction of a High-Performance Catalytic Membrane Reactor
by Shiliang Chen and Qiaoling Teng
Materials 2017, 10(7), 846; https://doi.org/10.3390/ma10070846 - 24 Jul 2017
Cited by 17 | Viewed by 4522
Abstract
We report the fabrication of a tetra-amino cobalt (II) phthalocyanine (CoPc)-immobilized bacterial cellulose (BC) functional nanocomposite, CoPc@BC, by quantitative immobilization of CoPc onto a BC membrane. Lab-cultured BC was oxidized by NaIO4 to generate aldehyde groups on BC for the subsequent CoPc [...] Read more.
We report the fabrication of a tetra-amino cobalt (II) phthalocyanine (CoPc)-immobilized bacterial cellulose (BC) functional nanocomposite, CoPc@BC, by quantitative immobilization of CoPc onto a BC membrane. Lab-cultured BC was oxidized by NaIO4 to generate aldehyde groups on BC for the subsequent CoPc immobilization, the processing conditions were optimized by monitoring both the generated aldehyde content and the resulting CoPc loading. X-ray photoelectron spectroscopy (XPS) was employed to characterize the change of the element bonding environment during the functionalization processes. The CoPc@BC functional nanocomposite was utilized for the treatment of reactive red X-3B dye wastewater. The CoPc molecules in the CoPc@BC nanocomposite can function as an “antenna” to adsorb the target anionic dye molecules, the adsorption takes place both on the surface and in the interior of CoPc@BC. A catalytic membrane reactor (CMR) was assembled with the CoPc@BC nanocomposite, the performance of CMR was evaluated based on the catalytic oxidation behavior of reactive red X-3B, with H2O2 as an oxidant. Highly-reactive hydroxyl radical (OH) was involved in the catalytic oxidation process, as detected by electron paramagnetic resonance (EPR). Under optimal operating conditions of a flow rate of 6 mL/min, a reaction temperature of 50 °C, and an H2O2 concentration of 10 mmol/L, the decoloration rate of CMR was as high as 50 μmol⋅min−1⋅g−1. Full article
(This article belongs to the Section Advanced Composites)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Synthesis route of CoPc@BC.</p> Full article ">Figure 2
<p>(<b>a</b>) Schematic representation of the CoPc@BC-based catalytic membrane reactor (CMR); (<b>b</b>) Optical image of the CoPc@BC-based CMR.</p> Full article ">Figure 3
<p>XPS spectra of (<b>a</b>) BC; (<b>b</b>) oxidized BC; and (<b>c</b>) CoPc@BC. The window included shows, in detail, the Co region.</p> Full article ">Figure 4
<p>Curve fit of (<b>a</b>) O1s peaks of BC; (<b>b</b>) O1s peaks of oxidized BC; (<b>c</b>) O1s peaks of CoPc@BC; and (<b>d</b>) N1s peaks of CoPc@BC.</p> Full article ">Figure 5
<p>Effect of NaIO<sub>4</sub> concentration on CoPc loading of CoPc@BC (filled square) and aldehyde content of BC (filled circle), T = 30 °C, reaction time = 8 h.</p> Full article ">Figure 6
<p>Concentration changes of reactive red X-3B (initial concentration: 1 × 10<sup>−4</sup> mol/L, T = 50 °C) with CoPc@BC (1.60 mg) adsorption: (<b>a</b>) effect of pH; and (<b>b</b>) the effect of CoPc loading.</p> Full article ">Figure 7
<p>XPS of the cross-section of CoPc@BC after dye adsorption. <b>Left</b> inset: detail of the Co region, <b>middle</b> inset: detail of the Cl region; and <b>right</b> inset: detail of the S region.</p> Full article ">Figure 8
<p>Typical concentration changes of reactive red X-3B (T = 50 °C, pH = 2) with CoPc@BC (1.60 mg) and H<sub>2</sub>O<sub>2</sub> (10 mmol/L) under various flow rates. Inset: Effect of flow rate on the decoloration rate of reactive red X-3B.</p> Full article ">Figure 9
<p>XPS of cross-section of CoPc@BC after catalytic oxidation. <b>Left</b> inset: detail of Co region, <b>middle</b> inset: detail of Cl region, <b>right</b> inset: detail of S region.</p> Full article ">Figure 10
<p>DMPO spin-trapping EPR spectra of reactive red X-3B dye solution (initial concentration: 1 × 10<sup>−4</sup> mol/L, CoPc@BC: 1.60 mg, T = 50 °C).</p> Full article ">Figure 11
<p>Conceptual representation of catalytic oxidation of reactive red X-3B with CoPc@BC/H<sub>2</sub>O<sub>2</sub> reaction system.</p> Full article ">
3319 KiB  
Article
On Identification of Critical Material Attributes for Compression Behaviour of Pharmaceutical Diluent Powders
by Jianyi Zhang, Chuan-Yu Wu, Xin Pan and Chuanbin Wu
Materials 2017, 10(7), 845; https://doi.org/10.3390/ma10070845 - 23 Jul 2017
Cited by 36 | Viewed by 5807
Abstract
As one of the commonly-used solid dosage forms, pharmaceutical tablets have been widely used to deliver active drugs into the human body, satisfying patient’s therapeutic requirements. To manufacture tablets of good quality, diluent powders are generally used in formulation development to increase the [...] Read more.
As one of the commonly-used solid dosage forms, pharmaceutical tablets have been widely used to deliver active drugs into the human body, satisfying patient’s therapeutic requirements. To manufacture tablets of good quality, diluent powders are generally used in formulation development to increase the bulk of formulations and to bind other inactive ingredients with the active pharmaceutical ingredients (APIs). For formulations of a low API dose, the drug products generally consist of a large fraction of diluent powders. Hence, the attributes of diluents become extremely important and can significantly influence the final product property. Therefore, it is essential to accurately characterise the mechanical properties of the diluents and to thoroughly understand how their mechanical properties affect the manufacturing performance and properties of the final products, which will build a sound scientific basis for formulation design and product development. In this study, a comprehensive evaluation of the mechanical properties of the widely-used pharmaceutical diluent powders, including microcrystalline cellulose (MCC) powders with different grades (i.e., Avicel PH 101, Avicel PH 102, and DG), mannitol SD 100, lactose monohydrate, and dibasic calcium phosphate, were performed. The powder compressibility was assessed with Heckel and Kawakita analyses. The material elastic recovery during decompression and in storage was investigated through monitoring the change in the dimensions of the compressed tablets over time. The powder hygroscopicity was also evaluated to examine the water absorption ability of powders from the surroundings. It was shown that the MCC tablets exhibited continuous volume expansion after ejection, which is believed to be induced by (1) water absorption from the surrounding, and (2) elastic recovery. However, mannitol tablets showed volume expansion immediately after ejection, followed by the material shrinkage in storage. It is anticipated that the expansion was induced by elastic recovery to a limited extent, while the shrinkage was primarily due to the solidification during storage. It was also found that, for all powders considered, the powder compressibility and the elastic recovery depended significantly on the particle breakage tendency: a decrease in the particle breakage tendency led to a slight decrease in the powder compressibility and a significant drop in immediate elastic recovery. This implies that the particle breakage tendency is a critical material attribute in controlling the compression behaviour of pharmaceutical powders. Full article
(This article belongs to the Special Issue Materials for Drug Delivery and Biomedical Consideration)
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Figure 1

Figure 1
<p>Heckel yield pressure as a function of compression pressure for different diluent powders: (■) MCC PH 101, (●) MCC PH 102, (▲) MCC DG, (◇) Mannitol SD 100, (□) lactose, and (○) dibasic calcium phosphate.</p> Full article ">Figure 2
<p>The average Heckel yield pressures for different diluent powders.</p> Full article ">Figure 3
<p>The Kawakita parameters <b>a</b> and <b>1/b</b> for different diluent powders.</p> Full article ">Figure 4
<p>The relative density <math display="inline"> <semantics> <mrow> <msub> <mstyle mathvariant="bold-sans-serif" mathsize="normal"> <mi>ρ</mi> </mstyle> <mstyle mathvariant="bold" mathsize="normal"> <mi>A</mi> </mstyle> </msub> </mrow> </semantics> </math> for different diluent powders.</p> Full article ">Figure 5
<p>The values of parameter <math display="inline"> <semantics> <mrow> <msub> <mstyle mathvariant="bold-sans-serif" mathsize="normal"> <mi>ρ</mi> </mstyle> <mn mathvariant="bold">0</mn> </msub> </mrow> </semantics> </math> (i.e. the significance of particle rearrangement) for different diluent powders.</p> Full article ">Figure 6
<p>SEM images of MCC PH 102 (<b>a</b>) and mannitol SD 100 (<b>b</b>) [<a href="#B33-materials-10-00845" class="html-bibr">33</a>].</p> Full article ">Figure 7
<p>The parameter <math display="inline"> <semantics> <mrow> <msub> <mstyle mathvariant="bold-sans-serif" mathsize="normal"> <mi>ρ</mi> </mstyle> <mstyle mathvariant="bold" mathsize="normal"> <mi>B</mi> </mstyle> </msub> </mrow> </semantics> </math> for different powders, indicating the significance of particle fragmentation for different diluent powders.</p> Full article ">Figure 8
<p>The average IERs for the different materials investigated.</p> Full article ">Figure 9
<p>(<b>a</b>) The accumulated volume changes of MCC PH 102 tablets compressed at different pressures (<b>■</b>) 68 MPa, (<b>▲</b>) 120 MPa, (<b>○</b>) 210 MPa, and (<b>◇</b>) 300 MPa, versus the storage time; (<b>b</b>) The average volume expansion at different compression pressures.</p> Full article ">Figure 10
<p>The accumulated volume changes of mannitol tablets compressed at different pressures (■) 68 MPa, (▲ ) 120 MPa, (○) 210 MPa, and (◇ ) 300 MPa.</p> Full article ">Figure 11
<p>The water contents of different powders stored at different environmental humidity. Key: (■) MCC PH 101, (●) MCC PH 102, (▲) MCC DG, (◇) Mannitol SD 100, (□) lactose, and (○) dibasic calcium phosphate.</p> Full article ">Figure 12
<p>The relationship between the particle breakage (i.e., the breakage parameter <math display="inline"> <semantics> <mrow> <msub> <mstyle mathvariant="bold-sans-serif" mathsize="normal"> <mi>ρ</mi> </mstyle> <mstyle mathvariant="bold" mathsize="normal"> <mi>b</mi> </mstyle> </msub> </mrow> </semantics> </math> from Heckel analysis) and the powder compressibility (i.e., the Kawakita parameter <b>a</b>) with a compression pressure of 170 MPa.</p> Full article ">Figure 13
<p>The relationship between the particle breakage (i.e., the breakage parameter <math display="inline"> <semantics> <mrow> <msub> <mstyle mathvariant="bold-sans-serif" mathsize="normal"> <mi>ρ</mi> </mstyle> <mstyle mathvariant="bold" mathsize="normal"> <mi>b</mi> </mstyle> </msub> </mrow> </semantics> </math> from Heckel analysis) and the in-die elastic recovery for different powders at a compression pressure of 170 MPa.</p> Full article ">
2570 KiB  
Article
Zinc Sorption Studies on Pectin-Based Biosorbents
by Agata Jakóbik-Kolon, Krzysztof Mitko and Joanna Bok-Badura
Materials 2017, 10(7), 844; https://doi.org/10.3390/ma10070844 - 22 Jul 2017
Cited by 11 | Viewed by 4328
Abstract
The previously-obtained and characterized hybrid pectin-based beads containing agar-agar and guar gum, as well as sole pectin beads (P, for comparison) were examined for zinc ions sorption and desorption properties. The sorption kinetics and equilibrium in the studied system was described by two [...] Read more.
The previously-obtained and characterized hybrid pectin-based beads containing agar-agar and guar gum, as well as sole pectin beads (P, for comparison) were examined for zinc ions sorption and desorption properties. The sorption kinetics and equilibrium in the studied system was described by two kinetic models (pseudo-first- and pseudo-second-order) and two isotherms (Langmuir and Freundlich), respectively. The desorption kinetics and equilibrium was also investigated by applying various inorganic acids (nitric, hydrochloric, and sulfuric acid) of various concentrations. In the case of guar gum additive, no significant change in sorption capacity compared to sole pectin beads was observed (q: 37.0 ± 2.6 and 34.7 ± 2.0 mg/g, respectively). Addition of agar-agar significantly decreased the sorption capacity to 22.3 ± 1.0 mg/g, but stripping of zinc(II) ions from this biosorbent was complete even with very diluted acids (0.01 M). Total desorption of zinc from sole pectin and pectin-guar gum beads required acid solution of higher concentration (0.1 M). Sorption rates for all biosorbents are roughly the same and maximum sorption is achieved after 4–5 h. Obtained results and the advantage of our sorbent’s shape formation ability, make the pectin-based biosorbents interesting alternative for zinc(II) ions removal. Full article
(This article belongs to the Special Issue Sorption Materials for Environment Purification)
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Figure 1

Figure 1
<p>The effect of the sorbent dose on zinc(II) ions sorption on pectin based biosorbents: (<b>a</b>) hybrid pectin biosorbent with agar (P+A); and (<b>b</b>) hybrid pectin biosorbent with guar gum (P + G). (R) percentage of zinc removal [%], (q) sorption capacity [mg/g].</p> Full article ">Figure 2
<p>Sorption kinetics of zinc(II) ions on pectin—based biosorbents. Pseudo-first-order model: (<b>a</b>) hybrid pectin biosorbent with agar (P + A); (<b>b</b>) hybrid pectin biosorbent with guar gum (P + G); (<b>c</b>) sole pectin biosorbent (P) and pseudo-second order model; (<b>d</b>) hybrid pectin biosorbent with agar (P + A); (<b>e</b>) hybrid pectin biosorbent with guar gum (P + G); and (<b>f</b>) sole pectin biosorbent (P). Mass of sorbent 0.75 g, initial concentration of metal: c = 30 mg/L, volume of solution: 0.5 L, pH = 6, temperature 22 ± 1 °C.</p> Full article ">Figure 3
<p>Sorption isotherms of zinc on pectin-based biosorbents. Langmuir model: (<b>a</b>) hybrid pectin biosorbent with agar (P + A); (<b>b</b>) hybrid pectin biosorbent with guar gum (P + G); (<b>c</b>) sole pectin biosorbent (P) and Freundlich model; (<b>d</b>) hybrid pectin biosorbent with agar (P + A); (<b>e</b>) hybrid pectin biosorbent with guar gum (P + G); (<b>f</b>) sole pectin biosorbent (P). Mass of sorbent 0.03 g, volume of solution: 0.02 L, pH = 6, temperature 22 ± 1 °C, time of contact 24 h.</p> Full article ">Figure 4
<p>Comparison of zinc(II) ions desorption from pectin-based biosorbents (P + A—hybrid pectin biosorbent with agar, P + G—hybrid pectin biosorbent with guar gum, P—sole pectin biosorbent) using various acid solutions of various concentration. Mass of sorbent 0.03 g, volume of solution: 0.01 L, pH = 6, temperature 22 ± 1 °C, time of contact 24 h.</p> Full article ">Figure 5
<p>Kinetics of zinc(II) ions desorption from pectin-based biosorbents (P + A—hybrid pectin biosorbent with agar, P + G—hybrid pectin biosorbent with guar gum, P—sole pectin biosorbent) using various acid solutions of various concentration: (<b>a</b>,<b>b</b>) 0.01 M HNO<sub>3</sub>; (<b>c</b>,<b>d</b>) 0.1 M HNO<sub>3</sub>; (<b>e</b>,<b>f</b>) 0.01 M HCl; (<b>g</b>,<b>h</b>) 0.1 HCl; (<b>i</b>,<b>j</b>) 0.005 M H<sub>2</sub>SO<sub>4</sub>; and (<b>k</b>,<b>l</b>) 0.05 M H<sub>2</sub>SO<sub>4</sub>. Mass of sorbent 0.75 g, volume of solution: 0.25 L, temperature 22 ± 1 °C.</p> Full article ">Figure 5 Cont.
<p>Kinetics of zinc(II) ions desorption from pectin-based biosorbents (P + A—hybrid pectin biosorbent with agar, P + G—hybrid pectin biosorbent with guar gum, P—sole pectin biosorbent) using various acid solutions of various concentration: (<b>a</b>,<b>b</b>) 0.01 M HNO<sub>3</sub>; (<b>c</b>,<b>d</b>) 0.1 M HNO<sub>3</sub>; (<b>e</b>,<b>f</b>) 0.01 M HCl; (<b>g</b>,<b>h</b>) 0.1 HCl; (<b>i</b>,<b>j</b>) 0.005 M H<sub>2</sub>SO<sub>4</sub>; and (<b>k</b>,<b>l</b>) 0.05 M H<sub>2</sub>SO<sub>4</sub>. Mass of sorbent 0.75 g, volume of solution: 0.25 L, temperature 22 ± 1 °C.</p> Full article ">Figure 5 Cont.
<p>Kinetics of zinc(II) ions desorption from pectin-based biosorbents (P + A—hybrid pectin biosorbent with agar, P + G—hybrid pectin biosorbent with guar gum, P—sole pectin biosorbent) using various acid solutions of various concentration: (<b>a</b>,<b>b</b>) 0.01 M HNO<sub>3</sub>; (<b>c</b>,<b>d</b>) 0.1 M HNO<sub>3</sub>; (<b>e</b>,<b>f</b>) 0.01 M HCl; (<b>g</b>,<b>h</b>) 0.1 HCl; (<b>i</b>,<b>j</b>) 0.005 M H<sub>2</sub>SO<sub>4</sub>; and (<b>k</b>,<b>l</b>) 0.05 M H<sub>2</sub>SO<sub>4</sub>. Mass of sorbent 0.75 g, volume of solution: 0.25 L, temperature 22 ± 1 °C.</p> Full article ">
4182 KiB  
Article
Anti-Inflammatory, Immunomodulatory, and Tissue Repair Activity on Human Keratinocytes by Green Innovative Nanocomposites
by Pierfrancesco Morganti, Alessandra Fusco, Iole Paoletti, Brunella Perfetto, Paola Del Ciotto, Marco Palombo, Angelo Chianese, Adone Baroni and Giovanna Donnarumma
Materials 2017, 10(7), 843; https://doi.org/10.3390/ma10070843 - 22 Jul 2017
Cited by 44 | Viewed by 5149
Abstract
The use of raw materials obtained by waste and processed through innovative industrial methodologies has generated an industry of about a trillion dollars in a short time, and in the near future will provide resources and services for the conservation and sustainable use [...] Read more.
The use of raw materials obtained by waste and processed through innovative industrial methodologies has generated an industry of about a trillion dollars in a short time, and in the near future will provide resources and services for the conservation and sustainable use of natural resources in order to ensure a better and fairer welfare for the human race. The production of nano-fiber chitin non-woven tissue is in accordance with the Organization for Economic Co-operation and Development (OECD) and European Union (EU) bio-economic programs: 100% biodegradable, ecological, and therefore useful in decreasing dependence on fossil fuel resources. The aim of our study is the evaluation of different formulations of a non-woven tissue obtained from electrospinning of a mixture of nanochitin fibrils, lignin, and poly (ethylene) oxide (PEO) on the restoration of damaged tissues. Wound repair is a complex process that involves epithelial and immune cells and includes the induction of metalloproteinases, inflammatory mediators, and angiogenic factors. Our in vitro results have shown that all of the realized chitin nanofibrils-bio-lignin non-woven tissues tested as nontoxic for human keratinocytes (HaCat) cells. Furthermore, the bio-composites that included bio-lignin at 0.1% have been able to modulate the expression of pro-inflammatory cytokines (Tumor Necrosis Factor-α, IL-1α, and IL8), lipopolysaccharide (LPS)-induced, and matrix metalloproteinases (MMPs) and human beta-defensin 2 (HBD-2) expression in HaCat cells, suggesting an anti-inflammatory and immunomodulatory role. Taken together, our results suggest that our chitin nanofibrils-bio-lignin non-woven tissue represents a skin-friendly tool that is able to favor a correct and fast wound repair. Full article
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Figure 1
<p>Morphology of the Chitin Nanofibril bio-Lignin micro/nanoparticles at SEM microscopy. Magnification 1000KX. From: Morganti et al. J. of Clinical and Cosmetic Dermatology Vol.1:1, 2017; Open Access [<a href="#B22-materials-10-00843" class="html-bibr">22</a>].</p> Full article ">Figure 2
<p>Porous structure of bio-composite Chitin Nanofibril scaffold (left) Extracellular Matrix (ECM)-like (right) at SEM microscopy. From: Morganti et al. J. of Clinical and Cosmetic Dermatology Vol.1:1, 2017; Open Access [<a href="#B22-materials-10-00843" class="html-bibr">22</a>].</p> Full article ">Figure 3
<p>mRNA expression of Metalloproteinase-2 (MMP-2) from HaCat cells treated with S21, S30, S31, S35, S40, S41 and S42 non-woven tissue bio-composites (10 μg/mL) for 6 h (<b>a</b>) and 24 h (<b>b</b>). Data are mean ± SD of values calculated on two different experiments. * <span class="html-italic">P</span> &lt; 0.05 compared to Ctrl.</p> Full article ">Figure 4
<p>mRNA expression of Metalloproteinase-9 (MMP-9) from HaCat cells treated with S21, S30, S31, S35, S40, S41 and S42 non-woven tissue bio-composites (10 μg/mL) for 6 h (<b>a</b>) and 24 h (<b>b</b>). Data are mean ± SD of values calculated on two different experiments. * <span class="html-italic">P</span> &lt; 0.05 compared to Ctrl.</p> Full article ">Figure 5
<p>mRNA expression of HBD-2 from HaCat cells treated with S21, S30 , S31, S35, S40, S41 and S42 non-woven tissue bio-composites (10 μg/mL) for 6 h (<b>a</b>) and 24 h (<b>b</b>). Data are mean ± SD of values calculated on two different experiments. * <span class="html-italic">P</span> &lt; 0.05 compared to Ctrl.</p> Full article ">Figure 6
<p>mRNA expression of IL-1α from HaCat cells treated with S21, S30 , S31, S35, S40, S41 and S42 non-woven tissue bio-composites (10 μg/mL) plus <span class="html-italic">P. aeruginosa</span> lipopolysaccharide (LPS) (10 μg/mL) 6 h (<b>a</b>) and 24 h (<b>b</b>). Data are mean ± SD of values calculated on two different experiments. * <span class="html-italic">P</span> &lt; 0.05 compared to LPS (10 μg/mL) alone.</p> Full article ">Figure 7
<p>mRNA expression of IL-8 from HaCat cells treated with S21, S30 , S31, S35, S40, S41 and S42 non-woven tissue bio-composites (10 μg/mL) plus <span class="html-italic">P. aeruginosa</span> lipopolysaccharide (LPS) (10 μg/mL) 6 h (<b>a</b>) and 24 h (<b>b</b>). Data are mean ± SD of values calculated on two different experiments. * <span class="html-italic">P</span> &lt; 0.05 compared to LPS (10 μg/mL) alone.</p> Full article ">Figure 8
<p>mRNA expression of TNF-α from HaCat cells treated with S21, S30 , S31, S35, S40, S41 and S42 non-woven tissue bio-composites (10 μg/mL) plus <span class="html-italic">P. aeruginosa</span> lipopolysaccharide (LPS) (10 μg/mL) 6 h (<b>a</b>) and 24 h (<b>b</b>). Data are mean ± SD of values calculated on two different experiments. * <span class="html-italic">P</span> &lt; 0.05 compared to LPS (10 μg/mL) alone.</p> Full article ">
1700 KiB  
Article
Interaction of Shear and Rayleigh–Lamb Waves with Notches and Voids in Plate Waveguides
by Annamaria Pau and Dimitra V. Achillopoulou
Materials 2017, 10(7), 841; https://doi.org/10.3390/ma10070841 - 21 Jul 2017
Cited by 26 | Viewed by 4106
Abstract
This paper investigates the interaction of different shear- and Rayleigh–Lamb-guided waves in plates with a discontinuity such as a notch or an internal void. The problem was solved numerically using a finite element model and by exploiting an analytical solution obtainable for the [...] Read more.
This paper investigates the interaction of different shear- and Rayleigh–Lamb-guided waves in plates with a discontinuity such as a notch or an internal void. The problem was solved numerically using a finite element model and by exploiting an analytical solution obtainable for the double sharp changes of the cross-section that served as a reference. We aimed to elucidate the relation between the size and shape of the discontinuity and the reflection and transmission coefficients of the scattered field. Different sizes and profiles of the discontinuity were considered, with the shapes ranging from step changes of the height to ellipses, both symmetric and nonsymmetric. Regimes related to low and high values of the product frequency multiplied by the height of the plate were investigated. These showed how the mode conversion was related to the symmetry between the incident mode and the discontinuity, and to the actual existence of multiple propagating modes. The analysis presented was motivated by the need to set up procedures that exploit propagating waves not only to detect the presence of a notch, but also to characterize its size and shape. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)
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<p>Plate.</p> Full article ">Figure 2
<p>Phase (<b>a</b>) and group (<b>b</b>) velocity of shear waves in an aluminum plate.</p> Full article ">Figure 3
<p>Phase (<b>a</b>) and group (<b>b</b>) velocity of Rayleigh–Lamb waves in an aluminum plate.</p> Full article ">Figure 4
<p>Profiles of discontinuities and voids under investigation: external symmetric (<b>A</b>,<b>D</b>); internal symmetric (<b>B</b>,<b>E</b>); external nonsymmetric (<b>C</b>,<b>F</b>).</p> Full article ">Figure 5
<p>Time-history (<b>a</b>) and Fourier transform (<b>b</b>) of the forcing function.</p> Full article ">Figure 6
<p>Spatial distribution of forces used to generate SH0 (<b>a</b>) and S0 (<b>b</b>) waves.</p> Full article ">Figure 7
<p>Contour plot of <math display="inline"> <semantics> <msub> <mi>u</mi> <mn>2</mn> </msub> </semantics> </math> displacements at a time step following the interaction of the SH0 mode with an A-type discontinuity (2<span class="html-italic">hf</span> = 4 MHz mm).</p> Full article ">Figure 8
<p><math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <mn>00</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> (<b>a</b>) and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <mn>00</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> (<b>b</b>) for several values of <span class="html-italic">r</span> as a function of <math display="inline"> <semantics> <mrow> <mi>δ</mi> <mo>=</mo> <mi>d</mi> <mo>/</mo> <msub> <mi>λ</mi> <mi>w</mi> </msub> </mrow> </semantics> </math> (2<span class="html-italic">hf</span> = 1 MHz mm).</p> Full article ">Figure 9
<p><math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <mn>00</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <mn>00</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> as a function of <span class="html-italic">r</span> for <math display="inline"> <semantics> <mrow> <mi>δ</mi> <mo>=</mo> <mn>0.16</mn> </mrow> </semantics> </math> for rectangular (<b>a</b>) and elliptical (<b>b</b>) profiles of the notch.</p> Full article ">Figure 10
<p><math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <mn>00</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <mn>02</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> (<b>a</b>) and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <mn>00</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <mn>02</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> (<b>b</b>) as a function of <math display="inline"> <semantics> <mi>δ</mi> </semantics> </math> for <math display="inline"> <semantics> <mrow> <mi>r</mi> <mo>=</mo> <mn>0.1</mn> </mrow> </semantics> </math>.</p> Full article ">Figure 11
<p><math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <mn>00</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math>, <math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <mn>01</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <mn>02</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> (<b>a</b>,<b>c</b>,<b>e</b>) and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <mn>00</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math>, <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <mn>01</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <mn>02</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> (<b>b</b>,<b>d</b>,<b>f</b>) as a function of <span class="html-italic">r</span> for <math display="inline"> <semantics> <mrow> <mi>δ</mi> <mo>=</mo> <mn>0.16</mn> </mrow> </semantics> </math> for cases A–C.</p> Full article ">Figure 12
<p><math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <mn>00</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math>, <math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <mn>01</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <mn>02</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> (<b>a</b>,<b>c</b>,<b>e</b>) and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <mn>00</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math>, <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <mn>01</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <mn>02</mn> </mrow> <mrow> <mi>S</mi> <mi>H</mi> </mrow> </msubsup> </semantics> </math> (<b>b</b>,<b>d</b>,<b>f</b>) as a function of <span class="html-italic">r</span> for <math display="inline"> <semantics> <mrow> <mi>δ</mi> <mo>=</mo> <mn>0.16</mn> </mrow> </semantics> </math> for cases D–F.</p> Full article ">Figure 13
<p>Contour plot of <math display="inline"> <semantics> <msub> <mi>u</mi> <mn>1</mn> </msub> </semantics> </math> displacements at a time step following the interaction of the S0 mode with an A-type discontinuity (<math display="inline"> <semantics> <mrow> <mn>2</mn> <mi>h</mi> <mi>f</mi> </mrow> </semantics> </math> = 1 MHz mm).</p> Full article ">Figure 14
<p>Contour plot of <math display="inline"> <semantics> <msub> <mi>u</mi> <mn>1</mn> </msub> </semantics> </math> displacements at a time step following the interaction of the S0 mode with a C-type discontinuity (<math display="inline"> <semantics> <mrow> <mn>2</mn> <mi>h</mi> <mi>f</mi> </mrow> </semantics> </math> = 1 MHz mm).</p> Full article ">Figure 15
<p><math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <msub> <mi>S</mi> <mn>0</mn> </msub> <msub> <mi>S</mi> <mn>0</mn> </msub> </mrow> <mrow> <mi>R</mi> <mi>L</mi> </mrow> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <msub> <mi>S</mi> <mn>0</mn> </msub> <msub> <mi>S</mi> <mn>0</mn> </msub> </mrow> <mrow> <mi>R</mi> <mi>L</mi> </mrow> </msubsup> </semantics> </math> for <math display="inline"> <semantics> <mi>δ</mi> </semantics> </math> = 0.13 (<b>a</b>) and <math display="inline"> <semantics> <mi>δ</mi> </semantics> </math> = 0.07 (<b>b</b>) for the A-type discontinuity.</p> Full article ">Figure 16
<p><math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <msub> <mi>S</mi> <mn>0</mn> </msub> <msub> <mi>S</mi> <mn>0</mn> </msub> </mrow> <mrow> <mi>R</mi> <mi>L</mi> </mrow> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <msub> <mi>S</mi> <mn>0</mn> </msub> <msub> <mi>S</mi> <mn>0</mn> </msub> </mrow> <mrow> <mi>R</mi> <mi>L</mi> </mrow> </msubsup> </semantics> </math> for rectangular (<b>a</b>) and elliptical voids (<b>b</b>); <math display="inline"> <semantics> <mrow> <mi>δ</mi> <mo>=</mo> <mn>0.07</mn> </mrow> </semantics> </math>.</p> Full article ">Figure 17
<p><math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <msub> <mi>S</mi> <mn>0</mn> </msub> <msub> <mi>S</mi> <mn>0</mn> </msub> </mrow> <mrow> <mi>R</mi> <mi>L</mi> </mrow> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <msub> <mi>S</mi> <mn>0</mn> </msub> <msub> <mi>S</mi> <mn>0</mn> </msub> </mrow> <mrow> <mi>R</mi> <mi>L</mi> </mrow> </msubsup> </semantics> </math> (<b>a</b>), <math display="inline"> <semantics> <msubsup> <mi>R</mi> <mrow> <msub> <mi>S</mi> <mn>0</mn> </msub> <msub> <mi>A</mi> <mn>0</mn> </msub> </mrow> <mrow> <mi>R</mi> <mi>L</mi> </mrow> </msubsup> </semantics> </math> (<b>b</b>) and <math display="inline"> <semantics> <msubsup> <mi>T</mi> <mrow> <msub> <mi>S</mi> <mn>0</mn> </msub> <msub> <mi>A</mi> <mn>0</mn> </msub> </mrow> <mrow> <mi>R</mi> <mi>L</mi> </mrow> </msubsup> </semantics> </math> (<b>c</b>) for cases C and F; <math display="inline"> <semantics> <mrow> <mi>δ</mi> <mo>=</mo> <mn>0.07</mn> </mrow> </semantics> </math>.</p> Full article ">
6595 KiB  
Article
Synthesis of Bioactive Chlorogenic Acid-Silica Hybrid Materials via the Sol–Gel Route and Evaluation of Their Biocompatibility
by Michelina Catauro and Severina Pacifico
Materials 2017, 10(7), 840; https://doi.org/10.3390/ma10070840 - 21 Jul 2017
Cited by 24 | Viewed by 4435
Abstract
Natural phenol compounds are gaining a great deal of attention because of their potential use as prophylactic and therapeutic agents in many diseases, as well as in applied science for their preventing role in oxidation deterioration. With the aim to synthetize new phenol-based [...] Read more.
Natural phenol compounds are gaining a great deal of attention because of their potential use as prophylactic and therapeutic agents in many diseases, as well as in applied science for their preventing role in oxidation deterioration. With the aim to synthetize new phenol-based materials, the sol–gel method was used to embed different content of the phenolic antioxidant chlorogenic acid (CGA) within silica matrices to obtain organic-inorganic hybrid materials. Fourier transform infrared (FTIR) measurements were used to characterize the prepared materials. The new materials were screened for their bioactivity and antioxidant potential. To this latter purpose, direct DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azinobis-(3-ethylbenzothiazolin-6-sulfonic acid) methods were applied: radical scavenging capability appeared strongly dependent on the phenol amount in investigated hybrids, and became pronounced, mainly toward the ABTS radical cation, when materials with CGA content equal to 15 wt% and 20 wt% were analyzed. The in vitro biocompatibility of the synthetized materials was estimated by using the MTT assay towards fibroblast NIH 3T3 cells, human keratinocyte HaCaT cells, and the neuroblastoma SH-SY5Y cell line. As cell viability and morphology of tested cell lines seemed to be unaffected by new materials, the attenuated total reflectance (ATR)-FTIR method was applied to deeply measure the effects of the hybrids in the three different cell lines. Full article
(This article belongs to the Special Issue Sol-Gel Chemistry Applied to Materials Science)
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<p>Chemical structure of chlorogenic acid (CGA).</p> Full article ">Figure 2
<p>FT-IR spectra of (<b>a</b>) pure SiO<sub>2</sub>; (<b>b</b>) SiO<sub>2</sub>/CGA, 5 wt%; (<b>c</b>) SiO<sub>2</sub>/CGA, 10 wt%; (<b>d</b>) SiO<sub>2</sub>/CGA, 15 wt%; (<b>e</b>) SiO<sub>2</sub>/CGA, 20 wt%; and (<b>f</b>) pure CGA.</p> Full article ">Figure 3
<p>UV-VIS spectra of (<b>a</b>) pure SiO<sub>2</sub>; (<b>b</b>) pure CGA; (<b>c</b>) SiO<sub>2</sub>/CGA hybrids. Panel (<b>d</b>) shows different UV-VIS spectra obtained by importing the acquired data into Excel and subtracting SiO<sub>2</sub> signals from the SiO<sub>2</sub> scan to those of each hybrid.</p> Full article ">Figure 4
<p>FT-IR spectra of (<b>a</b>) pure SiO<sub>2</sub>; (<b>b</b>) SiO<sub>2</sub>/CGA, 5 wt%; (<b>c</b>) SiO<sub>2</sub>/CGA, 10 wt%; (<b>d</b>) SiO<sub>2</sub>/CGA, 15 wt%; and (<b>e</b>) SiO<sub>2</sub>/CGA, 20 wt% after 21 days of exposure to SBF.</p> Full article ">Figure 5
<p>SEM micrographs of (<b>a</b>) pure SiO<sub>2</sub> and (<b>b</b>) a representative SiO<sub>2</sub>/CGA hybrid; and (<b>c</b>) EDX analysis.</p> Full article ">Figure 6
<p>Radical Scavenging Capacity (RSC, %) of different amounts of SiO<sub>2</sub>-CGA hybrids, and SiO<sub>2</sub> samples towards (<b>a</b>) ABTS<sup>•+</sup> and (<b>b</b>) DPPH<sup>•</sup>. Values, reported as percentage vs. a blank, are the mean ± SD of measurements carried out on three samples (<span class="html-italic">n</span> = 3) analyzed three times.</p> Full article ">Figure 7
<p>Morphological changes in hybrids- and SiO<sub>2</sub>-treated NIH-3T3 cells. Representative images were acquired by an inverted phase contrast brightfield Zeiss Primo Vert Microscope. Ctrl = untreated cells.</p> Full article ">Figure 8
<p>Cell Viability (CV, %) of (<b>a</b>) NIH-3T3, (<b>b</b>) HaCaT, and (<b>c</b>) SH-SY5Y cells treated with <span style="color:#A6A6A6">■</span> 1.0 mg, and <span style="color:#595959">■</span> 2.0 mg of SiO<sub>2</sub>-CGA hybrids, after 48 h exposure time by means of MTT test results. Values, reported as percentage vs. an untreated control, are the mean ± SD of measurements carried out on three samples (<span class="html-italic">n</span> = 3) analyzed six times.</p> Full article ">Figure 9
<p>Representative ATR-FTIR spectra of cell suspensions (<b>a</b>) untreated or previously treated with (<b>b</b>) pure SiO<sub>2</sub>; (<b>c</b>) SiO<sub>2</sub>/CGA, 5 wt%; and (<b>d</b>) SiO<sub>2</sub>/CGA, 15 wt%.</p> Full article ">Figure 10
<p>Flowchart of the sol–gel process used to synthesize the SiO<sub>2</sub>-CGA hybrids.</p> Full article ">
21827 KiB  
Article
The Microstructural Characterization of Multiferroic LaFeO3-YMnO3 Multilayers Grown on (001)- and (111)-SrTiO3 Substrates by Transmission Electron Microscopy
by Bin Pang, Lei Sun, Xuan Shen, Yang-Yang Lv, Xiao Li, Fei-Xiang Wu, Shu-Hua Yao, Jian Zhou, Shan-Tao Zhang and Y.B. Chen
Materials 2017, 10(7), 839; https://doi.org/10.3390/ma10070839 - 21 Jul 2017
Cited by 3 | Viewed by 4692
Abstract
The microstructure of multiferroic LaFeO3-YMnO3 (LFO-YMO) multilayers grown on (001)- and (111)-SrTiO3 substrates is characterized by the transmission electron microscopy (TEM). Detailed TEM characterization reveals that LFO-YMO multilayers grown on both substrates have clear layer-by-layer morphology and distinct chemical-composition [...] Read more.
The microstructure of multiferroic LaFeO3-YMnO3 (LFO-YMO) multilayers grown on (001)- and (111)-SrTiO3 substrates is characterized by the transmission electron microscopy (TEM). Detailed TEM characterization reveals that LFO-YMO multilayers grown on both substrates have clear layer-by-layer morphology and distinct chemical-composition layered structure. The most notable feature is that LFO-YMO multilayers grown on (001)-SrTiO3 substrate have three types of domains, while those on (111)-SrTiO3 have only one. The multi-/twin- domain structure can be qualitatively explained by the lattice mismatch in this system. The details of the domain structure of LFO-YMO multilayers are crucial to understanding their magnetic properties. Full article
(This article belongs to the Special Issue Physics, Measurements and Applications of Multiferroic and Magnetoelectric Materials)
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<p>(<b>a</b>) The low-magnification transmission electron microscopy (TEM) of LFO-YMO (sample-I) multilayers grown on (001)-SrTiO<sub>3</sub> (STO) substrate; (<b>b</b>) The selected-area-electron-diffraction (SAED) pattern of sample-I. The three weak spots coming from multi-domain structure are highlighted by white arrows. The directions of c-axis in three types of domains of YMO are indicated, as well. The SAED pattern of sample-I are the overlap of four electron diffraction patterns: α-, β-, γ-domain of YMO and [001]-zone axis of LFO. The elongation at the high-order reflections is attributed to splitting of corresponding diffractions; (<b>c</b>) is the schematic of three type of crystallographic domain between YMO and LFO in α-, β-, and γ-type of domain configurations; (<b>d</b>) is the schematic of SAED pattern of α-, β-, and γ-type of domain configurations. Large violet circles represent the basic reflections of the three types of domains. Small blue, red, and black circles represent the weak reflections coming from α-, β-, and γ-type of domain, respectively; (<b>e</b>) The low-magnification high-angle-annular-dark-field (HAADF) image of sample-I. The inset is the high-magnification HAADF image.</p> Full article ">Figure 2
<p>(<b>a</b>) HAADF image and (<b>b</b>–<b>d</b>) are the element mapping images of Fe, Mn, and La of sample-I, respectively.</p> Full article ">Figure 2 Cont.
<p>(<b>a</b>) HAADF image and (<b>b</b>–<b>d</b>) are the element mapping images of Fe, Mn, and La of sample-I, respectively.</p> Full article ">Figure 3
<p>(<b>a</b>,<b>b</b>) are two typical High-resolution TEM (HRTEM) images of sample-I show that there are multi-domain structures in YMO layers. Three digital Fast Fourier Transformation (FFT) images are depicted in these pictures, as well. The areas used to take FFT images are highlighted by white squares. Obviously, overlapping of three FFT images forms the same pattern as that shown in <a href="#materials-10-00839-f001" class="html-fig">Figure 1</a>b.</p> Full article ">Figure 4
<p>(<b>a</b>) The low-magnification TEM image of sample-II; (<b>b</b>) The HAADF image of sample-II; (<b>c</b>) The SAED pattern of LFO-YMO multilayers. The weak reflection spots coming from three-type domain are highlighted by white arrows.</p> Full article ">Figure 5
<p>HRTEM image of sample-II shows the two-type domain structure. Left and right insets are the digital Fast Fourier Transformation images of their respective micrograph. The <span class="html-italic">c</span>-axis of different domains is indicated by the white arrows.</p> Full article ">Figure 6
<p>(<b>a</b>) The low-magnification TEM image of sample-III grown on (111)-STO substrate; (<b>b</b>) is the SAED pattern of sample-III with electron beam aligned along [11<math display="inline"> <semantics> <mover accent="true"> <mn>2</mn> <mo>¯</mo> </mover> </semantics> </math>]-STO direction; (c) is the schematic of SAED pattern of <a href="#materials-10-00839-f006" class="html-fig">Figure 6</a>b. Black circles are the reflections observed in the experiment. Blue triangles (highlighted by black arrows) are the extra reflections if there are three types of domains.</p> Full article ">Figure 7
<p>(<b>a</b>) Low-magnification HAADF image of sample-III; (<b>b</b>–<b>d</b>) are the element mapping images of La, Fe, and Mn in sample-III.</p> Full article ">Figure 8
<p>HRTEM image of sample-III. This image was taken with electron beam aligned along the [11-2]-STO zone axis.</p> Full article ">Figure 9
<p>(<b>a</b>) A typical HRTEM image of sample-III; (<b>b</b>–<b>d</b>) are pure strain e<sub>xx</sub> and e<sub>yy</sub>, as well as torsional strain e<sub>xy</sub> (e<sub>xx</sub> and e<sub>yy</sub> are pure strain along the <span class="html-italic">x</span> and <span class="html-italic">y</span> axes, while e<sub>xy</sub> is a torsional strain) that are extracted from geometric phase analysis, respectively.</p> Full article ">Figure 10
<p>(<b>a</b>,<b>b</b>) are atomic structures of YMO and LFO, respectively. One can see the greater distortion of oxygen octahedra in YMO with respect to LFO.</p> Full article ">
3039 KiB  
Article
Influences of Thermal Treatment on the Dielectric Performances of Polystyrene Composites Reinforced by Graphene Nanoplatelets
by Benhui Fan, Yu Liu, Delong He and Jinbo Bai
Materials 2017, 10(7), 838; https://doi.org/10.3390/ma10070838 - 21 Jul 2017
Cited by 11 | Viewed by 4069
Abstract
Dielectric properties of composites near percolation threshold (fc) are often sensitive to thermal treatments, and the annealing temperature is usually associated with a polymer’s rheological properties. In this study, the influences of the thermal treatment on dielectric properties are investigated [...] Read more.
Dielectric properties of composites near percolation threshold (fc) are often sensitive to thermal treatments, and the annealing temperature is usually associated with a polymer’s rheological properties. In this study, the influences of the thermal treatment on dielectric properties are investigated for the polystyrene (PS) matrix composite reinforced by graphene nanoplatelets (GNP) fillers near fc. It can be found that the thermal treatment can not only increase the dielectric constant, but also decrease the dielectric loss for the PS/GNP composite. This interesting phenomenon possibly happens in the interfacial region of PS/GNP with the thickness about 4–6 nm according to the electron energy-loss spectroscopy (EELS) results. The free volumes around the interface can be easily altered by the movement of polymeric segments after annealing at the glass transition temperature. Full article
(This article belongs to the Special Issue Polymers for Film Capacitors)
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<p>The process of preparing samples by micro-compounder.</p> Full article ">Figure 2
<p>(<b>a</b>) SEM image and (<b>b</b>) Raman spectrum for G5 powder.</p> Full article ">Figure 3
<p>Frequency dependence of dielectric properties for polystyrene/graphene nanoplatelets (PS/G5) composites with different filler volume fractions: (<b>a</b>) dielectric loss; (<b>b</b>) dielectric constant; and (<b>c</b>) the best linear fits for ε’ at 100 Hz for PS/G5 composites with different volume fractions by the percolation theory shown in Equation (1).</p> Full article ">Figure 4
<p>(<b>a</b>) The fracture image by scanning transmission electron microscopy (STEM) for PS/G5-9%; (<b>b</b>) Higher magnification for the red area in (<b>a</b>); (<b>c</b>) The energy loss spectra of C-K edges for three points which stand for three regions in the orange line of (<b>b</b>); (<b>d</b>) Peak positions extracted from electron energy-loss spectroscopy (EELS) acquired from image (<b>b</b>), shown as a function of the acquisition order from point 1 to point 250.</p> Full article ">Figure 5
<p>ε’ and tan θ of the dynamic mechanical analysis (DMA) measurement for PS/G5-9% from 25 °C to 150 °C at 1 Hz.</p> Full article ">Figure 6
<p>Frequency dependence of dielectric properties for PS/G5 composites series after the thermal treatment: (<b>a</b>) for tan δ and (<b>b</b>) for ε’; (<b>c</b>,<b>d</b>) are the differences (∆) of the values of tan δ and ε’ between before and after the thermal treatment at five frequencies, respectively.</p> Full article ">
6805 KiB  
Article
Effects of Annealing Conditions on Mixed Lead Halide Perovskite Solar Cells and Their Thermal Stability Investigation
by Haifeng Yang, Jincheng Zhang, Chunfu Zhang, Jingjing Chang, Zhenhua Lin, Dazheng Chen, He Xi and Yue Hao
Materials 2017, 10(7), 837; https://doi.org/10.3390/ma10070837 - 21 Jul 2017
Cited by 32 | Viewed by 6460
Abstract
In this work, efficient mixed organic cation and mixed halide (MA0.7FA0.3Pb(I0.9Br0.1)3) perovskite solar cells are demonstrated by optimizing annealing conditions. AFM, XRD and PL measurements show that there is a better perovskite film [...] Read more.
In this work, efficient mixed organic cation and mixed halide (MA0.7FA0.3Pb(I0.9Br0.1)3) perovskite solar cells are demonstrated by optimizing annealing conditions. AFM, XRD and PL measurements show that there is a better perovskite film quality for the annealing condition at 100 °C for 30 min. The corresponding device exhibits an optimized PCE of 16.76% with VOC of 1.02 V, JSC of 21.55 mA/cm2 and FF of 76.27%. More importantly, the mixed lead halide perovskite MA0.7FA0.3Pb(I0.9Br0.1)3 can significantly increase the thermal stability of perovskite film. After being heated at 80 °C for 24 h, the PCE of the MA0.7FA0.3Pb(I0.9Br0.1)3 device still remains at 70.00% of its initial value, which is much better than the control MAPbI3 device, where only 46.50% of its initial value could be preserved. We also successfully fabricated high-performance flexible mixed lead halide perovskite solar cells based on PEN substrates. Full article
(This article belongs to the Section Energy Materials)
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<p>Device structure of p-i-n MA<sub>0.7</sub>FA<sub>0.3</sub>Pb(I<sub>0.9</sub>Br<sub>0.1</sub>)<sub>3</sub> PSCs.</p> Full article ">Figure 2
<p>XRD patterns of MA<sub>0.7</sub>FA<sub>0.3</sub>Pb(I<sub>0.9</sub>Br<sub>0.1</sub>)<sub>3</sub> perovskite films on glass/ITO substrates annealed at 100 °C for 10, 20, 30 or 40 min.</p> Full article ">Figure 3
<p>SEM and AFM topography images of MA<sub>0.7</sub>FA<sub>0.3</sub>Pb(I<sub>0.9</sub>Br<sub>0.1</sub>)<sub>3</sub> perovskite films annealed at 100 °C for 10 (<b>a</b>,<b>e</b>), 20 (<b>b</b>,<b>f</b>), 30 (<b>c</b>,<b>g</b>) and 40 (<b>d</b>,<b>h</b>) min. The scale bar in SEM measurements is 1 μm.</p> Full article ">Figure 4
<p>(<b>a</b>) Steady-state photoluminescence (PL) spectra for the MA<sub>0.7</sub>FA<sub>0.3</sub>Pb(I<sub>0.9</sub>Br<sub>0.1</sub>)<sub>3</sub> perovskite films on glass substrates at 100 °C for 10, 20, 30 and 40 min; (<b>b</b>) The wavelength-dependent absorbance spectra of MA<sub>0.7</sub>FA<sub>0.3</sub>Pb(I<sub>0.9</sub>Br<sub>0.1</sub>)<sub>3</sub> perovskite films on glass/ITO annealed at 100 °C for 10, 20, 30 and 40 min. The inset picture is high magnification.</p> Full article ">Figure 5
<p>(<b>a</b>) <span class="html-italic">J</span>-<span class="html-italic">V</span> characteristics of forward and reverse bias sweeps for the best-performing MA<sub>0.7</sub>FA<sub>0.3</sub>Pb(I<sub>0.9</sub>Br<sub>0.1</sub>)<sub>3</sub> PSC annealed at 100 °C for 30 min; (<b>b</b>) Steady measurement at the maximum power output point; (<b>c</b>) IPCE spectrum of the best-performing solar cell.</p> Full article ">Figure 6
<p>Thermal degradation of MA<sub>0.7</sub>FA<sub>0.3</sub>Pb(I<sub>0.9</sub>Br<sub>0.1</sub>)<sub>3</sub> and MAPbI<sub>3</sub> films on glass, when each perovskite is heated at 150 °C for the times indicated.</p> Full article ">Figure 7
<p>(<b>a</b>) The wavelength-dependent absorbance spectra of MAPbI<sub>3</sub> films; (<b>b</b>) MA<sub>0.7</sub>FA<sub>0.3</sub>Pb(I<sub>0.9</sub>Br<sub>0.1</sub>)<sub>3</sub> films; (<b>c</b>) XRD patterns of MAPbI<sub>3</sub> films; and (<b>d</b>) MA<sub>0.7</sub>FA<sub>0.3</sub>Pb(I<sub>0.9</sub>Br<sub>0.1</sub>)<sub>3</sub> films on glass at 150 °C for the different time scales.</p> Full article ">Figure 8
<p>(<b>a</b>) <span class="html-italic">J</span>-<span class="html-italic">V</span> characteristics of forward and reverse bias sweeps for the best-performing flexible PSCs; (<b>b</b>) Normalized PCE of flexible perovskite devices as a function of bending cycles with different radii of 8 and 5 mm. Inset is a photograph of the flexible device.</p> Full article ">
8641 KiB  
Review
Surface Plasmon Resonance or Biocompatibility—Key Properties for Determining the Applicability of Noble Metal Nanoparticles
by Ana Maria Craciun, Monica Focsan, Klara Magyari, Adriana Vulpoi and Zsolt Pap
Materials 2017, 10(7), 836; https://doi.org/10.3390/ma10070836 - 21 Jul 2017
Cited by 35 | Viewed by 7843
Abstract
Metal and in particular noble metal nanoparticles represent a very special class of materials which can be applied as prepared or as composite materials. In most of the cases, two main properties are exploited in a vast number of publications: biocompatibility and surface [...] Read more.
Metal and in particular noble metal nanoparticles represent a very special class of materials which can be applied as prepared or as composite materials. In most of the cases, two main properties are exploited in a vast number of publications: biocompatibility and surface plasmon resonance (SPR). For instance, these two important properties are exploitable in plasmonic diagnostics, bioactive glasses/glass ceramics and catalysis. The most frequently applied noble metal nanoparticle that is universally applicable in all the previously mentioned research areas is gold, although in the case of bioactive glasses/glass ceramics, silver and copper nanoparticles are more frequently applied. The composite partners/supports/matrix/scaffolds for these nanoparticles can vary depending on the chosen application (biopolymers, semiconductor-based composites: TiO2, WO3, Bi2WO6, biomaterials: SiO2 or P2O5-based glasses and glass ceramics, polymers: polyvinyl alcohol (PVA), Gelatin, polyethylene glycol (PEG), polylactic acid (PLA), etc.). The scientific works on these materials’ applicability and the development of new approaches will be targeted in the present review, focusing in several cases on the functioning mechanism and on the role of the noble metal. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>A</b>) Schematic illustration presenting the covalent functionalization of the fabricated plasmonic biosensor with anti-alpha-fetoprotein (AFP) for label-free and one-step localized surface plasmon resonance (LSPR) detection of AFP; (<b>B</b>) Representative SEM image of the fabricated plasmonic substrate; (<b>C</b>) Normalized reflectance spectra of the plasmonic biosensor before (a) and after (b–d) exposure to human serum sample three times. (Reproduced with permission from Reference [<a href="#B17-materials-10-00836" class="html-bibr">17</a>] published by Elsevier).</p> Full article ">Figure 2
<p>(<b>A</b>) Surface textures of the origin of butterfly wings covered with an Au layer of 40–70 nm thickness; (<b>B</b>) Schematic illustration representing the functionalization steps involved in the fabrication of butterfly wings for carcinoembryonic antigen (CEA) detection; (<b>C</b>) Surface enhanced Raman spectroscopy (SERS)-based CEA detection for five different clinical samples. (Reproduced with permission from Reference [<a href="#B36-materials-10-00836" class="html-bibr">36</a>] published by the Royal Society of Chemistry).</p> Full article ">Figure 3
<p>(<b>A</b>) Schematic illustration of the single-step colorimetric detection assay applied for the early detection of H3N2 influenza A virus (IAV) using Au nanoparticles (AuNPs); An obvious color change from red to purple and alteration of extinction spectrum is observed with the increase of H3N2 concentration; (<b>B</b>) Variance of absorption ratio of A700/A525 as a function of H3N2 concentration. (Reproduced with permission from Reference [<a href="#B53-materials-10-00836" class="html-bibr">53</a>] published by the Royal Society of Chemistry).</p> Full article ">Figure 4
<p>(<b>A</b>) Schematic representation of the synthesis of monoclonal anti-tau antibody-conjugated AuNPs and interaction with tau protein; (<b>B</b>) TEM image of anti-tau antibody-conjugated AuNPs after the addition of 20 ng∙mL<sup>−1</sup> tau protein; (<b>C</b>) Extinction spectrum of monoclonal anti-tau antibody conjugated AuNPs in the presence of bovine serum albumin (BSA) and tau protein (200 ng∙mL<sup>−1</sup>); (<b>D</b>) Plot illustrating the linear correlation between two-photon Rayleigh scattering (TPRS) intensity and concentration of tau protein over the range of 5–350 ng∙mL<sup>−1</sup>. (Reprinted with permission from Reference [<a href="#B58-materials-10-00836" class="html-bibr">58</a>] Copyright (2009) American Chemical Society).</p> Full article ">Figure 5
<p>(<b>A</b>) Illustration of single-step SERS immunoassay based on plasmonic coupling enhancement via sandwich assembly; (<b>B</b>) SERS spectra obtained in response to different combinations of proteins targets; (<b>C</b>) SERS response for immunoassay of recombinant human interferon gamma (INFγ) protein with varying concentration; (<b>D</b>) The peak intensity at 1335 cm<sup>−1</sup> as a function of INFγ concentration. (Reprinted with permission from Reference [<a href="#B73-materials-10-00836" class="html-bibr">73</a>] Copyright (2013) published by American Chemical Society).</p> Full article ">Figure 6
<p>Bioluminescent signals from <span class="html-italic">Escherichia coli</span> and <span class="html-italic">Staphylococcus epidermidis</span> in response to the presence of polymer/bioactive glass and polymer/bioactive glass with Ag<sub>2</sub>O composites. (Reproduced with permission from Reference [<a href="#B114-materials-10-00836" class="html-bibr">114</a>] published by Sage).</p> Full article ">Figure 7
<p>UV-vis spectra of the 60SiO<sub>2</sub>(32−x)CaO·8P<sub>2</sub>O<sub>5</sub>∙xAg<sub>2</sub>O samples.</p> Full article ">Figure 8
<p>TEM micrographs of sample 60SiO<sub>2</sub>∙31.85CaO∙8P<sub>2</sub>O<sub>5</sub>∙0.15Au<sub>2</sub>O (mol%). (Reproduced with permission from Reference [<a href="#B117-materials-10-00836" class="html-bibr">117</a>] published by Elsevier).</p> Full article ">Figure 9
<p>The increasing trend of Au applicability in photocatalysis (Web of Knowledge, <a href="https://apps.webofknowledge.com" target="_blank">https://apps.webofknowledge.com</a>, access date: 22 May 2017).</p> Full article ">Figure 10
<p>The charge transfer mechanism (<b>left</b>) of the quaternary composite formed from ZnS/CdS/graphene shells and Au; the degradation of phenol (<b>right</b>) in the presence of the quaternary composite (Reproduced with permission from Reference [<a href="#B150-materials-10-00836" class="html-bibr">150</a>] published by the Royal Society of Chemistry).</p> Full article ">Figure 11
<p>The enhanced activity of Cu/Au—TiO<sub>2</sub> NPs in photocatalytic hydrogen production (<b>left</b>); the high-resolution transmission electron microscopy (HR-TEM) micrograph of the used composite material (<b>right</b>). (Reproduced with permission from Reference [<a href="#B152-materials-10-00836" class="html-bibr">152</a>] published by Springer).</p> Full article ">Figure 12
<p>The application of Au in Z-scheme photocatalysts for photocatalytic hydrogen production (<b>left</b>) (Reproduced with permission from Reference [<a href="#B157-materials-10-00836" class="html-bibr">157</a>] published by the Royal Society of Chemistry) and CO<sub>2</sub> photoreduction (<b>right</b>) (Reproduced with permission from Reference [<a href="#B158-materials-10-00836" class="html-bibr">158</a>] published by Elsevier).</p> Full article ">Figure 13
<p>The role of CuS, TiO<sub>2</sub> and Au in ternary composites in the degradation of oxytetracycline(OTC) (<b>left</b>) (Reproduced with permission from Reference [<a href="#B161-materials-10-00836" class="html-bibr">161</a>] published by American Chemical Society) and the photocatalytic performance of CuO-Au composites in the photodegradation of rhodamine-B (<b>right</b>) (Reproduced with permission from Reference [<a href="#B162-materials-10-00836" class="html-bibr">162</a>] published by American Chemical Society).</p> Full article ">Figure 14
<p>The photocurrent response of Bi<sub>2</sub>MoO<sub>6</sub> and the composite materials (S1–S3) (Reproduced with permission from Reference [<a href="#B165-materials-10-00836" class="html-bibr">165</a>] published by Elsevier).</p> Full article ">Figure 15
<p>(<b>a</b>) TEM micrographs of Bi<sub>2</sub>WO<sub>6</sub>nanosheets; (<b>b</b>) HRTEM micrograph of Bi<sub>2</sub>WO<sub>6</sub> nanosheets. Inset: Fourier transformed electron diffraction pattern of Bi<sub>2</sub>WO<sub>6</sub>; (<b>c</b>) TEM and (<b>d</b>) HRTEM micrographs of Au nanorods (AuNRs); (<b>e</b>) TEM and (<b>f</b>) HRTEM micrographs of Au NR/Bi<sub>2</sub>WO<sub>6</sub> heterostructures. (Reproduced with permission from Reference [<a href="#B166-materials-10-00836" class="html-bibr">166</a>] published by John Wiley and Sons).</p> Full article ">Figure 16
<p>The mechanism of H<sub>2</sub>O<sub>2</sub> generation (<b>left</b>) (Reprinted with permission from Reference [<a href="#B167-materials-10-00836" class="html-bibr">167</a>] Copyright (2016) published by American Chemical Society) and the enhanced electron transfer mechanism, when shape-tailored BiVO<sub>4</sub> was applied (<b>right</b>) (Reproduced with permission from Reference [<a href="#B168-materials-10-00836" class="html-bibr">168</a>] published by Elsevier).</p> Full article ">Figure 17
<p>TEM micrographs of Au/Cu<sub>2</sub>FeSnS<sub>4</sub> core/shell NPs (Reprinted with permission from Reference [<a href="#B173-materials-10-00836" class="html-bibr">173</a>] Copyright (2015) published by the American Chemical Society).</p> Full article ">Figure 18
<p>Schematic illustration of the possible mechanism of the UV enhancement involving the processes of (1) virtually generating green luminescence (GL) at Cu dopant, (2) transferring energy from the virtual GL of Cu-doped ZnO to localized surface plasmon resonance (LSPR) of Au NPs, (3) exciting LSPR of Au upon receiving the transferred energy from the virtual GL, and generating plasmonic hot electrons as a result of nonradiative decay of the LSPR, (4) transferring hot electrons from Au to the conduction band of Cu-doped ZnO, and (5) excitons radiative recombination at Cu-doped ZnO into UV emission (Reproduced with permission from Reference [<a href="#B176-materials-10-00836" class="html-bibr">176</a>] published by John Wiley and Sons).</p> Full article ">Figure 19
<p>Hierarchical ZnO nanostructures (<b>a</b>,<b>b</b>) with AuNPs (<b>c</b>,<b>e</b>,<b>f</b>) used in the degradation of rhodamine-B (<b>d</b>) (Reproduced with permission from Reference [<a href="#B180-materials-10-00836" class="html-bibr">180</a>] published by Elsevier).</p> Full article ">Figure 20
<p>A schematic illustration of the photocatalysis mechanisms under (<b>A</b>) UV; (<b>B</b>) visible; and (<b>C</b>) NIR irradiation, respectively.(Reproduced with permission from Reference [<a href="#B185-materials-10-00836" class="html-bibr">185</a>] published by John Wiley and Sons).</p> Full article ">
26171 KiB  
Article
Investigation of the Quasi-Brittle Failure of Alashan Granite Viewed from Laboratory Experiments and Grain-Based Discrete Element Modeling
by Jian Zhou, Luqing Zhang, Duoxing Yang, Anika Braun and Zhenhua Han
Materials 2017, 10(7), 835; https://doi.org/10.3390/ma10070835 - 21 Jul 2017
Cited by 47 | Viewed by 6518
Abstract
Granite is a typical crystalline material, often used as a building material, but also a candidate host rock for the repository of high-level radioactive waste. The petrographic texture—including mineral constituents, grain shape, size, and distribution—controls the fracture initiation, propagation, and coalescence within granitic [...] Read more.
Granite is a typical crystalline material, often used as a building material, but also a candidate host rock for the repository of high-level radioactive waste. The petrographic texture—including mineral constituents, grain shape, size, and distribution—controls the fracture initiation, propagation, and coalescence within granitic rocks. In this paper, experimental laboratory tests and numerical simulations of a grain-based approach in two-dimensional Particle Flow Code (PFC2D) were conducted on the mechanical strength and failure behavior of Alashan granite, in which the grain-like structure of granitic rock was considered. The microparameters for simulating Alashan granite were calibrated based on real laboratory strength values and strain-stress curves. The unconfined uniaxial compressive test and Brazilian indirect tensile test were performed using a grain-based approach to examine and discuss the influence of mineral grain size and distribution on the strength and patterns of microcracks in granitic rocks. The results show it is possible to reproduce the uniaxial compressive strength (UCS) and uniaxial tensile strength (UTS) of Alashan granite using the grain-based approach in PFC2D, and the average mineral size has a positive relationship with the UCS and UTS. During the modeling, most of the generated microcracks were tensile cracks. Moreover, the ratio of the different types of generated microcracks is related to the average grain size. When the average grain size in numerical models is increased, the ratio of the number of intragrain tensile cracks to the number of intergrain tensile cracks increases, and the UCS of rock samples also increases with this ratio. However, the variation in grain size distribution does not have a significant influence on the likelihood of generated microcracks. Full article
(This article belongs to the Special Issue The Brittle Failure of Different Materials)
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<p>The location of the Alashan area and a photo of rock cores deeply drilled for test specimens.</p> Full article ">Figure 2
<p>Two cross-polarized light photos of thin sections showing the mineralogical composition of test specimens. (<b>a</b>) Section I; (<b>b</b>) Section II.</p> Full article ">Figure 3
<p>MTS 815 servo-controlled hydraulic testing machine for the laboratory tests.</p> Full article ">Figure 4
<p>The curves of axial stress versus deformation of different specimens under UCS and UTS testing. (<b>a</b>) The stress–strain curves under UCS testing; (<b>b</b>) The curves of axial stress versus axial deformation under UTS testing.</p> Full article ">Figure 5
<p>The failure characteristics of the rock specimens under both UCS and UTS testing. (<b>a</b>) NRG-1-541.3; (<b>b</b>) NRG-1-541.4; (<b>c</b>) NRG-1-541.5; (<b>d</b>) NRG-541-1; (<b>e</b>) NRG-541-2; (<b>f</b>) NRG-541-3.</p> Full article ">Figure 5 Cont.
<p>The failure characteristics of the rock specimens under both UCS and UTS testing. (<b>a</b>) NRG-1-541.3; (<b>b</b>) NRG-1-541.4; (<b>c</b>) NRG-1-541.5; (<b>d</b>) NRG-541-1; (<b>e</b>) NRG-541-2; (<b>f</b>) NRG-541-3.</p> Full article ">Figure 6
<p>Bonded particle model in PFC2D: (<b>a</b>) Schematic of bonded particle model; (<b>b</b>) the micro-scale parameters of the bond at contacts; and (<b>c</b>) the deformation and failure mechanisms of the bond under tensile and shear stress (modified from Bahaaddini et al. [<a href="#B48-materials-10-00835" class="html-bibr">48</a>]).</p> Full article ">Figure 6 Cont.
<p>Bonded particle model in PFC2D: (<b>a</b>) Schematic of bonded particle model; (<b>b</b>) the micro-scale parameters of the bond at contacts; and (<b>c</b>) the deformation and failure mechanisms of the bond under tensile and shear stress (modified from Bahaaddini et al. [<a href="#B48-materials-10-00835" class="html-bibr">48</a>]).</p> Full article ">Figure 7
<p>Steps in the generation of a grain-based model based on the initial particle seeds in PFC5.0 (<b>a</b>–<b>f</b>). (<b>a</b>) Initial particle packing; (<b>b</b>) Development of polygons; (<b>c</b>) Polygonal grain structure; (<b>d</b>) Different grain types; (<b>e</b>) Particles in mineral grians bonded by parallel bond; (<b>f</b>) Grain boundaries mimiced by smooth joint model (red).</p> Full article ">Figure 7 Cont.
<p>Steps in the generation of a grain-based model based on the initial particle seeds in PFC5.0 (<b>a</b>–<b>f</b>). (<b>a</b>) Initial particle packing; (<b>b</b>) Development of polygons; (<b>c</b>) Polygonal grain structure; (<b>d</b>) Different grain types; (<b>e</b>) Particles in mineral grians bonded by parallel bond; (<b>f</b>) Grain boundaries mimiced by smooth joint model (red).</p> Full article ">Figure 8
<p>Smooth joint model [<a href="#B49-materials-10-00835" class="html-bibr">49</a>]: (<b>a</b>) Sketches of smooth joint model; (<b>b</b>) force-displacement relationship at smooth joint contacts: (i) normal force versus normal displacement; (ii) shear force versus shear displacement; and (iii) normal displacement versus shear displacement in the sliding process.</p> Full article ">Figure 9
<p>Microscale parameter calibration for Alasha granite by modeling of UCS and UTS tests. (<b>a</b>) The stress–strain curves under UCS testing; (<b>b</b>) The curves of axial stress vs. axial deformation under UTS testing.</p> Full article ">Figure 10
<p>Mineral distributions and microcrack distributions in rock models after UCS and UTS tests under the loading rate of 0.01 m/s. a, b, c are the indexes of samples, respectively. (<b>a</b>) Microcracks distribution after UCS test; (<b>b</b>) Microcracks distribution after UTS test.</p> Full article ">Figure 11
<p>Cumulative distributions of the size of mineral grains in the five models and the corresponding mineral structures. (<b>a</b>) Cumulative distributions of the size of mineral grains in the five models; (<b>b</b>) Mineral structures in five different models.</p> Full article ">Figure 12
<p>UCS, UTS, and the ratio of UCS to UTS varying with average grain size, respectively. (<b>a</b>) UCS varying with average grain size; (<b>b</b>) The UTS varying with average grain size; (<b>c</b>) The ratio of UCS to UTS varying with average grain size.</p> Full article ">Figure 12 Cont.
<p>UCS, UTS, and the ratio of UCS to UTS varying with average grain size, respectively. (<b>a</b>) UCS varying with average grain size; (<b>b</b>) The UTS varying with average grain size; (<b>c</b>) The ratio of UCS to UTS varying with average grain size.</p> Full article ">Figure 13
<p>Mineral distributions and microcrack distributions in five representative rock models after UCS and UTS tests. (<b>a</b>) Micro-cracks distribution after UTS tests; (<b>b</b>) Micro-cracks distribution after UCS tests.</p> Full article ">Figure 13 Cont.
<p>Mineral distributions and microcrack distributions in five representative rock models after UCS and UTS tests. (<b>a</b>) Micro-cracks distribution after UTS tests; (<b>b</b>) Micro-cracks distribution after UCS tests.</p> Full article ">Figure 14
<p>The rose diagrams of the inclination angle of different type microcracks in the corresponding models in <a href="#materials-10-00835-f013" class="html-fig">Figure 13</a>b. (<b>a</b>) The rose diagram of inclination angle of intergrain tensile microcracks; (<b>b</b>) The rose diagram of inclination angle of intergrain shear microcracks; (<b>c</b>) The rose diagram of inclination angle of intragrain tensile microcracks.</p> Full article ">
2920 KiB  
Article
Improvement of Cr-Co-Mo Membrane Surface Used as Barrier for Bone Regeneration through UV Photofunctionalization: An In Vitro Study
by Oscar Decco, Jésica Zuchuat and Nicolás Farkas
Materials 2017, 10(7), 825; https://doi.org/10.3390/ma10070825 - 21 Jul 2017
Cited by 9 | Viewed by 3994
Abstract
Although there are several studies of the ultraviolet (UV) light-mediated photofunctionalization of titanium for use as implant material, the underlying mechanism is not fully understood. However, the results of in vitro and in vivo studies are very encouraging. The use of UV photofunctionalization [...] Read more.
Although there are several studies of the ultraviolet (UV) light-mediated photofunctionalization of titanium for use as implant material, the underlying mechanism is not fully understood. However, the results of in vitro and in vivo studies are very encouraging. The use of UV photofunctionalization as a surface treatment on other implant materials, as the Cr-Co-Mo alloy, has not been explored in depth. Using sandblasted Cr-Co-Mo discs, the surface photofunctionalization was studied for ultraviolet A (UVA, 365 nm) and ultraviolet C (UVC, 254 nm), and the surfaces were evaluated for their ability to sustain hydroxyapatite crystal growth through incubation in simulated body fluid for a seven-day period. The variation of the pre- and post-irradiation contact angle and surface composition was determined through the quantification of the weight percentage of Ca and P crystals by the EDAX ZAF method (EDS). Statistically significant differences (p < 0.05) were found for samples irradiated with UVA over 48 h, corresponding with hydrophilic surfaces, and the same result was found for samples exposed to 3 h of UVC. Superhydrophilic surfaces were found in samples irradiated for 12, 24 and 48 h with UVC. The decrease in the carbon content is related with the increase in the surface content of Ca and P, and vice versa over the Cr-Co-Mo surfaces. Full article
(This article belongs to the Section Biomaterials)
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<p>Contact angle variation of UVA irradiation. There were no statistically significant differences for the first four irradiation times studied. * For 48 h of UVA irradiation statistically significant difference (<span class="html-italic">p</span> &lt; 0.05) was observed.</p> Full article ">Figure 2
<p>(<b>A</b>) Contact angle variation of UVC irradiation. There were no statistically significant differences for 15 min of irradiation. After 3 h, statistically significant differences were observed: * (<span class="html-italic">p</span> &lt; 0.05), and from 12 h, superhydrophilic surfaces were found; (<b>B</b>) The control (upper) and the 48 h discs (lower) after UVC irradiation.</p> Full article ">Figure 3
<p>Microanalysis of surfaces irradiated. (<b>A</b>,<b>C</b>) Carbon content (UVA and UVC, respectively); (<b>B</b>,<b>D</b>) Ca and P content (UVA and UVC, respectively). High-resolution figure.</p> Full article ">Figure 4
<p>Micrograph and Energy Dispersive Spectroscopy (EDS) spectra of samples of Cr-Co-Mo alloy irradiated with UV light during 3 h, incubated in Revised Simulated Body Fluid (R-SBF) for seven days. (<b>A</b>) UVA-treated; (<b>B</b>) UVC-treated.</p> Full article ">Figure 5
<p>Mapping of surface Ca (<b>A</b>) and P (<b>B</b>) distribution to the 3 h UVA-irradiated samples, and superficial Ca (<b>C</b>) and P (<b>D</b>) to its homologous sample, UVC-irradiated.</p> Full article ">Figure 6
<p>(<b>A</b>) Setup for image capture; (<b>B</b>) Image used for measurement.</p> Full article ">Figure 7
<p>Characterization of contact angle.</p> Full article ">
2669 KiB  
Article
Biological Degradation of Chinese Fir with Trametes Versicolor (L.) Lloyd
by Meiling Chen, Chuangui Wang, Benhua Fei, Xinxin Ma, Bo Zhang, Shuangyan Zhang and Anmin Huang
Materials 2017, 10(7), 834; https://doi.org/10.3390/ma10070834 - 20 Jul 2017
Cited by 18 | Viewed by 4509
Abstract
Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) has been an important afforestation species in northeast China. It has obvious defects of buckling and cracking easily, which are caused by its chemical components. Trametes versicolor (L.) Lloyd, a white-rot fungus, can decompose the cellulose, [...] Read more.
Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) has been an important afforestation species in northeast China. It has obvious defects of buckling and cracking easily, which are caused by its chemical components. Trametes versicolor (L.) Lloyd, a white-rot fungus, can decompose the cellulose, hemicellulose, and lignin in the wood. White-rot fungus was used to biologically degrade Chinese fir wood. The effects of different degradation time on the Chinese fir wood’s mechanical properties, micromorphology, chemical components, and crystallinity were studied. The results showed that the heartwood of Chinese fir was more durable than the sapwood and the durability class of Chinese fir was III. Trametes versicolor (L.) Lloyd had a greater influence on the mechanical properties (especially with respect to the modulus of elasticity (MOE)) for the sapwood. Trametes versicolor (L.) Lloyd degraded Chinese fir and colonized the lumen of various wood cell types in Chinese fir, penetrated cell walls via pits, caused erosion troughs and bore holes, and removed all cell layers. The ability of white-rot fungus to change the chemical composition mass fraction for Chinese fir was: hemicellulose > lignin > cellulose. The durability of the chemical compositions was: lignin > cellulose > hemicellulose. The crystallinity of the cellulose decreased and the mean size of the ordered (crystalline) domains increased after being treated by white-rot fungus. Full article
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<p>Mass loss of samples after degradation. The continuous and discontinuous lines in the figure caption indicates sapwood and heartwood. The error bar is according to a confidence interval of 95%.</p> Full article ">Figure 2
<p>Changes of (<b>a</b>) modulus of rupture (MOR) and (<b>b</b>) modulus of elongation (MOE) before and after degradation. The continuous and discontinuous lines in the figure caption indicates sapwood and heartwood. The error bar is according to a confidence interval of 95%.</p> Full article ">Figure 3
<p>(<b>a</b>) Untreated wood samples; (<b>b</b>) Hyphae spread in the wood cells; (<b>c</b>) Hyphae spread by penetrating pit; (<b>d</b>) The cell wall became thinner after degradation, the arrow shows the area becoming thinner; (<b>e</b>) Treated wood samples; (<b>f</b>) The treated tracheid; (<b>g</b>) The change of tracheid before and after degradation. The surface of untreated tracheid (left) was smooth and the end of it was spinous. The end of the tracheid and the middle of treated tracheid (right) surface became rough.</p> Full article ">Figure 3 Cont.
<p>(<b>a</b>) Untreated wood samples; (<b>b</b>) Hyphae spread in the wood cells; (<b>c</b>) Hyphae spread by penetrating pit; (<b>d</b>) The cell wall became thinner after degradation, the arrow shows the area becoming thinner; (<b>e</b>) Treated wood samples; (<b>f</b>) The treated tracheid; (<b>g</b>) The change of tracheid before and after degradation. The surface of untreated tracheid (left) was smooth and the end of it was spinous. The end of the tracheid and the middle of treated tracheid (right) surface became rough.</p> Full article ">Figure 4
<p>Changes of chemical compositions mass fraction after degradation. (<b>a</b>) Changes of holocellulose mass fraction; (<b>b</b>) Changes of cellulose mass fraction; (<b>c</b>) Changes of hemicellulose mass fraction; (<b>d</b>) Changes of acid-insoluble lignin mass fraction; (<b>e</b>) Changes of extractives mass fraction. The continuous and discontinuous lines in the figure caption indicates sapwood and heartwood. The error bar is according to a confidence interval of 95%.</p> Full article ">Figure 5
<p>Changes of (<b>a</b>) cellulose crystallinity and (<b>b</b>) crystalline mean size before and after degradation. The continuous and discontinuous lines in the figure caption indicates sapwood and heartwood. The error bar is according to a confidence interval of 95%.</p> Full article ">Figure 6
<p>(<b>a</b>) Fungal pure cultures were held on the potato dextrose agar; (<b>b</b>) Wood samples and sampling areas; (<b>c</b>) Treated sample preparation.</p> Full article ">
13243 KiB  
Article
Effect of the Ultrasonic Surface Rolling Process on the Fretting Fatigue Behavior of Ti-6Al-4V Alloy
by Chengsong Liu, Daoxin Liu, Xiaohua Zhang, Shouming Yu and Weidong Zhao
Materials 2017, 10(7), 833; https://doi.org/10.3390/ma10070833 - 20 Jul 2017
Cited by 67 | Viewed by 6085
Abstract
The effect of the ultrasonic surface rolling process (USRP) on the rotary bending fretting fatigue (FF) of Ti-6Al-4V alloy was investigated. The reason for the USRP’s ability to improve the FF resistance of Ti-6Al-4V alloy was studied. The results revealed that the USRP [...] Read more.
The effect of the ultrasonic surface rolling process (USRP) on the rotary bending fretting fatigue (FF) of Ti-6Al-4V alloy was investigated. The reason for the USRP’s ability to improve the FF resistance of Ti-6Al-4V alloy was studied. The results revealed that the USRP induced a compressive residual stress field with a depth of 530 μm and a maximum residual stress of −930 MPa. Moreover, the surface micro-hardness of the USRP sample was significantly higher than that of the untreated base material (BM) sample, and the USRP yielded a 72.7% increase in the FF limit of the alloy. These further enhanced fatigue properties contributed mainly to the compressive residual stress field with large numerical value and deep distribution, which could effectively suppress FF crack initiation and early propagation. The USRP-induced surface work-hardening had only a minor impact on the FF resistance. Full article
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<p>The microstructure of the annealed-state Ti-6Al-4V alloy.</p> Full article ">Figure 2
<p>Schematic illustrations of the FF test apparatus (<b>a</b>) Principle of the rotary bending FF test; (<b>b</b>) shape and dimensions of the proving ring.</p> Full article ">Figure 3
<p>Schematic illustration of USRP set-up.</p> Full article ">Figure 4
<p>The cross-sectional microstructure of the USRP sample.</p> Full article ">Figure 5
<p>Cross-sectional EBSD map of Ti-6Al-4V alloy treated by the USRP (<b>a</b>); and corresponding grain diameter distribution (<b>b</b>,<b>c</b>) and misorientation angle distribution (<b>d</b>,<b>e</b>): Ι zone—the near surface; ΙΙ zone—the sub-surface.</p> Full article ">Figure 5 Cont.
<p>Cross-sectional EBSD map of Ti-6Al-4V alloy treated by the USRP (<b>a</b>); and corresponding grain diameter distribution (<b>b</b>,<b>c</b>) and misorientation angle distribution (<b>d</b>,<b>e</b>): Ι zone—the near surface; ΙΙ zone—the sub-surface.</p> Full article ">Figure 6
<p>The results of micro-hardness distribution along the cross-section of samples with different treatments.</p> Full article ">Figure 7
<p>The results of axial residual stress distribution along the cross-section of samples with different treatments.</p> Full article ">Figure 8
<p>Stress/life (S-N) curves for BM, USRP + A and USRP samples.</p> Full article ">Figure 9
<p>Fretting fatigue lives of Ti-6Al-4V alloy with different surface treatments at a maximum stress level of 500 MPa (H-surface work-hardening, σ<sub>r</sub>-compressive residual stress).</p> Full article ">Figure 10
<p>Morphologies of the fretting contact zones and the fracture surfaces of BM and USRP samples: (<b>a</b>,<b>b</b>) BM sample; (<b>c</b>,<b>d</b>) USRP sample (maximum stress level σ<sub>max</sub> = 500 MPa).</p> Full article ">Figure 10 Cont.
<p>Morphologies of the fretting contact zones and the fracture surfaces of BM and USRP samples: (<b>a</b>,<b>b</b>) BM sample; (<b>c</b>,<b>d</b>) USRP sample (maximum stress level σ<sub>max</sub> = 500 MPa).</p> Full article ">
18947 KiB  
Article
An Advanced Multi-Sensor Acousto-Ultrasonic Structural Health Monitoring System: Development and Aerospace Demonstration
by Joel Smithard, Nik Rajic, Stephen Van der Velden, Patrick Norman, Cedric Rosalie, Steve Galea, Hanfei Mei, Bin Lin and Victor Giurgiutiu
Materials 2017, 10(7), 832; https://doi.org/10.3390/ma10070832 - 20 Jul 2017
Cited by 27 | Viewed by 5589
Abstract
A key longstanding objective of the Structural Health Monitoring (SHM) research community is to enable the embedment of SHM systems in high value assets like aircraft to provide on-demand damage detection and evaluation. As against traditional non-destructive inspection hardware, embedded SHM systems must [...] Read more.
A key longstanding objective of the Structural Health Monitoring (SHM) research community is to enable the embedment of SHM systems in high value assets like aircraft to provide on-demand damage detection and evaluation. As against traditional non-destructive inspection hardware, embedded SHM systems must be compact, lightweight, low-power and sufficiently robust to survive exposure to severe in-flight operating conditions. Typical Commercial-Off-The-Shelf (COTS) systems can be bulky, costly and are often inflexible in their configuration and/or scalability, which militates against in-service deployment. Advances in electronics have resulted in ever smaller, cheaper and more reliable components that facilitate the development of compact and robust embedded SHM systems, including for Acousto-Ultrasonics (AU), a guided plate-wave inspection modality that has attracted strong interest due mainly to its capacity to furnish wide-area diagnostic coverage with a relatively low sensor density. This article provides a detailed description of the development, testing and demonstration of a new AU interrogation system called the Acousto Ultrasonic Structural health monitoring Array Module+ (AUSAM+). This system provides independent actuation and sensing on four Piezoelectric Wafer Active Sensor (PWAS) elements with further sensing on four Positive Intrinsic Negative (PIN) photodiodes for intensity-based interrogation of Fiber Bragg Gratings (FBG). The paper details the development of a novel piezoelectric excitation amplifier, which, in conjunction with flexible acquisition-system architecture, seamlessly provides electromechanical impedance spectroscopy for PWAS diagnostics over the full instrument bandwidth of 50 KHz–5 MHz. The AUSAM+ functionality is accessed via a simple hardware object providing a myriad of custom software interfaces that can be adapted to suit the specific requirements of each individual application. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)
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<p>Acousto Ultrasonic Structural health monitoring Array Module<sup>+</sup> (AUSAM<sup>+</sup>) system: (<b>a</b>) Inputs and Outputs; (<b>b</b>) Size comparison to an iPhone 6.</p> Full article ">Figure 2
<p>AUSAM<sup>+</sup> simplified block diagram.</p> Full article ">Figure 3
<p>Industrial Fiber Communication Ring for channel expansion and scalability. Up to 62 AUSAM<sup>+</sup> can exist on the Industrial Fiber Communications Ring (IFCR).</p> Full article ">Figure 4
<p>AUSAM<sup>+</sup> simplified Analogue Front End (AFE) channel architecture, where the four available channels are referenced A through D. The Drive Voltage Monitoring on/off switch and 1 MΩ divider resistor only exists on channel A and channel D while the Buffer Current Amplifiers, of which there are only two, have their outputs connected to channel B and channel C only.</p> Full article ">Figure 5
<p>AUSAM<sup>+</sup> simplified High Voltage Drive Amplifier (HVDA) (not all swich elements shown).</p> Full article ">Figure 6
<p>Solatron 1260 measurement of the Variable Gain Amplifier (VGA) input impedance when the AFE channel is configured to monitor PWAS excitation voltage in Drive Monitor mode. The impedance between TP1 and ground is<math display="inline"> <semantics> <mrow> <mo> </mo> <msub> <mi mathvariant="normal">Z</mi> <mrow> <mi mathvariant="normal">T</mi> <mo>−</mo> <mi>voltage</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>ω</mi> <mo>)</mo> </mrow> </mrow> </semantics> </math>. The impedance between TP2, which is located at the AFE channels summing junction, and circuit ground, is the VGA input impedance<math display="inline"> <semantics> <mrow> <mo> </mo> <msub> <mi>Z</mi> <mrow> <mi mathvariant="normal">I</mi> <mo>−</mo> <mi>voltage</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>ω</mi> <mo>)</mo> </mrow> </mrow> </semantics> </math>.</p> Full article ">Figure 7
<p>Solatron 1260 measurement of the transfer functions (TF) as the measured Piezoelectric Wafer Active Sensor (PWAS) excitation voltage signal propagates through the remaining AFE channel when configured in Drive Monitor mode. TP1 is located at the AFE channels summing junction while TP2 and TP3 comprise the differential signal<math display="inline"> <semantics> <mrow> <mo> </mo> <msub> <mi>V</mi> <mrow> <mi>A</mi> <mi>D</mi> <mi>C</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>ω</mi> <mo>)</mo> </mrow> </mrow> </semantics> </math> subsequently digitized by the high-speed Analog to Digital Converter (ADC).</p> Full article ">Figure 8
<p>Solatron 1260 measurement of the TF as the measured PWAS excitation current signal propagates through the AFE channel when configured in Drive Monitor mode. TP1 correlates to the input of the current amplifier while TP2 and TP3 comprise the differential signal<math display="inline"> <semantics> <mrow> <mo> </mo> <msub> <mi>V</mi> <mrow> <mi>A</mi> <mi>D</mi> <mi>C</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>ω</mi> <mo>)</mo> </mrow> </mrow> </semantics> </math> subsequently digitized by the high-speed ADC.</p> Full article ">Figure 9
<p>AUSAM<sup>+</sup> hardware object hierarchy and contents.</p> Full article ">Figure 10
<p>Example Graphical User Interface (GUI) created to explore the AUSAM<sup>+</sup> capability.</p> Full article ">Figure 11
<p>Typical variation in maximum excitation peak voltage with various excitation frequencies applied over a precision 1 nF capacitor.</p> Full article ">Figure 12
<p>(<b>a</b>) Percentage of channel D excitation cross-talk on other channels; (<b>b</b>) Typical single-shot (no synchronous averaging) Root Mean Square (RMS) noise floor performance.</p> Full article ">Figure 13
<p>Acquisition system comparison to a LeCroy oscilloscope in both Drive Monitor mode and pitch-catch regime; (<b>a</b>) 1.2 MHz 100 Vpeak excitation signal applied to a 1 nF capacitor; (<b>b</b>) The PSD of the AU response of a PWAS on an aluminum panel, in a pitch-catch regime, when excited at 500 kHz.</p> Full article ">Figure 14
<p>Comparison of the EM impedance magnitude sweep over the AUSAM<sup>+</sup> bandwidth for un-bonded 6.3 mm and 10 mm diameter PWAS elements.</p> Full article ">Figure 15
<p>Schematic of experimental setup showing rectangular PWAS grid arrangement.</p> Full article ">Figure 16
<p>Image of the experimental setup.</p> Full article ">Figure 17
<p>Typical signal acquired using the AUSAM<sup>+</sup> (PWAS 8).</p> Full article ">Figure 18
<p>Signal band-pass filtered between 200 kHz and 400 kHz.</p> Full article ">Figure 19
<p>Raw signals from PWAS 1–10.</p> Full article ">Figure 20
<p>Filtered signals from PWAS 1–10.</p> Full article ">Figure 21
<p>Signal envelopes of PWAS 1–10.</p> Full article ">Figure 22
<p>Correlation between radial distance and time of flight.</p> Full article ">Figure 23
<p>The unfiltered pulse-echo signal on PWAS 11.</p> Full article ">Figure 24
<p>The filtered signal on PWAS 11.</p> Full article ">Figure 25
<p>(<b>a</b>) An aluminum panel with 40 mm long full-depth extended notch located 140 mm from the source PWAS and perpendicular to the center line; (<b>b</b>) Photograph of the Beeswax well around the source PWAS to contain acetone solution used to induce damage of the bond layer.</p> Full article ">Figure 26
<p>Hilbert transform envelops of the response PWAS and Fiber Bragg Gratings (FBG) showing the average and two standard deviations (shaded) for each stage in the experiment. (<b>a</b>) 150 kHz excitation; (<b>b</b>) 550 kHz excitation.</p> Full article ">Figure 26 Cont.
<p>Hilbert transform envelops of the response PWAS and Fiber Bragg Gratings (FBG) showing the average and two standard deviations (shaded) for each stage in the experiment. (<b>a</b>) 150 kHz excitation; (<b>b</b>) 550 kHz excitation.</p> Full article ">Figure 27
<p>(<b>a</b>) PWAS S<sub>0</sub> mode amplitudes normalized as a percentage of the baseline average peak over frequencies and experimental stages; (<b>b</b>) FBG S<sub>0</sub> mode amplitudes normalized as a percentage of the baseline average peak over frequencies and experimental stages.</p> Full article ">Figure 27 Cont.
<p>(<b>a</b>) PWAS S<sub>0</sub> mode amplitudes normalized as a percentage of the baseline average peak over frequencies and experimental stages; (<b>b</b>) FBG S<sub>0</sub> mode amplitudes normalized as a percentage of the baseline average peak over frequencies and experimental stages.</p> Full article ">Figure 28
<p>(<b>a</b>) PWAS A<sub>0</sub> mode amplitudes normalized as a percentage of the baseline average peak over frequencies and experimental stages; (<b>b</b>) FBG A<sub>0</sub> mode amplitudes normalized as a percentage of the baseline average peak over frequencies and experimental stages.</p> Full article ">Figure 28 Cont.
<p>(<b>a</b>) PWAS A<sub>0</sub> mode amplitudes normalized as a percentage of the baseline average peak over frequencies and experimental stages; (<b>b</b>) FBG A<sub>0</sub> mode amplitudes normalized as a percentage of the baseline average peak over frequencies and experimental stages.</p> Full article ">Figure 29
<p>(<b>a</b>) Pulse-echo signal peak bordered by dashed lines corresponds to a reflection from the notch for each stage in the experiment with two standard deviations (shaded); (<b>b</b>) The same reflection Pulse-echo signal peak amplitudes normalized as a percentage of the baseline average peak over frequencies and experimental stages.</p> Full article ">Figure 29 Cont.
<p>(<b>a</b>) Pulse-echo signal peak bordered by dashed lines corresponds to a reflection from the notch for each stage in the experiment with two standard deviations (shaded); (<b>b</b>) The same reflection Pulse-echo signal peak amplitudes normalized as a percentage of the baseline average peak over frequencies and experimental stages.</p> Full article ">Figure 30
<p>(<b>a</b>) Successive pitch-catch responses from dark (purple) to light (orange) at 150 kHz showing a gradual attenuation as the source element bond-line was damaged by acetone; (<b>b</b>) Successive impedance magnitude plots from dark (purple) to light (orange) showing an increase in capacitance at the lateral resonance peak indicating de-bonding of the source element.</p> Full article ">Figure 30 Cont.
<p>(<b>a</b>) Successive pitch-catch responses from dark (purple) to light (orange) at 150 kHz showing a gradual attenuation as the source element bond-line was damaged by acetone; (<b>b</b>) Successive impedance magnitude plots from dark (purple) to light (orange) showing an increase in capacitance at the lateral resonance peak indicating de-bonding of the source element.</p> Full article ">Figure 31
<p>Test coupon representing key structural elements of F-111C lower wing skin at Forward Auxiliary Spar Station (FASS) 281.28. Marked is the location of the Fuel Transfer Groove (FTG).</p> Full article ">Figure 32
<p>(<b>a</b>) The FASS coupon test set up showing two PWAS elements installed on the outside of the wing skin; (<b>b</b>) The notch milled into the FTG location after establishing a baseline to simulate where a crack typically forms under operational loading. Shaded marks show the location of PWAS elements bonded on the opposite side.</p> Full article ">Figure 33
<p>Effect of the notch on the pitch-catch response at 1.25 MHz with the first incident wave-packet bordered by dashed lines. The barely perceptible shading confirms very good repeatability.</p> Full article ">Figure 34
<p>Variation in attenuation expressed as a percentage of the baseline calculated using a Riemann sum of the signal envelope for the first wave-packet over the experimental frequency range. Error bars represent two standard deviations over ten consecutive sweeps.</p> Full article ">Figure 35
<p>Composite test set-up. (<b>a</b>) Interrogating the impacted coupon; (<b>b</b>) coupon cross-sectional view showing the location of two embedded PWAS elements in relation to the impact site.</p> Full article ">Figure 36
<p>Waveforms for pitch-catch interrogation in both directions; top plots show excitation on PWAS channel A and bottom plot shows excitation on PWAS channel B. The Hilbert transform envelopes are displayed and any shading represents two standard deviations in variability over 10 consecutive sweeps: (<b>a</b>) 250 KHz; (<b>b</b>) 300 KHz; (<b>c</b>) 350 KHz; (<b>d</b>) 400 KHz.</p> Full article ">Figure 36 Cont.
<p>Waveforms for pitch-catch interrogation in both directions; top plots show excitation on PWAS channel A and bottom plot shows excitation on PWAS channel B. The Hilbert transform envelopes are displayed and any shading represents two standard deviations in variability over 10 consecutive sweeps: (<b>a</b>) 250 KHz; (<b>b</b>) 300 KHz; (<b>c</b>) 350 KHz; (<b>d</b>) 400 KHz.</p> Full article ">Figure 37
<p>Attenuation due to coupon damage as a normalized percentage of the baseline calculated using a Riemann sum of the signal envelope in the time window 40–150 μs. Error bars represent two standard deviations showing the variability over ten consecutive sweeps.</p> Full article ">Figure 38
<p>AUSAM<sup>+</sup> strapped on-board a SJ900 Hexacopter during flight testing.</p> Full article ">
16056 KiB  
Article
Evaluation of 3D-Printed Polycaprolactone Scaffolds Coated with Freeze-Dried Platelet-Rich Plasma for Bone Regeneration
by Junda Li, Meilin Chen, Xiaoying Wei, Yishan Hao and Jinming Wang
Materials 2017, 10(7), 831; https://doi.org/10.3390/ma10070831 - 19 Jul 2017
Cited by 80 | Viewed by 8569
Abstract
Three-dimensional printing is one of the most promising techniques for the manufacturing of scaffolds for bone tissue engineering. However, a pure scaffold is limited by its biological properties. Platelet-rich plasma (PRP) has been shown to have the potential to improve the osteogenic effect. [...] Read more.
Three-dimensional printing is one of the most promising techniques for the manufacturing of scaffolds for bone tissue engineering. However, a pure scaffold is limited by its biological properties. Platelet-rich plasma (PRP) has been shown to have the potential to improve the osteogenic effect. In this study, we improved the biological properties of scaffolds by coating 3D-printed polycaprolactone (PCL) scaffolds with freeze-dried and traditionally prepared PRP, and we evaluated these scaffolds through in vitro and in vivo experiments. In vitro, we evaluated the interaction between dental pulp stem cells (DPSCs) and the scaffolds by measuring cell proliferation, alkaline phosphatase (ALP) activity, and osteogenic differentiation. The results showed that freeze-dried PRP significantly enhanced ALP activity and the mRNA expression levels of osteogenic genes (ALP, RUNX2 (runt-related gene-2), OCN (osteocalcin), OPN (osteopontin)) of DPSCs (p < 0.05). In vivo, 5 mm calvarial defects were created, and the PRP-PCL scaffolds were implanted. The data showed that compared with traditional PRP-PCL scaffolds or bare PCL scaffolds, the freeze-dried PRP-PCL scaffolds induced significantly greater bone formation (p < 0.05). All these data suggest that coating 3D-printed PCL scaffolds with freeze-dried PRP can promote greater osteogenic differentiation of DPSCs and induce more bone formation, which may have great potential in future clinical applications. Full article
(This article belongs to the Section Biomaterials)
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<p>An overview of the in vivo bone regeneration of the calvarial defects.</p> Full article ">Figure 2
<p>Characterization of 3D-printed polycaprolactone (PCL) scaffolds before (<b>a</b>,<b>c</b>,<b>e</b>) and after (<b>b</b>,<b>d</b>,<b>f</b>) treatment with ethanolic sodium hydroxide. At a higher magnification, we can see the roughness and micro-size pores (<b>d</b>,<b>f</b>). The magnification levels were ×100 (<b>a</b>,<b>b</b>), ×500 (<b>c</b>,<b>d</b>) and ×30,000 (<b>e</b>,<b>f</b>).</p> Full article ">Figure 3
<p>Scanning electron microscope (SEM) microphotographs of freeze-dried platelet-rich plasma polycaprolactone (PRP-PCL) scaffolds (<b>a</b>,<b>d</b>,<b>g</b>), traditional PRP-PCL scaffolds (<b>b</b>,<b>e</b>,<b>h</b>), and bare PCL scaffolds (<b>c</b>,<b>f</b>,<b>i</b>) at ×200, ×800, and ×3000 magnification. PRP could be seen after coating with freeze-dried PRP-PCL scaffolds (<b>a</b>,<b>d</b>,<b>g</b>) or traditional PRP-PCL scaffolds (<b>b</b>,<b>e</b>,<b>h</b>). Randomly distributed PRP are visible around the surface of the scaffolds, while no PRP are visible on the bare PCL scaffolds (<b>c</b>,<b>f</b>,<b>i</b>).</p> Full article ">Figure 4
<p>Cell attachment on the freeze-dried PRP-PCL scaffolds (<b>a</b>–<b>c</b>); traditional PRP-PCL scaffolds (<b>d</b>–<b>f</b>); bare PCL scaffolds (<b>g</b>–<b>i</b>) after three days of seeding; all images shown at ×50 magnification (* <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01) and (<b>j</b>) The number of the cell attachment.</p> Full article ">Figure 5
<p>Number of migrated cells in the (<b>a</b>) freeze-dried PRP-PCL scaffold group; (<b>b</b>) traditional PRP-PCL scaffold group; (<b>c</b>) bare PCL scaffold group after 12 h of seeding; all images shown at ×50 magnification (** <span class="html-italic">p</span> &lt; 0.01) and (<b>d</b>) The number of the cell migration.</p> Full article ">Figure 6
<p>(<b>a</b>) Cell proliferation on the freeze-dried PRP-PCL scaffolds, traditional PRP-PCL scaffolds and bare PCL scaffolds 1, 3, 5, and 7 days after seeding; (<b>b</b>) ALP activity of the freeze-dried PRP-PCL scaffolds, traditional PRP-PCL scaffolds and bare PCL scaffolds seven and 14 days after seeding (* <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01).</p> Full article ">Figure 7
<p>Expression of bone-specific genes, RUNX2, ALP, OPN, and OCN on the freeze-dried PRP-PCL scaffold, traditional PRP-PCL scaffold and bare PCL scaffold (* <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01).</p> Full article ">Figure 8
<p>Evaluation of bone formation in calvarial defects via micro-CT. Representative micro-CT images of calvarial defects showing mineralized bone formation after treatment with freeze-dried PRP-PCL scaffolds (<b>a</b>,<b>d</b>,<b>g</b>,<b>j</b>), traditional PRP-PCL scaffolds (<b>b</b>,<b>e,h</b>,<b>k</b>) and bare PCL scaffolds (<b>c</b>,<b>f</b>,<b>i</b>,<b>l</b>). The bone tissue in the circle represents the regenerated bone. (<b>m</b>) Regenerated bone formation rate at 2, 4, 8 and 12 weeks after scaffold implantation (* <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01).</p> Full article ">Figure 9
<p>Histological sections stained with H&amp;E showing calvarial defects treated with freeze-dried PRP-PCL scaffold (<b>a1</b>–<b>c1</b>,<b>a2</b>–<b>c2</b>,<b>a3</b>–<b>c3</b>), traditional PRP-PCL scaffold (<b>d1</b>–<b>f1</b>,<b>d2</b>–<b>f2</b>,<b>d3</b>–<b>f3</b>) and bare PCL scaffold (<b>g1</b>–<b>i1</b>,<b>g2</b>–<b>i2</b>,<b>g3</b>–<b>i3</b>) at 4, 8, and 12 weeks after implantation. The bone-like tissues between the dashed lines are newly formed bone. Empty circles are the scaffold locations. (<b>j</b>) New bone formation rate at 4, 8, and 12 weeks after scaffold implantation (* <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01).</p> Full article ">
12199 KiB  
Article
Sliding Wear Behavior of UNS R56400 Titanium Alloy Samples Thermally Oxidized by Laser
by Juan Manuel Vazquez Martinez, Francisco J. Botana Pedemonte, Marta Botana Galvin, Jorge Salguero Gomez and Mariano Marcos Barcena
Materials 2017, 10(7), 830; https://doi.org/10.3390/ma10070830 - 19 Jul 2017
Cited by 16 | Viewed by 4431
Abstract
Wear of elements subjected to friction and sliding is among the main causes of low tribological performance and short lifetime of strategic materials such as titanium alloys. These types of alloys are widely used in different areas such as aerospace and the biomechanics [...] Read more.
Wear of elements subjected to friction and sliding is among the main causes of low tribological performance and short lifetime of strategic materials such as titanium alloys. These types of alloys are widely used in different areas such as aerospace and the biomechanics industry. In this sense, surface modification treatments allow for the overcoming of limitations and improvement of features and properties. In the case of titanium alloys, improvements in the main weaknesses of these materials can be obtained. Laser texturing of UNS R56400 (Ti6Al4V) alloy, according to Unified Numbering System designation, surface layers in a non-protective atmosphere produces an increase of the oxides, especially of titanium dioxide (TiO2) species. The presence of oxides in the alloy results in color tonality variations as well as hardness increases. In addition, specific roughness topographies may be produced by the track of laser beam irradiation. In this research, thermochemical oxidation of UNS R56400 alloy has been developed through laser texturing, using scan speed of the beam (Vs) as the process control variable, and its influence on the sliding wear behavior was analyzed. For this purpose, using pin on disc tribological tests, wear was evaluated from the friction coefficient, and wear mechanisms involved in the process were analyzed. Combined studies of wear mechanisms and the friction coefficient verified that by means of specific surface treatments, an increase in the wear resistance of this type of alloys is generated. The most advantageous results for the improvement of tribological behavior have been detected in textured surfaces using a Vs of 150 mm/s, resulting in a decrease in the friction coefficient values by approximately 20%. Full article
(This article belongs to the Special Issue Tribological Behavior of Materials by Surface Engineering)
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<p>Layout and effects of laser texturing over Ti6Al4V samples.</p> Full article ">Figure 2
<p>Surface tonality variations as a function of laser textured parameters.</p> Full article ">Figure 3
<p>(<b>a</b>) Correlation between roughness parameters [<a href="#B33-materials-10-00830" class="html-bibr">33</a>] and scan speed of the laser beam; (<b>b</b>) Roughness (Rpk) as a function of scan speed (Vs).</p> Full article ">Figure 3 Cont.
<p>(<b>a</b>) Correlation between roughness parameters [<a href="#B33-materials-10-00830" class="html-bibr">33</a>] and scan speed of the laser beam; (<b>b</b>) Roughness (Rpk) as a function of scan speed (Vs).</p> Full article ">Figure 4
<p>Roughness (Rpk) evolution as a function of scan speed (Vs) at different pulse rates (F).</p> Full article ">Figure 5
<p>Surface microgeometry evolution (<b>a</b>) F = 50 kHz-Vs = 10 mm/s; (<b>b</b>) F = 50 kHz-Vs = 250 mm/s.</p> Full article ">Figure 6
<p>Oxygen presence of areas near textured grooves.</p> Full article ">Figure 7
<p>(<b>a</b>) Hardness gradient on textured groove; (<b>b</b>) Hardness (HV) as a function of scan speed (Vs).</p> Full article ">Figure 8
<p>Friction coefficient for several surface treatments as a function of sliding distance.</p> Full article ">Figure 9
<p>Wear mechanisms and friction coefficient behavior at the first stage of sliding distance.</p> Full article ">Figure 10
<p>Wear mechanisms and friction coefficient behavior at the second stage of sliding distance.</p> Full article ">Figure 11
<p>Wear mechanisms and friction coefficient behavior at the last stage of sliding distance.</p> Full article ">
3563 KiB  
Article
Synthesis and Properties of Carbon Nanotube-Grafted Silica Nanoarchitecture-Reinforced Poly(Lactic Acid)
by Yao-Wen Hsu, Chia-Ching Wu, Song-Mao Wu and Chean-Cheng Su
Materials 2017, 10(7), 829; https://doi.org/10.3390/ma10070829 - 19 Jul 2017
Cited by 28 | Viewed by 5299
Abstract
A novel nanoarchitecture-reinforced poly(lactic acid) (PLA) nanocomposite was prepared using multi-walled carbon nanotube (MWCNT)-grafted silica nanohybrids as reinforcements. MWCNT-grafted silica nanohybrids were synthesized by the generation of silica nanoparticles on the MWCNT surface through the sol-gel technique. This synthetic method involves organo-modified MWCNTs [...] Read more.
A novel nanoarchitecture-reinforced poly(lactic acid) (PLA) nanocomposite was prepared using multi-walled carbon nanotube (MWCNT)-grafted silica nanohybrids as reinforcements. MWCNT-grafted silica nanohybrids were synthesized by the generation of silica nanoparticles on the MWCNT surface through the sol-gel technique. This synthetic method involves organo-modified MWCNTs that are dispersed in tetrahydrofuran, which incorporates tetraethoxysilane that undergoes an ultrasonic sol-gel process. Gelation yielded highly dispersed silica on the organo-modified MWCNTs. The structure and properties of the nanohybrids were established using 29Si nuclear magnetic resonance, Raman spectroscopy, wide-angle X-ray diffraction, thermogravimetric analysis, and transmission electron microscopy. The resulting MWCNT nanoarchitectures were covalently assembled into silica nanoparticles, which exhibited specific and controllable morphologies and were used to reinforce biodegradable PLA. The tensile strength and the heat deflection temperature (HDT) of the PLA/MWCNT-grafted silica nanocomposites increased when the MWCNT-grafted silica was applied to the PLA matrix; by contrast, the surface resistivity of the PLA/MWCNT-grafted silica nanocomposites appeared to decline as the amount of MWCNT-grafted silica in the PLA matrix increased. Overall, the reinforcement of PLA using MWCNT-grafted silica nanoarchitectures was efficient and improved its mechanical properties, heat resistance, and electrical resistivity. Full article
(This article belongs to the Special Issue Selected Material Related Papers from ICI2016)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Thermal degradation of surface-functionalized MWCNTs.</p> Full article ">Figure 2
<p>FT-IR spectra of MWCNT-grafted silica nanohybrids: (<b>a</b>) the IR region between 2000 and 4000 cm<sup>−</sup><sup>1</sup> and (<b>b</b>) the IR region between 500 and 2000 cm<sup>−1</sup>.</p> Full article ">Figure 3
<p>The solid-state <sup>29</sup>Si NMR spectra of silica and MWCNT-grafted silica nanohybrids: (<b>a</b>) neat silica; (<b>b</b>) MWCNT-COOH-silica; (<b>c</b>) MWCNT-COCl-silica; (<b>d</b>) MWCNT-NH<sub>2</sub>-silica; and (<b>e</b>) MWCNT-OH-silica.</p> Full article ">Figure 4
<p>XRD patterns of MWCNT-grafted silica nanohybrids.</p> Full article ">Figure 5
<p>Raman spectra of MWCNTs: (<b>a</b>) crude MWCNT; (<b>b</b>) carboxylic acid-modified MWCNT-grafted silica nanohybrids.</p> Full article ">Figure 6
<p>TEM images of MWCNT-grafted silica nanohybrids: (<b>a</b>) neat silica (Si(OR)<sub>n</sub>); (<b>b</b>) crude MWCNTs; (<b>c</b>) MWCNT-COOH-silica; (<b>d</b>) MWCNT-COCl-silica; (<b>e</b>) MWCNT-NH<sub>2</sub>-silica; and (<b>f</b>) MWCNT-OH-silica.</p> Full article ">Figure 7
<p>Stress–strain curves of neat poly(lactic acid) (PLA) and PLA-based nanocomposites.</p> Full article ">Figure 8
<p>TEM microphotograph of PLA/MWCNT-silica nanocomposites: (<b>a</b>) nanocomposite with a MWCNT-silica content of 0.5 wt % and (<b>b</b>) schematic depiction of the MWCNT-grafted silica in the PLA matrix.</p> Full article ">Scheme 1
<p>Synthesis of multi-walled carbon nanotube (MWCNT)-grafted silica nanohybrids.</p> Full article ">Scheme 2
<p>The mechanism of formation of carboxylic acid-modified MWCNT-grafted silica nanohybrids.</p> Full article ">
12273 KiB  
Article
Effect of Fly-Ash Cenospheres on Properties of Clay-Ceramic Syntactic Foams
by Kristine Rugele, Dirk Lehmhus, Irina Hussainova, Julite Peculevica, Marks Lisnanskis and Andrei Shishkin
Materials 2017, 10(7), 828; https://doi.org/10.3390/ma10070828 - 19 Jul 2017
Cited by 32 | Viewed by 5777
Abstract
A low-density clay ceramic syntactic foam (CSF) composite material was successfully synthesized from illitic clay added by fly ash cenospheres (CS) using the semi-dry formation method. The content of CS varied in the range of 10, 30, 50 and 60 vol %. Furthermore, [...] Read more.
A low-density clay ceramic syntactic foam (CSF) composite material was successfully synthesized from illitic clay added by fly ash cenospheres (CS) using the semi-dry formation method. The content of CS varied in the range of 10, 30, 50 and 60 vol %. Furthermore, reference samples without cenospheres were produced for property comparison. The materials comprising different amount of the additives were fired at temperatures of 600, 950, 1000, 1050, 1100, 1150 and 1200 °C. Firing times were kept constant at 30 min. Processing characteristics of the materials were evaluated in terms of density achieved and shrinkage observed as functions of both the CS content and the sintering temperature. The compressive strength and water uptake were determined as application-oriented properties. Except for the reference and the low CS level samples, the materials show an increase in strength with the increase in firing temperature, and a decrease of mechanical reliability with a decrease in density, which is typical for porous materials. Exceptions are the samples with no or low (10 vol %) content of cenospheres. In this case, the maximum strength is obtained at an intermediate sintering temperature of 1100 °C. At a low density (1.10 and 1.25 g/cm3), the highest levels of strength are obtained after sintering at 1200 °C. For nominal porosity levels of 50 and 60 vol %, 41 and 26 MPa peak stresses, respectively, are recorded under compressive load. Full article
(This article belongs to the Special Issue Syntactic Foams: Microstructural Characterisation and Effective Properties)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Appearance of samples with CS load (from left to right in each row) 0, 10, 30, 50 and 60 vol % of CS, (<b>a</b>) fired at 1000 °C, (<b>b</b>) 1050 °C, (<b>c</b>) 1100 °C, (<b>d</b>,<b>e</b>) 1200 °C—(<b>d</b>) side view and (<b>e</b>) top view.</p> Full article ">Figure 2
<p>Dependence of total shrinkage on CS content and firing temperature.</p> Full article ">Figure 3
<p>Fracture surfaces of fired samples with different CS loads, left, column showing scanning electron microscope (SEM), right, light microscopy images: (<b>a</b>,<b>b</b>) 10 vol % CS at firing temperature 1000 °C at a magnification of 150×; (<b>c</b>,<b>d</b>) 30 vol % CS at firing temperature 1100 °C at a magnification of 300×; (<b>e</b>,<b>f</b>) 50 vol % CS at firing temperature 1000 °C at a magnification of 150×.</p> Full article ">Figure 3 Cont.
<p>Fracture surfaces of fired samples with different CS loads, left, column showing scanning electron microscope (SEM), right, light microscopy images: (<b>a</b>,<b>b</b>) 10 vol % CS at firing temperature 1000 °C at a magnification of 150×; (<b>c</b>,<b>d</b>) 30 vol % CS at firing temperature 1100 °C at a magnification of 300×; (<b>e</b>,<b>f</b>) 50 vol % CS at firing temperature 1000 °C at a magnification of 150×.</p> Full article ">Figure 4
<p>LM images (magnification 500×) of ceramic syntactic foam (CSF) samples (<b>a</b>,<b>b</b>) fired at 1000 °C with (<b>a</b>) 50 and (<b>b</b>) 60 vol % of CS addition (side view), (<b>c</b>,<b>d</b>) cross section of reference samples without CS addition fired (<b>c</b>) at 1150 and (<b>d</b>) 1200 °C.</p> Full article ">Figure 4 Cont.
<p>LM images (magnification 500×) of ceramic syntactic foam (CSF) samples (<b>a</b>,<b>b</b>) fired at 1000 °C with (<b>a</b>) 50 and (<b>b</b>) 60 vol % of CS addition (side view), (<b>c</b>,<b>d</b>) cross section of reference samples without CS addition fired (<b>c</b>) at 1150 and (<b>d</b>) 1200 °C.</p> Full article ">Figure 5
<p>SEM images of CE-5 samples fracture fired at 1000 °C with 50 vol % of CS addition, (<b>a</b>) at a magnification of ×3500; (<b>b</b>) at a magnification of ×3000.</p> Full article ">Figure 6
<p>Apparent density dependence on the CS content and the firing temperature.</p> Full article ">Figure 7
<p>Dependence of water uptake on CS content and firing temperature.</p> Full article ">Figure 8
<p>Compressive strength dependence on the CS content and the firing temperature.</p> Full article ">Figure 9
<p>Dependency of compressive strength on porosity and firing temperature for material variants containing 0, 10, 30, 50 and 60 vol % of cenospheres. Arrows are meant to highlight the course of firing temperature increase for each curve.</p> Full article ">Figure 10
<p>Exemplary stress strain curves for the reference material containing no cenospheres: (<b>a</b>) maximum strength at firing temperature 1100 °C; (<b>b</b>) strength and stiffness reduction at firing temperature 1200 °C.</p> Full article ">Figure 11
<p>Exemplary stress strain curves for the syntactic foams containing 50 vol % cenospheres: (<b>a</b>) firing temperature 1100 °C; (<b>b</b>) firing temperature 1200 °C.</p> Full article ">
4075 KiB  
Article
Simulations on Monitoring and Evaluation of Plasticity-Driven Material Damage Based on Second Harmonic of S0 Mode Lamb Waves in Metallic Plates
by Xiaoqiang Sun, Xuyang Liu, Yaolu Liu, Ning Hu, Youxuan Zhao, Xiangyan Ding, Shiwei Qin, Jianyu Zhang, Jun Zhang, Feng Liu and Shaoyun Fu
Materials 2017, 10(7), 827; https://doi.org/10.3390/ma10070827 - 19 Jul 2017
Cited by 16 | Viewed by 5146
Abstract
In this study, a numerical approach—the discontinuous Meshless Local Petrov-Galerkin-Eshelby Method (MLPGEM)—was adopted to simulate and measure material plasticity in an Al 7075-T651 plate. The plate was modeled in two dimensions by assemblies of small particles that interact with each other through bonding [...] Read more.
In this study, a numerical approach—the discontinuous Meshless Local Petrov-Galerkin-Eshelby Method (MLPGEM)—was adopted to simulate and measure material plasticity in an Al 7075-T651 plate. The plate was modeled in two dimensions by assemblies of small particles that interact with each other through bonding stiffness. The material plasticity of the model loaded to produce different levels of strain is evaluated with the Lamb waves of S0 mode. A tone burst at the center frequency of 200 kHz was used as excitation. Second-order nonlinear wave was extracted from the spectrogram of a signal receiving point. Tensile-driven plastic deformation and cumulative second harmonic generation of S0 mode were observed in the simulation. Simulated measurement of the acoustic nonlinearity increased monotonically with the level of tensile-driven plastic strain captured by MLPGEM, whereas achieving this state by other numerical methods is comparatively more difficult. This result indicates that the second harmonics of S0 mode can be employed to monitor and evaluate the material or structural early-stage damage induced by plasticity. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)
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<p>Dispersion curves of Lamb waves in an aluminum plate: phase velocity.</p> Full article ">Figure 2
<p>Description of MLPGEM: (<b>a</b>) trial and test domain; (<b>b</b>) three configurations during a finite deformation.</p> Full article ">Figure 3
<p>Meshless Local Petrov-Galerkin-Eshelby Method (MLPGEM) model.</p> Full article ">Figure 4
<p>Actuating function of excitation signal with stretching length <span class="html-italic">l</span> = 30 mm and <span class="html-italic">T</span> = 0.8 ms: (<b>a</b>) time domain and (<b>b</b>) frequency domain.</p> Full article ">Figure 5
<p>Stress–strain curve of Al 7075-T651 plate with maximum strains loaded for the seven models.</p> Full article ">Figure 6
<p>(<b>a</b>) Displacement in <span class="html-italic">y</span>-axis direction at different locations through-thickness direction with the same <span class="html-italic">x</span> coordinate (=100 mm); (<b>b</b>) S<sub>0</sub> mode at 200 kHz—through thickness profiles for <span class="html-italic">y</span> displacement at <span class="html-italic">x</span> coordinate (=100 mm) for various times <span class="html-italic">t</span> = 0.02–0.07 ms.</p> Full article ">Figure 7
<p>Displacement in <span class="html-italic">x</span>-axis direction at different locations through-thickness direction with the same <span class="html-italic">x</span> coordinate (=100 mm).</p> Full article ">Figure 8
<p>Signal received at propagation distance of 300 mm for S<sub>0</sub> at 200 kHz with maximum strain 0.015 (tension 30 mm): (<b>a</b>) time domain and (<b>b</b>) frequency domain; amplitude ratio is 0.3280.</p> Full article ">Figure 9
<p>Amplitude ratio <math display="inline"> <semantics> <mrow> <msub> <mi>A</mi> <mn>2</mn> </msub> <mo>/</mo> <msubsup> <mi>A</mi> <mn>1</mn> <mn>2</mn> </msubsup> </mrow> </semantics> </math>, a measure of the nonlinearity parameter <span class="html-italic">β</span>, plotted as a function of propagation distance for the seven models (linearly fitted lines passing through the origin).</p> Full article ">Figure 10
<p>Normalized acoustic nonlinearity versus strain with the model.</p> Full article ">
4158 KiB  
Article
Synthesis and Characterization of Gelatin-Based Crosslinkers for the Fabrication of Superabsorbent Hydrogels
by Penphitcha Amonpattaratkit, Sureerat Khunmanee, Dong Hyun Kim and Hansoo Park
Materials 2017, 10(7), 826; https://doi.org/10.3390/ma10070826 - 19 Jul 2017
Cited by 29 | Viewed by 5309
Abstract
In this work, crosslinkers were prepared by conjugating high- and low-molecular-weight gelatin with different mole ratios of itaconic acid (IA) with double bonds. Then, the gelatin-itaconic acid (gelatin-IA) crosslinkers were compared with the gelatin-methacrylate (gelatin-MA) crosslinkers. The molecular weights and structures of gelatin-MA [...] Read more.
In this work, crosslinkers were prepared by conjugating high- and low-molecular-weight gelatin with different mole ratios of itaconic acid (IA) with double bonds. Then, the gelatin-itaconic acid (gelatin-IA) crosslinkers were compared with the gelatin-methacrylate (gelatin-MA) crosslinkers. The molecular weights and structures of gelatin-MA and gelatin-IA were confirmed using gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR). Additionally, the swelling ratio and biodegradation properties of the hydrogels using IA as starting monomers and gelatin-IA and gelatin-MA as crosslinkers were investigated. Both hydrogels prepared with high and low molecular weights of gelatin-IA showed higher swelling ratios than those prepared with the gelatin-MA. The results also showed that absorbent hydrogels with different biodegradabilities and swelling ratios could be prepared by changing the ratio of the gelatin-based crosslinkers. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2017)
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<p><sup>1</sup>H-NMR spectra of (<b>a</b>) High-Molecular-Weight Gelatin-MA (HGM) and (<b>b</b>) High-Molecular-Weight Gelatin-IA (HGI) crosslinkers.</p> Full article ">Figure 2
<p>Swelling ratio (<b>a</b>) and photographs (<b>b</b>) of 9 w/v % of HGM and HGI hydrogels.</p> Full article ">Figure 3
<p>Scanning electron microscopy (SEM) photograph of 9 w/v % of HGM and HGI hydrogels.</p> Full article ">Figure 4
<p>Percentage of biodegradation of 9 w/v % HGM750 and HGI750 hydrogels.</p> Full article ">Figure 5
<p><sup>1</sup>H-NMR spectra of high-molecular-weight gelatin (HG), low-molecular-weight gelatin (LG), HGI, and LGI crosslinker.</p> Full article ">Figure 6
<p>Swelling ratios (<b>a</b>) and photographs (<b>b</b>) of 9 w/v % HGI and LGI hydrogels.</p> Full article ">Figure 7
<p>SEM micrograph of 9 w/v % HGI and LGI hydrogels.</p> Full article ">Figure 8
<p>Percentage of biodegradation of 9 w/v % HGI and LGI hydrogels.</p> Full article ">
1815 KiB  
Article
First Principles Study of Adsorption of Hydrogen on Typical Alloying Elements and Inclusions in Molten 2219 Al Alloy
by Yu Liu, Yuanchun Huang, Zhengbing Xiao and Guangze Jia
Materials 2017, 10(7), 816; https://doi.org/10.3390/ma10070816 - 19 Jul 2017
Cited by 4 | Viewed by 3616
Abstract
To better understand the effect of the components of molten 2219 Al alloy on the hydrogen content dissolved in it, the H adsorption on various positions of alloying element clusters of Cu, Mn and Al, as well as the inclusion of Al2 [...] Read more.
To better understand the effect of the components of molten 2219 Al alloy on the hydrogen content dissolved in it, the H adsorption on various positions of alloying element clusters of Cu, Mn and Al, as well as the inclusion of Al2O3, MgO and Al4C3, were investigated by means of first principles calculation, and the thermodynamic stability of H adsorbed on each possible site was also studied on the basis of formation energy. Results show that the interaction between Al, MgO, Al4C3 and H atoms is mainly repulsive and energetically unfavorable; a favorable interaction between Cu, Mn, Al2O3 and H atoms was determined, with H being more likely to be adsorbed on the top of the third atomic layer of Cu(111), the second atomic layer of Mn(111), and the O atom in the third atomic layer of Al2O3, compared with other sites. It was found that alloying elements Cu and Mn and including Al2O3 may increase the hydrogen adsorption in the molten 2219 Al alloy with Al2O3 being the most sensitive component in this regard. Full article
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<p>Schematic illustration of the side structure of surface model of (<b>a</b>) Al(111), (<b>b</b>) Cu(111) and (<b>c</b>) Mn(111), along with the adsorption sites of H on (<b>d</b>) Al(111), (<b>e</b>) Cu(111) and (<b>f</b>) Mn(111).</p> Full article ">Figure 2
<p>Schematic illustration of the side structure of surface model of (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>(0001), (<b>b</b>) MgO(111) and (<b>c</b>) Al<sub>4</sub>C<sub>3</sub>(0001), along with the adsorption sites of H on (<b>d</b>) Al<sub>2</sub>O<sub>3</sub>(0001), (<b>e</b>) MgO(111) and (<b>f</b>) Al<sub>4</sub>C<sub>3</sub>(0001).</p> Full article ">Figure 3
<p>Average adsorption energy of H on Cu(111), Mn(111), Al(111), Al<sub>2</sub>O<sub>3</sub>(0001), MgO(111) and Al<sub>4</sub>C<sub>3</sub>(0001).</p> Full article ">Figure 4
<p>Formation energy of H adsorption on (<b>a</b>) Al(111), (<b>b</b>) Cu(111) and (<b>c</b>) Mn(111) as function of the relative chemical potential of H.</p> Full article ">Figure 5
<p>Formation energy of H adsorption on (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>(0001), (<b>b</b>) MgO(111) and (<b>c</b>) Al<sub>4</sub>C<sub>3</sub>(0001) as function of the relative chemical potential of H.</p> Full article ">
2240 KiB  
Article
Thermostability of Hybrid Thermoelectric Materials Consisting of Poly(Ni-ethenetetrathiolate), Polyimide and Carbon Nanotubes
by Keisuke Oshima, Shifumi Sadakata, Hitoshi Asano, Yukihide Shiraishi and Naoki Toshima
Materials 2017, 10(7), 824; https://doi.org/10.3390/ma10070824 - 18 Jul 2017
Cited by 16 | Viewed by 4960
Abstract
Three-component organic/inorganic hybrid films were fabricated by drop-casting the mixed dispersion of nanodispersed-poly(nickel 1,1,2,2-ethenetetrathiolate) (nano-PETT), polyimide (PI) and super growth carbon nanotubes (SG-CNTs) in N-methylpyrrolidone (NMP) at the designed ratio on a substrate. The dried nano-PETT/PI/SG-CNT hybrid films were prepared by the [...] Read more.
Three-component organic/inorganic hybrid films were fabricated by drop-casting the mixed dispersion of nanodispersed-poly(nickel 1,1,2,2-ethenetetrathiolate) (nano-PETT), polyimide (PI) and super growth carbon nanotubes (SG-CNTs) in N-methylpyrrolidone (NMP) at the designed ratio on a substrate. The dried nano-PETT/PI/SG-CNT hybrid films were prepared by the stepwise cleaning of NMP and methanol, and were dried once more. The thermoelectric properties of Seebeck coefficient S and electrical conductivity σ were measured by a thin-film thermoelectric measurement system ADVANCE RIKO ZEM-3M8 at 330–380 K. The electrical conductivity of nano-PETT/PI/SG-CNT hybrid films increased by 1.9 times for solvent treatment by clearing insulated of polymer. In addition, the density of nano-PETT/PI/SG-CNT hybrid films decreased 1.31 to 0.85 g·cm−3 with a decrease in thermal conductivity from 0.18 to 0.12 W·m−1·K−1. To evaluate the thermostability of nano-PETT/PI/SG-CNT hybrid films, the samples were kept at high temperature and the temporal change of thermoelectric properties was measured. The nano-PETT/PI/SG-CNT hybrid films were rather stable at 353 K and kept their power factor even after 4 weeks. Full article
(This article belongs to the Special Issue Advances in Thermoelectric Materials)
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<p>SEM images of the hybrid films of nano-PETT/PI/SG-CNT before cleaning (<b>a</b>), after methanol cleaning (<b>b</b>); after <span class="html-italic">N</span>-methylpyrrolidone (NMP) cleaning (<b>c</b>) and after the stepwise cleaning by NMP and methanol (<b>d</b>).</p> Full article ">Figure 2
<p>Seebeck coefficient (<span class="html-italic">S</span>), electrical conductivity (σ) and power factor (<span class="html-italic">PF</span>) of SG-CNT sheet, PI/SG-CNT and nano-PETT/PI/SG-CNT. Mass ratios are PI/SG-CNT = 12/8, and nano-PETT/PI/SG-CNT = 9/3/8. All films have a thickness of 10 µm.</p> Full article ">Figure 3
<p>Durability of power factor (<span class="html-italic">PF</span>) at 353 K and 423 K of nano-PETT/PI/SG-CNT hybrid films (film thickness of 10 μm).</p> Full article ">Figure 4
<p>Durability of power factor (<span class="html-italic">PF</span>) at 353 K of nano-PETT/PI/SG-CNT hybrid films (film thickness of 3 μm).</p> Full article ">Figure 5
<p>Comparison of thermogravimetric analyses of nano-PETT/PI/SG-CNT (red line) and nano-PETT/PVC/SG-CNT (black line) hybrid films. Mass ratio: nano-PETT/polymer/SG-CNT = 9/3/8.</p> Full article ">
3107 KiB  
Article
Characterisation of Asphalt Concrete Using Nanoindentation
by Salim Barbhuiya and Benjamin Caracciolo
Materials 2017, 10(7), 823; https://doi.org/10.3390/ma10070823 - 18 Jul 2017
Cited by 12 | Viewed by 4283
Abstract
In this study, nanoindentation was conducted to extract the load-displacement behaviour and the nanomechanical properties of asphalt concrete across the mastic, matrix, and aggregate phases. Further, the performance of hydrated lime as an additive was assessed across the three phases. The hydrated lime [...] Read more.
In this study, nanoindentation was conducted to extract the load-displacement behaviour and the nanomechanical properties of asphalt concrete across the mastic, matrix, and aggregate phases. Further, the performance of hydrated lime as an additive was assessed across the three phases. The hydrated lime containing samples have greater resistance to deformation in the mastic and matrix phases, in particular, the mastic. There is strong evidence suggesting that hydrated lime has the most potent effect on the mastic phase, with significant increase in hardness and stiffness. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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<p>Indentation sites for Set 1 (marked with X).</p> Full article ">Figure 2
<p>Indentation sites for Set 2 (marked with X).</p> Full article ">Figure 3
<p>Load-displacement curve for two separate indents on mastic phase.</p> Full article ">Figure 4
<p>Load-displacement curve for 10 indents on mastic phase.</p> Full article ">Figure 5
<p>Load-displacement curve for two separate indents on aggregate phase.</p> Full article ">Figure 6
<p>Load-displacement curve for 10 indents on aggregate phase.</p> Full article ">Figure 7
<p>Load-displacement curve for all phases in AC without hydrated lime.</p> Full article ">Figure 8
<p>Load-displacement curve for all phases in AC with hydrated lime.</p> Full article ">Figure 9
<p>Load-displacement curve for mastic phases with hydrated lime.</p> Full article ">Figure 10
<p>Average indentation depth for all phases.</p> Full article ">Figure 11
<p>Young’s modulus and hardness of all phases in sample without hydrated lime.</p> Full article ">Figure 12
<p>Young’s modulus and hardness in mastic phase of sample without hydrated lime.</p> Full article ">Figure 13
<p>Young’s modulus and hardness on mastic and matrix phase for samples with and without hydrated lime.</p> Full article ">Figure 14
<p>Average Young’s modulus values obtained from the indentation grids.</p> Full article ">Figure 15
<p>Average hardness values obtained from the indentation grids.</p> Full article ">
3416 KiB  
Article
Strengthening Effect of Extruded Mg-8Sn-2Zn-2Al Alloy: Influence of Micro and Nano-Size Mg2Sn Precipitates
by Weili Cheng, Yang Bai, Lifei Wang, Hongxia Wang, Liping Bian and Hui Yu
Materials 2017, 10(7), 822; https://doi.org/10.3390/ma10070822 - 18 Jul 2017
Cited by 42 | Viewed by 3775
Abstract
In this study, Mg-8Sn-2Zn-2Al (TZA822) alloys with varying Mg2Sn contents prior to extrusion were obtained by different pre-treatments (without and with T4), and the strengthening response related to micro and nano-size Mg2Sn precipitates in the extruded TZA822 alloys was [...] Read more.
In this study, Mg-8Sn-2Zn-2Al (TZA822) alloys with varying Mg2Sn contents prior to extrusion were obtained by different pre-treatments (without and with T4), and the strengthening response related to micro and nano-size Mg2Sn precipitates in the extruded TZA822 alloys was reported. The results showed that the morphology of nano-size Mg2Sn precipitates exhibits a significant change in basal plane from rod-like to spherical, owing to the decrement in the fraction of micro-size particles before extrusion. Meanwhile, the spherical Mg2Sn precipitates provided a much stronger strengthening effect than did the rod-like ones, which was ascribed to uniform dispersion and refinement of spherical precipitates to effectively hinder basal dislocation slip. As a consequence, the extruded TZA822 alloy with T4 showed a higher tensile yield strength (TYS) of 245 MPa, ultimate tensile strength (UTS) of 320 MPa and elongation (EL) of 26.5%, as well as a lower degree of yield asymmetry than their counterpart without T4. Detailed reasons for the strengthening effect were given and analyzed. Full article
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Graphical abstract

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<p>OM and SEM-SE images of TZA822 alloys prior to extrusion in different states: (<b>a</b>,<b>c</b>) without T4 and (<b>b</b>,<b>d</b>) with T4.</p> Full article ">Figure 2
<p>OM, SEM-SE and TEM images of extruded TZA822 alloys: (<b>a</b>,<b>c</b>,<b>e</b>) without T4 and (<b>b</b>,<b>d</b>,<b>f</b>) with T4, respectively.</p> Full article ">Figure 3
<p>Particle-size distribution and number per area for the extruded TZA822 alloys.</p> Full article ">Figure 4
<p>Bright field TEM images of DRXed region of extruded TZA822 alloys taken from the zone axis of [0001] (inset: SAED pattern) (<b>a</b>) without T4; (<b>b</b>) with T4; (<b>c</b>) The schematic illustration of the two different types of precipitates; (<b>d</b>,<b>e</b>) HR-TEM of rod-like and spherical precipitates.</p> Full article ">Figure 5
<p>The (0002) and (10<math display="inline"> <semantics> <mrow> <mover> <mn>1</mn> <mo stretchy="false">¯</mo> </mover> </mrow> </semantics> </math>0) pole figures of extruded TZA822 alloys. (<b>a</b>) Without T4 and (<b>b</b>) with T4, respectively.</p> Full article ">Figure 6
<p>(<b>a</b>) Tensile and compressive stress-strain curves of the extruded TZA822 alloys; (<b>b</b>) TYS and EL of various Mg based wrought alloys.</p> Full article ">Figure 7
<p>OM from gage sections of fractured tensile samples for the extruded TZA822 alloys in different states: (<b>a</b>) without T4 and (<b>b</b>) with T4.</p> Full article ">
7015 KiB  
Article
Thin-Film Coated Plastic Wrap for Food Packaging
by Hsin-Yu Wu, Ting-Xuan Liu, Chia-Hsun Hsu, Yun-Shao Cho, Zhi-Jia Xu, Shu-Chuan Liao, Bo-Han Zeng, Yeu-Long Jiang and Shui-Yang Lien
Materials 2017, 10(7), 821; https://doi.org/10.3390/ma10070821 - 18 Jul 2017
Cited by 8 | Viewed by 6192
Abstract
In this study, the antimicrobial property and food package capability of polymethylpentene (PMP) substrate with silicon oxdie (SiOx) and organic silicon (SiCxHy) stacked layers deposited by an inductively coupled plasma chemical vapor deposition system were investigated. The [...] Read more.
In this study, the antimicrobial property and food package capability of polymethylpentene (PMP) substrate with silicon oxdie (SiOx) and organic silicon (SiCxHy) stacked layers deposited by an inductively coupled plasma chemical vapor deposition system were investigated. The experimental results show that the stacked pair number of SiOx/SiCxHy on PMP is limited to three pairs, beyond which the films will crack and cause package failure. The three-pair SiOx/SiCxHy on PMP shows a low water vapor transmission rate of 0.57 g/m2/day and a high water contact angle of 102°. Three-pair thin-film coated PMP demonstrates no microbe adhesion and exhibits antibacterial properties within 24 h. Food shelf life testing performed at 28 °C and 80% humidity reports that the three-pair thin-film coated PMP can enhance the food shelf-life to 120 h. The results indicate that the silicon-based thin film may be a promising material for antibacterial food packaging applications to extend the shelf-life of food products. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2017)
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<p>Optical microscope images of the polymethylpentene (PMP) without, with one-, two-, three- and four-pair SiO<span class="html-italic"><sub>x</sub></span>/SiC<span class="html-italic"><sub>x</sub></span>H<span class="html-italic"><sub>y</sub></span> films.</p> Full article ">Figure 2
<p>Water vapor transmission rate for the PMP without and with one-, two-, and three-pair SiO<span class="html-italic"><sub>x</sub></span>/SiC<span class="html-italic"><sub>x</sub></span>H<span class="html-italic"><sub>y</sub></span> layers at 40 °C/100% relative humidity (RH).</p> Full article ">Figure 3
<p>Water contact angle images for the PMP (<b>a</b>) without and (<b>b</b>) with SiC<span class="html-italic"><sub>x</sub></span>H<span class="html-italic"><sub>y</sub></span>/three-pair SiO<span class="html-italic"><sub>x</sub></span>/SiC<span class="html-italic"><sub>x</sub></span>H<span class="html-italic"><sub>y</sub></span> stack.</p> Full article ">Figure 4
<p>Ratio of microbe adhesion area to sample area for PMP without and with different pairs of SiO<span class="html-italic"><sub>x</sub></span>/SiC<span class="html-italic"><sub>x</sub></span>H<span class="html-italic"><sub>y</sub></span> stacked films as a function of time.</p> Full article ">Figure 5
<p>SEM images for <span class="html-italic">Escherichia coli</span> adhesion on PMP without and with different pairs of SiO<span class="html-italic"><sub>x</sub></span>/SiC<span class="html-italic"><sub>x</sub></span>H<span class="html-italic"><sub>y</sub></span> stacked films at 72 h. The percentage represents the ratio of microbes to total area.</p> Full article ">Figure 6
<p>Images of food packed by PMP without and with different pairs of SiO<span class="html-italic"><sub>x</sub></span>/SiC<span class="html-italic"><sub>x</sub></span>H<span class="html-italic"><sub>y</sub></span> stacked film.</p> Full article ">Figure 7
<p>Photograph of stretched and rolled PMP with three-pair SiO<span class="html-italic"><sub>x</sub></span>/SiC<span class="html-italic"><sub>x</sub></span>H<span class="html-italic"><sub>y</sub></span> stack.</p> Full article ">
2681 KiB  
Article
Low-Temperature Preparation of Tungsten Oxide Anode Buffer Layer via Ultrasonic Spray Pyrolysis Method for Large-Area Organic Solar Cells
by Ran Ji, Ding Zheng, Chang Zhou, Jiang Cheng, Junsheng Yu and Lu Li
Materials 2017, 10(7), 820; https://doi.org/10.3390/ma10070820 - 18 Jul 2017
Cited by 56 | Viewed by 6006
Abstract
Tungsten oxide (WO3) is prepared by a low-temperature ultrasonic spray pyrolysis method in air atmosphere, and it is used as an anode buffer layer (ABL) for organic solar cells (OSCs). The properties of the WO3 transition metal oxide material as [...] Read more.
Tungsten oxide (WO3) is prepared by a low-temperature ultrasonic spray pyrolysis method in air atmosphere, and it is used as an anode buffer layer (ABL) for organic solar cells (OSCs). The properties of the WO3 transition metal oxide material as well as the mechanism of ultrasonic spray pyrolysis processes are investigated. The results show that the ultrasonic spray pyrolysized WO3 ABL exhibits low roughness, matched energy level, and high conductivity, which results in high charge transport efficiency and suppressive recombination in OSCs. As a result, compared to the OSCs based on vacuum thermal evaporated WO3, a higher power conversion efficiency of 3.63% is reached with low-temperature ultrasonic spray pyrolysized WO3 ABL. Furthermore, the mostly spray-coated OSCs with large area was fabricated, which has a power conversion efficiency of ~1%. This work significantly enhances our understanding of the preparation and application of low temperature-processed WO3, and highlights the potential of large area, all spray coated OSCs for sustainable commercial fabrication. Full article
(This article belongs to the Section Energy Materials)
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<p>(<b>a</b>) Device architecture of inverted organic solar cell (OSC) and (<b>b</b>) Ultrasonic spray pyrolysis system.</p> Full article ">Figure 2
<p>X-ray photoelectron spectroscopy (XPS) spectra of different process tungsten oxide (WO<sub>3</sub>) films. (<b>a</b>) Full scan; (<b>c</b>) W (4f) core levels and (<b>e</b>) O (1s) core levels of spray-coated WO<sub>3</sub> (S-WO<sub>3</sub>) film, respectively; (<b>b</b>) Full scan; (<b>d</b>) W (4f) core levels and (<b>f</b>) O (1s) core levels of evaporated WO<sub>3</sub>) E-WO<sub>3</sub> film, respectively.</p> Full article ">Figure 3
<p>(<b>a</b>) Thermo gravimetric (TG) and differential scanning calorimeter (DSC) profiles of the AT precursor; (<b>b</b>) ultraviolet photo-electron spectroscopy (UPS) results of S-WO<sub>3</sub> film; (<b>c</b>) energy level of the component materials used in the OSCs; (<b>d</b>) XRD pattern of S-WO<sub>3</sub> and E-WO<sub>3</sub>, respectively.</p> Full article ">Figure 4
<p>(<b>a</b>) Current density versus voltage (<span class="html-italic">J–V</span>) characteristics of OSCs with S-WO<sub>3</sub> and E-WO<sub>3</sub> films; (<b>b</b>) external quantum efficiency (<span class="html-italic">EQE</span>) characteristics of OSCs with S-WO<sub>3</sub> and E-WO<sub>3</sub> films; Atomic force microscopy (AFM) images of (<b>c</b>) S-WO<sub>3</sub>; (<b>d</b>) E-WO<sub>3</sub>.</p> Full article ">Figure 5
<p>(<b>a</b>) Equivalent circuit model of the devices. (R1 and CPE1, R2 and C2, R3 represent equivalent of donor and accepter interface, interface between active layer and electrodes, resistance of electrodes, respectively; (<b>b</b>) Cole–Cole plots of the devices based on E-WO<sub>3</sub> and S-WO<sub>3</sub> films with different precursor concentration.</p> Full article ">Figure 6
<p>Dynamics of USP with different substrate temperature.</p> Full article ">Figure 7
<p>(<b>a</b>) Image of a 25 cm<sup>2</sup> OSC device with as-grown S-WO<sub>3</sub> film and (<b>b</b>) <span class="html-italic">J–V</span> characteristic of the OSC.</p> Full article ">
4858 KiB  
Article
Color Shift Failure Prediction for Phosphor-Converted White LEDs by Modeling Features of Spectral Power Distribution with a Nonlinear Filter Approach
by Jiajie Fan, Moumouni Guero Mohamed, Cheng Qian, Xuejun Fan, Guoqi Zhang and Michael Pecht
Materials 2017, 10(7), 819; https://doi.org/10.3390/ma10070819 - 18 Jul 2017
Cited by 23 | Viewed by 7328
Abstract
With the expanding application of light-emitting diodes (LEDs), the color quality of white LEDs has attracted much attention in several color-sensitive application fields, such as museum lighting, healthcare lighting and displays. Reliability concerns for white LEDs are changing from the luminous efficiency to [...] Read more.
With the expanding application of light-emitting diodes (LEDs), the color quality of white LEDs has attracted much attention in several color-sensitive application fields, such as museum lighting, healthcare lighting and displays. Reliability concerns for white LEDs are changing from the luminous efficiency to color quality. However, most of the current available research on the reliability of LEDs is still focused on luminous flux depreciation rather than color shift failure. The spectral power distribution (SPD), defined as the radiant power distribution emitted by a light source at a range of visible wavelength, contains the most fundamental luminescence mechanisms of a light source. SPD is used as the quantitative inference of an LED’s optical characteristics, including color coordinates that are widely used to represent the color shift process. Thus, to model the color shift failure of white LEDs during aging, this paper first extracts the features of an SPD, representing the characteristics of blue LED chips and phosphors, by multi-peak curve-fitting and modeling them with statistical functions. Then, because the shift processes of extracted features in aged LEDs are always nonlinear, a nonlinear state-space model is then developed to predict the color shift failure time within a self-adaptive particle filter framework. The results show that: (1) the failure mechanisms of LEDs can be identified by analyzing the extracted features of SPD with statistical curve-fitting and (2) the developed method can dynamically and accurately predict the color coordinates, correlated color temperatures (CCTs), and color rendering indexes (CRIs) of phosphor-converted (pc)-white LEDs, and also can estimate the residual color life. Full article
(This article belongs to the Special Issue Light Emitting Diodes and Laser Diodes: Materials and Devices)
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<p>(<b>a</b>) The 3D model of selected light-emitting diodes (LED) package; (<b>b</b>) its packaging materials and construction shown in the scanning electron microscope image of cross-section.</p> Full article ">Figure 2
<p>(<b>a</b>) Spectral power distribution (SPD) data collected under the accelerated degradation test; (<b>b</b>) color shift failure time <span class="html-italic">T</span><sub>f</sub> = 529 h defined as when <span class="html-italic">du</span>′<span class="html-italic">v</span>′ = 0.007.</p> Full article ">Figure 3
<p>SPD and luminous mechanism of the selected phosphor-converted white LED (pc-WLED) package.</p> Full article ">Figure 4
<p>Feature extraction from the initial SPD of pc-WLED package with both Gaussian and Lorentzian models (the red (<b>a</b>) and blue (<b>b</b>) dash lines with shadow areas represent the Gaussian and Lorentzian models respectively).</p> Full article ">Figure 5
<p>Particle filter (PF) prediction approach.</p> Full article ">Figure 6
<p>Failure mechanism classification in a pc-WLED package (the blue and red curves represent the initial and aged SPDs, respectively).</p> Full article ">Figure 7
<p>Ratio of extracted areas under the SPD curve.</p> Full article ">Figure 8
<p>Chemical element analysis result of phosphors in the selected LED with the SEM-EDX.</p> Full article ">Figure 9
<p>(<b>a</b>) The 3D model of test sample soldered on a substrate used for FEA simulation; (<b>b</b>) its simulated Kelvin temperature distribution.</p> Full article ">Figure 10
<p>Shift trajectories of normalized features extracted from SPDs by (<b>a</b>) Gaussian model and (<b>b</b>) Lorentzian model until 345 h.</p> Full article ">Figure 11
<p>PF prediction results of four normalized features extracted from the Gaussian model until 529 h (<b>a</b>) Normalized <span class="html-italic">y</span><sub>0</sub>; (<b>b</b>) Normalized <span class="html-italic">A</span><sub>B</sub>; (<b>c</b>) Normalized 1/<span class="html-italic">w</span><sub>Y</sub>; (<b>d</b>) Normalized <span class="html-italic">A</span><sub>Y</sub>.</p> Full article ">Figure 12
<p>PF prediction results of four normalized features extracted from the Lorentzian model until 529 h (<b>a</b>) Normalized <span class="html-italic">y</span><sub>0</sub>; (<b>b</b>) Normalized <span class="html-italic">A</span><sub>B</sub>; (<b>c</b>) Normalized 1/<span class="html-italic">w</span><sub>Y</sub>; (<b>d</b>) Normalized <span class="html-italic">A</span><sub>Y</sub>.</p> Full article ">Figure 13
<p>Prediction errors of (<b>a</b>) <span class="html-italic">u</span>′; (<b>b</b>) <span class="html-italic">v</span>′, (<b>c</b>) correlated color temperature (CCT) and (<b>d</b>) color rendering index (CRI) based on the Gaussian and Lorentzian models.</p> Full article ">Figure 14
<p>Prediction results of <span class="html-italic">du</span>′<span class="html-italic">v</span>′ based on the Gaussian and Lorentzian models.</p> Full article ">
2419 KiB  
Article
Monoclinic 122-Type BaIr2Ge2 with a Channel Framework: A Structural Connection between Clathrate and Layered Compounds
by Xin Gui, Tay-Rong Chang, Tai Kong, Max T. Pan, Robert J. Cava and Weiwei Xie
Materials 2017, 10(7), 818; https://doi.org/10.3390/ma10070818 - 18 Jul 2017
Cited by 4 | Viewed by 4859
Abstract
A new 122-type phase, monoclinic BaIr2Ge2 is successfully synthesized by arc melting; X-ray diffraction and scanning electron microscopy are used to purify the phase and determine its crystal structure. BaIr2Ge2 adopts a clathrate-like channel framework structure of [...] Read more.
A new 122-type phase, monoclinic BaIr2Ge2 is successfully synthesized by arc melting; X-ray diffraction and scanning electron microscopy are used to purify the phase and determine its crystal structure. BaIr2Ge2 adopts a clathrate-like channel framework structure of the monoclinic BaRh2Si2-type, with space group P21/c. Structural comparisons of clathrate, ThCr2Si2, CaBe2Ge2, and BaRh2Si2 structure types indicate that BaIr2Ge2 can be considered as an intermediate between clathrate and layered compounds. Magnetic measurements show it to be diamagnetic and non-superconducting down to 1.8 K. Different from many layered or clathrate compounds, monoclinic BaIr2Ge2 displays a metallic resistivity. Electronic structure calculations performed for BaIr2Ge2 support its observed structural stability and physical properties. Full article
(This article belongs to the Special Issue Metal-Insulator Transition)
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<p>Powder X-ray diffraction pattern of BaIr<sub>2</sub>Ge<sub>2</sub> (Cu Kα radiation, 300 K). Lower—observed pattern; Upper—calculated pattern with marked Miller indices (hkl) based on the single crystal structure.</p> Full article ">Figure 2
<p>Crystal structure of monoclinic BaIr<sub>2</sub>Ge<sub>2</sub> refined by single crystal X-ray diffraction. (<b>a</b>) View down the a-axis; (<b>b</b>) View down the b-axis; (<b>c</b>) The IrGe framework. The channels running along the a-axis have a channel of diameter ~6.45 Å; (<b>d</b>) close-up of the framework structure showing the Ir-Ge bond lengths; (<b>e</b>) Crystal orbital hamilton populations (-COHP) calculation emphasis on the Ir-Ge, Ir-Ir, and Ge-Ge interactions.</p> Full article ">Figure 3
<p>Structural comparison of 122-type phases. (<b>a</b>) Clathrate structure of Ba<sub>3</sub>Ir<sub>4</sub>Ge<sub>16</sub>; (<b>b</b>) Channel framework of BaIr<sub>2</sub>Ge<sub>2</sub>; (<b>c</b>) Layered structure of BaIrGe<sub>3</sub>; (<b>d</b>) The symmetrical pentahedron in Ba<sub>3</sub>Ir<sub>4</sub>Ge<sub>16</sub>; (<b>e</b>) The irregular, non-symmetrical tetrahedron in BaIr<sub>2</sub>Ge<sub>2</sub>; (<b>f</b>) The square pyramid in BaIrGe<sub>3</sub>.</p> Full article ">Figure 4
<p>Basic electronic and magnetic characterization of BaIr<sub>2</sub>Ge<sub>2</sub>. (<b>Left:</b> Main Panel) Temperature-dependent magnetic susceptibility (M/μ<sub>0</sub>H at μ<sub>0</sub>H = 5 T) and (<b>Left:</b> Inserted) field-dependent magnetization measurements showing the near linearity of M (magnetization) vs. H (magnetic field) for fields beyond 5 T at 1.8 K, justifying the use of the a high applied field in the measurements; (<b>Right</b>) Zero-field resistance data from 1.8 K to 300 K.</p> Full article ">Figure 5
<p>Calculated electronic band structure and density of states (DOS) of BaIr<sub>2</sub>Ge<sub>2</sub> using generalized gradient approximation (GGA). (<b>a</b>) Band structure and DOS with spin-orbit coupling emphasis on the energy range from −7 to +7 eV; (<b>b</b>) Band structure calculated by GGA without spin-orbit coupling; (<b>c</b>) Band structure calculated by GGA with spin-orbit coupling.</p> Full article ">
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