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Materials, Volume 9, Issue 11 (November 2016) – 95 articles

Cover Story (view full-size image): Multi-scale analysis of concrete requires validation and determination of input parameters at all scales. This paper presents techniques for making, testing and modelling micro-cubes of cement paste. The micro-cubes are made by precision cutting, grinding and micro-dicing. The microstructure is determined by X-ray tomography. Mechanical testing of the micro-cubes is performed by nano-indentation and the modelling is done by a lattice fracture model. View the paper
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9599 KiB  
Article
Effects of BMP-2 Delivery in Calcium Phosphate Bone Graft Materials with Different Compositions on Bone Regeneration
by Jin-Chul Park, Eun-Bin Bae, Se-Eun Kim, So-Yun Kim, Kyung-Hee Choi, Jae-Won Choi, Ji-Hyeon Bae, Jae-Jun Ryu and Jung-Bo Huh
Materials 2016, 9(11), 954; https://doi.org/10.3390/ma9110954 - 23 Nov 2016
Cited by 10 | Viewed by 5274
Abstract
This study was undertaken to investigate the effect of loading rhBMP-2 onto biphasic calcium phosphate (BCP) and calcium pyrophosphate (CPP) on bone regeneration, and to examine the efficacies of BCP and CPP as rhBMP-2 carriers. Specimens were divided into the BCP, CPP, BCP/BMP, [...] Read more.
This study was undertaken to investigate the effect of loading rhBMP-2 onto biphasic calcium phosphate (BCP) and calcium pyrophosphate (CPP) on bone regeneration, and to examine the efficacies of BCP and CPP as rhBMP-2 carriers. Specimens were divided into the BCP, CPP, BCP/BMP, and CPP/BMP groups; BCP and CPP were in granules and not coated with rhBMP-2. BCP/BMP and CPP/BMP were prepared as discs, which were treated with rhBMP-2 and collagen. Physical and biological features were investigated using in-vitro and in-vivo tests. New bone area percentages (%) in the BCP/BMP and CPP/BMP groups were significantly greater than in the BCP and CPP groups. At weeks 4 and 8 post-implantation, CPP/BMP showed the most new bone growth. Within the limitations of this study, treatment of BCP and CPP with rhBMP-2 significantly enhanced bone regeneration. CPP was found to be a suitable carrier for rhBMP-2. Full article
(This article belongs to the Section Biomaterials)
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Figure 1
<p>Scanning electron microscopic photographs of (<b>a</b>,<b>e</b>) biphasic calcium phosphate (BCP) granules; (<b>b</b>,<b>f</b>) calcium pyrophosphate (CPP) granules; (<b>c</b>,<b>g</b>) a BCP/BMP disc; (<b>d</b>,<b>h</b>) a CPP/BMP disc. White arrow: rhBMP-2 coated collagen (Original magnification ×100 for <b>a</b> to <b>d</b> and ×3000 for <b>e</b> to <b>h</b>).</p> Full article ">Figure 2
<p>Release kinetics of rhBMP-2. CPP/BMP released double the amount of rhBMP-2 than BCP/BMP.</p> Full article ">Figure 3
<p>SEM photographs of graft material surfaces after culture with C2C12 for 14 days. (<b>a</b>) BCP granule; (<b>b</b>) CPP granule; (<b>c</b>) BCP/BMP granule; and (<b>d</b>) CPP/BMP granule (original magnification ×500).</p> Full article ">Figure 4
<p>(<b>a</b>) Proliferation and (<b>b</b>) Alkaline phosphatase (ALP) activity of myoblast cells (C2C12 cells) grown on BCP, CPP, BCP/BMP or CPP/BMP after 1, 3, or 7 days of incubation. The symbol ‘*’ indicates significantly different versus the control (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 5
<p>Hematoxylin and eosin staining of histological sections of defect sites at 4 and 8 weeks’ post-implantation. Black arrow; newly formed bone (original magnification: ×12.5 for rows 1 and 3, and ×40 for rows 2 and 4).</p> Full article ">Figure 6
<p>New bone area percentages at 4 and 8 weeks’ post-implantation. No significant differences were found between the control, BCP, and CPP groups at 4 or 8 weeks. The symbol ‘§’ indicates significantly higher percentage versus the control, BCP, and CPP groups at the indicated time (<span class="html-italic">p</span> &lt; 0.05). The symbol ‘¶’ indicates significantly higher percentage versus BCP/BMP group at the indicated time (<span class="html-italic">p</span> &lt; 0.05). ‘‡’ indicates significantly higher percentage versus the same group at 4 weeks (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 7
<p>X-ray diffraction analysis (XRD) patterns of bone graft materials. (<b>a</b>) BCP containing HA(30): <span class="html-italic">β</span>-TCP(70); (<b>b</b>) CPP.</p> Full article ">Figure 8
<p>(<b>a</b>) Surgical procedures; (<b>b</b>) a schematic of the histometric analysis.</p> Full article ">
2108 KiB  
Article
Recording Characteristics, Microstructure, and Crystallization Kinetics of Ge/GeCu Recording Film Used for Write-Once Blu-Ray Disc
by Sin-Liang Ou, Feng-Min Lai, Wei-Kai Wang, Shih-Yung Huang, An-Cheng Sun, Ching-Ho Tien, Zhi-Jia Xu, Chin-Yen Yeh and Kuo-Sheng Kao
Materials 2016, 9(11), 953; https://doi.org/10.3390/ma9110953 - 23 Nov 2016
Viewed by 4058
Abstract
A Ge67Cu33 (16 nm) layer and a Ge (3 nm)/Ge67Cu33 (16 nm) bilayer were grown by sputtering at room temperature and used as the recording films for write-once blue laser media. In comparison to the crystallization temperature [...] Read more.
A Ge67Cu33 (16 nm) layer and a Ge (3 nm)/Ge67Cu33 (16 nm) bilayer were grown by sputtering at room temperature and used as the recording films for write-once blue laser media. In comparison to the crystallization temperature of Ge in a GeCu film (380.7 °C–405.1 °C), the crystallization temperature of Ge in a Ge/GeCu bilayer could be further decreased to 333.7 °C–382.8 °C. The activation energies of Ge crystallization were 3.51 eV ± 0.05 eV and 1.50 eV ± 0.04 eV for the GeCu and the Ge/GeCu films, respectively, indicating that the Ge/GeCu bilayer possesses a higher feasibility in high-speed optical recording applications. Moreover, the lower activation energy would lead to a larger grain size of Ge crystallization in the Ge/GeCu bilayer after the annealing process. Between the as-deposited and the annealed states, the optical contrasts (@ 405 nm) of the GeCu and the Ge/GeCu films were 26.0% and 47.5%, respectively. This reveals that the Ge/GeCu bilayer is more suitable for the recording film of a write-once blu-ray disc (BD-R) in comparison with the GeCu film. Based on the dynamic tests performed for 2× and 4× recording speeds, the optimum jitter values of the BD-R with the Ge/GeCu recording film were 7.4% at 6.3 mW and 7.6% at 8.6 mW, respectively. Full article
(This article belongs to the Special Issue Selected Papers from IS3C2016)
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<p>Layer structures of the write-once blu-ray discs (BD-Rs) with (<b>a</b>) Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) and (<b>b</b>) Ge (3 nm)/Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) recording films. PC: polycarbonate.</p> Full article ">Figure 2
<p>Relationships between reflectivity and temperature of (<b>a</b>) Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) and (<b>b</b>) Ge (3 nm)/Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) films measured at the heating rates of 5, 10, 20, and 50 °C/min.</p> Full article ">Figure 3
<p>Transmission electron microscopy (TEM) bright field images and electron diffraction patterns of (<b>a</b>) as-deposited and (<b>b</b>) 450 °C-annealed Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) films.</p> Full article ">Figure 4
<p>(<b>a</b>) TEM image and electron diffraction pattern of as-deposited Ge (3 nm)/Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) film; (<b>b</b>) TEM image and electron diffraction pattern of annealed Ge/GeCu film; (<b>c</b>) TEM image of region 2 of the annealed film; (<b>d</b>) TEM bright field image and selected area electron diffraction pattern of parallelogram-shaped grain formed in the 450 °C-annealed Ge/GeCu film; (<b>e</b>) TEM bright field image and selected area electron diffraction pattern of hexagon-shaped grain formed in the 450 °C-annealed Ge/GeCu film.</p> Full article ">Figure 5
<p>Plots of ln[<span class="html-italic">A</span>/(<span class="html-italic">T<sub>x</sub></span>)<sup>2</sup>] versus (1/<span class="html-italic">T<sub>x</sub></span>) of (<b>a</b>) Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) and (<b>b</b>) Ge (3 nm)/Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) films for the Ge crystallization.</p> Full article ">Figure 6
<p>Reflectivity spectra of the as-deposited and the 450 °C-annealed states for (<b>a</b>) Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) and (<b>b</b>) Ge (3 nm)/Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) films.</p> Full article ">Figure 7
<p>Jitter values and modulations as a function of writing power at 2× and 4× recording speeds for the BD-Rs with (<b>a</b>) Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) and (<b>b</b>) Ge (3 nm)/Ge<sub>67</sub>Cu<sub>33</sub> (16 nm) recording films.</p> Full article ">
4296 KiB  
Article
The Effect of Curing Temperature on the Properties of Cement Pastes Modified with TiO2 Nanoparticles
by Karine Pimenta Teixeira, Isadora Perdigão Rocha, Leticia De Sá Carneiro, Jessica Flores, Edward A. Dauer and Ali Ghahremaninezhad
Materials 2016, 9(11), 952; https://doi.org/10.3390/ma9110952 - 23 Nov 2016
Cited by 42 | Viewed by 6236
Abstract
This paper investigates the effect of curing temperature on the hydration, microstructure, compressive strength, and transport of cement pastes modified with TiO2 nanoparticles. These characteristics of cement pastes were studied using non-evaporable water content measurement, X-ray diffraction (XRD), compressive strength test, electrical [...] Read more.
This paper investigates the effect of curing temperature on the hydration, microstructure, compressive strength, and transport of cement pastes modified with TiO2 nanoparticles. These characteristics of cement pastes were studied using non-evaporable water content measurement, X-ray diffraction (XRD), compressive strength test, electrical resistivity and porosity measurements, and scanning electron microscopy (SEM). It was shown that temperature enhanced the early hydration. The cement pastes cured at elevated temperatures generally showed an increase in compressive strength at an early age compared to the cement paste cured at room temperature, but the strength gain decreased at later ages. The electrical resistivity of the cement pastes cured at elevated temperatures was found to decrease more noticeably at late ages compared to that of the room temperature cured cement paste. SEM examination indicated that hydration product was more uniformly distributed in the microstructure of the cement paste cured at room temperature compared to the cement pastes cured at elevated temperatures. It was observed that high temperature curing decreased the compressive strength and electrical resistivity of the cement pastes at late ages in a more pronounced manner when higher levels of TiO2 nanoparticles were added. Full article
(This article belongs to the Section Advanced Materials Characterization)
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<p>(<b>a</b>) Particle size distribution of TiO<sub>2</sub> nanoparticles; (<b>b</b>) Scanning electron microscopy (SEM) image of TiO<sub>2</sub> nanoparticles used in the experiment.</p> Full article ">Figure 2
<p>Non-evaporable water contents of the neat cement paste and the cement pastes modified with 0.8%, 2.5%, and 5% TiO<sub>2</sub> nanoparticles, cured at varied temperatures (room temperature (RT), 40 °C and 60 °C), at different ages. CP: cement paste.</p> Full article ">Figure 3
<p>Compressive strengths of the cement pastes, cured at varied temperatures (room temperature (RT), 40 °C and 60 °C), at 3 days, 14 days, and 28 days of age.</p> Full article ">Figure 4
<p>Electrical resistivity of the cement pastes, cured at varied temperatures (room temperature (RT), 40 °C and 60 °C), at 3 days, 14 days, and 28 days of age.</p> Full article ">Figure 5
<p>Porosity of the cement pastes, cured at varied temperatures (room temperature (RT), 40 °C, and 60 °C), at 3 days, 14 days, and 28 days of age.</p> Full article ">Figure 6
<p>X-ray Diffraction (XRD) spectra of the neat cement paste and cement pastes with 0.8% TiO<sub>2</sub> nanoparticles cured at (<b>a</b>) room temperature and (<b>b</b>) at 60 °C. CH: calcium hydroxide; CSH: calcium silicate hydrate; C<sub>3</sub>S: tricalcium silicate; C<sub>2</sub>S: dicalcium silicate.</p> Full article ">Figure 7
<p>SEM micrographs showing the microstructure at 3 days of (<b>a</b>) the neat cement paste; (<b>b</b>) cement paste with 0.8% TiO<sub>2</sub> nanoparticles, respectively, cured at room temperature; (<b>c</b>) the neat cement paste; and (<b>d</b>) cement paste with 0.8% TiO<sub>2</sub> nanoparticles, cured at 60 °C.</p> Full article ">Figure 7 Cont.
<p>SEM micrographs showing the microstructure at 3 days of (<b>a</b>) the neat cement paste; (<b>b</b>) cement paste with 0.8% TiO<sub>2</sub> nanoparticles, respectively, cured at room temperature; (<b>c</b>) the neat cement paste; and (<b>d</b>) cement paste with 0.8% TiO<sub>2</sub> nanoparticles, cured at 60 °C.</p> Full article ">Figure 8
<p>SEM micrographs showing the microstructure at 28 days of (<b>a</b>) the neat cement paste; (<b>b</b>) cement paste with 0.8% TiO<sub>2</sub> nanoparticles, respectively, cured at room temperature; (<b>c</b>) the neat cement paste; and (<b>d</b>) cement paste with 0.8% TiO<sub>2</sub> nanoparticles, cured at 60 °C.</p> Full article ">
19218 KiB  
Article
Fabrication of Al/Mg/Al Composites via Accumulative Roll Bonding and Their Mechanical Properties
by Jinfeng Nie, Mingxing Liu, Fang Wang, Yonghao Zhao, Yusheng Li, Yang Cao and Yuntian Zhu
Materials 2016, 9(11), 951; https://doi.org/10.3390/ma9110951 - 23 Nov 2016
Cited by 51 | Viewed by 5881
Abstract
Al(1060)/Mg(AZ31)/Al(1060) multilayered composite was successfully produced using an accumulative roll bonding (ARB) process for up to four cycles at an elevated temperature (400 °C). The microstructure evolution of the composites and the bonding characteristics at the interfaces between Al and Mg layers with [...] Read more.
Al(1060)/Mg(AZ31)/Al(1060) multilayered composite was successfully produced using an accumulative roll bonding (ARB) process for up to four cycles at an elevated temperature (400 °C). The microstructure evolution of the composites and the bonding characteristics at the interfaces between Al and Mg layers with increasing ARB cycles were characterized through optical microscopy, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). It was found that the grains of Al and Mg layers were significantly refined and Al3Mg2 and Al12 Mg17 intermetallic compound layers formed at the Al/Mg bonding interfaces. The strength increased gradually and the ultimate tensile strength (UTS) reached a maximum value of about 240 MPa at the third pass. Furthermore, the strengthening mechanism of the composite was analyzed based on the fracture morphologies. Full article
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<p>Diagrammatic illustration of the accumulate roll-bonding (ARB) process.</p> Full article ">Figure 2
<p>SEM micrographs of ARBed Al/Mg composites: (<b>a</b>) primary sandwich; (<b>b</b>) 2nd; (<b>c</b>) 3rd; (<b>d</b>) 4th cycle.</p> Full article ">Figure 2 Cont.
<p>SEM micrographs of ARBed Al/Mg composites: (<b>a</b>) primary sandwich; (<b>b</b>) 2nd; (<b>c</b>) 3rd; (<b>d</b>) 4th cycle.</p> Full article ">Figure 3
<p>Thickness variations of Al and Mg layers in Al/Mg/Al composite during ARB cycles.</p> Full article ">Figure 4
<p>SEM images and corresponding EDS line-scanning analysis across the interfaces of the Al/Mg composite after (<b>a</b>,<b>b</b>) one; (<b>c</b>,<b>d</b>) two and (<b>e</b>,<b>f</b>) three; (<b>g</b>,<b>h</b>) four cycles.</p> Full article ">Figure 5
<p>EDS line-scanning analysis of the fresh interface in the Al/Mg composites after three cycles: (<b>a</b>) SEM image; (<b>b</b>) element distribution of Mg and Al along line A-B across the interface.</p> Full article ">Figure 6
<p>(<b>a</b>,<b>b</b>) TEM bright field images of the interface of Al/Mg/Al laminated composites after three cycles and (<b>c</b>,<b>d</b>) magnified microstructures of interface marked by A and B in (<b>b</b>).</p> Full article ">Figure 7
<p>Optical micrographs showing the microstructure of Mg layer in the Al/Mg/Al laminated composites after (<b>a</b>) one; (<b>b</b>) two; (<b>c</b>) three; (<b>d</b>) four cycles.</p> Full article ">Figure 8
<p>EBSD maps of surface Al layer in the Al/Mg/Al laminated composites after (<b>a</b>) one; (<b>b</b>) two; (<b>c</b>) three; (<b>d</b>) four cycles.</p> Full article ">Figure 9
<p>EBSD maps of Al layers through thickness of the laminated composites with different cycles: (<b>a</b>) surface Al layer after the 1st cycle; (<b>b</b>,<b>c</b>) surface and center layer after the 2nd cycles; (<b>d</b>–<b>f</b>) surface, subsurface and center layer after the 3rd cycles; (<b>g</b>–<b>i</b>) surface, subsurface and center layer after the 4th cycles.</p> Full article ">Figure 9 Cont.
<p>EBSD maps of Al layers through thickness of the laminated composites with different cycles: (<b>a</b>) surface Al layer after the 1st cycle; (<b>b</b>,<b>c</b>) surface and center layer after the 2nd cycles; (<b>d</b>–<b>f</b>) surface, subsurface and center layer after the 3rd cycles; (<b>g</b>–<b>i</b>) surface, subsurface and center layer after the 4th cycles.</p> Full article ">Figure 10
<p>Mechanical properties of Al/Mg/Al multilayered composites with different ARB cycles.</p> Full article ">Figure 11
<p>Hardness variation of Al and Mg layers in the Al/Mg/Al composites at different ARB cycles.</p> Full article ">Figure 12
<p>The panoramic SEM fractographs of the Al/Mg/Al laminated composites fabricated after (<b>a</b>) one; (<b>b</b>) two; (<b>c</b>) three and (<b>d</b>) four cycles.</p> Full article ">
5936 KiB  
Article
Friction and Wear Reduction of Eccentric Journal Bearing Made of Sn-Based Babbitt for Ore Cone Crusher
by Auezhan Amanov, Byungmin Ahn, Moon Gu Lee, Yongho Jeon and Young-Sik Pyun
Materials 2016, 9(11), 950; https://doi.org/10.3390/ma9110950 - 22 Nov 2016
Cited by 15 | Viewed by 7787
Abstract
An anti-friction Babbitt alloy-coated bearing made by a casting process is a journal bearing, which is used in an ore cone crusher eccentric. The main purpose of the Babbitt coated eccentric is to provide a low friction to support and guide a rotating [...] Read more.
An anti-friction Babbitt alloy-coated bearing made by a casting process is a journal bearing, which is used in an ore cone crusher eccentric. The main purpose of the Babbitt coated eccentric is to provide a low friction to support and guide a rotating shaft. Despite the fact that the Babbitt-coated eccentric offers a low friction coefficient and can be operated without a continuous supply of lubricant, it suffers from mining environments and short service life. In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was used to further reduce the friction coefficient, to increase the wear resistance, and to extend the service life of the Sn-based Babbitt metal. The friction and wear behavior of the Sn-based Babbitt metal was investigated using a block-on-ring tester under both dry and oil-lubricated conditions. The results of the experiments revealed that the friction and wear behavior of Sn-based Babbitt metal could be improved by the application of the UNSM technique. The friction and wear mechanisms of the specimens were explained and discussed in terms of changes in surface properties—microstructure, surface hardness, surface roughness, etc. Full article
(This article belongs to the Special Issue Tribological Behavior of Materials by Surface Engineering)
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Figure 1
<p>A schematic view of a UNSM device.</p> Full article ">Figure 2
<p>Diagram of fundamental parameters of the UNSM treatment.</p> Full article ">Figure 3
<p>3D laser microscopic images of the (<b>a</b>) untreated and (<b>b</b>) UNSM-treated Babbitt specimens. Atomic force microscopy (AFM) images of the UNSM-treated Babbitt specimen showing (<b>c</b>) the wavy grooves and (<b>d</b>) dimples on the surface.</p> Full article ">Figure 3 Cont.
<p>3D laser microscopic images of the (<b>a</b>) untreated and (<b>b</b>) UNSM-treated Babbitt specimens. Atomic force microscopy (AFM) images of the UNSM-treated Babbitt specimen showing (<b>c</b>) the wavy grooves and (<b>d</b>) dimples on the surface.</p> Full article ">Figure 4
<p>A schematic view of a block-on-ring friction tester used in this study.</p> Full article ">Figure 5
<p>Comparison in surface roughness for the untreated and UNSM-treated Babbitt specimens. The average surface roughness (<span class="html-italic">Ra</span>) of the untreated and UNSM-treated specimens was about 0.26 and 0.14 µm, respectively.</p> Full article ">Figure 6
<p>(<b>a</b>) Comparison in surface hardness with respect to depth from the top surface for the untreated and UNSM-treated Babbitt specimens: the surface hardness was about 25 and 31 HV for the untreated and UNSM-treated specimens, respectively; (<b>b</b>) Typical <span class="html-italic">P</span>-<span class="html-italic">h</span> curves of the untreated and UNSM-treated specimens obtained from nano-indentation.</p> Full article ">Figure 7
<p>Comparison of indentations created on the surface of the (<b>a</b>) untreated and (<b>b</b>) UNSM-treated Babbitt specimens.</p> Full article ">Figure 8
<p>Variation in friction coefficient of the untreated and UNSM-treated Babbitt specimens in (<b>a</b>) dry and (<b>b</b>) oil-lubricated conditions, respectively.</p> Full article ">Figure 9
<p>Comparison of wear amount for the untreated and UNSM-treated Babbitt specimens in dry and oil-lubricated conditions, respectively.</p> Full article ">Figure 10
<p>Comparison of cross-sectional wear track profiles of the untreated and UNSM-treated Babbitt specimens in (<b>a</b>) dry and (<b>b</b>) oil-lubricated conditions, respectively.</p> Full article ">Figure 11
<p>Wear track scanning electron microscopy (SEM) images of the Babbitt specimens in dry and oil-lubricated conditions. (<b>a</b>) Untreated in dry conditions; (<b>b</b>) UNSM-treated in dry conditions; (<b>c</b>) untreated in oil-lubricated conditions and (<b>d</b>) UNSM-treated in oil-lubricated conditions.</p> Full article ">Figure 12
<p>Energy-dispersive X-ray spectroscopy (EDX) results obtained from the wear track of the Babbitt specimens in dry and oil-lubricated conditions. (<b>a</b>) Untreated in dry conditions; (<b>b</b>) UNSM-treated in dry conditions; (<b>c</b>) untreated in oil-lubricated conditions and (<b>d</b>) UNSM-treated in oil-lubricated conditions.</p> Full article ">
16565 KiB  
Article
In Vitro and In Vivo Study of a Novel Porcine Collagen Membrane for Guided Bone Regeneration
by Eisner Salamanca, Chi-Yang Tsai, Yu-Hwa Pan, Yu-Te Lin, Haw-Ming Huang, Nai-Chia Teng, Che-Tong Lin, Sheng-Wei Feng and Wei-Jen Chang
Materials 2016, 9(11), 949; https://doi.org/10.3390/ma9110949 - 22 Nov 2016
Cited by 18 | Viewed by 6238
Abstract
For years, in order to improve bone regeneration and prevent the need of a second stage surgery to remove non-resorbable membranes, biological absorbable membranes have gradually been developed and applied in guided tissue regeneration (GTR). The present study’s main objective was to achieve [...] Read more.
For years, in order to improve bone regeneration and prevent the need of a second stage surgery to remove non-resorbable membranes, biological absorbable membranes have gradually been developed and applied in guided tissue regeneration (GTR). The present study’s main objective was to achieve space maintenance and bone regeneration using a new freeze-dried developed porcine collagen membrane, and compare it with an already commercial collagen membrane, when both were used with a bovine xenograft in prepared alveolar ridge bone defects. Prior to surgery, the membrane’s vitality analysis showed statistically significant higher cell proliferation in the test membrane over the commercial one. In six beagle dogs, commercial bone xenograft was packed in lateral ridge bone defects prepared in the left and right side and then covered with test porcine collagen membrane or commercial collagen membrane. Alveolar height changes were measured. Histomorphometric results, in vitro and in vivo properties indicated that the new porcine collagen membrane is biocompatible, enhances bone xenograft osteoconduction, and reduces the alveolar ridge height reabsorption rate. Full article
(This article belongs to the Special Issue Materials for Hard and Soft Tissue Engineering: Novel Approaches)
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Figure 1
<p>Surgical procedure for the treatment of bone defects in both groups. (<b>a</b>) Left bone box-shaped 5 mm × 5 mm defect prepared at the mesial side of the fourth premolar; (<b>b</b>) Xenograft placement within the defect; (<b>c</b>) The graft covered with the test collagen membrane; (<b>d</b>) primary closure was achieved. Steps in the surgical site; (<b>e</b>) Right bone box-shaped 5 mm × 5 mm defect prepared at the mesial side of the fourth premolar; (<b>f</b>) Xenograft placement within the defect; (<b>g</b>) The graft covered with the control membrane; (<b>h</b>) primary closure was achieved.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) showed: (<b>a</b>) Control membrane bilayer; (<b>b</b>) Test membrane monolayer; (<b>c</b>) Control membrane surface after 3 days with MG-63 cells in Dulbecco’s Modified Eagle’s Medium; (<b>d</b>) Test membrane surface after 3 days with MG-63 cells in Dulbecco’s Modified Eagle’s Medium.</p> Full article ">Figure 3
<p>MTT assay. Vitality analysis comparison between both membranes at (<b>a</b>) 1; (<b>b</b>) 3 and (<b>c</b>) 5 days. * <span class="html-italic">P</span> &lt; 0.001.</p> Full article ">Figure 4
<p>Surgical sites at 4 and 8 weeks post-surgery. In vivo observation of surgical sites and tissue regeneration at 4 and 8 weeks post-surgery. (<b>a</b>) Four weeks after surgery, the area treated with the test collagen membrane healed uneventfully; (<b>b</b>) Same surgical side from 4a image, the flap was elevated, and the bone defects demonstrated healing with a bone-like tissue; (<b>c</b>) Four weeks after the surgery, the area treated with the control membrane healed uneventfully; (<b>d</b>) The flap was elevated in same surgical side from 4c image, and the bone defect demonstrated healing with a bone-like tissue. Measurements from the cemento enamel junction (CEJ) showed the regained alveolar ridge height with a periodontal probe; (<b>e</b>) Eight weeks after surgery, the area treated with the test collagen membrane healed uneventfully; (<b>f</b>) Same surgical side from 4e image, the flap was elevated, and the bone defect demonstrated healing with a bone-like tissue; (<b>g</b>) Eight weeks after the surgery, the area treated with the control membrane healed uneventfully; (<b>h</b>) The flap was elevated in same surgical side from 4g image, and the bone defect demonstrated healing with a bone-like tissue. Measurements from the CEJ showed the regained alveolar ridge height with a periodontal probe.</p> Full article ">Figure 5
<p>In vivo height changes of the alveolar ridge. Bone defects height changes at different time points, where 0 indicates surgery day. * <span class="html-italic">P</span> &lt; 0.001.</p> Full article ">Figure 6
<p>Histology and histomorphometric analysis (H&amp;E stain): The use of both membranes showed similar behavior at 4 weeks post-surgery with residual collagen in the most coronal portion of the bone defect with woven new bone tissue and residual bone grafts filling the defect. Moreover, connective tissue surrounded some of the graft particles. (<b>a</b>–<b>c</b>) the test collagen membrane; (<b>d</b>–<b>f</b>) the control collagen membrane; In the test membrane group, (<b>a</b>) showed the intact test membrane (10×); (<b>b</b>) indicated new bone formation (nb) (80×) and (<b>c</b>) demonstrated residual bone grafts (G) (200×); In the control group, (<b>d</b>) showed the perforated membrane(10×); (<b>e</b>) performed new bone formation (nb); and (<b>f</b>) showed inflammation (P) without bone graft residual. At 8 weeks; (<b>g</b>) presented the test membrane (c) (10×); (<b>h</b>) showed the new bone formation (nb) without inflammation (80×) in the test group and (<b>i</b>) performed bone graft residual (G) (200×) under the test membrane; In the control group, (<b>j</b>) indicated the residual membrane (c) (10×); (<b>k</b>) showed the new bone formation (ob) surrounded with connective tissue (80×) and (<b>l</b>) also performed the higher magnification of (k) (200×).</p> Full article ">Figure 7
<p>Percentage (%) distribution of the bone tissue, connective tissue, and residual bone grafts at (<b>a</b>) 4 and (<b>b</b>) 8 weeks.</p> Full article ">
2533 KiB  
Article
Prediction of Three-Dimensional Downward Flame Spread Characteristics over Poly(methyl methacrylate) Slabs in Different Pressure Environments
by Kun Zhao, Xiao-Dong Zhou, Xue-Qiang Liu, Lei Lu, Zhi-Bo Wu, Fei Peng, Xiao-Yu Ju and Li-Zhong Yang
Materials 2016, 9(11), 948; https://doi.org/10.3390/ma9110948 - 22 Nov 2016
Cited by 15 | Viewed by 4664
Abstract
The present study is aimed at predicting downward flame spread characteristics over poly(methyl methacrylate) (PMMA) with different sample dimensions in different pressure environments. Three-dimensional (3-D) downward flame spread experiments on free PMMA slabs were conducted at five locations with different altitudes, which provide [...] Read more.
The present study is aimed at predicting downward flame spread characteristics over poly(methyl methacrylate) (PMMA) with different sample dimensions in different pressure environments. Three-dimensional (3-D) downward flame spread experiments on free PMMA slabs were conducted at five locations with different altitudes, which provide different pressures. Pressure effects on the flame spread rate, profile of pyrolysis front and flame height were analyzed at all altitudes. The flame spread rate in the steady-state stage was calculated based on the balance on the fuel surface and fuel properties. Results show that flame spread rate increases exponentially with pressure, and the exponent of pressure further shows an increasing trend with the thickness of the sample. The angle of the pyrolysis front emerged on sample residue in the width direction, which indicates a steady-burning stage, varies clearly with sample thicknesses and ambient pressures. A global non-dimensional equation was proposed to predict the variation tendency of the angle of the pyrolysis front with pressure and was found to fit well with the measured results. In addition, the dependence of average flame height on mass burning rate, sample dimension and pressure was proposed based on laminar diffusion flame theory. The fitted exponent of experimental data is 1.11, which is close to the theoretical value. Full article
(This article belongs to the Special Issue Thermal Sciences and Thermodynamics of Materials)
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<p>Schematic illustration of the experimental apparatus.</p> Full article ">Figure 2
<p>Mass loss rate histories and recorded flame profiles for 2 mm sample in 102 kPa. The flame spread process is divided into three stages: (1) ignition stage; (2) development stage; (3) steady-state stage.</p> Full article ">Figure 3
<p>Sketch diagram of the theoretical model in the steady-state stage. Heating region in the model includes two parts, preheated region and pyrolysis surface. Total heat fluxes at preheated region and pyrolysis surface are <span class="html-italic">q<sub>s</sub></span> and <span class="html-italic">q<sub>p</sub></span>, respectively. α, β and γ are characteristic angles that emerged on sample residue in the steady-state stage. <math display="inline"> <semantics> <mrow> <msub> <mover accent="true"> <mi>m</mi> <mo>˙</mo> </mover> <mi>g</mi> </msub> <msub> <mi>h</mi> <mi>p</mi> </msub> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <msub> <mover accent="true"> <mi>m</mi> <mo>˙</mo> </mover> <mi>s</mi> </msub> <msub> <mi>h</mi> <mo>∞</mo> </msub> </mrow> </semantics> </math> refer to the variation of enthalpy of gas phase and solid phase. <span class="html-italic">T<sub>p</sub></span>, <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mo>∞</mo> </msub> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mi mathvariant="sans-serif">ε</mi> </semantics> </math> are pyrolysis temperature, ambient temperature and preheated length, respectively.</p> Full article ">Figure 4
<p>Angle of pyrolysis front (α) with respect to ambient pressure for different sample thicknesses (<math display="inline"> <semantics> <mi mathvariant="sans-serif">δ</mi> </semantics> </math>).</p> Full article ">Figure 5
<p>Comparisons between experimental and theoretical flame spread rates over a 5 mm slab for different widths under different pressure environments.</p> Full article ">Figure 6
<p>Comparisons between experimental and theoretical flame spread rates over 2, 10 mm slabs under three different pressure environments.</p> Full article ">Figure 7
<p>Fitted relationships between flame spread rate and pressure for different sized samples. The horizontal and vertical coordinates are the values of non-dimensional pressure (<math display="inline"> <semantics> <mrow> <msup> <mi>P</mi> <mo>*</mo> </msup> </mrow> </semantics> </math>) and non-dimensional flame spread rate (<math display="inline"> <semantics> <mrow> <msub> <mi>V</mi> <mi>f</mi> </msub> <msup> <mrow/> <mo>*</mo> </msup> </mrow> </semantics> </math>) after logarithm.</p> Full article ">Figure 8
<p>Non-dimensional dependence of <math display="inline"> <semantics> <mrow> <mi>sin</mi> <mo stretchy="false">(</mo> <mrow> <mi mathvariant="sans-serif">α</mi> <mo>/</mo> <mn>2</mn> </mrow> <mo stretchy="false">)</mo> </mrow> </semantics> </math> on pressure.</p> Full article ">Figure 9
<p>Relationship between averaged flame height and burning rate: <math display="inline"> <semantics> <mrow> <msub> <mi>H</mi> <mi>f</mi> </msub> </mrow> </semantics> </math> to <math display="inline"> <semantics> <mrow> <mfrac> <mover accent="true"> <mi>m</mi> <mo>˙</mo> </mover> <mrow> <mi>W</mi> <msup> <mi>P</mi> <mrow> <mrow> <mn>1</mn> <mo>/</mo> <mn>2</mn> </mrow> </mrow> </msup> </mrow> </mfrac> </mrow> </semantics> </math>. The red line is an exponential fit to the experimental data.</p> Full article ">Figure 10
<p>Non-dimensional dependence of flame height on pressure.</p> Full article ">
2384 KiB  
Article
Optimizing Injection Molding Parameters of Different Halloysites Type-Reinforced Thermoplastic Polyurethane Nanocomposites via Taguchi Complemented with ANOVA
by Tayser Sumer Gaaz, Abu Bakar Sulong, Abdul Amir H. Kadhum, Mohamed H. Nassir and Ahmed A. Al-Amiery
Materials 2016, 9(11), 947; https://doi.org/10.3390/ma9110947 - 22 Nov 2016
Cited by 17 | Viewed by 6452
Abstract
Halloysite nanotubes-thermoplastic polyurethane (HNTs-TPU) nanocomposites are attractive products due to increasing demands for specialized materials. This study attempts to optimize the parameters for injection just before marketing. The study shows the importance of the preparation of the samples and how well these parameters [...] Read more.
Halloysite nanotubes-thermoplastic polyurethane (HNTs-TPU) nanocomposites are attractive products due to increasing demands for specialized materials. This study attempts to optimize the parameters for injection just before marketing. The study shows the importance of the preparation of the samples and how well these parameters play their roles in the injection. The control parameters for injection are carefully determined to examine the mechanical properties and the density of the HNTs-TPU nanocomposites. Three types of modified HNTs were used as untreated HNTs (uHNTs), sulfuric acid treated (aHNTs) and a combined treatment of polyvinyl alcohol (PVA)-sodium dodecyl sulfate (SDS)-malonic acid (MA) (treatment (mHNTs)). It was found that mHNTs have the most influential effect of producing HNTs-TPU nanocomposites with the best qualities. One possible reason for this extraordinary result is the effect of SDS as a disperser and MA as a crosslinker between HNTs and PVA. For the highest tensile strength, the control parameters are demonstrated at 150 °C (injection temperature), 8 bar (injection pressure), 30 °C (mold temperature), 8 min (injection time), 2 wt % (HNTs loading) and mHNT (HNTs type). Meanwhile, the optimized combination of the levels for all six control parameters that provide the highest Young’s modulus and highest density was found to be 150 °C (injection temperature), 8 bar (injection pressure), 32 °C (mold temperature), 8 min (injection time), 3 wt % (HNTs loading) and mHNT (HNTs type). For the best tensile strain, the six control parameters are found to be 160 °C (injection temperature), 8 bar (injection pressure), 32 °C (mold temperature), 8 min (injection time), 2 wt % (HNTs loading) and mHNT (HNTs type). For the highest hardness, the best parameters are 140 °C (injection temperature), 6 bar (injection pressure), 30 °C (mold temperature), 8 min (injection time), 2 wt % (HNTs loading) and mHNT (HNTs type). The analyses are carried out by coordinating Taguchi and ANOVA approaches. Seemingly, mHNTs has shown its very important role in the resulting product. Full article
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<p>Samples of (<b>a</b>) thermoplastic polyurethane (TPU) matrix, (<b>b</b>–<b>d</b>) 1, 2, 3 wt % untreated halloysite nanotubes (<span class="html-italic">u</span>HNTs)-TPU nanocomposites, (<b>e</b>–<b>g</b>) 1, 2, 3 wt % acid treated HNTs (<span class="html-italic">a</span>HNTs)-TPU nanocomposites, (<b>h</b>–<b>j</b>) 1, 2, 3 wt % modified HNTs (<span class="html-italic">m</span>HNTs)-TPU nanocomposites.</p> Full article ">Figure 2
<p>The experimental layout (L<sub>27</sub> (3<sup>13</sup>)) Taguchi model for experimentation.</p> Full article ">Figure 3
<p>S/N results for the five responses.</p> Full article ">Figure 4
<p>Response for S/N ratios “larger is better”.</p> Full article ">Figure 5
<p>The effect of the levels of the control parameters on the responses: (<b>a</b>) tensile strength; (<b>b</b>) Young’s modulus; (<b>c</b>) tensile strain; (<b>d</b>) hardness; and (<b>e</b>) density.</p> Full article ">Figure 5 Cont.
<p>The effect of the levels of the control parameters on the responses: (<b>a</b>) tensile strength; (<b>b</b>) Young’s modulus; (<b>c</b>) tensile strain; (<b>d</b>) hardness; and (<b>e</b>) density.</p> Full article ">Figure 6
<p>FESEM (10,000×) of (<b>a</b>) TPU matrix; (<b>b</b>) 1 wt % <span class="html-italic">u</span>HNTs-TPU nanocomposites; (<b>c</b>) 3 wt % <span class="html-italic">u</span>HNTs-TPU nanocomposites; (<b>d</b>) 1 wt % <span class="html-italic">a</span>HNTs-TPU nanocomposites; (<b>e</b>) 3 wt % <span class="html-italic">a</span>HNTs-TPU nanocomposites; (<b>f</b>) 1 wt % <span class="html-italic">m</span>HNTs-TPU nanocomposites; and (<b>g</b>) 3 wt % <span class="html-italic">m</span>HNT-TPU nanocomposites.</p> Full article ">Figure 6 Cont.
<p>FESEM (10,000×) of (<b>a</b>) TPU matrix; (<b>b</b>) 1 wt % <span class="html-italic">u</span>HNTs-TPU nanocomposites; (<b>c</b>) 3 wt % <span class="html-italic">u</span>HNTs-TPU nanocomposites; (<b>d</b>) 1 wt % <span class="html-italic">a</span>HNTs-TPU nanocomposites; (<b>e</b>) 3 wt % <span class="html-italic">a</span>HNTs-TPU nanocomposites; (<b>f</b>) 1 wt % <span class="html-italic">m</span>HNTs-TPU nanocomposites; and (<b>g</b>) 3 wt % <span class="html-italic">m</span>HNT-TPU nanocomposites.</p> Full article ">
1213 KiB  
Article
A Bayesian Approach for Sensor Optimisation in Impact Identification
by Vincenzo Mallardo, Zahra Sharif Khodaei and Ferri M. H. Aliabadi
Materials 2016, 9(11), 946; https://doi.org/10.3390/ma9110946 - 22 Nov 2016
Cited by 31 | Viewed by 4743
Abstract
This paper presents a Bayesian approach for optimizing the position of sensors aimed at impact identification in composite structures under operational conditions. The uncertainty in the sensor data has been represented by statistical distributions of the recorded signals. An optimisation strategy based on [...] Read more.
This paper presents a Bayesian approach for optimizing the position of sensors aimed at impact identification in composite structures under operational conditions. The uncertainty in the sensor data has been represented by statistical distributions of the recorded signals. An optimisation strategy based on the genetic algorithm is proposed to find the best sensor combination aimed at locating impacts on composite structures. A Bayesian-based objective function is adopted in the optimisation procedure as an indicator of the performance of meta-models developed for different sensor combinations to locate various impact events. To represent a real structure under operational load and to increase the reliability of the Structural Health Monitoring (SHM) system, the probability of malfunctioning sensors is included in the optimisation. The reliability and the robustness of the procedure is tested with experimental and numerical examples. Finally, the proposed optimisation algorithm is applied to a composite stiffened panel for both the uniform and non-uniform probability of impact occurrence. Full article
(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)
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<p>Composite panel subjected to the experimental tests. Top view (<b>a</b>); and bottom view with sensors (<b>b</b>).</p> Full article ">Figure 2
<p>Fitness function <math display="inline"> <semantics> <mrow> <mi>J</mi> <mo>(</mo> <msub> <mi>e</mi> <mi>T</mi> </msub> <mo>)</mo> </mrow> </semantics> </math> (given by Equation (<a href="#FD7-materials-09-00946" class="html-disp-formula">7</a>)) distribution for all the possible four-sensor combinations. <math display="inline"> <semantics> <mrow> <mi>J</mi> <msub> <mrow> <mo>(</mo> <msub> <mi>e</mi> <mi>T</mi> </msub> <mo>)</mo> </mrow> <mrow> <mi>b</mi> <mi>e</mi> <mi>s</mi> <mi>t</mi> </mrow> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>33</mn> <mo>⇒</mo> <mi>P</mi> <mi>o</mi> <mi>D</mi> <mo>=</mo> <mn>67</mn> <mo>%</mo> </mrow> </semantics> </math>.</p> Full article ">Figure 3
<p>The 2045 × 1070 mm<math display="inline"> <semantics> <msup> <mrow/> <mn>2</mn> </msup> </semantics> </math> stiffened panel with all possible sensor locations.</p> Full article ">Figure 4
<p>(<b>a</b>) Main panel with the one-sixth portion extraction; (<b>b</b>) one-sixth portion with eight possible sensor locations.</p> Full article ">Figure 5
<p>Sensor locations for the section of the panel. The quotes are expressed in millimiters.</p> Full article ">Figure 6
<p>Performance of four-, six- and eight-sensor combinations for increasing sensor malfunctioning <math display="inline"> <semantics> <msub> <mi>M</mi> <mi>s</mi> </msub> </semantics> </math> in the panel represented in <a href="#materials-09-00946-f004" class="html-fig">Figure 4</a>. <math display="inline"> <semantics> <mrow> <msub> <mi>P</mi> <mrow> <mi>s</mi> <mi>d</mi> </mrow> </msub> <mo>=</mo> <mn>5</mn> <mo>%</mo> <mi>μ</mi> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <msub> <mi>e</mi> <mi>T</mi> </msub> <mo>=</mo> <mn>30</mn> </mrow> </semantics> </math> mm.</p> Full article ">Figure 7
<p>Stiffened panel with forty-five possible sensor locations.</p> Full article ">Figure 8
<p>Non-uniform prior probability <math display="inline"> <semantics> <mrow> <mi>p</mi> <mo>(</mo> <mi mathvariant="bold">x</mi> <mo>)</mo> </mrow> </semantics> </math> considered in the example depicted in <a href="#materials-09-00946-f009" class="html-fig">Figure 9</a>(b). <span class="html-italic">x</span>- and <span class="html-italic">y</span>- coordinates in millimeters.</p> Full article ">Figure 9
<p>Best four-sensor combination. Uniform probability (<b>a</b>); non-uniform probability (<b>b</b>).</p> Full article ">Figure 10
<p>Best five-sensor combinations. Sensors with the same color belong to the same combination.</p> Full article ">Figure 11
<p>Performance of four-, five- and six-sensor combinations for increasing sensor malfunctioning <math display="inline"> <semantics> <msub> <mi>M</mi> <mi>s</mi> </msub> </semantics> </math> in the panel represented in <a href="#materials-09-00946-f007" class="html-fig">Figure 7</a>. <math display="inline"> <semantics> <mrow> <msub> <mi>P</mi> <mrow> <mi>s</mi> <mi>d</mi> </mrow> </msub> <mo>=</mo> <mn>10</mn> <mo>%</mo> <mi>μ</mi> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <msub> <mi>e</mi> <mi>T</mi> </msub> <mo>=</mo> <mn>20</mn> </mrow> </semantics> </math> mm.</p> Full article ">
6222 KiB  
Article
The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT)
by Christoph Slouka, Theresa Kainz, Edvinas Navickas, Gregor Walch, Herbert Hutter, Klaus Reichmann and Jürgen Fleig
Materials 2016, 9(11), 945; https://doi.org/10.3390/ma9110945 - 22 Nov 2016
Cited by 66 | Viewed by 8556
Abstract
The different properties of acceptor-doped (hard) and donor-doped (soft) lead zirconate titanate (PZT) ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly [...] Read more.
The different properties of acceptor-doped (hard) and donor-doped (soft) lead zirconate titanate (PZT) ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La3+ donor-doped, Fe3+ acceptor-doped and La3+/Fe3+-co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Depth profiles of five differently doped lead zirconate titanate (PZT) samples in linear plots after tracer diffusion (30 min) at 560 °C; (<b>b</b>) logarithmic plots of the same profiles; (<b>c</b>,<b>d</b>) depth profiles of tracer exchange experiments at 715 °C (30 min) in linear plots (<b>c</b>) and logarithmic plots (<b>d</b>); (<b>e</b>) cross-sectional measurements after the tracer exchange experiments at 715 °C in linear plots; (<b>f</b>) cross-sectional profiles for 715 °C in logarithmic plots with fit curves (Equation (2)) for 0.5% and 1% Fe-doped samples.</p> Full article ">Figure 2
<p>Tracer distribution images of differently doped PZT after diffusion at 715 °C with clear indication of fast grain boundary diffusion in the donor doped samples; <sup>18</sup>O tracer fractions are shown.</p> Full article ">Figure 3
<p>(<b>a</b>) Tracer depth profile of 1.5% La-doped PZT at 715 °C with fit according to Equation (2). A clear grain boundary contribution is indicated by the diffusion tail. (<b>b</b>) Tracer depth profile of 1% Fe-doped PZT at 715 °C with fits according to Equation (2) in the near surface regime and in the region in some depth (beyond SCL = space charge layer); (<b>c</b>) tracer depth profile of 0.5% La-doped PZT at 560 °C with fit according to Equation (2); (<b>d</b>) tracer depth profile of 1% Fe-doped PZT at 560 °C with fits according to Equation (2) in the near surface regime and in the region in some depth (beyond SCL).</p> Full article ">Figure 4
<p>Bulk diffusion coefficients of the five analysed sample compositions. Negative dopant concentrations refer to donor dopant (La), positive to acceptor dopant (Fe).</p> Full article ">Figure 5
<p>Tracer depth profiles in 1% Fe-doped PZT measured after 30 min tracer diffusion at 560 °C. The circles represent the data after integration over the entire region shown in the tracer distribution image (see insets, <span class="html-italic">f</span>(<sup>18</sup>O)). Profiles obtained for small regions of interest (ROIs) within single grains (indicated in the SE inset image) lead to the same profiles.</p> Full article ">Figure 6
<p>(<b>a</b>) Impedance spectrum of the 1.5% La-doped PZT at 560 °C—an almost ideal semicircle results; (<b>b</b>) impedance spectrum of the undoped sample at 560 °C; the semicircle is more distorted; (<b>c</b>) impedance spectrum of the 1% Fe-doped PZT at 560 °C. A splitting into two semicircles is visible. The absolute resistance values of the three spectra differ by two orders of magnitude.</p> Full article ">Figure 7
<p>Partial pressure dependence of impedance spectra of 1% Fe-doped (<b>a</b>) and 1.5% La-doped (<b>b</b>) samples at 560 °C. Both show characteristics of hole conducting material, having a higher resistance for lower oxygen partial pressure.</p> Full article ">Figure 8
<p>Bulk conductivity values of differently doped PZT at 560 °C in ambient air; negative dopant concentrations refer to donor dopant (La), positive to acceptor dopant (Fe).</p> Full article ">Figure 9
<p>SEM images of co-doped samples, (<b>a</b>) 2% Fe/1.5% La; (<b>b</b>) 6.5% Fe/6% La; (<b>c</b>) 7% Fe/6% La.</p> Full article ">Figure 10
<p>(<b>a</b>) Tracer depth profiles after diffusion at 560 °C for all Fe- and Fe/La-doped samples; (<b>b</b>) tracer depth profiles of 6.5% Fe/6% La with a region of interest (ROI) integrated over a larger area and ROIs situated within single grains (see SE inset), respectively. The second inset displays the lateral tracer distribution.</p> Full article ">Figure 11
<p>(<b>a</b>) Bulk diffusion coefficients of PZT at 560 °C with effective acceptor concentrations of 0.5% and 1%, drawn as function of the La content; (<b>b</b>) summary of all bulk diffusion coefficients and hole conductivities in ambient air, measured at 560 °C. For co-doped and acceptor doped samples the abscissa indicates the Fe content.</p> Full article ">Figure 12
<p>Impedance spectra of PZT with 2% Fe/1.5% La and 6.5% Fe/6% La, measured in ambient air at 560 °C.</p> Full article ">Figure 13
<p>(<b>a</b>) <span class="html-italic">P–E</span> curves of different PZT samples (see legend). La-doped samples develop slim <span class="html-italic">P–E</span> curves with increased polarization. Fe-doped samples develop inclined <span class="html-italic">P–E</span> curves with reduced maximum polarization; (<b>b</b>) <span class="html-italic">P–E</span> curves of a sample doped with 0.5 mol % Fe measured for different maximum electric fields (see legend). Pinching of the <span class="html-italic">P–E</span> curve at low field amplitude indicates domain wall pinning, which is typical for acceptor-doped samples; (<b>c</b>) <span class="html-italic">P–E</span> curves of a sample doped with 6 mol % La and 6.5 mol % Fe measured for different maximum electric fields (see legend). Again the pinching of the <span class="html-italic">P–E</span> curves at low field amplitude indicates net acceptor doping of the sample.</p> Full article ">Figure 14
<p>Concentrations of oxygen vacancies and holes for different acceptor concentrations. All concentrations are normalized to a formula unit (concentration of ABO<sub>3</sub> cell = C<sub>0</sub>) and calculated from Equation (13) with <math display="inline"> <semantics> <mrow> <msub> <mi>C</mi> <mrow> <mi mathvariant="normal">T</mi> <mo>,</mo> <mi>tot</mi> </mrow> </msub> <mo>/</mo> <msub> <mi>C</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>0.56</mn> <mo>×</mo> <msup> <mrow> <mn>10</mn> </mrow> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> <mo>,</mo> <msub> <mi>K</mi> <mi mathvariant="normal">T</mi> </msub> <mo>=</mo> <mn>0.8</mn> <mo>×</mo> <msup> <mrow> <mn>10</mn> </mrow> <mrow> <mn>11</mn> </mrow> </msup> <mo>×</mo> <msup> <mrow> <mrow> <mo>(</mo> <mrow> <msub> <mi>C</mi> <mn>0</mn> </msub> </mrow> <mo>)</mo> </mrow> </mrow> <mn>2</mn> </msup> <mo>,</mo> <msubsup> <mi>K</mi> <mi mathvariant="sans-serif">δ</mi> <mo>′</mo> </msubsup> <mo>=</mo> <mn>1</mn> <mo>×</mo> <msup> <mrow> <mn>10</mn> </mrow> <mn>5</mn> </msup> <mo>×</mo> <msub> <mi>C</mi> <mn>0</mn> </msub> </mrow> </semantics> </math>.</p> Full article ">
9840 KiB  
Article
Protein-Mediated Precipitation of Calcium Carbonate
by Izabela Polowczyk, Anna Bastrzyk and Marta Fiedot
Materials 2016, 9(11), 944; https://doi.org/10.3390/ma9110944 - 22 Nov 2016
Cited by 48 | Viewed by 7047
Abstract
Calcium carbonate is an important component in exoskeletons of many organisms. The synthesis of calcium carbonate was performed by mixing dimethyl carbonate and an aqueous solution of calcium chloride dihydrate. The precipitation product was characterized by means of scanning electron microscopy (SEM), transmission [...] Read more.
Calcium carbonate is an important component in exoskeletons of many organisms. The synthesis of calcium carbonate was performed by mixing dimethyl carbonate and an aqueous solution of calcium chloride dihydrate. The precipitation product was characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) measurements. In addition, the turbidity of the reaction solution was acquired to monitor the kinetics of the calcium carbonate structure’s growth in the investigated system. In this study, samples of CaCO3 particles obtained with individual proteins, such as ovalbumin, lysozyme, and a mixture of the proteins, were characterized and compared with a control sample, i.e., synthesized without proteins. The obtained data indicated that the addition of ovalbumin to the reaction changed the morphology of crystals from rhombohedral to ‘stack-like’ structures. Lysozyme, however, did not affect the morphology of calcium carbonate, yet the presence of the protein mixture led to the creation of more complex composites in which the calcium carbonate crystals were constructed in protein matrices formed by the ovalbumin-lysozyme interaction. It was also observed that in the protein mixture, ovalbumin has a major influence on the CaCO3 formation through a strong interaction with calcium ions, which leads to the coalescence and creation of a steric barrier reducing particle growth. The authors proposed a mechanism of calcium carbonate grain growth in the presence of both proteins, taking into account the interaction of calcium ions with the protein. Full article
(This article belongs to the Section Biomaterials)
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<p>Transmission curves observed during precipitation of calcium carbonates.</p> Full article ">Figure 2
<p>SEM images of CaCO<sub>3</sub> obtained in the presence of: (<b>a</b>) no protein; (<b>b</b>) ovalbumin; (<b>c</b>) lysozyme; and (<b>d</b>) mixture of proteins.</p> Full article ">Figure 3
<p>Micrograph of organic-inorganic agglomerates obtained in the presence of a protein mixture (0.1% of albumin and lysozyme, 24 h).</p> Full article ">Figure 4
<p>TEM image of CaCO<sub>3</sub> precipitated without protein, after 1 min.</p> Full article ">Figure 5
<p>XRD diffraction patterns of the crystal structure of the calcium carbonates precipitated in the absence and in the presence of proteins (0.1%).</p> Full article ">Figure 6
<p>Interplanar spacing d of CaCO<sub>3</sub> samples after 10 min and 24 h. Protein concentration—0.1%.</p> Full article ">Figure 7
<p>The W-H analysis of CaCO<sub>3</sub> precipitated with lysozyme (0.1%) after 10 min.</p> Full article ">Figure 8
<p>Changes in: (<b>a</b>) crystallite size; (<b>b</b>) microstrains. Protein concentration: 0.1%.</p> Full article ">Figure 9
<p>FTIR spectra of the calcium carbonate crystals obtained in the absence and in the presence of proteins (0.1%, after 10 min).</p> Full article ">Figure 10
<p>Mechanisms of calcium carbonate crystal growth: (<b>a</b>) attachment of new ions to the existing crystallite; (<b>b</b>) Ostwald’s recrystallization; and (<b>c</b>) coalescence.</p> Full article ">Figure 11
<p>Scheme of the process of calcium carbonate formation in the presence of ovalbumin.</p> Full article ">
2671 KiB  
Article
Targeted Magnetic Nanoparticles for Mechanical Lysis of Tumor Cells by Low-Amplitude Alternating Magnetic Field
by Adi Vegerhof, Eran A. Barnoy, Menachem Motiei, Dror Malka, Yossef Danan, Zeev Zalevsky and Rachela Popovtzer
Materials 2016, 9(11), 943; https://doi.org/10.3390/ma9110943 - 22 Nov 2016
Cited by 22 | Viewed by 6787
Abstract
Currently available cancer therapies can cause damage to healthy tissue. We developed a unique method for specific mechanical lysis of cancer cells using superparamagnetic iron oxide nanoparticle rotation under a weak alternating magnetic field. Iron oxide core nanoparticles were coated with cetuximab, an [...] Read more.
Currently available cancer therapies can cause damage to healthy tissue. We developed a unique method for specific mechanical lysis of cancer cells using superparamagnetic iron oxide nanoparticle rotation under a weak alternating magnetic field. Iron oxide core nanoparticles were coated with cetuximab, an anti-epidermal growth factor receptor antibody, for specific tumor targeting. Nude mice bearing a head and neck tumor were treated with cetuximab-coated magnetic nanoparticles (MNPs) and then received a 30 min treatment with a weak external alternating magnetic field (4 Hz) applied on alternating days (total of seven treatments, over 14 days). This treatment, compared to a pure antibody, exhibited a superior cell death effect over time. Furthermore, necrosis in the tumor site was detected by magnetic resonance (MR) images. Thermal camera images of head and neck squamous cell carcinoma cultures demonstrated that cell death occurred purely by a mechanical mechanism. Full article
(This article belongs to the Special Issue Nanoprobes for Imaging)
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<p>Schematic design of the experimental setup.</p> Full article ">Figure 2
<p>Cell viability of 10<sup>6</sup> A431 cell cultures after various treatments. (<b>a</b>) Untreated cells; (<b>b</b>) cells without magnetic nanoparticles (MNPs) treated with 15 min of alternating magnetic fields (AMFs); (<b>c</b>) cells incubated with MNPs without AMFs; (<b>d</b>) cells incubated with MNPs and treated with 15 min of AMFs; (<b>e</b>) cells with MNPs heated for 5 min on a hot plate. Imaged by Leica microscope X20.</p> Full article ">Figure 3
<p>Thermal profile for (<b>a</b>) 10<sup>6</sup> A431 cells only; (<b>b</b>) solution of coated MNPs immediately after 15 min of AMF treatment; (<b>c</b>) 10<sup>6</sup> A431 cells after 15 min of AMF treatment; (<b>d</b>) 10<sup>6</sup> A431 cells incubated with coated MNPs after 15 min of AMF treatment; (<b>e</b>) 10<sup>6</sup> A431 cells with coated MNPs after 40 min of AMF treatment and (<b>f</b>) 10<sup>6</sup> A431 cells after 5 min on a hot plate set to 45 °C. Images taken by thermal imaging camera.</p> Full article ">Figure 4
<p>Number of cells in a 1 mL solution after AMF treatment for 5 min (<b>a</b>) with different particle concentrations (2 mg/mL–10 mg/mL); (<b>b</b>) The number of live cells in a sample with 10 mg/mL particles over a 5 min treatment.</p> Full article ">Figure 5
<p>Axial contrast-enhanced axial T2-weighted MRI slices of a head and neck tumor in a representative mouse from each MNP size group, after three cycles of 30 min AMF treatments given on alternating days: (<b>a</b>) a mouse with 50 nm coated MNPs; (<b>b</b>) a mouse with 100 nm coated MNPs; and (<b>c</b>) a mouse with 200 nm coated MNPs. The yellow arrows indicate the tumor sites. Measurements were performed in 3 slices for each mouse (with 8.5 signal averages per position to improve signal-to-noise ratio) resulting in a total data acquisition time of 10 minutes. All MRI slices were 1.0 mm thick with a 0.15 mm in-plane resolution.</p> Full article ">Figure 6
<p>Percentage of tumor volume growth for each AMF treatment in mice injected with 50, 100, and 200 nm coated MNPs, as well as cetuximab alone. <span class="html-italic">N</span> = 5 for the MNP groups and <span class="html-italic">n</span> = 4 for controls at each time point.</p> Full article ">
2369 KiB  
Article
Experimental and Theoretical Analysis of Sound Absorption Properties of Finely Perforated Wooden Panels
by Boqi Song, Limin Peng, Feng Fu, Meihong Liu and Houjiang Zhang
Materials 2016, 9(11), 942; https://doi.org/10.3390/ma9110942 - 22 Nov 2016
Cited by 23 | Viewed by 5585
Abstract
Perforated wooden panels are typically utilized as a resonant sound absorbing material in indoor noise control. In this paper, the absorption properties of wooden panels perforated with tiny holes of 1–3 mm diameter were studied both experimentally and theoretically. The Maa-MPP (micro perforated [...] Read more.
Perforated wooden panels are typically utilized as a resonant sound absorbing material in indoor noise control. In this paper, the absorption properties of wooden panels perforated with tiny holes of 1–3 mm diameter were studied both experimentally and theoretically. The Maa-MPP (micro perforated panels) model and the Maa-Flex model were applied to predict the absorption regularities of finely perforated wooden panels. A relative impedance comparison and full-factorial experiments were carried out to verify the feasibility of the theoretical models. The results showed that the Maa-Flex model obtained good agreement with measured results. Control experiments and measurements of dynamic mechanical properties were carried out to investigate the influence of the wood characteristics. In this study, absorption properties were enhanced by sound-induced vibration. The relationship between the dynamic mechanical properties and the panel mass-spring vibration absorption was revealed. While the absorption effects of wood porous structure were not found, they were demonstrated theoretically by using acoustic wave propagation in a simplified circular pipe with a suddenly changed cross-section model. This work provides experimental and theoretical guidance for perforation parameter design. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Mechanical property analyzer for thin wood composites.</p> Full article ">Figure 2
<p>Magnitudes of the relative acoustic resistance (<b>dotted lines</b>) and reactance (<b>solid lines</b>).</p> Full article ">Figure 3
<p>Experimental and theoretical sound absorption coefficients for perforated panels with 8 mm hole spacing.</p> Full article ">Figure 4
<p>Experimental and theoretical sound absorption coefficients for perforated panels with 10 mm hole spacing.</p> Full article ">Figure 5
<p>Measured and calculated relative impedance for finely perforated wooden panels.</p> Full article ">Figure 6
<p>Sound absorption coefficients of uncoated and coated perforated panels on tangential and cross sections.</p> Full article ">Figure 7
<p>Simplified model of wooden perforation with suddenly-changed cross-section.</p> Full article ">Figure 8
<p>Sound absorption coefficients for unperforated panel and perforated panels with different perforation rates.</p> Full article ">Figure 9
<p>Sound absorption coefficients of perforated panels of different wood species.</p> Full article ">
6996 KiB  
Article
Laboratory Testing of Silica Sol Grout in Coal Measure Mudstones
by Dongjiang Pan, Nong Zhang, Zhengzheng Xie, Xiaowei Feng and Yong Kong
Materials 2016, 9(11), 940; https://doi.org/10.3390/ma9110940 - 22 Nov 2016
Cited by 15 | Viewed by 6419
Abstract
The effectiveness of silica sol grout on mudstones is reported in this paper. Using X-ray diffraction (XRD), the study investigates how the silica sol grout modifies mudstone mineralogy. Micropore sizes and mechanical properties of the mudstone before and after grouting with four different [...] Read more.
The effectiveness of silica sol grout on mudstones is reported in this paper. Using X-ray diffraction (XRD), the study investigates how the silica sol grout modifies mudstone mineralogy. Micropore sizes and mechanical properties of the mudstone before and after grouting with four different materials were determined with a surface area/porosity analyser and by uniaxial compression. Tests show that, after grouting, up to 50% of the mesopore volumes can be filled with grout, the dominant pore diameter decreases from 100 nm to 10 nm, and the sealing capacity is increased. Uniaxial compression tests of silica sol grouted samples shows that their elastic modulus is 21%–38% and their uniaxial compressive strength is 16%–54% of the non-grouted samples. Peak strain, however, is greater by 150%–270%. After grouting, the sample failure mode changes from brittle to ductile. This paper provides an experimental test of anti-seepage and strengthening properties of silica sol. Full article
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<p>Micropore size analysis. (<b>a</b>) Graph of pore volume vs. pressure showing Hg hysteresis and retention; and (<b>b</b>) pore diameter distribution.</p> Full article ">Figure 2
<p>Adjustable gel time with varying catalyst dosage.</p> Full article ">Figure 3
<p>SEM backscattered electron image showing NaCl crystals distributed on the surface of hardened silica sol gel (aged 28 days). The scale bar in the lower right corner is 5 μm.</p> Full article ">Figure 4
<p>XRD results. (<b>a</b>) XRD scans showing peak positions and intensities for one untreated mudstone sample and four mudstone samples impregnated with different mixtures of silica sol grout; and (<b>b</b>) XRD test of the pure gel, the peak occurred at 20.9° or so (2-theta of quartz (100)) is too wide.</p> Full article ">Figure 5
<p>Laboratory-scale grouting system. (<b>a</b>) Grouting system; and (<b>b</b>) detail of mould assembly.</p> Full article ">Figure 6
<p>Mesopore analysis of samples before and after grouting with four different grouts. (<b>a</b>) Before and after grouting with P.O 425R; (<b>b</b>) before and after grouting with MP364; (<b>c</b>) before and after grouting with silica sol S/C = 6:1; (<b>d</b>) before and after grouting with silica sol S/C = 4:1.</p> Full article ">Figure 6 Cont.
<p>Mesopore analysis of samples before and after grouting with four different grouts. (<b>a</b>) Before and after grouting with P.O 425R; (<b>b</b>) before and after grouting with MP364; (<b>c</b>) before and after grouting with silica sol S/C = 6:1; (<b>d</b>) before and after grouting with silica sol S/C = 4:1.</p> Full article ">Figure 7
<p>Change curves of temperature and relative humidity in the curing box.</p> Full article ">Figure 8
<p>Flow chart for the uniaxial compression tests for mechanical properties.</p> Full article ">Figure 9
<p>Uniaxial compression stress strain curves for samples before and after grout impregnation with five different grouts. The elastic modulus reflects the capacity of a sample to resist deformation. Uniaxial compressive strength (UCS) and peak strain both reflect the capacity of the sample to resist failure. Pre-peak absorption strain energy (PASE) [<a href="#B18-materials-09-00940" class="html-bibr">18</a>] is the energy that causes sudden failure of a rock. (<b>a</b>) Grouting with P.O 425R W/C = 0.7; (<b>b</b>) Grouting with MP364 R/C = 1:1; (<b>c</b>) Grouting with silica sol S/C = 1:0; (<b>d</b>) Grouting with silica sol S/C = 6:1; (<b>e</b>) Grouting with silica sol S/C = 4:1.</p> Full article ">
12959 KiB  
Article
Efficient Solar-Induced Photoelectrochemical Response Using Coupling Semiconductor TiO2-ZnO Nanorod Film
by Nur Azimah Abd Samad, Chin Wei Lai, Kung Shiuh Lau and Sharifah Bee Abd Hamid
Materials 2016, 9(11), 937; https://doi.org/10.3390/ma9110937 - 22 Nov 2016
Cited by 15 | Viewed by 6614
Abstract
Efficient solar driven photoelectrochemical (PEC) response by enhancing charge separation has attracted great interest in the hydrogen generation application. The formation of one-dimensional ZnO nanorod structure without bundling is essential for high efficiency in PEC response. In this present research work, ZnO nanorod [...] Read more.
Efficient solar driven photoelectrochemical (PEC) response by enhancing charge separation has attracted great interest in the hydrogen generation application. The formation of one-dimensional ZnO nanorod structure without bundling is essential for high efficiency in PEC response. In this present research work, ZnO nanorod with an average 500 nm in length and average diameter of about 75 nm was successfully formed via electrodeposition method in 0.05 mM ZnCl2 and 0.1 M KCl electrolyte at 1 V for 60 min under 70 °C condition. Continuous efforts have been exerted to further improve the solar driven PEC response by incorporating an optimum content of TiO2 into ZnO nanorod using dip-coating technique. It was found that 0.25 at % of TiO2 loaded on ZnO nanorod film demonstrated a maximum photocurrent density of 19.78 mA/cm2 (with V vs. Ag/AgCl) under UV illumination and 14.75 mA/cm2 (with V vs. Ag/AgCl) under solar illumination with photoconversion efficiency ~2.9% (UV illumination) and ~4.3% (solar illumination). This performance was approximately 3–4 times higher than ZnO film itself. An enhancement of photocurrent density and photoconversion efficiency occurred due to the sufficient Ti element within TiO2-ZnO nanorod film, which acted as an effective mediator to trap the photo-induced electrons and minimize the recombination of charge carriers. Besides, phenomenon of charge-separation effect at type-II band alignment of Zn and Ti could further enhance the charge carrier transportation during illumination. Full article
(This article belongs to the Special Issue Thin-Film Deposition, Characterization and Advanced Surface Engineering)
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<p>FESEM images with 100 k magnification: (<b>a</b>) ZnO; (<b>b</b>) 0.25 at % TiO<sub>2</sub>-ZnO; (<b>c</b>) 0.50 at % TiO<sub>2</sub>-ZnO; and (<b>d</b>) 1.0 at % TiO<sub>2</sub>-ZnO; (<b>e</b>) HRTEM image for TiO<sub>2</sub>-ZnO.</p> Full article ">Figure 1 Cont.
<p>FESEM images with 100 k magnification: (<b>a</b>) ZnO; (<b>b</b>) 0.25 at % TiO<sub>2</sub>-ZnO; (<b>c</b>) 0.50 at % TiO<sub>2</sub>-ZnO; and (<b>d</b>) 1.0 at % TiO<sub>2</sub>-ZnO; (<b>e</b>) HRTEM image for TiO<sub>2</sub>-ZnO.</p> Full article ">Figure 2
<p>The schematic diagram of dip-coating method for the formation of TiO<sub>2</sub> loaded-ZnO: (<b>a</b>) ZnO nanorods; (<b>b</b>) dip-coating process; and (<b>c</b>) TiO<sub>2</sub> loaded-ZnO and followed by calcination process at 400 °C.</p> Full article ">Figure 3
<p>XRD pattern of (<b>a</b>) ZnO; (<b>b</b>) 0.25 at % TiO<sub>2</sub>-ZnO; (<b>c</b>) 0.50 at % TiO<sub>2</sub>-ZnO; and (<b>d</b>) 1.0 at % TiO<sub>2</sub>-ZnO.</p> Full article ">Figure 4
<p>Raman scattering of ZnO, 0.25 at % TiO<sub>2</sub>-ZnO, 0.5 at % TiO<sub>2</sub>-ZnO, and 1.0 at % TiO<sub>2</sub>-ZnO.</p> Full article ">Figure 5
<p>Full XPS survey spectra of ZnO, 0.25 at % TiO<sub>2</sub>-ZnO, and 1.0 at % TiO<sub>2</sub>-ZnO.</p> Full article ">Figure 6
<p>XPS spectra Zn2p of ZnO, 0.25 at % TiO<sub>2</sub>-ZnO, and 1.0 at % TiO<sub>2</sub>-ZnO.</p> Full article ">Figure 7
<p>XPS spectra O1s of TiO<sub>2</sub>, 0.25 at % TiO<sub>2</sub>-ZnO, 1.0 at % TiO<sub>2</sub>-ZnO, and ZnO.</p> Full article ">Figure 8
<p>XPS spectra Ti2p of TiO<sub>2</sub>, 0.25 at % TiO<sub>2</sub>-ZnO, and 1.0 at % TiO<sub>2</sub>-ZnO.</p> Full article ">Figure 9
<p>PL spectra of ZnO, 0.25 at % TiO<sub>2</sub>-ZnO, 0.50 at % TiO<sub>2</sub>-ZnO, and 1.0 at % TiO<sub>2</sub>-ZnO (excitation: λ = 514 nm).</p> Full article ">Figure 10
<p>Photocurrent response of (<b>a</b>) ZnO; (<b>b</b>) 0.25% TiO<sub>2</sub>-ZnO; (<b>c</b>) 0.50 at % TiO<sub>2</sub>-ZnO; and (<b>d</b>) 1.0 at % TiO<sub>2</sub>-ZnO under UV illumination.</p> Full article ">Figure 11
<p>Photocurrent response of (<b>a</b>) ZnO; (<b>b</b>) 0.25 at % TiO<sub>2</sub>-ZnO; (<b>c</b>) 0.50 at % TiO<sub>2</sub>-ZnO; and (<b>d</b>) 1.0 at % TiO<sub>2</sub>-ZnO under solar illumination.</p> Full article ">Figure 12
<p>Photocurrent response for combination of all samples with respect to UV ray (300 nm) and solar illumination.</p> Full article ">Figure 13
<p>Photoconversion efficiency of (<b>a</b>) ZnO; (<b>b</b>) 0.25 at % TiO<sub>2</sub>-ZnO; (<b>c</b>) 0.50 at % TiO<sub>2</sub>-ZnO; and (<b>d</b>) 1.0 at % TiO<sub>2</sub>-ZnO under UV illumination.</p> Full article ">Figure 14
<p>Photoconversion efficiency of (<b>a</b>) ZnO; (<b>b</b>) 0.25 at % TiO<sub>2</sub>-ZnO; (<b>c</b>) 0.50 at % TiO<sub>2</sub>-ZnO; and (<b>d</b>) 1.0 at % TiO<sub>2</sub>-ZnO under solar illumination.</p> Full article ">Figure 15
<p>Reflectance spectra of ZnO, 0.25 at % TiO<sub>2</sub>-ZnO, 0.50 at % TiO<sub>2</sub>-ZnO, and 1.0 at % TiO<sub>2</sub>-ZnO.</p> Full article ">Figure 16
<p>Tauc plot of ZnO, 0.25 at % TiO<sub>2</sub>-ZnO, 0.50 at % TiO<sub>2</sub>-ZnO, and 1.0 at % TiO<sub>2</sub>-ZnO.</p> Full article ">Figure 17
<p>Illustration of staggered bandgap (type II) TiO<sub>2</sub> loaded on ZnO nanorod semiconductor and its photo-induced charge transfer and separation.</p> Full article ">
6070 KiB  
Article
Numerical Approach to Modeling and Characterization of Refractive Index Changes for a Long-Period Fiber Grating Fabricated by Femtosecond Laser
by Akram Saad, Yonghyun Cho, Farid Ahmed and Martin Byung-Guk Jun
Materials 2016, 9(11), 941; https://doi.org/10.3390/ma9110941 - 21 Nov 2016
Cited by 3 | Viewed by 6061
Abstract
A 3D finite element model constructed to predict the intensity-dependent refractive index profile induced by femtosecond laser radiation is presented. A fiber core irradiated by a pulsed laser is modeled as a cylinder subject to predefined boundary conditions using COMSOL5.2 Multiphysics commercial package. [...] Read more.
A 3D finite element model constructed to predict the intensity-dependent refractive index profile induced by femtosecond laser radiation is presented. A fiber core irradiated by a pulsed laser is modeled as a cylinder subject to predefined boundary conditions using COMSOL5.2 Multiphysics commercial package. The numerically obtained refractive index change is used to numerically design and experimentally fabricate long-period fiber grating (LPFG) in pure silica core single-mode fiber employing identical laser conditions. To reduce the high computational requirements, the beam envelope method approach is utilized in the aforementioned numerical models. The number of periods, grating length, and grating period considered in this work are numerically quantified. The numerically obtained spectral growth of the modeled LPFG seems to be consistent with the transmission of the experimentally fabricated LPFG single mode fiber. The sensing capabilities of the modeled LPFG are tested by varying the refractive index of the surrounding medium. The numerically obtained spectrum corresponding to the varied refractive index shows good agreement with the experimental findings. Full article
(This article belongs to the Special Issue Ultrafast Laser-Based Manufacturing)
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<p>Schematic illustration of long-period grating fabrication.</p> Full article ">Figure 2
<p>The numerical effective refractive index of the SMF.</p> Full article ">Figure 3
<p>Visualization of the light intensity in the cross section of the SMF; the core’s index is 1.4649.</p> Full article ">Figure 4
<p>Schematic illustration of the model geometry and boundary conditions.</p> Full article ">Figure 5
<p>(<b>a</b>) A multi-slice plot of the induced refractive index profile; (<b>b</b>) An isosurface plot illustrating specified contours of the induced refractive index.</p> Full article ">Figure 6
<p>Geometrical depiction of the numerically modeled single mode fiber.</p> Full article ">Figure 7
<p>Gradual growth of LPFG in the modeled single mode fiber for different number of periods using free triangular mesh.</p> Full article ">Figure 8
<p>Gradual growth of LPFG in the modeled single mode fiber for different number of periods using mapped mesh.</p> Full article ">Figure 9
<p>Schematic illustration of the experimental setup.</p> Full article ">Figure 10
<p>Gradual growth of LPFG in SMF fiber for different number of periods.</p> Full article ">Figure 11
<p>Transmission spectrum of an LPFG numerically modeled in SMF with various grating periods; the number of grating periods and the grating length are 42 and 100 μm respectively.</p> Full article ">Figure 12
<p>The numerically acquired spectrum for various grating lengths; the grating period is 435 μm. The numbers of periods in (<b>a</b>–<b>c</b>) are 15, 30, and 42 respectively.</p> Full article ">Figure 13
<p>The numerically obtained spectral growth as a function of medium refractive index.</p> Full article ">Figure 14
<p>Experimentally obtained shift of the transmission valley when the LPFG is exposed to solutions of different refractive indices.</p> Full article ">Figure 15
<p>Numerical vs. experimental refractive index characterization of an LPFG sensor.</p> Full article ">
5255 KiB  
Article
Effects of Acoustic Modulation and Mixed Fuel on Flame Synthesis of Carbon Nanomaterials in an Atmospheric Environment
by Wei-Chieh Hu, Shanti Kartika Sari, Shuhn-Shyurng Hou and Ta-Hui Lin
Materials 2016, 9(11), 939; https://doi.org/10.3390/ma9110939 - 18 Nov 2016
Cited by 7 | Viewed by 4530
Abstract
In this study, methane–ethylene jet diffusion flames modulated by acoustic excitation in an atmospheric environment were used to investigate the effects of acoustic excitation frequency and mixed fuel on nanomaterial formation. Acoustic output power was maintained at a constant value of 10 W, [...] Read more.
In this study, methane–ethylene jet diffusion flames modulated by acoustic excitation in an atmospheric environment were used to investigate the effects of acoustic excitation frequency and mixed fuel on nanomaterial formation. Acoustic output power was maintained at a constant value of 10 W, while the acoustic excitation frequency was varied (f = 0–90 Hz). The results show that the flame could not be stabilized on the port when the ethylene volume concentration (ΩE) was less than 40% at f = 10 Hz, or when ΩE = 0% (i.e., pure methane) at f = 90 Hz. The reason for this is that the flame had a low intensity and was extinguished by the entrained air due to acoustic modulation. Without acoustic excitation (f = 0 Hz), the flame was comprised of a single-layer structure for all values of ΩE, and almost no carbon nanomaterials were synthesized. However, with acoustic excitation, a double-layer flame structure was generated for frequencies close to both the natural flickering frequency and the acoustically resonant frequency. This double-layer flame structure provided a favorable flame environment for the fabrication of carbon nanomaterials. Consequently, the synthesis of carbon nano-onions was significantly enhanced by acoustic excitation near both the natural flickering frequency and the acoustically resonant frequency. At f = 20 Hz (near the natural flickering frequency) for 0% ≤ ΩE ≤ 100%, a quantity of carbon nano-onions (CNOs) piled like bunches of grapes was obtained as a result of improved mixing of the fuel with ambient air. High-density CNOs were also produced at f = 70 Hz (close to the acoustically resonant frequency) for 40% ≤ ΩE ≤ 100%. Furthermore, carbon nanotubes (CNTs) were synthesized only at 80 Hz for ΩE = 0%. The suitable temperature range for the synthesis of CNTs was slightly higher than that for the formation of CNOs (about 600 °C for CNTs; 510–600 °C for CNOs). Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2016)
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<p>Schematic of acoustically modulated jet flow system.</p> Full article ">Figure 2
<p>Effect of modulation frequency (<span class="html-italic">f</span>) and fuel concentration ratio (Ω<sub>E</sub>) on flame structure.</p> Full article ">Figure 3
<p>Variations of flame diameter at <span class="html-italic">z</span> = 10 mm with modulation frequency (<span class="html-italic">f</span>) and ethylene concentration (Ω<sub>E</sub>).</p> Full article ">Figure 4
<p>Mean temperatures (<span class="html-italic">T</span>) at <span class="html-italic">z</span> = 10 mm for various modulation frequencies (<span class="html-italic">f</span>) and ethylene concentrations (Ω<sub>E</sub>).</p> Full article ">Figure 5
<p>Scanning electron microscopy (SEM) images of carbon nanomaterials synthesized at <span class="html-italic">z</span> = 10 mm for various values of Ω<sub>E</sub> and <span class="html-italic">f</span>. ×: No CNMs; CNMs: carbon nanomaterials.</p> Full article ">Figure 6
<p>Typical transmission electron microscopy (TEM) images of carbon nanomaterials synthesized at <span class="html-italic">z</span> = 10 mm: (<b>a</b>) carbon nano-onion (CNO), and (<b>b</b>) carbon nanotube (CNT).</p> Full article ">Figure 7
<p>Variations of average diameters of synthesized carbon nanomaterials with Ω<sub>E</sub> for <span class="html-italic">f</span> = 20, 70 and 80 Hz at <span class="html-italic">P</span> = 10 W.</p> Full article ">
4961 KiB  
Article
Molecular Weight Cut-Off and Structural Analysis of Vacuum-Assisted Titania Membranes for Water Processing
by Siti Nurehan Abd Jalil, David K. Wang, Christelle Yacou, Julius Motuzas, Simon Smart and João C. Diniz da Costa
Materials 2016, 9(11), 938; https://doi.org/10.3390/ma9110938 - 18 Nov 2016
Cited by 6 | Viewed by 5983
Abstract
This work investigates the structural formation and analyses of titania membranes (TM) prepared using different vacuum exposure times for molecular weight (MW) cut-off performance and oil/water separation. Titania membranes were synthesized via a sol-gel method and coated on macroporous alumina tubes followed by [...] Read more.
This work investigates the structural formation and analyses of titania membranes (TM) prepared using different vacuum exposure times for molecular weight (MW) cut-off performance and oil/water separation. Titania membranes were synthesized via a sol-gel method and coated on macroporous alumina tubes followed by exposure to a vacuum between 30 and 1200 s and then calcined at 400 °C. X-ray diffraction and nitrogen adsorption analyses showed that the crystallite size and particle size of titania increased as a function of vacuum time. All the TM membranes were mesoporous with an average pore diameter of ~3.6 nm with an anatase crystal morphology. Water, glucose, sucrose, and polyvinylpyrrolidone with 40 and 360 kDa (PVP-40 kDa and PVP-360 kDa) were used as feed solutions for MW cut-off and hexadecane solution for oil filtration investigation. The TM membranes were not able to separate glucose and sucrose, thus indicating the membrane pore sizes are larger than the kinetic diameter of sucrose of 0.9 nm, irrespective of vacuum exposure time. They also showed only moderate rejection (20%) of the smaller PVP-40 kDa, however, all the membranes were able to obtain an excellent rejection of near 100% for the larger PVP-360 kDa molecule. Furthermore, the TM membranes were tested for the separation of oil emulsions with a high concentration of oil (3000 ppm), reaching high oil rejections of more than 90% of oil. In general, the water fluxes increased with the vacuum exposure time indicating a pore structural tailoring effect. It is therefore proposed that a mechanism of pore size tailoring was formed by an interconnected network of Ti–O–Ti nanoparticles with inter-particle voids, which increased as TiO2 nanoparticle size increased as a function of vacuum exposure time, and thus reduced the water transport resistance through the TM membranes. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
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<p>(<b>a</b>) Nitrogen adsorption isotherms (full symbols for adsorption and hollow symbols for desorption); (<b>b</b>) Brunner-Emmett-Teller (BET) surface area and pore volumes; and (<b>c</b>) pore size distribution of titania membranes (TM) xerogels exposed to varying vacuum times.</p> Full article ">Figure 1 Cont.
<p>(<b>a</b>) Nitrogen adsorption isotherms (full symbols for adsorption and hollow symbols for desorption); (<b>b</b>) Brunner-Emmett-Teller (BET) surface area and pore volumes; and (<b>c</b>) pore size distribution of titania membranes (TM) xerogels exposed to varying vacuum times.</p> Full article ">Figure 2
<p>X-ray diffraction (XRD) patterns of titania samples calcined at 400 °C and exposed to different vacuum times.</p> Full article ">Figure 3
<p>Scanning electron microscopy (SEM) of the cross-section of (<b>a</b>) alumina substrate and the TM1200 membranes for (<b>c</b>) one layer (<b>e</b>) two layers (<b>g</b>) three layers and their corresponding surface morphology of (<b>b</b>) alumina substrate (<b>d</b>) one layer (<b>f</b>) two layers and (<b>h</b>) three layers of TM1200 membranes.</p> Full article ">Figure 4
<p>Single layer TM membranes at different vacuum times (<b>a</b>) flux and (<b>b</b>) percentage of rejection as a function of molecular weight (MW) for TM0 (grey circles), TM30 (green inverted triangles), TM120 (red diamonds), TM600 (black triangles) and TM1200 (blue squares).</p> Full article ">Figure 4 Cont.
<p>Single layer TM membranes at different vacuum times (<b>a</b>) flux and (<b>b</b>) percentage of rejection as a function of molecular weight (MW) for TM0 (grey circles), TM30 (green inverted triangles), TM120 (red diamonds), TM600 (black triangles) and TM1200 (blue squares).</p> Full article ">Figure 5
<p>MW cut off performance of TM1200 membranes prepared with varying numbers of titania layers (<b>a</b>) flux and (<b>b</b>) percentage of rejection as a function of MW.</p> Full article ">Figure 5 Cont.
<p>MW cut off performance of TM1200 membranes prepared with varying numbers of titania layers (<b>a</b>) flux and (<b>b</b>) percentage of rejection as a function of MW.</p> Full article ">Figure 6
<p>Water flux of the TM1200 membranes as a function of the feed pressure and number of layers.</p> Full article ">Figure 7
<p>Water flux of the TM1200-1L, TM1200-2L, and TM1200-3L membranes tested with oil emulsion (3000 ppm of hexadecane) at 60 min of filtration.</p> Full article ">Figure 8
<p>Water flux for single layer titania membranes versus calculated titania particle diameter.</p> Full article ">Figure 9
<p>Schematic of the effect of the vacuum in the formation of titania films.</p> Full article ">Figure 10
<p>Schematic of the membrane experimental set up.</p> Full article ">
20975 KiB  
Article
Experimental Study on Reaction Characteristics of PTFE/Ti/W Energetic Materials under Explosive Loading
by Yan Li, Chunlan Jiang, Zaicheng Wang and Puguang Luo
Materials 2016, 9(11), 936; https://doi.org/10.3390/ma9110936 - 18 Nov 2016
Cited by 21 | Viewed by 6103
Abstract
Metal/fluoropolymer composites represent a new category of energetic structural materials that release energy through exothermic chemical reactions initiated under shock loading conditions. This paper describes an experiment designed to study the reaction characteristics of energetic materials with low porosity under explosive loading. Three [...] Read more.
Metal/fluoropolymer composites represent a new category of energetic structural materials that release energy through exothermic chemical reactions initiated under shock loading conditions. This paper describes an experiment designed to study the reaction characteristics of energetic materials with low porosity under explosive loading. Three PTFE (polytetrafluoroethylene)/Ti/W mixtures with different W contents are processed through pressing and sintering. An inert PTFE/W mixture without reactive Ti particles is also prepared to serve as a reference. Shock-induced chemical reactions are recorded by high-speed video through a narrow observation window. Related shock parameters are calculated based on experimental data, and differences in energy release are discussed. The results show that the reaction propagation of PTFE/Ti/W energetic materials with low porosity under explosive loading is not self-sustained. As propagation distance increases, the energy release gradually decreases. In addition, reaction failure distance in PTFE/Ti/W composites is inversely proportional to the W content. Porosity increased the failure distance due to higher shock temperature. Full article
(This article belongs to the Section Advanced Composites)
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<p>The temperature history of a sintering cycle.</p> Full article ">Figure 2
<p>Sintered PTFE (polytetrafluoroethylene)/Ti/W samples: (<b>a</b>) 98.8% TMD 68PTFE/32Ti; (<b>b</b>) 90.3% TMD 34PTFE/16Ti/50W; (<b>c</b>) 70.7% TMD 16PTFE/8Ti/76W; and (<b>d</b>) 96.7% TMD 45PTFE/55W. TMD: theoretical maximum density.</p> Full article ">Figure 3
<p>Backscattered scanning electron microscope (SEM) images of PTFE/Ti/W composites: (<b>a</b>,<b>b</b>) 98.8% TMD 68PTFE/32Ti; (<b>c</b>,<b>d</b>) 90.3% TMD 34PTFE/16Ti/50W; (<b>e</b>,<b>f</b>) 70.7% TMD 16PTFE/8Ti/76W; and (<b>g</b>,<b>h</b>) 96.7% TMD 45PTFE/55W.</p> Full article ">Figure 3 Cont.
<p>Backscattered scanning electron microscope (SEM) images of PTFE/Ti/W composites: (<b>a</b>,<b>b</b>) 98.8% TMD 68PTFE/32Ti; (<b>c</b>,<b>d</b>) 90.3% TMD 34PTFE/16Ti/50W; (<b>e</b>,<b>f</b>) 70.7% TMD 16PTFE/8Ti/76W; and (<b>g</b>,<b>h</b>) 96.7% TMD 45PTFE/55W.</p> Full article ">Figure 4
<p>Photograph of experimental steel body.</p> Full article ">Figure 5
<p>Schematic diagram of the experimental setup. TNT: trinitrotoluene.</p> Full article ">Figure 6
<p>Typical shock front signals (Test No. 5).</p> Full article ">Figure 7
<p>High-speed video sequences of partial tests. (<b>a</b>) Test No. 2; (<b>b</b>) Test No. 5; (<b>c</b>) Test No. 8; and (<b>d</b>) Test No. 10.</p> Full article ">Figure 8
<p>Schematic illustration of reaction propagation under explosive loading. The black profile represents the pulse shock wave propagating in the energetic materials. The arrow shows the propagation direction. The use of color within the idealized microstructure symbolizes the chemical reaction.</p> Full article ">Figure 9
<p>Residual sample and SEM micrographs of reaction surface after test No. 2. The arrow indicates the reaction surface.</p> Full article ">Figure 10
<p>Time–distance curves for shock wave propagation.</p> Full article ">Figure 11
<p>Velocity-distance curves for shock wave propagation.</p> Full article ">Figure 12
<p>Pressure–distance curves for shock wave propagation.</p> Full article ">Figure 13
<p>Temperature–distance curves for shock wave propagation.</p> Full article ">Figure 14
<p>Curve of reaction extent changing with temperature for PTFE/Ti.</p> Full article ">Figure 15
<p>Curves of energy release changing with distance.</p> Full article ">
2210 KiB  
Communication
Energy Storage Characteristics of BiFeO3/BaTiO3 Bi-Layers Integrated on Si
by Menglin Liu, Hanfei Zhu, Yunxiang Zhang, Caihong Xue and Jun Ouyang
Materials 2016, 9(11), 935; https://doi.org/10.3390/ma9110935 - 18 Nov 2016
Cited by 37 | Viewed by 6750
Abstract
BiFeO3/BaTiO3 bi-layer thick films (~1 μm) were deposited on Pt/Ti/SiO2/(100) Si substrates with LaNiO3 buffer layers at 500 °C via a rf magnetron sputtering process. X-ray diffraction (XRD) analysis revealed that both BiFeO3 and BaTiO3 [...] Read more.
BiFeO3/BaTiO3 bi-layer thick films (~1 μm) were deposited on Pt/Ti/SiO2/(100) Si substrates with LaNiO3 buffer layers at 500 °C via a rf magnetron sputtering process. X-ray diffraction (XRD) analysis revealed that both BiFeO3 and BaTiO3 layers have a (00l) preferred orientation. The films showed a small remnant polarization (Pr ~ 7.8 μC/cm2) and a large saturated polarization (Ps ~ 65 μC/cm2), resulting in a slim polarization-electric field (P-E) hysteresis loop with improved energy storage characteristics (Wc = 71 J/cm3, η = 61%). The successful “slim-down” of the P-E loop from that of the pure BiFeO3 film can be attributed to the competing effects of space charges and the interlayer charge coupling on charge transport of the bi-layer film. The accompanying electrical properties of the bi-layer films were measured and the results confirmed their good quality. Full article
(This article belongs to the Special Issue Microwave Absorbing and Energy Storage Materials)
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<p>Schematic of a ferroelectric <span class="html-italic">P-E</span> loop. The green area is the discharged energy density <span class="html-italic">W<sub>d</sub></span>, while the yellow area is the energy loss of one charge-discharge cycle (<span class="html-italic">W</span><sub>loss</sub>).</p> Full article ">Figure 2
<p>Schematics of the experimental procedures.</p> Full article ">Figure 3
<p>(<b>a</b>) XRD 2<span class="html-italic">θ</span> scan spectrum (R-rhombohedral, T- tetragonal for BFO peaks, while the BTO phase is tetragonal); (<b>b</b>) X-ray pole figure analyses by using the (001)<sub>R</sub> BFO peak; (<b>c</b>) AFM surface scan image (5 μm × 5 μm); and (<b>d</b>) cross-sectional SEM image of the BiFeO<sub>3</sub>/BaTiO<sub>3</sub> bi-layer film deposited on LaNiO<sub>3</sub>/Pt/Ti/SiO<sub>2</sub>/(100) Si substrate.</p> Full article ">Figure 4
<p>(<b>a</b>) Room temperature ferroelectric hysteresis loop of the BiFeO<sub>3</sub>/BaTiO<sub>3</sub> bi-layer film deposited on LaNiO<sub>3</sub>/Pt/Ti/SiO<sub>2</sub>/(100)Si substrate, the insets compare <span class="html-italic">P-E</span> loops of the pure BiFeO<sub>3</sub> and BaTiO<sub>3</sub> films with those of the bi-layer film measured under the same electric field [<a href="#B22-materials-09-00935" class="html-bibr">22</a>,<a href="#B23-materials-09-00935" class="html-bibr">23</a>]; (<b>b</b>) schematics of the ferroelectric bi-layer considered in our work; (<b>c</b>) the space charge effect dominant at a low electric field, ω is the depletion layer width under an electric field E; (<b>d</b>) strong interlayer charge coupling dominant at a high electric field (after the BaTiO<sub>3</sub> layer has been fully depleted).</p> Full article ">Figure 5
<p>(<b>a</b>) Leakage current density vs. voltage <span class="html-italic">(J-V</span>) curve; and (<b>b</b>) frequency dependent dielectric properties of the BiFeO<sub>3</sub>/BaTiO<sub>3</sub> bi-layer film.</p> Full article ">
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Article
Characterization and Bioactivity Evaluation of (Polyetheretherketone/Polyglycolicacid)-Hydroyapatite Scaffolds for Tissue Regeneration
by Cijun Shuai, Chenying Shuai, Ping Wu, Fulai Yuan, Pei Feng, Youwen Yang, Wang Guo, Xiaohan Fan, Ting Su, Shuping Peng and Chengde Gao
Materials 2016, 9(11), 934; https://doi.org/10.3390/ma9110934 - 18 Nov 2016
Cited by 29 | Viewed by 4946
Abstract
Bioactivity and biocompatibility are crucial for tissue engineering scaffolds. In this study, hydroxyapatite (HAP) was incorporated into polyetheretherketone/polyglycolicacid (PEEK/PGA) hybrid to improve its biological properties, and the composite scaffolds were developed via selective laser sintering (SLS). The effects of HAP on physical and [...] Read more.
Bioactivity and biocompatibility are crucial for tissue engineering scaffolds. In this study, hydroxyapatite (HAP) was incorporated into polyetheretherketone/polyglycolicacid (PEEK/PGA) hybrid to improve its biological properties, and the composite scaffolds were developed via selective laser sintering (SLS). The effects of HAP on physical and chemical properties of the composite scaffolds were investigated. The results demonstrated that HAP particles were distributed evenly in PEEK/PGA matrix when its content was no more than 10 wt %. Furthermore, the apatite-forming ability became better with increasing HAP content after immersing in simulated body fluid (SBF). Meanwhile, the composite scaffolds presented a greater degree of cell attachment and proliferation than PEEK/PGA scaffolds. These results highlighted the potential of (PEEK/PGA)-HAP scaffolds for tissue regeneration. Full article
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<p>(<b>a</b>) Top view; (<b>b</b>) isometric view; and (<b>c</b>) lateral view of the polyetheretherketone/ polyglycolicacid-hydroxyapatite (PEEK/PGA-HAP) composite scaffold.</p> Full article ">Figure 2
<p>Morphologies of the scaffolds with (<b>a</b>) 0 wt %; (<b>b</b>) 5 wt %; (<b>c</b>) 7.5 wt %; (<b>d</b>) 10 wt %; (<b>e</b>) 12.5 wt %; (<b>f</b>) 15 wt % HAP.</p> Full article ">Figure 3
<p>X-ray diffraction (XRD) patterns of (<b>a</b>) the HAP powder; (<b>b</b>) the PEEK/PGA scaffold; (<b>c</b>) the PEEK/PGA-5 wt % HAP scaffold; (<b>d</b>) the PEEK/PGA-7.5 wt % HAP scaffold; (<b>e</b>) the PEEK/PGA-10 wt % HAP scaffold; (<b>f</b>) the PEEK/PGA-12.5 wt % HAP scaffold and (<b>g</b>) the PEEK/PGA-15 wt %.</p> Full article ">Figure 4
<p>Differential scanning calorimetry (DSC) spectra of PEEK/PGA scaffold and PEEK/PGA-HAP composite scaffolds.</p> Full article ">Figure 5
<p>Elastic modulus, compressive strength and tensile strength of the scaffolds with different HAP contents.</p> Full article ">Figure 6
<p>Morphologies of the scaffolds with (<b>a</b>) 0 wt %; (<b>b</b>) 5 wt %; (<b>c</b>) 7.5 wt %; (<b>d</b>) 10 wt %; (<b>e</b>) 12.5 wt %; (<b>f</b>) 15 wt % HAP after immersion in simulated body fluid (SBF) for 14 days.</p> Full article ">Figure 7
<p>Fourier transform infrared spectrums of the scaffolds with 10 wt % HAP before and after immersing in SBF.</p> Full article ">Figure 8
<p>(<b>a</b>) pH value of the PEEK/PGA scaffold and PEEK/PGA-10 wt % HAP scaffold during in vitro degradation; (<b>b</b>) weight loss of the PEEK/PGA scaffold and PEEK/PGA-10 wt % HAP scaffold after immersing in PBS.</p> Full article ">Figure 9
<p>MTT assay of MG-63 cells cultured on PEEK/PGA scaffolds and PEEK/PGA-10 wt % HAP scaffolds (* <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 10
<p>Fluorescence images of MG63 cells cultured on PEEK/PGA and PEEK/PGA-10 wt % HAP scaffolds for different periods (letters <b>A</b> and <b>B</b> correspond to the two scaffolds. Subscripts indicate the time).</p> Full article ">Figure 11
<p>Alkaline phosphatase (ALP) activity of MG63 cells cultured on PEEK/PGA scaffolds and PEEK/PGA-10 wt % HAP scaffolds at various time points (* <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">
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Article
Studying the Hydration of a Retarded Suspension of Ground Granulated Blast-Furnace Slag after Reactivation
by Nick Schneider and Dietmar Stephan
Materials 2016, 9(11), 933; https://doi.org/10.3390/ma9110933 - 18 Nov 2016
Cited by 2 | Viewed by 4511
Abstract
This article presents a combined use of a retarder (d-gluconic acid) and an alkaline activator (sodium hydroxide) in a binder system based on ground granulated blast-furnace slag. The properties of the retarder are extending the dormant hydration period and suppressing the [...] Read more.
This article presents a combined use of a retarder (d-gluconic acid) and an alkaline activator (sodium hydroxide) in a binder system based on ground granulated blast-furnace slag. The properties of the retarder are extending the dormant hydration period and suppressing the generation of strength-giving phases. Different retarder concentrations between 0.25 and 1.00 wt.% regulate the intensity and the period of the retardation and also the characteristics of the strength development. The activator concentration of 30 and 50 wt.% regulates the overcoming of the dormant period and thereby the solution of the slag and hence the formation of the hydration products. The research objective is to produce a mineral binder system based on two separate liquid components. The highest concentration of retarder and activator generates the highest compressive strength and mass of hydration products—after 90 days of hydration a compressive strength of more than 50 N/mm2. The main phases are calcium silicate hydrate and hydrotalcite. Generally, the combination of retarder and activator shows a high potential in the performance increase of the hydration process. Full article
(This article belongs to the Section Advanced Composites)
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<p>Timescale of the retardation periods (0–28 days), the points of activation/reactivation (Ac1, Ac2) and the ages of the hydration (7–90 days).</p> Full article ">Figure 2
<p>Compressive strength after seven, 28 and 90 days of hydration with (<b>a</b>) Ac1 and (<b>b</b>) Ac2 of the references (without retarder) and the reactivated mixtures with NaOH after seven different periods of retardation of 0.25%, 0.50%, and 1.00%R (* average out of four instead of six samples).</p> Full article ">Figure 3
<p>Mass loss by TG of Ac1 after seven, 28 and 90 days (from left to right, per test) after the beginning of the hydration of the reference of Ac1 (without retarder) and the reactivated mixtures with NaOH after seven different periods of retardation with (<b>a</b>) 0.25%; (<b>b</b>) 0.50%; and (<b>c</b>) 1.00%R.</p> Full article ">Figure 4
<p>Mass loss by TG of Ac2 after seven, 28 and 90 days (from left to right per test) after the beginning of the hydration of the reference of Ac2 (without retarder) and the reactivated mixtures with NaOH after seven different periods of retardation with (<b>a</b>) 0.25%; (<b>b</b>) 0.50%; and (<b>c</b>) 1.00%R.</p> Full article ">Figure 5
<p>X-ray diffractogram of the reference of Ac1 (without retarder) and the reactivated mixtures with Ac1 after seven days of hydration of 0.25%, 0.50%, and 1.00%R—after hydration periods of seven (lower curve) and 28 days (upper curve) per test, with an angular range of 2θ.</p> Full article ">Figure 6
<p>X-ray diffractogram of the reference of Ac2 (without retarder) and the reactivated mixtures with Ac2 after seven days of retardation of 0.25%, 0.50%, and 1.00%R—after hydration periods of seven (lower curve) and 28 days (upper curve) per test, with an angular range of 2θ.</p> Full article ">Figure 7
<p>SEM pictures after a hydration period of seven days, of the reference ((<b>a</b>) of surface and (<b>b</b>) of pore) and the reactivated mixtures with Ac1 after seven days of retardation ((<b>c</b>) of surface and (<b>d</b>) of pore with 0.25%R, (<b>e</b>) of surface and (<b>f</b>) of pore with 1.00%R).</p> Full article ">Figure 8
<p>SEM pictures after a hydration period of seven days, of the reference ((<b>a</b>) of surface and (<b>b</b>) of pore) and the reactivated mixtures with Ac2 after seven days of retardation ((<b>c</b>) of surface and (<b>d</b>) of pore with 0.25%R, (<b>e</b>) of surface and (<b>f</b>) of pore with 1.00%R).</p> Full article ">
5991 KiB  
Article
Evaluating and Modeling the Internal Diffusion Behaviors of Microencapsulated Rejuvenator in Aged Bitumen by FTIR-ATR Tests
by Junfeng Su, Yingyuan Wang, Peng Yang, Shan Han, Ningxu Han and Wei Li
Materials 2016, 9(11), 932; https://doi.org/10.3390/ma9110932 - 17 Nov 2016
Cited by 26 | Viewed by 4798
Abstract
Microencapsulated rejuvenator has been attracted much attention for self-healing bitumen. The diffusion coefficient is one of the key parameters to estimate the feasibility of rejuvenator to age bitumen. The objective of this research was to evaluate diffusion behaviors of microencapsulated rejuvenator in aged [...] Read more.
Microencapsulated rejuvenator has been attracted much attention for self-healing bitumen. The diffusion coefficient is one of the key parameters to estimate the feasibility of rejuvenator to age bitumen. The objective of this research was to evaluate diffusion behaviors of microencapsulated rejuvenator in aged bitumen by a FTIR-ATR method. Various microcapsule samples were mixed in bitumen to form thin films. The core material of microcapsules used as rejuvenator was diphenylsilane (DPS), its fairly specific absorption band at 843 cm−1 was selected as a marker band to calculate the diffusion coefficient (D). The microstructure parameters, including contents, mean size and mean shell thickness of microcapsules, were considered to understand the diffusion behaviors under different temperatures (20, 30, 40 and 50 °C) in bitumen. The results showed that a larger mean size of microcapsules did not greatly affect the D values under the same temperature. In contrast, a higher mean shell thickness decreased the D values because of the decrement of damage probability of microcapsules under the same content. With the same microcapsule sample in bitumen, the D values presented a trend of linear increase when the content of microcapsules was increased. All these results indicated that the microstructure affected the diffusion behaviors based on the concentration of released rejuvenator. A preliminary model of diffusion behaviors of microencapsulated rejuvenator in bitumen was given based on the Arrhenius equation considering the microstructure of microcapsules, the amount of released rejuvenator and the age degree of bitumen. This model may be a guide to the construction and application of self-healing bitumen using microcapsules. Full article
(This article belongs to the Section Advanced Materials Characterization)
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<p>Illustration of the diffusion process of microencapsulated rejuvenator into bitumen.</p> Full article ">Figure 2
<p>The illustration of FTIR-ATR method testing the diffusion behavior of rejuvenator in bitumen, (<b>a</b>) the aluminum plate containing bitumen with notch ends, microcrack generated by liquid N<sub>2</sub>; (<b>b</b>) the FTIR-ATR testing prism.</p> Full article ">Figure 3
<p>Calculating method of diffusion coefficient, (<b>a</b>) the fairly specific absorption band for DPS at 843 com<sup>−1</sup> selected as a marker band to calculate the diffusion coefficient, the integrated peak area determined as absorbance; (<b>b</b>) a logarithmic scale curve of time-absorbance, the sloping line in the horizontal direction determined by the diffusion coefficient.</p> Full article ">Figure 4
<p>Morphologies of microcapsules and microcapsules/bitumen composite, (<b>a</b>,<b>b</b>) optical morphologies of microcapsules; (<b>c</b>) ESEM morphologies of microcapsules; (<b>d</b>) fluorescence microscope morphology of microcapsules/bitumen composite at 25 °C.</p> Full article ">Figure 5
<p>ESEM morphologies of microcracks in bitumen, (<b>a</b>) a microcrack propagation direction; (<b>b</b>) a microcrack punctured several microcapsules.</p> Full article ">Figure 6
<p>Fluorescence microscope morphologies of microencapsulated rejuvenator diffusing into bitumen under 25 °C at different time, the diffusion diameters of rejuvenator from one microcapsule: (<b>a</b>) <span class="html-italic">S</span><sub>1</sub> at 30 min; (<b>b</b>) <span class="html-italic">S</span><sub>2</sub> at 60 min, and (<b>c</b>) <span class="html-italic">S</span><sub>3</sub> at 90 min.</p> Full article ">Figure 7
<p>Absorbance-time curves of 843 cm<sup>−1</sup> band at 30 °C with the microcapsules contents of 2.0, 4.0 and 6.0 wt %.</p> Full article ">Figure 8
<p>Diffusion coefficient values of microcapsules (sample of M-1) in bitumen with contents of 2%, 4% and 6% under a temperature range of 10 °C–60 °C.</p> Full article ">Figure 9
<p>Diffusion coefficient values of microcapsules (content of 6%) in bitumen with different mean size values (samples of M-2, M-4 and M-6) under a temperature range of 10 °C–60 °C.</p> Full article ">Figure 10
<p>Diffusion coefficient values of microcapsules (content of 2%) in bitumen with different shell thickness values (samples of M-1, M-3 and M-5) under a temperature range of 10 °C–60 °C.</p> Full article ">Figure 11
<p>Diffusion coefficient values of microcapsules (content of 6%) in bitumen with different penetration grade values (29.7, 36.8, 47.6, 55.4 and 70.5) under a temperature range of 10 °C–60 °C.</p> Full article ">
7616 KiB  
Article
Feasibility of Using Unbound Mixed Recycled Aggregates from CDW over Expansive Clay Subgrade in Unpaved Rural Roads
by Isaac Del Rey, Jesús Ayuso, Adela P. Galvín, José R. Jiménez and Auxi Barbudo
Materials 2016, 9(11), 931; https://doi.org/10.3390/ma9110931 - 17 Nov 2016
Cited by 29 | Viewed by 5378
Abstract
Social awareness aims to increase practical skills, such as sustainable development, which seeks to increase the use of different types of waste in construction activities. Although insufficient attention is sometimes given to these actions, it is essential to spread information regarding new studies [...] Read more.
Social awareness aims to increase practical skills, such as sustainable development, which seeks to increase the use of different types of waste in construction activities. Although insufficient attention is sometimes given to these actions, it is essential to spread information regarding new studies in the field of waste recycling, which encourages and promotes waste use. Reusing and recycling construction waste in the creation of buildings and infrastructure are fundamental strategies to achieving sustainability in the construction and engineering sectors. In this context, the concept of waste would no longer exist, as waste would become a material resource. Therefore, this study analyses the behaviours of two unbound mixed recycled aggregates (MRA) in the structural layers of an unpaved rural road with low traffic (category T43). The sections were built on inappropriate soil (A-7-6) with a high degree of free swelling. The experimental road consisted of three sections: the first was made with natural aggregates (NA) that were used as a control, the second was composed of MRA in the subbase and NA in the base, and the third section was completely composed of MRA. The materials were characterised in the laboratory. The behaviours of the structural layers in the experimental road were determined by controlling compaction (“in situ” density and moisture) and measuring the deflections and load capacity (deflectometer) during the 18 months after construction. The results show that the sections made with recycled aggregates meet the technical specifications required by General Technical Specifications for Road and Bridge Works (PG-3). Therefore, the water-soluble sulphate content and Los Angeles abrasion coefficient limits can be increased for recycled aggregates without compromising the quality of this type of road with low traffic. To the best of our knowledge, this is the first study regarding the use of unbound MRA made from construction and demolition waste (CDW) in the construction of an unpaved rural road with low traffic on an expansive clay subgrade. Full article
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<p>Illustration of the experimental sections of unpaved rural road.</p> Full article ">Figure 2
<p>Section III of experimental unpaved rural road.</p> Full article ">Figure 3
<p>Particle size distribution. * UGM-32 = Unbound granular material. Maximum aggregate size is 32 mm.</p> Full article ">Figure 4
<p>Rut depth measurement manually with straight edge and steel rule.</p> Full article ">Figure 5
<p>Straight edge of 2 m in each wheel path.</p> Full article ">Figure 6
<p>Vertical stress–settlement diagram of the subgrade layer.</p> Full article ">Figure 7
<p>Vertical stress–settlement diagram of the subbase layer.</p> Full article ">Figure 8
<p>Vertical stress–settlement diagram of the base layer.</p> Full article ">Figure 9
<p>Deflections of subgrade, subbase and base in Section I.</p> Full article ">Figure 10
<p>Deflections of subgrade, subbase and base in Section II.</p> Full article ">Figure 11
<p>Deflections of subgrade, subbase and base in Section III.</p> Full article ">Figure 12
<p>Mean values of dry density and 95% LSD intervals vs. composition of sections.</p> Full article ">Figure 13
<p>Mean values of dry density and 95% LSD intervals vs. date.</p> Full article ">Figure 14
<p>Evolution of the deflection for the base layer over time.</p> Full article ">Figure 15
<p>Mean values of deflections and 95% LSD intervals vs. composition of sections.</p> Full article ">Figure 16
<p>Mean values of deflections and 95% LSD intervals vs. composition of sections.</p> Full article ">Figure 17
<p>Evolution of the elastic modulus for the base layer over time.</p> Full article ">Figure 18
<p>Mean values of rut depth and 95% LSD intervals vs. composition of sections.</p> Full article ">
5960 KiB  
Article
Separation of Hydrogen from Carbon Dioxide through Porous Ceramics
by Taro Shimonosono, Hikari Imada, Hikaru Maeda and Yoshihiro Hirata
Materials 2016, 9(11), 930; https://doi.org/10.3390/ma9110930 - 16 Nov 2016
Cited by 9 | Viewed by 5561
Abstract
The gas permeability of α-alumina, yttria-stabilized zirconia (YSZ), and silicon carbide porous ceramics toward H2, CO2, and H2–CO2 mixtures were investigated at room temperature. The permeation of H2 and CO2 single gases occurred above [...] Read more.
The gas permeability of α-alumina, yttria-stabilized zirconia (YSZ), and silicon carbide porous ceramics toward H2, CO2, and H2–CO2 mixtures were investigated at room temperature. The permeation of H2 and CO2 single gases occurred above a critical pressure gradient, which was smaller for H2 gas than for CO2 gas. When the Knudsen number (λ/r ratio, λ: molecular mean free path, r: pore radius) of a single gas was larger than unity, Knudsen flow became the dominant gas transportation process. The H2 fraction for the mixed gas of (20%–80%) H2–(80%–20%) CO2 through porous Al2O3, YSZ, and SiC approached unity with decreasing pressure gradient. The high fraction of H2 gas was closely related to the difference in the critical pressure gradient values of H2 and CO2 single gas, the inlet mixed gas composition, and the gas flow mechanism of the mixed gas. Moisture in the atmosphere adsorbed easily on the porous ceramics and affected the critical pressure gradient, leading to the increased selectivity of H2 gas. Full article
(This article belongs to the Special Issue Porous Ceramics)
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<p>Molecular mean free paths of H<sub>2</sub> and CO<sub>2</sub> molecules as a function of gas pressure.</p> Full article ">Figure 2
<p>Schematic showing the flux–pressure gradient relation of H<sub>2</sub> and CO<sub>2</sub> gases through porous ceramics. A critical pressure gradient (∆<span class="html-italic">P</span><sub>c</sub>/<span class="html-italic">L</span>) is observed for CO<sub>2</sub> gas.</p> Full article ">Figure 3
<p>Gas permeation apparatus with porous ceramics.</p> Full article ">Figure 4
<p>Microstructures (<b>a</b>,<b>b</b>) and pore size distributions (<b>c</b>,<b>d</b>) of Al<sub>2</sub>O<sub>3</sub> and yttria-stabilized zirconia (YSZ) porous ceramics by mercury porosimetry.</p> Full article ">Figure 5
<p>(<b>a</b>–<b>c</b>) Microstructures and (<b>d</b>) pore size distributions of SiC ceramics hot-pressed at (<b>a</b>) 1400 °C; (<b>b</b>) 1500 °C; and (<b>c</b>) 1700 °C.</p> Full article ">Figure 6
<p>Single-gas flux of H<sub>2</sub> and CO<sub>2</sub> through Al<sub>2</sub>O<sub>3</sub> porous ceramics as a function of the pressure gradient.</p> Full article ">Figure 7
<p>Single-gas flux of H<sub>2</sub> and CO<sub>2</sub> through YSZ porous ceramics as a function of the pressure gradient.</p> Full article ">Figure 8
<p>Single-gas flux of H<sub>2</sub> and CO<sub>2</sub> through porous SiC ceramics hot-pressed at 1400, 1500, and 1700 °C as a function of the pressure gradient.</p> Full article ">Figure 9
<p>Permeability coefficients of (<b>a</b>) H<sub>2</sub> gas and (<b>b</b>) CO<sub>2</sub> gas in Al<sub>2</sub>O<sub>3</sub>, YSZ, and SiC porous ceramics against the pressure gradient above the Δ<span class="html-italic">P</span><sub>c</sub>/<span class="html-italic">L</span> value as a function of the Knudsen number.</p> Full article ">Figure 10
<p>Relationship between the critical pressure gradient and the Knudsen number for (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) YSZ and SiC sintered at 1500 °C, and (<b>c</b>) SiC sintered at 1400 °C and 1700 °C.</p> Full article ">Figure 11
<p>Flux of H<sub>2</sub> and CO<sub>2</sub> gases for the mixed gas of 50 vol % H<sub>2</sub>–50 vol % CO<sub>2</sub> through (<b>a</b>) Al<sub>2</sub>O<sub>3</sub> and (<b>b</b>) YSZ porous ceramics.</p> Full article ">Figure 12
<p>Flux of H<sub>2</sub> and CO<sub>2</sub> gases for the mixed gas of 50 vol % H<sub>2</sub>–50 vol % CO<sub>2</sub> through SiC ceramics hot-pressed at (<b>a</b>) 1400 °C; (<b>b</b>) 1500 °C; and (<b>c</b>) 1700 °C.</p> Full article ">Figure 13
<p>Fraction of H<sub>2</sub> gas for the 50 vol % H<sub>2</sub>–50 vol % CO<sub>2</sub> mixed gas through (<b>a</b>) Al<sub>2</sub>O<sub>3</sub> and YSZ and (<b>b</b>) SiC.</p> Full article ">Figure 14
<p>Fraction of H<sub>2</sub> gas for the 20 vol % H<sub>2</sub>–80 vol % CO<sub>2</sub> mixed gas through (<b>a</b>) Al<sub>2</sub>O<sub>3</sub> and YSZ and (<b>b</b>) SiC.</p> Full article ">Figure 15
<p>Fraction of H<sub>2</sub> gas for the 80 vol % H<sub>2</sub>–20 vol % CO<sub>2</sub> mixed gas through (<b>a</b>) Al<sub>2</sub>O<sub>3</sub> and YSZ and (<b>b</b>) SiC.</p> Full article ">Figure 16
<p>Selectivity (Equation (6)) of (<b>a</b>) Al<sub>2</sub>O<sub>3</sub> and YSZ; and (<b>b</b>) SiC for the 50 vol % H<sub>2</sub>–50 vol % CO<sub>2</sub> mixed gas.</p> Full article ">Figure 17
<p>Comparison between measured and calculated H<sub>2</sub> fractions in the porous Al<sub>2</sub>O<sub>3</sub> ceramics for the supplied gas of (<b>a</b>) 80 vol % H<sub>2</sub>–20 vol % CO<sub>2</sub>; (<b>b</b>) 50 vol % H<sub>2</sub>–50 vol % CO<sub>2</sub>, and (<b>c</b>) 20 vol % H<sub>2</sub>–80 vol % CO<sub>2</sub>.</p> Full article ">Figure 18
<p>Comparison between measured and calculated H<sub>2</sub> fractions in the porous SiC ceramics hot-pressed at 1400 °C for the supplied gas of (<b>a</b>) 80 vol % H<sub>2</sub>–20 vol % CO<sub>2</sub>; (<b>b</b>) 50 vol % H<sub>2</sub>–50 vol % CO<sub>2</sub>; and (<b>c</b>) 20 vol % H<sub>2</sub>–80 vol % CO<sub>2</sub>.</p> Full article ">Figure 19
<p>Flux of H<sub>2</sub> and CO<sub>2</sub> gases permeated through Al<sub>2</sub>O<sub>3</sub> porous ceramics (60.9% relative density) for the 50 vol % H<sub>2</sub>–50 vol % CO<sub>2</sub> mixed gas (<b>a</b>) with and (<b>b</b>) without 3 vol % H<sub>2</sub>O.</p> Full article ">Figure 20
<p>H<sub>2</sub> fractions through the different four samples of Al<sub>2</sub>O<sub>3</sub> sintered at 800 °C for the dried gas of (<b>a</b>) 80 vol % H<sub>2</sub>–20 vol % CO<sub>2</sub>; (<b>b</b>) 50 vol % H<sub>2</sub>–50 vol % CO<sub>2</sub> and (<b>c</b>) 20 vol % H<sub>2</sub>–80 vol % CO<sub>2</sub>.</p> Full article ">Figure 21
<p>Influence of humidification of supplied gas of (<b>a</b>) 80 vol % H<sub>2</sub>–20 vol % CO<sub>2</sub>; (<b>b</b>) 50 vol % H<sub>2</sub>–50 vol % CO<sub>2</sub> and (<b>c</b>) 20 vol % H<sub>2</sub>–80 vol % CO<sub>2</sub> on the H<sub>2</sub> fractions through the porous Al<sub>2</sub>O<sub>3</sub> ceramics (60.9% relative density, sample No. 4 in <a href="#materials-09-00930-f020" class="html-fig">Figure 20</a>).</p> Full article ">
19303 KiB  
Article
Freckle Defect Formation near the Casting Interfaces of Directionally Solidified Superalloys
by Jianping Hong, Dexin Ma, Jun Wang, Fu Wang, Baode Sun, Anping Dong, Fei Li and Andreas Bührig-Polaczek
Materials 2016, 9(11), 929; https://doi.org/10.3390/ma9110929 - 16 Nov 2016
Cited by 25 | Viewed by 8308
Abstract
Freckle defects usually appear on the surface of castings and industrial ingots during the directional solidification process and most of them are located near the interface between the shell mold and superalloys. Ceramic cores create more interfaces in the directionally solidified (DS) and [...] Read more.
Freckle defects usually appear on the surface of castings and industrial ingots during the directional solidification process and most of them are located near the interface between the shell mold and superalloys. Ceramic cores create more interfaces in the directionally solidified (DS) and single crystal (SX) hollow turbine blades. In order to investigate the location of freckle occurrence in superalloys, superalloy CM247 LC was directionally solidified in an industrial-sized Bridgman furnace. Instead of ceramic cores, Alumina tubes were used inside of the casting specimens. It was found that freckles occur not only on the casting external surfaces, but also appear near the internal interfaces between the ceramic core and superalloys. Meanwhile, the size, initial position, and area of freckle were investigated in various diameters of the specimens. The initial position of the freckle chain reduces when the diameter of the rods increase. Freckle area follows a linear relationship in various diameters and the average freckle fraction is 1.1% of cross sectional area of casting specimens. The flow of liquid metal near the interfaces was stronger than that in the interdendritic region in the mushy zone, and explained why freckle tends to occur on the outer or inner surfaces of castings. This new phenomenon suggests that freckles are more likely to occur on the outer or inner surfaces of the hollow turbine blades. Full article
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<p>SEM micrograph showing the as-cast microstructure of the CM 247 LC superalloy.</p> Full article ">Figure 2
<p>Schematic diagram of (<b>a</b>) 3D design of a series of solid rod specimens, and (<b>b</b>) possible freckle formation on the external surface.</p> Full article ">Figure 3
<p>Schematic diagram of (<b>a</b>) 3D design of a series of rod specimens with multi-interfacial features and (<b>b</b>) possible freckle formation on the multi-interfaces.</p> Full article ">Figure 4
<p>The process of directional solidification in the industrial vacuum Bridgman furnace: (<b>a</b>) Shell mold; (<b>b</b>) mold loaded in the Bridgman furnace; (<b>c</b>) melt pouring, and (<b>d</b>) directionally solidification and mold cooling.</p> Full article ">Figure 5
<p>The temperature of the heating system during the solidification and cooling process in the Bridgman furnace.</p> Full article ">Figure 6
<p>The temperature of the heating and the shadow side of the Ø19 mm rod during the solidification and cooling process (at a height of 190 mm from the chill plate).</p> Full article ">Figure 7
<p>Freckle defects on CM247 LC casting rods with diameters of 5 mm, 7 mm, 9 mm, 11 mm, 13 mm, and 15 mm after directional solidification in a vacuum Bridgman furnace with a low withdraw rate of 1.0 mm/min. (<b>a</b>) freckles location; (<b>b</b>) magnification picture of freckles.</p> Full article ">Figure 8
<p>Freckle observed under metallurgical microscopy on the cross section of CM247 LC casting rods (at a height of 210 mm from the cooling chill) with diameters of (<b>a</b>) 5 mm; (<b>b</b>) 7 mm; (<b>c</b>) 9 mm; (<b>d</b>) 11 mm; (<b>e</b>) 13 mm; (<b>f</b>) 15 mm; and (<b>g</b>) 19 mm.</p> Full article ">Figure 9
<p>Freckle chain occurs on the: (<b>a</b>) internal surface and (<b>b</b>) cross section of specimen; (<b>c</b>) external surface of CM247 LC.</p> Full article ">Figure 10
<p>Magnified photos of freckles near the multi-interfaces (cross section of superalloy CM247 LC in <a href="#materials-09-00929-f006" class="html-fig">Figure 6</a>) on (<b>a</b>) the interface of the inner superalloy A and (<b>b</b>) the interface of the outer superalloy B.</p> Full article ">Figure 11
<p>Freckles on the specimens with various diameters of ceramic tubes inside: (<b>a</b>) 1 mm; (<b>b</b>) 2 mm; (<b>c</b>) 4 mm; (<b>d</b>) 5 mm; (<b>e</b>) 6 mm; (<b>f</b>) 8 mm; (<b>g</b>) 11 mm; and (<b>h</b>) 12 mm.</p> Full article ">Figure 12
<p>Composition (in wt %) in the matrix and freckle area of as-cast CM 247 LC with a 11 mm diameter ceramic tube inside, by SEM with EDS: (<b>a</b>) Inspection zone A1 is the external freckle area, Inspection zone A3 is the matrix area; (<b>b</b>) Inspection zone A2 is the internal freckle area; (<b>c</b>) EDS results.</p> Full article ">Figure 13
<p>Cross sections of CM247 LC at different heights from the cooling chill (with a 5 mm diameter), freckles were observed above a height of 150 mm from the chill plate: (<b>a</b>) height of 210 mm; (<b>b</b>) height of 190 mm; (<b>c</b>) height of 150 mm; (<b>d</b>) height of 110 mm.</p> Full article ">Figure 14
<p>Initiation position of the freckle chain in various diameters.</p> Full article ">Figure 15
<p>Statistics of the maximum and minimum width of freckle chains with incremental diameter of the specimens.</p> Full article ">Figure 16
<p>Experimental date and the fitting line of the primary dendrite arm spacing (<span class="html-italic">λ</span><sub>1</sub>) at the height of the freckle initiation position with diameters of 5 mm, 7 mm, 9 mm, 11 mm, 13 mm, 15 mm, and 19 mm.</p> Full article ">Figure 17
<p>Freckle area and fitting curve on the top of CM247 LC rods for various cross sectional areas from 20 to 284 mm<sup>2</sup>.</p> Full article ">Figure 18
<p>Freckle area percentage and fitting curve on the top of CM247 LC rods for various cross sectional areas from 20 to 284 mm<sup>2</sup>. The average value is 1.1% from this figure.</p> Full article ">Figure 19
<p>Schematic diagram of the inclination of the primary dendrites with respect to the mold wall. Micro-segregation causes density inversion near the interface of the mold wall and casting on the shadow side.</p> Full article ">Figure 20
<p>Schematic diagram of freckle formation (<b>a</b>) inside of superalloy and (<b>b</b>) near the interfaces of superalloys and ceramic materials.</p> Full article ">
2066 KiB  
Communication
Mechanical Properties and In Vitro Degradation of Sputtered Biodegradable Fe-Au Foils
by Till Jurgeleit, Eckhard Quandt and Christiane Zamponi
Materials 2016, 9(11), 928; https://doi.org/10.3390/ma9110928 - 15 Nov 2016
Cited by 7 | Viewed by 3324
Abstract
Iron-based materials proved being a viable candidate material for biodegradable implants. Magnetron sputtering combined with UV-lithography offers the possibility to fabricate structured, freestanding foils of iron-based alloys and even composites with non-solvable elements. In order to accelerate the degradation speed and enhance the [...] Read more.
Iron-based materials proved being a viable candidate material for biodegradable implants. Magnetron sputtering combined with UV-lithography offers the possibility to fabricate structured, freestanding foils of iron-based alloys and even composites with non-solvable elements. In order to accelerate the degradation speed and enhance the mechanical properties, the technique was used to fabricate Fe-Au multilayer foils. The foils were annealed after the deposition to form a homogeneous microstructure with fine Au precipitates. The characterization of the mechanical properties was done by uniaxial tensile tests. The degradation behavior was analyzed by electrochemical tests and immersion tests under in vitro conditions. Due to the noble Au precipitates it was possible to achieve high tensile strengths between 550 and 800 MPa depending on the Au content and heat treatment. Furthermore, the Fe-Au foils showed a significantly accelerated corrosion compared to pure iron samples. The high mechanical strength is close to the properties of SS316L steel. In combination with the accelerated degradation rate, sputtered Fe-Au foils showed promising properties for use as iron-based, biodegradable implants. Full article
(This article belongs to the Section Biomaterials)
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<p>Ultimate tensile strength of the Fe, FeAu0.3, FeAu1.0 and FeAu2.5 samples, before and after different heat treatments.</p> Full article ">Figure 2
<p>Fracture strain of the Fe, FeAu0.3, FeAu1.0 and FeAu2.5 samples, before and after different heat treatments.</p> Full article ">Figure 3
<p>STEM images and EDX Fe-K-α and Au-L-α elemental mappings of Fe-Au sample cross-section, as deposited (<b>a</b>) and annealed at 800 °C for two hours (<b>b</b>–<b>g</b>). In the images Au precipitates appear bright due to the material contrast. (<b>a</b>) FeAu2.5 sample as deposited with intact multilayer structure; (<b>b</b>) FeAu2.5 sample annealed and (<b>c</b>) Fe-Au STEM/EDX mapping of Au precipitates in a grain and along a grain boundary; (<b>d</b>) FeAu1.0 sample annealed; the bright Au precipitates are barely visible along the grain boundaries but still resolvable in the EDX mapping (<b>e</b>). FeAu0.3 sample annealed (<b>f</b>), bright areas along the grain boundaries cannot be identified by EDX mapping (<b>g</b>).</p> Full article ">Figure 4
<p>Weight loss of Fe, FeAu0.3, FeAu1.0 and FeAu2.5 samples, after immersion for different times in HBSS (pH 7.4; 37 °C).</p> Full article ">Figure 5
<p>Mean corrosion rate of Fe, FeAu1.0 and FeAu2.5 samples. Using Equation (1), the corrosion rates were calculated from the corrosion current density <span class="html-italic">j<sub>c</sub></span>, determined linear polarization in HBSS (pH 7.4; 37 °C) and Tafel extrapolation method.</p> Full article ">Figure 6
<p>SEM surface image and EDX elemental mappings of the Fe-L-α and Au-M-α lines for (<b>a</b>) a FeAu1.0 and (<b>b</b>) FeAu2.5 sample annealed at 800 °C, 2 h. In the SEM image Au precipitates appearing bright due to the Z-contrast.</p> Full article ">
3191 KiB  
Article
ZnO-Layered Double Hydroxide@Graphitic Carbon Nitride Composite for Consecutive Adsorption and Photodegradation of Dyes under UV and Visible Lights
by Luhong Zhang, Li Li, Xiaoming Sun, Peng Liu, Dongfang Yang and Xiusong Zhao
Materials 2016, 9(11), 927; https://doi.org/10.3390/ma9110927 - 15 Nov 2016
Cited by 50 | Viewed by 7999
Abstract
In this work, a ZnO-layered double hydroxide@graphitic carbon nitride composite (ZnO-LDH@C3N4) was synthesized via co-precipitation method with solvothermal treatment. The structure and morphology of ZnO-LDH@C3N4 composite were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy [...] Read more.
In this work, a ZnO-layered double hydroxide@graphitic carbon nitride composite (ZnO-LDH@C3N4) was synthesized via co-precipitation method with solvothermal treatment. The structure and morphology of ZnO-LDH@C3N4 composite were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopes/transmission electron microscopes (SEM/TEM), N2 adsorption/desorption, ultraviolet visible diffuse reflectance spectroscopy (UV-Vis-DRS), photoluminescence spectrometer (PL) and electrochemical impedance spectroscopy (EIS). The adsorption and photocatalytic properties of ZnO-LDH@C3N4 composite towards the organic dyes: Orange II sodium salt (OrgII, an anionic azo dye) and methylene blue (MB, a cationic azo dye) were investigated. Compared to ZnO-LDH and g-C3N4, the ZnO-LDH@C3N4 composite displayed an excellent performance in both adsorption and photocatalytic degradation of the organic dyes. Moreover, a combination of ZnO-LDH and g-C3N4 significantly improved the photocatalytic performance of ZnO-LDH and g-C3N4 under visible-light irradiation. The adsorption and photocatalytic mechanism were also investigated. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
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<p>XRD patterns of g-C<sub>3</sub>N<sub>4</sub>, ZnO-LDH and ZnO-LDH@C<sub>3</sub>N<sub>4</sub>.</p> Full article ">Figure 2
<p>XPS images of the g-C<sub>3</sub>N<sub>4</sub> and ZnO-LDH@C<sub>3</sub>N<sub>4</sub> composite. (<b>A</b>) Survey spectrum for g-C<sub>3</sub>N<sub>4</sub>; (<b>B</b>) High-resolution N 1s XPS spectrum of g-C<sub>3</sub>N<sub>4</sub>; (<b>C</b>) High-resolution C 1s XPS spectrum of g-C<sub>3</sub>N<sub>4</sub>; (<b>D</b>) Survey spectrum for the ZnO-LDH@C<sub>3</sub>N<sub>4</sub> composite; (<b>E</b>–<b>I</b>) are high-resolution XPS spectra for N 1s, C 1s, Zn 2p, O 1s and Al 2p of the ZnO-LDH@C<sub>3</sub>N<sub>4</sub> composite respectively.</p> Full article ">Figure 3
<p>(<b>A</b>) TEM image for g-C<sub>3</sub>N<sub>4</sub>; (<b>B</b>) TEM image for ZnO-LDH@C<sub>3</sub>N<sub>4</sub>; (<b>C</b>) SEM image for ZnO-LDH@C<sub>3</sub>N<sub>4</sub>; (<b>D</b>) SEM image for ZnO-LDH.</p> Full article ">Figure 4
<p>(<b>A</b>) The adsorption dynamic of ZnO-LDH@C<sub>3</sub>N<sub>4</sub> in OrgII adsorption. The insert is adsorption capacity comparison among g-C<sub>3</sub>N<sub>4</sub>, ZnO-LDH@C<sub>3</sub>N<sub>4</sub> and ZnO-LDH; (<b>B</b>) FT-IR spectra of (<b>a</b>) g-C<sub>3</sub>N<sub>4</sub>, (<b>b</b>) ZnO-LDH, (<b>c</b>) ZnO-LDH@C<sub>3</sub>N<sub>4</sub>, (<b>d</b>) OrgII, (<b>e</b>) ZnO-LDH@C<sub>3</sub>N<sub>4</sub> after saturated adsorption with OrgII.</p> Full article ">Figure 5
<p>(<b>a</b>) Comparison of MB adsorption and photodegradation in water under UV-light over ZnO, ZnO-LDH, g-C<sub>3</sub>N<sub>4</sub> and ZnO-LDH@C<sub>3</sub>N<sub>4</sub> respectively; (<b>b</b>) Comparison of MB adsorption and photodegradation in water under visible-light over ZnO, ZnO-LDH, g-C<sub>3</sub>N<sub>4</sub> and ZnO-LDH@C<sub>3</sub>N<sub>4</sub> respectively; (<b>c</b>) Kinetic fit for the degradation of MB with the ZnO, ZnO-LDH, g-C<sub>3</sub>N<sub>4</sub> and ZnO-LDH@C<sub>3</sub>N<sub>4</sub> respectively under visible light; (<b>d</b>) UV-vis diffuse reflectance spectra of the photocatalysts with corresponding tangent lines; (<b>e</b>) Photoluminescence spectra of g-C<sub>3</sub>N<sub>4</sub>, ZnO, ZnO-LDH and ZnO-LDH@C<sub>3</sub>N<sub>4</sub>; (<b>f</b>) Electrochemical impedance spectroscopy of g-C<sub>3</sub>N<sub>4</sub>, ZnO, ZnO-LDH and ZnO-LDH@C<sub>3</sub>N<sub>4</sub> composite.</p> Full article ">Figure 6
<p>(<b>A</b>) The experimental data and the fitting plots of photogenerated carriers trapping in the photodegradation of MB by ZnO-LDH@C<sub>3</sub>N<sub>4</sub> under UV-light irradiation; (<b>B</b>) The experimental data and the fitting plots of photogenerated carriers trapping in the photodegradation of MB by ZnO-LDH@C<sub>3</sub>N<sub>4</sub> under visible-light irradiation.</p> Full article ">Figure 7
<p>Schematic illustration of the mechanism of uptake of anionic dye OrgII and the charge separation and photocatalytic activity of the ZnO-LDH@C<sub>3</sub>N<sub>4</sub> under UV- and visible-light irradiation, respectively.</p> Full article ">Scheme 1
<p>Schematic representation of the synthesis process of the ZnO-LDH@C<sub>3</sub>N<sub>4</sub> composite.</p> Full article ">
5407 KiB  
Article
Tissue-Like Phantoms as a Platform for Inserted Fluorescence Nano-Probes
by Tsviya Nayhoz, Eran A. Barnoy and Dror Fixler
Materials 2016, 9(11), 926; https://doi.org/10.3390/ma9110926 - 15 Nov 2016
Cited by 7 | Viewed by 5299
Abstract
Tissue-like phantoms are widely used as a model for mimicking the optical properties of live tissue. This paper presents the results of a diffusion reflection method and fluorescence lifetime imaging microscopy measurements of fluorescein-conjugated gold nanorods in solution, as well as inserted in [...] Read more.
Tissue-like phantoms are widely used as a model for mimicking the optical properties of live tissue. This paper presents the results of a diffusion reflection method and fluorescence lifetime imaging microscopy measurements of fluorescein-conjugated gold nanorods in solution, as well as inserted in solid tissue-imitating phantoms. A lack of consistency between the fluorescence lifetime results of the solutions and the phantoms raises a question about the ability of tissue-like phantoms to maintain the optical properties of inserted contrast agents. Full article
(This article belongs to the Special Issue Nanoprobes for Imaging)
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<p>A bar plot of ln(ρ<sup>2</sup>Γ(ρ)) slopes of the different phantoms, which were measured using the DR method. In the upper right corner, the absorption spectrum of the GNRs is presented with the DR light source wavelengths marked by diamonds.</p> Full article ">Figure 2
<p>FLT histogram of fluorescein 0.33 µM solution.</p> Full article ">Figure 3
<p>τ<sub>1</sub> histograms for fluorescein-conjugated GNR solutions with different linkers: (<b>a</b>) NH<sub>2</sub>-PEG-SH-5 kDa; (<b>b</b>) NH<sub>2</sub>-PEG-SH-1 kDa; (<b>c</b>) 16-amino-1-hexadecanethiol; (<b>d</b>) 11-amino-1-undecanethiol; (<b>e</b>) 6-amino-1-hexanethiol; (<b>f</b>) MDDA (Au concentration 1 mg/mL, fluorescein concentration 6.6 µM).</p> Full article ">Figure 4
<p>FLT histogram of free fluorescein phantom. The fluorescein concentration in the phantom was 0.33 μM.</p> Full article ">Figure 5
<p>τ<sub>1</sub> histograms for fluorescein-conjugated GNR phantoms with different linkers: (<b>a</b>) NH<sub>2</sub>-PEG-SH-5 kDa; (<b>b</b>) NH<sub>2</sub>-PEG-SH-1 kDa; (<b>c</b>) 16-amino-1-hexadecanethiol; (<b>d</b>) 11-amino-1-undecanethiol; (<b>e</b>) 6-amino-1-hexanethiol; (<b>f</b>) MDDA. Histograms are shown for three areas indicated by the different colors. In all phantoms, Au concentration was 0.05 mg/mL, and fluorescein concentration was 0.33 µM.</p> Full article ">Figure 5 Cont.
<p>τ<sub>1</sub> histograms for fluorescein-conjugated GNR phantoms with different linkers: (<b>a</b>) NH<sub>2</sub>-PEG-SH-5 kDa; (<b>b</b>) NH<sub>2</sub>-PEG-SH-1 kDa; (<b>c</b>) 16-amino-1-hexadecanethiol; (<b>d</b>) 11-amino-1-undecanethiol; (<b>e</b>) 6-amino-1-hexanethiol; (<b>f</b>) MDDA. Histograms are shown for three areas indicated by the different colors. In all phantoms, Au concentration was 0.05 mg/mL, and fluorescein concentration was 0.33 µM.</p> Full article ">Figure 6
<p>FLIM images of (<b>a</b>) free fluorescein control phantom, and the image of the interface region of base phantoms containing free fluorescein (fluorescein concentration of 330 nM) and phantoms containing fluorescein-conjugated-GNRs with conjugation through different likers: (<b>b</b>) NH<sub>2</sub>-PEG-SH-5 kDa; (<b>c</b>) NH<sub>2</sub>-PEG-SH-1 kDa; (<b>d</b>) 16-amino-1-hexadecanethiol; (<b>e</b>) 11-amino-1-undecanethiol; (<b>f</b>) 6-amino-1-hexanethiol; (<b>g</b>) MDDA (Au concentration 0.05 mg/mL, fluorescein concentration of 330 nM). Color indicates the average FLT in each pixel.</p> Full article ">Figure 7
<p>Bar plot of τ<sub>1</sub> for fluorescein-conjugated GNRs with different linkers’ solutions and phantoms (indicated by striped or solid texture respectively), where three area measurements are shown for each phantom. Free fluorescein solution and phantom FLTs are shown at the end for comparison.</p> Full article ">Figure 8
<p>GNRs characteristics: (<b>a</b>) GNRs normalized absorption spectrum; (<b>b</b>) GNRs TEM image.</p> Full article ">Figure 9
<p>A schematic representation of the linkers’ end-to-end length in scale relatively to each other.</p> Full article ">Figure 10
<p>A schematic representation of the GNRs’ fabrication and fluorescein conjugation process.</p> Full article ">Figure 11
<p>A schematic representation of the DR system.</p> Full article ">Figure 12
<p>An image of the FLIM system.</p> Full article ">
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Article
Comparison of Electrochemical Methods for the Evaluation of Cast AZ91 Magnesium Alloy
by Jakub Tkacz, Jozef Minda, Stanislava Fintová and Jaromír Wasserbauer
Materials 2016, 9(11), 925; https://doi.org/10.3390/ma9110925 - 15 Nov 2016
Cited by 39 | Viewed by 6417
Abstract
Linear polarization is a potentiodynamic method used for electrochemical characterization of materials. Obtained values of corrosion potential and corrosion current density offer information about material behavior in corrosion environments from the thermodynamic and kinetic points of view, respectively. The present study offers a [...] Read more.
Linear polarization is a potentiodynamic method used for electrochemical characterization of materials. Obtained values of corrosion potential and corrosion current density offer information about material behavior in corrosion environments from the thermodynamic and kinetic points of view, respectively. The present study offers a comparison of applications of the linear polarization method (from −100 mV to +200 mV vs. EOCP), the cathodic polarization of the specimen (−100 mV vs. EOCP), and the anodic polarization of the specimen (+100 mV vs. EOCP), and a discussion of the differences in the obtained values of the electrochemical characteristics of cast AZ91 magnesium alloy. The corrosion current density obtained by cathodic polarization was similar to the corrosion current density obtained by linear polarization, while a lower value was obtained by anodic polarization. Signs of corrosion attack were observed only in the case of linear polarization including cathodic and anodic polarization of the specimen. Full article
(This article belongs to the Special Issue Degradable Biomaterials Based on Magnesium Alloys)
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Figure 1

Figure 1
<p>Tafel extrapolation of the cathodic part of the polarization curve.</p> Full article ">Figure 2
<p>Microstructure of AZ91 magnesium alloy (<b>a</b>) and elemental maps: (<b>b</b>) magnesium; (<b>c</b>) aluminum; (<b>d</b>) zinc; and (<b>e</b>) manganese (SEM).</p> Full article ">Figure 3
<p>Cathodic polarization curves (CPCs) of AZ91 tested in 0.1 M NaCl solution; −100 mV vs. E<sub>OCP</sub>.</p> Full article ">Figure 4
<p>Anodic polarization curves (APCs) of AZ91 tested in 0.1 M NaCl solution; +100 mV vs. E<sub>OCP</sub>.</p> Full article ">Figure 5
<p>Linear polarization curves (PC) of AZ91 in 0.1 M NaCl solution containing cathodic and anodic parts; from −100 mV to +200 mV vs. E<sub>OCP</sub>.</p> Full article ">Figure 6
<p>Comparison of polarization techniques of AZ91 in 0.1 M NaCl solution (CPC, APC, PC).</p> Full article ">Figure 7
<p>Surface of AZ91 magnesium alloy after electrochemical measurements: (<b>a</b>) cathodic polarization; (<b>b</b>) anodic polarization; and (<b>c</b>) linear polarization.</p> Full article ">
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