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Coatings
Volume 9
Issue 7
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Coatings, Volume 9, Issue 7 (July 2019) – 53 articles

Cover Story (view full-size image): Microencapsulated essential oils (EOs) are increasingly used to protect the safety of foods due to their natural origin. Pork meat pieces were coated with a combination of basil and oregano microencapsulated EOs, which upon GC/MS analysis their main components were linalool (23.7%) and thymol (28.9%), respectively. EOs exerted membrane damage to spoilage and pathogenic bacteria, such as E. coli O157:H7, Brochothrix thermosphacta and Pseudomonas fragi. The EOs showed antioxidant activity, preventing oxidation of lipids of coated meat without affecting sensory properties, after 28 days of storage at 4°C. Active coatings are a natural food preservation alternative. View this paper.
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12 pages, 6313 KiB  
Article
Biofouling of FeNP-Coated SWRO Membranes with Bacteria Isolated after Pre-Treatment in the Sea of Cortez
by Maria Magdalena Armendáriz-Ontiveros, Gustavo A. Fimbres Weihs, Sergio de los Santos Villalobos and Sergio G. Salinas-Rodriguez
Coatings 2019, 9(7), 462; https://doi.org/10.3390/coatings9070462 - 23 Jul 2019
Cited by 8 | Viewed by 5546
Abstract
Commercial seawater reverse osmosis (SWRO) membranes were coated with iron nanoparticles (FeNPs) and biofouled with a bacterium strain isolated from the Sea of Cortez, Mexico. This strain was selected and characterized, as it was the only cultivable strain in pretreated seawater. Molecular identification [...] Read more.
Commercial seawater reverse osmosis (SWRO) membranes were coated with iron nanoparticles (FeNPs) and biofouled with a bacterium strain isolated from the Sea of Cortez, Mexico. This strain was selected and characterized, as it was the only cultivable strain in pretreated seawater. Molecular identification of the strain showed that it belongs to Bacillus halotolerans MCC1. This strain was Gram positive with spore production, and was susceptible to Fe+2 toxicity with a minimum inhibitory concentration of 1.8 g L−1. Its biofouling potential on both uncoated and FeNP coated reverse osmosis (RO) membranes was measured via biofilm layer thickness, total cell count, optical density and organic matter. The FeNP-coated RO membrane presented a significant reduction in biofilm cake layer thickness (>90%), total cells (>67%), optical density (>42%) and organic matter (>92%) with respect to an uncoated commercial membrane. Thus, Bacillus halotolerans MCC1 shows great potential to biofoul RO membranes as it can pass through ultrafiltration membranes due to its spore producing ability; nonetheless, FeNP-coated membranes represent a potential alternative to mitigate RO membrane biofouling. Full article
(This article belongs to the Special Issue Novel Marine Antifouling Coatings)
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Figure 1

Figure 1
<p>Map showing the location of the water collection point.</p> Full article ">Figure 2
<p>Representative diagram of the experimental setup for accelerated biofouling of RO membranes.</p> Full article ">Figure 3
<p>Macro and microscopic traits of the <span class="html-italic">B. halotolerans</span> MCC1 strain. (<b>a</b>) Bacterial colonies on nutritive agar; (<b>b</b>) bacterial Gram stain; (<b>c</b>) bacterial sporulation.</p> Full article ">Figure 4
<p>Effect of Fe<sup>+2</sup> concentration on the growth rate of <span class="html-italic">B. halotolerans</span> MCC1.</p> Full article ">Figure 5
<p>Final bacterial population of the strain MCC1 at different Fe<sup>+2</sup> concentrations. <span class="html-italic">C</span> (Fe<sup>+2</sup>): concentration of Fe<sup>+2</sup>. <span class="html-italic">R</span>: correlation coefficient. <span class="html-italic">p</span>: probability. <span class="html-italic">R</span><sup>2</sup>: coefficient of determination without adjustment. **: highly significant.</p> Full article ">Figure 6
<p>SEM image of FeNPs.</p> Full article ">Figure 7
<p>XRD of the FeNPs showing the peaks associated with the Fe (red arrows) and iron oxides (black arrows) present on the FeNPs.</p> Full article ">Figure 8
<p>Photographs of the RO membranes before and after the accelerated biofouling tests: (<b>a</b>) membrane before the test, (<b>b</b>) bacterial growth on uncoated membrane, and (<b>c</b>) bacterial growth on FeNP-coated membrane.</p> Full article ">Figure 9
<p>Effect of FeNP coating on biofilm parameters obtained after biofouling of RO membranes by <span class="html-italic">Bacillus halotolerans</span> MCC1: (<b>a</b>) thickness of biofilm layer formed onto the membranes; (<b>b</b>) bacterial count obtained from scraped biofilm; (<b>c</b>) optical density of scraped biofilm; (<b>d</b>) organic matter in scraped biofilm.</p> Full article ">Figure 9 Cont.
<p>Effect of FeNP coating on biofilm parameters obtained after biofouling of RO membranes by <span class="html-italic">Bacillus halotolerans</span> MCC1: (<b>a</b>) thickness of biofilm layer formed onto the membranes; (<b>b</b>) bacterial count obtained from scraped biofilm; (<b>c</b>) optical density of scraped biofilm; (<b>d</b>) organic matter in scraped biofilm.</p> Full article ">
9 pages, 3615 KiB  
Article
The Effect of Heat Treatment on Properties of Ni–P Coatings Deposited on a AZ91 Magnesium Alloy
by Martin Buchtík, Michaela Krystýnová, Jiří Másilko and Jaromír Wasserbauer
Coatings 2019, 9(7), 461; https://doi.org/10.3390/coatings9070461 - 23 Jul 2019
Cited by 49 | Viewed by 4800
Abstract
The present study reports the effect of phosphorus content in deposited electroless nickel (Ni–P) coatings, the heat treatment on the microhardness and its microstructural characteristics, and the influence of the temperature on the microstructure of the Mg alloy substrate during the heat treatment. [...] Read more.
The present study reports the effect of phosphorus content in deposited electroless nickel (Ni–P) coatings, the heat treatment on the microhardness and its microstructural characteristics, and the influence of the temperature on the microstructure of the Mg alloy substrate during the heat treatment. The deposition of Ni–P coatings was carried out in the electroless nickel bath, and the resulting P content ranged from 5.2 to 10.8 wt.%. Prepared samples were heat-treated in the muffle furnace at 400 °C for 1 h after the coating deposition. The cooling of the samples to room temperature was proceeded in the air. For as-deposited and heat-treated samples, it was determined that with the increasing P content, the microhardness was decreasing. This may be caused by the changes in the structure of the Ni–P coating. The X-ray diffraction patterns of the as-deposited Ni–P coatings showed that the microstructure changed their nature from crystalline to amorphous with the increasing P content. The heat treatment of prepared samples led to the significant increase of microhardness of Ni–P coatings. All the heat-treated samples showed the crystalline character, regardless of the P content and the presence of hard Ni3P phase, which can have a positive effect on the increase of microhardness. The metallographic analysis showed changes of substrate microstructure after the heat treatment. The prepared coatings were uniform and with no visible defects. Full article
(This article belongs to the Special Issue Surface Engineering of Light Alloys)
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Figure 1

Figure 1
<p>Microstructure of Ni–P coatings with 7.4 wt.% P (<b>a</b>) as-deposited; (<b>b</b>) heat-treated.</p> Full article ">Figure 2
<p>Microstructure of the AZ91 Mg alloy (<b>a</b>) as-cast, (<b>b</b>) heat-treated at 400 °C for 1 h.</p> Full article ">Figure 3
<p>Microhardness dependence on the phosphorus content of Ni–P coatings, (<b>a</b>) as-deposited, (<b>b</b>) heat-treated.</p> Full article ">Figure 4
<p>XRD patterns of (<b>a</b>) as-deposited and (<b>b</b>) heat-treated Ni–P coatings with different phosphorus content.</p> Full article ">Figure 5
<p>The effect of Ni crystallite size on the P content in (<b>a</b>) as-deposited Ni–P coatings and (<b>b</b>) heat-treated Ni–P coatings.</p> Full article ">Figure 6
<p>The effect of Ni<sub>3</sub>P crystallite size on the P content in heat-treated Ni–P coatings.</p> Full article ">
19 pages, 4654 KiB  
Review
Porosity and Its Significance in Plasma-Sprayed Coatings
by John Gerald Odhiambo, WenGe Li, YuanTao Zhao and ChengLong Li
Coatings 2019, 9(7), 460; https://doi.org/10.3390/coatings9070460 - 23 Jul 2019
Cited by 120 | Viewed by 12263
Abstract
Porosity in plasma-sprayed coatings is vital for most engineering applications. Porosity has its merits and demerits depending on the functionality of the coating and the immediate working environment. Consequently, the formation mechanisms and development of porosity have been extensively explored to find out [...] Read more.
Porosity in plasma-sprayed coatings is vital for most engineering applications. Porosity has its merits and demerits depending on the functionality of the coating and the immediate working environment. Consequently, the formation mechanisms and development of porosity have been extensively explored to find out modes of controlling porosity in plasma-sprayed coatings. In this work, a comprehensive review of porosity on plasma-sprayed coatings is established. The formation and development of porosity on plasma-sprayed coatings are governed by set spraying parameters. Optimized set spraying parameters have been used to achieve the most favorable coatings with minimum defects. Even with the optimized set spraying parameters, defects like porosity still occur. Here, we discuss other ways that can be used to control porosity in plasma-sprayed coating with emphasis to atmospheric plasma-sprayed chromium oxide coatings. Techniques like multilayer coatings, nanostructured coatings, doping with rare earth elements, laser surface re-melting and a combination of the above methods have been suggested in adjusting porosity. The influences of porosity on microstructure, properties of plasma-sprayed coatings and the measurement methods of porosity have also been reviewed. Full article
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Figure 1

Figure 1
<p>Showing the components of thermal barrier coating (TBC) (<b>a</b>) before oxidation (<b>b</b>) after oxidation with the inclusion of thermally grown oxide (TGO).</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) images showing typical atmospheric plasma-sprayed coating morphology for chromium oxide coating on Q235 steel.</p> Full article ">Figure 3
<p>Porosity characterization techniques.</p> Full article ">Figure 4
<p>Cross-sectional view of a mercury penetrometer.</p> Full article ">Figure 5
<p>A representation of a multilayer coating where two different coating materials are alternated.</p> Full article ">Figure 6
<p>Schematic representation of a co-doping coating.</p> Full article ">Figure 7
<p>Schematic illustration of the nanostructured coating during plasma-spraying of agglomerated nanostructured based powders. (<b>a</b>) Partially molten particles. (<b>b</b>) Fully molten particles.</p> Full article ">
14 pages, 5643 KiB  
Article
Surface Activation and Characterization of Aluminum Alloys for Brazing Optimization
by Sara Ferraris, Sergio Perero and Graziano Ubertalli
Coatings 2019, 9(7), 459; https://doi.org/10.3390/coatings9070459 - 23 Jul 2019
Cited by 8 | Viewed by 5398
Abstract
Brazing of Al-alloys is of interest in many application fields (e.g., mechanical and automotive). The surface preparation of substrates and the in depth investigation of the interface reaction between aluminum substrates and brazing materials is fundamental for a proper understanding of the process [...] Read more.
Brazing of Al-alloys is of interest in many application fields (e.g., mechanical and automotive). The surface preparation of substrates and the in depth investigation of the interface reaction between aluminum substrates and brazing materials is fundamental for a proper understanding of the process and for its optimization. The interaction between two aluminum based substrates (Al5182 and Al6016) and two studied brazing materials (pure Zn and for the first time ZAMA alloy) has been studied in simulated brazing condition in order to define the best surface preparation conditions and combination substrate-brazing material to be used in real joining experiments. Three different surface preparations were considered: polishing and cleaning, application of flux and vacuum plasma etching (Ar) followed by sputtering coating with Zn. Macroscopic observation of the samples surface after “brazing”, optical microscopy, and microhardness measurements on the cross-section and XRD measurements on the top surface gave a comprehensive description of the phenomena occurring at the interface between the substrate and the brazing alloy which are of interest to understand the brazing process and for the detection of the best conditions to be used in brazing. Plasma etching (Ar) followed by sputtering coating with Zn resulted a promising solution in case of Al5182 brazed with Zn, while the addition of flux was more effective in case of Al6016 substrate. ZAMA alloy demonstrated good interface reactivity with both Al6016 and Al5182 alloys, particularly on only cleaned surfaces. Full article
(This article belongs to the Special Issue Surface Engineering of Light Alloys)
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Figure 1

Figure 1
<p>Scheme of the research setup and rationale.</p> Full article ">Figure 2
<p>Macroscopic appearance of samples before and after brazing. (<b>a</b>) Al5182 substrate and (<b>b</b>) Al6016 substrate. Scale bar: 1 cm.</p> Full article ">Figure 3
<p>Optical microscope images of the transverse section of the samples (no etching): (<b>a</b>) Zn as brazing material; (<b>b</b>) ZAMA as brazing material.</p> Full article ">Figure 4
<p>XRD spectra of the top surface of samples after the “spreading test”. (Zn as brazing material.): (<b>a</b>) Al 5182 substrate; (<b>b</b>) Al 6016 substrate.</p> Full article ">Figure 5
<p>XRD spectra of the top surface of samples after the “spreading test”. (ZAMA as brazing material.): (<b>a</b>) Al 5182 substrate; (<b>b</b>) Al 6016 substrate.</p> Full article ">Figure 6
<p>Field-emission scanning electron microscopy–energy-dispersive spectroscopy (FESEM-EDS) analyses of Al6016-flux-Zn. (<b>a</b>) Micrograph of the drop/reaction layer; (<b>b</b>) magnification of the reaction layer/interface; and (<b>c</b>) semiquantitative EDS analyses of selected area evidenced in panel (<b>b</b>).</p> Full article ">Figure 7
<p>FESEM-EDS analyses of Al5182 Zn-sput-Zn. (<b>a</b>) Micrograph of the reaction layer; (<b>b</b>) magnification of the reaction layer/interface; and (<b>c</b>) semiquantitative EDS analyses of selected areas evidenced in panel (<b>b</b>).</p> Full article ">Figure 8
<p>FESEM-EDS analyses of Al6016-ZAMA. (<b>a</b>) Micrograph of the reaction layer and (<b>b</b>) semiquantitative EDS analyses of selected areas evidenced in panel (<b>a</b>).</p> Full article ">Figure 9
<p>FESEM-EDS analyses of Al5182-ZAMA. (<b>a</b>) Low magnification micrograph of transverse section reaction/layer substrate interface; (<b>b</b>) high magnification of the reaction zone; and (<b>c</b>) semiquantitative EDS analyses of selected areas evidenced in panel (<b>b</b>).</p> Full article ">
14 pages, 8169 KiB  
Article
Mathematical Analysis of the Coating Process over a Porous Web Lubricated with Upper-Convected Maxwell Fluid
by Muhammad Zafar, Muhammad A. Rana, Muhammad Zahid and Babar Ahmad
Coatings 2019, 9(7), 458; https://doi.org/10.3390/coatings9070458 - 22 Jul 2019
Cited by 13 | Viewed by 4832
Abstract
The present study offers mathematical calculations of the roll-coating procedure lubricated with an upper-convected Maxwell fluid. An incompressible isothermal viscoelastic fluid was considered, with both the roll and the porous web having uniform velocities. By using the lubrication approximation theory, the desired equations [...] Read more.
The present study offers mathematical calculations of the roll-coating procedure lubricated with an upper-convected Maxwell fluid. An incompressible isothermal viscoelastic fluid was considered, with both the roll and the porous web having uniform velocities. By using the lubrication approximation theory, the desired equations of motion for the fluid applied to the porous web were modelled and analyzed. The suction rate on the web and the injection rate at the roll surface were proportionately anticipated. Results for the velocity profile and pressure gradient were received analytically. Fluid parameters of industrial significance (i.e., detachment point, pressure, sheet/roll separating force, power contribution, and coating thickness) were also calculated numerically. A substantial and monotonic increase was witnessed in these quantities with the increase of flow parameters. Full article
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Figure 1

Figure 1
<p>Sketch of the physical model under study.</p> Full article ">Figure 2
<p>Mathematical illustration of the region under study.</p> Full article ">Figure 3
<p>Influence of <span class="html-italic">B</span> on velocity profile at <span class="html-italic">x</span> = 0. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.3050..1.4522</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.4789..1.5590</mn> </mrow> </semantics></math>.</p> Full article ">Figure 4
<p>Influence of <span class="html-italic">B</span> on velocity profile at <span class="html-italic">x</span> = 0.25. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.3050..1.4522</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.4789..1.5590</mn> </mrow> </semantics></math>.</p> Full article ">Figure 5
<p>Influence of <span class="html-italic">B</span> on velocity profile at <span class="html-italic">x</span> = 0.5. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.3050..1.4522</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.4789..1.5590</mn> </mrow> </semantics></math>.</p> Full article ">Figure 6
<p>Influence of <span class="html-italic">B</span> on velocity profile at <span class="html-italic">x</span> = 0.75. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.3050..1.4522</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.4789..1.5590</mn> </mrow> </semantics></math>.</p> Full article ">Figure 7
<p>Influence of <span class="html-italic">B</span> on velocity profile at <span class="html-italic">x</span> = 1. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.3050..1.4522</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.4789..1.5590</mn> </mrow> </semantics></math>.</p> Full article ">Figure 8
<p>Influence of Re on velocity profile at <span class="html-italic">x</span> = 0. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.2027..1.0721</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.0271..0.9332</mn> </mrow> </semantics></math>.</p> Full article ">Figure 9
<p>Influence of Re on velocity profile at <span class="html-italic">x</span> = 0.25. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.2027..1.0721</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.0271..0.9332</mn> </mrow> </semantics></math>.</p> Full article ">Figure 10
<p>Influence of Re on velocity profile at <span class="html-italic">x</span> = 0.5. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.2027..1.0721</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.0271..0.9332</mn> </mrow> </semantics></math>.</p> Full article ">Figure 11
<p>Influence of Re on velocity profile at <span class="html-italic">x</span> = 0.75. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.2027..1.0721</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.0271..0.9332</mn> </mrow> </semantics></math>.</p> Full article ">Figure 12
<p>Influence of Re on velocity profile at <span class="html-italic">x</span> = 1. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.2027..1.0721</mn> </mrow> </semantics></math>, (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>1.0271..0.9332</mn> </mrow> </semantics></math>.</p> Full article ">Figure 13
<p>Axial distribution of the pressure gradient by fixing <span class="html-italic">B</span> = 10.</p> Full article ">Figure 14
<p>Axial distribution of the pressure gradient by fixing Re = 10.</p> Full article ">Figure 15
<p>Axial distribution of dimensional pressure fixing Re = 10.</p> Full article ">Figure 16
<p>Axial distribution of dimensional pressure by fixing <span class="html-italic">B</span> = 10.</p> Full article ">
28 pages, 82381 KiB  
Article
Extrusion Coating of Paper with Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)—Packaging Related Functional Properties
by Sven Sängerlaub, Marleen Brüggemann, Norbert Rodler, Verena Jost and Klaus Dieter Bauer
Coatings 2019, 9(7), 457; https://doi.org/10.3390/coatings9070457 - 22 Jul 2019
Cited by 25 | Viewed by 7860
Abstract
Taking into account the current trend for environmentally friendly solutions, paper coated with a biopolymer presents an interesting field for future packaging applications. This study covers the application of the biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) on a paper substrate via extrusion coating. The intention of [...] Read more.
Taking into account the current trend for environmentally friendly solutions, paper coated with a biopolymer presents an interesting field for future packaging applications. This study covers the application of the biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) on a paper substrate via extrusion coating. The intention of this study is to analyse the effect of a plasticiser on the processability (melting point, film thickness) and the final properties (crystallinity, elongation at break) of PHBV. Up to 15 wt.% of the plasticisers triethyl citrate (TEC) and polyethylene glycol (PEG) were used as additive. The processing (including melt flow rate) as well as the structural properties (melting and crystallisation temperature, surface structure by atomic force microscopy (AFM), polarisation microscopy, scanning electron microscopy (SEM)), mechanical properties (elongation at break, tensile strength, elastic modulus, adhesion), and barrier properties (grease) of these blends and their coating behaviour (thickness on paper), were tested at different extrusion temperatures. The melting temperature (Tm) of PHBV was reduced by the plasticisers (from 172 °C to 164 resp. 169 °C with 15 wt.% TEC resp. PEG). The minimal achieved PHBV film thickness on paper was 30 µm owing to its low melt strength. The elastic modulus decreased with both plasticisers (from 3000 N/mm2 to 1200 resp. 1600 N/mm2 with 15 wt.% TEC resp. PEG). At 15 wt.% TEC, the elongation at break increased to 2.4 length-% (pure PHBV films had 0.9 length-%). The grease barrier (staining) was low owing to cracks in the PHBV layers. The extrusion temperature correlated with the grease barrier, mechanical properties, and bond strength. The bond strength was higher for films extruded with a temperature profile for constant melt flow rate at different plasticiser concentrations. The bond strength was max. 1.2 N/15 mm. Grease staining occurs because of cracks induced by the low elongation at break and high brittleness. Extrusion coating of the used specific PHBV on paper is possible. In further studies, the minimum possible PHBV film thickness needs to be reduced to be cost-effective. The flexibility needs to be increased to avoid cracks, which cause migration and staining. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Melting temperatures of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and PHBV with different concentrations of plasticizers. PEG: polyethylene glycol, TEC: triethyl citrate.</p> Full article ">Figure 2
<p>Crystallisation temperature of PHBV and PHBV with different concentrations of plasticizers. PEG: polyethylene glycol, TEC: triethyl citrate.</p> Full article ">Figure 3
<p>Crystallinity as function of time of PHBV layers blended with TEC: (<b>a</b>) temperature (T) during extrusion constant; (<b>b</b>) melt flow rate (MFR) during extrusion constant.</p> Full article ">Figure 4
<p>Crystallinity as function of time of PHBV layers blended with PEG: (<b>a</b>) temperature (T) during extrusion constant; (<b>b</b>) melt flow rate (MFR) during extrusion constant.</p> Full article ">Figure 5
<p>First and second heating cycle of a differential scanning calorimetry (DSC) measurement.</p> Full article ">Figure 6
<p>Melt flow rate of PHBV: (<b>a</b>) blended with PEG; (<b>b</b>) blended with TEC.</p> Full article ">Figure 7
<p>Tensile strength as function plasticizer concentration: (<b>a</b>) of triethyl citrate (TEC) concentration; (<b>b</b>) of polyethylene glycol (PEG) concentration. Comparison with results of Jost. MFR: melt flow rate during extrusion; T: temperature during extrusion.</p> Full article ">Figure 7 Cont.
<p>Tensile strength as function plasticizer concentration: (<b>a</b>) of triethyl citrate (TEC) concentration; (<b>b</b>) of polyethylene glycol (PEG) concentration. Comparison with results of Jost. MFR: melt flow rate during extrusion; T: temperature during extrusion.</p> Full article ">Figure 8
<p>Elongation at break as function of plasticizer concentration: (<b>a</b>) of TEC; (<b>b</b>) of PET. Comparison with results of Jost. MFR: melt flow rate during extrusion; T: temperature during extrusion.</p> Full article ">Figure 8 Cont.
<p>Elongation at break as function of plasticizer concentration: (<b>a</b>) of TEC; (<b>b</b>) of PET. Comparison with results of Jost. MFR: melt flow rate during extrusion; T: temperature during extrusion.</p> Full article ">Figure 9
<p>Elastic modulus as function of plasticizer concentration: (<b>a</b>) of triethyl citrate (TEC) concentration; (<b>b</b>) of polyethylene glycol (PEG) concentration. Comparison with results of Jost. MFR: melt flow rate during extrusion; T: temperature during extrusion.</p> Full article ">Figure 9 Cont.
<p>Elastic modulus as function of plasticizer concentration: (<b>a</b>) of triethyl citrate (TEC) concentration; (<b>b</b>) of polyethylene glycol (PEG) concentration. Comparison with results of Jost. MFR: melt flow rate during extrusion; T: temperature during extrusion.</p> Full article ">Figure 10
<p>Elongation at break versus elastic modulus as function of plasticizer concentration: (<b>a</b>) of TEC; (<b>b</b>) of PEG. Comparison with results of Jost. MFR: melt flow rate during extrusion; T: temperature during extrusion.</p> Full article ">Figure 10 Cont.
<p>Elongation at break versus elastic modulus as function of plasticizer concentration: (<b>a</b>) of TEC; (<b>b</b>) of PEG. Comparison with results of Jost. MFR: melt flow rate during extrusion; T: temperature during extrusion.</p> Full article ">Figure 11
<p>Bond strength of PHBV layers blended with plasticizer on paper: (<b>a</b>) of triethyl citrate (TEC); (<b>b</b>) of polyethylene glycol (PEG). Plasticizer concentration 0, 2, 5, 10, 15 wt.%; coating velocity: 1.6 and 4 m/min. MD: machine direction; CD: cross direction; MFR: melt flow rate during extrusion; T: temperature during extrusion, numbers above the bars: thickness in µm.</p> Full article ">Figure 12
<p>Raman spectra of samples.</p> Full article ">Figure 13
<p>Raman spectra of PHBV with 15 wt.% PEG at different sample depths.</p> Full article ">Figure 14
<p>Grease barrier (staining) of paper coated with PHBV layers blended with triethyl citrate (TEC): (<b>a</b>) temperature (T) during extrusion constant; (<b>b</b>) melt flow rate (MFR) during extrusion constant. Thickness: PHBV thickness.</p> Full article ">Figure 15
<p>Grease barrier (staining) of paper coated with PHBV layers blended with polyethylene glycol (PEG): (<b>a</b>) temperature (T) during extrusion constant; (<b>b</b>) melt flow rate (MFR) during extrusion constant. Thickness: PHBV thickness.</p> Full article ">Figure 16
<p>Roughnesses of PHBV layers blended with triethyl citrate (TEC), constant MFR (melt flow rate during extrusion).</p> Full article ">Figure 17
<p>Atomic force microscopy (AFM) measurements of PHBV film with 15 wt.% PEG. <b>left</b>, extrusion temperature: 176 °C (MFR = const.); <b>right</b>, extrusion temperature: 185 °C (T = const.).</p> Full article ">Figure 18
<p>Scanning electron microscopy (SEM) pictures of pure PHBV film with defects (marked in red). <b>Left</b>: magnification ×1000, <b>right</b>: magnification ×500; red ellipse: cracks in the layer.</p> Full article ">
11 pages, 4383 KiB  
Article
Predictability of Microbial Adhesion to Dental Materials by Roughness Parameters
by Andrea Schubert, Torsten Wassmann, Mareike Holtappels, Oliver Kurbad, Sebastian Krohn and Ralf Bürgers
Coatings 2019, 9(7), 456; https://doi.org/10.3390/coatings9070456 - 22 Jul 2019
Cited by 39 | Viewed by 4828
Abstract
Microbial adhesion to intraoral biomaterials is associated with surface roughness. For the prevention of oral pathologies, smooth surfaces with little biofilm formation are required. Ideally, appropriate roughness parameters make microbial adhesion predictable. Although a multitude of parameters are available, surface roughness is commonly [...] Read more.
Microbial adhesion to intraoral biomaterials is associated with surface roughness. For the prevention of oral pathologies, smooth surfaces with little biofilm formation are required. Ideally, appropriate roughness parameters make microbial adhesion predictable. Although a multitude of parameters are available, surface roughness is commonly described by the arithmetical mean roughness value (Ra). The present study investigates whether Ra is the most appropriate roughness parameter in terms of prediction for microbial adhesion to dental biomaterials. After four surface roughness modifications using standardized polishing protocols, zirconia, polymethylmethacrylate, polyetheretherketone, and titanium alloy specimens were characterized by Ra as well as 17 other parameters using confocal microscopy. Specimens of the tested materials were colonized by C. albicans or S. sanguinis for 2 h; the adhesion was measured via luminescence assays and correlated with the roughness parameters. The adhesion of C. albicans showed a tendency to increase with increasing the surface roughness—the adhesion of S. sanguinis showed no such tendency. Although Sa, that is, the arithmetical mean deviation of surface roughness, and Rdc, that is, the profile section height between two material ratios, showed higher correlations with the microbial adhesion than Ra, these differences were not significant. Within the limitations of this in-vitro study, we conclude that Ra is a sufficient roughness parameter in terms of prediction for initial microbial adhesion to dental biomaterials with polished surfaces. Full article
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<p>Confocal images of the tested materials standardized zirconia (YTZP), polymethylmethacrylate (PMMA), polyetheretherketone (PEEK), and titanium alloy (Ti) at the four roughness levels (I–IV) for 500 µm × 500 µm scan areas; <span class="html-italic">Z</span> = z-axis dimension.</p> Full article ">Figure 2
<p>Relative adhesion of (<b>a</b>) <span class="html-italic">C. albicans</span> and (<b>b</b>) <span class="html-italic">S. sanguinis</span> to the test groups at four different roughness levels after 2 h of incubation. Levels of relative luminescence intensities from the adenosine triphosphate (ATP) assays correlate to the number of viable cells; relative luminescence intensities are shown logarithmized. Bars labeled with identical letters are significantly different at α = 0.05.</p> Full article ">Figure 3
<p>Correlation matrix for representative roughness parameters with scatterplots of the roughness values. <span class="html-italic">S<sub>a</sub></span>, <span class="html-italic">R<sub>dc</sub></span>, and <span class="html-italic">R<sub>z</sub></span> are positively correlated with each other and with <span class="html-italic">R<sub>a</sub></span>; <span class="html-italic">R<sub>mr</sub></span> and <span class="html-italic">S<sub>sk</sub></span> show no linear correlation with <span class="html-italic">R<sub>a</sub></span> or any of the other shown parameters. <span class="html-italic">r</span> = Pearson correlation coefficient; <span class="html-italic">p</span> = <span class="html-italic">p</span>-value; <span class="html-italic">p</span>. adj = Bonferroni-adjusted <span class="html-italic">p</span>-value.</p> Full article ">
11 pages, 24752 KiB  
Article
In Situ Preparation and Corrosion Resistance of a ZrO2 Film on a ZrB2 Ceramic
by Haitao Yang, Jian Zhang, Junguo Li, Qiang Shen and Lianmeng Zhang
Coatings 2019, 9(7), 455; https://doi.org/10.3390/coatings9070455 - 21 Jul 2019
Cited by 5 | Viewed by 3279
Abstract
ZrO2 films were in situ prepared using the anodic passivation of a ZrB2 ceramic in alkaline solutions. The composition and structure of the films were characterized using field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The corrosion [...] Read more.
ZrO2 films were in situ prepared using the anodic passivation of a ZrB2 ceramic in alkaline solutions. The composition and structure of the films were characterized using field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The corrosion resistances were evaluated in 0.1 M oxalate solution using the potentiodynamic polarization method (PDP) and the electrochemical impedance spectroscopy (EIS) technique. The results show that ZrO2 films can be prepared using anodization from −0.8 to 0.8 V standard hydrogen electrode (SHE) in 2–16 M NaOH solutions. During the anodization, the dehydration reaction of Zr(OH)4 to ZrO2 caused the volume shrinkage and tensile stress of the films. When the thickness of the films exceeded a critical value, the mud-cracking morphology occurred. The films without cracks exhibited the inhibition effect and provided effective corrosion protection in a 0.1 M H2C2O4 solution, which had a positive correlation with the film thickness. The film obtained when put in an 8 M NaOH solution (near the critical thickness) was found to significantly improve its corrosion resistance when put in a 0.1 M H2C2O4 solution by almost one order of magnitude compared with the bare ceramic. Full article
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<p>PDP curves for the ZrB<sub>2</sub> ceramic in 2–16 M NaOH solutions at 40 °C.</p> Full article ">Figure 2
<p>Surface and cross-section morphology of the films obtained using potentiostatic anodization at 0 V for 10 min in (<b>a</b>,<b>f</b>) 6 M, (<b>b</b>,<b>g</b>) 8 M, (<b>c</b>,<b>h</b>) 10 M, (<b>d</b>,<b>i</b>) 12 M, and (<b>e</b>,<b>j</b>) 14 M NaOH solution.</p> Full article ">Figure 3
<p>Surface morphology of the anodic film obtained using potentiostatic anodization at 0 V for 10 min without the OCP test process when put in a 6 M NaOH solution.</p> Full article ">Figure 4
<p>Raman spectra of the anodic film obtained using potentiostatic anodization when put in a 10 M NaOH solution at 0 V for 10 min.</p> Full article ">Figure 5
<p>B 1<span class="html-italic">s</span> and Zr 3<span class="html-italic">d</span> XPS spectra for the anodic film obtained using potentiostatic anodization at 0 V for 10 min in 10 M NaOH solution.</p> Full article ">Figure 6
<p>Optical image of the anodic film obtained using potentiostatic anodization when put in a 14 M NaOH solution at 0 V for 10 min without a drying process.</p> Full article ">Figure 7
<p>PDP curves of the anodic films in 0.1 M H<sub>2</sub>C<sub>2</sub>O<sub>4</sub> solution at 40 °C where the substrate (bare sample) is listed for comparison. The films were prepared using potentiostatic anodization in different NaOH solutions at 0 V for 10 min.</p> Full article ">Figure 8
<p>The <span class="html-italic">i</span><sub>corr</sub> and <span class="html-italic">E</span><sub>corr</sub> of the anodic films put in a 0.1 M H<sub>2</sub>C<sub>2</sub>O<sub>4</sub> solution at 40 °C calculated using the Tafel extrapolation method based on <a href="#coatings-09-00455-f007" class="html-fig">Figure 7</a>.</p> Full article ">Figure 9
<p>EIS results of the anodic films of ZrB<sub>2</sub> ceramic when put in a 0.1 M H<sub>2</sub>C<sub>2</sub>O<sub>4</sub> solution (40 °C) at OCP: (<b>a</b>) Nyquist plots, (<b>b</b>) Bode impedance magnitude plots, (<b>c</b>) Bode phase angle plots, (<b>d</b>,<b>e</b>) equivalent circuit for the substrate and the anodic films, and (<b>f</b>) the <span class="html-italic">R</span><sub>t</sub> of the substrate and the films.</p> Full article ">
16 pages, 2549 KiB  
Article
Surface Modification of Hemoglobin-Based Oxygen Carriers Reduces Recognition by Haptoglobin, Immunoglobulin, and Hemoglobin Antibodies
by Ausanai Prapan, Nittiya Suwannasom, Chiraphat Kloypan, Saranya Chaiwaree, Axel Steffen, Yu Xiong, Ijad Kao, Axel Pruß, Radostina Georgieva and Hans Bäumler
Coatings 2019, 9(7), 454; https://doi.org/10.3390/coatings9070454 - 21 Jul 2019
Cited by 7 | Viewed by 5218
Abstract
Hemoglobin-based oxygen carriers (HBOCs) represent a propitious type of blood substitute to transport oxygen throughout the body while acting as a carrier in biomedical applications. However, HBOCs in blood are recognized and rapidly scavenged by the body’s innate immune systems. To overcome this [...] Read more.
Hemoglobin-based oxygen carriers (HBOCs) represent a propitious type of blood substitute to transport oxygen throughout the body while acting as a carrier in biomedical applications. However, HBOCs in blood are recognized and rapidly scavenged by the body’s innate immune systems. To overcome this problem, HBOCs require a surface modification that provides protection against detection and elimination in order to prolong their circulation time after administration. In this study, we investigated different surface modifications of hemoglobin submicron particles (HbMPs) by double/triple precipitation, as well as by adsorption of human serum albumin (HSA), hyaluronic acid (HA), and pluronic (Plu) to discover how diverse surface modifications influence the oxygen binding capacity and the binding of anti-hemoglobin (Hb) antibodies, immunoglobulin G (IgG), and haptoglobin (HP) to HbMPs. The particle size and zeta potential of the six types of HbMP modifications were analyzed by zeta sizer, confocal laser scanning microscopy, and transmission electron microscopy (TEM), and were compared to the unmodified HbMPs. The results revealed that all surface-modified HbMPs had a submicron size with a negative charge. A slight decrease in the oxygen binding capacity was noticed. The specific binding of anti-Hb antibodies, IgG, and HP to all surface-modified HbMPs was reduced. This indicates a coating design able to protect the particles from detection and elimination processes by the immune system, and should lead to a delayed clearance and the required and essential increase in half-life in circulation of these particles in order to fulfill their purpose. Our surface modification method reflects a promising strategy for submicron particle design, and can lead the way toward novel biomedical applications. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Fabrication scheme of surface-modified hemoglobin submicron particles (HbMPs) by triple precipitation in presence of polymers (human serum albumin (HSA), hyaluronic acid (HA), or pluronic (Plu)). For fabrication of the double precipitated surface-modified HbMP, the particles were dissolved with ethylene-diaminetetraacetic acid (EDTA) after the second crosslinking step.</p> Full article ">Figure 2
<p>Transmission electron microscope (TEM) images (scale bar: 100 nm) together with confocal laser scanning microscope (CLSM) imaging (inserts, scale bar: 5 µm) of unmodified hemoglobin submicron particles (HbMPs) (<b>A</b>), double precipitated HbMPs (HSA-d-HbMPs) (<b>B</b>), and triple precipitated HbMPs (HSA-t-HbMPs) (<b>C</b>).</p> Full article ">Figure 3
<p>The hydrodynamic diameter (<b>A</b>) and zeta-potential (<b>B</b>) of the surface-modified HbMPs. Data are presented as mean ± SD (<span class="html-italic">n</span> = 3). ’’NS’’ indicates not significant, whereas the asterisk indicates a significant difference when compared to HbMPs (* <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 4
<p>The Hb (<b>A</b>) and oxygenated Hb (Oxy-Hb) (<b>B</b>) content of surface-modified HbMPs as calculated for a suspension with an Hct of 20%. Data are represented as mean ± SD (<span class="html-italic">n</span> = 3). ’’NS’’ indicates not significant, whereas the asterisk indicates a significant difference when compared to HbMPs (* <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 5
<p>Immunofluorescence assay with rabbit anti-bovine-Hb antibodies. (<b>A</b>) Schematic drawing representing a model of indirect immunofluorescence staining with anti-Hb antibodies. (<b>B</b>) The % positive events of non-specific and specific binding of anti-Hb antibodies on each surface-modified HbMP. Specific binding was calculated by subtracting the non-specific binding from the total binding. Data represent the mean ± SD, and asterisks indicate the significance of differences when compared to HbMPs (* <span class="html-italic">p</span> &lt; 0.05). Representative histograms show examples of flowcytometric analysis of anti-Hb antibodies binding on HbMPs (<b>C</b>), HSA-d-HbMPs (<b>D</b>) and HSA-t-HbMPs (<b>E</b>). Gray areas represent the histograms of particles that were not exposed to antibodies. Dash lines are histograms of particles with only secondary antibodies staining, as a non-specific binding. The solid lines are the histograms of particles with both primary and secondary antibody staining, as a total binding.</p> Full article ">Figure 6
<p>Immunofluorescence assay of the binding of IgG (biotinylated) to surface-modified HbMPs. (<b>A</b>) Schematic drawing representing the staining procedure with APC-Streptavidin. (<b>B</b>) The % positive events of non-specific and specific binding of APC-Streptavidin on each surface-modified HbMP. Specific binding was calculated by subtracting the non-specific binding from the total binding. Data represent the mean ± SD, and asterisks indicate the significance of differences when compared to HbMPs (* <span class="html-italic">p</span> &lt; 0.05). Representative histograms show examples of flowcytometric analysis of the binding of APC-Streptavidin on HbMPs (<b>C</b>), HSA-d-HbMPs (<b>D</b>) and HSA-t-HbMPs (<b>E</b>). Gray areas represent the histograms of particles that were not exposed to antibodies. Dash lines are histograms of particles with only APC-Streptavidin staining, as a non-specific binding. The solid lines are the histograms of particles with both biotinylated IgG and APC-Streptavidin staining, as a total binding.</p> Full article ">Figure 7
<p>Immunofluorescence assay of haptoglobin (HP) binding to surface-modified HbMPs. (<b>A</b>) Schematic drawing representing the staining procedure. (<b>B</b>) The % positive events of non-specific and specific binding of anti-HP antibodies on each surface-modified HbMP. Specific binding was calculated by subtracting the non-specific binding from the total binding. Data represent the mean ± SD, and asterisks indicate the significance of differences when compared to HbMPs (* <span class="html-italic">p</span> &lt; 0.05). Representative histograms show example of flowcytometric analysis of anti-HP antibodies binding on HbMP (<b>C</b>), HSA-d-HbMP (<b>D</b>) and HSA-t-HbMP (<b>E</b>) samples. Gray areas represent the histogram of particles that were not exposed to antibodies. Dash lines are histograms of particles with only anti-HP antibody staining, as a non-specific binding. The solid lines are the histograms of particles with both HP and anti-HP antibodies staining, as a total binding.</p> Full article ">
10 pages, 8548 KiB  
Article
Hybrid Nanostructured Antireflection Coating by Self-Assembled Nanosphere Lithography
by Zizheng Li, Chi Song, Qiang Li, Xiangjun Xiang, Haigui Yang, Xiaoyi Wang and Jinsong Gao
Coatings 2019, 9(7), 453; https://doi.org/10.3390/coatings9070453 - 18 Jul 2019
Cited by 19 | Viewed by 6910
Abstract
Broadband antireflection (AR) coatings are essential elements for improving the photocurrent generation of photovoltaic modules or the enhancement of visibility in optical devices. In this paper, we report a hybrid nanostructured antireflection coating combination that is a clean and efficient method for fabricating [...] Read more.
Broadband antireflection (AR) coatings are essential elements for improving the photocurrent generation of photovoltaic modules or the enhancement of visibility in optical devices. In this paper, we report a hybrid nanostructured antireflection coating combination that is a clean and efficient method for fabricating a nanostructured antireflection coating (ARC). A multilayer thin-film was introduced between the ARC and substrate to solve the significant problem of preparing nanostructured ARCs on different substrates. In this way, we rebuilt a gradient refractive index structure and optimize the antireflective property by simply adjusting the moth-eye structure and multilayers. Subwavelength-structured cone arrays were directly patterned using a self-assembled single-layer polystyrene (PS) nanosphere array as an etching mask. Nanostructure coatings exhibited excellent broadband and wide-angle antireflective properties. The bottom-up preparation process and hybrid structural combination have the potential to significantly enhance the broadband and wide-angle antireflective properties for a number of optical systems that require high transparency, which is promising for reducing the manufacturing cost of nanostructured AR coatings. Full article
(This article belongs to the Special Issue Photonic and Electronic Multilayer Thin Films: Growth, Properties, and Applications)
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<p>The relationships between height position and material refractive index of (<b>a</b>) a moth-eye SiO<sub>2</sub> AR structure on a sapphire substrate, and (<b>b</b>) a hybrid AR nanostructure on a sapphire substrate.</p> Full article ">Figure 2
<p>Schematic diagram of the process used to fabricate the hybrid AR nanostructures including multilayer deposition, nanosphere self-assembly, nanosphere size reduction, reactive ion beam etching, and cleaning.</p> Full article ">Figure 3
<p>Schematic diagrams of a nanocone array under different viewing angles: (<b>a</b>) 3D image, (<b>b</b>) cross-section, and (<b>c</b>) top view. The computer simulations investigating the influence of structural parameters: (<b>d</b>) height, (<b>e</b>) separation distance, and (<b>f</b>) diameter of nanocone array on the surface reflectance.</p> Full article ">Figure 4
<p>SEM photograph of self-assembled PS-nanosphere masks magnified (<b>a</b>) 7000 times and (<b>b</b>) 4000 times, (<b>c</b>) 2D and (<b>d</b>) 3D AFM images of etched SiO<sub>2</sub> nanocone arrays without a size-reduction procedure, and (<b>e</b>) surface reflectance of a prepared SiO<sub>2</sub> nanocone array.</p> Full article ">Figure 5
<p>SEM images of self-assembled nanosphere masks after (<b>a</b>) 5 s, (<b>b</b>) 10 s, and (<b>c</b>) 15 s size-reduction processes. The SiO<sub>2</sub> nanocone arrays after etching process with different size-reduced PS nanospheres mask that used (<b>d</b>) 5 s, (<b>e</b>) 10 s, and (<b>f</b>) 15 s etching times.</p> Full article ">Figure 6
<p>(<b>a</b>) 2D and (<b>b</b>) 3D AFM images of the hybrid nanostructure surface; (<b>c</b>) Surface reflectance of the prepared nanocone array without a multilayer thin-film; (<b>d</b>) Surface reflectance of the prepared hybrid nanostructure at different incident angles.</p> Full article ">Figure 7
<p>(<b>a</b>) A higher-resolution surface 3D image of a nanocone array, (<b>b</b>) a surface profile of a hybrid AR nanostructure surface, (<b>c</b>) cross-sectional SEM image of a SiO<sub>2</sub> layer and multilayer AR coating before etching, and (<b>d</b>) cross-sectional SEM image of a hybrid AR nanostructure.</p> Full article ">Figure 8
<p>(<b>a</b>) The surface reflectance of a hybrid AR nanostructure compared with a sapphire substrate, and (<b>b</b>) the surface reflectance of a hybrid AR nanostructure at different incident angles.</p> Full article ">
28 pages, 8631 KiB  
Review
Robust Super-Hydrophobic Coating Prepared by Electrochemical Surface Engineering for Corrosion Protection
by Peng Bi, Hongliang Li, Guochen Zhao, Minrui Ran, Lili Cao, Hanjie Guo and Yanpeng Xue
Coatings 2019, 9(7), 452; https://doi.org/10.3390/coatings9070452 - 18 Jul 2019
Cited by 48 | Viewed by 12743
Abstract
Corrosion—reactions occuring between engineering materials and their environment—can cause material failure and catastrophic accidents, which have a serious impact on economic development and social stability. Recently, super-hydrophobic coatings have received much attention due to their effectiveness in preventing engineering materials from further corrosion. [...] Read more.
Corrosion—reactions occuring between engineering materials and their environment—can cause material failure and catastrophic accidents, which have a serious impact on economic development and social stability. Recently, super-hydrophobic coatings have received much attention due to their effectiveness in preventing engineering materials from further corrosion. In this paper, basic principles of wetting properties and corrosion protection mechanism of super-hydrophobic coatings are introduced firstly. Secondly, the fabrication methods by electrochemical surface engineering—including electrochemical anodization, micro-arc oxidation, electrochemical etching, and deposition—are presented. Finally, the stabilities and future directions of super-hydrophobic coatings are discussed in order to promote the movement of such coatings into real-world applications. The objective of this review is to bring a brief overview of the recent progress in the fabrication of super-hydrophobic coatings by electrochemical surface methods for corrosion protection of engineering materials. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)
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<p>Schematic of a liquid droplet on solid surface. (<b>a</b>) Young’s wetting state; (<b>b</b>) Wenzel wetting state; (<b>c</b>) Cassie–Baxter wetting state.</p> Full article ">Figure 2
<p>Schematic image of anti-corrosion using a super-hydrophobic surface. The super-hydrophobic micro/nanostructures keep surface wettability in ‘Cassie State’ to prevent corrosive medium penetrating the air layer and contacting with the substrate.</p> Full article ">Figure 3
<p>(<b>a</b>) Growth process of anodic aluminum nanofibers and nanofiber-tangled intermetallic particles; (<b>b</b>) SEM of samples anodized for t<sub>a</sub> = 2 min, 4 min, 10 min, and 30 min, respectively. Reprinted from [<a href="#B66-coatings-09-00452" class="html-bibr">66</a>], Copyright (2017), with permission from Elsevier.</p> Full article ">Figure 4
<p>(<b>a</b>) Scheme of the preparation and evaluation of SHPL and SHPB surface by high-speed hard anodization; (<b>b</b>) SEM images of the <span class="html-italic">Dianthus caryophyllus</span>-like structure; (<b>c</b>) Nyquist plots and fittings of EP surface, SHPL surface, and SHPB surface; (<b>d</b>) The variations of WCAs and sliding angels of the SHPB surface under hot water droplets with different temperatures. Reprinted from [<a href="#B29-coatings-09-00452" class="html-bibr">29</a>], Copyright (2017), with permission from Elsevier.</p> Full article ">Figure 5
<p>Mechanical stability and corrosion resistance evaluation of the PDES-MS surface: (<b>a</b>) Surface morphologies of the PDES-MS surface before and after abrasion test for 10, 30, and 50 cycles with sandpaper; (<b>b</b>) The variations of WCAs and WSAs under different ultrasonication time; (<b>c</b>) Variations of WCAs and WSAs of the PDES-MS surface after abrasion tests; (<b>d</b>) Potentiodynamic polarization curves of the unmodified and modified surfaces in 3.5 wt % NaCl solution. Reprinted with permission from [<a href="#B67-coatings-09-00452" class="html-bibr">67</a>]. Copyright (2014) American Chemical Society.</p> Full article ">Figure 6
<p>(<b>a</b>,<b>b</b>) Nyquist and Bode plots for the super-hydrophobic Ti surface and bare Ti substrate, respectively; (<b>c</b>) Polarization curves of super-hydrophobic Ti surface and bare Ti substrate. Reprinted from [<a href="#B70-coatings-09-00452" class="html-bibr">70</a>]. Copyright (2017), with permission from MDPI AG.</p> Full article ">Figure 7
<p>(<b>a</b>) Schematic of the electrodeposition process of MAO/ZnSA coating; (<b>b</b>) Macro-photographs and SEM images of Mg-4Li-1Ca substrate, MAO and MAO/ZnSA coating. The inserted are corresponding contact angles of each surface. Reprinted from [<a href="#B75-coatings-09-00452" class="html-bibr">75</a>]. Copyright (2017), with permission from Elsevier.</p> Full article ">Figure 8
<p>(<b>a</b>) Cross-view image of the MAO/SA 7h coating; (<b>b</b>) Polarization curves of the AZ31 substrate and the MAO coatings before and after modification with SA in 3.5 wt % NaCl solution. Reprinted from [<a href="#B76-coatings-09-00452" class="html-bibr">76</a>], Copyright (2017), with permission from Elsevier.</p> Full article ">Figure 9
<p>(<b>a</b>) Surface morphologies and inserted corresponding contact angles of the MAO coatings modified for 0, 1, 3, 5, and 10 h; (<b>b</b>) Potentiodynamic polarization curves of bare AZ31 Mg alloy and MAO coatings modified for different times; (<b>c</b>) EIS results and fitting curves for uncoated AZ31 Mg alloy, MAO coating, and H-MAO coating in 3.5 wt % NaCl solution. Reprinted from [<a href="#B74-coatings-09-00452" class="html-bibr">74</a>], Copyright (2015), with permission from Elsevier.</p> Full article ">Figure 10
<p>(<b>a</b>,<b>b</b>) Variations on contact angles and potentiodynamic polarization curves of the Ti-6Al-4V, MAO and MAO + PFOTS samples; (<b>c</b>) The morphologies of platelets adhered on the surface of the obtained samples. Reprinted from [<a href="#B77-coatings-09-00452" class="html-bibr">77</a>], Copyright (2015), with permission from Elsevier.</p> Full article ">Figure 11
<p>(<b>a</b>–<b>c</b>) Images of water droplets on the surface of superoleophobic Ti surface, super-hydrophobic Ti surface, and unprocessed Ti surface, respectively; (<b>d</b>) Variations in contact angles of super-oleophobic and super-hydrophobic Ti surface. Reprinted with permission from [<a href="#B78-coatings-09-00452" class="html-bibr">78</a>]. Copyright (2013) American Chemical Society.</p> Full article ">Figure 12
<p>(<b>a</b>) Scheme of electrochemical etching method. (<b>b</b>) Surface morphologies of AR-SS316L and NT-SS316L surfaces. The scale bar of the inset image is 200 nm. (<b>c</b>) Potentiodynamic polarization curves of AR-SS316L and NT-SS316L specimens in Hank’s balanced salt solution. Reprinted from [<a href="#B80-coatings-09-00452" class="html-bibr">80</a>]. Copyright (2017), with permission from American Chemical Society.</p> Full article ">Figure 13
<p>(<b>a</b>) SEM images and corresponding WCAs of the super-hydrophobic surfaces with various electrodeposition times: 1, 5, 10, 20, 30, and 60 min; (<b>b</b>,<b>c</b>) Potentiodynamic polarization curves and Nyquist plots of the untreated and super-hydrophobic Mg alloy surfaces in 3.5 wt % NaCl solution; (<b>d</b>) Schematic of the abrasion test and contact angles of the super-hydrophobic surface as a function of abrasion length. Reprinted with permission from [<a href="#B11-coatings-09-00452" class="html-bibr">11</a>]. Copyright (2015), American Chemical Society.</p> Full article ">Figure 14
<p>(<b>a</b>) Schematic of the electrochemical deposition process; (<b>b</b>) SEM images and contact angle of super-hydrophobic Ni (Ni-III) surface; (<b>c</b>–<b>e</b>) SEM images and contact angle of the super-hydrophobic surface (c) before and after abrasion for 1.0 m at applied pressure of (<b>d</b>) 2.4 kPa and (<b>e</b>) 6.0 kPa; (<b>f</b>,<b>g</b>) Potentiodynamic polarization curves and Nyquist plots of Cu substrate, electrodeposited Ni and the super-hydrophobic surface in 3.5 wt % NaCl solution. Reprinted with permission from [<a href="#B60-coatings-09-00452" class="html-bibr">60</a>]. Copyright (2014) American Chemical Society.</p> Full article ">Figure 15
<p>(<b>a</b>) SEM morphologies and WCAs of electrodeposited Cu fabricated at overpotentials of 0.5 V, 0.7 V, 0.9 V, and 1.1 V; (<b>b</b>) Potentiodynamic polarization curves for super-hydrophobic and base Cu in 3.5 wt % NaCl solution; (<b>c</b>) Schematic of the shear abrasion test setup; (<b>d</b>) SEM morphologies of super-hydrophobic sample before and after abrasion test. Reprinted (adapted) with permission from [<a href="#B84-coatings-09-00452" class="html-bibr">84</a>]. Copyright (2018) American Chemical Society.</p> Full article ">Figure 16
<p>Linear abrasion test. (<b>a</b>) A water droplet rolls on a nonwetting surface; (<b>b</b>) The setup and process of linear abrasion test; (<b>c</b>) The structures are worn out after linear abrasion cause that the surface may lose water repellent property. Adapted with permission from. Reprinted from [<a href="#B90-coatings-09-00452" class="html-bibr">90</a>], Copyright (2016), with permission from AAAS.</p> Full article ">Figure 17
<p>(<b>a</b>,<b>b</b>) Effect of abrasion length on WCA of Ni-PTFE composite coatings and CSHST coatings under 400 and 800 grit SiC papers, respectively. Reprinted from [<a href="#B95-coatings-09-00452" class="html-bibr">95</a>], Copyright (2017), with permission from Elsevier; (<b>c</b>–<b>e</b>) SEM images and inserted profiles of a water droplet for super-hydrophobic Co–Ni coating before abrasion and after abrasion wear of 6 m and 12 m under the applied pressure of 5 kPa, respectively; (<b>f</b>) Variations of the WCA and WSA on the tested surface with the abrasion distance [<a href="#B96-coatings-09-00452" class="html-bibr">96</a>]. Copyright (2019), with permission from MDPI AG.</p> Full article ">Figure 18
<p>(<b>a</b>) WCAs and WSAs vary by different UV exposure time on super-hydrophobic steel. Reprinted (adapted) with permission from [<a href="#B86-coatings-09-00452" class="html-bibr">86</a>]. Copyright (2015) American Chemical Society; (<b>b</b>) The thermal stability of transparent porous silica coating. Reproduced with permission from [<a href="#B106-coatings-09-00452" class="html-bibr">106</a>]. Copyright (2015), with permission from Royal Society of Chemistry.</p> Full article ">Figure 19
<p>(<b>a</b>) Schematic of the structure of the microcapsules and the self-healing mechanisms of the coating. Reprinted from [<a href="#B112-coatings-09-00452" class="html-bibr">112</a>] Copyright (2018), with permission from Elsevier; (<b>b</b>) Formation process of oil-containing graphene oxide microcapsules (GOMCs) and the processing of GOMCs/PU coatings. Reprinted from [<a href="#B113-coatings-09-00452" class="html-bibr">113</a>], Copyright (2017), with permission from Elsevier; (<b>c</b>,<b>d</b>) SEM images of self-healing coating before and after healing. Reprinted from [<a href="#B114-coatings-09-00452" class="html-bibr">114</a>], Copyright (2009), with permission from John Wiley and Sons.</p> Full article ">Figure 20
<p>(<b>a</b>) Schematics of the fabrication process of a SLIPS; (<b>b</b>) Schematics and time-lapse images showing the stability and displacement of SLIPs. Reprinted from [<a href="#B115-coatings-09-00452" class="html-bibr">115</a>], Copyright (2011), with permission from Springer Nature.</p> Full article ">
13 pages, 2443 KiB  
Article
The Influence of Polymer Blends on Regulating Chondrogenesis
by Aneel Bherwani, Chung-Chueh Chang, Gadi Pelled, Zulma Gazit, Dan Gazit, Miriam Rafailovich and Marcia Simon
Coatings 2019, 9(7), 451; https://doi.org/10.3390/coatings9070451 - 18 Jul 2019
Cited by 1 | Viewed by 2959
Abstract
The influence of polymer blend coatings on the differentiation of mouse mesenchymal stem cells was investigated. Polymer blending is a common means of producing new coating materials with variable properties. Stem cell differentiation is known to be influenced by both chemical and mechanical [...] Read more.
The influence of polymer blend coatings on the differentiation of mouse mesenchymal stem cells was investigated. Polymer blending is a common means of producing new coating materials with variable properties. Stem cell differentiation is known to be influenced by both chemical and mechanical properties of the underlying scaffold. We therefore selected to probe the response of stem cells cultured separately on two very different polymers, and then cultured on a 1:1 blend. The response to mechanical properties was probed by culturing the cells on polybutadiene (PB) films, where the film moduli was varied by adjusting film thickness. Cells adjusted their internal structure such that their moduli scaled with the PB films. These cells expressed chondrocyte markers (osterix (OSX), alkaline phosphatase (ALP), collagen X (COL-X), and aggrecan (ACAN)) without mineralizing. In contrast, cells on partially sulfonated polystyrene (PSS28) deposited large amounts of hydroxyapatite and expressed differentiation markers consistent with chondrocyte hypertrophy (OSX, ALP, COL-X, but not ACAN). Cells on phase-segregated PB and PSS28 films differentiated identically to those on PSS28, underscoring the challenges of using polymer templates for cell patterning in tissue engineering. Full article
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<p>Confocal microscopy of C9 grown for four days on 20 nm thick polybutadiene (PB), on 200 nm thick PB, or on partially (28%) sulfonated polystyrene (PSS28) in the presence (+) or absence (−) of doxycycline and then fixed and labeled with AlexaFluor<sup>®</sup> 488-phalloidin to visualize f-actin.</p> Full article ">Figure 2
<p>Comparison of relative moduli of C9 cells after 1- and 3-day incubation on 200 nm (gray) and 20 nm (black) PB films. <b>Left</b>: Cells overexpressing rhBMP2<sup>+</sup>. <b>Right</b>: Cells where rhBMP2<sup>−</sup> expression is suppressed.</p> Full article ">Figure 3
<p>(<b>A</b>) Relative moduli of C9 cells plated on sulfonated PSS<sub>28</sub> coated Si wafers with DOXY<sup>−</sup>/rhBMP2<sup>+</sup> medium (filled circles) and DOXY<sup>+</sup>/rhBMP2<sup>−</sup> (clear circles). (<b>B</b>) Topographical atomic force microscopy images of the extracellular matrix (ECM) fibers produced by the cells expressing (left) and not expressing BMP2 (right) after 6 days of incubation. Relative modulus of the ECM fibers (<b>C</b>) and interfiber spaces (<b>D</b>) are also shown.</p> Full article ">Figure 4
<p>C9 was grown on 20 nm PB (1), 200 nm PB (2), or PSS<sub>28</sub> (3) in DOXY<sup>+</sup>/rhBMP2<sup>−</sup> medium (a) or DOXY<sup>−</sup>/rhBMP2<sup>+</sup> medium (b) for 14 days. mRNA levels determined by qRT-PCR using primers for rhBMP2 (<b>A</b>), OSX (<b>B</b>), COL-X (<b>C</b>), ALP (<b>D</b>), and ACAN (<b>E</b>).</p> Full article ">Figure 5
<p>(<b>A</b>) SEM image of biomineralized film deposited by the C9 cells after 14 days in culture on PSS28, clearly showing the ECM fibers. (<b>B</b>) EDX spectra of the film showing the presence of Ca, P, O, and Si minerals present. (<b>C</b>–<b>E</b>) Elemental maps of Ca, P, and Si on the surface with overlap of Ca and P consistent with a uniform layer of hydroxyapatite incorporated into the ECM fibers shown in (<b>A</b>).</p> Full article ">Figure 6
<p>Atomic force microscopy images of polymer coatings spun cast on HF-etched Si with (<b>A</b>) 200 nm PB (<b>B</b>) 20 nm PSS28, and (<b>C</b>) a 1:1 binary PS28/PB blend. (<b>D</b>) Lateral force image corresponding to (<b>C</b>). Scanning electron microscope images of the films surfaces following incubation by the C9 expressing rhBMP-2: (<b>E</b>) 200 nm PB, (<b>F</b>) 20 nm PSS28, and (<b>G</b>) 1:1 binary PB/PSS28 blend. EDX spectra plotted as counts (y-axis) vs. energy (keV; x-axis) corresponding to the SEM images for (<b>H</b>) 200 nm PB, (<b>I</b>) 20 nm PSS<sub>28</sub>, and (<b>J</b>) 1:1 Binary PSS28/PB blend. (<b>K</b>) Schematic of the polymers in the phase segregated blend film. The scale bar in panels <b>E</b>–<b>G</b> is 20 µm. Panels <b>A</b> and <b>B</b> are 20 µm × 20 µm, and Panel <b>C</b> and <b>D</b> are 20 µm × 10 µm.</p> Full article ">Figure 7
<p>Scanning modulation force microscopy (SMFM) was carried out on (<b>A</b>) PB, PSS<sub>28</sub>, and a 1:1 blend of PB and PSS<sub>28</sub> (1:1) and on (<b>B</b>) live cells cultured on these substrates for 4 days in DOXY<sup>−</sup>/rhBMP2<sup>+</sup> medium (dark gray bars) or DOXY<sup>+</sup>/rhBMP2<sup>−</sup> medium (light gray bars). ACAN mRNA expression (<b>C</b>) was evaluated after 14 days of growth.</p> Full article ">
10 pages, 9930 KiB  
Article
High Temperature Anti-Friction Behaviors of a-Si:H Films and Counterface Material Selection
by Qunfeng Zeng and Liguo Qin
Coatings 2019, 9(7), 450; https://doi.org/10.3390/coatings9070450 - 18 Jul 2019
Cited by 9 | Viewed by 3699
Abstract
In the present paper, the influence of self-mated friction materials on the tribological properties of hydrogenated amorphous silicon films (a-Si:H films) is studied systemically at high temperature. The results are obtained by comparing the tribological properties of a-Si:H films under different friction pair [...] Read more.
In the present paper, the influence of self-mated friction materials on the tribological properties of hydrogenated amorphous silicon films (a-Si:H films) is studied systemically at high temperature. The results are obtained by comparing the tribological properties of a-Si:H films under different friction pair materials and temperatures. The a-Si:H films exhibit super-low friction of 0.07 at a temperature of 600 °C, and ceramic materials are appropriate for anti-friction behaviors of a-Si:H films at high temperature. The results of tribotests and observations of the fundamental friction mechanism show that super-low friction of a-Si:H films and ceramic materials of the friction system are involved in high temperature oxidation; this also applies to the tribochemical reactions of a-Si:H films, steel and iron silicate in open air at elevated temperature in the friction process. Full article
(This article belongs to the Special Issue Science and Technology of Thermal Barrier Coatings)
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<p>(<b>a</b>) Raman and (<b>b</b>) FTIR spectrum of a-Si:H films.</p> Full article ">Figure 2
<p>CoF of steel ball/a-Si:H films under different temperatures.</p> Full article ">Figure 3
<p>Images of wear scar of steel ball/a-Si:H films at 600 °C: (<b>a</b>) disc; (<b>b</b>) ball.</p> Full article ">Figure 4
<p>SEM images and EDS of wear scar of disc and Raman spectrum of steel ball/a-Si:H films: (<b>a</b>) SEM images and (<b>b</b>) EDS spectroscopy of wear scar disc at 600 °C. (<b>c</b>) Raman spectrum of wear scar on ball. (<b>d</b>) Raman spectrum of wear scar on disc.</p> Full article ">Figure 5
<p>CoF of DLC films on steel ball/a-Si:H films under different temperatures.</p> Full article ">Figure 6
<p>Images of wear scar of DLC films on steel ball/a-Si:H films at 600 °C: (<b>a</b>) disc; (<b>b</b>) ball.</p> Full article ">Figure 7
<p>Raman spectrum of wear scar of DLC films/silicon films under different temperatures: (<b>a</b>) ball; (<b>b</b>) disc.</p> Full article ">Figure 8
<p>CoF of ZrO<sub>2</sub> ball/a-Si:H films under different temperatures.</p> Full article ">Figure 9
<p>CoF of Si<sub>3</sub>Ni<sub>4</sub> ball/a-Si:H films under different temperatures.</p> Full article ">Figure 10
<p>Images of wear scar of Si<sub>3</sub>N<sub>4</sub> ball/a-Si:H films at 600 °C: (<b>a</b>) a-Si:H; (<b>b</b>) ball.</p> Full article ">Figure 11
<p>Raman spectrum of wear scar of Si<sub>3</sub>N<sub>4</sub>/a-Si:H films under different temperatures: (<b>a</b>) ball; (<b>b</b>) disc.</p> Full article ">Figure 12
<p>CoF of different friction pair materials and temperatures.</p> Full article ">
11 pages, 5059 KiB  
Article
The Implication of Benzene–Ethanol Extractive on Mechanical Properties of Waterborne Coating and Wood Cell Wall by Nanoindentation
by Yan Wu, Yingchun Sun, Feng Yang, Haiqiao Zhang and Yajing Wang
Coatings 2019, 9(7), 449; https://doi.org/10.3390/coatings9070449 - 18 Jul 2019
Cited by 20 | Viewed by 4182
Abstract
The waterborne coating uses water as its solvent, which will partially dissolve wood extractives when it is applied to wood surfaces. This influences both the coating curing process and the mechanical properties of the cured coating. To investigate these influences, the mechanical properties [...] Read more.
The waterborne coating uses water as its solvent, which will partially dissolve wood extractives when it is applied to wood surfaces. This influences both the coating curing process and the mechanical properties of the cured coating. To investigate these influences, the mechanical properties of waterborne polyacrylic coating on control and extractive-free wood surfaces were investigated by nanoindentation. Reductions to elastic modulus (Er) and hardness (H) of the coating layer was observed in the wood cell walls adjacent to or away from coating layers. Extraction treatment resulted in significant decrease of the Er and H of the coating layer on extractive-free wood surface comparing with control wood, but the values slightly increased for extractive-free wood cell walls compared to a control. Er and H of coating in wood cell lumen were higher than the average value of coating layer on wood surface in both the control and extractive-free wood. The Er of wood cell wall without coating filled in lumen was significantly higher than those of filling with coating. However, there was no distinct difference of H. The Er and H of CCML in extractive-free wood were 15% and 6% lower than those in control ones, respectively. Full article
(This article belongs to the Special Issue Coatings and Interfaces)
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<p>Diagram of sample preparation: microtome (<b>A</b>); wood sample (<b>B</b>); soxhlet extraction apparatus (<b>C</b>); ultramicrotome (<b>D</b>); wood sample (<b>E</b>); and Hysitron TriboIndenter system (<b>F</b>).</p> Full article ">Figure 2
<p>Microscopic and SPM images for the coated control wood sample and locations of indents: (<b>A</b>,<b>C</b>) SPM images of test locations and the indents after characterization by nanoindentation; (<b>B</b>) incident light micrograph of the coated layer and the wood cell wall.</p> Full article ">Figure 3
<p>Load-displacement curves of acrylic-coated wood samples at room temperature.</p> Full article ">Figure 4
<p>Spectra of control and extractive-free wood.</p> Full article ">Figure 5
<p>Modulus and hardness of water-based acrylic coating layer evaluated by nanoindentation (C1–C6: indents at coating layer; C7 and C8: indents at coating filled in the cell lumen; the inserted figures compare control wood (red line) and extractive-free wood (black line) at C5–C8 locations): (<b>A</b>) Reduced elastic modulus of coating layer indented at C1–C8; (<b>B</b>) Reduced elastic modulus indented at C5–C8; (<b>C</b>) SPM images of coating layer and wood cell wall after nanoindenation test; (<b>D</b>) Hardness of coating layer indented atC1–C8; (<b>E</b>) Hardness indented at C5–C8.</p> Full article ">Figure 6
<p>Reduced elastic modulus and hardness of wood cell wall and compound corner lamella (the inserted scanning probe microscope (SPM) images showed the indents at wood cell wall (W, WC and PC) and compound corner middle lamella (CCML)).</p> Full article ">
13 pages, 4394 KiB  
Article
Phase Selectivity in Cr and N Co-Doped TiO2 Films by Modulated Sputter Growth and Post-Deposition Flash-Lamp-Annealing
by Raúl Gago, Slawomir Prucnal, René Hübner, Frans Munnik, David Esteban-Mendoza, Ignacio Jiménez and Javier Palomares
Coatings 2019, 9(7), 448; https://doi.org/10.3390/coatings9070448 - 17 Jul 2019
Cited by 3 | Viewed by 3441
Abstract
In this paper, we report on the phase selectivity in Cr and N co-doped TiO2 (TiO2:Cr,N) sputtered films by means of interface engineering. In particular, monolithic TiO2:Cr,N films produced by continuous growth conditions result in the formation of [...] Read more.
In this paper, we report on the phase selectivity in Cr and N co-doped TiO2 (TiO2:Cr,N) sputtered films by means of interface engineering. In particular, monolithic TiO2:Cr,N films produced by continuous growth conditions result in the formation of a mixed-phase oxide with dominant rutile character. On the contrary, modulated growth by starting with a single-phase anatase TiO2:N buffer layer, can be used to imprint the anatase structure to a subsequent TiO2:Cr,N layer. The robustness of the process with respect to the growth conditions has also been investigated, especially regarding the maximum Cr content (<5 at.%) for single-phase anatase formation. Furthermore, post-deposition flash-lamp-annealing (FLA) in modulated coatings was used to improve the as-grown anatase TiO2:Cr,N phase, as well as to induce dopant activation (N substitutional sites) and diffusion. In this way, Cr can be distributed through the whole film thickness from an initial modulated architecture while preserving the structural phase. Hence, the combination of interface engineering and millisecond-range-FLA opens new opportunities for tailoring the structure of TiO2-based functional materials. Full article
(This article belongs to the Special Issue Advanced Strategies in Thin Film Engineering by Magnetron Sputtering)
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<p>RBS (Rutherford backscattering spectrometry) data (dots) and fitted spectra (solid lines) for as-grown TiO<sub>2</sub>:Cr,N coatings grown on Si(100) substrates with monolithic and modulated (bilayer and gradient architectures) structures. The individual element contribution from Cr to the fitted spectra is also shown (dotted lines).</p> Full article ">Figure 2
<p>Grazing-incidence XRD patterns from TiO<sub>2</sub>, TiO<sub>2</sub>:N and TiO<sub>2</sub>:Cr,N (monolithic/modulated) coatings grown under equivalent conditions. The diffraction patterns from anatase (PDF-00-021-1272), rutile (PDF-00-021-1276), Cr<sub>2</sub>O<sub>3</sub> (PDF-00-001-0622) and CrO<sub>2</sub> (PDF-00-001-0622) reference compounds are shown in the upper panel for phase identification.</p> Full article ">Figure 3
<p>XANES spectra at the different element edges for monolithic (MON) and modulated (MOD) TiO<sub>2</sub>:Cr,N coatings before (black) and after (red) FLA. The reference spectra from binary oxide compounds are also included in the bottom part (see text for details).</p> Full article ">Figure 4
<p>Grazing-incidence XRD patterns from monolithic and modulated TiO<sub>2</sub>:Cr,N coatings before and after FLA. The anatase phase in modulated coatings shows a shift to higher scattering angles (lattice contraction) with the thermal treatment.</p> Full article ">Figure 5
<p>N 1<span class="html-italic">s</span> core-level spectra from monolithic and modulated TiO<sub>2</sub>:Cr,N coatings before and after FLA.</p> Full article ">Figure 6
<p>Cross-sectional bright-field TEM images from monolithic (MON) and modulated (MOD) TiO<sub>2</sub>:Cr,N coatings as-deposited (AD) (<b>a</b>) and after FLA (<b>b</b>). The slightly under-focused (UF) bright-field images in the third row are magnified views of the marked regions close to the substrate-coating interface in the MOD case to enhance the contrast of the pore structures. Corresponding representative SAED patterns displayed in the bottom part confirm the dominant rutile and anatase character for MON and MOD coatings, respectively.</p> Full article ">Figure 7
<p>HAADF-STEM micrographs and element distributions obtained by EDXS analysis of monolithic (MON) and modulated (MOD) coatings in as-deposited (AD) and after FLA states. Dashed lines in the MOD-AD coating indicate the interfaces caused by the gradient steps during film growth.</p> Full article ">Figure 8
<p>XANES spectra of modulated films with a bilayer structure produced with different <span class="html-italic">W</span><sub>Cr</sub> in the uppermost layer in as-grown (black curves) and after FLA (red curves) states.</p> Full article ">
14 pages, 3811 KiB  
Article
Bio-Based Composites with Enhanced Matrix-Reinforcement Interactions from the Polymerization of α-Eleostearic Acid
by Amanda Murawski and Rafael L. Quirino
Coatings 2019, 9(7), 447; https://doi.org/10.3390/coatings9070447 - 17 Jul 2019
Cited by 8 | Viewed by 3158
Abstract
Vegetable oil-based composites have been proposed as interesting bio-based materials in the recent past. The carbon–carbon double bonds in unsaturated vegetable oils are ideal reactive sites for free radical polymerization. Without the presence of a reinforcement, typical vegetable oil-based polymers cannot achieve competitive [...] Read more.
Vegetable oil-based composites have been proposed as interesting bio-based materials in the recent past. The carbon–carbon double bonds in unsaturated vegetable oils are ideal reactive sites for free radical polymerization. Without the presence of a reinforcement, typical vegetable oil-based polymers cannot achieve competitive thermo-mechanical properties. Compatibilizers have been utilized to enhance the adhesion between resin and reinforcement. This work discusses the antagonist implications of polarity and crosslink density of an unprecedented polar α-eleostearic acid-based resin reinforced with α-cellulose, eliminating the need of a compatibilizer. It is shown that the polar regions of α-eleostearic acid can interact directly with the polar reinforcement. The successful isolation of α-eleostearic acid from tung oil was verified via GC-MS, 1H NMR, Raman, and FT-IR spectroscopies. The optimal cure schedule for the resin was determined by DSC and DEA. The composites’ thermo-mechanical properties were assessed by TGA, DSC, and DMA. Full article
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<p>FTIR spectra of (<b>a</b>) tung oil methyl esters, (<b>b</b>) isolated α-eleostearic acid, and (<b>c</b>) tung oil.</p> Full article ">Figure 2
<p><sup>1</sup>H NMR spectra of (<b>a</b>) tung oil, (<b>b</b>) tung oil methyl esters, and (<b>c</b>) α-eleostearic acid.</p> Full article ">Figure 3
<p>Raman spectra of (<b>a</b>) tung oil, (<b>b</b>) isolated α-eleostearic acid, and (<b>c</b>) tung oil methyl ester.</p> Full article ">Figure 4
<p>Chromatograms of (<b>a</b>) tung oil, (<b>b</b>) isolated α-eleostearic acid, and (<b>c</b>) tung oil methyl esters.</p> Full article ">Figure 5
<p>(<b>A</b>) DEA curves of fatty acid resin cured at 120, 130, and 140 °C for 20 h; (<b>B</b>) Derivative of the DEA curves of the fatty acid resin cured at 130 and 120 °C with respect to time.</p> Full article ">Figure 6
<p>(<b>A</b>) Raman spectra of (a) tung oil fatty acid crude resin, and (b) tung oil fatty acid resin cured at 130 °C for 18 h. (<b>B</b>) DSC curves of (a) tung oil resin cured at 130 °C for 18 h, (b) tung oil fatty acid resin cured at 130 °C for 18 h, (c) tung oil methyl ester resin cured at 130°C for 18 h, and (d) tung oil methyl ester resin cured at 130 °C for 24 h.</p> Full article ">Figure 7
<p>SEM images of (<b>A</b>) composite prepared with tung oil fatty acid resin, (<b>B</b>) composite prepared with tung oil methyl ester resin, and (<b>C</b>) composite prepared with a tung oil resin.</p> Full article ">Figure 8
<p>TGA curves of (<b>a</b>) tung oil resin, (<b>b</b>) tung oil fatty acid resin, (<b>c</b>) tung oil methyl ester resin, (<b>d</b>) composite prepared with tung oil resin, (<b>e</b>) composite prepared with tung oil fatty acid resin, and (<b>f</b>) composite prepared with tung oil methyl ester resin.</p> Full article ">Figure 9
<p>(<b>A</b>) Storage modulus (E’) vs. temperature and (<b>B</b>) tan δ curves for (a) a resin prepared with tung oil, (b) a resin prepared with fatty acids, (c) a composite prepared with tung oil, (d) a composite prepared with fatty acids, and (e) a composite prepared with methyl esters.</p> Full article ">
13 pages, 2112 KiB  
Article
Influence of MHD on Thermal Behavior of Darcy-Forchheimer Nanofluid Thin Film Flow over a Nonlinear Stretching Disc
by Abdullah Dawar, Zahir Shah, Poom Kumam, Waris Khan and Saeed Islam
Coatings 2019, 9(7), 446; https://doi.org/10.3390/coatings9070446 - 17 Jul 2019
Cited by 22 | Viewed by 3829
Abstract
The aim of this research work is to increase our understanding of the exhaustion of energy in engineering and industrial fields. The study of nanofluids provides extraordinary thermal conductivity and an increased heat transmission coefficient compared to conventional fluids. These specific sorts of [...] Read more.
The aim of this research work is to increase our understanding of the exhaustion of energy in engineering and industrial fields. The study of nanofluids provides extraordinary thermal conductivity and an increased heat transmission coefficient compared to conventional fluids. These specific sorts of nanofluids are important for the succeeding generation of flow and heat transfer fluids. Therefore, the investigation of revolutionary new nanofluids has been taken up by researchers and engineers all over the world. In this article, the study of the thin layer flow of Darcy-Forchheimer nanofluid over a nonlinear radially extending disc is presented. The disc is considered as porous. The impacts of thermal radiation, magnetic field, and heat source/sink are especially focused on. The magnetic field, positive integer, porosity parameter, coefficient of inertia, and fluid layer thickness reduce the velocity profile. The Prandtl number and fluid layer thickness reduce the temperature profile. The heat source/sink, Eckert number, and thermal radiation increase the temperature profile. The suggested model is solved analytically by the homotopy analysis method (HAM). The analytical and numerical techniques are compared through graphs and tables, and have shown good agreement. The influences of embedded parameters on the flow problem are revealed through graphs and tables. Full article
(This article belongs to the Special Issue Recent Trends in Coatings and Thin Film–Modeling and Application)
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<p>Geometrical illustration of the problem.</p> Full article ">Figure 2
<p><math display="inline"><semantics> <mi>ℏ</mi> </semantics></math>-curves for <math display="inline"><semantics> <mrow> <msup> <mi>f</mi> <mo>′</mo> </msup> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">η</mi> <mo>)</mo> </mrow> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">θ</mi> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">η</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>.</p> Full article ">Figure 3
<p>Impression of <span class="html-italic">n</span> and <span class="html-italic">M</span> on <math display="inline"><semantics> <mrow> <msup> <mi>f</mi> <mo>′</mo> </msup> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">η</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>.</p> Full article ">Figure 4
<p>Impression of κ and <span class="html-italic">F<sub>r</sub></span> on <math display="inline"><semantics> <mrow> <msup> <mi>f</mi> <mo>′</mo> </msup> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">η</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>.</p> Full article ">Figure 5
<p>Impression of β on <math display="inline"><semantics> <mrow> <msup> <mi>f</mi> <mo>′</mo> </msup> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">η</mi> <mo>)</mo> </mrow> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">θ</mi> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">η</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>.</p> Full article ">Figure 6
<p>Impression of <math display="inline"><semantics> <mi mathvariant="sans-serif">γ</mi> </semantics></math> and <span class="html-italic">R</span> on <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">θ</mi> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">η</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>.</p> Full article ">Figure 7
<p>Impression of <math display="inline"><semantics> <mrow> <mi>Pr</mi> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>Ec</mi> </mrow> </semantics></math> on <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">θ</mi> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">η</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>.</p> Full article ">Figure 8
<p>The assessment of HAM and ND-Solve for <math display="inline"><semantics> <mrow> <msup> <mi>f</mi> <mo>′</mo> </msup> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">η</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>.</p> Full article ">Figure 9
<p>The assessment of HAM and ND-Solve for <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">θ</mi> <mrow> <mo>(</mo> <mi mathvariant="sans-serif">η</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>.</p> Full article ">
19 pages, 14067 KiB  
Article
Stress Corrosion Cracking Resistance of Cold-Sprayed Al 6061 Deposits Using a Newly Developed Test Fixture
by Mala Sharma, Jeremy Schreiber, Timothy Eden and Victor Champagne
Coatings 2019, 9(7), 445; https://doi.org/10.3390/coatings9070445 - 17 Jul 2019
Cited by 3 | Viewed by 5045
Abstract
The stress corrosion cracking (SCC) response of Al 6061 bulk deposits produced by high-pressure cold spray (HPCS) was investigated and compared to commercial wrought Al 6061-T6 material. Representative tensile coupons were stressed to 25%, 65% and 85% of their respective yield strength and [...] Read more.
The stress corrosion cracking (SCC) response of Al 6061 bulk deposits produced by high-pressure cold spray (HPCS) was investigated and compared to commercial wrought Al 6061-T6 material. Representative tensile coupons were stressed to 25%, 65% and 85% of their respective yield strength and exposed to ASTM B117 salt fog for 90 days. After exposure, the samples were mechanically tested to failure, and subsequently investigated for stress corrosion cracking via optical and scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDS). The results were compared to the wrought Al 6061-T6 properties and correlated with the observed microstructures. Wrought samples showed the initiation of stress corrosion cracking, while the cold-sprayed deposits appeared to be unaffected or affected by general corrosion only. Optical microscopy revealed evidence of stress corrosion cracking in the form of intergranular corrosion in the wrought samples, while no significant corrosion was observed in the cold-sprayed deposits. Fractography revealed wrought samples failed due to multiple mechanisms, with predominant cleavage and intergranular failure, but cold-sprayed samples only failed by ductile dimple rupture. The difference in SCC response between the differently processed materials is attributed to the documented benefits of the cold spray process, which includes maintaining fine grain structure of the feedstock powder and high density after consolidation, low oxidation, and work hardening effect. Full article
(This article belongs to the Special Issue Cold Spraying: Recent Trends and Future Views)
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Figure 1
<p>Al 6061 as-received powder at (<b>a</b>) low magnification and (<b>b</b>) high magnification; particles primarily exhibit a spherical morphology.</p> Full article ">Figure 2
<p>Particle size distribution (PSD) for the Al 6061 feedstock powder.</p> Full article ">Figure 3
<p>Cross section and isometric rendering of cold-sprayed coating on Al 6061-T6 plate.</p> Full article ">Figure 4
<p>Corrosion-resistant uniaxial test fixture designed at PSU/ARL, used in SCC testing loaded with a sample (<b>a</b>) before coating to prevent galvanic couple and (<b>b</b>) after coating with STOP-OFF lacquer.</p> Full article ">Figure 5
<p>Fiber Bragg grating data captured during fixture testing. Units on the vertical axis are in microstrain, and the horizontal axis is time.</p> Full article ">Figure 6
<p>Optical cross-sectional micrograph for cold spray Al 6061, etched using Keller’s reagent, showing the particle morphologies after deposition. (<b>a</b>) There is some evidence of interparticle voids and porosity, as indicated by arrows and (<b>b</b>) high-magnification micrograph showing small average grain size and finer sub grains resulting from buildup of particles.</p> Full article ">Figure 6 Cont.
<p>Optical cross-sectional micrograph for cold spray Al 6061, etched using Keller’s reagent, showing the particle morphologies after deposition. (<b>a</b>) There is some evidence of interparticle voids and porosity, as indicated by arrows and (<b>b</b>) high-magnification micrograph showing small average grain size and finer sub grains resulting from buildup of particles.</p> Full article ">Figure 7
<p>Optical cross-sectional micrograph of wrought Al 6061-T6 samples in as-received condition and etched using Keller’s reagent. There is clear evidence of randomly sized and irregularly distributed second-phase precipitates.</p> Full article ">Figure 8
<p>Stress/strain behavior of the wrought Al 6061-T6 samples after 90 days of B-117 salt fog exposure.</p> Full article ">Figure 9
<p>Stress/strain behavior of the cold-sprayed Al 6061-T6 deposits after 90 days of B-117 salt fog exposure.</p> Full article ">Figure 10
<p>Tensile data for wrought (W) and cold-sprayed (CS) samples at various pre-stress levels after 90 days of B-117 salt fog exposure (SS).</p> Full article ">Figure 11
<p>Strain at fracture and strength retained of wrought (W) and cold-sprayed (CS) samples at various pre-stress levels after 90 days of B-117 salt fog exposure (SF).</p> Full article ">Figure 12
<p>Metallographic section of wrought Al 6061-T6 stressed at 25% of yield strength after 90 days exposure to B117 salt fog testing. Various locations show pitting and intergranular crack branching.</p> Full article ">Figure 13
<p>Metallographic section of wrought Al 6061-T6 stressed at 65% of yield strength after 90 days exposure to B117 salt fog testing. Various locations show pitting and intergranular crack branching.</p> Full article ">Figure 14
<p>Metallographic section of wrought Al 6061-T6 stressed at 85% of yield strength after 90 days exposure to B117 salt fog testing. Various locations show pitting and intergranular crack branching.</p> Full article ">Figure 15
<p>Metallographic sections of cold spray samples at (<b>a</b>) 25% yield strength and (<b>b</b>) 65% yield strength after 90 days exposure to B117 salt fog testing. There is no indication of stress corrosion cracking through branching or evidence of any other artifacts related to corrosive attack on failed sample cross sections; (<b>c</b>) Metallographic sections of cold spray samples at 85% yield strength after 90 days exposure to B117 salt fog testing. There is no indication of stress corrosion cracking through branching on the entire cross section. Evidence of slight corrosive attack is observed and identified on the figure.</p> Full article ">Figure 16
<p>Secondary electron images of wrought Al 6061-T6 fracture surfaces. The fractography predominately shows (<b>a</b>) cleavage as well as intergranular fracture with (<b>b</b>) the grain boundaries attacked in the 25% yield stress condition.</p> Full article ">Figure 17
<p>Secondary electron images of wrought Al 6061-T6 fracture surfaces. The fractography predominately shows cleavage and transgranular fracture (circles), but intergranular facture is also present (arrows) in (<b>a</b>) 65% and (<b>b</b>) 85% stress conditions.</p> Full article ">Figure 18
<p>Secondary electron images of cold-sprayed Al 6061 fracture surfaces. The fractography predominately shows the failure mode to be ductile in nature in (<b>a</b>) 25% stress, (<b>b</b>) 65% stress, and (<b>c</b>) 85% stress conditions. Smooth particle–particle fracture can be observed (arrows).</p> Full article ">Figure 19
<p>EDS analysis of wrought fracture surface after B117 testing, showing evidence of second-phase particle concentrations of Mg, Si and Fe.</p> Full article ">Figure 20
<p>EDS analysis of cold-sprayed, stressed 25% fracture surface after B117 testing, showing the fracture surface is predominately free of precipitates or element segregation. Two second-phase particles are obvious, one an oxide inclusion and the other rich in Si.</p> Full article ">
16 pages, 4673 KiB  
Article
Effect of High-Temperature Calcined Wheat Straw Powder after Lignin Removal on Properties of Waterborne Wood Coatings
by Xiaoxing Yan, Lin Wang and Xingyu Qian
Coatings 2019, 9(7), 444; https://doi.org/10.3390/coatings9070444 - 16 Jul 2019
Cited by 10 | Viewed by 3121
Abstract
The effect of adding wheat straw powder after lignin removal (WSPALR) and high-temperature calcined WSPALR on the hardness, adhesion, and resistance to impact, color difference, and mold resistance of waterborne coatings was studied. The results showed that the hardness was the highest of [...] Read more.
The effect of adding wheat straw powder after lignin removal (WSPALR) and high-temperature calcined WSPALR on the hardness, adhesion, and resistance to impact, color difference, and mold resistance of waterborne coatings was studied. The results showed that the hardness was the highest of 6H when the concentration of WSPALR was 1.0%–2.0%. WSPALR and high-temperature calcined WSPALR had little effect on the adhesion and impact resistance of waterborne coatings, and the resistance to impact was about 10.0 kg cm. When both the concentration of WSPALR and high-temperature calcined WSPALR were 0.5%, the waterborne coating had the best adhesion of Level 1. The addition of high-temperature calcined WSPALR maintained the color difference of the original coatings. A high WSPALR concentration showed better mold resistance than a low concentration WSPALR, and the inhibition effect of high-temperature calcined WSPALR on Trichoderma was better than that of WSPALR. When the concentration of WSPALR calcined at a high temperature was 0.5%, it showed a better hardness of 4H, Level 1 adhesion, 10.0 kg cm resistance to impact, and 1.1 color difference of the waterborne coating. This work has important application value for mold resistance of wood coatings. Full article
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<p>SEM images of (<b>A</b>) wheat straw powder, (<b>C</b>) WSPALR, and (<b>E</b>) high-temperature calcined WSPALR. EDX analysis of (<b>B</b>) wheat straw powder, (<b>D</b>) WSPALR, and (<b>F</b>) high-temperature calcined WSPALR.</p> Full article ">Figure 2
<p>SEM images: (<b>A</b>) waterborne coating; waterborne coating with different concentrations of WSPALR: (<b>C</b>) 0.5% and (<b>E</b>) 5.0%; and waterborne coating with different concentrations of calcined WSPALR: (<b>G</b>) 0.5% and (<b>I</b>) 5.0%. EDX analysis: (<b>B</b>) waterborne coating; waterborne coating with different concentrations of WSPALR: (<b>D</b>) 0.5% and (<b>F</b>) 5.0%; and waterborne coating with different concentrations of calcined WSPALR: (<b>H</b>) 0.5% and (<b>J</b>) 5.0%.</p> Full article ">Figure 2 Cont.
<p>SEM images: (<b>A</b>) waterborne coating; waterborne coating with different concentrations of WSPALR: (<b>C</b>) 0.5% and (<b>E</b>) 5.0%; and waterborne coating with different concentrations of calcined WSPALR: (<b>G</b>) 0.5% and (<b>I</b>) 5.0%. EDX analysis: (<b>B</b>) waterborne coating; waterborne coating with different concentrations of WSPALR: (<b>D</b>) 0.5% and (<b>F</b>) 5.0%; and waterborne coating with different concentrations of calcined WSPALR: (<b>H</b>) 0.5% and (<b>J</b>) 5.0%.</p> Full article ">Figure 3
<p>The cross-section SEM images of the waterborne coatings with (<b>A</b>) 5.0% WSPALR and (<b>B</b>) 5.0% calcined WSPALR.</p> Full article ">Figure 4
<p>The infrared spectrum of wheat straw powder: untreated and treated with alkaline hydrogen peroxide.</p> Full article ">Figure 5
<p>The infrared spectrum: (<b>A</b>) waterborne coating; waterborne coating with different concentrations of WSPALR: (<b>B</b>) 0.5% and (<b>C</b>) 5.0%; and waterborne coating with different concentrations of calcined WSPALR: (<b>D</b>) 0.5% and (<b>E</b>) 5.0%.</p> Full article ">Figure 6
<p>Effect on WSPALR and high-temperature calcined WSPALR on the hardness of coatings.</p> Full article ">Figure 7
<p>Effect of WSPALR and high-temperature calcined WSPALR on adhesion of coatings.</p> Full article ">Figure 8
<p>Effect of WSPALR and high-temperature calcined WSPALR on the resistance to impact of coatings.</p> Full article ">Figure 9
<p>Effect of WSPALR and high-temperature calcined WSPALR on the elongation at break of coatings.</p> Full article ">Figure 10
<p>Digital microscopic images of (<b>A</b>) wheat straw powder, (<b>B</b>) WSPALR, and (<b>C</b>) high-temperature calcined WSPALR.</p> Full article ">Figure 11
<p>Trichoderma grew on the surface of wood substrates: (<b>A</b>) waterborne coating; waterborne coating with different concentrations of WSPALR: (<b>B</b>) 0.5%; (<b>C</b>) 1.0%; (<b>D</b>) 2.0%; (<b>E</b>) 3.5%; (<b>F</b>) 5.0%; and waterborne coating with different concentrations of calcined WSPALR: (<b>G</b>) 0.5%; (<b>H</b>) 1.0%; (<b>I</b>) 2.0%; (<b>J</b>) 3.5%; (<b>K</b>) 5.0%.</p> Full article ">
12 pages, 5849 KiB  
Article
Manufacturing and Assessment of Electrospun PVP/TEOS Microfibres for Adsorptive Heat Transformers
by Patrizia Frontera, Mikio Kumita, Angela Malara, Junya Nishizawa and Lucio Bonaccorsi
Coatings 2019, 9(7), 443; https://doi.org/10.3390/coatings9070443 - 16 Jul 2019
Cited by 16 | Viewed by 4383
Abstract
A new adsorbent coating for the adsorber unit of an adsorption heat pump made of hybrid, organic–inorganic microfibres was prepared and characterized. Different coatings were obtained by the electrospinning of polyvinylpyrrolidone (PVP) solutions added with different quantities of tetraethyl orthosilicate (TEOS). PVP is [...] Read more.
A new adsorbent coating for the adsorber unit of an adsorption heat pump made of hybrid, organic–inorganic microfibres was prepared and characterized. Different coatings were obtained by the electrospinning of polyvinylpyrrolidone (PVP) solutions added with different quantities of tetraethyl orthosilicate (TEOS). PVP is a polymer with water adsorption capability and the TEOS addition allowed to increase the thermal stability of microfibres. The aim, indeed, was to preserve the polymeric structure of microfibres in order to obtain coatings with high flexibility and mechanical strength. The results demonstrated that TEOS concentrations in the range of 5–13 wt.% produced microfibre coatings of non-woven textile structure with both good water affinity and good thermal stability. SEM images of coatings showed that the deposited microfibre layers have both a high surface area and a high permeability representing a significant advantage in adsorption systems. Full article
(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications)
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<p>SEM images of microfibres coatings.</p> Full article ">Figure 2
<p>Determination of microfibre diameters by image digital analysis.</p> Full article ">Figure 3
<p>The polyvinylpyrrolidone polymeric unit.</p> Full article ">Figure 4
<p>TGA-DSC plots of pure and hybrid polyvinylpyrrolidone (PVP) microfibre coatings.</p> Full article ">Figure 5
<p>TGA-DSC comparison between pure PVP microfibres (<b>a</b>) and silica gel (<b>b</b>) (<span class="html-italic">T</span> = 25–150 °C).</p> Full article ">Figure 6
<p>Schemes of the tetraethyl orthosilicate (TEOS) addition to PVP at low (<b>a</b>) and high (<b>b</b>) concentration.</p> Full article ">Figure 7
<p>Correlation between weigh loss (<span class="html-italic">T</span> = 150 °C) and Si concentrations for the electrospun microfibres. Error bars of Si (EDX) measures are obtained from data in <a href="#coatings-09-00443-t002" class="html-table">Table 2</a>.</p> Full article ">Figure 8
<p>Cyclic TGA test for microfibres Mf-5.</p> Full article ">
13 pages, 5809 KiB  
Article
RF Magnetron Sputtering Deposition of TiO2 Thin Films in a Small Continuous Oxygen Flow Rate
by Octavian-Gabriel Simionescu, Cosmin Romanițan, Oana Tutunaru, Valentin Ion, Octavian Buiu and Andrei Avram
Coatings 2019, 9(7), 442; https://doi.org/10.3390/coatings9070442 - 16 Jul 2019
Cited by 50 | Viewed by 8578
Abstract
Rutile titanium oxide (TiO2) thin films require more energy to crystallize than the anatase phase of TiO2. It is a prime candidate for micro-optoelectronics and is usually obtained either by high substrate temperature, applying a substrate bias, pulsed gas [...] Read more.
Rutile titanium oxide (TiO2) thin films require more energy to crystallize than the anatase phase of TiO2. It is a prime candidate for micro-optoelectronics and is usually obtained either by high substrate temperature, applying a substrate bias, pulsed gas flow to modify the pressure, or ex situ annealing. In the present work, we managed to obtain high enough energy at the substrate in order for the particles to form rutile TiO2 at room temperature without any intentional substrate bias in a continuous gas flow. The rutile TiO2 thin films were deposited by a reactive radiofrequency magnetron sputtering system from a titanium target, in an argon/oxygen gas mixture. Investigations regarding the film’s structure and morphology were performed by X-ray diffraction (XRD), X-ray reflectivity (XRR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX), while the optical properties were investigated by means of ellipsometry. Full article
(This article belongs to the Special Issue Micro- and Nano-Coatings for Technological and Biomedical Applications)
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<p>Experimental data for a TiO<sub>2</sub> thin film deposited at Ar:O<sub>2</sub> flow rate of 30:1.5 sccm vs. the model fit with a single Gauss oscillator for (<b>a</b>) the amplitude ratio Ψ, and (<b>b</b>) the phase difference Δ.</p> Full article ">Figure 2
<p>Experimental GI-XRD pattern of a Ti thin film deposited under Ar:O<sub>2</sub> = 30:0 sccm flow rate (bottom) and Ar:O<sub>2</sub> = 30:0.5 sccm flow rate (top) in the chamber (black curves) and simulated patterns (red curves).</p> Full article ">Figure 3
<p>(<b>a</b>) Experimental GI-XRD patterns (black curve) of the investigated samples and the corresponding simulated curves (red curve). The letters “r” and “a” symbolize the rutile and anatase phases and the sharp peak at ~51° for the middle spectrum (Ar:O<sub>2</sub> = 30:1.5) is caused by the Si substrate. (<b>b</b>) Enhancement of (<b>a</b>) in the 2θ range of 23°–29° for the TiO<sub>2</sub> thin films.</p> Full article ">Figure 4
<p>XRR profiles and calculated data. Inset represents thickness (t), density (ρ) and surface roughness (σ).</p> Full article ">Figure 5
<p>Cross-section SEM images at 300 k× magnification of TiO<sub>2</sub> film deposited at (<b>a</b>) Ar:O<sub>2</sub> = 30:1, (<b>b</b>) Ar:O<sub>2</sub> = 30:1.5 and (<b>c</b>) Ar:O<sub>2</sub> = 30:2 sccm flow rate.</p> Full article ">Figure 5 Cont.
<p>Cross-section SEM images at 300 k× magnification of TiO<sub>2</sub> film deposited at (<b>a</b>) Ar:O<sub>2</sub> = 30:1, (<b>b</b>) Ar:O<sub>2</sub> = 30:1.5 and (<b>c</b>) Ar:O<sub>2</sub> = 30:2 sccm flow rate.</p> Full article ">Figure 6
<p>Element distribution mapping at 2000× magnification of the TiO<sub>2</sub> sample deposited under Ar:O<sub>2</sub> = 30:2 sccm flow rate.</p> Full article ">Figure 7
<p>The dispersion of optical constants: (<b>a</b>) Refractive index (inset: enhancement in the wavelength range of 500–550 nm) and (<b>b</b>) extinction coefficient for the as-deposited TiO<sub>2</sub> thin films obtained from fitting with a single Gauss oscillator.</p> Full article ">Figure 8
<p>Tauc plot for indirect transitions for a TiO<sub>2</sub> thin film deposited under Ar:O<sub>2</sub>=30:2 sccm flow rate. Inset represents the plot of the optical band gap energy as a function of O<sub>2</sub> flow rate during deposition.</p> Full article ">
13 pages, 11965 KiB  
Article
Deposition of TiO2 Thin Films on Wood Substrate by an Air Atmospheric Pressure Plasma Jet
by Ghiath Jnido, Gisela Ohms and Wolfgang Viöl
Coatings 2019, 9(7), 441; https://doi.org/10.3390/coatings9070441 - 15 Jul 2019
Cited by 33 | Viewed by 7254
Abstract
In the present work, titanium dioxide (TiO2) coatings were deposited on wood surfaces by an atmospheric pressure plasma jet using titanium tetraisopropoxide (TTIP) as a precursor to improve the wood’s stability against ultraviolet (UV) light and its moisture resistance capability. The [...] Read more.
In the present work, titanium dioxide (TiO2) coatings were deposited on wood surfaces by an atmospheric pressure plasma jet using titanium tetraisopropoxide (TTIP) as a precursor to improve the wood’s stability against ultraviolet (UV) light and its moisture resistance capability. The surface topology and morphology of the wood specimens were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Surface chemical compositions of the specimens were characterized by X-ray photoelectron spectroscopy (XPS) and by Fourier transform infrared (FTIR) spectroscopy. The wettability of the coated wood was investigated by measuring the sessile contact angle. SEM and AFM showed the presence of small globules of TiO2 with some areas agglomerated on the coated wood surface. The coated surface roughness increased with increasing deposition time. FTIR analysis showed the existence of a Ti–O–Ti band at 800–400 cm−1 on the coated wood surfaces. The results obtained from FTIR were confirmed by XPS measurements. The hydrophilic wood surfaces were transformed to become hydrophobic or superhydrophobic after coating with TiO2, depending on the deposition parameters. The changes of colour during UV-exposure for both uncoated and coated wood specimens were measured using the CIELab colour system. The TiO2 coated wood became more resistant to colour change after UV radiation exposure than did untreated wood. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic representation of the atmospheric pressure plasma jet (APPJ) system coupled with spraying system.</p> Full article ">Figure 2
<p>Graphical representation of the CIELab color space based on ref. [<a href="#B28-coatings-09-00441" class="html-bibr">28</a>].</p> Full article ">Figure 3
<p>Scanning electron microscope (SEM) images of (<b>a</b>) uncoated wood and (<b>b</b>) TiO<sub>2</sub>-coated wood at <span class="html-italic">v</span> = 80 mm/s, (<b>c</b>) TiO<sub>2</sub>-coated wood at <span class="html-italic">v</span> = 40 mm/s.</p> Full article ">Figure 4
<p>Three-dimensional atomic force microscopy (AFM) images of (<b>a</b>) uncoated wood, (<b>b</b>) TiO<sub>2</sub>-coated wood at deposition velocity 80 mm/s, (<b>c</b>) TiO<sub>2</sub>-coated wood at deposition velocity 40 mm/s, (<b>d</b>) uncoated glass, (<b>e</b>) TiO<sub>2</sub>-coated glass at deposition velocity 80 mm/s and (<b>f</b>) TiO<sub>2</sub>-coated glass at deposition velocity 40 mm/s.</p> Full article ">Figure 5
<p>(<b>a</b>) Fourier transform infrared (FTIR) spectroscopy–attenuated total reflectance (FTIR–ATR) spectra for uncoated wood and TiO<sub>2</sub>-coated wood; (<b>b</b>) Spectra for TiO<sub>2</sub> pure powder and TiO<sub>2</sub> powder scraped from the coated glass substrate.</p> Full article ">Figure 6
<p>Survey spectra for uncoated (black) and TiO<sub>2</sub>-coated wood (red) showing oxygen peaks and a carbon peaks and titanium peak.</p> Full article ">Figure 7
<p>High-resolution XPS spectra of (<b>a</b>) Ti 2<span class="html-italic">p</span>, (<b>b</b>) O 1<span class="html-italic">s</span>, (<b>c</b>) C 1<span class="html-italic">s</span> and (<b>d</b>) N 1<span class="html-italic">s</span> of coated wood using Gaussian–Lorentzians deconvolution.</p> Full article ">Figure 8
<p>Colour change of coated and uncoated wood versus the irradiation time (<b>a</b>) lightness index change <span class="html-italic">ΔL</span>, (<b>b</b>) red-green index change <span class="html-italic">Δa</span>, (<b>c</b>) yellow-blue index change <span class="html-italic">Δb</span>, (<b>d</b>) total color change <span class="html-italic">ΔE</span>, and (<b>e</b>) optical images of the uncoated and coated wood before and after 50 and 100 h of irradiation.</p> Full article ">Figure 8 Cont.
<p>Colour change of coated and uncoated wood versus the irradiation time (<b>a</b>) lightness index change <span class="html-italic">ΔL</span>, (<b>b</b>) red-green index change <span class="html-italic">Δa</span>, (<b>c</b>) yellow-blue index change <span class="html-italic">Δb</span>, (<b>d</b>) total color change <span class="html-italic">ΔE</span>, and (<b>e</b>) optical images of the uncoated and coated wood before and after 50 and 100 h of irradiation.</p> Full article ">Figure 9
<p>Images of 11 µm water droplets on (<b>a</b>) uncoated wood, (<b>b</b>) TiO<sub>2</sub>-coated wood surface at <span class="html-italic">v</span> = 80 mm/s and (<b>c</b>) TiO<sub>2</sub>-coated wood surface at <span class="html-italic">v</span> = 40 mm/s.</p> Full article ">
12 pages, 2194 KiB  
Article
Characterisation of NiTi Orthodontic Archwires Surface after the Simulation of Mechanical Loading in CACO2-2 Cell Culture
by Nikola Lepojević, Ivana Šćepan, Branislav Glišić, Monika Jenko, Matjaž Godec, Samo Hočevar and Rebeka Rudolf
Coatings 2019, 9(7), 440; https://doi.org/10.3390/coatings9070440 - 15 Jul 2019
Cited by 9 | Viewed by 4060
Abstract
Nickel-titanium (NiTi) orthodontic archwires are crucial in the initial stages of orthodontic therapy when the movement of teeth and deflection of the archwire are the largest. Their great mechanical properties come with their main disadvantage—the leakage of nickel. Various in vitro studies measured [...] Read more.
Nickel-titanium (NiTi) orthodontic archwires are crucial in the initial stages of orthodontic therapy when the movement of teeth and deflection of the archwire are the largest. Their great mechanical properties come with their main disadvantage—the leakage of nickel. Various in vitro studies measured nickel leakage from archwires that were only immersed in the medium with little or minimal simulation of all stress and deflection forces that affect them. This study aims to overcome that by simulating deflection forces that those archwires are exposed to inside the mouth of a patient. NiTi orthodontic archwires were immersed in CACO2-2 cell culture medium and then immediately loaded while using a simulator of multiaxial stress for 24 h. After the experiment, the surface of the NiTi orthodontic archwires were analysed while using scanning electron microscopy (SEM) and auger electron spectroscopy (AES). The observations showed significant microstructural and compositional changes within the first 51 nm thickness of the archwire surface. Furthermore, the released nickel and titanium concentrations in the CACO2-2 cell culture medium were measured while using Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). It was found out that the level of released nickel ions was 1.310 µg/L, which can be assigned as statistically significant results. These data represent the first mention of the already detectable release of Ni ions after 24 h during the simulation of mechanical loading in the CACO2-2 cell culture medium, which is important for clinical orthodontic praxis. Full article
(This article belongs to the Special Issue Anticorrosion Protection of Nonmetallic and Metallic Coatings)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Fixed orthodontic appliance (arrow pointing to the bending and torsional stresses of the archwire); (<b>b</b>) Simulation of multiaxial stress equipment (SMAS) [<a href="#B23-coatings-09-00440" class="html-bibr">23</a>]. Reprinted with permission from [<a href="#B23-coatings-09-00440" class="html-bibr">23</a>]. © 2014 Elsevier.</p> Full article ">Figure 2
<p>Schematic presentation of (<b>a</b>) the chamber and (<b>b</b>) the cover.</p> Full article ">Figure 3
<p>SEM image of: (<b>a</b>) Initial archwire surface (control); (<b>b</b>) Deformed archwire surface after the simulation of multiaxial stress equipment (SMAS) simulation test.</p> Full article ">Figure 4
<p>Auger electron spectroscopy (AES) spectra of archwire surfaces: (<b>a</b>) Initial (control); (<b>b</b>) Deformed after the SMAS simulation test.</p> Full article ">Figure 5
<p>AES depth profiles show the concetrations of elements in the direction from the surface to 51 nm in the depth of each of the archwires: (<b>a</b>) Initial (control), (<b>b</b>) Deformed after the SMAS simulation test.</p> Full article ">
12 pages, 13630 KiB  
Article
The Influence of Surface Treatment of PVD Coating on Its Quality and Wear Resistant
by Tomas Zlamal, Ivan Mrkvica, Tomas Szotkowski and Sarka Malotova
Coatings 2019, 9(7), 439; https://doi.org/10.3390/coatings9070439 - 13 Jul 2019
Cited by 26 | Viewed by 5352
Abstract
The article deals with a determination of the influence of a cutting edge preparation on the quality and wear resistance of coated cutting tools. Cutting inserts made from a sintered carbide with a deposited layer of PVD coating were selected for measurement. Non-homogeneity [...] Read more.
The article deals with a determination of the influence of a cutting edge preparation on the quality and wear resistance of coated cutting tools. Cutting inserts made from a sintered carbide with a deposited layer of PVD coating were selected for measurement. Non-homogeneity caused by the creation of droplets arises in the application layer during the process of applying the coating by the PVD method. These droplets make the surface roughness of the PVD coating worse, increase the friction and thereby the thermal load of the cutting tool as well. Also, the droplets could be the cause of the creation and propagation of droplets in the coating and they can cause quick cutting tool wear during machining. Cutting edge preparations were suggested for the improvement of the surface integrity of deposited layers of PVD coating, namely the technology of drag finishing and abrasive jet machining. After their application, the areal surface roughness was measured on the surface of coated cutting inserts, the occurrence of droplets was tracked and the surface structure was explored. A tool-life test of cutting inserts was carried out for verification of the influence of surface treatment on the wear resistance of cutting inserts during the milling process. The cutting inserts with a layer of PVD coatings termed as samples A, B, and C were used for the tool-life test. The first sample, A, represented the coating before the application of cutting edge preparations and samples B and C were after the application of the cutting edge preparation. A carbon steel termed C45 was used for the milling process and cutting conditions were suggested. The visual control of surface of cutting inserts, intensity of wear and occurrence of thermal cracks in deposited PVD layers were the criterion for the evaluation of the individual tests. Full article
(This article belongs to the Special Issue Physical Vapor Deposition)
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<p>Abrasive jet machining process.</p> Full article ">Figure 2
<p>Drag finishing.</p> Full article ">Figure 3
<p>Image of dirties on the surface of tested PVD coating after cutting edge preparation (dark areas) <b>Left</b>—abrasive jet machining, <b>Right</b>—Drag finishing.</p> Full article ">Figure 4
<p>Measurement methods of the length of thermal cracks.</p> Full article ">Figure 5
<p>Damage of PVD coatings during drag finishing (time = 10 min). <b>Left</b>—magnification 1000x; <b>right</b>—magnification 5000x.</p> Full article ">
16 pages, 1741 KiB  
Article
Two Different Scenarios for the Equilibration of Polycation—Anionic Solutions at Water–Vapor Interfaces
by Eduardo Guzmán, Laura Fernández-Peña, Andrew Akanno, Sara Llamas, Francisco Ortega and Ramón G. Rubio
Coatings 2019, 9(7), 438; https://doi.org/10.3390/coatings9070438 - 13 Jul 2019
Cited by 30 | Viewed by 3391
Abstract
The assembly in solution of the cationic polymer poly(diallyldimethylammonium chloride) (PDADMAC) and two different anionic surfactants, sodium lauryl ether sulfate (SLES) and sodium N-lauroyl-N-methyltaurate (SLMT), has been studied. Additionally, the adsorption of the formed complexes at the water–vapor interface have been measured to [...] Read more.
The assembly in solution of the cationic polymer poly(diallyldimethylammonium chloride) (PDADMAC) and two different anionic surfactants, sodium lauryl ether sulfate (SLES) and sodium N-lauroyl-N-methyltaurate (SLMT), has been studied. Additionally, the adsorption of the formed complexes at the water–vapor interface have been measured to try to shed light on the complex physico-chemical behavior of these systems under conditions close to that used in commercial products. The results show that, independently of the type of surfactant, polyelectrolyte-surfactant interactions lead to the formation of kinetically trapped aggregates in solution. Such aggregates drive the solution to phase separation, even though the complexes should remain undercharged along the whole range of explored compositions. Despite the similarities in the bulk behavior, the equilibration of the interfacial layers formed upon adsorption of kinetically trapped aggregates at the water–vapor interface follows different mechanisms. This was pointed out by surface tension and interfacial dilational rheology measurements, which showed different equilibration mechanisms of the interfacial layer depending on the nature of the surfactant: (i) formation layers with intact aggregates in the PDADMAC-SLMT system, and (ii) dissociation and spreading of kinetically trapped aggregates after their incorporation at the fluid interface for the PDADMAC-SLES one. This evidences the critical impact of the chemical nature of the surfactant in the interfacial properties of these systems. It is expected that this work may contribute to the understanding of the complex interactions involved in this type of system to exploit its behavior for technological purposes. Full article
(This article belongs to the Special Issue Fluid Interfaces)
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<p>(<b>a</b>) Binding isotherms for surfactants on PDADMAC as a function of the initial concentration of surfactant in bulk. (<b>b</b>) Surfactant concentration dependences of the optical density of the solution, measured at 400 nm. Note: (□) = PDADMAC-SLMT; (●) = PDADMAC-SLES solutions. Lines are guides for the eyes. The results correspond to PDADMAC-surfactant mixtures containing a fixed PDADMAC concentration of 0.5 wt.%, and left to age for one week prior to measurement.</p> Full article ">Figure 2
<p>Results obtained using a drop profile analysis tensiometer: (<b>a</b>) Surface pressure dependence on surfactant concentration for the adsorption of pure SLES (○) and SLMT (■) at the water–vapor interface; cmc for both surfactants is marked. The inserted panel represents the surface pressure dependence on PDADMAC concentration for the adsorption of pure PDADMAC at the water–vapor interface. (<b>b</b>) Surface pressure dependence of SLMT concentration for pure SLMT (■) and PDADMAC–SLMT (□) solutions. (<b>c</b>) Surface pressure dependence of SLES concentration for pure SLES (○) and PDADMAC–SLES (●) solutions. The lines are guides for the eyes. The results for PDADMAC-surfactant mixtures correspond to mixtures containing a fixed PDADMAC concentration of 0.5 wt.%, and left to age for one week prior to measurement.</p> Full article ">Figure 3
<p>Surface pressure isotherms for solutions of PDADMAC with the two surfactants, obtained using different tensiometers. (<b>a</b>) Isotherms for PDADMAC-SLMT solutions. (<b>b</b>) Isotherms for PDADMAC-SLES solutions. Note: (□ and ■) Surface force tensiometer with Pt Wilhelmy plate as contact probe; (○ and ●) surface force tensiometer with paper Wilhelmy plate as contact probe; (Δ and ▲) drop profile analysis tensiometer. The lines are guides for the eyes. The results correspond to PDADMAC-surfactant mixtures containing a fixed PDADMAC concentration of 0.5 wt.% left to age for one week prior to measurement.</p> Full article ">Figure 4
<p>(<b>a</b>) Dynamic surface pressure for PDADMAC-SLMT solutions with different surfactant concentrations. (<b>b</b>) Dynamic surface pressure for PDADMAC-SLES solutions with different surfactant concentrations. The results correspond to PDADMAC-surfactant mixtures containing a fixed PDADMAC concentration of 0.5 wt.%, and left to age for one week prior to measurement.</p> Full article ">Figure 5
<p>(<b>a</b>) Concentration dependences of the elastic modulus for PDADMAC-SLMT adsorption layers as were obtained from oscillatory barrier experiments performed at different frequencies. (<b>b</b>) Concentration dependences of the elastic modulus for PDADMAC-SLES adsorption layers, obtained from oscillatory barrier experiments performed at different frequencies. Note: (□ and ■) ν = 0.01 Hz; (○ and ●) ν = 0.05 Hz; (Δ and ▲) ν = 0.10 Hz. The lines are guides for the eyes. For the sake of clarity, only results corresponding to some of the explored frequencies (ν) are shown, with the other frequencies presenting similar dependences. The results correspond to PDADMAC-surfactant mixtures containing a fixed PDADMAC concentration of 0.5 wt.%, and left to age for one week prior to measurement.</p> Full article ">Figure 6
<p>(<b>a</b>) Examples of frequency dependences of the elastic modulus for interfacial layers of PDADMAC-SLMT (□) and PDADMAC-SLES (●) and for solutions with surfactant concentration of 0.1 mM. Symbols represent the experimental data and the lines are the theoretical curves obtained from the analysis of the experimental results in term of the theoretical model described by Equation (2). (<b>b</b>) Concentration dependences of <span class="html-italic">ν</span><sub>D</sub> for PDADMAC-SLMT (□) and PDADMAC-SLES (■). (<b>c</b>) Concentration dependences of <span class="html-italic">ν</span><sub>1</sub> for PDADMAC-SLMT (○) and PDADMAC-SLES (●). (<b>b</b>,<b>c</b>) Symbols represent the experimental data and the lines are guides for the eyes. The results correspond to PDADMAC-surfactant mixtures containing a fixed PDADMAC concentration of 0.5 wt.%, and left to age for one week prior to measurement.</p> Full article ">Scheme 1
<p>Molecular formula of the three surfactants used in this work: PDADMAC (<b>a</b>), SLMT (<b>b</b>) and SLES (<b>c</b>).</p> Full article ">
11 pages, 3274 KiB  
Article
Enhancement of Critical Current Density by Establishing a YBa2Cu3O7−x/LaAlO3/YBa2Cu3O7−x Quasi-Trilayer Architecture Using the Sol-Gel Method
by Chuanbao Wu and Yunwei Wang
Coatings 2019, 9(7), 437; https://doi.org/10.3390/coatings9070437 - 13 Jul 2019
Cited by 1 | Viewed by 3139
Abstract
We developed a solution-derived method to establish a YBa2Cu3O7−x/LaAlO3/YBa2Cu3O7−x quasi-trilayer architecture. Using the method, nano-scale pinning sites were induced into the quasi-trilayer architecture and yielded an apparent improvement [...] Read more.
We developed a solution-derived method to establish a YBa2Cu3O7−x/LaAlO3/YBa2Cu3O7−x quasi-trilayer architecture. Using the method, nano-scale pinning sites were induced into the quasi-trilayer architecture and yielded an apparent improvement in the in-field critical current density (Jc) of high-quality YBa2Cu3O7−x (YBCO). The improvement in the in-field Jc of the films was closely related to the thickness of the LaAlO3 (LAO) interlayer. In this paper it is demonstrated that when the nominal interlayer thickness approximates 20 nm, which is slightly higher than the roughness of the YBa2Cu3O7−x surface, the LaAlO3 interlayer is discontinuous due to synchromesh-like growth of the LaAlO3 layer on relatively rough YBa2Cu3O7−x surface resulting from the mobility of the solution. Nanoscale defects, such as particles, some amorphous phases, and especially their concomitant lattice defects (such as stacking faults and plane buckling) arise in YBa2Cu3O7−x layers. These nanoscale defects could play a role in flux pinning and thus enhancing Jc. The effective non-vacuum solution to induce vortex pinning into YBa2Cu3O7−x films could be a reference for the further design of an optimal pinning landscape for higher Jc. Full article
(This article belongs to the Special Issue Superconducting Films and Nanostructures)
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<p>Schematic diagram for YBCO/LAO/YBCO trilayer structure.</p> Full article ">Figure 2
<p>The <span class="html-italic">M-H</span> curves of the YBCO/LAO/YBCO trilayer with LAO thicknesses of (<b>a</b>) 0, (<b>b</b>) 20, (<b>c</b>) 40, and (<b>d</b>) 70 nm.</p> Full article ">Figure 3
<p><span class="html-italic">J<sub>c</sub></span> versus the magnetic field of samples SS and SIS-20.</p> Full article ">Figure 4
<p>XRD patterns of YBCO/LAO/YBCO trilayer films.</p> Full article ">Figure 5
<p>SEM morphologies of the top YBCO layers in YBCO/LAO/YBCO trilayer films with the samples of (<b>a</b>) SS, (<b>b</b>) SIS-20, (<b>c</b>) SIS-40, and (<b>d</b>) SIS-70.</p> Full article ">Figure 5 Cont.
<p>SEM morphologies of the top YBCO layers in YBCO/LAO/YBCO trilayer films with the samples of (<b>a</b>) SS, (<b>b</b>) SIS-20, (<b>c</b>) SIS-40, and (<b>d</b>) SIS-70.</p> Full article ">Figure 6
<p>Cross-section TEM images of YBCO/LAO/YBCO quasi-trilayer (sample SIS-20): (<b>a</b>) shows the overall structure of the quasi-trilayer; (<b>b</b>,<b>c</b>) are the high resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED) of the interface between the bottom YBCO layer and the LAO substrate, respectively; and (<b>d</b>–<b>f</b>) is the HRTEM of the interface between YBCO and LAO films.</p> Full article ">Figure 7
<p>AFM image of YBCO film grown on an LAO substrate by using the low-fluorine rapid sol-gel route. Surface roughness of the YBCO film is 19 nm in <span class="html-italic">R</span><sub>q</sub> (root mean square (RMS)).</p> Full article ">Figure 8
<p>Schematic illustration for enhanced <span class="html-italic">J</span><sub>c</sub> in YBCO/LAO/YBCO quasi-trilayer architecture. In the quasi-trilayer, the LAO layer is discontinuous.</p> Full article ">
12 pages, 5778 KiB  
Article
Tribological Performance of CF-PEEK Sliding against 17-4PH Stainless Steel with Various Cermet Coatings for Water Hydraulic Piston Pump Application
by Songlin Nie, Fangli Lou, Hui Ji and Fanglong Yin
Coatings 2019, 9(7), 436; https://doi.org/10.3390/coatings9070436 - 11 Jul 2019
Cited by 17 | Viewed by 4017
Abstract
To improve the abrasion resistance performance of the critical tribopairs within water hydraulic piston pumps, tribological characteristics of the stainless steel 17-4PH and 17-4PH coated with Cr3C2-NiCr, WC-10Co-4Cr, Cr2O3 and Al2O3-13%TiO2 [...] Read more.
To improve the abrasion resistance performance of the critical tribopairs within water hydraulic piston pumps, tribological characteristics of the stainless steel 17-4PH and 17-4PH coated with Cr3C2-NiCr, WC-10Co-4Cr, Cr2O3 and Al2O3-13%TiO2 sliding against carbon fiber reinforced polyetheretherketone (CF-PEEK) composite under water-lubricated condition were experimentally studied using a pin-on-ring test bench with different working conditions. It has been demonstrated by the experimental results that the tribological behaviors of CF-PEEK/cermet coatings tribipairs were better than that of CF-PEEK/17-4PH tribopair under water lubrication. However, the Cr3C2-NiCr coating could be damaged under high rotational speed. Due to the reaction film produced by the Al2O3-13%TiO2 and water, the CF-PEEK/Al2O3-13%TiO2 material combination exhibits more excellent tribological behaviors than other tribopairs lubricated with water, and could preferentially be used in water hydraulic piston pumps. Full article
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<p>Configurations of a water hydraulic axial piston pump.</p> Full article ">Figure 2
<p>Schematic configuration of the pin-on-disk test: (<b>a</b>) schematic diagram; (<b>b</b>) real photo.</p> Full article ">Figure 3
<p>Friction coefficients of 17-4PH and several coatings sliding against CF-PEEK: (<b>a</b>) 100 N, 100 r/min; (<b>b</b>) 100 N, 300 r/min and (<b>c</b>) the mean friction coefficients.</p> Full article ">Figure 4
<p>The wear rates of several tribopairs: (<b>a</b>) wear rates of CF-PEEK polymers and (<b>b</b>) wear rates of 17-4PH and several cermet coatings.</p> Full article ">Figure 5
<p>Worn surfaces morphology of CF-PEEK when sliding against 17-4PH and several cermet coatings (100 N, 300 r/min): (<b>a</b>) CF-PEEK/17-4PH; (<b>b</b>) CF-PEEK/Cr<sub>3</sub>C<sub>2</sub>-NiCr; (<b>c</b>) CF-PEEK/WC-10Co-4Cr; (<b>d</b>) CF-PEEK/Cr<sub>2</sub>O<sub>3</sub> and (<b>e</b>) CF-PEEK/Al<sub>2</sub>O<sub>3</sub>-13%TiO<sub>2</sub>.</p> Full article ">Figure 5 Cont.
<p>Worn surfaces morphology of CF-PEEK when sliding against 17-4PH and several cermet coatings (100 N, 300 r/min): (<b>a</b>) CF-PEEK/17-4PH; (<b>b</b>) CF-PEEK/Cr<sub>3</sub>C<sub>2</sub>-NiCr; (<b>c</b>) CF-PEEK/WC-10Co-4Cr; (<b>d</b>) CF-PEEK/Cr<sub>2</sub>O<sub>3</sub> and (<b>e</b>) CF-PEEK/Al<sub>2</sub>O<sub>3</sub>-13%TiO<sub>2</sub>.</p> Full article ">Figure 6
<p>Worn surfaces morphology and the corresponding EDS results of different cermet coatings (100 N, 300 r/min): (<b>a</b>) 17-4PH; (<b>b</b>) Cr<sub>3</sub>C<sub>2</sub>-NiCr; (<b>c</b>) WC-10Co-4Cr; (<b>d</b>) Cr<sub>2</sub>O<sub>3</sub> and (<b>e</b>) Al<sub>2</sub>O<sub>3</sub>-13%TiO<sub>2</sub>.</p> Full article ">Figure 6 Cont.
<p>Worn surfaces morphology and the corresponding EDS results of different cermet coatings (100 N, 300 r/min): (<b>a</b>) 17-4PH; (<b>b</b>) Cr<sub>3</sub>C<sub>2</sub>-NiCr; (<b>c</b>) WC-10Co-4Cr; (<b>d</b>) Cr<sub>2</sub>O<sub>3</sub> and (<b>e</b>) Al<sub>2</sub>O<sub>3</sub>-13%TiO<sub>2</sub>.</p> Full article ">Figure 7
<p>Worn surface scars of the lower specimens (100 N, 300 r/min): (<b>a</b>) 17-4PH; (<b>b</b>) Cr<sub>3</sub>C<sub>2</sub>-NiCr; (<b>c</b>) WC-10Co-4Cr; (<b>d</b>) Cr<sub>2</sub>O<sub>3</sub> and (<b>e</b>) Al<sub>2</sub>O<sub>3</sub>-13%TiO<sub>2</sub>.</p> Full article ">
9 pages, 1682 KiB  
Article
PL Study on the Effect of Cu on the Front Side Luminescence of CdTe/CdS Solar Cells
by Halina Opyrchal, Dongguo Chen, Zimeng Cheng and Ken Chin
Coatings 2019, 9(7), 435; https://doi.org/10.3390/coatings9070435 - 11 Jul 2019
Cited by 3 | Viewed by 3262
Abstract
The effect of Cu on highly efficient CdTe thin solid film cells with a glass/TCO/CdS/CdTe structure subjected to CdCl2 treatment was investigated by low-temperature photoluminescence (PL). The PL of the CdS/CdTe junction in samples without Cu deposition revealed a large shift in [...] Read more.
The effect of Cu on highly efficient CdTe thin solid film cells with a glass/TCO/CdS/CdTe structure subjected to CdCl2 treatment was investigated by low-temperature photoluminescence (PL). The PL of the CdS/CdTe junction in samples without Cu deposition revealed a large shift in the bound exciton position due to the formation of CdSxTe1−x alloys with Eg (alloy) ≅ 1.557 eV at the interface region. After Cu deposition on the CdTe layer and subsequent heat treatment, a neutral acceptor-bound exciton (A0Cu,X) line at 1.59 eV and two additional band-edge peaks at 1.54 and 1.56 eV were observed, indicating an increase in the energy gap value in the vicinity of the CdTe/CdS interface to that characteristic of bulk CdTe. These results may suggest the disappearance of the intermixing phase at the CdTe/CdS interface due to the presence of Cu atoms in the junction area and the interaction of the Cu with sulfur atoms. Furthermore, an increase in the intensity of CdS-related peaks in Cu-doped samples was observed, implying that Cu atoms were incorporated into CdS after heat treatment. Full article
(This article belongs to the Special Issue Advanced Thin Film Materials for Photovoltaic Applications)
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<p>The glass substrate represents the front side of a solar cell and the CdTe layer represents the backside of a solar cell. The glass substrate, SnO<sub>2</sub>, and CdS layers are transparent to a 658 nm line that is absorbed only by the CdTe film at the interface (junction luminescence).</p> Full article ">Figure 2
<p>Backside luminescence (10 K) of CdS/CdTe solar cells grown in the NREL laboratory and CNBM New Energy Materials Research Center, respectively.</p> Full article ">Figure 3
<p>Photoluminescence (PL) spectra (10 K) from undoped CdS/CdTe solar cells excited from the backside (full line) and front side (dotted line) of the cell.</p> Full article ">Figure 4
<p>Temperature dependence of the PL intensity of the 1.53 transition in undoped cells along with the two-activation energy fit.</p> Full article ">Figure 5
<p>Front side luminescence of Cu-doped (full line) and undoped (dotted line) CdS/CdTe solar cells taken at 10 K.</p> Full article ">Figure 6
<p>Front side luminescence (10 K) from Cu-doped (solid line) and undoped (dotted line) CdS/CdTe solar cells excited by the 405 nm line.</p> Full article ">
18 pages, 12965 KiB  
Article
Enhancement of Tribological Behavior of Rolling Bearings by Applying a Multilayer ZrN/ZrCN Coating
by Isabel Clavería, Aleida Lostalé, Ángel Fernández, Pere Castell, Daniel Elduque, Gemma Mendoza and Cristina Zubizarreta
Coatings 2019, 9(7), 434; https://doi.org/10.3390/coatings9070434 - 10 Jul 2019
Cited by 14 | Viewed by 4411
Abstract
This paper focuses on the tribological behaviour of ZrN/ZrCN coating on bearing steel substrates DIN 17230, 100Cr6/1.3505. Coatings are applied at room temperature processes by means of Cathodic Arc Evaporation (CAE), a kind of Physical Vapor Deposition (PVD) technique. In order to achieve [...] Read more.
This paper focuses on the tribological behaviour of ZrN/ZrCN coating on bearing steel substrates DIN 17230, 100Cr6/1.3505. Coatings are applied at room temperature processes by means of Cathodic Arc Evaporation (CAE), a kind of Physical Vapor Deposition (PVD) technique. In order to achieve a satisfactory compromise between coating-substrate adhesion and the surface roughness requirement of the bearing rings, a polish post-processing is proposed. Different polish post-processing times and conditions are applied. The coated and polished bearing rings are tested under real friction torque test protocols. These tests show that the application of the coating does not entail a significant improvement in friction performance of the bearing. However, fatigue tests in real test bench are pending to evaluate the possible improvement in bearing life time. Full article
(This article belongs to the Special Issue Selected Papers from the 1st Coatings and Interfaces Web Conference (CIWC-1))
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<p>Tapered roller bearing 594A/592A.</p> Full article ">Figure 2
<p>Measured profiles: (<b>a</b>) inner ring raceway profile; (<b>b</b>) flange profile.</p> Full article ">Figure 3
<p>Chart VDI 3198 indentation test.</p> Full article ">Figure 4
<p>Inner raceway profile (logarithmic) for (<b>a</b>) Uncoated bearing; (<b>b</b>) uncoated bearing at the selected area in (<b>a</b>), (<b>c</b>) coated bearing; and (<b>d</b>) coated bearing at the selected area in (<b>c</b>).</p> Full article ">Figure 5
<p>Flange profile for (<b>a</b>) Uncoated bearing; (<b>b</b>) uncoated bearing at the selected area in (<b>a</b>), (<b>c</b>) coated bearing; and (<b>d</b>) coated bearing at the selected area in (<b>c</b>).</p> Full article ">Figure 6
<p>Inner ring raceway diameter shape.</p> Full article ">Figure 7
<p>Example of GIXRD spectrum of a ZrCN coating.</p> Full article ">Figure 8
<p>D1 design coating composition graphic obtained by GD-OES.</p> Full article ">Figure 9
<p>Optical and SEM images for D1 coating; (<b>a</b>) adhesion results (optical); (<b>b</b>,<b>c</b>) surface, and cross-section micrographs.</p> Full article ">Figure 10
<p>Optical and SEM images for D2 coating; (<b>a</b>) adhesion results (optical); (<b>b</b>) surface micrograph.</p> Full article ">Figure 11
<p>SEM images for D3 coating; (<b>a</b>) adhesion results; (<b>b</b>,<b>c</b>) D3 surface, and cross-section micrographs.</p> Full article ">Figure 12
<p>D4 adhesion results.</p> Full article ">Figure 13
<p>Bearing samples D4 coating + B polish post-processing.</p> Full article ">Figure 14
<p>Relation between tempering temperature and hardness (<b>a</b>) Martensitic through hardening treatment; (<b>b</b>) tempering temperature vs hardness [<a href="#B50-coatings-09-00434" class="html-bibr">50</a>].</p> Full article ">Figure 15
<p>594A/592A ZrCN + polish post-processing Stribeck friction test 8 kN.</p> Full article ">Figure 16
<p>594A/592A ZrCN + polish post-processing TTR friction test 0–15 kN, 30 rpm.</p> Full article ">Figure 17
<p>594A/592A ZrCN + polish post-processing TTR friction test vs Baseline.</p> Full article ">
12 pages, 4474 KiB  
Article
Size-Controlled Transparent Jute Fiber for Replacing Transparent Wood in Industry Production Area
by Tianshi Feng, Jiankun Qin, Yali Shao, Lili Jia, Qi Li and Yingcheng Hu
Coatings 2019, 9(7), 433; https://doi.org/10.3390/coatings9070433 - 10 Jul 2019
Cited by 8 | Viewed by 4797
Abstract
Transparent jute fiber (TJF) was prepared from delignified jute fiber (DJF) and was subjected to various surface knitting densities (190 and 340 g/m2) before epoxy resin (ER) impregnation under vacuum. The preparation process and properties of TJF were evaluated. The mechanical [...] Read more.
Transparent jute fiber (TJF) was prepared from delignified jute fiber (DJF) and was subjected to various surface knitting densities (190 and 340 g/m2) before epoxy resin (ER) impregnation under vacuum. The preparation process and properties of TJF were evaluated. The mechanical properties and surface morphology of the jute fiber samples were also studied. The mechanical properties were compared with transparent coir fiber (TCF) and transparent balsa wood (TBW). Optical properties, such as surface color, optical transmittance, and visual haze, of natural jute fiber (JF) and TJF were measured to better understand the influence of delignification. The experimental results showed transparency of 51% even for dense jute fiber cloth, and the maximum transmittance was as high as 60% with a low surface density. TJF had similar tensile strength as TBW but was higher than TCF, indicating a maximum tensile strength of 43.25 MPa with a surface density of 340 g/m2. These results suggest that TJF has the potential to meet the particular optical and mechanical properties of transparent wood. Transparent jute fiber can replace transparent wood for industrial production because of the simple preparation process and lower price. Full article
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<p>Sparse (<b>a</b>) and dense (<b>b</b>) jute fibers.</p> Full article ">Figure 2
<p>Flow chart to prepare transparent jute fibers.</p> Full article ">Figure 3
<p>Photographs of the TJF190 (<b>a</b>) and TJF340 (<b>b</b>) products and epoxy resin (<b>c</b>) under an incandescent lamp.</p> Full article ">Figure 4
<p>Photographs of DJF190 (<b>b</b>) and DJF340 (<b>d</b>) compared with the raw materials JF190 (<b>a</b>) and JF340 (<b>c</b>) under an incandescent lamp.</p> Full article ">Figure 5
<p>Photographs of TJF190 (<b>b</b>) and TJF340 (<b>d</b>) compared with raw materials JF190 (<b>a</b>) and JF340 (<b>c</b>) under an incandescent lamp.</p> Full article ">Figure 6
<p>Photographs of TJF190 (<b>b</b>)/TJF340 (<b>d</b>) treated with hydrogen peroxide solution and UTJF190 (<b>a</b>)/UTJF340 (<b>c</b>) treated without hydrogen peroxide solution under an incandescent lamp.</p> Full article ">Figure 7
<p>Scanning electron micrographs of jute fibers and transparent jute fibers.</p> Full article ">Figure 8
<p>Photographs of TJF190 and TJF340 in the macro-transparent jute fibers.</p> Full article ">Figure 9
<p>Mechanical properties of epoxy resin–jute fiber (ER–JF) composites: (<b>a</b>) tensile strength-strain curve of four kinds of jute fiber; (<b>b</b>) tensile strength and Young’s modulus of four kinds of jute fiber.</p> Full article ">Figure 10
<p>Energy absorption and ultimate elongation of jute fiber composites.</p> Full article ">Figure 11
<p>Transparency of transparent biomass materials at 300–800 nm.</p> Full article ">
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