Coatings

8 pages, 3576 KiB

Open AccessArticle

Effect of Surface Roughness and Electroless Ni–P Plating on the Bonding Strength of Bi–Te-based Thermoelectric Modules

by Sung Hwa Bae, Sungsoon Kim, Seong Hoon Yi, Injoon Son, Kyung Tae Kim and Hoyong Chung

Coatings 2019, 9(3), 213; https://doi.org/10.3390/coatings9030213 - 26 Mar 2019

Cited by 10 | Viewed by 4867

In this study, electroless-plating of a nickel-phosphor (Ni–P) thin film on surface-controlled thermoelectric elements was developed to significantly increase the bonding strength between Bi–Te materials and copper (Cu) electrodes in thermoelectric modules. Without electroless Ni–P plating, the effect of surface roughness on the [...] Read more.

In this study, electroless-plating of a nickel-phosphor (Ni–P) thin film on surface-controlled thermoelectric elements was developed to significantly increase the bonding strength between Bi–Te materials and copper (Cu) electrodes in thermoelectric modules. Without electroless Ni–P plating, the effect of surface roughness on the bonding strength was negligible. Brittle SnTe intermetallic compounds were formed at the bonding interface of the thermoelectric elements and defects such as pores were generated at the bonding interface owing to poor wettability with the solder. However, defects were not present at the bonding interface of the specimen subjected to electroless Ni–P plating, and the electroless Ni–P plating layer acted as a diffusion barrier toward Sn and Te. The bonding strength was higher when the specimen was subjected to Ni–P plating compared with that without Ni–P plating, and it improved with increasing surface roughness. As electroless Ni–P plating improved the wettability with molten solder, the increase in bonding strength was attributed to the formation of a thicker solder reaction layer below the bonding interface owing to an increase in the bonding interface with the solder at higher surface roughness. Full article

(This article belongs to the Special Issue Thin Films for Thermoelectric Applications)

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8 pages, 5010 KiB

Open AccessArticle

Sol-Gel and Electrospinning Synthesis of Lithium Niobate-Silica Nanofibers

by Jesús Alberto Garibay-Alvarado, Rurik Farías and Simón Yobanny Reyes-López

Coatings 2019, 9(3), 212; https://doi.org/10.3390/coatings9030212 - 26 Mar 2019

Cited by 15 | Viewed by 4400

Abstract

Lithium niobate-silica fibers were produced by the combination of the sol-gel method and the electrospinning technique. Two sol-gel solutions starting from niobium-lithium ethoxide and tetraethyl orthosilicate were prepared and then mixed with polyvinylpyrrolidone; the solutions were electrospun in a coaxial setup. The obtained [...] Read more.

Lithium niobate-silica fibers were produced by the combination of the sol-gel method and the electrospinning technique. Two sol-gel solutions starting from niobium-lithium ethoxide and tetraethyl orthosilicate were prepared and then mixed with polyvinylpyrrolidone; the solutions were electrospun in a coaxial setup. The obtained lithium niobate-silica polymeric fibers were approximately 760 nm in diameter. Raman spectroscopy confirmed the composite composition by showing signals corresponding to lithium niobate and silica. Scanning electron microscopy showed coaxial fibers with a diameter of around 330 nm arranged as a fibrillar membrane at 800 °C. At 1000 °C the continuous shape of fibers was preserved; the structure is composed of silica and lithium niobate nanoparticles within the fibers. The formation of crystalline lithium niobate and amorphous SiO₂ phase was also confirmed by XRD peaks. Full article

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13 pages, 2871 KiB

Open AccessArticle

Analysis of Unsteady Flow and Heat Transfer of Nanofluid Using Blasius–Rayleigh–Stokes Variable

by Dianchen Lu, Sumayya Mumtaz, Umer Farooq and Adeel Ahmad

Coatings 2019, 9(3), 211; https://doi.org/10.3390/coatings9030211 - 25 Mar 2019

Cited by 7 | Viewed by 2941

Abstract

This article investigates the unsteady flow and heat transfer analyses of a viscous-based nanofluid over a moving surface emerging from a moving slot. This new form of boundary layer flow resembles with the boundary layer flow over a stretching/shrinking surface depending on the [...] Read more.

This article investigates the unsteady flow and heat transfer analyses of a viscous-based nanofluid over a moving surface emerging from a moving slot. This new form of boundary layer flow resembles with the boundary layer flow over a stretching/shrinking surface depending on the motion of the moving slot. The governing partial differential equations are transformed to correct similar form using the Blasius–Rayleigh–Stokes variable. The transformed equations are solved numerically. Existence of dual solutions is observed for a certain range of moving slot parameter. The range of dual solution is strongly influenced by Brownian and thermophoretic diffusion of nanoparticles. Full article

(This article belongs to the Special Issue Recent Trends in Coatings and Thin Film–Modeling and Application)

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10 pages, 4062 KiB

Open AccessArticle

Anticorrosion Properties of Zn–Al Composite Coating Prepared by Cold Spraying

by Xinqiang Lu, Shouren Wang, Tianying Xiong, Daosheng Wen, Gaoqi Wang and Hao Du

Coatings 2019, 9(3), 210; https://doi.org/10.3390/coatings9030210 - 25 Mar 2019

Cited by 11 | Viewed by 3643

Abstract

In order to slow down the corrosion and wear of offshore equipment, the Zn–Al composite coating was prepared on Q345 substrate by cold spray technique. The mass fraction of Zn and Al in the raw material was 2:3. The microstructure of the original [...] Read more.

In order to slow down the corrosion and wear of offshore equipment, the Zn–Al composite coating was prepared on Q345 substrate by cold spray technique. The mass fraction of Zn and Al in the raw material was 2:3. The microstructure of the original coating was observed by scanning electron microscopy (SEM) and was characterized by energy dispersive spectrometer (EDS). From the composite alloy coating obtained by cold spraying, it was observed that the Zn and Al particles were uniformly distributed without oxidation product, and the powder particles were significantly plastically deformed. The microstructure of the composite coating is very dense and has strong adhesion to the substrate. Neutral salt spray test (NSS) and electrochemical accelerated corrosion test results showed that Zn–Al composite coating can effectively provide corrosion protection. Full article

(This article belongs to the Special Issue Corrosion and Electrochemical Behavior of Metals Coating)

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10 pages, 23748 KiB

Open AccessArticle

Improved Adhesion of TiAlSiN Nanocomposite Coatings on Cemented Carbide Substrate by Pre-Implantation

by Lei Wang, Liuhe Li, Guodong Li and Quansheng Ma

Coatings 2019, 9(3), 209; https://doi.org/10.3390/coatings9030209 - 25 Mar 2019

Cited by 11 | Viewed by 3522

Abstract

TiAlSiN coatings were deposited on YT 15 cemented carbide substrate by reactive direct current magnetron sputtering (DCMS) in a Plasma Immersion Ion Implantation and Deposition (PIII&D) system. The pre-implantation step and the coating deposition were carried out in the same experimental facility. In [...] Read more.

TiAlSiN coatings were deposited on YT 15 cemented carbide substrate by reactive direct current magnetron sputtering (DCMS) in a Plasma Immersion Ion Implantation and Deposition (PIII&D) system. The pre-implantation step and the coating deposition were carried out in the same experimental facility. In this article the effects of pre-implantation of several different elements (N, C, and O) were investigated. The adhesion strength, hardness, micro-structure, element concentration, depth profile, and the formation of coatings after the PIII experiments were characterized by a wide variety of techniques such as Rockwell indentation, scratch test, nano-indentation measurement, X-ray diffraction, energy dispersive spectroscopy, and Auger electron spectroscopy. The results showed that the adhesive strength of TiAlSiN coatings was significantly improved on samples pre-implanted with N and O whereas only slightly improved with pre-implantation of C. Additionally, the microstructure and mechanical properties of the TiAlSiN coatings were also altered through pre-implantation. The improved adhesion could be explained by the grain refinement and surface energy enhancement of the substrate by pre-implantation. Full article

(This article belongs to the Special Issue Advanced Thin Films Deposited by Magnetron Sputtering)

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6 pages, 2891 KiB

Open AccessArticle

The Fabrication of a UV Notch Filter by Using Solid State Diffusion

by Hung-Pin Chen, Wen-Hao Cho, Wei-Chun Chen, Chao-Te Lee and Cheng-Chung Lee

Coatings 2019, 9(3), 208; https://doi.org/10.3390/coatings9030208 - 23 Mar 2019

Cited by 1 | Viewed by 2846

Abstract

One of the methods used to obtain notch filters involves one or several gradient index layers. In this method, the indices are decreased and then increased step by step to create a sinusoidal-like gradient layer. This paper reports a sinusoidal-like gradient layer fabrication [...] Read more.

One of the methods used to obtain notch filters involves one or several gradient index layers. In this method, the indices are decreased and then increased step by step to create a sinusoidal-like gradient layer. This paper reports a sinusoidal-like gradient layer fabrication method based on solid state diffusion. Al₂O₃/MgO/Al₂O₃ (AMA) was deposited by electron beam evaporation and then post-annealed at 800 °C for 4 h. Through inner diffusion, the MgO layers became a low refractive index material with a porous structure (the average refractive index was 1.55) such that the MgAl₂O₄ spinel was formed as an inhomogeneous layer with an average refractive index of 1.69. This allowed simply using a structured multilayer, (Al₂O₃/MgO)⁸ Al₂O₃, and post-annealing to form a sinusoidal-like gradient layer for a UV notch filter. Full article

(This article belongs to the Special Issue Design, Manufacturing and Measurement of Optical Film Coatings)

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22 pages, 19228 KiB

Open AccessArticle

Electrodeposition of Hydroxyapatite Coatings for Marble Protection: Preliminary Results

by Enrico Sassoni, Giulia Masi, Maria Chiara Bignozzi and Elisa Franzoni

Coatings 2019, 9(3), 207; https://doi.org/10.3390/coatings9030207 - 23 Mar 2019

Cited by 10 | Viewed by 3464

Abstract

Surface coatings made of hydroxyapatite (HAP) have been proposed to protect marble artworks from dissolution in rain, originated by the aqueous solubility of calcite. However, HAP coatings formed by wet chemistry exhibit incomplete coverage of marble surface, which results in limited protective efficacy. [...] Read more.

Surface coatings made of hydroxyapatite (HAP) have been proposed to protect marble artworks from dissolution in rain, originated by the aqueous solubility of calcite. However, HAP coatings formed by wet chemistry exhibit incomplete coverage of marble surface, which results in limited protective efficacy. In this study, electrodeposition was explored as a new route to possibly form continuous coatings over the marble surface, leaving no bare areas. Electrodeposition was performed by placing marble samples in poultices containing the electrolyte (an aqueous solution with calcium and phosphate precursors) and the electrodes. The influence of several parameters was investigated, namely the role of the working electrode (cathode or anode), the distance between the marble sample and the working electrode, the deposition conditions (potentiostatic or galvanostatic), the electrolyte composition and concentration, the applied voltage, and time. The coating morphology and composition were assessed by SEM/EDS and FT-IR. The protective ability of the most promising formulations was then evaluated, in all cases comparing electrodeposition with traditional wet synthesis methods. The results of the study suggest that electrodeposition is able to accelerate and improve formation of HAP coatings over the marble surface, even though the obtained protective efficacy is not complete yet. Full article

(This article belongs to the Special Issue Ion-Substituted Calcium Phosphates Coatings)

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14 pages, 2522 KiB

Open AccessFeature PaperArticle

Correlative Experimental and Theoretical Investigation of the Angle-Resolved Composition Evolution of Thin Films Sputtered from a Compound Mo₂BC Target

by Jan-Ole Achenbach, Stanislav Mráz, Daniel Primetzhofer and Jochen M. Schneider

Coatings 2019, 9(3), 206; https://doi.org/10.3390/coatings9030206 - 22 Mar 2019

Cited by 13 | Viewed by 3904

Abstract

The angle-resolved composition evolution of Mo-B-C thin films deposited from a Mo₂BC compound target was investigated experimentally and theoretically. Depositions were carried out by direct current magnetron sputtering (DCMS) in a pressure range from 0.09 to 0.98 Pa in Ar and [...] Read more.

The angle-resolved composition evolution of Mo-B-C thin films deposited from a Mo₂BC compound target was investigated experimentally and theoretically. Depositions were carried out by direct current magnetron sputtering (DCMS) in a pressure range from 0.09 to 0.98 Pa in Ar and Kr. The substrates were placed at specific angles α with respect to the target normal from 0 to ±67.5°. A model based on TRIDYN and SIMTRA was used to calculate the influence of the sputtering gas on the angular distribution function of the sputtered species at the target, their transport through the gas phase, and film composition. Experimental pressure- and sputtering gas-dependent thin film chemical composition data are in good agreement with simulated angle-resolved film composition data. In Ar, the pressure-induced film composition variations at a particular α are within the error of the EDX measurements. On the contrary, an order of magnitude increase in Kr pressure results in an increase of the Mo concentration measured at α = 0° from 36 at.% to 43 at.%. It is shown that the mass ratio between sputtering gas and sputtered species defines the scattering angle within the collision cascades in the target, as well as for the collisions in the gas phase, which in turn defines the angle- and pressure-dependent film compositions. Full article

(This article belongs to the Special Issue Advanced Strategies in Thin Film Engineering by Magnetron Sputtering)

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11 pages, 658 KiB

Open AccessArticle

Efficacy of Sweet Potato Starch-Based Coating to Improve Quality and Safety of Hen Eggs during Storage

by Abdulhakim Sharaf Eddin and Reza Tahergorabi

Coatings 2019, 9(3), 205; https://doi.org/10.3390/coatings9030205 - 22 Mar 2019

Cited by 17 | Viewed by 4866

Abstract

Egg deterioration occurs during storage time, which leads to quality loss. Thus, different preservations methods have been used to extend the shelf-life and maintain the safety of eggs. Edible coating materials based on biopolymers, such as starches and other renewable sources, have been [...] Read more.

Egg deterioration occurs during storage time, which leads to quality loss. Thus, different preservations methods have been used to extend the shelf-life and maintain the safety of eggs. Edible coating materials based on biopolymers, such as starches and other renewable sources, have been used for different food products and been identified as an effective method of food preservation. In this study, eggs were coated with edible coatings prepared from sweet potato starch (SPS) and varying levels of thyme essential oil (TEO), including 0 (control), 2%, 4%, and 6%. The quality and safety of the coated and uncoated eggs during five weeks of storage at 25 °C were studied. The application of 4% TEO in SPS-based coatings maintained the quality and safety of eggs two weeks longer than non-coated eggs. This study showed that the SPS-TEO coating could be useful in extending the shelf life of eggs during storage time, by delaying changes in egg quality. Full article

(This article belongs to the Special Issue Films and Coatings for Food and Health Applications)

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14 pages, 4034 KiB

Open AccessArticle

The Dielectric Properties Improvement of Cable Insulation Layer by Different Morphology Nanoparticles Doping into LDPE

by Guang Yu, Yujia Cheng and Xiaohong Zhang

Coatings 2019, 9(3), 204; https://doi.org/10.3390/coatings9030204 - 21 Mar 2019

Cited by 13 | Viewed by 2879

Abstract

Low density polyethylene (LDPE) doped with inorganic nano-MMT and nano-ZnO particles improved the dielectric properties of the cable insulation layer. In this article, nano-MMT/LDPE and nano-ZnO/LDPE composites were prepared by polymer intercalation and melt blending, respectively. The octadecyl quaternary ammonium salt and silane [...] Read more.

Low density polyethylene (LDPE) doped with inorganic nano-MMT and nano-ZnO particles improved the dielectric properties of the cable insulation layer. In this article, nano-MMT/LDPE and nano-ZnO/LDPE composites were prepared by polymer intercalation and melt blending, respectively. The octadecyl quaternary ammonium salt and silane coupling agent were applied for surface modification in nano-MMT and nano-ZnO particles, and this then improved the compatibility of nanoparticles and polymeric matrix. These samples were characterized by FTIR, PLM, DSC and TSC, from which the effect of nanoparticles doping on polymer crystal habit and interface traps would be explored. In these experiments, the AC breakdown characteristics and space charge characteristic of different composites were studied. The experimental results showed that the interface bonding of nanoparticles and polymer was improved by coupling agents modifying. The dispersion of nanoparticles in matrix was better. When the mass fraction of nanoparticles doping was 3 wt.%, the crystallization rate and crystallinity of composites increased, and the crystalline structure was more complete. Besides, the amorphous regions in material decreased and the conducting channel was circuitous. At this time, the breakdown field strength of nano-MMT/LDPE and nano-ZnO/LDPE increased by 10.3% and 11.1%, compared to that of pure LDPE, respectively. Furthermore, the density and depth of interface traps in polymer increased with nanoparticles doping. Nano-MMT and nano-ZnO could both restrain the space charge accumulation, and the inhibiting effect of nano-ZnO was more visible. Full article

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13 pages, 2549 KiB

Open AccessArticle

Silicon Phthalocyanines as Acceptor Candidates in Mixed Solution/Evaporation Processed Planar Heterojunction Organic Photovoltaic Devices

by Marie D. M. Faure, Trevor M. Grant and Benoît H. Lessard

Coatings 2019, 9(3), 203; https://doi.org/10.3390/coatings9030203 - 21 Mar 2019

Cited by 15 | Viewed by 3615

Abstract

Silicon phthalocyanines (SiPc) are showing promise as both ternary additives and non-fullerene acceptors in organic photovoltaics (OPVs) as a result of their ease of synthesis, chemical stability and strong absorption. In this study, bis(3,4,5-trifluorophenoxy) silicon phthalocyanine ((345F)₂-SiPc)) and bis(2,4,6-trifluorophenoxy) silicon phthalocyanine [...] Read more.

Silicon phthalocyanines (SiPc) are showing promise as both ternary additives and non-fullerene acceptors in organic photovoltaics (OPVs) as a result of their ease of synthesis, chemical stability and strong absorption. In this study, bis(3,4,5-trifluorophenoxy) silicon phthalocyanine ((345F)₂-SiPc)) and bis(2,4,6-trifluorophenoxy) silicon phthalocyanine ((246F)₂-SiPc)) are employed as acceptors in mixed solution/evaporation planar heterojunction (PHJ) devices. The donor layer, either poly(3-hexylthiophene) (P3HT) or poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT), was spin coated followed by the evaporation of the SiPc acceptor thin film. Several different donor/acceptor combinations were investigated in addition to investigations to determine the effect of film thickness on device performance. Finally, the effects of annealing, prior to SiPc deposition, after SiPc deposition, and during SiPc deposition were also investigated. The devices which performed the best were obtained using PCDTBT as the donor, with a 90 nm film of (345F)₂-SiPc as the acceptor, followed by thermal annealing at 150 °C for 30 min of the entire mixed solution/evaporation device. An open-circuit voltage (Voc) of 0.88 V and a fill factor (FF) of 0.52 were achieved leading to devices that outperformed corresponding fullerene-based PHJ devices. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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15 pages, 3436 KiB

Open AccessArticle

Photocatalytic and Photostability Behavior of Ag- and/or Al-Doped ZnO Films in Methylene Blue and Rhodamine B under UV-C Irradiation

by Adeel Riaz, Amna Ashraf, Hymna Taimoor, Sofia Javed, Muhammad Aftab Akram, Mohammad Islam, Mohammad Mujahid, Iftikhar Ahmad and Khalid Saeed

Coatings 2019, 9(3), 202; https://doi.org/10.3390/coatings9030202 - 20 Mar 2019

Cited by 35 | Viewed by 4705

Abstract

Silver (Ag) and/or aluminum (Al)-doped zinc oxide (ZnO:Ag, ZnO:Al) films with different concentrations were produced using sol-gel process and investigated for wettability and photocatalysis. Water contact angle (CA) measurements indicated the films to be hydrophilic with reduced solid/liquid interfacial surface energy upon metal [...] Read more.

Silver (Ag) and/or aluminum (Al)-doped zinc oxide (ZnO:Ag, ZnO:Al) films with different concentrations were produced using sol-gel process and investigated for wettability and photocatalysis. Water contact angle (CA) measurements indicated the films to be hydrophilic with reduced solid/liquid interfacial surface energy upon metal doping. The films were highly transparent (>94%) with red or blue shift in the absorption edge depending on the dopant type (Ag or Al) owing to the Burstein–Moss effect. The ZnO:Ag and ZnO:Al films with 0.5 and 1.0 wt.% metal dopant showed high degradation efficiency in methylene blue (MB) solution under UV irradiation, mainly due to an increase in the photogenerated electron–hole pair recombination time and hydroxyl radicals (·OH) generation. The MB degradation followed pseudo-first-order reaction with maximum apparent reaction rate constant of 2.40 h⁻¹ for the 0.5 wt.% ZnO:Al film. ZnO films with 1.0 wt.% dopant demonstrated excellent photostability and recyclability even after several runs presumably due to reduced Zn²⁺ dissolution as well as blocking of the active surface area. ZnO:(Ag + Al) film containing 0.5 wt.% Al and Ag showed excellent UV photodegradation of MB and rhodamine blue (RhB) with high levels of photostability over five cycles. Full article

(This article belongs to the Special Issue Advances in Zinc Oxide Thin Films: Synthesis, Properties and Applications)

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11 pages, 7214 KiB

Open AccessArticle

Preparation of Hierarchically Structured Polystyrene Surfaces with Superhydrophobic Properties by Plasma-Assisted Fluorination

by Martin Minařík, Erik Wrzecionko, Antonín Minařík, Ondřej Grulich, Petr Smolka, Lenka Musilová, Ita Junkar, Gregor Primc, Barbora Ptošková, Miran Mozetič and Aleš Mráček

Coatings 2019, 9(3), 201; https://doi.org/10.3390/coatings9030201 - 20 Mar 2019

Cited by 16 | Viewed by 3406

Abstract

The nanotexturing of microstructured polystyrene surfaces through CF₄ plasma chemical fluorination is presented in this study. It is demonstrated that the parameters of a surface micropore-generation process, together with the setup of subsequent plasma-chemical modifications, allows for the creation of a long-term [...] Read more.

The nanotexturing of microstructured polystyrene surfaces through CF₄ plasma chemical fluorination is presented in this study. It is demonstrated that the parameters of a surface micropore-generation process, together with the setup of subsequent plasma-chemical modifications, allows for the creation of a long-term (weeks) surface-stable micro- and nanotexture with high hydrophobicity (water contact angle >150°). Surface micropores were generated initially via the time-sequenced dosing of mixed solvents onto a polystyrene surface (Petri dish) in a spin-coater. In the second step, tetrafluoromethane (CF₄) plasma fluorination was used for the generation of a specific surface nanotexture and the modulation of the surface chemical composition. Experimental results of microscopic, goniometric, and spectroscopic measurements have shown that a single combination of phase separation methods and plasma processes enables the facile preparation of a wide spectrum of hierarchically structured surfaces differing in their wetting properties and application potentials. Full article

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15 pages, 11479 KiB

Open AccessFeature PaperArticle

Coating of Titanium Substrates with ZrO₂ and ZrO₂-SiO₂ Composites by Sol-Gel Synthesis for Biomedical Applications: Structural Characterization, Mechanical and Corrosive Behavior

by Michelina Catauro, Federico Barrino, Massimiliano Bononi, Elena Colombini, Roberto Giovanardi, Paolo Veronesi and Elisabetta Tranquillo

Coatings 2019, 9(3), 200; https://doi.org/10.3390/coatings9030200 - 19 Mar 2019

Cited by 31 | Viewed by 5853

Abstract

The use of metallic materials as implants presents some major drawbacks, such as their harmful effects on the living organism, especially those induced by corrosion. To overcome this problem, the implant surface of titanium implants can be improved using a coating of bioactive [...] Read more.

The use of metallic materials as implants presents some major drawbacks, such as their harmful effects on the living organism, especially those induced by corrosion. To overcome this problem, the implant surface of titanium implants can be improved using a coating of bioactive and biocompatible materials. The aim of this work is the synthesis of SiO₂/ZrO₂ composites with different percentages of zirconia matrix (20, 33 and 50 wt.%), by the sol-gel method to coat commercial Grade 4 titanium disks using a dip coater. Attenuated total reflectance Fourier transform infrared (ATR/FTIR) spectroscopy was used to evaluate the interactions between the inorganic matrices. Furthermore, the mechanical properties and corrosive behavior of the SiO₂/ZrO₂ coatings were evaluated as a function of the ZrO₂ content. The bioactive properties of the substrate coated with different composites were evaluated using simulated body fluid (SBF). The antibacterial activity was tested against gram-negative and gram-positive Escherichia coli and Enterococcus faecalis, respectively, to assess the release of toxic products from the different composites and to evaluate the possibility of using them in the biomedical field. Full article

(This article belongs to the Special Issue Thin Films and Coatings by Sol-Gel Chemistry: Synthesis, Characterization and Applications)

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18 pages, 31754 KiB

Open AccessArticle

The Evaluation on Corrosion Resistance and Dross Formation of Zn–23 wt % Al–0.3 wt % Si–x wt % Mg Alloy

by Wangjun Peng, Guangxin Wu, Rui Lu, Quanyong Lian and Jieyu Zhang

Coatings 2019, 9(3), 199; https://doi.org/10.3390/coatings9030199 - 19 Mar 2019

Cited by 2 | Viewed by 4379

Abstract

A comparative study of the corrosive resistance and dross formation of 55Al–Zn–1.6Si (wt %) (55AZS) and 23Al–Zn–0.3Si–xMg (wt %) (23AZS–xMg, x = 0, 1.5, 3) alloys are performed using immersion corrosion and dross formation test, respectively. The result of [...] Read more.

A comparative study of the corrosive resistance and dross formation of 55Al–Zn–1.6Si (wt %) (55AZS) and 23Al–Zn–0.3Si–xMg (wt %) (23AZS–xMg, x = 0, 1.5, 3) alloys are performed using immersion corrosion and dross formation test, respectively. The result of immersion corrosion testing shows that corrosive rate of the 23AZS alloy is lower than that of 55AZS alloy in the latter stage of immersion and 23AZS–1.5Mg alloy shows the optimal corrosive resistance compared to other alloys relatively. The result of dross formation test shows that the number of bottom dross particle formed in 23AZS–xMg (x = 0, 1.5, 3) alloy is less than that in 55AZS alloy. Moreover, the thermodynamic calculation is performed to reveal the solubility of Fe in the alloys, the result shows the solubility of Fe reduces as a decrease of Al content in the alloy, and the number of dross particle (Fe₄Al₁₃ and τ₆ (Al₉Fe₂Si₂) phase) generated in 23AZS alloy is more than that in 55AZS alloy. In general, 23AZS–1.5Mg alloy has an advantage of less dross and a certain corrosion resistance and it is expected to be applied for the hot stamping process of coating. Full article

(This article belongs to the Special Issue Advanced Coatings for Corrosion Protection in Extreme Environments)

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10 pages, 3139 KiB

Open AccessArticle

Silver-Nanoparticle-Decorated Gold Nanorod Arrays via Bioinspired Polydopamine Coating as Surface-Enhanced Raman Spectroscopy (SERS) Platforms

by Mehmet Yilmaz

Coatings 2019, 9(3), 198; https://doi.org/10.3390/coatings9030198 - 19 Mar 2019

Cited by 15 | Viewed by 4785

Abstract

The controlled deposition of nanoparticles onto 3-D nanostructured films is still facing challenges due to the uncontrolled aggregation of colloidal nanoparticles. In the context of this study, a simple yet effective approach is demonstrated to decorate the silver nanoparticles (AgNP) onto the 3-D [...] Read more.

The controlled deposition of nanoparticles onto 3-D nanostructured films is still facing challenges due to the uncontrolled aggregation of colloidal nanoparticles. In the context of this study, a simple yet effective approach is demonstrated to decorate the silver nanoparticles (AgNP) onto the 3-D and anisotropic gold nanorod arrays (GNAs) through a bioinspired polydopamine (PDOP) coating to fabricate surface-enhanced Raman spectroscopy (SERS) platforms. Since the Raman reporter molecules (methylene blue, MB, 10 µM) were not adsorbed directly on the surface of the plasmonic material, a remarkable decrease in SERS signals was detected for the PDOP-coated GNAs (GNA@PDOP) platforms. However, after uniform and well-controlled AgNP decoration on the GNA@PDOP (GNA@PDOP@AgNP), huge enhancement was observed in SERS signals from the resultant platform due to the synergistic action which originated from the interaction of GNAs and AgNPs. I also detected that PDOP deposition time (i.e., PDOP film thickness) is the dominant parameter that determines the SERS activity of the final system and 30 min of PDOP deposition time (i.e., 3 nm of PDOP thickness) is the optimum value to obtain the highest SERS signal. To test the reproducibility of GNA@PDOP@AgNP platforms, relative standard deviation (RSD) values for the characteristic peaks of MB were found to be less than 0.17, demonstrating the acceptable reproducibility all over the proposed platform. This report suggests that GNA@PDOP@AgNP system may be used as a robust platform for practical SERS applications. Full article

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17 pages, 6950 KiB

Open AccessArticle

Investigation on Corrosion Resistance and Formation Mechanism of a P–F–Zr Contained Micro-Arc Oxidation Coating on AZ31B Magnesium Alloy Using an Orthogonal Method

by Yuanyuan Zhu, Wenhui Chang, Shufang Zhang, Yingwei Song, Huade Huang, Rongfang Zhao, Guoqiang Li, Rongfa Zhang and Yijia Zhang

Coatings 2019, 9(3), 197; https://doi.org/10.3390/coatings9030197 - 19 Mar 2019

Cited by 13 | Viewed by 2990

Abstract

In this study, the synergistic effects of NH₄HF₂, sodium phytate (Na₁₂Phy), K₂ZrF₆, and treatment time on corrosion resistance of a micro-arc oxidation (MAO) treated magnesium alloy and the entrance mechanism of P, F, [...] Read more.

In this study, the synergistic effects of NH₄HF₂, sodium phytate (Na₁₂Phy), K₂ZrF₆, and treatment time on corrosion resistance of a micro-arc oxidation (MAO) treated magnesium alloy and the entrance mechanism of P, F, and Zr into anodic coatings were investigated using an orthogonal method. In addition, the roles of NH₄HF₂, Na₁₂Phy, and K₂ZrF₆ on coating development were separately studied. The results show that NH₄HF₂ and Na₁₂Phy, the corrosion inhibitors of magnesium alloys, are beneficial but K₂ZrF₆ is harmful to developing anodic coatings. The corrosion resistance of MAO coatings is synergistically determined by coating characteristics, though the coating thickness plays a main role. Na₁₂Phy significantly improves but NH₄HF₂ decreases the corrosion resistance of MAO coatings, while excess high K₂ZrF₆ is harmful to the coating corrosion resistance. Treatment time can increase the coating thickness but is the least important factor in corrosion resistance. During MAO, NH₄HF₂, Na₁₂Phy, and K₂ZrF₆ take part in coating formation, causing P, F, and Zr to compete with each other to enter into anodic coatings. Full article

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10 pages, 1065 KiB

Open AccessArticle

Correlation Between Stoichiometry of Nb_xN_y Coatings Produced by DC Magnetron Sputtering with Electrical Conductivity and the Hall Coefficient

by Angélica Garzon-Fontecha, Harvi A. Castillo, Daniel Escobar-Rincón, Elisabeth Restrepo-Parra and Wencel de la Cruz

Coatings 2019, 9(3), 196; https://doi.org/10.3390/coatings9030196 - 18 Mar 2019

Cited by 4 | Viewed by 3176

Abstract

Non-stoichiometric Nb_xN_y coatings, produced in a reactive sputtering process, were analyzed on the basis of their chemical composition (specifically, nitrogen concentration) and its relationship with electrical conductivity. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS), [...] Read more.

Non-stoichiometric Nb_xN_y coatings, produced in a reactive sputtering process, were analyzed on the basis of their chemical composition (specifically, nitrogen concentration) and its relationship with electrical conductivity. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS), revealing Nb–N bonds. The stoichiometry variation dependence on the N₂ flow was also analyzed, using Auger electron spectroscopy (AES). Without exposing the samples to air, a normal behavior was observed; meaning that the nitrogen concentration in the coatings increased, with an increase in N₂ flow. The electrical properties were evaluated and their relationship with nitrogen content in the films was analyzed. The highest conductivity value for all studied samples was observed for the sub-stoichiometric film, NbN_0.32, which also exhibited a positive Hall coefficient. It indicated that the conduction was mainly dominated by hole-type carriers. High conductivity at lower nitrogen content was attributed to the fact that, at a low concentration of nitrogen, the effect of impurities, acting as dispersion points for electrons, was lower, increasing the relaxation time. As the main conclusion, the Ar/N₂ flow ratio strongly influenced the coatings of stoichiometry and then, this stoichiometry affected, to a great extent, the electrical conduction and the Hall coefficient of the coatings. Full article

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16 pages, 7097 KiB

Open AccessFeature PaperArticle

Pulsed Laser Deposition of Aluminum Nitride Films: Correlation between Mechanical, Optical, and Structural Properties

by Lilyana Kolaklieva, Vasiliy Chitanov, Anna Szekeres, Krassimira Antonova, Penka Terziyska, Zsolt Fogarassy, Peter Petrik, Ion N. Mihailescu and Liviu Duta

Coatings 2019, 9(3), 195; https://doi.org/10.3390/coatings9030195 - 17 Mar 2019

Cited by 15 | Viewed by 4214

Abstract

Aluminum nitride (AlN) films were synthesized onto Si(100) substrates by pulsed laser deposition (PLD) in vacuum or nitrogen, at 0.1, 1, 5, or 10 Pa, and substrate temperatures ranging from RT to 800 °C. The laser parameters were set at: incident laser fluence [...] Read more.

Aluminum nitride (AlN) films were synthesized onto Si(100) substrates by pulsed laser deposition (PLD) in vacuum or nitrogen, at 0.1, 1, 5, or 10 Pa, and substrate temperatures ranging from RT to 800 °C. The laser parameters were set at: incident laser fluence of 3–10 J/cm² and laser pulse repetition frequency of 3, 10, or 40 Hz, respectively. The films’ hardness was investigated by depth-sensing nanoindentation. The optical properties were studied by FTIR spectroscopy and UV-near IR ellipsometry. Hardness values within the range of 22–30 GPa and Young’s modulus values of 230–280 GPa have been inferred. These values were determined by the AlN film structure that consisted of nanocrystallite grains, strongly dependent on the deposition parameters. The values of optical constants, superior to amorphous AlN, support the presence of crystallites in the amorphous film matrix. They were visualized by TEM and evidenced by FTIR spectroscopy. The characteristic Reststrahlen band of the h-AlN lattice with component lines arising from IR active phonon vibrational modes in AlN nanocrystallites was well detectable within the spectral range of 950–500 cm⁻¹. Control X-ray diffraction and atomic force microscopy data were introduced and discussed. All measurements delivered congruent results and have clearly shown a correlation between the films’ structure and the mechanical and optical properties dependent on the experimental conditions. Full article

(This article belongs to the Special Issue Current Research in Pulsed Laser Deposition)

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21 pages, 1187 KiB

Open AccessReview

Chitosan Coating Applications in Probiotic Microencapsulation

by Lavinia-Florina Călinoiu, Bianca Eugenia Ştefănescu, Ioana Delia Pop, Leon Muntean and Dan Cristian Vodnar

Coatings 2019, 9(3), 194; https://doi.org/10.3390/coatings9030194 - 16 Mar 2019

Cited by 121 | Viewed by 12161

Abstract

Nowadays, probiotic bacteria are extensively used as health-related components in novel foods with the aim of added-value for the food industry. Ingested probiotic bacteria must resist gastrointestinal exposure, the food matrix, and storage conditions. The recommended methodology for bacteria protection is microencapsulation technology. [...] Read more.

Nowadays, probiotic bacteria are extensively used as health-related components in novel foods with the aim of added-value for the food industry. Ingested probiotic bacteria must resist gastrointestinal exposure, the food matrix, and storage conditions. The recommended methodology for bacteria protection is microencapsulation technology. A key aspect in the advancement of this technology is the encapsulation system. Chitosan compliments the real potential of coating microencapsulation for applications in the food industry due to its physicochemical properties: positive charges via its amino groups (which makes it the only commercially available water-soluble cationic polymer), short-term biodegradability, non-toxicity and biocompatibility with the human body, and antimicrobial and antifungal actions. Chitosan-coated microcapsules have been reported to have a major positive influence on the survival rates of different probiotic bacteria under in vitro gastrointestinal conditions and in the storage stability of different types of food products; therefore, its utilization opens promising routes in the food industry. Full article

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13 pages, 7965 KiB

Open AccessArticle

Measurement of Equivalent BRDF on the Surface of Solar Panel with Periodic Structure

by Qingyu Hou, Zhile Wang, Jinyu Su and Fanjiao Tan

Coatings 2019, 9(3), 193; https://doi.org/10.3390/coatings9030193 - 16 Mar 2019

Cited by 8 | Viewed by 3472

Abstract

The surface of a complex material with a periodic structure is equivalent to the surface of a uniform material, and the measurement and data processing methods for the equivalent optical BRDF of a solar panel based on a large-scale spot are proposed. Based [...] Read more.

The surface of a complex material with a periodic structure is equivalent to the surface of a uniform material, and the measurement and data processing methods for the equivalent optical BRDF of a solar panel based on a large-scale spot are proposed. Based on a solar simulator, high-intensity light illuminometer, low-intensity light illuminometer and precise rotary platform, the BRDF automatic measurement platform is built. Spot size optimization and a measurement radius optimization method are proposed. The measurement results show that the BRDF of the solar panel has specular reflection characteristics, but that it still differs from the solar cell in the half width of the BRDF curve. Measurement error analysis is performed for the measurement process; its value is 6.74%. The measurement results can be used to improve the understanding of the optical reflection characteristics of the solar panel. Meanwhile, the method can also be used to measure and characterize the coatings of heat insulation material and scattering coating. The measurement data also has practical reference value for evaluations of improvements of the light absorption of the surface functional material. Finally, it can be used to simulate the target image scene. Full article

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15 pages, 4027 KiB

Open AccessArticle

DLC and DLC-WS₂ Coatings for Machining of Aluminium Alloys

by Tomasz L. Brzezinka, Jeff Rao, Jose M. Paiva, Joern Kohlscheen, German S. Fox-Rabinovich, Stephen C. Veldhuis and Jose L. Endrino

Coatings 2019, 9(3), 192; https://doi.org/10.3390/coatings9030192 - 15 Mar 2019

Cited by 18 | Viewed by 4747

Abstract

Machine-tool life is one limiting factor affecting productivity. The requirement for wear-resistant materials for cutting tools to increase their longevity is therefore critical. Titanium diboride (TiB₂) coated cutting tools have been successfully employed for machining of AlSi alloys widely used in [...] Read more.

Machine-tool life is one limiting factor affecting productivity. The requirement for wear-resistant materials for cutting tools to increase their longevity is therefore critical. Titanium diboride (TiB₂) coated cutting tools have been successfully employed for machining of AlSi alloys widely used in the automotive industry. This paper presents a methodological approach to improving the self-lubricating properties within the cutting zone of a tungsten carbide milling insert precoated with TiB₂, thereby increasing the operational life of the tool. A unique hybrid Physical Vapor Deposition (PVD) system was used in this study, allowing diamond-like carbon (DLC) to be deposited by filtered cathodic vacuum arc (FCVA) while PVD magnetron sputtering was employed to deposit WS₂. A series of ~100-nm monolayer DLC coatings were prepared at a negative bias voltage ranging between −50 and −200 V, along with multilayered DLC-WS₂ coatings (total thickness ~500 nm) with varying number of layers (two to 24 in total). The wear rate of the coated milling inserts was investigated by measuring the flank wear during face milling of an Al-10Si. It was ascertained that employing monolayer DLC coating reduced the coated tool wear rate by ~85% compared to a TiB₂ benchmark. Combining DLC with WS₂ as a multilayered coating further improved tool life. The best tribological properties were found for a two-layer DLC-WS₂ coating which decreased wear rate by ~75% compared to TiB₂, with a measured coefficient of friction of 0.05. Full article

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9 pages, 4714 KiB

Open AccessArticle

Electrochromic Properties of Lithium-Doped Tungsten Oxide Prepared by Electron Beam Evaporation

by Jui-Yang Chang, Ying-Chung Chen, Chih-Ming Wang, Wen-Nan Wang, Chih-Yu Wen and Jyun-Min Lin

Coatings 2019, 9(3), 191; https://doi.org/10.3390/coatings9030191 - 14 Mar 2019

Cited by 10 | Viewed by 3494

Abstract

In this study, xLi₂O-(1−x)WO₃ powders were mixed with WO₃ and Li₂O and pressed into target pellets to fabricate electrochromic films on indium tin oxide (ITO) glasses prepared by electron beam evaporation under the parameters [...] Read more.

In this study, xLi₂O-(1−x)WO₃ powders were mixed with WO₃ and Li₂O and pressed into target pellets to fabricate electrochromic films on indium tin oxide (ITO) glasses prepared by electron beam evaporation under the parameters of room temperature, and thicknesses of about 530 nm. It was expected that the amount of charge stored in the electrochromic devices (ECDs) could be enhanced by using the doping method in the cathode materials. The experimental results show that as the composition of Li_0.18W_0.82O_2.6 powder was formed, the optimal characteristics of ECD can be obtained. In which, as a voltage of 3.5 V was applied on ECD, a transmittance change (ΔT%) of 53.1%, an optical density (ΔOD) of 0.502, an intercalation charge (Q) of 12.9 mC/cm² and a coloration efficiency (η) of 41.6 cm²/C at a wavelength of 550 nm can be achieved. These results demonstrate that Li₂O doping in WO₃ films could effectively improve the coloration and electrochromic properties of ECD devices. Full article

(This article belongs to the Special Issue Electrochromic Thin Films and Devices)

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9 pages, 3523 KiB

Open AccessCommunication

Adhesive Hybrid SiO_2.01C_0.23H_x Nanoparticulate Coating on Polyethylene (PE) Separator by Roll-to-Roll Atmospheric Pressure Plasma

by Yichao Jin, Chaoliang Wang, Nana Yuan, Ke Ding, Yu Xu, Sicheng Qin, Ming Wang, Zhuangchun Wu, Chengran Du, Jianjun Shi and Jing Zhang

Coatings 2019, 9(3), 190; https://doi.org/10.3390/coatings9030190 - 14 Mar 2019

Cited by 6 | Viewed by 3769

Abstract

For the ever-increasing demand for highly safe lithium-ion batteries (LIBs), the common sol-gel process provides heat-resistance to separators with an inorganic coating, where the adhesion to the separator is the key to safety and stability. In this paper, we present a SiO_2.01 [...] Read more.

For the ever-increasing demand for highly safe lithium-ion batteries (LIBs), the common sol-gel process provides heat-resistance to separators with an inorganic coating, where the adhesion to the separator is the key to safety and stability. In this paper, we present a SiO_2.01C_0.23H_x-coated polyethylene (PE) separator through a roll-to-roll atmospheric plasma-enhanced chemical vapor deposition (R2R-APECVD) of hexamethyldisiloxane (HMDSO)/Ar/O₂. The adhesion strength of SiO_2.01C_0.23H_x-coated PE was tested by peel-off test and found to be higher than that of the commercial Al₂O₃-coated separator (0.28 N/mm vs. 0.06 N/mm). Furthermore, the SiO_2.01C_0.23H_x-coated PE separator showed better electrochemical performance in C-rate and long term cycle tests. FTIR, SEM, and XPS analysis indicate that the increased adhesion and electrochemical performance are attributed to the inner hybrid SiO_2.01C_0.23H_x coating with organic and inorganic components. Full article

(This article belongs to the Special Issue Surface Plasma Treatments)

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12 pages, 3721 KiB

Open AccessArticle

Electrodeposition of Nanocrystalline Fe-P Coatings: Influence of Bath Temperature and Glycine Concentration on Structure, Mechanical and Corrosion Behavior

by Natalia Kovalska, Natalia Tsyntsaru, Henrikas Cesiulis, Annet Gebert, Jordina Fornell, Eva Pellicer, Jordi Sort, Wolfgang Hansal and Wolfgang Kautek

Coatings 2019, 9(3), 189; https://doi.org/10.3390/coatings9030189 - 13 Mar 2019

Cited by 8 | Viewed by 4254

Abstract

A detailed electrochemical study and investigation of a Fe-P glycine bath as a function of the temperature and glycine concentrations and current density, and their resulting corrosion and mechanical behavior is presented. A low addition of glycine to the electrolyte led to a [...] Read more.

A detailed electrochemical study and investigation of a Fe-P glycine bath as a function of the temperature and glycine concentrations and current density, and their resulting corrosion and mechanical behavior is presented. A low addition of glycine to the electrolyte led to a drastic increase of the P content. At low Fe-P deposition rates, heterogeneous rough deposits with morphological bumps and pores were observed. By increasing the Fe-P deposition rate, the number of pores were reduced drastically, resulting in smooth coatings. Increasing the P content led to the formation of nanocrystalline grains from an “amorphous-like” state. Coatings with higher P contents exhibited better corrosion resistance and hardening, most likely attributed to grain boundary strengthening. Full article

(This article belongs to the Special Issue Sustainable Coatings by Electrodeposition: Synthesis, Characterization, and Applications)

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13 pages, 7605 KiB

Open AccessArticle

A Comparative Study of YSZ Suspensions and Coatings

by Fariba Tarasi, Elnaz Alebrahim, Ali Dolatabadi and Christian Moreau

Coatings 2019, 9(3), 188; https://doi.org/10.3390/coatings9030188 - 13 Mar 2019

Cited by 12 | Viewed by 3419

Abstract

The demand for suspensions that are used in thermal spray processes is expanding from research labs using the lab-prepared suspensions toward actual coating production in different industrial sectors. Industrial applications dictate the reduced production time and effort, which may in turn justify the [...] Read more.

The demand for suspensions that are used in thermal spray processes is expanding from research labs using the lab-prepared suspensions toward actual coating production in different industrial sectors. Industrial applications dictate the reduced production time and effort, which may in turn justify the development of the market for ready-to-use commercial suspensions. To this end, some of the powder suppliers have already taken steps forward by introducing, to the market, suspensions of some of the most used materials, such as yttria-stabilized zirconia (YSZ), alumina, and titania. However, there is a need to compare the suspension characteristics over time and the resultant coatings when using these suspensions when compared with the freshly prepared homemade suspensions. In this work, such a comparison is done using YSZ suspensions of the sub-micron to a few micron powders. In addition, some changes in the suspensions’ formula were performed as a tool to vary the coatings’ microstructures in a more predictable way, without any variation of the spray parameters. The coatings were generated while using both radial and axial injection of the suspensions into Oerlikon-Metco 3MB and Mettech Axial III plasma spray torches, respectively. A clear effect of suspension viscosity on the coating microstructure was observed using the 3MB torch with a radial injection of suspension (i.e., cross flow atomization). However, the viscosity role was not dominant when using the Axial III torch with an axial feed injection system (i.e., coaxial flow atomization). Full article

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20 pages, 8740 KiB

Open AccessArticle

Aluminum Coated Micro Glass Spheres to Increase the Infrared Reflectance

by Laura Schwinger, Sebastian Lehmann, Lukas Zielbauer, Benedikt Scharfe and Thorsten Gerdes

Coatings 2019, 9(3), 187; https://doi.org/10.3390/coatings9030187 - 12 Mar 2019

Cited by 7 | Viewed by 5775

Abstract

The reflective properties of micro glass spheres (MGS) such as Solid Micro Glass Spheres (SMGS, “glass beads”) and Micro Hollow Glass Spheres (MHGS, “glass bubbles”) are utilized in various applications, for example, as retro-reflector for traffic road stripe paints or facade paints. The [...] Read more.

The reflective properties of micro glass spheres (MGS) such as Solid Micro Glass Spheres (SMGS, “glass beads”) and Micro Hollow Glass Spheres (MHGS, “glass bubbles”) are utilized in various applications, for example, as retro-reflector for traffic road stripe paints or facade paints. The reflection behavior of the spheres can be further adapted by coating the surfaces of the spheres, e.g., by titanium dioxide or a metallic coating. Such coated spheres can be employed as, e.g., mid infrared (MIR)-reflective additives in wall paints to increase the thermal comfort in rooms. As a result, the demand of heating energy can be reduced. In this paper, the increase of the MIR-reflectance by applying an aluminum coating on MGS is discussed. Aluminum coatings are normally produced via the well-known Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD). In our work, the Liquid Phase Deposition (LPD) method, as a new, non-vacuum method for aluminum coating on spherical spheres, is investigated as an alternative, scalable, and simple coating process. The LPD-coating is characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and reflection measurements. The results are compared to a reference PVD-coating. It is shown that both sphere types, SMGS and MHGS, can be homogeneously coated with metallic aluminum using the LPD method but the surface morphology plays an important role concerning the reflection properties. With the SMGS, a smooth surface morphology and a reflectance increase to a value of 30% can be obtained. Due to a structured surface morphology, a reflection of only 5% could be achieved with the MHGS. However, post-treatments showed that a further increase is possible. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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20 pages, 6182 KiB

Open AccessFeature PaperArticle

Fibre Laser Treatment of Beta TNZT Titanium Alloys for Load-Bearing Implant Applications: Effects of Surface Physical and Chemical Features on Mesenchymal Stem Cell Response and Staphylococcus aureus Bacterial Attachment

by Clare Lubov Donaghy, Ryan McFadden, Graham C. Smith, Sophia Kelaini, Louise Carson, Savko Malinov, Andriana Margariti and Chi-Wai Chan

Coatings 2019, 9(3), 186; https://doi.org/10.3390/coatings9030186 - 12 Mar 2019

Cited by 14 | Viewed by 4725

Abstract

A mismatch in bone and implant elastic modulus can lead to aseptic loosening and ultimately implant failure. Selective elemental composition of titanium (Ti) alloys coupled with surface treatment can be used to improve osseointegration and reduce bacterial adhesion. The biocompatibility and antibacterial properties [...] Read more.

A mismatch in bone and implant elastic modulus can lead to aseptic loosening and ultimately implant failure. Selective elemental composition of titanium (Ti) alloys coupled with surface treatment can be used to improve osseointegration and reduce bacterial adhesion. The biocompatibility and antibacterial properties of Ti-35Nb-7Zr-6Ta (TNZT) using fibre laser surface treatment were assessed in this work, due to its excellent material properties (low Young’s modulus and non-toxicity) and the promising attributes of fibre laser treatment (very fast, non-contact, clean and only causes changes in surface without altering the bulk composition/microstructure). The TNZT surfaces in this study were treated in a high speed regime, specifically 100 and 200 mm/s, (or 6 and 12 m/min). Surface roughness and topography (WLI and SEM), chemical composition (SEM-EDX), microstructure (XRD) and chemistry (XPS) were investigated. The biocompatibility of the laser treated surfaces was evaluated using mesenchymal stem cells (MSCs) cultured in vitro at various time points to assess cell attachment (6, 24 and 48 h), proliferation (3, 7 and 14 days) and differentiation (7, 14 and 21 days). Antibacterial performance was also evaluated using Staphylococcus aureus (S. aureus) and Live/Dead staining. Sample groups included untreated base metal (BM), laser treated at 100 mm/s (LT100) and 200 mm/s (LT200). The results demonstrated that laser surface treatment creates a rougher (Ra value of BM is 199 nm, LT100 is 256 nm and LT200 is 232 nm), spiky surface (Rsk > 0 and Rku > 3) with homogenous elemental distribution and decreasing peak-to-peak distance between ripples (0.63 to 0.315 µm) as the scanning speed increases (p < 0.05), generating a surface with distinct micron and nano scale features. The improvement in cell spreading, formation of bone-like nodules (only seen on the laser treated samples) and subsequent four-fold reduction in bacterial attachment (p < 0.001) can be attributed to the features created through fibre laser treatment, making it an excellent choice for load bearing implant applications. Last but not least, the presence of TiN in the outermost surface oxide might also account for the improved biocompatibility and antibacterial performances of TNZT. Full article

(This article belongs to the Special Issue Laser Surface Engineering)

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15 pages, 2736 KiB

Open AccessArticle

Self-Ordered Orientation of Crystalline Hexagonal Boron Nitride Nanodomains Embedded in Boron Carbonitride Films for Band Gap Engineering

by Yujing Li, Wei Gao, Fei Wang, Dehe Zhao, Yuyuan Zhang and Hong Yin

Coatings 2019, 9(3), 185; https://doi.org/10.3390/coatings9030185 - 12 Mar 2019

Cited by 10 | Viewed by 4499

Abstract

Boron carbonitride (BCN) films containing hybridized bonds involving elements B, C, and N over wide compositional ranges enable an abundant variety of new materials, electronic structures, properties, and applications, owing to their semiconducting properties with variable band gaps. However, it still remains challenging [...] Read more.

Boron carbonitride (BCN) films containing hybridized bonds involving elements B, C, and N over wide compositional ranges enable an abundant variety of new materials, electronic structures, properties, and applications, owing to their semiconducting properties with variable band gaps. However, it still remains challenging to achieve band gap-engineered BCN ternary with a controllable composition and well-established ordered structure. Herein, we report on the synthesis and characterization of hybridized BCN materials, consisting of self-ordered hexagonal BN (h-BN) crystalline nanodomains, with its aligned basal planes preferentially perpendicular to the substrate, depending on the growth conditions. The observation of the two sets of different band absorptions suggests that the h-BN nanodomains are distinguished enough to resume their individual band gap identity from the BCN films, which decreases as the carbon content increases in the BCN matrix, due to the doping and/or boundary effect. Our results reveal that the structural features and band gap of this form of hybrid BCN films are strongly correlated with the kinetic growth factors, making it a great system for further fundamental physical research and for potential in the development of band gap-engineered applications in optoelectronics. Full article

(This article belongs to the Special Issue Advanced Thin Films Deposited by Magnetron Sputtering)

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17 pages, 18433 KiB

Open AccessArticle

Theoretical Study of Sulphur Atoms’ Adsorption and Migration Behaviors on Diamond (001) Surface

by Xuejie Liu, Haifeng Sun, Yanzhao Wu, Shiyang Sun, Yuan Ren, Xin Tan and Huiling Jia

Coatings 2019, 9(3), 184; https://doi.org/10.3390/coatings9030184 - 12 Mar 2019

Cited by 2 | Viewed by 3055

Abstract

The adsorption and migration of sulphur (S) atoms on the diamond (001) surface were investigated through first principles calculations to discover the inherent law in S-doped diamond film growth. Results indicated that deposited S atoms could abstract the hydrogen atom on the surface. [...] Read more.

The adsorption and migration of sulphur (S) atoms on the diamond (001) surface were investigated through first principles calculations to discover the inherent law in S-doped diamond film growth. Results indicated that deposited S atoms could abstract the hydrogen atom on the surface. The adsorption energies were in a range of 2.47 to 5.5 eV when S atoms were deposited on the hydrogen terminated surface or the surface with open radical sites (ORSs). The S atom could migrate on the surface of the 3ORS slabs and the energy barrier was approximately 1.35 eV. The calculations of the projected density of states and the analysis of the magnetic moments presented an interesting result, which demonstrated the evolving phenomena in S-doped diamond film growth and discovered the inherent laws. On the 2ORS slabs, the magnetic moment of the S atom became 0.000 μ_B after bonding with the two carbon atoms. In such case, a new doped C atom combined with the S atom with a triple bond, and then the C–S molecule was desorbed from the surface. The abstraction of the adsorbed S atom results from the fact that S atoms have six electrons in their outermost electron shell. This finding revealed the reason behind the low S incorporation and the growth rate decrease in S-doped diamond film deposition. This discovery also indicated that atoms with six electrons in their outermost electron shell might hardly be doped into the diamond films during the deposition process. Full article

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