Coatings

13 pages, 3346 KiB

Open AccessArticle

Increasing the Efficiency of Dye-Sensitized Solar Cells by Adding Nickel Oxide Nanoparticles to Titanium Dioxide Working Electrodes

by Chih-Hung Tsai, Chia-Ming Lin and Yen-Cheng Liu

Coatings 2020, 10(2), 195; https://doi.org/10.3390/coatings10020195 - 24 Feb 2020

Cited by 17 | Viewed by 5060

Abstract

In this study, nickel oxide (NiO) nanoparticles were added to a titanium dioxide (TiO₂) nanoparticle paste to fabricate a dye-sensitized solar cell (DSSC) working electrode by using a screen-printing method. The effects of the NiO proportion in the TiO₂ paste [...] Read more.

In this study, nickel oxide (NiO) nanoparticles were added to a titanium dioxide (TiO₂) nanoparticle paste to fabricate a dye-sensitized solar cell (DSSC) working electrode by using a screen-printing method. The effects of the NiO proportion in the TiO₂ paste on the TiO₂ working electrode, DSSC devices, and electron transport characteristics were comprehensively investigated. The results showed that adding NiO nanoparticles to the TiO₂ working electrode both inhibited electron transport (a negative effect) and prevented electron recombination with the electrolyte (a positive effect). The electron transit time was extended following an increase in the amount of NiO nanoparticles added, confirming that NiO inhibited electron transport. Furthermore, the energy level difference between TiO₂ and NiO generated a potential barrier that prevented the recombination of the electrons in the TiO₂ conduction band with the I₃^- ions in the electrolyte. When the TiO₂–NiO ratio was 99:1, the positive effects outweighed the negative effects. Therefore, this ratio was the optimal TiO₂–NiO ratio in the electrode for electron transport. The DSSCs with a TiO₂–NiO (99:1) working electrode exhibited an optimal power conversion efficiency of 8.39%, which was higher than the DSSCs with a TiO₂ working electrode. Full article

(This article belongs to the Special Issue Mesoporous Metal Oxide Films)

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11 pages, 3630 KiB

Open AccessArticle

Forward Current Transport Properties of AlGaN/GaN Schottky Diodes Prepared by Atomic Layer Deposition

by Hogyoung Kim, Seok Choi and Byung Joon Choi

Coatings 2020, 10(2), 194; https://doi.org/10.3390/coatings10020194 - 24 Feb 2020

Cited by 11 | Viewed by 3963

Abstract

Atomic layer deposited AlGaN on GaN substrate with different thicknesses was prepared and the electron transport mechanism of AlGaN/GaN Schottky diodes was investigated. Above 348 K, both 5 and 10 nm thick AlGaN showed that the thermionic emission model with inhomogeneous Schottky barrier [...] Read more.

Atomic layer deposited AlGaN on GaN substrate with different thicknesses was prepared and the electron transport mechanism of AlGaN/GaN Schottky diodes was investigated. Above 348 K, both 5 and 10 nm thick AlGaN showed that the thermionic emission model with inhomogeneous Schottky barrier could explain the forward current transport. Analysis using a dislocation-related tunneling model showed that the current values for 10 nm thick AlGaN was matched well to the experimental data while those were not matched for 5 nm thick AlGaN. The higher density of surface (and interface) states was found for 5 nm thick AlGaN. In other words, a higher density of surface donors, as well as a thinner AlGaN layer for 5 nm thick AlGaN, enhanced the tunneling current. Full article

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34 pages, 11659 KiB

Open AccessFeature PaperReview

Percolation Model for Renewable-Carbon Doped Functional Composites in Packaging Application: A Brief Review

by Bo Sun, Fangong Kong, Min Zhang, Weijun Wang, Birat Singh KC, Jimi Tjong and Mohini Sain

Coatings 2020, 10(2), 193; https://doi.org/10.3390/coatings10020193 - 24 Feb 2020

Cited by 8 | Viewed by 5286

Abstract

This review summarizes the application of percolation theory for the behavior simulation of renewable-carbon in its doped packaging composites. Such dopant-reinforced materials have sparked considerable interest due to the significant improvement on the aesthetic and mechanical properties at considerable low filler content (<1% [...] Read more.

This review summarizes the application of percolation theory for the behavior simulation of renewable-carbon in its doped packaging composites. Such dopant-reinforced materials have sparked considerable interest due to the significant improvement on the aesthetic and mechanical properties at considerable low filler content (<1% in some cases), which would further boost their potential use in the food and pharmaceutical packaging industries. We focused mainly on the percolation behavior, which is closely related to the distribution of renewable carbon particles in the presence of polymeric matrix. The effect of geometry, alignment and surface property is of particular relevance to the percolation threshold of composites containing carbon fillers. Validity, as well as limitations of the mostly used percolation models, is further discussed. Finally, despite its recent emergence as functional filler, carbon-based nanocellulose has been extensively developed for a wide range of applications. This inspired the concept to use nanocellulose as a secondary bio-additive for packaging purposes, such as functional nanocellulose-coated film where primarily synthetic polymers are used. The microstructure and functionality of rod-like nanocellulose in its use for film composite are specifically discussed. Full article

(This article belongs to the Special Issue Bio-Based Active Packaging for Shelf Life Extension)

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14 pages, 4487 KiB

Open AccessArticle

Effect of the Compactness on the Texture and Friction of Asphalt Concrete Intended for Wearing Course of the Road Pavement

by Tengda Wang, Liqun Hu, Xiaodong Pan, Song Xu and Di Yun

Coatings 2020, 10(2), 192; https://doi.org/10.3390/coatings10020192 - 24 Feb 2020

Cited by 10 | Viewed by 3796

Abstract

Maintaining good friction performance of highway pavement is important for road safety. The friction is affected by many factors, and the present study investigates the effect of the compactness on the texture and friction of asphalt concrete during the polishing process. Two three-dimensional [...] Read more.

Maintaining good friction performance of highway pavement is important for road safety. The friction is affected by many factors, and the present study investigates the effect of the compactness on the texture and friction of asphalt concrete during the polishing process. Two three-dimensional (3D) texture parameters and the mean texture depth (MTD) were used to characterize the surface texture of AC-13 asphalt concrete. The differences of surface texture are then being analyzed among the pavement in the field, rutting slabs with 97% compactness (RS-97), rutting slabs with 100% compactness (RS-100), and rutting slabs with 103% (RS-103). The rutting slabs were polished by a circular vehicle simulator (CVS). The 3D surface topography, British pendulum number (BPN), and MTD were obtained during the polishing process. Test results show that the surface of the rutting slab can be smoother as the compactness increased from 97% to 103%. During the whole polishing process, the rutting slab with smaller compactness had higher value of the MTD. The impact of compactness on the BPN is insignificant during the polishing process, but rutting slabs with smaller compactness had better friction at high speed as the result of the higher MTD. Full article

(This article belongs to the Collection Pavement Surface Coatings)

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11 pages, 2221 KiB

Open AccessArticle

Development of Apatite Nuclei Precipitated Carbon Nanotube-Polyether Ether Ketone Composite with Biological and Electrical Properties

by Chihiro Ishizaki, Takeshi Yabutsuka and Shigeomi Takai

Coatings 2020, 10(2), 191; https://doi.org/10.3390/coatings10020191 - 24 Feb 2020

Cited by 7 | Viewed by 4754

Abstract

We aimed to impart apatite-forming ability to carbon nanotube (CNT)-polyether ether ketone (PEEK) composite (CNT-PEEK). Since CNT possesses electrical conductivity, CNT-PEEK can be expected to useful not only for implant materials but also biosensing devices. First of all, in this study, CNT-PEEK was [...] Read more.

We aimed to impart apatite-forming ability to carbon nanotube (CNT)-polyether ether ketone (PEEK) composite (CNT-PEEK). Since CNT possesses electrical conductivity, CNT-PEEK can be expected to useful not only for implant materials but also biosensing devices. First of all, in this study, CNT-PEEK was treated with sulfuric acid to form fine pores on its surface. Then, the hydrophilicity of the substrate was improved by oxygen plasma treatment. After that, the substrate was promptly immersed in simulated body fluid (SBF) which was adjusted at pH 8.40, 25.0 °C (alkaline SBF) and held in an incubator set at 70.0 °C for 1 day to deposit fine particles of amorphous calcium phosphate, which we refer to as ‘apatite nuclei’. When thus-treated CNT-PEEK was immersed in SBF, its surface was spontaneously covered with hydroxyapatite within 1 day by apatite nuclei deposited in the fine pores and high apatite-forming ability was successfully demonstrated. The CNT-PEEK also showed conductivity even after the above treatment and showed smaller impedance than that of the untreated CNT-PEEK substrate. Full article

(This article belongs to the Special Issue Synthetic and Biological-Derived Hydroxyapatite Implant Coatings)

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28 pages, 8045 KiB

Open AccessFeature PaperArticle

Production of High Silicon-Doped Hydroxyapatite Thin Film Coatings via Magnetron Sputtering: Deposition, Characterisation, and In Vitro Biocompatibility

by Samuel C. Coe, Matthew D. Wadge, Reda M. Felfel, Ifty Ahmed, Gavin S. Walker, Colin A. Scotchford and David M. Grant

Coatings 2020, 10(2), 190; https://doi.org/10.3390/coatings10020190 - 23 Feb 2020

Cited by 17 | Viewed by 6426

Abstract

In recent years, it has been found that small weight percent additions of silicon to HA can be used to enhance the initial response between bone tissue and HA. A large amount of research has been concerned with bulk materials, however, only recently [...] Read more.

In recent years, it has been found that small weight percent additions of silicon to HA can be used to enhance the initial response between bone tissue and HA. A large amount of research has been concerned with bulk materials, however, only recently has the attention moved to the use of these doped materials as coatings. This paper focusses on the development of a co-RF and pulsed DC magnetron sputtering methodology to produce a high percentage Si containing HA (SiHA) thin films (from 1.8 to 13.4 wt.%; one of the highest recorded in the literature to date). As deposited thin films were found to be amorphous, but crystallised at different annealing temperatures employed, dependent on silicon content, which also lowered surface energy profiles destabilising the films. X-ray photoelectron spectroscopy (XPS) was used to explore the structure of silicon within the films which were found to be in a polymeric (SiO₂; Q⁴) state. However, after annealing, the films transformed to a SiO₄⁴⁻, Q⁰, state, indicating that silicon had substituted into the HA lattice at higher concentrations than previously reported. A loss of hydroxyl groups and the maintenance of a single-phase HA crystal structure further provided evidence for silicon substitution. Furthermore, a human osteoblast cell (HOB) model was used to explore the in vitro cellular response. The cells appeared to prefer the HA surfaces compared to SiHA surfaces, which was thought to be due to the higher solubility of SiHA surfaces inhibiting protein mediated cell attachment. The extent of this effect was found to be dependent on film crystallinity and silicon content. Full article

(This article belongs to the Special Issue Physical Vapor Deposited Biomedical Coatings)

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15 pages, 4383 KiB

Open AccessFeature PaperArticle

Graphene Oxide Reinforcing Genipin Crosslinked Chitosan-Gelatin Blend Films

by George Mihail Vlasceanu, Livia Elena Crica, Andreea Madalina Pandele and Mariana Ionita

Coatings 2020, 10(2), 189; https://doi.org/10.3390/coatings10020189 - 23 Feb 2020

Cited by 32 | Viewed by 5293

Abstract

This study was targeted towards the synthesis and characterization of new chitosan–gelatin biocomposite films reinforced with graphene oxide and crosslinked with genipin. The composites’ mode of structuration was characterized by Fourier Transform Infrared spectroscopy and X-ray diffraction, while morphology and topography were investigated [...] Read more.

This study was targeted towards the synthesis and characterization of new chitosan–gelatin biocomposite films reinforced with graphene oxide and crosslinked with genipin. The composites’ mode of structuration was characterized by Fourier Transform Infrared spectroscopy and X-ray diffraction, while morphology and topography were investigated by scanning electron microscopy, nano-computer tomography and profilometry. Eventually, thermal stability was evaluated through thermogravimetrical analysis, mechanical properties assessment was carried out to detect potential improvements as a result of graphene oxide (GO) addition and in vitro enzyme degradation was performed to discern the most promising formulations for the maturation of the study towards in vivo assays. In accordance with similar works, results indicated the possibility of using GO as an agent for adjusting films’ roughness, chemical stability and polymer structuration. The enzymatic stability of chitosan–gelatin (CHT-GEL) films was also improved by genipin (GEN) crosslinking and GO supplementation, with the best results being obtained for CHT-GEL-GEN and CHT-GEL-GEN-GO3 (crosslinked formulation with 3 wt.% GO). Yet, contrary to previous reports, no great enhancement of CHT-GEN-GEL-GO thermal performances was obtained by the incorporation of GO. Full article

(This article belongs to the Special Issue Advances in Graphene Based Composite for Bio-Applications)

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11 pages, 2689 KiB

Open AccessFeature PaperArticle

Acrylic Pressure-Sensitive Adhesive Reinforced with Aluminum Nitride and Its Thermal Properties: Effect of Surface Treatment and Particle Size

by Garima Mittal, Soo Jin Park and Kyong Yop Rhee

Coatings 2020, 10(2), 188; https://doi.org/10.3390/coatings10020188 - 22 Feb 2020

Cited by 7 | Viewed by 5449

Abstract

Thermal interface materials (TIMs) are very crucial for better heat-transfer in electronics working as an interfacial connection between heat generators and heat sinks. This study is focused on the pressure-sensitive acrylic adhesive tape reinforced with micron-sized and nano-sized aluminum nitride (AlN) particles where [...] Read more.

Thermal interface materials (TIMs) are very crucial for better heat-transfer in electronics working as an interfacial connection between heat generators and heat sinks. This study is focused on the pressure-sensitive acrylic adhesive tape reinforced with micron-sized and nano-sized aluminum nitride (AlN) particles where the surface modification of AlN particles is done using (3-Aminopropyl) triethoxysilane (3-APTES). The physicochemical analysis of the silanized AlN particles is done using FTIR spectroscopy and scanning electron microscopy (SEM). Furthermore, thermal properties along with thermal conductivity and thermal diffusion are also studied. The main outcome of this study shows that the sample containing surface-treated AlN particles exhibits better thermal conductivity than that of the samples containing µ and nano-sized of AlN due to the comparatively better interactions with the matrix. Full article

(This article belongs to the Special Issue Advances in Nanoscale Coatings for Composites)

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14 pages, 6908 KiB

Open AccessArticle

Synchronous Shot Peening Applied on HVOF for Improvement on Wear Resistance of Fe-based Amorphous Coating

by Zhidan Zhou, Junchao Shang, Yongxiong Chen, Xiubing Liang, Baolong Shen and Zhibin Zhang

Coatings 2020, 10(2), 187; https://doi.org/10.3390/coatings10020187 - 20 Feb 2020

Cited by 9 | Viewed by 3386

Abstract

Shot peening was used synchronously to improve Fe-based amorphous coating performance by delivering ZrO₂ ceramic particles into a low-temperature region of a flame during the high velocity oxygen flame (HVOF) spray process. The coating became denser, and its hardness became higher via [...] Read more.

Shot peening was used synchronously to improve Fe-based amorphous coating performance by delivering ZrO₂ ceramic particles into a low-temperature region of a flame during the high velocity oxygen flame (HVOF) spray process. The coating became denser, and its hardness became higher via the new process. Moreover, the compressive residual stress was induced by shot peening. The results from the dry friction test indicated that the coating’s wear resistance was enhanced obviously. The wear mechanism of coatings with and without shot peening is an abrasive wear combined with an oxidation wear at wear test conditions of a low load and a low frequency. The coating with the best wear resistance did not have the strongest microhardness but had the highest compressive residual stress. The compressive residual stress had a significant positive influence on the wear resistance at a low frequency, while its effect is weakened at a high frequency. Full article

(This article belongs to the Section Corrosion, Wear and Erosion)

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28 pages, 8489 KiB

Open AccessArticle

MHD Effects on Ciliary-Induced Peristaltic Flow Coatings with Rheological Hybrid Nanofluid

by M. Awais, Zahir Shah, N. Perveen, Aamir Ali, Poom Kumam, Habib ur Rehman and Phatiphat Thounthong

Coatings 2020, 10(2), 186; https://doi.org/10.3390/coatings10020186 - 19 Feb 2020

Cited by 71 | Viewed by 5569

Abstract

Present theoretical investigation is a mathematical illustration of an application to endoscopy by incorporating hybrid nanoparticles and an induced magnetic field with a rheological fluid model for more realistic results. Rheological fluid behavior is characterized by the Ostwald-de-Waele power-law model. A hybrid nanofluid [...] Read more.

Present theoretical investigation is a mathematical illustration of an application to endoscopy by incorporating hybrid nanoparticles and an induced magnetic field with a rheological fluid model for more realistic results. Rheological fluid behavior is characterized by the Ostwald-de-Waele power-law model. A hybrid nanofluid mechanism is considered comprising platelet-shaped nanoparticles since nanoparticles are potential drug transportation tools in biomedical applications. Moreover, ciliary activity is encountered regarding their extensive applications in performing complex functions along with buoyancy effects. An endoscope is inserted inside a ciliated tube and peristalsis occurred due to ciliary activity in the gap between tube and endoscope. A non-Newtonian model is developed by mathematical formulation which is tackled analytically using homotopy analysis. The outcomes are interpreted graphically along with the pressure rise and streamlining configuration for the case of negligible inertial forces and long wavelength. A three-dimensional graphical interpretation of axial velocity is studied as well. Moreover, tables are prepared and displayed for a more physical insight. Full article

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

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23 pages, 5044 KiB

Open AccessArticle

Impact of Degree of Hydrophilicity of Pyridinium Bromide Derivatives on HCl Pickling of X-60 Mild Steel: Experimental and Theoretical Evaluations

by Nurudeen A. Odewunmi, Mohammad A. Jafar Mazumder, Shaikh A. Ali, Norah A. Aljeaban, Bader G. Alharbi, Abdulaziz A. Al-Saadi and Ime B. Obot

Coatings 2020, 10(2), 185; https://doi.org/10.3390/coatings10020185 - 19 Feb 2020

Cited by 17 | Viewed by 3792

Abstract

Dodecyl pyridinium bromide (DDPB), tetradecyl pyridinium bromide (TDPB) and dodecyl 1,1′-bispyridinium dibromide (DDBPB) were successfully synthesized, characterized and evaluated for HCl pickling of X-60 low carbon steel. Order of corrosion inhibitions efficiencies, as revealed by both electrochemical and gravimetric studies, is TDPB > [...] Read more.

Dodecyl pyridinium bromide (DDPB), tetradecyl pyridinium bromide (TDPB) and dodecyl 1,1′-bispyridinium dibromide (DDBPB) were successfully synthesized, characterized and evaluated for HCl pickling of X-60 low carbon steel. Order of corrosion inhibitions efficiencies, as revealed by both electrochemical and gravimetric studies, is TDPB > DDPB > DDBPB. The degree of hydrophilicity of inhibitors as predicted by a partition coefficient (Log P) and supported by a contact angle measurement was found to be responsible for their order of corrosion inhibition efficiencies. Adsorption of DDPB, TDPB, and DDBPB through the pyridinium nitrogen on mild steel surface was confirmed by ATR-FTIR and SEM-EDX analyses. The pyridinium nitrogen was found not to be the only factor responsible for their efficiency, but hydrophobes and the orientation of the hydrophilic ring were responsible, which incline to the deviation of experimental results and the order of Monte Carlo simulation adsorption energies. DDPB, TDPB, and DDBPB obey the Langmuir isotherm model despite major contributions of the film formed on the surface of X-60 mild steel on their overall inhibition corrosion resistance. Full article

(This article belongs to the Special Issue Innovative Organic Coatings)

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17 pages, 6499 KiB

Open AccessEditor’s ChoiceArticle

One-Step Deposition of Polyester/TiO₂ Coatings by Atmospheric Pressure Plasma Jet on Wood Surfaces for UV and Moisture Protection

by Ghiath Jnido, Gisela Ohms and Wolfgang Viöl

Coatings 2020, 10(2), 184; https://doi.org/10.3390/coatings10020184 - 19 Feb 2020

Cited by 17 | Viewed by 5166

Abstract

In this work, polyester/TiO₂ coatings on wood surfaces were prepared in one step via two deposition methods by using an atmospheric pressure plasma jet technique with the aim to further enhance the stabilization of the wood surfaces against UV-radiation and moisture. The [...] Read more.

In this work, polyester/TiO₂ coatings on wood surfaces were prepared in one step via two deposition methods by using an atmospheric pressure plasma jet technique with the aim to further enhance the stabilization of the wood surfaces against UV-radiation and moisture. The first method, based on the combination of plasma spray powder (PSP) coating and liquid precursor plasma spraying (LPPS) coating techniques, used polyester powder and titanium tetraisopropoxide (TTIP) liquid precursor as feedstock. In the second method, the polyester/TiO₂ coatings were prepared by using a mixed powder of polyester micro-particles and TiO₂ nano-particles as feedstock and applied via plasma spray powder coating technique. The surface topology and morphology of the wood samples were observed by scanning electron microscopy (SEM). The SEM results showed the presence of a rough structure after coating with polyester/TiO₂. The surface chemical compositions of the samples were characterized by X-ray photoelectron spectroscopy and by Fourier transform infrared spectroscopy. The wetting behaviour of the coated wood surfaces was studied by measuring the water contact angle. After coating a hydrophilic wood surface with polyester/TiO₂ prepared via (PSP + LPPS), it showed excellent water repellency; the wood surfaces were transformed from hydrophilic to superhydrophobic, while the polyester/TiO₂ coating prepared via (PSP) was hydrophilic. Protection against UV radiation-induced colour changes was determined by UV tests and photo-assisted analysis using the CIELab colour system. The abrasion test results indicated that the polyester-containing films had good abrasion resistance and good adhesion to the wood substrates. Full article

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14 pages, 4501 KiB

Open AccessArticle

Properties of a Plasma-Nitrided Coating and a CrN_x Coating on the Stainless Steel Bipolar Plate of PEMFC

by Meiling Xu, Shumei Kang, Jinlin Lu, Xinyong Yan, Tingting Chen and Zimeng Wang

Coatings 2020, 10(2), 183; https://doi.org/10.3390/coatings10020183 - 17 Feb 2020

Cited by 32 | Viewed by 4284

Abstract

PEMFC are considered to be the most promising for automotive energy because of their good working effect, low temperature, high efficiency, and zero pollution. Stainless steel as a PEMFC bipolar plate has unparalleled advantages in strength, cost, and processability, but it is easy [...] Read more.

PEMFC are considered to be the most promising for automotive energy because of their good working effect, low temperature, high efficiency, and zero pollution. Stainless steel as a PEMFC bipolar plate has unparalleled advantages in strength, cost, and processability, but it is easy to corrode in a PEMFC working environment. In order to improve the corrosion resistance, the surface modification of 316L stainless steel is a feasible solution for PEMFC bipolar plates. In the present study, the plasma-nitrided coating and CrN_x coating were prepared by the plasma-enhanced balanced magnetron sputtering technology on the 316L stainless steel surface. The microstructures, phase compositions, and corrosion resistance behavior of the coatings were investigated. The corrosion behavior of the prepared plasma-nitrided coating and CrN_x coating was investigated by potentiodynamic polarization, potentiostatic polarization, and electrochemical impedance spectroscopy (EIS) in both cathodic and anodic environments. The experimental results show that corrosion resistance of the CrN_x coating was better than the plasma-nitrided coating. It was indicated that the technology process of nitriding first and then depositing Cr was better than nitriding only. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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13 pages, 2935 KiB

Open AccessFeature PaperArticle

Iron-Doped Titanium Dioxide Nanoparticles As Potential Scaffold for Hydrazine Chemical Sensor Applications

by Ahmad Umar, Farid A. Harraz, Ahmed A. Ibrahim, Tubia Almas, Rajesh Kumar, M. S. Al-Assiri and Sotirios Baskoutas

Coatings 2020, 10(2), 182; https://doi.org/10.3390/coatings10020182 - 17 Feb 2020

Cited by 22 | Viewed by 4566

Abstract

Herein, we report the fabrication of a modified glassy carbon electrode (GCE) with high-performance hydrazine sensor based on Fe-doped TiO₂ nanoparticles prepared via a facile and low-cost hydrothermal method. The structural morphology, crystalline, crystallite size, vibrational and scattering properties were examined through [...] Read more.

Herein, we report the fabrication of a modified glassy carbon electrode (GCE) with high-performance hydrazine sensor based on Fe-doped TiO₂ nanoparticles prepared via a facile and low-cost hydrothermal method. The structural morphology, crystalline, crystallite size, vibrational and scattering properties were examined through different characterization techniques, including FESEM, XRD, FTIR, UV–Vis, Raman and photoluminescence spectroscopy. FESEM analysis revealed the high-density synthesis of Fe-doped TiO₂ nanoparticles with the average diameter of 25 ± 5 nm. The average crystallite size of the synthesized nanoparticles was found to be around 14 nm. As-fabricated hydrazine chemical sensors exhibited 1.44 μA µM⁻¹ cm⁻² and 0.236 µM sensitivity and limit of detection (LOD), respectively. Linear dynamic ranged from 0.2 to 30 µM concentrations. Furthermore, the Fe-doped TiO₂ modified GCE showed a negligible inference behavior towards ascorbic acid, uric acid, glucose, SO₄²⁻, NO₃⁻, Pb²⁺ and Ca²⁺ ions on the hydrazine sensing performance. Thus, Fe-doped TiO₂ modified GCE can be efficiently used as an economical, easy to fabricate and selective sensing of hydrazine and its derivatives. Full article

(This article belongs to the Special Issue Mesoporous Metal Oxide Films)

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13 pages, 2327 KiB

Open AccessArticle

The Antibacterial Effects of Quaternary Ammonium Salts in the Simulated Presence of Inhibitors in Root Canals: A Preliminary In-Vitro Study

by Sanjay Kumar Tiwari, Suping Wang, Yannan Huang, Xuedong Zhou, Hockin H. K. Xu, Biao Ren, Xian Peng, Michael D. Weir, Mingyun Li and Lei Cheng

Coatings 2020, 10(2), 181; https://doi.org/10.3390/coatings10020181 - 16 Feb 2020

Cited by 5 | Viewed by 3637

Abstract

To investigate the antibacterial effects of two newly developed quaternary ammonium salts (QAMs)-dimethylaminododecyl methacrylate (DMADDM) and dimethylaminohexadecyl methacrylate (DMAHDM), in the presence of various root canal inhibitors. Streptococcus gordonii, Enterococcus faecalis, Lactobacillus acidophilus and Actinomyces naeslundii were used. Dentine, dentine matrix [...] Read more.

To investigate the antibacterial effects of two newly developed quaternary ammonium salts (QAMs)-dimethylaminododecyl methacrylate (DMADDM) and dimethylaminohexadecyl methacrylate (DMAHDM), in the presence of various root canal inhibitors. Streptococcus gordonii, Enterococcus faecalis, Lactobacillus acidophilus and Actinomyces naeslundii were used. Dentine, dentine matrix and dead bacteria were selected as inhibitors. The antimicrobial efficacy of monomers of DMADDM and DMAHDM was tested against suspensions formed by mixtures of four bacterial species in or without the presence of inhibitors. The inhibition results were compared with chlorhexidine (CHX) and sodium hypochlorite (NaOCl). One-way analyses of variance (ANOVA) followed by Tukey’s multiple comparison test was performed to determine significant differences. The antibacterial effects of DMADDM and DMAHDM were variably inhibited dentine, dentine matrix and dead bacteria. CHX and NaOCl showed substantivity and they inhibited bacteria present in suspension. The concentration of compound decreased in the dentine block due to constant release. Bacterial colonies on the dentine surface and dentine tubules were significantly inhibited by DMADDM and DMAHDM. The antibacterial effects of DMADDM and DMAHDM could be inactivated by dentine, dentine matrix and dead bacteria, while DMADDM and DMAHDM could inhibit bacteria colonization on the dentine surface and kill bacteria present in dentinal tubules. The antibacterial effects of DMADDM and DMAHDM as free monomers in the presence of inhibitors was evaluated for the first time. They could help inhibit the residual bacteria on the dentine surface and in dentinal tubules that may cause persisting infection. Therefore the novel QAMs showed great potentials as root canal medication. Full article

(This article belongs to the Special Issue Recent Developments in Antibacterial and/or Antifouling Surfaces)

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12 pages, 10604 KiB

Open AccessFeature PaperArticle

A Tunable Beamforming Ferroelectric Lens for Millimeter Wavelength Ranges

by Roman Platonov, Andrey Altynnikov and Andrey Kozyrev

Coatings 2020, 10(2), 180; https://doi.org/10.3390/coatings10020180 - 16 Feb 2020

Cited by 7 | Viewed by 4227

Abstract

The advanced design of a millimeter-wave quasi-optical beamforming device (QOBD) based on the ferroelectric ceramic was elaborated and considered. Among the advantages of the proposed design are simplicity and cost-effectiveness in contrast to conventional analog and digital beamforming devices based on array antennas. [...] Read more.

The advanced design of a millimeter-wave quasi-optical beamforming device (QOBD) based on the ferroelectric ceramic was elaborated and considered. Among the advantages of the proposed design are simplicity and cost-effectiveness in contrast to conventional analog and digital beamforming devices based on array antennas. The use of ferroelectric ceramic in the QOBD design allows operating in a wide frequency range up to 100 GHz. The advanced topology of discrete radiotransparent electrodes to provide a realization of different beamforming functions such as beam focusing and beam scanning was considered. The prototype of the proposed QOBD was designed to operate at 60 GHz. The measured radiation pattern of the QOBD prototype is in good agreement with the simulated one. Measurements demonstrate decreasing of beamwidth of the primary antenna radiation pattern by the lens prototype operating in the beam focusing regime. Full article

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

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11 pages, 11228 KiB

Open AccessArticle

Study of TiO₂-Modified Sol Coating Material in the Protection of Stone-Built Cultural Heritage

by Hui Shu, Ming Yang, Qiang Liu and Maobin Luo

Coatings 2020, 10(2), 179; https://doi.org/10.3390/coatings10020179 - 15 Feb 2020

Cited by 19 | Viewed by 3298

Abstract

Coating materials can effectively protect stone-built cultural heritage and, as such, research into coating materials has gained comprehensive attention from researchers. The aim of this work is to prepare a TiO₂-modified sol coating material (TSCM) and study its protective effects on [...] Read more.

Coating materials can effectively protect stone-built cultural heritage and, as such, research into coating materials has gained comprehensive attention from researchers. The aim of this work is to prepare a TiO₂-modified sol coating material (TSCM) and study its protective effects on stone-built cultural heritage. TSCM and pure TiO₂ sol (p-sol, unmodified; for comparison) were applied evenly over the entire surface of stone samples. The prepared stone samples included untreated stone, stone treated with pure sol, and stone treated with TSCM. The protective effects of TSCM were evaluated by water absorption, water vapor permeability, acid resistance, and weather resistance experiments. The results show that stone treated with TSCM has excellent water absorption and water vapor permeability, strong acid resistance, and good weather resistance, compared with untreated stone or stone treated with p-sol. The acid resistance of stone treated by TSCM was 1.75 times higher than that treated with traditional coating materials. The weather resistance cycle number of stone treated by TSCM was four times higher than that treated with organic protective materials. These findings are expected to provide useful suggestions for the protection of stone-built cultural heritage. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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16 pages, 27122 KiB

Open AccessArticle

Influence of a Biocompatible Hydrophilic Needle Surface Coating on a Puncture Biopsy Process for Biomedical Applications

by Fan Gao, Qinghua Song, Zhanqiang Liu, Yonghang Jiang and Xiuqing Hao

Coatings 2020, 10(2), 178; https://doi.org/10.3390/coatings10020178 - 15 Feb 2020

Cited by 8 | Viewed by 4069

Abstract

A puncture biopsy is a widely used, minimally invasive surgery process. During the needle insertion process, the needle body is always in direct contact with a biological soft tissue. Tissue adhesion and different degrees of tissue damage occur frequently. Optimization of the needle [...] Read more.

A puncture biopsy is a widely used, minimally invasive surgery process. During the needle insertion process, the needle body is always in direct contact with a biological soft tissue. Tissue adhesion and different degrees of tissue damage occur frequently. Optimization of the needle surface, and especially the lubrication of the needle surface, can deal with these problems efficiently. Therefore, in this paper, a biocompatible hydrophilic coating was applied onto the surface of a needle to improve the surface quality of the needle surface. Further, a simplified finite element model of insertion was established, and extracorporeal insertion experiments were used to verify the accuracy of the model. Then, by analyzing a simulation model of a coated needle and a conventional needle, the influence of the application of the coated needle on the insertion process was obtained. It can be seen from the results that the coating application relieved the force on the needle and the soft tissue during the insertion process and could significantly reduce friction during the insertion process. At the same time, the deformation of biological soft tissue was reduced, and the adhesion situation between the needle and tissue improved, which optimized the puncture needle. Full article

(This article belongs to the Section Surface Coatings for Biomedicine and Bioengineering)

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14 pages, 6070 KiB

Open AccessArticle

Property of TiO₂-15MgAl₂O₄ Electrical-Heating Coating Prepared by Atmospheric Plasma Spraying and Hydrogen Heat Treatment

by Xiyang Li, Kun Yang, Dezhi Wang, Chunming Deng and Yanzhe Zhou

Coatings 2020, 10(2), 177; https://doi.org/10.3390/coatings10020177 - 14 Feb 2020

Cited by 1 | Viewed by 2600

Abstract

Using TiO₂-15MgAl₂O₄ mixed powder as spray-feed, an electrical-heating coating was successfully fabricated by atmospheric plasma spraying technology. The phase composition, microstructure, and electrical-heating performance of the coating were characterized by XRD, SEM, and cyclic electrification tests, respectively. The [...] Read more.

Using TiO₂-15MgAl₂O₄ mixed powder as spray-feed, an electrical-heating coating was successfully fabricated by atmospheric plasma spraying technology. The phase composition, microstructure, and electrical-heating performance of the coating were characterized by XRD, SEM, and cyclic electrification tests, respectively. The coating samples were heat-treated at 350 °C in a hydrogen atmosphere. The results show that TiO₂-15MgAl₂O₄ coating can be heated over 300 °C within 30 m at 55.1 V which preserves heat for a long time. Before heat treatment, the available heating temperature of the coating decreases significantly with electrification cycles. The resistivity of coating rises rapidly during the cyclic electricity test. After hydrogen heat treatment, the electrical-heating property of coatings is significantly enhanced. Full article

(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)

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13 pages, 9748 KiB

Open AccessArticle

Preparation of WC Reinforced Co-Based Alloy Gradient Coatings on a H13 Mold Steel Substrate by Laser Cladding

by Chenchen Li, Xuefeng Yang, Shouren Wang, Yanjun Wang and Jinlong Cao

Coatings 2020, 10(2), 176; https://doi.org/10.3390/coatings10020176 - 14 Feb 2020

Cited by 13 | Viewed by 3450

Abstract

H13 die steel often fails as a result of physical and chemical effects such as wear, erosion and cyclic stress. Accordingly, the study evaluates Co-based gradient coating on an H13 steel featuring a stress-relieving effect. Scanning electron microscope and X-ray diffraction were used [...] Read more.

H13 die steel often fails as a result of physical and chemical effects such as wear, erosion and cyclic stress. Accordingly, the study evaluates Co-based gradient coating on an H13 steel featuring a stress-relieving effect. Scanning electron microscope and X-ray diffraction were used to analyze the microstructure and phase of the coatings. A microhardness tester and friction and wear tester were used to compare the hardness and wear resistance of the coatings and the substrate, and the wear morphology was observed. A pendulum impact test was used to compare the impact resistance of the coatings and the substrate, and the fracture morphology was observed. Finally, a corrosion test was used to compare the corrosion resistance of coatings and substrate. The results show that the Co-based gradient coatings have good combinations with the substrate, the hard phase content gradually increases from the bottom to the top of the coating, and the crystal microstructure generally maintains a distribution trend from coarse to fine. The hardness of the gradient coatings is significantly higher than the substrate, and from the coating surface to the substrate, the hardness decreases slowly. The wear loss of the coatings is much lower than that of the substrate, the main wear mechanism of the substrate is abrasive wear, and the main wear mechanism of the coatings is brittle spalling. While the gradient coatings increase the surface hardness, the brittleness also increases, the impact resistance of the coatings is lower than that of the substrate, the fracture form of the substrate is a ductile fracture, and the fracture form of the coating is a brittle fracture. The gradient coatings effectively improve the corrosion resistance of the substrate surface, and the higher the content of the reinforcing phase, the better the corrosion resistance of the coatings. Full article

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13 pages, 9835 KiB

Open AccessArticle

High Temperature Tribological Properties of Al₂O₃/NCD Films Investigated Under Ambient Air Conditions

by Vitali Podgursky, Maxim Yashin, Taivo Jõgiaas, Mart Viljus, Asad Alamgir, Mati Danilson and Andrei Bogatov

Coatings 2020, 10(2), 175; https://doi.org/10.3390/coatings10020175 - 14 Feb 2020

Cited by 3 | Viewed by 3363

Abstract

Comparative analysis of dry sliding wear behavior of nanocrystalline diamond (NCD) films and NCD films coated with a thin Al₂O₃ layer (Al₂O₃/NCD) is the main goal of the present study. Plasma-enhanced chemical vapor deposition (PECVD) and [...] Read more.

Comparative analysis of dry sliding wear behavior of nanocrystalline diamond (NCD) films and NCD films coated with a thin Al₂O₃ layer (Al₂O₃/NCD) is the main goal of the present study. Plasma-enhanced chemical vapor deposition (PECVD) and atomic layer deposition (ALD) methods were used to prepare the NCD and alumina films, respectively. Sliding wear tests were conducted at room temperature (RT), 300 and 450 °C in air. Independent of type of specimen, superlubricating behavior with the coefficient of friction (COF) in the range of 0.004‒0.04 was found for the tests at 300 °C. However, the COF value measured on the Al₂O₃/NCD films in the tests at 450 °C is lower than that for the NCD film. A relatively short run-in period and a stable COF value of about 0.15 were observed at this temperature for the Al₂O₃/NCD films. The width of the wear scars measured on the Al₂O₃/NCD films after the tests at 450 °C is significantly smaller in comparison with the NCD film. The apparent wear volume of the wear scar on the NCD film tested at 450 °C was noticeably higher than that on the Al₂O₃/NCD films. Full article

(This article belongs to the Section Tribology)

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11 pages, 5438 KiB

Open AccessArticle

Fabrication of Cotton Fabric with Superoleophilic/Superhydrophobic Characteristic on the Modified Surface by Using Fluoroalkylated Oligomeric Silica/Triazine Derivative Nanocomposites

by Katsumi Yamashita, Akemi Yasukawa and Hideo Sawada

Coatings 2020, 10(2), 174; https://doi.org/10.3390/coatings10020174 - 14 Feb 2020

Cited by 6 | Viewed by 3085

Abstract

Two fluoroalkylated vinyltrimethoxysilane oligomer (R_F-(CH₂CHSi(OMe)₃)_n-R_F; n = 2, 3; R_F = CF(CF₃)OC₃F₇:R_F-VMSi) in methanol reacted with aqueous sodium carbonate solution containing 2-hydroxy-4,6-dichloro-1,3,5-triazine sodium salt [...] Read more.

Two fluoroalkylated vinyltrimethoxysilane oligomer (R_F-(CH₂CHSi(OMe)₃)_n-R_F; n = 2, 3; R_F = CF(CF₃)OC₃F₇:R_F-VMSi) in methanol reacted with aqueous sodium carbonate solution containing 2-hydroxy-4,6-dichloro-1,3,5-triazine sodium salt (TAZ) to provide two fluoroalkylated oligomeric silica/TAZ nanocomposites (R_F-VMSiO₂/TAZ). The original cotton fabric gives an oleophilic/hydrophilic property on its surface; however, modified cotton fabric surface with R_F-VMSiO₂/TAZ composites was demonstrated to provide highly oleophobic/superhydrophobic property on the surface. We can observe a remarkable time-dependent decrease of the contact angle of dodecane (oil) on the modified surfaces, and the contact angles of dodecane were found to decrease effectively from 55

^{\circ}

–83

^{\circ}

to 0

^{\circ}

over 5–30 s to supply superoleophilicity with keeping the superhydrophobic property on the surfaces. The modified cotton fabric having superoleophilic/superhydrophobic property was applicable to the separation membrane to separate oil and water. Interestingly, modified cotton fabric was found to adsorb efficiently only droplets of oil spread on the water interface due to its unique surface wettability. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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16 pages, 13270 KiB

Open AccessArticle

The Microstructure and Selected Mechanical Properties of Al₂O₃ + 13 wt % TiO₂ Plasma Sprayed Coatings

by Monika Michalak, Leszek Łatka, Paweł Sokołowski, Aneta Niemiec and Andrzej Ambroziak

Coatings 2020, 10(2), 173; https://doi.org/10.3390/coatings10020173 - 13 Feb 2020

Cited by 21 | Viewed by 4224

Abstract

The Al₂O₃ + TiO₂ coatings are of the interest of surface technology and tribology due to their good wear resistance and enhanced toughness comparing to pure Al₂O₃ coatings. However, the detailed effect of the used feedstock [...] Read more.

The Al₂O₃ + TiO₂ coatings are of the interest of surface technology and tribology due to their good wear resistance and enhanced toughness comparing to pure Al₂O₃ coatings. However, the detailed effect of the used feedstock powder, is often neglected. Here, this work focuses on the deposition of Al₂O₃ + 13 wt % TiO₂ coatings by atmospheric plasma spraying (APS) method as well as on their microstructure, phase composition and selected mechanical properties, in the reference to the route of the powder feedstock preparation. The commercial powder Metco 6221 in agglomerated and sintered form was used as a feedstock material during spraying, due to the fact that, so far, sintered or cladded powders are the most studied ones. The 2^k + 1 spray experiment allowed to evaluate the influence of two variables, namely spray distance and torch linear velocity, on the coating microstructure. Afterwards, the coating adhesion was measured by the means of pull-off test. The correlations between Vickers microhardness, fracture toughness (Kc) as well as the coating morphology and phase composition were investigated. Finally, the dry sliding wear resistance was studied by using Ball-on-Disc method. Full article

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20 pages, 3967 KiB

Open AccessFeature PaperArticle

The Effect of the Methyl and Ethyl Group of the Acrylate Precursor in Hybrid Silane Coatings Used for Corrosion Protection of Aluminium Alloy 7075-T6

by Damir Hamulić, Peter Rodič, Matic Poberžnik, Marjan Jereb, Janez Kovač and Ingrid Milošev

Coatings 2020, 10(2), 172; https://doi.org/10.3390/coatings10020172 - 13 Feb 2020

Cited by 28 | Viewed by 5186

Abstract

This study investigated polysiloxane hybrid sol-gel coatings synthesized from tetraethyl orthosilicate (TEOS), 3-(trimethoxysilyl)propyl methacrylate (MAPTMS) and two different precursors, i.e., methyl- or ethyl- methacrylate (MMA or EMA), as corrosion protection of aluminium alloy 7075-T6. The hypothesis was that the additional alkyl group might [...] Read more.

This study investigated polysiloxane hybrid sol-gel coatings synthesized from tetraethyl orthosilicate (TEOS), 3-(trimethoxysilyl)propyl methacrylate (MAPTMS) and two different precursors, i.e., methyl- or ethyl- methacrylate (MMA or EMA), as corrosion protection of aluminium alloy 7075-T6. The hypothesis was that the additional alkyl group might affect the chemical properties and, consequently, the corrosion properties. Synthesis of the sols proceeded in two steps, each involving either MMA or EMA in the same molar ratio. The resulting sols, siloxane-(poly(methyl methacrylate-co-MAPTMS)) or siloxane-(poly(ethyl methacrylate-co-MAPTMS)), were applied on aluminium alloy followed by characterization in terms of chemical structure and composition, topography, wettability, adhesion and corrosion resistance in 0.1 M sodium chloride solution. The chemical properties of sols, monoliths and coatings were investigated using Fourier transform infrared spectrometry, solid state nuclear magnetic resonance spectrometry, X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Coatings were similar in terms of surface topography, while the wettability of the coating with EMA showed 6° greater water contact angle compared to the coating with MMA. Both coatings were shown, by electrochemical impedance spectroscopy in 0.1 M NaCl solution, to act as barriers to protect the underlying substrate in which coating with EMA exhibits better protection properties after 2 months of immersion. Adhesion tests confirmed the highest grade of adhesion to the substrate for both coatings. Testing in a salt-spray chamber demonstrated excellent corrosion protection, where coatings remaining intact after more than 600 h of exposure. Full article

(This article belongs to the Special Issue Corrosion Science and Surface Engineering)

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18 pages, 4831 KiB

Open AccessReview

Optimization of Performance Parameters and Mechanism of Bionic Texture on Friction Surface

by Qimin Hou, Xuefeng Yang, Jian Cheng, Shouren Wang, Derong Duan, Jupeng Xiao and Wanyang Li

Coatings 2020, 10(2), 171; https://doi.org/10.3390/coatings10020171 - 13 Feb 2020

Cited by 45 | Viewed by 5261

Abstract

In this paper, a variety of micro-textures made by imitating the biological body surface are mentioned, and four common biomimetic texture types—convex hull, pit, groove and corrugation—are summarized by referring to a large number of literatures. These texture types that are widely used [...] Read more.

In this paper, a variety of micro-textures made by imitating the biological body surface are mentioned, and four common biomimetic texture types—convex hull, pit, groove and corrugation—are summarized by referring to a large number of literatures. These texture types that are widely used are those of the grooves and the pits of non-smooth surface because their viscosity drag reduction effects are relatively optimal for wear-resistance; in view of these two types of textures (with others including pit diameter, groove width, depth and area of share, and morphology spacing), we use data analysis and comparisons to find optimal parameter values in order to find the optimal effect of drag reduction and anti-sticking wear-resistance. Several texture processing methods are briefly introduced through case analysis and an illustration of the viscosity drag reduction mechanism of wear-resistance, and general fluid dynamic pressure is deduced from a theory formula in order to facilitate future research work on the basis of the optimal parameters to further improve the friction, wear lubrication, and hydrophobic properties, thus improving the bionic texture surface efficiency of saving energy and reducing consumption in industrial applications. Full article

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20 pages, 831 KiB

Open AccessArticle

Analysis of Magnetic Properties of Nano-Particles Due to a Magnetic Dipole in Micropolar Fluid Flow over a Stretching Sheet

by Liaqat Ali, Xiaomin Liu, Bagh Ali, Saima Mujeed, Sohaib Abdal and Shahid Ali Khan

Coatings 2020, 10(2), 170; https://doi.org/10.3390/coatings10020170 - 13 Feb 2020

Cited by 72 | Viewed by 3839

Abstract

This article explores the impact of a magnetic dipole on the heat transfer phenomena of different nano-particles Fe (ferromagnetic) and Fe₃O₄ (Ferrimagnetic) dispersed in a base fluid (

60 %

water +

40 %

ethylene glycol) on micro-polar fluid flow [...] Read more.

This article explores the impact of a magnetic dipole on the heat transfer phenomena of different nano-particles Fe (ferromagnetic) and Fe₃O₄ (Ferrimagnetic) dispersed in a base fluid (

60 %

water +

40 %

ethylene glycol) on micro-polar fluid flow over a stretching sheet. A magnetic dipole in the presence of the ferrities of nano-particles plays an important role in controlling the thermal and momentum boundary layers. The use of magnetic nano-particles is to control the flow and heat transfer process through an external magnetic field. The governing system of partial differential equations is transformed into a system of coupled nonlinear ordinary differential equations by using appropriate similarity variables, and the transformed equations are then solved numerically by using a variational finite element method. The impact of different physical parameters on the velocity, the temperature, the Nusselt number, and the skin friction coefficient is shown. The velocity profile decreases in the order Fe (ferromagnetic fluid) and Fe₃O₄ (ferrimagnetic fluid). Furthermore, it was observed that the Nusselt number is decreasing with the increasing values of boundary parameter

(δ)

, while there is controversy with respect to the increasing values of radiation parameter

(N)

. Additionally, it was observed that the ferromagnetic case gained maximum thermal conductivity, as compared to ferrimagnetic case. In the end, the convergence of the finite element solution was observed; the calculations were found by reducing the mesh size. Full article

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20 pages, 5034 KiB

Open AccessFeature PaperArticle

Titanium Dioxide Coatings Doubly-Doped with Ca and Ag Ions as Corrosion Resistant, Biocompatible, and Bioactive Materials for Medical Applications

by Barbara Burnat, Patrycja Olejarz, Damian Batory, Michal Cichomski, Marta Kaminska and Dorota Bociaga

Coatings 2020, 10(2), 169; https://doi.org/10.3390/coatings10020169 - 13 Feb 2020

Cited by 10 | Viewed by 3933

Abstract

The aim of this study was to develop a multifunctional biomedical coating that is highly corrosion resistant, biocompatible, and reveals the bioactive properties. For that purpose, titanium dioxide coatings doubly-doped with Ca and Ag ions were deposited by dip-coating onto M30NW biomedical steel. [...] Read more.

The aim of this study was to develop a multifunctional biomedical coating that is highly corrosion resistant, biocompatible, and reveals the bioactive properties. For that purpose, titanium dioxide coatings doubly-doped with Ca and Ag ions were deposited by dip-coating onto M30NW biomedical steel. The influence of different ratios of Ca and Ag dopants on morphology, surface structure, corrosion resistance, bioactivity, wettability, and biological properties of TiO₂-based sol-gel coatings was studied and discussed. Comprehensive measurements were performed including atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray reflectivity (XRR), corrosion tests, immersion test, contact angle, as well as biological evaluation. The obtained results confirmed that anatase-based coatings containing Ca and Ag ions, independently of their molar ratio in the coating, are anticorrosive, hydrophilic, and bioactive. The results of the biological evaluation indicated that investigated coatings are biocompatible and do not reduce the proliferation ability of the osteoblasts cells. Full article

(This article belongs to the Special Issue Functional Ceramic Coatings)

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14 pages, 4768 KiB

Open AccessArticle

Effect of Emulsifier on the Structure and Properties of Waterborne Silicone Antifouling Coating

by Sikui Liu, Zhanping Zhang and Yuhong Qi

Coatings 2020, 10(2), 168; https://doi.org/10.3390/coatings10020168 - 12 Feb 2020

Cited by 14 | Viewed by 4838

Abstract

Three-component waterborne silicone antifouling coatings, which could cured at room temperature, were prepared, respectively, with cationic (stearyl trimethyl ammonium bromide) or anionic (sodium dodecyl benzene sulfonate) silicone emulsion as a film-forming substance, γ-methacryloxypropyltrimethoxysilane as a curing agent and dibutyltin dilaurate as a catalyst. [...] Read more.

Three-component waterborne silicone antifouling coatings, which could cured at room temperature, were prepared, respectively, with cationic (stearyl trimethyl ammonium bromide) or anionic (sodium dodecyl benzene sulfonate) silicone emulsion as a film-forming substance, γ-methacryloxypropyltrimethoxysilane as a curing agent and dibutyltin dilaurate as a catalyst. The effect of emulsifier on the structure and properties of silicone coating was studied. The results showed that the coating with cationic silicone emulsion had high crosslinking density, and its surface is smooth. The surface of the coating prepared by the anionic silicone emulsion is rough. Emulsifier type had no obvious effect on the surface free energy of the waterborne silicone coating. The coatings have the characteristics of low surface energy and excellent bacterial desorption properties. Stearyl trimethyl ammonium bromide in the cured coating can reduce the adhesion of marine bacteria on the coating surface. Both the emulsifiers can inhibit the activity of Navicula Tenera. The waterborne silicone coating prepared by cationic silicone emulsion has better comprehensive mechanical properties and antifouling performance. Full article

(This article belongs to the Special Issue Antimicrobial/Antibiofilm Surfaces)

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20 pages, 6001 KiB

Open AccessArticle

Water Pipes Corrosion Inhibitors for Q235 Steel in Hydrochloric Acid Medium Using Spiropyrazoles Derivatives

by A. M. Eldesoky, Hala. M. Hassan, Abdu Subaihi, Abeer El Shahawy and Thoraya A. Farghaly

Coatings 2020, 10(2), 167; https://doi.org/10.3390/coatings10020167 - 12 Feb 2020

Cited by 10 | Viewed by 3527

Abstract

Water pipes and drinking water quality deterioration in distribution systems and sea water desalination impose the use of corrosion inhibitors. The protective effect of spiropyrazole derivatives against Q235 steel and its adsorption performance were examined in solution of 1 M HCl utilizing TP [...] Read more.

Water pipes and drinking water quality deterioration in distribution systems and sea water desalination impose the use of corrosion inhibitors. The protective effect of spiropyrazole derivatives against Q235 steel and its adsorption performance were examined in solution of 1 M HCl utilizing TP (Tafel polarization), electrochemical frequency modulation (EFM), and electrochemical impedance spectroscopy (EIS) tests. The outcome data from hindrance efficiency rise with the dose of inhibitor. The orders of %IE of spiropyrazole derivatives are given: (1) > (2) > (3).It was noted that the values of E_HOMO and E_LUMO dropping in order run parallel to the improvement in %IE, which support the preceding order. EIS spectra exhibited one capacitive loop and approve the protective ability. Molecular docking was utilized to get a full picture on the binding mode among spiropyrazoles derivatives and the receptor of 3tt8-hormone of crystal structure examination of Cu human insulin derivative. The morphology of protected Q235 steel was evaluated by checking electron magnifying instrument innovation with energy dispersive X-beam spectroscopy (SEM–EDX). Full article

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16 pages, 2603 KiB

Open AccessReview

The Use of Edible Films Based on Sodium Alginate in Meat Product Packaging: An Eco-Friendly Alternative to Conventional Plastic Materials

by Roxana Gheorghita (Puscaselu), Gheorghe Gutt and Sonia Amariei

Coatings 2020, 10(2), 166; https://doi.org/10.3390/coatings10020166 - 12 Feb 2020

Cited by 116 | Viewed by 19787

Abstract

The amount of plastics used globally today exceeds a million tonnes annually, with an alarming annual growth. The final result is that plastic packaging is thrown into the environment, and the problem of waste is increasing every year. A real alternative is the [...] Read more.

The amount of plastics used globally today exceeds a million tonnes annually, with an alarming annual growth. The final result is that plastic packaging is thrown into the environment, and the problem of waste is increasing every year. A real alternative is the use bio-based polymer packaging materials. Research carried out in the laboratory context and products tested at the industrial level have confirmed the success of replacing plastic-based packaging with new, edible or completely biodegradable foils. Of the polysaccharides used to obtain edible materials, sodium alginate has the ability to form films with certain specific properties: resistance, gloss, flexibility, water solubility, low permeability to O₂ and vapors, and tasteless or odorless. Initially used as coatings for perishable or cut fresh fruits and vegetables, these sodium alginate materials can be applied to a wide range of foods, especially in the meat industry. Used to cover meat products, sodium alginate films prevent mass loss and degradation of color and texture. The addition of essential oils prevents microbial contamination with Escherichia coli, Salmonella enterica, Listeria monocytogenes, or Botrytis cinerea. The obtained results promote the substitution of plastic packaging with natural materials based on biopolymers and, implicitly, of sodium alginate, with or without other natural additions. These natural materials have become the packaging of the future. Full article

(This article belongs to the Special Issue Novel Advances in Food Contact Materials)

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