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10 pages, 38250 KiB

Open AccessArticle

Microstructure and Performance of Ni/TiN Coatings Deposited by Laser Melting Deposition on 40Cr Substrates

by Yan Wang and Wang Gao

Coatings 2022, 12(3), 367; https://doi.org/10.3390/coatings12030367 - 10 Mar 2022

Cited by 7 | Viewed by 2399

Abstract

The current study reports the successful preparation of Ni/TiN coatings via laser melting deposition (LMD) for repairing the shaft of an electric submersible pump (ESP). The surface morphology, microstructure, phase composition, microhardness, shear strength, and wear resistance were investigated using a scanning electron [...] Read more.

The current study reports the successful preparation of Ni/TiN coatings via laser melting deposition (LMD) for repairing the shaft of an electric submersible pump (ESP). The surface morphology, microstructure, phase composition, microhardness, shear strength, and wear resistance were investigated using a scanning electron microscope (SEM), X-ray diffractometer (XRD), microhardness meter, shear strength test machine, and friction and wear tester. Among the three coatings, the Ni/TiN coating deposited at 1.5 kW processed fine grains with an evenly dispersed and compact structure. The Ni/TiN coating revealed a face-centered cubic (f c c) lattice that exhibited diverse orientations due to the laser powers. The Ni/TiN coating deposited at 1 kW had the lowest average microhardness of 768 HV, while the Ni/TiN coating deposited at 1.5 kW had the highest average hardness of 843 HV. The shear displacements of the Ni/TiN coatings obtained at 1, 1.5, and 2 kW were 0.68, 0.54, and 0.61 mm, respectively. The Ni/TiN coating deposited at 1.5 kW had the lowest friction coefficient among all coatings, with an average value of only 0.44. Additionally, the Ni/TiN coating deposited at 1.5 kW exhibited the highest wear resistance. The presence of Ni, Ti, N, Cr, and Fe elements on the surface of the shaft of the ESP, indicated that the LMD technology had successfully repaired the shaft. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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9 pages, 7265 KiB

Open AccessArticle

The Surface Properties of an Aviation Aluminum Alloy after Laser Cleaning

by Yuan Ren, Liming Wang, Jianfeng Li, Wei Cheng and Xinqiang Ma

Coatings 2022, 12(2), 273; https://doi.org/10.3390/coatings12020273 - 18 Feb 2022

Cited by 12 | Viewed by 3253

Abstract

In this study, we explored the effects of a laser cleaning process on the surface properties of an aerospace aluminum alloy. We performed surface cleaning on an AA2024 aluminum alloy. Through SEM and EDS analyses on the surface of the aluminum alloy samples [...] Read more.

In this study, we explored the effects of a laser cleaning process on the surface properties of an aerospace aluminum alloy. We performed surface cleaning on an AA2024 aluminum alloy. Through SEM and EDS analyses on the surface of the aluminum alloy samples after cleaning, the cleaning effect on the aluminum alloy under different laser energy densities was studied. After laser cleaning, residual stress, hardness, friction, and wear tests were performed on the aluminum alloy samples. The experimental results demonstrated that the oxides on the surface of AA2024 could be effectively removed when the laser energy density was 10.5 J/cm². With an increase in the laser energy density, the friction and wear properties of the AA2024 surface could be improved. Laser cleaning could also generate a new hardened layer and residual tensile stress on the surface of AA2024. This article provides a reference for applying laser cleaning in the aerospace field by studying the structure and mechanical properties of an aluminum alloy after laser cleaning. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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13 pages, 2543 KiB

Open AccessArticle

Research into Carbon Dioxide Curing’s Effects on the Properties of Reactive Powder Concrete with Assembly Unit of Sulphoaluminate Cement and Ordinary Portland Cement

by Hongfei Cao, Zhao Liang, Xi Peng, Xin Cai, Kewei Wang, Hui Wang and Zhongda Lyu

Coatings 2022, 12(2), 209; https://doi.org/10.3390/coatings12020209 - 5 Feb 2022

Cited by 16 | Viewed by 2507

Abstract

Excessive emissions of carbon dioxide can lead to greenhouse effect thus destroying the ecological balance. Therefore, effective measures need to be taken to reduce the emission of carbon dioxide. In this study, the influence of carbon dioxide curing on the mechanical strength and [...] Read more.

Excessive emissions of carbon dioxide can lead to greenhouse effect thus destroying the ecological balance. Therefore, effective measures need to be taken to reduce the emission of carbon dioxide. In this study, the influence of carbon dioxide curing on the mechanical strength and NaCl freeze-thaw deterioration of reactive powder concrete (RPC) with the assembly unit of sulphoaluminate cement and ordinary Portland cement was investigated. The ratio of sulphoaluminate cement ranged from 0% to 100% by the total mass of cement with the curing age ranging from 1 d to 28 d. The mechanical strength of RPC with 50% ordinary Portland cement and 50% sulphoaluminate cement containing the polypropylene fibers ranging from 1% to 4% by volume of RPC were investigated. Moreover, the following mass and mechanical strength loss rates, the carbonation depth, the chloride ion migration coefficient and the relative dynamic elastic modulus (RDEM) during NaCl freeze-thaw cycles were determined. Finally, the scanning electron microscope (SEM) and X-ray diffraction were applied in investigating the carbonation process of RPC. Results showed that the addition of sulphoaluminate cement could improve the mechanical strength of RPC at low curing age (lower than 7 d). However, when the cuing age reached 7 d, the sulphoaluminate cement demonstrated negative effect on the mechanical strength. Moreover, the carbon dioxide curing led to increases in the mechanical strength and when ordinary Portland cement was added the enhancing effect was more obvious. Furthermore, the carbon dioxide curing could effectively improve the resistance of NaCl freeze-thaw cycles and increase the carbonation depth. Finally, the increasing dosages of polypropylene fibers were advantageous to the mechanical strength and the resistance of NaCl freeze-thaw cycles. From the researching results of the microscopic performance, the carbon dioxide curing could improve the compactness of hydration products and reduce the content of calcium hydroxide especially at the curing age of 3 days. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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11 pages, 2395 KiB

Open AccessArticle

A Method for Calculating the Reliability of Welded Metal Bellows for Mechanical Seals

by Zhong Zhang, Chenbo Ma, Jianjun Sun, Yuyan Zhang and Xingya Ni

Coatings 2022, 12(2), 175; https://doi.org/10.3390/coatings12020175 - 29 Jan 2022

Cited by 3 | Viewed by 3529

Abstract

Welded metal bellows are an elastic element widely used in the field of mechanical seals. The main objective of the present study was to investigate the reliability of welded metal bellows in mechanical seals under specified working conditions. To this end, a stress [...] Read more.

Welded metal bellows are an elastic element widely used in the field of mechanical seals. The main objective of the present study was to investigate the reliability of welded metal bellows in mechanical seals under specified working conditions. To this end, a stress relaxation test bench was built to obtain the residual elastic force data of welded metal bellows under different compression loads in high-temperature environments. Then, the elastic force loss equation of the bellows was fitted. Moreover, a failure judgment form of welded metal bellows in the mechanical seal is proposed. According to the calculation relationship between the seal face pressure and the welded metal bellows’ elastic force, the elasticity force loss range of the bellows was 556–708 N. Finally, according to the elastic force loss equation, elastic force loss was determined. The maintenance time of the welded metal bellows, and the bellow’s failure limit state equation were determined, and the limit state equation was substituted into the center point method. The reliability of the welded metal bellows was 0.9958. The results show that the new failure criterion and the center point reliability calculation method proposed in this paper have certain practical value for the rapid reliability prediction of welded metal bellows. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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10 pages, 3456 KiB

Open AccessArticle

Forecast the Microhardness of Ni-TiN Nanoplatings via an Artificial Neural Network Model

by Yan Liu, Xingguo Han, Li Kang, Binwu Wang and Hongxia Xiang

Coatings 2022, 12(2), 145; https://doi.org/10.3390/coatings12020145 - 26 Jan 2022

Cited by 3 | Viewed by 2320

Abstract

This study used a backward propagation (BP) model to estimate the microhardness of Ni-TiN nanoplatings prepared using pulse electrodeposition. The influence of electroplating parameters on the microhardness of Ni-TiN nanoplatings was discussed. These parameters included the concentration of the TiN particle, pulse frequency, [...] Read more.

This study used a backward propagation (BP) model to estimate the microhardness of Ni-TiN nanoplatings prepared using pulse electrodeposition. The influence of electroplating parameters on the microhardness of Ni-TiN nanoplatings was discussed. These parameters included the concentration of the TiN particle, pulse frequency, duty cycle, and current density. The surface morphology, microstructure, and microhardness of Ni-TiN nanoplatings were examined using white-light interfering profilometry, scanning electron microscopy, Rockwell hardness testing, and high-resolution transmission emission microscopy. The Ni-TiN thin film prepared by pulse electrodeposition had a surface roughness of about 0.122 µm, and the average size of the Ni and TiN grains on this film was 61.8 and 31.3 nm, respectively. The optimal process parameters were determined based on the maximum microhardness of the deposited Ni-TiN nanoplatings, which included an 8 g/L TiN particle concentration, a 5 A/dm² current density, an 80 Hz pulse frequency, and a 0.7 duty cycle. It could be concluded that the BP model would accurately forecast the microhardness of Ni-TiN nanoplatings, with a maximal error of about 1.04%. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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15 pages, 46567 KiB

Open AccessArticle

Process Simulation and Abrasion Behavior of Jet Electrodeposited Ni–TiN Nanocoatings

by Zhongguo Yang, Shujuan Yi, Longkui Cao, Songhao Tang and Qiang Li

Coatings 2022, 12(1), 86; https://doi.org/10.3390/coatings12010086 - 12 Jan 2022

Cited by 12 | Viewed by 2287

Abstract

In this work, we study jet-electrodeposited Ni–TiN composite nanocoatings (CNCs) for improving abrasion resistance as a function of various nozzle diameters. In addition, COMSOL software is utilized to simulate the process of jet electrodeposition, particularly the influence of spraying speed and pressure of [...] Read more.

In this work, we study jet-electrodeposited Ni–TiN composite nanocoatings (CNCs) for improving abrasion resistance as a function of various nozzle diameters. In addition, COMSOL software is utilized to simulate the process of jet electrodeposition, particularly the influence of spraying speed and pressure of the electrolyte on the abrasion resistance of coatings. Optimization of the nozzle diameter to obtain uniform and high-performance coatings showed that a Φ7 mm nozzle diameter generated the optimum spraying speed and spraying pressure, which results in good micro-hardness and abrasion resistance of the Ni–TiN CNCs. Under these conditions, the 45 steel substrates are coated with a compact layer of uniform and nano-sized TiN particles, which are responsible for the high abrasion resistance of our Ni–TiN CNCs. Our study may motivate researchers to study jet electrodeposition in order to obtain abrasion-resistant coatings. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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11 pages, 2715 KiB

Open AccessArticle

Influence of Waste Fly Ash on the Rheological Properties of Fresh Cement Paste and the Following Electrical Performances and Mechanical Strengths of Hardened Specimens

by Lili Cui and Hui Wang

Coatings 2021, 11(12), 1558; https://doi.org/10.3390/coatings11121558 - 18 Dec 2021

Cited by 11 | Viewed by 2511

Abstract

Waste fly ash (WFA) is a kind of solid waste without reasonable disposition. The WFA with active substance can promote the cement hydration, therefore, WFA may enhance the mechanical strengths of cement-based materials. In this paper, the rheological properties (slump flow and plastic [...] Read more.

Waste fly ash (WFA) is a kind of solid waste without reasonable disposition. The WFA with active substance can promote the cement hydration, therefore, WFA may enhance the mechanical strengths of cement-based materials. In this paper, the rheological properties (slump flow and plastic viscosity) of fresh cement paste with WFA ranging from 0% to 25% by mass ratio of cement were studied. The alternating current (AC) electrical resistance and direct current (DC) resistance time curves were determined. The AC impedance spectroscopy curves of the specimens cured for 1 day and 28 days were obtained. Finally, the mechanical strengths of hardened cement paste cured for 1 day, 3 days, 7 days, and 28 days were tested. The results showed that the slump flow was decreased and the plastic viscosity was increased by the addition of WFA and the increasing curing time. The AC electrical resistance increased in the form of the quadratic function with the cuing age. Meanwhile, the addition of WFA demonstrated an enhancing effect on the electrical conduction of cement paste. The variation rate of DC electrical resistance during the testing time increased with the increasing dosages of WFA and the curing age. The mechanical strengths increased with the addition of curing time and the content of WFA. The increasing rate of mechanical strengths increased with the addition of WFA (0~15%) and decreased with curing time. However, when the dosage of WFA increased from 15% to 25%, the increasing rate decreased. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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15 pages, 4591 KiB

Open AccessArticle

Effects of Three Different Types of Aloin on Optical, Mechanical, and Antibacterial Properties of Waterborne Coating on Tilia europaea Surface

by Xiaoxing Yan and Nan Huang

Coatings 2021, 11(12), 1537; https://doi.org/10.3390/coatings11121537 - 14 Dec 2021

Cited by 7 | Viewed by 2864

Abstract

The microcapsules were prepared by using melamine-formaldehyde resin as the wall material and aloin as the core material. The aloin was dissolved in ethanol and water to prepare microcapsules. The aloin powder, the aloin microcapsules prepared with ethanol as the solvent, and the [...] Read more.

The microcapsules were prepared by using melamine-formaldehyde resin as the wall material and aloin as the core material. The aloin was dissolved in ethanol and water to prepare microcapsules. The aloin powder, the aloin microcapsules prepared with ethanol as the solvent, and the aloin microcapsules prepared with water as the solvent were, respectively, added to the waterborne coating with different contents and coated on the surface of Tilia europaea. The effects of different modifiers and contents on the coating’s optical properties, mechanical properties, and antibacterial properties were explored. The results showed that the aloin microcapsules prepared with ethanol as the solvent had good morphology and comprehensive properties. When the content was 7.0%, the color difference of the waterborne coating was small, the adhesion was grade 3, the impact resistance was 12 kg·cm, and the antibacterial rate was 87.8%. In terms of antibacterial properties, the uncoated aloin powder, the coated aloin microcapsules prepared with ethanol as the solvent, and the aloin microcapsules prepared with water all have certain antibacterial properties and the antibacterial rates reached 99.2%, 97.3%, and 67.3%, respectively. This study provides a certain reference for developing antibacterial wood furniture coatings. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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7 pages, 2391 KiB

Open AccessArticle

Preparation, Characterization, and Terahertz Spectroscopy Characteristics of Reduced Graphene Oxide-Doped Epoxy Resin Coating

by Mian Zhong, Xin Dai, Hongxing Xiang, Bingwei Liu, Xin Zhao, Dongshan Wei, Xiaoguang Tu, Zhihao Wang, Yan Gong, Yajun Xu and Mingxia He

Coatings 2021, 11(12), 1503; https://doi.org/10.3390/coatings11121503 - 6 Dec 2021

Cited by 9 | Viewed by 3365

Abstract

Reduced graphene oxide has attracted numerous interests due to its unique, superior electronic, optical, mechanical, and chemical properties. An epoxy resin with excellent mechanical and electrical properties can be obtained by doping with reduced graphene oxide to enhance the function of the polymer. [...] Read more.

Reduced graphene oxide has attracted numerous interests due to its unique, superior electronic, optical, mechanical, and chemical properties. An epoxy resin with excellent mechanical and electrical properties can be obtained by doping with reduced graphene oxide to enhance the function of the polymer. Here, we prepared a uniform reduced graphene oxide/epoxy resin coating with a different reduced graphene oxide content and characterized it using a field-emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), Raman, and Fourier transform infrared spectrometer (FTIR). Furthermore, the spectral characteristics of the composite coating in the terahertz band were discussed. The cross-sectional SEM results show that a fold structure with ductile failure was intensively formed due to the compatibility of graphene and polymer materials. Both the Raman G and Raman 2D peaks of reduced graphene oxide were confirmed using Raman spectrum testing. The diffraction peak of reduced graphene oxide at 24° disappeared within the reduced graphene oxide/epoxy resin coating, and a wide diffraction peak of the amorphous structure was formed together. Additionally, the intensity of the Raman spectrum increased significantly with increased reduced graphene oxide content, thereby making the surface electrical resistance of the coatings decrease exponentially. Additionally, the intensity of the terahertz time-domain signal and frequency-domain power spectrum linearly reduced with increased reduced graphene oxide concentration. However, the terahertz absorption coefficient and refractive index both increased gradually with increased reduced graphene oxide doping due to increased orientation polarization in the composite coating. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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14 pages, 3033 KiB

Open AccessArticle

Research on the Mechanical Strengths and the Following Corrosion Resistance of Inner Steel Bars of RPC with Rice Husk Ash and Waste Fly Ash

by Lili Cui and Hui Wang

Coatings 2021, 11(12), 1480; https://doi.org/10.3390/coatings11121480 - 1 Dec 2021

Cited by 20 | Viewed by 2353

Abstract

In this paper, the slump flow and mechanical strengths (compressive and flexural strengths) of the reactive powder concrete (RPC) with rice husk ash (RHA) and waste fly ash (WFA) were investigated. The following corrosion resistance of steel bars-reinforced specimens was researched. The ultrasonic [...] Read more.

In this paper, the slump flow and mechanical strengths (compressive and flexural strengths) of the reactive powder concrete (RPC) with rice husk ash (RHA) and waste fly ash (WFA) were investigated. The following corrosion resistance of steel bars-reinforced specimens was researched. The ultrasonic sound, the mass loss rate, the electrical resistance, and the electrical resistance time history curves were determined to reflect the corrosion resistance of steel bars. The influence of NaCl freeze–thaw cycles and dry–wet alternations was considered. Results showed that the addition of RHA and WFA demonstrated a negative effect on the fluidity of fresh RPC. The fluidity of fresh RPC with WFA was lower. Moreover, RHA and WFA could effectively improve the mechanical strengths of hardened RPC, and the enhancing effect of RHA was higher. The increasing dosage of RHA could improve the corrosion resistance of steel bars in RPC when the specimens were exposed to the environment of NaCl freeze–thaw cycles and dry–wet alternations. However, when WFA was added, the effect was the opposite. The steel bars in RPC corroded more seriously when the specimens were exposed to the environment of NaCl dry–wet alternations than the environment of NaCl freeze–thaw cycles. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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14 pages, 5274 KiB

Open AccessArticle

Investigations on the Influence of Annealing on Microstructure and Mechanical Properties of Electrodeposited Ni-Mo and Ni-Mo-W Alloy Coatings

by Chao Zhang, Wudong Si, Yin Wang, Sichao Dai and Da Shu

Coatings 2021, 11(11), 1428; https://doi.org/10.3390/coatings11111428 - 22 Nov 2021

Cited by 13 | Viewed by 3346

Abstract

Ni-Mo and Ni-Mo-W coatings were electrodeposited on a stainless steel sheet, and then were annealed at 200, 400, and 600 °C. The effect of annealing heat treatment on the microstructure of Ni-Mo and Ni-Mo-W electrodepositions, their nano-hardness, and tribological properties were investigated. It [...] Read more.

Ni-Mo and Ni-Mo-W coatings were electrodeposited on a stainless steel sheet, and then were annealed at 200, 400, and 600 °C. The effect of annealing heat treatment on the microstructure of Ni-Mo and Ni-Mo-W electrodepositions, their nano-hardness, and tribological properties were investigated. It was revealed that the average crystalline are refined and phase separation are promoted with formation of Mo-W related intermetallic precipitates at temperature exceed 400 °C on account of the co-existence of Mo-W elements within Ni-Mo-W coatings. Annealing heat treatment leads to hardening, and the hardness and elastic module increase significantly. The grain boundary (GB) relaxation and hard precipitated intermetallic particles are responsible for the annealing-induced hardening for ≤400 °C annealed and 600 °C annealed Ni-Mo-W coatings, respectively. In addition, both adhesive wear and abrasive wear are observed for coatings, and abrasive wear becomes predominant when annealing temperature up to 600 °C. The wear resistance of coatings is improved eventually by formation of a mixture of lubricated oxides upon annealing at 600 °C and the enhancement of H/E ratio for ≤400 °C annealed Ni-Mo-W coatings. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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13 pages, 5100 KiB

Open AccessArticle

PLGA Coatings and PLGA Drug-Loading Coatings for Cardiac Stent Samples: Degradation Characteristics and Blood Compatibility

by Ziyang Jia, Chunyang Ma and Hongbin Zhang

Coatings 2021, 11(11), 1427; https://doi.org/10.3390/coatings11111427 - 22 Nov 2021

Cited by 13 | Viewed by 3845

Abstract

PLGA (Poly lactic-co-glycolic acid) and PLGA drug-loading coatings were prepared on 316 L stainless steel by electrostatic spray deposition (ESD). The surface morphology, three-dimensional morphology, and crystal structures of the coatings were observed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and [...] Read more.

PLGA (Poly lactic-co-glycolic acid) and PLGA drug-loading coatings were prepared on 316 L stainless steel by electrostatic spray deposition (ESD). The surface morphology, three-dimensional morphology, and crystal structures of the coatings were observed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Thermal properties, molecular weight, and coating composition were studied by differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and NMR. The degradation behaviors of the coatings were studied by mass changes, relative molecular mass and distributions, polymer compositions, thermal properties, and surface morphologies. The blood compatibilities of the coatings were investigated by platelet adhesion testing and dynamic coagulation times. SEM results indicated the drug-loading coating with 33% RAPA had the smoothest and most compact morphology. Addition of RAPA decreased the Tg of the PLGA coating, accompanied by partial crystallization that slowed the degradation rate of the drug-loaded coating. Microscopically, the morphology of the PLGA drug-loaded coating was coarser than the PLGA coating. The average surface roughness values of line and surface scannings were 16.232 nm and 39.538 nm, respectively. The surface of the drug-loading coating was micro uneven, and the macro smooth and micro multiphase separation structure helped improve its blood compatibility. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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15 pages, 2770 KiB

Open AccessArticle

A Porous Media Leakage Model of Contact Mechanical Seals Considering Surface Wettability

by Guangyao Bei, Chenbo Ma, Jianjun Sun, Xingya Ni and Yafei Ma

Coatings 2021, 11(11), 1338; https://doi.org/10.3390/coatings11111338 - 31 Oct 2021

Cited by 9 | Viewed by 2750

Abstract

The fluid leakage channel found in contact mechanical seals belongs to the microchannel category. Thus, upon further inspection, the influence of surface wettability and other factors neglected in previous studies becomes obvious. The porous leakage model of contact mechanical seals considering the surface [...] Read more.

The fluid leakage channel found in contact mechanical seals belongs to the microchannel category. Thus, upon further inspection, the influence of surface wettability and other factors neglected in previous studies becomes obvious. The porous leakage model of contact mechanical seals considering the surface wettability presented in this paper was based on the Cassie model and slip theory. The variations of the microchannel slip length and the velocity under various wettability conditions were studied and the relationship between the slip length and the apparent contact angle was established. Moreover, using porous media theory, the theoretical model of the leakage rate in contact mechanical seals considers the surface wettability depending on various parameters. The observed parameters included the surface contact angle, sealing medium pressure, viscosity coefficient, fractal dimension, and maximum pore diameter. The simulation results obtained using the proposed model have shown that the leakage rate increases with the increase of the apparent contact angle. Particularly when the contact pressure is small, the influence of the surface wettability is more significant. Furthermore, the leakage rate results obtained via the proposed model were compared to those of existing models. The comparison confirmed that the proposed model is applicable and that the necessity of considering wettability significantly affects the leakage rate calculation accuracy. The proposed model lays a foundation for further improving the calculation accuracy, making it easier for both the researchers and practitioners to suppress the leakage in contact mechanical seals. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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10 pages, 2521 KiB

Open AccessArticle

Investigations on the Adhesive Contact Behaviors between a Viscoelastic Stamp and a Transferred Element in Microtransfer Printing

by Ling Jiang, Mengjie Wu, Qiuping Yu, Yuxia Shan and Yuyan Zhang

Coatings 2021, 11(10), 1201; https://doi.org/10.3390/coatings11101201 - 30 Sep 2021

Cited by 10 | Viewed by 2961

Abstract

Microtransfer printing is a sophisticated technique for the heterogeneous integration of separately fabricated micro/nano-elements into functional systems by virtue of an elastomeric stamp. One important factor influencing the capability of this technique depends on the adhesion between the viscoelastic stamp and the transferred [...] Read more.

Microtransfer printing is a sophisticated technique for the heterogeneous integration of separately fabricated micro/nano-elements into functional systems by virtue of an elastomeric stamp. One important factor influencing the capability of this technique depends on the adhesion between the viscoelastic stamp and the transferred element. To provide theoretical guidance for the control of adhesion in the transfer printing process, a finite element model for the viscoelastic adhesive contact between a polydimethylsiloxane (PDMS) stamp and a spherical transferred element was established, in which the adhesive interaction was modeled by the Lennard-Jones surface force law. Effects of the unloading velocity, preload, and thermodynamic work of adhesion on the adhesion strength, characterized by the pull-off force, were examined for a loading-dwelling-unloading history. Simulation results showed that the unloading path deviated from the loading path due to the viscoelastic property of the PDMS stamp. The pull-off force increased with the unloading velocity, and the increasing ratio was large at first and then became low. Furthermore, the influence of the preload on increasing the pull-off force was more significant under larger unloading velocity than that under smaller unloading velocity. In addition, the pull-off force increased remarkably with the thermodynamic work of adhesion at a fixed maximum approach. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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16 pages, 1672 KiB

Open AccessArticle

Effect of Paint Process on the Performance of Modified Poplar Wood Antique

by Qingqing Liu, Di Gao and Wei Xu

Coatings 2021, 11(10), 1174; https://doi.org/10.3390/coatings11101174 - 28 Sep 2021

Cited by 34 | Viewed by 2617

Abstract

Modified poplar wood is used as the substrate, based on the surface coating process and actual operation requirements of European and American furniture, and the painting process is studied. Four different paint coating methods are applied to modified poplar wood that has undergone [...] Read more.

Modified poplar wood is used as the substrate, based on the surface coating process and actual operation requirements of European and American furniture, and the painting process is studied. Four different paint coating methods are applied to modified poplar wood that has undergone different surface pretreatments. The gloss and adhesion of the coating system were measured. The difference in paint film performance of different paint finishes on the modified poplar with different surface pretreatments was discussed. The reasons were analyzed to establish the corresponding relationship between wood surface performance and paint film performance and obtain the best coating process parameters. The number of passes of nitrocellulose (NC) transparent primer was appropriately increasing, and the adhesion of the overall paint film was improved through the bonding between the films after sanding. NC transparent primer has the function of weakening the surface gloss. NC transparent topcoat has the effect of improving gloss. The proper use of PU sealing primer is beneficial to improve the gloss of the paint film, but excessive use will not produce any effect. The paint process of Group C is more suitable for the antique, old-fashioned process of European and American furniture from the perspective of the glossiness of the paint film. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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10 pages, 6148 KiB

Open AccessArticle

Characterization of MAO + Cu Composite Coatings on Aluminum Alloy

by Shang-Kun Wu, Wei Yang, Wei Gao, Yu-Hong Yao, Yong Zhang and Jian Chen

Coatings 2021, 11(10), 1172; https://doi.org/10.3390/coatings11101172 - 28 Sep 2021

Cited by 7 | Viewed by 2620

Abstract

Novel composite coatings were fabricated on 6061 aluminum alloy substrates by two steps combining micro-arc oxidation (MAO) plus electroless copper plating (Cu). Different MAO + Cu composite coatings were compared. Cu continuously and evenly covered an aluminum oxide surface during processing thus changing [...] Read more.

Novel composite coatings were fabricated on 6061 aluminum alloy substrates by two steps combining micro-arc oxidation (MAO) plus electroless copper plating (Cu). Different MAO + Cu composite coatings were compared. Cu continuously and evenly covered an aluminum oxide surface during processing thus changing the surface topography. The adhesion of MAO + Cu composite coating was tested by the pull-out method. The best adhesion strength of the composite coating can reach industrial requirements. The effects of the composite coatings on friction were investigated using a ball-on-disc test method. It is found that copper in composite coatings plays a lubricating effect during the wear process under dry sliding. Furthermore, the mechanisms by which the observed advantages were produced are discussed. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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12 pages, 7127 KiB

Open AccessArticle

Effect of SiC Particle Contents and Size on the Microstructure and Dissolution of SiC-Hydroxyapatite Coatings

by Li Yang and Zuli Mao

Coatings 2021, 11(10), 1166; https://doi.org/10.3390/coatings11101166 - 27 Sep 2021

Cited by 4 | Viewed by 2037

Abstract

Carbon/carbon composites, when used as bone implant materials, do not adhere well to the bone tissues because of their non-bioactive characteristics. Therefore, we electro-deposited SiC-hydroxyapatite coatings (with an ultrasound-assisted step) on carbon/carbon composites. We analyzed how the content and size of the SiC [...] Read more.

Carbon/carbon composites, when used as bone implant materials, do not adhere well to the bone tissues because of their non-bioactive characteristics. Therefore, we electro-deposited SiC-hydroxyapatite coatings (with an ultrasound-assisted step) on carbon/carbon composites. We analyzed how the content and size of the SiC particles affected the structure, morphology, bonding strength and dissolution of the SiC-hydroxyapatite coatings. The hydroxyapatite coating dissolution properties were assessed by the released Ca²⁺ and the weight loss. The SiC-hydroxyapatite coating on naked carbon/carbon composites showed a more compact microstructure in comparison to the hydroxyapatite coating on carbon/carbon composites. The reasons for the changes in the microstructure and the improvement in the adhesion of the coatings on C/C were discussed. Moreover, the addition of SiC particles increased the binding strengths of the hydroxyapatite coating on C/C composite, as well as reduced the dissolution rate of the hydroxyapatite coating. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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11 pages, 4889 KiB

Open AccessArticle

Preparation of High-Efficiency Flame-Retardant and Superhydrophobic Cotton Fabric by a Multi-Step Dipping

by Jingda Huang, Mengmeng Li, Changying Ren, Wentao Huang, Qiang Wu, Qian Li, Wenbiao Zhang and Siqun Wang

Coatings 2021, 11(10), 1147; https://doi.org/10.3390/coatings11101147 - 22 Sep 2021

Cited by 13 | Viewed by 3305

Abstract

Cotton fabric, as an important material, is suffering from some defects such as flammability, easy pollution and so on; therefore, it is important to make a flame-retardant and superhydrophobic modification on cotton fabric. In this study, we demonstrated a preparation of high-efficiency flame-retardant [...] Read more.

Cotton fabric, as an important material, is suffering from some defects such as flammability, easy pollution and so on; therefore, it is important to make a flame-retardant and superhydrophobic modification on cotton fabric. In this study, we demonstrated a preparation of high-efficiency flame-retardant and superhydrophobic cotton fabric with double coated construction by a simple multi-step dipping. First, the fabric was immersed in branched poly(ethylenimine) (BPEI) and ammonium polyphosphate (APP) water dispersions successively, and then immersed in polydimethylsiloxane (PDMS)/cellulose nanocrystals (CNC)-SiO₂ toluene dispersion to form a BPEI/APP/PDMS/CNC-SiO₂ (BAPC) composite coating on the surface of the cotton fabric. Here, the hydrophobic modified CNC-SiO₂ rods were used to construct the superhydrophobic layer and the BPEI/APP mixture was used as the flame-retardant layer, as well as SiO₂ particles which could further improve the flame-retardant effect. PDMS was mainly used as an adhesive between the BPEI/APP layer and the CNC-SiO₂ layer. The resulting cotton fabric shows outstanding flame-retardant properties, in that the value of oxygen index meter (LOI) reaches 69.8, as well as excellent superhydrophobicity, in that the water contact angle (WCA) is up to 156.6°. Meanwhile, there is a good abrasion resistance, the superhydrophobicity is not lost until the 16th abrasion cycles and the flame retardant retains well, even after 100 abrasion cycles in an automatic vertical flammability cabinet under a pressure of 8.8 kPa. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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9 pages, 1820 KiB

Open AccessArticle

Effect of Nitrogen Flow Ratio on Degradation Behaviors and Failure of Magnetron Sputter Deposited Tantalum Nitride

by Zhigang Li, Yubao Zhang, Yi Wang, Jinfeng Li and Hongtao Zhao

Coatings 2021, 11(9), 1133; https://doi.org/10.3390/coatings11091133 - 17 Sep 2021

Cited by 17 | Viewed by 3175

Abstract

A series of Tantalum Nitride (TaN) films under a reactive direct current magnetron sputtering method with a controlled total gas flow rate were prepared on aluminum oxide substrates. To find the nitrogen flow rate, which produced the minimum sheet resistance, TaN films deposited [...] Read more.

A series of Tantalum Nitride (TaN) films under a reactive direct current magnetron sputtering method with a controlled total gas flow rate were prepared on aluminum oxide substrates. To find the nitrogen flow rate, which produced the minimum sheet resistance, TaN films deposited under a nitrogen gas flow ratio of 2.5%, 5%, 10%, 15%, 20%, 25% were characterized in terms of their structural and electrical properties. The optimum total gas flow rate was 60 sccm, revealing the lowest deviation of sheet resistance. Next, the durability and reliability at high temperatures, after heating and cooling cycles and exposure to the induced current, were tested. When the nitrogen flow ratio reaches 2.5%, it gets the maximum for the adhesion force, roughness, and deposition rate of the TaN film, and maximum values are 75.4 N, 1.1 nm, and 3.67 nm/min, respectively, and the sheet resistance of the TaN film reaches a minimum of 20.32 Ω/sq. The degradation behaviors and failure of TaN films were investigated by measuring the sheet resistance variation. To further explain the degradation of TaN films, additional analysis of their crystallinity was conducted. The results showed that TaN-based thin film resistors have high durability and reliability, and are suitable for embedded passive resistors. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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13 pages, 1243 KiB

Open AccessArticle

Preparation and Characterization of Functional Films Based on Chitosan and Corn Starch Incorporated Tea Polyphenols

by Lepeng Gao, Tao Zhu, Fuyang He, Zhiqiang Ou, Jian Xu and Lili Ren

Coatings 2021, 11(7), 817; https://doi.org/10.3390/coatings11070817 - 6 Jul 2021

Cited by 40 | Viewed by 5149

Abstract

The functional films based on chitosan and corn starch incorporated tea polyphenols were developed through mixing the chitosan and starch solution and the powder of tea polyphenols by the casting method. The objective of this research was to investigate the effect of different [...] Read more.

The functional films based on chitosan and corn starch incorporated tea polyphenols were developed through mixing the chitosan and starch solution and the powder of tea polyphenols by the casting method. The objective of this research was to investigate the effect of different concentrations of tea polyphenols on the functional properties of the films. Attenuated total reflectance Fourier transform infrared spectrometry and X-ray diffraction were used to investigate the potential interactions among chitosan, corn starch and tea polyphenols in the blend films. Physical properties of the blend films, including density, moisture content, opacity, color, water solubility and water swelling, as well as morphological characteristics, were measured. The results demonstrated that the incorporation of tea polyphenols caused the blend films to lead to a darker appearance. The water solubility of the blend film increased with the increase of tea polyphenol concentrations, while moisture content and swelling degree decreased. The hydrogen bonding between chitosan, starch and tea polyphenols restricted the movement of molecular chains and was helpful to the stability of the blend films. The results suggested that these biodegradable blend films could potentially be used as packaging films for the food and drug industries to extend the shelf life to maintain their quality and safety. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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12 pages, 2978 KiB

Open AccessFeature PaperArticle

Indoor and Outdoor Performance Study of Metallic Zinc Particles in Black Paint to Improve Solar Absorption for Solar Still Application

by Muhammad Shakeel Ahmad, Shwe Sin Han, Amad Zafar, Usman Ghafoor, Nasrudin Abd Rahim, Muhammad Umair Ali and You Seung Rim

Coatings 2021, 11(5), 536; https://doi.org/10.3390/coatings11050536 - 30 Apr 2021

Cited by 10 | Viewed by 2801

Abstract

In this study, the effects of metallic zinc (Zn) particles were studied to increase surface temperature on a solar-still absorber, which is a major component of increased production. Various concentrations of Zn particles were mixed in black paint and applied to the absorber [...] Read more.

In this study, the effects of metallic zinc (Zn) particles were studied to increase surface temperature on a solar-still absorber, which is a major component of increased production. Various concentrations of Zn particles were mixed in black paint and applied to the absorber plate. SEM and XRD were used to examine and confirm the surface morphology and phase identification of as-received powder. UV-Vis spectroscopy was used to examine light-absorption properties. Finally, extensive indoor testing (using an improvised solar emulator) and outdoor testing were conducted to optimize the concentration. The specimens containing 10 wt% Zn in black paint showed the highest increase in temperature, i.e., 103.53 °C in indoor conditions at 1000 W/m² irradiation, which is 59.17% higher than a bare aluminum plate and 17.57% higher than an only black-paint-coated aluminum plate. On the other hand, specimens containing 10 wt% Zn reached just 87.53 °C, compared to 80.00 °C for an only black-paint-coated aluminum plate and 60.62 °C for bare aluminum. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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Review

Jump to: Research

25 pages, 4532 KiB

Open AccessReview

A Past, Present, and Prospective Review on Microwave Nondestructive Evaluation of Composite Coatings

by Teng Wei Siang, Muhammad Firdaus Akbar, Ghassan Nihad Jawad, Tan Shin Yee and Mohd Ilyas Sobirin Mohd Sazali

Coatings 2021, 11(8), 913; https://doi.org/10.3390/coatings11080913 - 30 Jul 2021

Cited by 28 | Viewed by 4441

Abstract

Recent years have witnessed an increase in the use of composite coatings for numerous applications, including aerospace, aircraft, and maritime vessels. These materials owe this popularity surge to the superior strength, weight, stiffness, and electrical insulation they exhibit over conventional substances, such as [...] Read more.

Recent years have witnessed an increase in the use of composite coatings for numerous applications, including aerospace, aircraft, and maritime vessels. These materials owe this popularity surge to the superior strength, weight, stiffness, and electrical insulation they exhibit over conventional substances, such as metals. The growing demand for such materials is accompanied by the inevitable need for fast, accurate, and affordable nondestructive testing techniques to reveal any possible defects within the coatings or any defects under coating. However, typical nondestructive testing (NDT) techniques such as ultrasonic testing (UT), infrared thermography (IRT), eddy current testing (ECT), and laser shearography (LS) have failed to provide successful results when inspecting composite coatings. Consequently, microwave NDT techniques have emerged to compensate for the shortcomings of traditional NDT approaches. Numerous microwave NDT methods have been reported for composite coatings inspection. Although existing microwave NDT methods have shown successful inspection of composite coatings, they often face several challenges, such as low spatial image quality and extensive data interpretation. Nevertheless, many of these limitations can be addressed by utilizing microwave NDT techniques with modern technologies such as soft computing. Artificially intelligent techniques have greatly enhanced the reliability and accuracy of microwave NDT techniques. This paper reviews various traditional NDT techniques and their limitations in inspecting composite coatings. In addition, the article includes a detailed review of several microwave NDT techniques and their benefits in evaluating composite coatings. The paper also highlights the advantages of using the recently reported microwave NDT approaches employing artificial intelligence approaches. This review demonstrates that microwave NDT techniques in conjunction with artificial intelligence approaches have excellent prospects for further enhancing composite coatings inspection and assessment efficiency. The review aimed to provide the reader with a comprehensive overview of most NDT techniques used for composite materials alongside their most salient features. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

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