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20 pages, 12204 KiB

Open AccessArticle

Verification of the Non-Axisymmetric Deformation Mechanism of Bearing Rings after Quenched in a Multi-Field Coupled Simulation

by Qian Liu, Dongying Ju, Xusheng Li, Kousuke Ishikawa, Rui Lv, Weifeng Lian and Min Zhang

Coatings 2022, 12(5), 676; https://doi.org/10.3390/coatings12050676 - 15 May 2022

Cited by 3 | Viewed by 1348

Abstract

In this paper, the elliptical deformation mechanism of the bearing ring after quenching has been studied by using the theory of “metal-thermal-mechanical” and the multi-field coupling simulation method. It has been mainly considered that it occurred as an experimental phenomenon in the past [...] Read more.

In this paper, the elliptical deformation mechanism of the bearing ring after quenching has been studied by using the theory of “metal-thermal-mechanical” and the multi-field coupling simulation method. It has been mainly considered that it occurred as an experimental phenomenon in the past that, when the bearing ring had been oil quenched, a vapor film had usually formed on its surface, and the breakage and boiling of the vapor film had been observed to be uneven in a circumferential direction. For this reason, based on the phase transition kinetics, several types of heat transfer boundary conditions on the outer surface of bearing rings during oil quenching have been assumed, and the multi-field coupled simulation of the quenching process of bearing rings has been carried out in this paper. According to the simulation results, it could be concluded that when two different heat transfer boundary conditions have been set on the outer surface of the bearing outer ring in the form of orthogonal symmetry, the quenched bearing outer ring would produce elliptical deformation. The above simulation results have been basically verified by comparing the experimental results. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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12 pages, 4452 KiB

Open AccessArticle

Study on AgCl/Al₂O₃ Catalyst Coating on Metal Workpiece Surface by Electrophoretic Deposition and Its Overall Catalytic Performance

by Yimin Yu, Yunlong Ding and Dongying Ju

Coatings 2022, 12(5), 553; https://doi.org/10.3390/coatings12050553 - 20 Apr 2022

Viewed by 1499

Abstract

This paper is a study of the coating technique of AgCl/Al₂O₃ catalyst on metal-based surfaces. In order to remove nitrogen oxides from the exhaust of marine diesel engines, this paper proposes a method of electrophoretic deposition and designs an electrophoretic [...] Read more.

This paper is a study of the coating technique of AgCl/Al₂O₃ catalyst on metal-based surfaces. In order to remove nitrogen oxides from the exhaust of marine diesel engines, this paper proposes a method of electrophoretic deposition and designs an electrophoretic deposition apparatus according to the coating conditions. An in-house developed catalyst was coated on a specific stainless-steel workpiece by the electrophoretic deposition method under the conditions of appropriate voltage and catalyst solution concentration. The surface and cross section of AgCl/Al₂O₃ coating on stainless steel were observed by scanning electron microscope, and the thickness of catalyst coating after coating was determined. In this study, an exhaust gas evaluation system was built, and a removal test of nitrogen oxides from diesel exhaust gas was conducted under the environment of temperature cyclic change, and repeated experiments proved that the coated workpiece could still effectively remove harmful nitrogen oxides from the exhaust gas. Converting them to N₂ provides a new idea for ship exhaust gas purification. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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14 pages, 6192 KiB

Open AccessArticle

Effect of Transformation Plasticity on Gear Distortion and Residual Stresses in Carburizing Quenching Simulation

by Xusheng Li, Dongying Ju, Jianting Cao, Sirui Wang, Yong Chen, Fangbo He and Hui Li

Coatings 2021, 11(10), 1224; https://doi.org/10.3390/coatings11101224 - 09 Oct 2021

Cited by 6 | Viewed by 1923

Abstract

This paper addresses the effect of gear steel on distortion and residual stresses due to phase transformation in carburizing and quenching. In particular, the martensitic and bainitic phase transformation expansion and transformation plasticity properties of two automotive gearbox steels (20CrMnTiH and 20MnCr5) and [...] Read more.

This paper addresses the effect of gear steel on distortion and residual stresses due to phase transformation in carburizing and quenching. In particular, the martensitic and bainitic phase transformation expansion and transformation plasticity properties of two automotive gearbox steels (20CrMnTiH and 20MnCr5) and their physical parameters are measured by experiments of transformation plasticity properties. Numerical simulations of the actual carburizing and quenching process of the gearbox spline helical gears were carried out in combination with the thermal and mechanical properties with temperature variations calculated by the material design software JMAT-Pro. In particular, the phase transformation properties of the two materials and their influence on the distortion and residual stresses after carburizing and quenching were verified by experiments of transformation plasticity and numerical simulations. A reliable basis is provided for predicting the distortion mechanism of gear steels in carburizing and quenching. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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13 pages, 3937 KiB

Open AccessArticle

Electrochemical Dechlorination of 3-chlorophenol with Palladium-Loaded Carbon Felt Electrode

by Di Li, Siqi Zhang, Yingjia Chen, Haiming Yang, Xin Geng, Suying Zhao, Jiajun Li and Lixiang Li

Coatings 2021, 11(10), 1188; https://doi.org/10.3390/coatings11101188 - 29 Sep 2021

Cited by 1 | Viewed by 1641

Abstract

Electrochemical dechlorination with Pd-loaded electrodes offers an effective method for detoxification of wastewater. Electro-reductive dechlorination of 3-chlorophenol (3-CP) with Pd loaded on carbon felt (Pd/CF) was investigated. Pd was loaded on carbon felt by electrolytic method. The prepared electrodes were characterized by XRD, [...] Read more.

Electrochemical dechlorination with Pd-loaded electrodes offers an effective method for detoxification of wastewater. Electro-reductive dechlorination of 3-chlorophenol (3-CP) with Pd loaded on carbon felt (Pd/CF) was investigated. Pd was loaded on carbon felt by electrolytic method. The prepared electrodes were characterized by XRD, SEM, EDS, S-TEM and CV. The sizes of the Pd particles loaded on CF were found in the range of 100–400 nm. The preparing conditions including loading amount of Pd and loading currents were investigated. Moreover, the reduction conditions including electrolytes, reductive currents and recycle times were also studied. The Pd/CF cathodes with Pd loading of 0.5 mg/cm², preparing current of 5 mA, electrolyte concentration of 30 mmol/L NaCl and 30 mmol/L CH₃COONa were used to reduce 3-CP for dechlorination. When CH₃COONa was used as the electrolyte, the current was 5 mA, the initial pH was 7.5, the initial 3-CP concentration was 1 mmol/L and the degradation rate of 3-CP could reach 95.81% after reduction of 150 min under an argon atmosphere. The electrochemical reduction of 3-CP was confirmed to follow the first-order rate law. 3-CP was qualitatively dechlorinated to phenol on electrodes with Pd. The fact that active hydrogen formed on palladium during preliminary electrolysis could be proved by the dechlorinated 3-CP in non-electroreduction after preliminary electrolysis. A possible reduction pathway was proposed based on the results. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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16 pages, 6585 KiB

Open AccessFeature PaperArticle

Mathematical Simulation and Experimental Verification of Carburizing Quenching Process Based on Multi-Field Coupling

by Jiangang Wang, Shuai Yang, Jianhui Li, Dongying Ju, Xusheng Li, Fangbo He, Hui Li and Yong Chen

Coatings 2021, 11(9), 1132; https://doi.org/10.3390/coatings11091132 - 17 Sep 2021

Cited by 5 | Viewed by 2215

Abstract

Based on the multi-field coupling effect of temperature, diffusion, and phase change, the finite element model of carburizing and quenching was established. The 20CrMnTiH steel helical gear as the research object, prediction accuracy of carburizing, and quenching model of complex helical gear was [...] Read more.

Based on the multi-field coupling effect of temperature, diffusion, and phase change, the finite element model of carburizing and quenching was established. The 20CrMnTiH steel helical gear as the research object, prediction accuracy of carburizing, and quenching model of complex helical gear was studied. The material properties database of experimental steel was established by JMatPro, and the material thermophysical parameters needed in the calculation process were obtained. The carburizing and quenching process of transmission helical gear was numerically simulated by thermodynamic three-dimensional coupling analysis method combined with actual heat treatment process. The microstructure morphology, macro hardness, and deformation were characterized. The experimental results show that the microstructure of the hardened surface layer was acicular martensite and a small amount of residual austenite. The highest hardness appears at the surface layer of 778.8 HV, the effective hardened layer depth was 0.9 mm, and the maximum deformation of the gear was 0.055 mm. By comparing the experimental measurement results with the simulation results, they were in good agreement, which verifies the accuracy of the finite element model. This indicates that the model has good prediction ability in carburizing and quenching process. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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12 pages, 2388 KiB

Open AccessArticle

Comparative Study on Transmission Performance of Manganese Phosphate Coated Gears

by Guangxin Li, Yong Chen, Libin Zang, Rui Liu, Dongying Ju, Yimin Wu and Yanjun Tan

Coatings 2021, 11(9), 1026; https://doi.org/10.3390/coatings11091026 - 26 Aug 2021

Cited by 1 | Viewed by 1953

Abstract

As an important part of transmission systems, coatings can improve the physical properties of gear surface. It is meaningful to research the effect of coating on the transmission performance of gears. In this paper, eight-degree-of-freedom dynamic response model of helical cylindrical gear is [...] Read more.

As an important part of transmission systems, coatings can improve the physical properties of gear surface. It is meaningful to research the effect of coating on the transmission performance of gears. In this paper, eight-degree-of-freedom dynamic response model of helical cylindrical gear is established considering friction, and the influence of friction factors on dynamic response is explored. The tribological properties and lubrication characteristics of the coating are investigated and compared with uncoated. The transmission performances of manganese phosphate conversion coated gears are studied experimentally. The results show that the coefficients of friction of Mn–P[C] coatings are reduced by 19%, the average amplitude and root mean square of vibration acceleration are obviously decreased, and the transmission efficiency is improved. The manganese phosphate conversion coating is beneficial to the transmission performance of gears. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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15 pages, 4222 KiB

Open AccessArticle

Modeling and Simulation of Vacuum Low Pressure Carburizing Process in Gear Steel

by Jingyu Guo, Xiaohu Deng, Huizhen Wang, Leyu Zhou, Yueming Xu and Dongying Ju

Coatings 2021, 11(8), 1003; https://doi.org/10.3390/coatings11081003 - 23 Aug 2021

Cited by 11 | Viewed by 3970

Abstract

A combination of simulation and experimental approaches to optimize the vacuum carburizing process is necessary to replace the costly experimental trial-and-error method in time and resources. In order to accurately predict the microstructure evolution and mechanical properties of the vacuum carburizing process, a [...] Read more.

A combination of simulation and experimental approaches to optimize the vacuum carburizing process is necessary to replace the costly experimental trial-and-error method in time and resources. In order to accurately predict the microstructure evolution and mechanical properties of the vacuum carburizing process, a multi-field multi-scale coupled model considering the interaction of temperature, diffusion, phase transformation, and stress was established. Meanwhile, the improved model is combined with the heat treatment software COSMAP to realize the simulation of the low-pressure vacuum carburizing process. The low-pressure vacuum carburizing process of 20CrMo gear steel was simulated by COSMAP and compared with the experimental results to verify the model. The results indicated that the model could quantitatively obtain the carbon concentration distribution, Fe-C phase fraction, and hardness distribution. It can be found that the carbon content gradually decreased from the surface to the center. The surface carbon concentration is relatively high only after the carburizing stage. With the increase in diffusion time, the surface carbon concentration decreases, and the carburized layer depth increases. The simulated surface carbon concentration results and experimental results are in good agreement. However, there is an error between calculations and observations for the depth of the carburized layer. The error between simulation and experiment of the depth of carburized layer is less than 6%. The simulated surface hardness is 34 HV lower than the experimental surface hardness. The error of surface hardness is less than 5%, which indicates that the simulation results are reliable. Furthermore, vacuum carburizing processes with different diffusion times were simulated to achieve the carburizing target under specific requirements. The results demonstrated that the optimum process parameters are a carburizing time of 42 min and a diffusion time of 105 min. This provides reference and guidance for the development and optimization of the vacuum carburizing process. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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11 pages, 13621 KiB

Open AccessArticle

Study on Laser Surface Hardening Behavior of 42CrMo Press Brake Die

by Huizhen Wang, Yuewen Zhai, Leyu Zhou and Zibo Zhang

Coatings 2021, 11(8), 997; https://doi.org/10.3390/coatings11080997 - 21 Aug 2021

Cited by 4 | Viewed by 2019

Abstract

Laser surface hardening is a promising surface technology to enhance the properties of surfaces. This technology was used on the 42CrMo press brake die. Its hardening behavior was investigated by using scanning electron microscopy and electron backscattering diffraction. The results indicated that the [...] Read more.

Laser surface hardening is a promising surface technology to enhance the properties of surfaces. This technology was used on the 42CrMo press brake die. Its hardening behavior was investigated by using scanning electron microscopy and electron backscattering diffraction. The results indicated that the martensite in the hardening zone was significantly finer than that in the substrate. There were many low-angle grain boundaries in the martensite of the hardening zone, and the kernel average misorientation and grain orientation spread in the hardening zone grains were obviously greater, which further improved the hardness of the hardening zone, especially near the substrate. The microstructure and the properties of the blade maintained excellent uniformity with treatment by single-pass laser surface hardening with a spot size of 2 mm, scanning speed of 1800 mm/min, and power of 2200 W. The hardness of the hardening zone was 1.6 times higher than that of the base material, and the thickness of the hardening zone reached 1.05 mm. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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10 pages, 1609 KiB

Open AccessArticle

Effect of Vacuum Annealing on Microstructure and Hot-Salt Corrosion Behavior of CoNiCrAlY/YSZ/LaMgAl₁₁O₁₉ Double-Ceramic Coating

by Guanming Xue, Yingchao Sun, Ling Xiang, Zhiguo Wang, Suying Hu and Zhiwen Xie

Coatings 2021, 11(8), 951; https://doi.org/10.3390/coatings11080951 - 09 Aug 2021

Cited by 3 | Viewed by 1649

Abstract

This study investigated the potential effect of vacuum annealing on the microstructure and hot salt corrosion behavior of CoNiCrAlY/YSZ/LaMgAl₁₁O₁₉ (LMA) double-ceramic coatings. A hot-salt corrosion test revealed that sprayed coatings exhibited an unsatisfactory anti-corrosion performance, and the LMA layer underwent [...] Read more.

This study investigated the potential effect of vacuum annealing on the microstructure and hot salt corrosion behavior of CoNiCrAlY/YSZ/LaMgAl₁₁O₁₉ (LMA) double-ceramic coatings. A hot-salt corrosion test revealed that sprayed coatings exhibited an unsatisfactory anti-corrosion performance, and the LMA layer underwent severe fracture and corrosion degradation. Vacuum annealing induced a prominent recrystallization of the amorphous phase in LMA layer, triggering severe volume shrinkage and microcrack initiation. The recrystallization and volume shrinkage of the LMA layer were aggravated by an increase in the annealing temperature. The annealed coating with a higher fraction of the LaMA phase showed superior resistance to hot-salt corrosion. However, the salt mixture diffused simultaneously along the microcracks and eventually eroded into the YSZ layer. These results confirmed that vacuum annealing significantly enhanced the hot-salt corrosion resistance of the LMA layer. However, it deteriorated the barrier effect of the salt mixture through microcrack formation. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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13 pages, 8731 KiB

Open AccessArticle

Structural Evaluation of Coal-Tar-Pitch-Based Carbon Materials and Their Na⁺ Storage Properties

by Ruilin Yin, Kun Wang, Beibei Han, Guiying Xu, Lixiang Li, Baigang An, Dongying Ju, Maorong Chai, Songnan Li and Weimin Zhou

Coatings 2021, 11(8), 948; https://doi.org/10.3390/coatings11080948 - 08 Aug 2021

Cited by 10 | Viewed by 3346

Abstract

Linking to the S element hybrid strategies, S-doped carbon materials having different macrostructures and defect concentrations are prepared by using sulfur and coal-tar-pitch as raw materials in a carbonization temperature range of 700–1000 °C. The evaluations of macrostructure and surface characteristics are performed [...] Read more.

Linking to the S element hybrid strategies, S-doped carbon materials having different macrostructures and defect concentrations are prepared by using sulfur and coal-tar-pitch as raw materials in a carbonization temperature range of 700–1000 °C. The evaluations of macrostructure and surface characteristics are performed through XRD, TEM, Raman and XPS measurements. Through the linear fitting among the Na⁺ storage capacity with I_D/I_G and d₀₀₂ values, the correlations of Na⁺ storage capacity with macrostructures and defects are respectively investigated in detail. It is observed that S-doped carbon materials exhibit storage capacity at 120 mAh/g after the charge-discharge is being carried out 2000 cycles at 2.0 A/g. Studies have shown that adsorptions of introduced defects on graphene-like carbon sheets mainly play the role to enhance the storage capacity, and the expanded carbonaceous lamellar spaces of highly disordered and pseudo-graphitic macrostructures provide the channels for fast transfer of Na⁺. Our studies are able to provide references for designs and fabrications of coal tar pitch based soft carbon materials as sodium-ion batteries (SIBs) anodes when using heteroatoms doping methods. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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9 pages, 5319 KiB

Open AccessArticle

Preparation and Characterization of (Al, Fe) Codoped ZnO Films Prepared by Sol–Gel

by Jiangang Wang, Wenjing Shen, Xin Zhang, Jianhui Li and Jing Ma

Coatings 2021, 11(8), 946; https://doi.org/10.3390/coatings11080946 - 08 Aug 2021

Cited by 3 | Viewed by 1819

Abstract

In this research, Al-doped and (Al, Fe) codoped ZnO films were prepared on glass substrate by the sol–gel method. The surface morphology, structure, and optical property were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Ultraviolet-Visible-Near-infrared (UV-Vis-NIR) [...] Read more.

In this research, Al-doped and (Al, Fe) codoped ZnO films were prepared on glass substrate by the sol–gel method. The surface morphology, structure, and optical property were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Ultraviolet-Visible-Near-infrared (UV-Vis-NIR) spectroscopy. The film surface morphologies all exhibited granular characteristics. With the Fe doping concentration increasing, the codoped films had smaller grain size and tended to be smoother. XRD analysis revealed that all films had a hexagonal wurtzite structure. The codoping can contribute to more Al and Fe ions entering the ZnO crystal structure, but result in the crystalline degree of the films decreasing. XPS results showed that the Al and Fe irons in the films exist in the form of trivalent. Moreover, the doped films had higher transmission, especially for codoped (Fe:Al = 3) film, but their absorption edge shifted to the short-wavelength direction. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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11 pages, 2868 KiB

Open AccessArticle

Electrochemical Properties of LiNi_0.6Co_0.2Mn_0.2O₂ Cathode Materials Prepared with Different Ammonia Content

by Chen Xu, Siqi Guan, Lixiang Li, Chengguo Sun, Baigang An and Xin Geng

Coatings 2021, 11(8), 932; https://doi.org/10.3390/coatings11080932 - 04 Aug 2021

Cited by 7 | Viewed by 2477

Abstract

The content of ammonia coordination agent in initial aqueous solution is one of important factors which greatly influences the morphologies and electrochemical performances of layered LiNi₆Mn₂Co₂O₂ (NCM622). The spherical morphologies, contributing to higher specific capacity of [...] Read more.

The content of ammonia coordination agent in initial aqueous solution is one of important factors which greatly influences the morphologies and electrochemical performances of layered LiNi₆Mn₂Co₂O₂ (NCM622). The spherical morphologies, contributing to higher specific capacity of NCM622, ascribe to the same precipitation rate of transition metal ions (Ni²⁺, Co²⁺, Mn²⁺) during co-precipitation. Hence, the effects of different amounts of ammonia in initial solution on the hydroxide equilibrium constant and properties of NCM622 were discussed. With the ammonia content of 70 mL, the spherical morphology with more perfect layered structure and higher discharge capacity are obtained. The necessity of ammonia content in initial solution are also demonstrated from electrochemical performances of NCM622, such as the initial discharge capacity of 199.8 mAh g⁻¹ at 0.1 C, the specific capacity of 150.0 mAh g⁻¹ after 100th cycles, and the capacity retention rate of 89.6% at 3 C. If other metal ions are anticipated to be chemically doped with NCM622, the hydroxide equilibrium constant and precipitation rate need to be considered. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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11 pages, 4199 KiB

Open AccessArticle

Fabrication of a Novel MgO-B₂O₃-SiO₂-Zn Coating by Thermal Spraying

by Zhan Yu, Bo Song, Ping Ma, Wenhui Fan, Enzhong Gong, Yilun Sun, Yunlong Ding and Dongying Ju

Coatings 2021, 11(8), 907; https://doi.org/10.3390/coatings11080907 - 29 Jul 2021

Cited by 2 | Viewed by 1689

Abstract

In automotive technology, the proper use of thermal insulation materials helps improve the performance and life of internal equipment and reduce maintenance cost. In this study, plasma spraying and flame spraying are used to prepare and coat a new MgO-B₂O₃ [...] Read more.

In automotive technology, the proper use of thermal insulation materials helps improve the performance and life of internal equipment and reduce maintenance cost. In this study, plasma spraying and flame spraying are used to prepare and coat a new MgO-B₂O₃-SiO₂-Zn powder on the SUS304 substrate. The resulting coating as thermal insulation layer formed a networked microstructure between the substrates to improve the thermal insulation performance of the material. By validation of thermal radiation experiments, the thermal insulation effects of various ceramic powders were compared, the high-temperature and low-temperature thermal insulation materials for about 300 and 100 °C were determined, and the thermal insulation performance of the constructed material coatings was verified by analysis. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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12 pages, 5025 KiB

Open AccessArticle

Effect of Mullite Film Layers on the High-Temperature Oxidation Resistance of AISI 304 Stainless Steel

by Jing Ma, Ning Wen, Ruiyang Wang, Jiangang Wang, Xin Zhang, Jianhui Li and Yiqing Chen

Coatings 2021, 11(8), 880; https://doi.org/10.3390/coatings11080880 - 23 Jul 2021

Cited by 3 | Viewed by 1792

Abstract

Protective coating is an effective way to extend materials’ high-temperature service life. In order to improve the high-temperature oxidation resistance of AISI 304 stainless steel, mullite films with different layers were successfully prepared by the sol-gel method and the sintering process on the [...] Read more.

Protective coating is an effective way to extend materials’ high-temperature service life. In order to improve the high-temperature oxidation resistance of AISI 304 stainless steel, mullite films with different layers were successfully prepared by the sol-gel method and the sintering process on the surface of stainless steel. The effect of the film layers on the high-temperature oxidation resistance of stainless steel at 900 °C for 100 h was studied. The analysis results of oxidation kinetics, X-rays diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis (EDS) show that Al_1.4Si_0.3O_2.7 mullite film effectively improved the high-temperature oxidation resistance of stainless steel. The sample with three-layer mullite film has the best high-temperature oxidation resistance. The mass gain and oxidation spalling mass are only 4.6% and 34.5% of those of the uncoated sample after 100 h cyclic oxidation at 900 °C. A chromium oxide layer was formed at the interface of mullite film and the substrate during the sintering process. The generation of selective Cr₂O₃ scale was promoted at the cyclic oxidation stage so that the sample with three-layers has excellent high-temperature oxidation resistance. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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16 pages, 6532 KiB

Open AccessArticle

Chemical Composition and Corrosion Behavior of a-C:H/DLC Film-Coated Titanium Substrate in Simulated PEMFC Environment

by Beibei Han, Mengyuan Yan, Dongying Ju, Maorong Chai and Susumu Sato

Coatings 2021, 11(7), 820; https://doi.org/10.3390/coatings11070820 - 07 Jul 2021

Cited by 4 | Viewed by 2607

Abstract

The amorphous hydrogenated (a-C:H) film-coated titanium, using different CH₄/H₂ and deposition times, was prepared by the ion beam deposition (IBD) method, which has the advantage of high adhesion because of the graded interface mixes at the atomic level. The chemical [...] Read more.

The amorphous hydrogenated (a-C:H) film-coated titanium, using different CH₄/H₂ and deposition times, was prepared by the ion beam deposition (IBD) method, which has the advantage of high adhesion because of the graded interface mixes at the atomic level. The chemical characterizations and corrosion behaviors of a-C:H film were investigated and evaluated by SEM, AFM, Raman spectroscopy, EPMA, TEM and XPS. An a-C:H film-coated titanium was corroded at 0.8 V, 90 °C in a 0.5 mol/L H₂SO₄ solution for 168 h. The metal ion concentration in the H₂SO₄ corrosion solution and the potentiodynamic polarization behavior were evaluated. Results indicate that a higher CH₄/H₂ of 1:0 and a deposition time of 12 h can result in a minimum I_D/I_G ratio of 0.827, Ra of 5.76 nm, metal ion concentration of 0.34 ppm in the corrosion solution and a corrosion current of 0.23 µA/cm². The current density in this work meets the DOE’s 2020 target of 1 µA/cm². Electrical conductivity is inversely proportional to the corrosion resistance. The significant improvement in the corrosion resistance of the a-C:H film was mainly attributed to the increased sp³ element and nanocrystalline TiC phase in the penetration layer. As a result, the a-C:H film-coated titanium at CH₄/H₂ = 1:0 with improved anti-corrosion behavior creates a great potential for PEMFC bipolar plates. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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10 pages, 5350 KiB

Open AccessArticle

Fabrication and Sterilization Characteristics of Visible Light Photocatalyst of CuO/ZrO₂/CB/Coal-Tar-Pitch-SAC

by Ziang Xu, Guiying Xu, Beibei Han, Kun Wang, Hui Ge, Baigang An, Dongying Ju, Maorong Chai, Lixiang Li and Weimin Zhou

Coatings 2021, 11(7), 816; https://doi.org/10.3390/coatings11070816 - 06 Jul 2021

Cited by 3 | Viewed by 2105

Abstract

To provide an effective method of green aquaculture, the photocatalysts of CuO/ZrO₂/CB/coal-tar-pitch-SAC, which have visible light sterilization capacity, were successfully fabricated by coating ZrO₂ and CuO on the surface of CB/coal-tar-pitch-SAC. The structures of synthesized CuO/ZrO₂/CB/coal-tar-pitch-SAC were investigated [...] Read more.

To provide an effective method of green aquaculture, the photocatalysts of CuO/ZrO₂/CB/coal-tar-pitch-SAC, which have visible light sterilization capacity, were successfully fabricated by coating ZrO₂ and CuO on the surface of CB/coal-tar-pitch-SAC. The structures of synthesized CuO/ZrO₂/CB/coal-tar-pitch-SAC were investigated by XRD, XPS and SEM measurements in detail. It was observed that CuO/ZrO₂/CB/coal-tar-pitch-SAC materials possess obvious heterojunction structure and excellent visible light sterilization capacity when the prepared weight ratio of CuO, ZrO₂ and CB/coal-tar-pitch-SAC is controlled as 0.03:0.3:1. Our studies can provide a beneficial reference for the design of photocatalysts with sterilization capacity in visible light. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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11 pages, 3727 KiB

Open AccessArticle

Discrete Coating of CNT on Carbon Fiber Surfaces and the Effect on Improving the Electrochemical Performance of VRFB Systems

by Zhongxu Tai, Dongying Ju, Susumu Sato and Kenzo Hanawa

Coatings 2021, 11(6), 736; https://doi.org/10.3390/coatings11060736 - 18 Jun 2021

Cited by 2 | Viewed by 2508

Abstract

Carbon fiber, as an electrode material, has been widely used in all-vanadium liquid flow batteries. In order to further reduce the size of the all-vanadium storage system, it is imperative to increase the current density of the battery and to achieve high conductivity [...] Read more.

Carbon fiber, as an electrode material, has been widely used in all-vanadium liquid flow batteries. In order to further reduce the size of the all-vanadium storage system, it is imperative to increase the current density of the battery and to achieve high conductivity and large electrostatic capacitance. The graphitization of the electrode material and the improvement in the specific surface area of the electrode surface also greatly affect the performance of all-vanadium redox liquid flow batteries. Therefore, in this paper, carbon nanotubes (CNTs) with a small diameter and a large specific surface area were coated on the electrode surface of the VRFB system by the dispersion method to improve the cell performance. The performance of the surface-modified electrode was also verified by Raman spectroscopy, XRD and SEM surface observations and charge/discharge experiments. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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10 pages, 4619 KiB

Open AccessArticle

Metal Deposition Induced by the Step Region of Si (111)-(7 × 7) Surface

by Wenxin Li, Wanyu Ding, Youping Gong and Dongying Ju

Coatings 2021, 11(3), 281; https://doi.org/10.3390/coatings11030281 - 27 Feb 2021

Cited by 2 | Viewed by 1398

Abstract

Scanning tunneling microscope results showed that Au and Fe atoms were steamed on the Si (111)-(7 × 7) substrate surface, with or without the step region. The experimental comparison proved that the induced effect of the step region is a controllable process, which [...] Read more.

Scanning tunneling microscope results showed that Au and Fe atoms were steamed on the Si (111)-(7 × 7) substrate surface, with or without the step region. The experimental comparison proved that the induced effect of the step region is a controllable process, which CH₃OH can adjust. In this paper, the latest progress on the dynamic phenomenon on the step region is discussed, including three deposition types: strong deposition, weak deposition, and the new quasi deposition. With a relatively weak interaction between Au and Si atoms, the linearity of the weak deposition is present in the step region. In contrast, Fe atoms tend to form a strong deposition along the boundary line between the flat and step regions. Different depositions correspond to different surface potential energy: a newly formed surface is stabilized by a quasi-potential made by breaking, and a metal atomic structure can be stabilized by forming several quasi depositions. After discussing the good adsorption properties, CH₃OH can be used as an intermediate layer on the step region. As an important result of quasi deposition, a regular linear Fe cluster structure is created, which is perpendicular to the boundary line. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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Surface Modification and Functional Structure Space Design to Improve the Cycle Stability of Silicon Based Materials as Anode of Lithium Ion Batteries

by Fang Di, Weimin Zhou, Haiming Yang, Chengguo Sun, Xin Geng, Yiqing Chen, Lixiang Li, Zunfeng Liu and Baigang An

Coatings 2021, 11(9), 1047; https://doi.org/10.3390/coatings11091047 - 30 Aug 2021

Cited by 4 | Viewed by 6925

Abstract

Silicon anode is considered as one of the candidates for graphite replacement due to its highest known theoretical capacity and abundant reserve on earth. However, poor cycling stability resulted from the “volume effect” in the continuous charge-discharge processes become the biggest barrier limiting [...] Read more.

Silicon anode is considered as one of the candidates for graphite replacement due to its highest known theoretical capacity and abundant reserve on earth. However, poor cycling stability resulted from the “volume effect” in the continuous charge-discharge processes become the biggest barrier limiting silicon anodes development. To avoid the resultant damage to the silicon structure, some achievements have been made through constructing the structured space and pore design, and the cycling stability of the silicon anode has been improved. Here, progresses on designing nanostructured materials, constructing buffered spaces, and modifying surfaces/interfaces are mainly discussed and commented from spatial structure and pore generation for volumetric stress alleviation, ions transport, and electrons transfer improvement to screen out the most effective optimization strategies for development of silicon based anode materials with good property. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

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