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11 pages, 4938 KiB

Open AccessArticle

Model and Algorithm for a Rotor-Bearing System Considering Journal Misalignment

by Zhiming Zhao, Junjie Ma, Qi Liu and Peiji Yang

Coatings 2024, 14(1), 48; https://doi.org/10.3390/coatings14010048 - 28 Dec 2023

Viewed by 658

Disturbances caused as a result of the misalignment and axial motion of the journal affect the characteristics of the rotor-bearing system. This paper aims to propose an algorithm for the theoretical analysis of a rotor-bearing system that considers these disturbances. A theoretical model [...] Read more.

Disturbances caused as a result of the misalignment and axial motion of the journal affect the characteristics of the rotor-bearing system. This paper aims to propose an algorithm for the theoretical analysis of a rotor-bearing system that considers these disturbances. A theoretical model for a journal bearing considering disturbances is given. The dynamic equations for a rigid rotor-bearing system are introduced. A detailed algorithm that can simultaneously solve the rotor-dynamic equations and the Reynolds equation is proposed. The static performance, such as the bearing attitude angle and the fluid film pressure, are given, and dynamic characteristics such as the nonlinear dynamic responses and the axial orbits of a rigid rotor-bearing system are presented. The hydrodynamic effect of the bearing is enhanced by the axial disturbance. Disturbances in the circumferential and radial directions lead to variations in the fluid film thickness distribution in the axial direction and the offset of the fluid film pressure distribution in the axial direction. When these disturbances work together, the variation trend is more obvious and affects the capacity and dynamic characteristics of the bearing. When the L/D value of the bearing increases, the clearance between the journal and the bearing decreases rapidly. When the value reaches a certain limit, contact and collision might occur. The theoretical analysis method and the algorithm proposed for a rotor-bearing system considering several disturbances could enhance the design level for a bearing and rotor-bearing system. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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15 pages, 4721 KiB

Open AccessArticle

A Joint Estimation Method Based on Kalman Filter of Battery State of Charge and State of Health

by Qingxia Yang, Ke Ma, Liyou Xu, Lintao Song, Xiuqing Li and Yefei Li

Coatings 2022, 12(8), 1047; https://doi.org/10.3390/coatings12081047 - 24 Jul 2022

Cited by 3 | Viewed by 1701

Abstract

In a battery management system, the accurate estimation of the battery’s state of health (SOH) and state of capacity (SOC) are vital functions. The traditional estimation methods have limitations. To accurately estimate the SOC and SOH of power battery and improve the performance [...] Read more.

In a battery management system, the accurate estimation of the battery’s state of health (SOH) and state of capacity (SOC) are vital functions. The traditional estimation methods have limitations. To accurately estimate the SOC and SOH of power battery and improve the performance of the long-term estimation of a battery’s SOC, a joint estimation method based on a Kalman filter is proposed in this work. First, a second-order RC equivalent circuit model of a ternary lithium battery was built, whose parameters were identified online, and the model’s accuracy was verified. Then, the battery data under actual working conditions were collected. The SOC and SOH were estimated based on the Kalman filter algorithm, and the simulation was implemented using MATLAB. Finally, according to a time scale transformation, the battery state was jointly estimated, the SOC was estimated at a short-time scale, the SOH was estimated at a long-time scale, and the SOH estimation results were updated to the model parameters for SOC estimation. The results show that the accuracy of the method is very good, and it can effectively improve estimation accuracy and ensure batteries’ long-term estimation performance. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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12 pages, 6386 KiB

Open AccessArticle

Microstructure and Nanoindentation Evolution of (Ni,Pt)Al Coating on IC21 Substrate at 1100 °C

by Yingkun Liu, Yun Ye, Bin Yin, Chunming Deng, Min Liu and Chaoqun Wu

Coatings 2022, 12(6), 796; https://doi.org/10.3390/coatings12060796 - 08 Jun 2022

Cited by 2 | Viewed by 1410

Abstract

In this study, a ~20 μm (Ni,Pt)Al coating was applied to an IC21 substrate via electroplating followed by aluminizing. A thermal exposure test at 1100 °C in air was used to investigate the microstructure evolution and nanoindentation behavior of samples with and without [...] Read more.

In this study, a ~20 μm (Ni,Pt)Al coating was applied to an IC21 substrate via electroplating followed by aluminizing. A thermal exposure test at 1100 °C in air was used to investigate the microstructure evolution and nanoindentation behavior of samples with and without coating. The experimental results show that the (Ni,Pt)Al coating caused a phase change from β-(Ni,Pt)Al to Ni₃Al, and the Topologically Close-Packed (TCP) phase at the interdiffusion zone grew larger after thermal exposure for 200 h at 1100 °C, while a layer of γ’ phase was formed on the surface of the IC21 substrate. The nanoindentation test indicated that the elastic modulus was reduced in both annealed samples (with and without coating), and after annealing the sample with coating had higher elastic modulus than the sample without coating. This result reveals that the coating effectively prevented the precipitation of refractory metal elements and the coarsening of the microstructure in the substrate, and thus shows that the coating had advantages not only in terms of improving the high-temperature oxidation properties of the substrate, but also played a significant role in improving the mechanical properties of the substrate. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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13 pages, 7114 KiB

Open AccessArticle

Friction and Wear Properties of Silicon Nitride-Based Composites with Different hBN Content Sliding against Polyether-Etherketone at Different Speeds under Artificial Seawater Lubrication

by Huaqiang Li, Xingwei Liu, Chen Zhang, Xiaoyu Jiao, Wei Chen, Jinghui Gao and Lisheng Zhong

Coatings 2022, 12(3), 411; https://doi.org/10.3390/coatings12030411 - 19 Mar 2022

Cited by 5 | Viewed by 2373

Abstract

In the present study, the friction and wear behaviors of Si₃N₄-hBN(Hexagonal boron nitride) ceramic composites against polyether-etherketone in artificial seawater were investigated, and the sliding speed was varied from 0.52 to 1.73 m/s to study the effect. It was [...] Read more.

In the present study, the friction and wear behaviors of Si₃N₄-hBN(Hexagonal boron nitride) ceramic composites against polyether-etherketone in artificial seawater were investigated, and the sliding speed was varied from 0.52 to 1.73 m/s to study the effect. It was found that the friction coefficients and wear rates decreased with the increase in sliding speed for Si₃N₄-hBN (with the hBN content ranging from 5% to 20%) against PEEK(Polyether-ether-ketone); the sliding pairs represented an upward trend as the speed increased for Si₃N₄-hBN (with an hBN content of 0 and 30%) against PEEK. This result was mainly attributed to complex friction resistance sources, such as mechanical meshing and the shear strength of soft tribofilm. On the other hand, both the hBN content and sliding speed had a significant effect on the tribological performance of the Si₃N₄-hBN/PEEK pairs. Meanwhile, the lowest friction coefficient of 0.07 and wear rates below 10⁻⁶ mm³/Nm were obtained from the Si₃N₄-20%hBN/PEEK pair at the speed of 1.73 m/s. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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11 pages, 3453 KiB

Open AccessArticle

Influence of Cross-Grooved Texture Shape on Tribological Performance under Mixed Lubrication

by Song Hu, Long Zheng, Qinggang Guo and Luquan Ren

Coatings 2022, 12(3), 305; https://doi.org/10.3390/coatings12030305 - 24 Feb 2022

Cited by 7 | Viewed by 1902

Abstract

Surface texture plays an important role in improving the tribological properties of materials. In this paper, the effect of different shapes (i.e., triangle, square, hexagon, round) on the tribological performance of cross-grooved texture was investigated. First, the mixed lubrication condition was used for [...] Read more.

Surface texture plays an important role in improving the tribological properties of materials. In this paper, the effect of different shapes (i.e., triangle, square, hexagon, round) on the tribological performance of cross-grooved texture was investigated. First, the mixed lubrication condition was used for the pin-on-disc rotating sliding tests. Then, the stress distribution of the four textures was analyzed to better explain the experimental results. Overall, the hexagon-textured specimens exhibited lower friction coefficients than the other shape-textured specimens under the examined conditions. Simulation results indicate that the contact stress can be reduced on the surface of hexagon-textured specimens, and this leads to a better oil film for lubrication. Furthermore, the hydrodynamic lubrication stood out with the increase of speeds to 250 rpm. However, as the test loads further increased, the film thickness decreased, resulting in the increase in the asperity contact areas, which dropped the above advantage of hexagon-textured specimens. This study would be beneficial for the texturing tribological and lubrication design. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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10 pages, 1944 KiB

Open AccessArticle

Amphiphilic Janus Microspheres Prepared by Caged Photoactivatable Alkoxysilane

by Wei Li, Daodao Hu, Jinxin Ma and Shukun Shen

Coatings 2022, 12(2), 198; https://doi.org/10.3390/coatings12020198 - 02 Feb 2022

Cited by 1 | Viewed by 1394

Abstract

A simple photolysis route was proposed to prepare Amphiphilic Janus Particles (AJP) based on SiO₂ microspheres. The surface of SiO₂ microspheres were modified by photoactive alkoxysilane, which was synthesized by dealcoholization condensation of 6-nitroveratroyloxycarbonyl and isocyanatopropyl-triethoxysilane. UV irradiation caused eater-breaking allowed [...] Read more.

A simple photolysis route was proposed to prepare Amphiphilic Janus Particles (AJP) based on SiO₂ microspheres. The surface of SiO₂ microspheres were modified by photoactive alkoxysilane, which was synthesized by dealcoholization condensation of 6-nitroveratroyloxycarbonyl and isocyanatopropyl-triethoxysilane. UV irradiation caused eater-breaking allowed for the precise control of hydrophilic modification of the hemispherical exposed particles surfaces. The component and morphology of the obtained particles were characterized by fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy, and the Janus feature was evaluated by scanning electron microscopy, transmission electron microscopy, and dispersity in the oil–water dual-phases. The following results were obtained. The AJP with 450 nm size processes the hydrophilic amino groups on one side and the hydrophobic 6-nitroveratryloxycarbonyl moieties on the other. Additionally, the AJP were located at the phase boundary between water and n-hexane, and the negative charged gold nanoparticles with 25 nm size were adsorbed only onto the side with the positive charged amino groups. The AJP have interfacial adsorption energies that can be as much as three times larger than that of homogeneous particles and thus exhibit excellent surface activities. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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11 pages, 5124 KiB

Open AccessArticle

Evaluating the Performance of Aluminum Sacrificial Anodes with Different Concentration of Gallium in Artificial Sea Water

by Yuntao Xi, Mao Jia, Jun Zhang, Wanli Zhang, Daoyong Yang and Liang Sun

Coatings 2022, 12(1), 53; https://doi.org/10.3390/coatings12010053 - 02 Jan 2022

Cited by 8 | Viewed by 2296

Abstract

In this manuscript, the influence of gallium content additions of Al-Zn-In-Mg alloy was investigated through electrochemical techniques and microstructure observation in 3.5 wt% NaCl solution. The results indicated that Al-Zn-In-Mg-0.03Ga alloy has the best discharge performance among all alloys. We propose that this [...] Read more.

In this manuscript, the influence of gallium content additions of Al-Zn-In-Mg alloy was investigated through electrochemical techniques and microstructure observation in 3.5 wt% NaCl solution. The results indicated that Al-Zn-In-Mg-0.03Ga alloy has the best discharge performance among all alloys. We propose that this is due to the fact that gallium addition to the Al-4Zn-In-Mg alloy improves the discharge activity of the alloy as well as elevating its anodic efficiency. In particular, the effect of gallium addition to improve discharge activity tends to be a parabolic curve, in which there is an increase when the gallium is first added that rises to the maximum anode current efficiency of about 98.25% whenever gallium content is 0.03 wt%. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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10 pages, 5071 KiB

Open AccessArticle

Investigations of Microstructures and Erosion–Corrosion Performance of Cast Boron-Bearing Stainless Steel

by Dawei Yi, Bin Li, Xiao Tan, Sifan Liu, Jin Chen and Yefei Li

Coatings 2021, 11(12), 1553; https://doi.org/10.3390/coatings11121553 - 17 Dec 2021

Viewed by 1798

Abstract

The microstructures and erosion–corrosion properties of boron-bearing stainless steel were researched by an erosion–corrosion tester, energy dispersive X–ray spectrometry, scanning electron microscope and X-ray diffraction analysis. The microstructures of as-cast, boron-bearing stainless steel contain M₇(B,C)₃, M₂(B,C) borocarbides [...] Read more.

The microstructures and erosion–corrosion properties of boron-bearing stainless steel were researched by an erosion–corrosion tester, energy dispersive X–ray spectrometry, scanning electron microscope and X-ray diffraction analysis. The microstructures of as-cast, boron-bearing stainless steel contain M₇(B,C)₃, M₂(B,C) borocarbides and the martensite matrix; the matrix has less chromium and more nickel than those in the M₂(B,C) and M₇(B,C)₃. The microstructures in heat-treated, boron-bearing stainless steel consist of M₇(B,C)₃, M₂(B,C) and M₂₃(B,C)₆ borocarbides and ferrite, and the Rockwell hardness of heat-treated, boron-bearing stainless steel is lower than that of as-cast steel. For Cr28 white cast iron and boron-bearing stainless steel, the mixing wheel with higher rotating speed leads to a higher erosion–corrosion weight loss, and as the impingement angle increases, the erosion–corrosion weight loss increases first, and then decreases. For any erosion–corrosion experiment conditions, the erosion–corrosion resistance of boron-bearing stainless steel is better than that of Cr28 white cast iron. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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23 pages, 90506 KiB

Open AccessArticle

First-Principle Study of Co-Adsorption Behavior of H₂O and O₂ on δ-Pu (100) Surface

by Guoliang Wang, Zhaoyang Zhao, Pengfei Zhai, Xudan Chen and Yefei Li

Coatings 2021, 11(9), 1098; https://doi.org/10.3390/coatings11091098 - 11 Sep 2021

Cited by 1 | Viewed by 1994

Abstract

The surface corrosion of plutonium in air is mainly the result of the interaction with O₂ and H₂O in air. In this paper, the co-adsorption behavior of O₂ and H₂O on a δ-Pu (100) surface is studied [...] Read more.

The surface corrosion of plutonium in air is mainly the result of the interaction with O₂ and H₂O in air. In this paper, the co-adsorption behavior of O₂ and H₂O on a δ-Pu (100) surface is studied by the first-principle method. Two different cases of preferential adsorption of H₂O and O₂ are considered, respectively. Bader charge analysis and adsorption energy analysis are carried out on all stable adsorption configurations, and the most stable adsorption configurations are found under the two conditions. The results of differential charge density analysis, the density of states analysis and Crystal Orbital Hamilton Populations (COHP) analysis show that the two molecules can promote each other’s adsorption behavior, which leads to the strength and stability of co-adsorption being far greater than that of single adsorption. In the co-adsorption configuration, O atoms preferentially interact with Pu atoms in the surface layer, and the essence is that the 2s and 2p orbitals of O overlap and hybridize with the 6p and 6d orbitals of Pu. H atoms mainly form O–H bonds with O atoms and hardly interact with Pu atoms on the surface layer. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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12 pages, 9235 KiB

Open AccessArticle

Basic Bio-Tribological Performance of Insulating Si₃N₄-Based Ceramic as Human Body Replacement Joints

by Huaqiang Li, Wei Chen, Hongxing Shi, Chen Zhang, Xingwei Liu and Lisheng Zhong

Coatings 2021, 11(8), 938; https://doi.org/10.3390/coatings11080938 - 05 Aug 2021

Cited by 5 | Viewed by 1703

Abstract

The paper presents an in-depth study of the bio-tribological performance on silicon nitride matrix ceramic composites containing hexagonal boron nitride (hBN) with different content. Ultra-high molecular weight polyethylene (UHMWPE) under simulated body fluid lubrication, and the simulated body fluid-lubricated sliding tests were performed [...] Read more.

The paper presents an in-depth study of the bio-tribological performance on silicon nitride matrix ceramic composites containing hexagonal boron nitride (hBN) with different content. Ultra-high molecular weight polyethylene (UHMWPE) under simulated body fluid lubrication, and the simulated body fluid-lubricated sliding tests were performed on a universal friction and wear tester. The results showed that the incorporation of hBN into silicon nitride matrix reduced the friction coefficients from 0.27 for Si₃N₄/UHMWPE pair to 0.16 for Si₃N₄-20%hBN/UHMWPE with full immersion in simulated body fluid lubrication. Scanning electron microscopy (SEM), laser scanning microscope, X-ray photoelectron spectroscopy (XPS) were utilized to characterize the wear surface. The analysis results indicated that, with simulated body fluid lubrication, the interfacial between hBN and Si₃N₄ facilitated the wear pits to form on the wear surface, and the residual wear particles deposited in the pits. Then, tribochemical products were formed on the wear surface, which protected and smoothed the wear surface of the sliding pair in the simulated body fluid. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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14 pages, 3629 KiB

Open AccessArticle

Intelligent Life Prediction of Thermal Barrier Coating for Aero Engine Blades

by Ruipeng Gao, Wei Mao, Yiran Wang, Shanshan Fan and Wei Shao

Coatings 2021, 11(8), 890; https://doi.org/10.3390/coatings11080890 - 26 Jul 2021

Cited by 7 | Viewed by 2207

Abstract

The existing methods for thermal barrier coating (TBC) life prediction rely mainly on experience and formula derivation and are inefficient and inaccurate. By introducing deep learning into TBC life analyses, a convolutional neural network (CNN) is used to extract the TBC interface morphology [...] Read more.

The existing methods for thermal barrier coating (TBC) life prediction rely mainly on experience and formula derivation and are inefficient and inaccurate. By introducing deep learning into TBC life analyses, a convolutional neural network (CNN) is used to extract the TBC interface morphology and analyze its life information, which can achieve a high-efficiency accurate judgment of the TBC life. In this thesis, an Adap–Alex algorithm is proposed to overcome the problems related to the large training time, over-fitting, and low accuracy in the existing CNN training of TBC images with complex tissue morphologies. The method adjusts the receptive field size, stride length, and other parameter settings and combines training epochs with a sigmoid function to realize adaptive pooling. TBC data are obtained by thermal vibration experiments, a TBC dataset is constructed, and then the Adap–Alex algorithm is used to analyze the generated TBC dataset. The average training time of the Adap–Alex method is significantly smaller than those of VGG-Net and Alex-Net by 125 and 685 s, respectively. For a fixed number of thermal vibrations, the test accuracy of the Adap–Alex algorithm is higher than those of Alex-Net and VGG-Net, which facilitates the TBC identification. When the number of thermal vibrations is 300, the accuracy reaches 93%, and the performance is highest. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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12 pages, 7785 KiB

Open AccessArticle

The Microstructure and Mechanical and Corrosion Behaviors of Thermally Aged Z3CN20-09M Cast Stainless Steel for Primary Coolant Pipes of Nuclear Power Plants

by Fei Xue, Fangjie Shi, Chuangju Zhang, Qiaoling Zheng, Dawei Yi, Xiuqing Li and Yefei Li

Coatings 2021, 11(8), 870; https://doi.org/10.3390/coatings11080870 - 21 Jul 2021

Cited by 5 | Viewed by 2336

Abstract

The effects of thermal aging time at 400 °C on the microstructure and mechanical and corrosion behaviors of Z3CN20.09M cast stainless steel were investigated; and the corresponding thermal aging mechanism was studied. It was revealed that the changes in mechanical properties after thermal [...] Read more.

The effects of thermal aging time at 400 °C on the microstructure and mechanical and corrosion behaviors of Z3CN20.09M cast stainless steel were investigated; and the corresponding thermal aging mechanism was studied. It was revealed that the changes in mechanical properties after thermal aging were mainly caused by the iron-rich phase (α) and the chromium-rich phase (α’) produced by the amplitude-modulation decomposition of ferrite. A similar trend of thermoelectric potential during thermal aging was determined in relation to the Charpy impact energy. However, the corrosion resistance of Z3CN20.09M cast stainless steel deteriorates as thermal aging time increases. When the thermal aging is longer than 3000 h, the precipitation of G phase has a great influence on the corrosion resistance. The interfacial matching relationship between G phase and the surrounding ferrite was established by selected area electron diffraction of HRTEM. The relationship is of cube-on-cube phase boundary type. The impact fracture mechanisms in relation to thermal aging time were also studied and compared. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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Review

Jump to: Research

13 pages, 2521 KiB

Open AccessReview

Research Progress on the Application of Graphene Quantum Dots

by Xiangyu Tan, Fangrong Zhou, Wenyun Li, Gang Ao, Xiaowei Xu and Le Yang

Coatings 2023, 13(11), 1956; https://doi.org/10.3390/coatings13111956 - 16 Nov 2023

Viewed by 952

Abstract

Graphene quantum dots (GQDs) are sets of carbon quantum dots derived from graphene or graphene oxide, and they have obvious graphene lattice properties. The number of layers in GQDs is generally no more than five layers, and the diameter size of GQDs is [...] Read more.

Graphene quantum dots (GQDs) are sets of carbon quantum dots derived from graphene or graphene oxide, and they have obvious graphene lattice properties. The number of layers in GQDs is generally no more than five layers, and the diameter size of GQDs is generally less than 10 nm. GQDs have stable photoluminescence characteristics, high specific surface areas, high conductivity levels and adjustable band gaps, and they can be used in sensing systems such as ion detection sensing, optical biosensing, electrochemical biosensing and electronic sensing. Based on the research status of GQDs in recent years and the application background of sensing systems, this review paper focuses on the synthesis strategies, sizes, chemical compositions, crystal structures, optical properties and sensor applications of GQDs. Full article

(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)

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