Papers by Keyword: Coating

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Authors: Sylvain Jacques, Houssam Fakih
Abstract: Thin (SiC/Ti3SiC2)n multi-layered coatings were deposited at 1100°C on ceramic substrates by chemical vapour deposition (CVD) methods. Each SiC sub-layer was classically processed from H2/CH3SiCl3. Each Ti3SiC2 sub-layer was obtained by reactive CVD (RCVD) from a H2/TiCl4 gaseous mixture reacting on each SiC solid sub-layer that was previously deposited. The growth of Ti3SiC2 by RCVD involves partial or total SiC consumption. The H2/TiCl4 ratio was chosen on the basis of a thermodynamic study. Using a sufficiently high H2/TiCl4 ratio and limiting the sub-layer thickness allowed the formation of TiC or binary titanium silicides to be avoided. By using a constant low gas pressure in the CVD reactor, it was possible to obtain nearly pure Ti3SiC2 sub-layers as thin as 0.8 μm. In that case, the ternary compound exhibits basal planes oriented perpendicular to the substrate surface. A way to obtain thinner sub-layers was the use of a pressurepulsed CVD method. In addition, the pressure-pulsed method allowed the preferential orientation to be prevented in the Ti3SiC2 coating.
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Authors: Qiu Ying Zhao, Ding Yong He, Xiao Yan Li, Jian Min Jiang
Abstract: Hydroxyapatite (HA) coatings were deposited onto Ti6Al4V substrate by microplasma spraying (MPS) in the current research. The morphology, phase compositions, and percentage of crystallinity of the coatings were characterized by means of scanning electron microscopy (SEM) and X-ray diffraction. An in vitro evaluation by soaking the coatings in simulated body fluid (SBF) for up to 14 days was conducted aiming at the evaluation of their bioactivity. Results from the present investigation suggest that microplasma sprayed HA coatings exhibited certain roughness, pores, and microcracks. Thermal decomposition existed in the coatings where HA, α-TCP,β-TCP, amorphous phases, and CaO-exclusive impurities were observed. The in vitro test indicated that HA coatings deposited by MPS possessed better bioactivity and stability. A layer of carbonate-apatite covered most of the coating surface, which did not exhibit significant spalling after incubation in SBF.
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Authors: Guna Civcisa, Tõnu Leemet
Abstract: This paper presents a study of 3D surface texture measurements and analysis of several surface texture parameters. A stylus measuring instrument was used to measure 3D surface topographies. In experimental part of this study, two coated gas turbine blades used in aerospace industry were chosen to examine surface of the coatings in nano-scale. Surface texture parameters of Ti-Al coating and Ti-Al-N coating were measured and compared to each other. The aim of the research is to analyze the surface of these coatings in an areal (3D) manner. The results indicate slight differences between these two surface textures despite the fact that both are Titanium-based coatings, and the surface of base material for both samples was prepared in the same way before deposition. Further study with repeated measurements of surface texture for deposed coatings has to be made after erosion tests.
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Authors: Yan Fang Shen, Wan Song, Xin Yu Cui, Tian Ying Xiong
Abstract: TiO2 is a promising photocatalyst with great potential for environment purification and energy conversion. TiO2 coatings have more advantages over powders in practical use. Cold spraying is an ideal technique to fabricate TiO2 coatings because of its low heat input compared with thermal sparing which may induce undesirable phase transformation from anatase to rutile. The paper will give a short introduction on recent development of TiO2 coatings by cold spraying. Then, the factors affecting the quality of coating should be analyzed. And finally, the bonding mechanism of cold sprayed TiO2 coating on metal substrates will also be proposed.
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Authors: Cheng Zhou Chen, Wei Ze Wang, Kai Di Cheng
Abstract: The vessel containing sulfur particles has been found failing due to the effect of corrosion and erosion by the sulfur particles. Several coatings, including zinc-aluminum coating, wear-resistance painting and two kinds of polymer, have been provided to resist the negative influence of sulfur in the present study. The wear and corrosion resistance of the selected coatings has been measured to study the performance difference. Impact test has also been done to investigate the bonding condition of coatings under the impact or bending load. The microstructure of coatings before and after wear test is observed by the Optical Microscope (OM) and Scanning Electron Microscope (SEM). The experiment results reveal that one of the polymer coatings shows the best performance in the corrosion resistance, another polymer coating’s wear resistance is better than others. The coatings are bonded well with the substrate except the zinc-aluminum coating. The performance of painting is ordinary in this investigation.
441
Authors: Badrinath Veluri, Henrik Myhre Jensen
Abstract: Corner cracks under steady-state delamination were investigated. The fracture mechanics parameters that include the strain energy release rate and the three-dimensional mode-mixity along the interface crack front are estimated. A numerical approach was then applied for coupling the far field solutions based on the Finite Element Method to the near field (crack tip) solutions based on the J-integral methodology. A quantitative approach was formulated based on the finite element method with iterative adjustment of the crack front nodal coordinates to estimate the critical delamination stresses as a function of the fracture criterion and corner angles.
457
Authors: Chien Chang Lin, Feng Min Lai, Chen Mao Yang
Abstract: The paper is investigated the polarization properties and mechanical behavior of new piezoelectric polymer material plates by experimental procedures and finite element analysis. In this study, the PVDF materials is used to produce the piezoelectric polymer layer and the coating film, we have provided a nice procedures for manufacturing piezoelectric polymer plates (PVDF). In order to find the proper proportion of the PVDF to achieve the best material properties, the mechanical behavior of displacements and stresses for the electrets is investigated by experimental measurement and finite element analysis (with ANSYS). It is investigated whether the thicknesses of specimens are affected the polarization. The paper is presented modal analysis techniques for piezoelectric thin plates.
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Authors: Yong Tian Wang, Wei Qiang Hu, Zong De Liu
Abstract: A Fe-based amorphous composite coating with different thickness on the Al thin plate is prepared by the electrothermal explosion spraying. Compared with other thermal spraying techniques, the electrothermal explosion spraying method can obtain a very high spraying velocity up to 4000m/s. The coating consists of the amorphous matrix and nanocrystal phases (α-Fe),no laminar phenomenon is observed. The diffusion occurs between the substrate and the coating, showing a diffusion-metallurgical bond. The average hardness of coatings is 8 times larger than that of the Al substrate. The unique hierarchical microstructure at multiple length scales leads to the superior micro-hardness and wear resistance of the coating. The Fe-based composite coatings on Al thin plate have great potential as the promising lightweight wear-resistance structural materials used in the aero technical industry.
389
Authors: Y. Zhao, Zhen Yue Ma, Li Lin, X.M. Li, M.K. Lei
Abstract: This paper provides a nondestructive method for determination of the density, thickness and velocity of homogeneous coating from an inversion of experimental ultrasonic reflection coefficient amplitude spectrum (URCAS). The detailed analyses of the inverse algorithm and sensitivity of URCAS to the density, thickness and velocity are presented, and the sensitivity is identified as a basis for selecting the experimental data used in inversion. An example of the method and experimental measurement for comparison was given for an epoxy coating with the thickness of 0.277 mm. The relative errors between the inversion and reference value of the density, thickness and velocity were found to be 0.5 %, 3.97 %, and 0.97 %, respectively.
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