Papers by Keyword: Functionally Graded Coating

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Authors: Jae Ho Jeon, Hai Tao Fang, Zhong Hong Lai, Zhong Da Yin
Abstract: The concept of functionally graded materials (FGMs) was originated in the research field of thermal barrier coatings. Continuous changes in the composition, grain size, porosity, etc., of these materials result in gradients in such properties as mechanical strength and thermal conductivity. In recent years, functionally graded structural composite materials have received increased attention as promising candidate materials to exhibit better mechanical and functional properties than homogeneous materials or simple composite materials. Therefore the research area of FGMs has been expending in the development of various structural and functional materials, such as cutting tools, photonic crystals, dielectric and piezoelectric ceramics, thermoelectric semiconductors, and biomaterials. We have developed functionally graded structural ceramic/metal composite materials for relaxation of thermal stress, functionally graded anti-oxidation coatings for carbon/carbon composites, and functionally graded dielectric ceramic composites to develop advanced dielectric ceramics with flat characteristics of dielectric constant in a wide temperature range. This paper introduces functionally graded coatings for C/C composites with superior oxidation resistance at high temperatures.
Authors: Chang Qing Sun, Hua Wei, Hong Gao
Abstract: In this paper, aiming at three material parameter functions of functionally graded coating (FGC) which have different continuities, the influence of functionally gradient coating material continuity on the fracture behaviors of the crack on the interface between the base material and coating is studied. The results show that when the functionally graded coating structure is under a tension load, if the ratio of maximum elastic modulus of the FGC to the elastic modulus of the base is less than 10, the functionally graded layer which has C02 continuity can help to improve the fracture resistance of the interface crack, and if the ratio increases continuously, the functionally graded layer which has C13 continuity can help to improve the fracture resistance of the interface crack, which is of great guiding significance for practical engineering design.
Authors: A. Joseph Nathanael, Jun Hee Lee, Sun Ig Hong
Abstract: Nanocomposited and Functionally graded (FG) ZrN/hydroxyapatite coatings with good mechanical strength and biocompatibility were prepared on cp-Ti substrate for biomedical applications and detailed analysis of the nanocomposite coatings for its structural, morphological, topographical and biocompatibility properties were carried out. Crystallite size of the coating for the functionally graded coatings was smaller compared to that of nanocomposite coatings. The arrangement of grains was observed to be denser in the FG coatings due to the decrease in the grain size. Hardness and modulus of FG coatings were observed to be greater than those of nanocomposite coating, which was attributed to the reduction in the crystallite size in FG coatings. Both ZrN/HA nanocomposite and functionally graded coatings was found to induce biomineralization formation, suggesting both are promising candidates for the future biomedical applications.
Authors: Tolga Tavşanoğlu, O. Addemir, E. Başaran, S. Alkoy
Authors: S.M. Aizikovich, L.I. Krenev, I.S. Trubchik
Abstract: Recent advances in nanotechnology have revealed numerous new methods of manufacturing functionally graded coatings and materials, but progress in this field is limited by the lack of knowledge about the mechanical behavior of such structures. Existing models of the mechanics of layered structures are not generally adequate for this purpose, since functionally graded structures can exhibit both qualitative and quantitative behavioral differences in comparison with homogeneous or layered structures, particularly if there is a significant gradient of elastic properties in the coating. In applications, interest is focused mainly on the deformation fields and stresses inside the inhomogeneous material caused by the contact tractions. Stresses at the interface between the functionally graded coating and the elastic half-space are of particular interest because of their influence on the propagation of cracks and other defects on this interface. Shear stresses at this interface associated with rapid variation in elastic properties with depth are particularly dangerous because of potential delaminations. In their work the authors: • develop a precise mathematical model and of the computational methods which makes it possible to achieve stable numerical results while analyzing the mechanical properties of functionally graded coatings; • study the variation effect in elastic properties on the maximum stresses in the surface layers of materials with functionally graded coatings caused by indentation.
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