Progress of Silicon Nitride Ceramics, Microstructure Evolution and Mechanical/Thermal Properties

Reference Presenter Authors
14-022 Tatsuki Ohji Ohji, T.(National Institute of Advanced Industrial Science and Technology (AIST)); Silicon nitride is one of the most important and widely used engineering ceramics for high temperature and high mechanical stress applications because of its excellent mechanical and thermal properties. During the last forty years, a great deal of research effort has been devoted for tailoring the microstructures and enhancing the mechanical and thermal properties, leading to tremendous progress of silicon nitride. This paper gives an overview on such progress of silicon nitride, on the basis of the reported literatures. Ceramic polycrystalline materials including silicon nitride ceramics are composed of a variety of structural elements, including, defects, grains, particles, pores, fibers, layers, and interfaces at different scale levels. It has been demonstrated that the mechanical and thermal properties of silicon nitride can be markedly improved by systematic control of these structural elements. Particularly, the structure of the grain boundary, which has been believed to affect substantially the properties of silicon nitride, has been elucidated relatively in details. The mechanical and thermal properties (strength, fracture toughness, heat resistance, thermal resistance, etc.) can be substantially enhanced in compatible manner, when the sizes, morphologies, orientation, distribution, etc. of grains and pores as well as grain boundary structure are carefully tailored. The paper also focuses on the recent developments and applications of silicon nitride ceramics, including wear resistance components for tribologcal applications, high thermal conductivity substrates for next-generation power devices, and energy-conscious manufacturing approaches for large-scaled products.
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