Microstructural Evolution and Mechanical/Thermal Properties of Silicon Nitride Ceramics

During the past 40 years, there has been tremendous progress in mechanical and thermal performances of silicon nitride ceramics, which is one of the most important and widely used engineering ceramics, through well-organized control of the microstructure elements. For examples, both high strength and high fracture toughness can be attained by optimizing the size, morphology, and alignment of the grains simultaneously, while these two properties had been believed in antagonistic relationship. In addition, adjusting the chemical phases of grain boundaries leads to further significant improvements in the fracture toughness and high-temperature properties. Even in the porous materials, markedly high mechanical properties can be realized by carefully tailoring the porous microstructure. Furthermore, significantly high thermal conductivity and high fracture toughness can be achieved through controlling grain size/morphology and oxygen impurities.