種結晶を用いた窒化ケイ素セラミックスの微構造制御と機能発現

Abstract

It has been reported that the size and distribution of β-Si3N4 particles existing in silicon nitride raw powder are crucial factors governing the microstructure of silicon nitride ceramics. Considering such the grain growth behavior, a processing strategy for controlling the microstructure of silicon nitride ceramics has been developed. The key point of this process is to control the size, distribution and orientation of large elongated β-Si3N4 grains via seeding of morphologically regulated β-Si3N4 single crystal particles. Silicon nitrides with textured microstructure where elongated β-Si3N4 grains were unidirectionally or two-dimensionally orientated could be fabricated by combining the seeding with forming methods of extrusion or tape casting. The textured silicon nitride exhibited superior mechanical properties such as high strength, high fracture toughness, high creep resistance, and had a high Weibull modulus of about 50. Moreover it has been revealed that the material exhibits unique tribological and thermal properties.