Fabrication of c-axis oriented Si3N4 ceramics using multilayered-graphene-coated β-Si3N4 seeds and their orientation in an innovative low magnetic field

Abstract

c-axis oriented Si3N4 ceramics were fabricated by applying a low static magnetic field. Conventionally, c-axis oriented Si3N4 ceramics are fabricated using a rotating magnetic field of over 10T considering the anisotropy and the magnitude of diamagnetic susceptibility between c- and a-axes. In this work, multilayered-graphene was used for orienting rod-like β-Si3N4 particles as graphene exhibits a high diamagnetic anisotropy. The multilayered-graphene was coated with their orientation on the surface of rod-like β-Si3N4 particles by using a mechanical treatment process. As a result, the c-axis of multilayered-graphene-coated β-Si3N4 particles were oriented parallel direction to the applied magnetic field even at 0.4T. In addition, c-axis oriented Si3N4 ceramics were fabricated successfully by adding a small quantity of multilayered-graphene-coated β-Si3N4 particles as seeds. The thermal conductivity of the c-axis oriented Si3N4 ceramics prepared with a magnetic field of 0.4T exhibited anisotropy with a higher value achieved in the c-axis oriented direction.