Influence of Fe impurity in nitridation of Si + B4C green compact

Abstract

The addition of B4C powder retarded the nitridation of the silicon powder green body by the formation of a borosilicate layer in interfaces between Si grains. The viscous layers hindered the SiO formation and the Si and N diffusion. Despite the presence of borosilicate layers, the Fe impurity in the green body still promoted the Si nitridation process by the formation of fluid iron silicide and the promotion of the B4C conversion to BN in gaps or holes in the viscous borosilicate layers. The addition of 5% H2 in the N2 atmosphere accelerated the Si + B4C nitridation, where the hydrogen acted as an oxygen getter, thus reducing the amount of glassy borosilicate in the interface.