Reactions in the systems Mo-Si3N4 and Ni-Si3N4

The reaction products, formed during annealing of porous powder mixts. of Si3N4 with nonnitride-forming metals like Ni or Mo, will depend on the partial pressure of N2 in the atm. In a diffusion couple, however, nitrogen has to be released at the Si3N4 interface during the formation of a metal silicide. It cannot escape easily and build up a higher pressure of nitrogen at this interface. Therefore, the reaction products are different from those in porous pellets. This has been verified for Ni-Si3N4 and Mo-Si3N4 couples. The role of traces of oxygen on these reactions is discussed. [on SciFinder (R)