Preparation of Silicon Nitride from Silica

The nucleation and growth of Si 3 N 4 from a carbon‐Si0 2 mixture in an N 2 atmosphere at 1400°C was studied by varying the specific surface area, particle size, and distribution of the Si0 2 and carbon. Si 3 N 4 yield increased and particle size decreased with increasing Si0 2 and carbon specific surface area. Manner of distribution appeared to have little effect but was difficult to assess. A model was proposed in which heterogeneous nucleation occurs on either the Si0 2 or C surfaces only in the early stages of the reaction. Growth occurs by the reaction