Process for producing silicon nitride

Abstract From the Canadian patent

The invention provides a process for forming silicon nitride containing little or no silicon carbide. The process involves producing a uniform dispersion of finely divided silica particles in a polymer, heating the polymer/ silica dispersion in a non-oxidizing atmosphere to carbonize the polymer, and heating the resulting carbonized product to a temperature in the range of 1300-1800°C in a non-oxidizing nitrogen-containing atmosphere. This latter heating step is carried out in the presence of a metal oxide (preferably alumina) which is capable in the, reaction conditions, of reducing the amount of silicon carbide formed as an undesired by-product.