OPTICAL MOLDINGS MADE FROM SILICON NITRIDE, AND A PROCESS FOR THEIR PRODUCTION

摘要

- ? HOE 90/F 129 of the disclosure Process for the preparation of optical materials from silicon nitride A process for the preparation of optical materials from silicon nitride by pyrolysis of polymeric silazanes, by pressing the pulverulent polymeric silazanes to give moldings before the pyrolysis or first dissolving the polymeric silazanes in an organic solvent, drawing fibers from this solution and pyrolyzing these fibers after evaporation of the solvent, or by melting polymeric silazanes, casting, injection-molding or extruding this melt to give moldings and subsequently pyrolyzing the moldings. An oxidic coating is produced on the silicon nitride molding in an oxygen-containing atmosphere during or after the pyrolysis. The pyrolysis can be carried out at 800-1000.degree.C in an atmosphere containing ammonia or an ammonia/inert gas mixture.