Preventing crystallisation of quartz glass - by thermal treatment with metal oxide or salt

摘要

Cristobalite crystallisation of quartz glass is hindered by applying onto the glass article the oxide of a gp. III metal or a salt yielding the same upon heating (pref. Al2O3) and subjecting the coated articles to a thermal treatment (pref. at 1200 degrees C). Al2O3 blocks the surface of the quartz glass, bars the diffusion of alkalis and sterically hinders the cristobalite formation. This process is esp. suitable for treating quartz glass articles frequently subjected to temp. fluctuations passing the cristobalite quartz transformation point (230 degrees C).