The dehydroxylation time of quartz glass depends on the preparation process and specifications of the quartz glass, the dehydroxylation atmosphere and temperature used.

Under normal melting conditions, i.e. oxidation or neutral atmosphere, such as SiCl4 as the raw material

Most of the hydroxyl groups in the quartz glass synthesized by high-temperature hydrolysis vapor deposition with hydrogen-oxygen flame as the heat source and quartz glass made by smelting and melting with crystal as the raw material and the hydrogen-oxygen flame as the heat source are in a stable state. It is also difficult to get rid of all the hydroxyl groups. Usually 0.5~1.0mm thick synthetic and gas-refined quartz glass sheets can be removed about 50% of the hydroxyl groups after 140h under vacuum or dry N2, 1050℃ dehydroxylation conditions, and almost no more removal after a longer time.

However, quartz glass melted in a hydrogen-rich reducing atmosphere, such as quartz glass melted in a continuous furnace using H2 as a protective gas, due to the existence of oxygen defects, the hydroxyl group in the quartz glass is metastable, and it is easy to diffuse and release H2 For example, 1~1.5mm thick smelting quartz glass tube can remove more than 90% of the hydroxyl groups after 2h under vacuum or flowing dry N2, 1050℃ dehydroxylation conditions.

Similarly, if the quartz glass is synthesized or gas-refined in a hydrogen-rich reducing atmosphere, the same dehydroxylation conditions can also greatly increase the amount of dehydroxylation.