Quartz glass deoxygenation time

The dehydroxylation time of quartz glass is influenced by several factors, including the manufacturing process, the size of the glass, the atmosphere used during dehydrogenation, and the temperature applied.

Under normal melting conditions—such as in an oxidizing or neutral atmosphere—materials like SiCl4 are commonly used. In these cases, the dehydroxylation process may take longer due to the nature of the environment.

When quartz glass is produced using an oxyhydrogen flame, which involves high-temperature hydrolysis and vapor deposition, it often contains a significant amount of hydroxyl groups. This type of glass, especially when made with large-sized products, can be challenging to fully dehydroxylate. For example, synthetic or gas-refined quartz glass sheets that are 0.5 to 1.0 mm thick typically lose about 50% of their hydroxyl groups after being treated for 140 hours under vacuum or dry N2 at 1050°C. Beyond this time, the rate of hydroxyl removal slows significantly.

On the other hand, quartz glass melted in a hydrogen-rich reducing atmosphere—such as in a continuous furnace where H2 is used as a protective gas—can undergo more efficient dehydroxylation. This is because the presence of H2 helps stabilize and release hydroxyl groups that are in a metastable state, especially in areas with oxygen defects. As a result, a 1 to 1.5 mm thick fused quartz tube can lose over 90% of its hydroxyl content within just 2 hours under similar vacuum or flowing dry N2 conditions at 1050°C.

Similarly, if the quartz glass is synthesized or processed in a hydrogen-rich environment, applying the same dehydroxylation conditions can significantly enhance the removal of hydroxyl groups. This makes the hydrogen-rich atmosphere a preferred choice for achieving higher levels of dehydroxylation in certain applications.

Understanding these differences is crucial for optimizing the performance and properties of quartz glass in various industrial and scientific uses.