Characteristics of fused silica - chemical reaction and thermal properties
The corrosion resistance of fused silica to various elements and compounds is another major advantage of its use in high-end applications. Fused silica has excellent water resistance and is resistant to the corrosion of salt water and acid. Only hydrofluoric acid and phosphoric acid can etch fused silica. Oxygen-free metals (except alkali and alkaline earth metals) do not chemically react with quartz glass or fused silica.
Fused silica easily reacts with alkali metals and alkaline earth metals. Therefore, even a very small amount of alkali metal and alkaline earth metal can cause crystallization to accelerate in a high temperature environment. We recommend that you erase fingerprints with alkali metals when using alcohol to heat quartz glass.
The extremely low coefficient of thermal expansion (CTE) is one of the most attractive properties of fused silica. The average coefficient of thermal expansion of fused silica is approximately 5.0 × 10 -7 / ° C, which is much lower than other common materials. Imagine if the volume of 1 cubic meter of stainless steel, borosilicate glass and quartz vessels are placed on a stove and heated to 500 ° C, the volume of borosilicate glass and stainless steel will expand by 5 liters and 28 liters respectively. The volume of fused silica expansion will be less than one liter. This low coefficient of thermal expansion allows this material to withstand very severe thermal shocks.
Even if it is taken out from a high temperature of 1000 ° C and immediately poured into cold water, it will not be chipped, so it can be used to make a quartz glass sheet. However, it must be noted that the thermal shock resistance of fused silica depends on factors such as its surface condition (determining its strength) and geometry rather than CTE. The CTE of all types of quartz glass and fused silica is almost identical, so they can be spliced ??together without worrying about the risk of chipping caused by sudden hot quenching.