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Chemical stability of quartz glass

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Update time : 2022-10-24 10:00:00

Quartz glass has high resistance to acid and corrosion. It itself belongs to the acid material, except hydrofluoric acid and hot phosphoric acid performance are inert, can be used as acid resistant material. At room temperature does not exclude the use of quartz glass in alkali and salt reagents, because the degree of corrosion of alkali and salt at room temperature is also relatively small.

There are bubbles inside the opaque quartz glass, which increase the surface area exposed to the corrosion liquid and aggravate the corrosion degree. Therefore, the chemical stability of opaque quartz glass is not as good as that of transparent quartz glass.

Quartz glass has the characteristics of no moisture absorption and no weathering. It is very sensitive to all alkali and alkaline earth compounds, and even the smallest trace amounts of these compounds will induce crystallization at high temperatures.

Crystallization is an inherent defect of quartz glass. From the thermodynamic point of view, the internal energy of quartz glass is higher than that of crystalline calcite, which is a thermodynamically unstable metastable state. When the temperature is higher than 1000 °C, the vibration of SiO₂ molecules is accelerated, and crystals are formed after a long period of rearrangement and directionality. The permeability is expressed by the growth rate of crystal nucleus. The crystallization speed of opaque quartz glass at 1520℃ and transparent quartz glass at 1620℃ respectively reaches the maximum.

Crystallization mainly occurs on the surface of quartz glass, followed by internal defects. The reason is that these places are easy to stain, causing local aggregation of impurity ions, especially alkali ions (such as K, Na, Li, Ca, Mg, etc.) after entering the network, the viscosity is reduced and the permeability is accelerated.

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