What is Quartz Glass?
- Quartz glass is valued for its superior optical properties (i.e. light transmittance), low coefficient of thermal expansion, and good chemical resistance.
- The starting material for quartz glass production is natural quartz, cultured quartz or a synthetic precursor such as silicon tetrachloride.
- The crystalline structure of quartz comprises strong, covalent silicon-oxygen bonds; a single molecule forms a tetrahedral geometry. A network of SiO4 molecules forms a body-centered crystal in hexagonal prism form. When processed, the crystalline structure is converted to metastable, amorphous quartz glass.
- Quartz crystals undergo particle size reduction to prepare it for the fusion process.
- Electric fusion produces Type I glass. The quartz sand or crystals are fed into a refractory crucible and the melt is collected to be formed into various parts. Flame fusion utilizes hydrogen-oxygen flame. Type II glass is produced from crystal quartz by passing through the hydrogen-oxygen flame; Type III glass, on the other hand, is produced by combustion of silicon tetrachloride with the flame. Plasma fusion, which produces Type IV glass, is almost similar to flame fusion, except in which plasma flame is used in this method.
- Resulting quartz glass undergoes further processing to transform into utilizable products.
- Purity is an important aspect of quartz glass. Hydroxyl (OH) groups can drastically affect the performance of the quartz glass. Quartz glass is resistive to most chemical reagents, but sensitive to alkali compounds.
- Quartz glass is used in the manufacturing of optical devices, lighting systems, refractory materials, and chemical apparatuses.
- One must observe proper precautions when handling quartz glass to protect its reliability. The glass must be kept clean all the time. Its thermal behavior must be taken into consideration when designing its application.
- Devitrification is the conversion of the metastable quartz glass into a stable cristobalite quartz crystal.