Silica (SiO2) is one of the chief constituents of the earth’s crust. It is present in various forms, the most being quartz which is crystalline in character. Typical examples are siliceous sands and rock crystal. There are also various other crystalline forms such as tridymite and cristoblite. All types when fused at 2000°C give a vitreous material. Fused Silica Glass is a unique material with an unrivalled combination of purity, high temperature resistance, thermal shock resistance, good electrical insulation, optical transparency and chemical inertness. This material is widely used in the production processes of the semi-conductor industries.
The outstanding characteristic of silica glass is its very high degree of purity (99.99% SiO2).
It also has excellent thermal properties with an extremely low coefficient of expansion 0.55 x 106cm/cm°C (0-300°C). This makes the material particularly useful for optical flats 7 furnace windows, where its minimal sensitivity to thermal changes is of benefit. Another related property is its high resistance to thermal shock. Thin sections can be heated and cooled rapidly without cracking. Some technical references report, heating the material to 1100°C, then plunging into cold water with no adverse effects.
Softening Point 1683°C
Density 2.20 x 103Kg/m3
Annealing Point 1215°C
Strain Point 1120°C
Rigidity Modulus 32 x 106KN/m2
Continuous Operating Temp 1000°C
Compressive Strength 20 x 106KN/m2
Tensile Strength 70 x 103KN/m2
Electrical Resistivity 2 x 1019 ohm cm at 20°C
Shear Strength 70 x 103KN/m2
2 x 106 ohm cm at 800°C
Moh’s Hardness 6
Dielectric Strength 10KV/mm at 20°C
Total Metallic Impurities 10ppm (Typical)