The opaque quality comes from quartz sands of high purity when reduced to a molten state at a temperature of
approximately 2000° C. The high temperature produces a vitreous material characterized by the presence of a multitude of
gaseous micro-bubbles. These bubbles diffract light, giving the material its opacity. The term opaque silica is mainly
used for molded or centrifuged parts, while the product obtained by drawing is normally referred to as translucent.
Opaque silica glass offers a number of exceptional properties, such as:
MECHANICAL PROPERTIES |
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Specific Density (according to fusion process) |
1.98 to 2.12
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Hardness (Mohs scale) |
6
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Rupture stress: | traction | N.m-2 | 2.107 |
compression | N.m-2 | 5.108 |
ELECTRICAL PROPERTIES |
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Dielectric constants | 3.5 | |
Dielectric rigidity | V.m-1 | 5.106 |
Loss coefficients at 1 MHz | 20.10-4 |
THERMAL PROPERTIES |
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Linear expansion coefficient | K-1 | 5.4.10-7 |
Specific heat at 20° C | J.kg-1. K-1 | 7.5.102 |
Heat conductivity at 20° C | W.m-1. K-1 | 1.05 |
Annealing point | ° C | 1120 |
Softening point | ° C | 1460 |
CHEMICAL PROPERTIES |
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SiO2 content | % | 99.8 | |
Element content (typical analysis) | Fe | ppm | 14 |
Ti | ppm | 100 | |
Al | ppm | 550 | |
Ca | ppm | 40 | |
Mg | ppm | 11 | |
Na | ppm | 25 | |
K | ppm | 20 | |
Li | ppm | 5 |