Silicon dioxide (SiO₂), also known as silica, is a naturally occurring compound found in various forms such as quartz and sand. It appears white or colorless, with the color becoming more yellow as iron content increases. Its density ranges from 2.2 to 2.66 g/cm³, with a melting point of approximately 1670°C (for α-quartz) and 1710°C (for β-cristobalite). The boiling point is around 2230°C, and it has a relative dielectric constant of 3.9. Silica is insoluble in water but slightly soluble in certain acids. It is commonly used in glass, ceramics, refractories, and silicon production.
In the semiconductor industry, silica is used as a protective layer during impurity diffusion in transistors and integrated circuits, forming a thin oxide film. It is also an essential component in the production of water glass, which serves as a precursor for many silicon-based compounds.
Silica exists in both crystalline and amorphous forms. Crystalline silica includes quartz, tridymite, and cristobalite. Quartz, the most common form, can be transparent or colored depending on impurities. Amorphous silica, like diatomite, is porous and highly absorbent, often used in filtration and insulation applications.
The specific surface area of silica is a critical parameter, measured using the BET method based on low-temperature nitrogen adsorption. This technique helps determine the surface area per unit mass of the material. The 3H-2000 series of fully automatic nitrogen adsorption testers are widely used for this purpose, offering high accuracy, repeatability, and advanced features such as integrated purge systems and program-controlled injection valves.
Chemically, silica is stable and does not react with water. However, it reacts with hydrofluoric acid to form silicon tetrafluoride gas and with strong alkalis at high temperatures to produce silicates. It is used in the manufacturing of optical fibers, glass, ceramics, and electronic components.
In practical applications, silica is a key raw material in the production of glass, ceramics, concrete, and industrial abrasives. It is also used in the rubber and plastic industries to enhance mechanical properties, and in pharmaceuticals and food as an anti-caking agent or filler.
For accurate and reliable specific surface area testing, the 3H-2000 series instruments are recommended. These devices provide precise measurements, ensuring quality control in various industrial and research settings. With advanced technology and excellent customer support, they have become a trusted choice in the field of silica analysis.
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