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Introduction of asbestos for electric light sources
Asbestos, also known as asbestos fiber, is a general term for certain silicate minerals that can be split into elastic fibers. It contains a certain amount of water. It is characterized by being loose, smooth and having a fibrous structure. According to the mineral composition, it can be divided into two categories: amphibole asbestos and serpentine asbestos. In vacuum technology, the most important is serpentine asbestos, which is composed of 44% SiO2, 44% MgO and 12% crystal water, and usually contains some iron oxide components.
Asbestos is chemically inactive. It is acid-resistant, alkali-resistant and heat-resistant, and is a poor conductor of heat and electricity, which is very important for vacuum technology. When asbestos is heated to 100°C, it will lose 7% of its weight (mostly surface adsorbed water). Serpentine fiber will also precipitate its crystal water at 400°C, and its strength will decrease. The density of asbestos is 2.1~2.8g/cm, the melting point of amphibole asbestos is 1150°C, and the melting point of serpentine asbestos is 1550°C.
Longer fibers are used to make fireproof textiles, such as asbestos rope, asbestos tape, asbestos cloth, etc.; shorter fibers are used to make asbestos insulation materials, asbestos cement products and insulation materials for low-voltage electrical appliances, etc.
In the production of electric light sources, asbestos is mainly used for heat insulation and heat preservation purposes, such as asbestos cloth, asbestos gloves and asbestos rope for high-temperature operation, exhaust table ovens and glass annealing furnace linings; asbestos paper is used for the interlayer of some discharge lamp caps.
Asbestos fiber dust is harmful to human health, so it is necessary to take precautions during production and use to avoid inhalation.
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