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Electric light source material - asbestos

Asbestos, also known as asbestos fiber, is a general term for certain silicate minerals that can break into elastic fibers. It contains a certain amount of water. It is characterized by its looseness, smoothness, and fibrous structure. Based on its mineral composition, it can be divided into two types: hornblende asbestos and serpentine asbestos. Serpentine asbestos is the most important type in vacuum technology. It consists of 44% SiO2, 44% MgO, and 12% water of crystallization, often containing some iron oxide.

Asbestos is chemically inert. It is resistant to acids, alkalis, and heat, and is a poor conductor of heat and electricity, making it crucial for vacuum technology. When heated to 100°C, asbestos loses 7% of its weight (mostly due to surface-absorbed water). Serpentine fibers also release their water of crystallization at 400°C, reducing their strength. The density of asbestos is 2.1-2.8 g/cm3. The melting points of hornblende asbestos are 1150°C and serpentine asbestos are 1550°C.

Longer fibers are used to make fire-resistant textiles, such as asbestos rope, tape, and cloth; shorter fibers are used to make asbestos insulation materials, asbestos cement products, and insulation for low-voltage electrical appliances.

In the production of electric light sources, asbestos is primarily used for thermal insulation and heat preservation. For example, asbestos cloth, gloves, and rope are used for high-temperature operations, exhaust ovens, and glass annealing furnace interior linings; asbestos paper is used as a barrier in the lamp holders of some discharge lamps.

Asbestos fiber dust is harmful to human health, so precautions should be taken during production and use to avoid inhalation.