What Is Silane Gas?
Silane gas is a hydride of silicon and is a colorless gas with a peculiar odor.
It is an inorganic compound with the chemical formula SiH4 and a molecular weight of 32.12. The hydride with one silicon (Si) is called silane (also known as monosilane), the hydride with two silicon (Si) is disilane, and the hydride with three silicon (Si) is trisilane.
Uses of Silane Gas
Silane gas is the raw material for the semiconductor silicon and is an important industrial material; it can be used in the chemical vapor deposition of silicon because silane gas decomposes into silicon (Si) and hydrogen (H) at temperatures above 420 ºC.
Compounds in which the four hydrogens of silane gas are replaced by alkoxy and alkyl groups (e.g. (CH3O)3SiCH3) are mainly used for surface treatment of inorganic fillers to improve their dispersion and flowability. Hexamethyldisilazane ((CH3)3SiNHSi(CH3)3) is used for surface treatment of inorganic materials to improve compatibility with organic resins.
Dimethylchlorosilane ((CH3)2SiHCl) is used as a raw material for silylating agents and silane gas coupling agents. They play an important role in linking organic and inorganic materials and are used in various applications, such as pharmaceutical synthesis, synthetic resins, adhesives, and glass fiber.
Furthermore, hydrolysis and polymerization of dimethylchlorosilane yields silicone fluid. Silicone is the general term for materials based on organopolysiloxanes, which are organic groups attached to siloxane bonds (alternating silicon and oxygen bonds forming a polymer).
Silicone polymers have excellent heat resistance, weather resistance, and chemical stability because the siloxane bond is the main backbone. They also have unique interfacial properties, such as water repellency and mold release properties, due to the presence of organic groups (mainly methyl groups CH3).
Polysilane gas, a silicon-based polymer compound, is known as an optoelectronic material for organic photoconductor materials, organic electroluminescence, and organic thin-film solar cells. Polydimethylsilane, a type of polysilane, is used as a raw material for silicon carbide fiber.
Properties of Silane Gas
Silane is quickly oxidized by oxygen in air and decomposes into water (H2O) and silicon dioxide (SiO2). It reacts gradually with water, so it should be handled with care. It has a melting point of -185 °C and a boiling point of -112 °C. It is insoluble in ether, benzene, chloroform, and ethanol.
Other Information on Silane Gas
1. How to Make Silane Gas
Trichlorosilane (SiHCl3), which is mainly produced by the reaction of metallic silicon (Si) with hydrochloric acid (HCl), is disproportionated using a catalyst to yield dichlorosilane (SiH2Cl2), tetrachlorosilane (SiCl4), monochlorosilane (SiH3Cl), and a mixture of silanes. Silane gas is then produced by purification and separation through distillation.
Other known industrial methods for the production of silane gas include the reduction of chlorosilane and tetraethoxysilane ((CH3CH2O)4Si), the reaction of magnesium silicide (Mg2Si) with ammonium salts, and the disproportionation of trialkoxysilane (RO3SiH).
2. Handling and Storage of Silane Gas
Silane gas is extremely flammable and combustible and can ignite spontaneously when exposed to air. It can also decompose by heating or combustion, producing silicon and hydrogen, posing a fire or explosion hazard. Therefore, it is important to store them away from ignition sources, such as heat and sparks, oxidizers, oxygen, explosives, halogens, compressed air, acids and bases.
Containers should be sealed and stored locked in a well-ventilated area at temperatures below 40°C (104°F), away from direct sunlight and fire. Also, because of the risk of skin irritation, strong eye irritation, and respiratory irritation, appropriate protective gloves, protective eyewear, and protective masks should be worn when handling, and only in well-ventilated areas.