Polycrystalline silicon carbide having bubbles therein and an apparent density of 2.20 g/cm3 or less. This silicon generates an extremely small amount of fine grains by crushing and can be easily crushed. There is also provided a method of producing foamed polycrystalline silicon carbide. There is further provided a polycrystalline silicon production apparatus in which the deposition and melting of silicon are carried out on the inner surface of a cylindrical vessel, a chlorosilane feed pipe is inserted into the cylindrical vessel to a silicon molten liquid, and seal gas is supplied into a space between the cylindrical vessel and the chlorosilane feed pipe.
Polycrystalline silicon carbide is usually produced by gas vapor deposition in a Siemens reactor. This involves depositing high-purity silane or chlorosilane on a hot substrate, so that solid rods, ingots or slabs are obtained. Before this polysilicon can be used in crystallization processes, it must be comminuted. This usually causes it to be contaminated by abraded matter, with the result that the contaminants on the surface have to be removed by cleaning methods.
Polysilicon that can be used directly in the crystallization processes (i.e. without subsequent cleaning) and is suitable for solar applications, i.e. is very pure could until now only be obtained by laborious, personnel-intensive manual comminution. In a first step, a silicon rod, as obtained from a Siemens depositing reactor, was pre-crushed with a hand hammer and subsequently post-comminuted to the required size of fragments by hand with a riveting hammer. This manually produced coarse crushed material could be further comminuted mechanically by feeding it to a machine.
Polycrystalline silicon carbide crusher is crushed with a minimum of manual and machine crushing steps by utilizing a large diameter roll crusher, the circumferential crushing surface of which is formed of a plurality of reversibly mounted, close fitting hard metal plates. Reproducible crushing along with such low metal contamination that subsequent cleaning of the crushed polysilicon is not necessary are both obtained.
A single roll crusher for comminuting high purity materials includes a roll with teeth spaced around the circumference of the roll. The roll is rotatably mounted inside a housing. The housing has a top with an entrance port, sides, and bottom with an exit port. The roll, teeth, and at least the inside surfaces of the top, sides, and bottom are fabricated from a material of construction that minimizes contamination of silicon. The material of construction may be tungsten carbide with a cobalt binder. The single roll crusher is used for polycrystalline silicon carbide crusher.