Shin-etsu Chemical Co., Ltd.

Masanori Fukuhira

Hirofumi Fukuoka

Yoshiharu Konya

Mutsuo Shimizu

Masaki Watanabe

Hiroshi Tsumura

Kazushi Satoh

Nobuhiko Kodana

Isao Watanuki

Hidehiko Aonuma

Hideaki Shimizu

Hidemitsu Ochiai

Ichiro Ishizaka

Silicon nitride powder is continuously prepared by feeding metallic silicon powder into a fluidized bed comprising silicon nitride powder and nitrogen or ammonia gas and discharging a nitrided product from the fluidized bed. The metallic silicon powder is pretreated at a temperature of 1,000.degree.-1,400.degree. C. under a vacuum of 0.001-100 Torr before it is subject to nitriding reaction.

Continuous preparation of silicon nitride powder

In a fluidized bed reactor for preparing a metal nitride by feeding metal powder and a non-oxidizing gas containing N.sub.2 or NH.sub.3 into a reaction tube (1) to form a fluidized bed (2) therein and heating the fluidized bed for nitriding the metal powder, an envelope (11) encloses the reaction tube (1) for preventing the surrounding air from entering the reaction tube. A heater (9) is disposed outside the envelope (11) for heating the fluidized bed (2) to 1,200.degree. C. or higher. The envelope prevents penetration of the surrounding air into the reaction tube and also prevents deterioration of the heater and surrounding components by scattering of metal fines. The reactor ensures safe operation to prepare metal nitride powder of high purity on an industrial scale.

Fluidized bed reactor for preparing metal nitride

Silicon nitride powder is prepared by nitriding metallic silicon powder in a nitriding gas atmosphere at a temperature of 1,000.degree. C.-1,500.degree. C. Midway the nitriding step, the nitrided product is heat treated in an inert non-oxidizing gas atmosphere or vacuum at a temperature higher than the nitriding temperature, but lower than 1,600.degree. C. The product is nitrided again, obtaining high .alpha.-content silicon nitride powder.

Preparation of high alpha-type silicon nitride powder

In a method for preparing a high .alpha.-type silicon nitride powder by adding to and mixing with metallic silicon powder a copper catalyst and nitriding the mixture in a non-oxidizing gas atmosphere containing nitrogen or ammonia at 1,000.degree. to 1,500.degree. C., the amount of copper catalyst is limited to from 0.05 % to less than 0.5 % by weight of copper based on the weight of the metallic silicon. There is obtained silicon nitride powder of high purity at low cost and high efficiency since the copper catalyst can be efficiently removed from the silicon nitride powder through conventional acid treatment.

Preparation of high .alpha.-type silicon nitride powder

Silicon nitride powder is produced in two steps, by supplying metallic silicon powder to a fluidized bed composed of silicon nitride and nitrogen or ammonia gas where primary nitriding reaction is effected until the silicon powder is nitrided to an amount of at least 50% and transferring the nitrided product from the fluidized bed into a moving bed where secondary nitriding reaction is effected for nitriding the unreacted silicon with nitrogen or ammonia gas. This method is adapted for manufacture on a commercial scale because the silicon nitride powder thus obtained is consistent and has a very high degree of nitriding and a minimal variation in quality.

Preparation of silicon nitride powder by partially nitriding in a

A simple but very effective and reliable method is proposed for the decolorizing purification of a halogenated silane compound, e.g., methyl trichlorosilane, colored by containing a very small amount of heavy metal impurities such as iron. The method comprises: contacting the halogenated silane compound with a small amount of a cationic surface active agent which is solid and insoluble in the silane such as a quaternary ammonium salt, e.g., trimethyl octadecyl ammonium chloride, for 2 to 240 minutes; and then separating the silane compound from the cationic surface active agent.

Method for decolorizing purification of halogenated silane

Silicon nitride powder is prepared by continuously supplying metallic silicon powder to a first fluidized bed which is composed of silicon nitride powder and a non-oxidizing reaction gas containing nitrogen or ammonia gas and maintained at 1,000.degree. to 1,400.degree. C. where primary nitriding reaction takes place, and continuously withdrawing the nitride product from the first fluidized bed and supplying it to a second fluidized bed of similar composition where secondary nitriding reaction takes place for nitriding the unreacted metallic silicon powder.

Growing community of inventors

Takasaki, Japan

Masanori Fukuhira