Dense shaped articles consisting of polycrystalline hexagonal bo

Details Dense shaped articles consisting of polycrystalline hexagonal bo Dense shaped articles consisting of polycrystalline hexagonal bo

1982-12-29

1985-01-22

Parrish, John A.

Plastic and nonmetallic article shaping or treating: processes

Treatment of material by vibrating, jarring, or agitating...

264325, 264332, 501 96, C01B 2106

Patent

active

044951230

ABSTRACT:
The invention is a shaped article of boron nitride having a density of at least 95% of the theoretical density which consists of polycrystalline hexagonal boron nitride in the form of a homogeneous isotropic microstructure and which has been manufactured from pure boron nitride powder without the concomitant use of sintering aids by isostatic hot-pressing in a vacuum-tight casing at temperatures of from about 1200.degree. to 1500.degree. C. under a pressure of from about 50 to 300 MPa. Boron nitride powders having a free boric oxide content of not more than 1.0% by weight and having a specific surface area of from 5 to 30 m.sup.2 /g are used as starting material. The powders either are filled into prefabricated casings consisting of steel or glass and densified by vibration or are preshaped to form green bodies having pores open to the surface and then placed in prefabricated casings or coated with a material which forms a vacuum-tight casing. The powders or the preshaped green bodies in the vacuum-tight casings are then subjected to an isostatic hot-pressing process in a high-pressure zone using an inert gas such as argon or nitrogen, as the pressure-transfer medium.

REFERENCES:
patent: 3455682 (1969-07-01), Barbaras
patent: 3469976 (1969-09-01), Iler
patent: 3513229 (1970-05-01), Asbury
patent: 3562371 (1971-02-01), Bush
patent: 3734997 (1973-05-01), Mandorf
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patent: 4023966 (1977-05-01), Loersch
Chemical Abstracts, vol. 97, 1982, p. 258, No. 43 096 f: Mattsson et al., (ASEA AB) Swed. SE 422, publ. Mar. 1, 1982.
Chemical Abstracts, vol. 74, 1971, p. 201, No. 56 893a: Brickway et al., AD 1970, No. 709 620 of Jul. 1970.

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