Process for producing an improved boron nitride crucible

Details Process for producing an improved boron nitride crucible Process for producing an improved boron nitride crucible

1976-02-05

1977-11-15

Gwinnell, Harry J.

Plastic and nonmetallic article shaping or treating: processes

Gas or vapor deposition of article forming material onto...

427248B, 427248J, C23C 1108

Patent

active

040585794

ABSTRACT:
A boron nitride crucible, suitable for the vaporization of aluminum, having a multi-walled structure comprising an outer wall and a thinner inner wall weakly bonded to the thicker outer wall. Because of this structure, the crucible is considerably more flexible than conventional single-walled crucibles and exhibits substantially improved thermal cycling characteristics and longer life. The crucible is produced by depositing pyrolytic boron nitride upon a mandrel having the shape of the desired crucible at a temperature of from about 1850.degree. C. to about 2100.degree. C. until a first layer of boron nitride of suitable thickness has been produced, interrupting the deposition of boron nitride upon the mandrel and lowering the temperature to below 1750.degree. C., and then depositing additional boron nitride upon the mandrel at a temperature of from about 1850.degree. C. to about 2100.degree. C. to produce a second outer layer of boron nitride having a thickness greater than that of the inner layer. The steps may be repeated at least one additional time so as to deposit at least one additional layer of boron nitride upon the second boron nitride layer.

REFERENCES:
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patent: 3152006 (1964-10-01), Basche
patent: 3226194 (1965-12-01), Kuntz
patent: 3367826 (1968-02-01), Heestand et al.
patent: 3549411 (1970-12-01), Bean et al.
patent: 3576932 (1971-04-01), Biddulph
patent: 3609829 (1971-10-01), Carrell et al.

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