Process for producing unagglomerated single crystals of aluminum

Details Process for producing unagglomerated single crystals of aluminum Process for producing unagglomerated single crystals of aluminum

1990-05-25

1992-03-17

Dixon, Jr., William R.

Compositions: ceramic

Ceramic compositions

Refractory

501 86, 501153, 423137, 423363, 156600, 1566205, C04B 3558

Patent

active

050968602

ABSTRACT:
A process for producing unagglomerated single crystals of aluminum nitride having a size of at least 10 microns suitable for the reinforcement of metal and ceramic matrix composite materials. The process involves reacting alumina (or a precursor) with carbon under an atmosphere of nitrogen (or a precursor such as ammonia or an amine) at a temperature in the range of 1800.degree.-1950.degree. C. in the presence of an alkaki metal oxide (or precursor such as a carbonate) as a crystal growth promoter or catalyst. The alkali metal oxide is present in an amount required for the formation of crystals of the required size, preferably in the range of 10-60 microns. Particularly desirable crystals are produced if electrostatic precipitator dust is used as a source of the alumina, if petroleum coke or calcined anthracite coal is used as a source of the carbon and if the reaction is carried out in the presence of a porosity enhancer for the reaction mass, especially short cellulose fibres. The particles produced by the invention are in the form of large single crystals for good matrix reinforcement and may have low oxygen and carbon contents. The invention extends to the particles produced by the process and to matrix composites reinforced with the particles.

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patent: 4869925 (1989-09-01), Hiai et al.
patent: 4908173 (1990-03-01), Schwetz et al.

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