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US 3,947,562 AGranted
Production of a form of alumina whiskers
AssigneeHepworth & Grandage Limited
InventorsRex William Grimshaw, John Gilleran Peacey
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AssigneeHepworth & Grandage Limited
InventorsRex William Grimshaw, John Gilleran Peacey
Estimating the term…
The invention relates to the production of alumina whiskers from alumina-bearing material by preparing an intimate mixture of such material and carbon and then passing a stream of gaseous aluminium trihalide and an inert carrier gas thereover in a first zone at an elevated temperature, usually 1400.degree.C to 1800.degree.C, at which reaction occurs to form aluminium monohalide and carbon monoxide. The gaseous stream comprising the two latter materials is then passed to a second zone maintained at a less elevated temperature than the first zone, usually 1400.degree.-1000.degree.C, at which temperature the reaction is reversed to produce a gaseous stream carrying alumina and carbon. Under conditions of low supersaturation the alumina deposits as single crystal alumina whiskers from which any carbon can be removed by an oxygen-containing gas at temperatures of 800.degree.-1000.degree.C.
A process for the production of alumina whiskers comprising contacting an intimate mixture of particulate alumina-bearing material and a particulate form of carbon with a stream of gaseous aluminium trihalide in a first reaction zone maintained at an elevated temperature at which reaction occurs to form aluminium monohalide and and carbon monoxide, transporting the gaseous products comprising said monohalide and carbon monoxide to a second reaction zone maintained at a lower temperature than said first reaction temperature, this said lower temperature being one at which reversal of the reaction which has occurred in said first reaction zone occurs with formation of a gaseous stream supersaturated with respect to alumina under the conditions prevailing in the second reaction zone and deposition of the desired whisker form of alumina.
A process for the production of alumina whiskers which comprises the steps of contacting an intimate mixture of particles of alumina-bearing material and particles of carbon with a gaseous stream comprising a mixture of aluminium trihalide vapour and an inert carrier gas in a first reaction zone maintained at an elevated temperature of at least 1400.degree.C at which temperature reaction occurs to form a gaseous mixture comprising the corresponding aluminium monohalide and carbon monoxide, transporting said gaseous mixture to a second reaction zone maintained at a less elevated temperature than said first reaction zone but above 1000.degree.C at which latter temperature the reaction which has taken place in said first reaction zone is reversed with formation of alumina and carbon so as to obtain a gaseous mixture containing a low supersaturation of alumina and deposition of alumina takes place from said mixture in the desired whisker form.
Dependencies are inferred from the claim text.