GB1298043A - Process for the continuous graphitisation of carbon filaments, carbon fibres, carbon fibre strips and carbon yarn - Google Patents

Abstract

1298043 Graphitization of carbon fibres BAYER AG 23 Dec 1970 [27 Dec 1969] 61115/70 Heading C1A [Also in Division H5] A carbon filament, fibre, fibre strip or yarn is continuously graphitized by passing it continuously through a plasma produced by one or more gas discharges having gas temperatures above 1000‹ C., and having substantially symmetrical properties about the line along which the filament is passed. The plasma gas may be one or more noble gases, e.g. argon (to which may be added N 2 , H 2 , NH 3 , CH 4 , C 2 H 2 or C 2 N 2 ) and the plasma may be produced by inductivelycoupled high-frequency discharges, unipolar high frequency or microwave flare discharges or by direct current arc plasma torches (optionally with an A.C. arc) (see Division H5). The filament may be graphitized under tension by using pairs of feed and draw rollers before the inlet and behind the outlet of the plasma chamber. Maximum filament temperature may be below the maximum gas temperature, and may be controlled by adjusting gas pressure, speed, composition and electrical parameters, or by altering filament speed, or by impregnating the filament with a substance vaporizable in the plasma. Such substances are salt melts, aqueous salt solutions, inorganic acids, hydrocarbons, oils, resins, pitch or tar. The process may be operated at 1 to 1000 mm. Hg, preferably atmospheric pressure. In examples, (1) a carbonized fibre strip (6000 individual fibres) is graphitized at 2500-2900‹ C. using 60% Ar, 35% N 2 , 5% H 2 as plasma gas; (2) carbonized polyacrylonitrile strip (5000 fibres) is graphitized at 2400-2600‹ C. using 90% Ar, 5% NH 3 , 5% C 2 H 2 as plasma gas; (3) carbonized polyacrylonitrile strip (3000 fibres) is impregnated with a mixture of diphenylether, diphenyl and benzene before graphitization at 2500-3000‹ C. using pure Ar as plasma gas.