Patent GB-1410090-A (GB)
Title: Reinforced carbon structures
IPC: C04B35/83
Filed: 1973-03-21
Abstract: 1410090 Reinforced carbon artefacts UNITED KINGDOM ATOMIC ENERGY AUTHORITY 26 March 1974 [21 March 1973] 13707/73 Heading C1A A reinforced carbon artefact consisting of a resin-bonded and carbonized or graphitized multilayer structure in which each layer comprises either bundles of aligned carbon fibres, woven carbon tape, or carbon felt, the structure containing one or more fibre bundle layers and one or more woven tape and/or felt layers assembled so that the bundle layers alternate with tape or felt layers or with contiguous tape and felt layers, the outermost layers of the structure being either both bundle layers, both tape layers or both felt layers may be made by one of two methods. In the first, a multilayer structure as described above is impregnated with a curable resin, the structure is shaped, the resin is cured, and the cured structure is heated in a non-oxidizing atmosphere to carbonize it. In the second, bundles of aligned carbon fibres are assembled side by side with their fibre axes in alignment and impregnated with a liquid comprising a heat-curable resin (which term includes coal tar pitch), a woven carbon tape and/or a carbon felt are similarly impregnated, and the liquid-impregnated bundles and the liquidimpregnated tape and/or felt are partially cured by heating to convert the liquid therein to a mass of viscosity sufficient that the bundles adhere together; cut lengths are made of the partially cured bundles, felt and/or tape and are then stacked to form a multilayer structure as described above, the layers each consisting of one or more bundle lengths, one or more felt lengths or one or more tape lengths; the stacked structure is then shaped, heated to hard-cure the resin, and heated in a non- oxidizing atmosphere to carbonize it. Either process may be followed by a further heating in a non-oxidizing atmosphere to graphitize the carbonized structure. Prior to the second process, the fibre bundles, woven tape and felt may be treated (either by heating in air or by immersion in a solution of an oxidizing agent) to surface-oxidize the fibres; as an alternative to, or following, surface oxidation the fibres may be surface-treated by immersion in a solution of a compound containing an element which will form a carbide on the surface of the fibres. In the second process, the stacked structure is preferably shaped by compression moulding, and the shaping pressure is preferably maintained through the hard-curing stage. The resin used in the second process may have dispersed therein carbon black or graphite in the form of a powder; and the second process may be followed by vacuum impregnation of a further quantity of the resin-containing liquid into the carbonized structure, whereafter the artefact is subjected to pressure, heated to hard-cure the newly introduced resin, and then heated in a non- oxidizing atmosphere to carbonize the cured resin; alternatively, or in addition, carbon may be deposited from the vapour phase within the pores of the structure prior to any graphitizing heat treatment, preferably by pyrolysis of a hydrocarbon. The artefact may be further heated in air after the hard-curing stage of the second process in order to substantially eliminate volatile materials without substantial loss by oxidation.