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Pressureless sintering of whisker-toughened ceramic composites
Abstracts of Patents fibres with lengths of 2.5-5 mm are oriented to within 80-90% of the perpendicular to the long axis of the composite. The remaining fibres are < 2.5 mm long and are randomly oriented. PROCESSES Manufacture of net shaped metal ceramic composite engineering components by selfpropagating synthesis Sekhar, J.A., Bhaduri, S.B., Li, H.P. and Canarslan, N.S. (University of Cincinnati, Cincinnati, OH, USA) US Pat 5 188 678 (23 February 1993) A combustible, titanium-, boron- and coppercontaining substance and at least one ceramic reinforcement are formed into the intended final shape and ignited to produce a distortion-free composite by combustion synthesis; expansion or contraction during the reaction is 7% or less. The Ti:B:Cu ratio in the combustible substance is 61:12:20. The ceramic reinforcement may be a boride of Ti, Zr, Nb, Ta, Mo, Hf, Cr or V; a carbide of Ti, Hf, B, AI, Ta, Si, W, Zr, Nb or Cr; a nitride of Ti, Zr, B, A1, Si, Ta, Hf or Nb; a silicide of Mo, Ti, Zr, Nb, Ta, W or V; an oxide of Fe, AI, Cr or Ti; or a phosphide of Ni or Nb. Process for preparing carbon/carbon composite Uemura, S., Sohda, Y., Kato, O., Kuono, T. and Kihara, T. (Nippon Oil Company, Ltd, Tokyo, Japan) US Pat 5 192 471 (9 March 1993) A carbon fibre bundle is impregnated with a nitrogen-containing heterocyclic compound and then carbonized under pressure. Thereafter it may be further carbonized under atmospheric pressure to produce a carbon/ carbon composite. Method of making discontinuous carbon fibre reinforced glass matrix composites with secondary matrix reinforcement Tredway, W.K. (United Technologies Corporation, Hartford, CT, USA) US Pat 5 192 475 (9 March 1993) A glass powder and boron nitride are mixed together in a carrier liquid to form a slurry; a binder is added and a continuous multifilament carbon fibre yarn impregnated with the slurry. The yarn is dried, cut into lengths and suitably moulded to produce a discontinuous carbon fibre-reinforced glass matrix composite. Process for making fluoropolymer composites Logethetis, A.L. (E.I. du Pont de Nemours and Company, Wilmington, DE, USA) US Pat 5 194 484 (16 March 1993) A fibrous material is contacted with an aqueous fluoropolymer dispersion and the fluoropolymer precipitated from the dispersion to form a fluoropolymer structure on the fibrous material. The structure is dried and then consolidated using heat and pressure to form a solid shaped composite article. Process for the production of a ceramic fibre/ matrix composite article Parlier, M., Bouillon, E., Muller, C., Bloch, B., Noireaux, P. and Jamet, J. (Office National D'Etudes et de Recherches Aerospatiales, Chatillon Sous Bagneux, France) US Pat 5 196 235 (23 March 1993) Silicon carbide fibres are impregnated with both discrete ceramic particles and a liquid
polymer that is convertible to a ceramic by pyrolysis. The whole is then heated to produce a silicon carbide-reinforced ceramic matrix composite.
to swell. The swollen reinforcements are placed in contact with a conductive or semiconductive powder to produce a dispersion of reinforcing elements in a matrix.
Investment casting technique for the formation of metal matrix composite bodies and products produced thereby Burke, J.T. (Lanxide Technology Company, LP, Newark, DE, USA) US Pat 5 197 528 (30 March 1993) An investment shell is formed and a barrier material is placed in at least a portion of the cavity within the shell. A non-reactive filler is also placed in the cavity; this filler is brought into contact with and infiltrated by a molten matrix metal up to the barrier material (either the filler or the metal contains an infiltration enhancer). The whole is then cooled to produce a shaped metal matrix composite body.
Fibre-reinforced composite material process for the production thereof Inata, H., Matsumura, S. and Yoshitomi, T. (Teijin Limited, Osaka, Japan) US Pat 5 223 335 (29 June 1993) A composition of a substantially linear aromatic oligomer with a terminal aliphatic hydroxyl group, bis(acylcaprolactum) and tetraalkoxy titanium catalyst is melted and used to impregnate a fibrous reinforcing material. The whole is then heated so that the caprolactum ring is opened, thereby forming a fibre-reinforced composite with a matrix composed of a thermoplastic copolymer with an ester group and an amide group in its main chain.
Process for producing carbon fibre reinforced materials Mochida, I. and Fujiura, R. (Mitsubishi Gas Chemical Company, Inc., Tokyo, Japan) US Pat 5 205 888 (27 April 1993) A carbon fibre assembly is impregnated with a mesophase pitch that contains almost 100% of an optically anisotropic phase and which has a softening point of 350~ or below. The impregnated assembly is shaped and then fired at between 600 and 1500~ in a nonoxidizing atmosphere to produce the carbon/ carbon composite which can optionally be graphitized at a temperature between 2000 and 3000~
Ceramics composite article and method for making same Matsuda, T., Saitoh, S., Yonezawa, T., Sakai, C. and Abe, H. (Japan Metals & Chemicals Co., Ltd, Tokyo, Japan) US Pat 5 227 344 (13 July 1993) A slip containing 5-30 vol% whiskers and a ceramic powder in a disperson is slip cast and the resultant green body dried to at least 60% density. The green body is sintered in a non-oxidizing atmosphere to produce the ceramic composite article.
Pressureless sintering of whisker-toughened ceramic composites Tiegs, T.N. (Martin Marietta Energy Systems, Inc., Oak Ridge, TN, USA) US Pat 5 207 958 (4 May 1993) A homogeneous mixture, comprising 10-20 wt% SiC whiskers with an aspect ratio of at least 50, 1040 wt% yttria, 0.1 1 wt% MgO with the balance being alumina, is milled for between 16 and 32 h. After milling the average aspect ratio of the SiC whiskers is between 10 and 20. The mixture is shaped and pressed to 50% density. It is then heated in an inert atmosphere at between 1750 and 1800~ to produce a 94% dense composite by liquid phase sintering. Method for moulding resin reinforced with fibre and mouldings produced Ebisawa, H., Kohama, K., Abe, T., Takizawa, H., Atobe, D. and Ueda, K. (Honda Giken Kogyo Kabushiki Kaisha, Tokyo and Nippon Shokubai Kagaku Kogyo Co., Ltd, Osaka, both of Japan) US Pat 5 211 893 (18 May 1993) The viscosity of a sheet comprising thermosetting resin and fibres is modified in regions which would otherwise produce undesirable variations in thickness during moulding. The sheet is then moulded by heat and pressure to produce a fibre-reinforced composite with a reduced tendency of having variations in wall thickness. Process for coating fibres and applications thereof to the production of composite materials Berger, M. (Pradom Limited, London, UK) US Pat 5 218 012 (8 June 1993) A composite material is produced by subjecting reinforcing elements (preferably fibres) to an electric field which causes them
Synthesis of metal matrix composites containing flyash, graphite, glass, ceramics or other metals (Rohatgi, P.K. of Milwaukee, WI, USA) US Pat 5 228 494 (20 July 1993) A metal matrix material is heated until it melts and is then stirred using an impeller whilst reinforcing particles of graphite, fly ash, oil ash or hollow microspheres are added to the melt. The mixture is poured into a mould whilst it is still being stirred at /> 1000 rev min J, to ensure that there is an even distribution of less dense reinforcing particles throughout the denser matrix. Process for making coated ceramic reinforcement whiskers Devore, D.D. (The Dow Chemical Company, Midland, MI, USA) US Pat 5 230 061 (27 July 1993) This coating process for mullite whiskers reduces the bonding between the whiskers and a matrix when the whiskers are incorporated into a ceramic matrix. The process comprises mixing the whiskers with one of a hydrocarbon solvent, an ether, an alcohol or tetrahydrofuran and an organometallic coating precursor; evaporating the solvent under vacuum; and then pyrolysing the precursorcoated whiskers to produce whiskers with a non-particulate ceramic coating on them. Method of providing a gating means, and products thereby Langensiepen, R.A., Aghajanian, M.K., Wiener, R.J., Kennedy, C.R. and Rocazella, M.A. (Lanxide Technology Company, LP, Newark, DE, USA) US Pat 5 240 062 (31 August 1993) A permeable mass of filler or a preform body is separated from a source of molten matrix metal by a gating means. The gating means comprises at least one riser of sufficient length and diameter to allow directional solification and/or isolation of thermal
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polymer that is convertible to a ceramic by pyrolysis. The whole is then heated to produce a silicon carbide-reinforced ceramic matrix composite.
to swell. The swollen reinforcements are placed in contact with a conductive or semiconductive powder to produce a dispersion of reinforcing elements in a matrix.
Investment casting technique for the formation of metal matrix composite bodies and products produced thereby Burke, J.T. (Lanxide Technology Company, LP, Newark, DE, USA) US Pat 5 197 528 (30 March 1993) An investment shell is formed and a barrier material is placed in at least a portion of the cavity within the shell. A non-reactive filler is also placed in the cavity; this filler is brought into contact with and infiltrated by a molten matrix metal up to the barrier material (either the filler or the metal contains an infiltration enhancer). The whole is then cooled to produce a shaped metal matrix composite body.
Fibre-reinforced composite material process for the production thereof Inata, H., Matsumura, S. and Yoshitomi, T. (Teijin Limited, Osaka, Japan) US Pat 5 223 335 (29 June 1993) A composition of a substantially linear aromatic oligomer with a terminal aliphatic hydroxyl group, bis(acylcaprolactum) and tetraalkoxy titanium catalyst is melted and used to impregnate a fibrous reinforcing material. The whole is then heated so that the caprolactum ring is opened, thereby forming a fibre-reinforced composite with a matrix composed of a thermoplastic copolymer with an ester group and an amide group in its main chain.
Process for producing carbon fibre reinforced materials Mochida, I. and Fujiura, R. (Mitsubishi Gas Chemical Company, Inc., Tokyo, Japan) US Pat 5 205 888 (27 April 1993) A carbon fibre assembly is impregnated with a mesophase pitch that contains almost 100% of an optically anisotropic phase and which has a softening point of 350~ or below. The impregnated assembly is shaped and then fired at between 600 and 1500~ in a nonoxidizing atmosphere to produce the carbon/ carbon composite which can optionally be graphitized at a temperature between 2000 and 3000~
Ceramics composite article and method for making same Matsuda, T., Saitoh, S., Yonezawa, T., Sakai, C. and Abe, H. (Japan Metals & Chemicals Co., Ltd, Tokyo, Japan) US Pat 5 227 344 (13 July 1993) A slip containing 5-30 vol% whiskers and a ceramic powder in a disperson is slip cast and the resultant green body dried to at least 60% density. The green body is sintered in a non-oxidizing atmosphere to produce the ceramic composite article.
Pressureless sintering of whisker-toughened ceramic composites Tiegs, T.N. (Martin Marietta Energy Systems, Inc., Oak Ridge, TN, USA) US Pat 5 207 958 (4 May 1993) A homogeneous mixture, comprising 10-20 wt% SiC whiskers with an aspect ratio of at least 50, 1040 wt% yttria, 0.1 1 wt% MgO with the balance being alumina, is milled for between 16 and 32 h. After milling the average aspect ratio of the SiC whiskers is between 10 and 20. The mixture is shaped and pressed to 50% density. It is then heated in an inert atmosphere at between 1750 and 1800~ to produce a 94% dense composite by liquid phase sintering. Method for moulding resin reinforced with fibre and mouldings produced Ebisawa, H., Kohama, K., Abe, T., Takizawa, H., Atobe, D. and Ueda, K. (Honda Giken Kogyo Kabushiki Kaisha, Tokyo and Nippon Shokubai Kagaku Kogyo Co., Ltd, Osaka, both of Japan) US Pat 5 211 893 (18 May 1993) The viscosity of a sheet comprising thermosetting resin and fibres is modified in regions which would otherwise produce undesirable variations in thickness during moulding. The sheet is then moulded by heat and pressure to produce a fibre-reinforced composite with a reduced tendency of having variations in wall thickness. Process for coating fibres and applications thereof to the production of composite materials Berger, M. (Pradom Limited, London, UK) US Pat 5 218 012 (8 June 1993) A composite material is produced by subjecting reinforcing elements (preferably fibres) to an electric field which causes them
Synthesis of metal matrix composites containing flyash, graphite, glass, ceramics or other metals (Rohatgi, P.K. of Milwaukee, WI, USA) US Pat 5 228 494 (20 July 1993) A metal matrix material is heated until it melts and is then stirred using an impeller whilst reinforcing particles of graphite, fly ash, oil ash or hollow microspheres are added to the melt. The mixture is poured into a mould whilst it is still being stirred at /> 1000 rev min J, to ensure that there is an even distribution of less dense reinforcing particles throughout the denser matrix. Process for making coated ceramic reinforcement whiskers Devore, D.D. (The Dow Chemical Company, Midland, MI, USA) US Pat 5 230 061 (27 July 1993) This coating process for mullite whiskers reduces the bonding between the whiskers and a matrix when the whiskers are incorporated into a ceramic matrix. The process comprises mixing the whiskers with one of a hydrocarbon solvent, an ether, an alcohol or tetrahydrofuran and an organometallic coating precursor; evaporating the solvent under vacuum; and then pyrolysing the precursorcoated whiskers to produce whiskers with a non-particulate ceramic coating on them. Method of providing a gating means, and products thereby Langensiepen, R.A., Aghajanian, M.K., Wiener, R.J., Kennedy, C.R. and Rocazella, M.A. (Lanxide Technology Company, LP, Newark, DE, USA) US Pat 5 240 062 (31 August 1993) A permeable mass of filler or a preform body is separated from a source of molten matrix metal by a gating means. The gating means comprises at least one riser of sufficient length and diameter to allow directional solification and/or isolation of thermal
COMPOSITES Volume 26 Number 1 1995
77