Patent GB-1271291-A (GB)
Title: Method and apparatus for making fibres
Inventor: GLASS JOHN P
IPC: C30B25/00
Filed: 1969-04-01
Abstract: 1,271,291. Growing whiskers from gaseous phase. J. P. GLASS. 1 April, 1969, No. 17088/ 69. Heading B1F. [Also in Division Cl] In making fibres or whiskers e.g. of carbon, alumina, boron carbide, or silicon carbide, a vapour stage of fibre forming material is introduced into a chamber 11 and condensed on a substrate 22 of whiskers or fibres supported within the chamber whilst the parts of the fibre projecting into the chamber are electrostatically charged so that they are separated and individually exposed to the vapour, the fibres or whiskers being gathered together at a constraining position, e.g. bush 21, spaced from the ends of the fibres so as to form a strand which is withdrawn from the chamber. The capacitance of the growing fibres is measured with the aid of electronic bridge 35 and an appropriate circuit, and the variation of such capacitance is used to control the whisker formation by controlling either the speed of the withdrawal on to pulley 26, or the rate of vaporisation of the whisker forming material when such is achieved by means of the vaporiser 33 positioned within the chamber or by controlling the operation of valve 38 which is adapted to admit cooling vapours or the vapours of whisker forming materials into conduit 37 for admission via inlets 54 in to the chamber. It is preferred that the fibres are charged oppositely to deposition vapour, and the chamber may contain means e.g. discharge element 51, vibrator 52 and emitter 53 to encourage growth of the fibres or whiskers at the growing tips. In Fig. 2 (not shown) a single chamber is equipped with a multiplicity of withdrawing point and strand winding reels. In Fig. 4 the strand is withdrawn from the base of the chamber, the strand being supported in bushing 239 spaced from the base, the bunch 249 of fibres being supported in an erect position by the electrostatic charging of partition member 225. A number of bunches are supported side by side so that the proximity of the adjacent bunch prevent any bunch spreading too widely and kinking the fibre at the bushing. The growing zone 221 is heated by elements 257 but the thimble 233 encloses a cooler section through which fibre forming material is introduced before passing to the deposition chamber. Reaction gases produced in the reaction chamber may be recycled via the hollow partition 243, using pump 247 the recycle gas being fed into chamber 221 by orifices 241. Air may be admitted from upper section 223 by vents 227 in portion member 225. This air may be preheated (Fig. 5 not shown) by being passed through a column of heated stones supported in the chamber 223. A bed of cooled stones also supported in a further section of chamber 223 may be heated by exhaust gases from 221 exiting through certain vents 227. The two beds are thus used alternately for preheating air. In growing carbon fibres, methane is used as the starting material being cracked at 700- 900‹C to form C+hydrogen which is recycled to improve the characteristics of the product. The ratio of H 2  to CH 4  in the mixture used may be from 5:1 to 20:1. The reaction vapour may also contain oxygen.