| 摘要 |
<p>Process for producing vapour-deposited carbon fibres, wherein a gaseous or vaporized hydrocarbon, carried by a carrier gas, is pyrolysed on a substrate in a passage reactor at a temperature comprised between 950 and 1300oC, in two successives steps, a germination step and a growth step. The process comprises the following steps: a gas mixture is prepared which comprises from 50 to 90% and preferably from 85 to 65% by volume of hydrogen and/or helium and from 10 to 40% and preferably from 15 to 35% by volume of methane. The mixture is circulated in the reactor, on a substrate comprising from 10?-8 to 10-4 g/cm2¿ of a catalyst selected among iron, nickel, cobalt and alloys thereof. The germination and the length growth of carbon fibres are initiated at a temperature t1 stabilized between 950 and 1050oC, with a substantially constant speed of the gas mixture comprised between 10 and 50 centimetres per minute during a time duration comprised between 10 and 90 minutes. The diameter growth of the carbon fibres is initiated at a temperature t2 higher than 1050oC, which may reach 1300oC approximately, with a progressively increasing gas mixture speed. The reactor is cooled under inert gas conditions before extracting the carbon fibres.</p> |
