| 摘要 |
Apparatus such as a furnace muffle ( 11 ) for use in a CVI/CVD furnace. The apparatus includes a bottom ( 12 ), a top ( 13 ), and an outer wall ( 3 ) defining an interior space ( 1 ) in the apparatus, and a passive heat distribution element ( 7, 9 ) located within the interior space ( 1 ) and apart from the outer wall ( 3 ). Preferably, the bottom ( 12 ) and top ( 12 ) include perforated plates and the outer wall ( 3 ) is cylindrical in shape and all are made of graphite or carbon-carbon composite material and the passive heat distribution element ( 7, 9 ) is cylindrical in shape and includes graphite or carbon-carbon composite discs having no spacers therebetween. Also, a method for densifying a porous carbon preform ( 5 ), which method includes the steps of: (a) providing the apparatus ( 11 ); (b) charging the apparatus ( 11 ) with a plurality of stacks of annular porous carbon preforms ( 5 ), the preforms being separated from one another by spacers ( 15 ); (c) locating the charged apparatus ( 11 ) in a furnace at a temperature in the range of 950-1100° C. and a pressure in the range of 5-40 torr; and (d) circulating a natural gas reactant blended with up to 15% propane through the apparatus for 150-900 hours. Also, a batch of carbon-carbon composite preforms made by the method, wherein the density of the batch of preforms is at least 0.5 g/cc higher than the density of a batch of preforms made by an otherwise identical process in which the apparatus does not contain a passive heat distribution element located within its interior. The preforms may be configured as aircraft landing system brake discs or racing car brake discs.
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