Patent ID: 7332195

Claim:
A method for densifying a porous carbon preform, which method comprises the steps of: (a) providing an apparatus for use in a CVI/CVD furnace, said apparatus comprising a bottom, a top, and an outer wall defining an interior space in the apparatus, and a passive heat distribution element having a mass of at least about 200 kilograms located within said interior space and apart from said wall; (b) charging said apparatus with a plurality of stacks of annular porous carbon preforms, said preforms being separated from one another by spacers; (c) placing said charged apparatus 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 said apparatus for a period of time of from 150 to 900 hours.