Patent ID: 7892646

Claim:
A process for densifying porous structures comprising: assembling a multitude of porous structures and ring-like spacers in a stack with a ring-like spacer between each adjacent pair of porous structures; disposing, in a furnace defining an outer volume, the stack of porous structures between a bottom plate and a top plate in the furnace, wherein the bottom plate, the stack of porous structures, and the ring-like spacers define an enclosed cavity extending from the bottom plate, including each porous structure aperture, and terminating proximate the top plate; providing at least one channel for fluid communication between the enclosed cavity and the outer volume; performing a one cycle, pressure gradient CVI/CVD process comprising: introducing a gas composition into the enclosed cavity; allowing a portion of the gas composition to flow through the channel while maintaining a pressure gradient between the enclosed cavity and the outer volume; and providing the gas composition in the outer volume at an initial pressure of at least about 15 torr, wherein a porous structure of the stack of porous structures is densified from an average density of less than about 0.60 g/cm 3 to an average density of greater than 1.70 g/cm 3 in the one cycle.