Patent ID: 7959973
Filing Date: 2011-06-14
Classification: C04B,C23C

Abstract:
1. A method of chemical vapor infiltration of a deposable carbon material into a porous carbon fiber preform in a reaction zone, the method comprising: situating the porous carbon fiber preform in the reaction zone; providing a linear flow of a reactant gas comprising deposable carbon material in the reaction zone at an initial reaction pressure of at most 50 torr to produce deposition of the deposable carbon material into the preform; and adjusting the pressure of the gas to reaction pressures lower than said initial reaction pressure while deposable carbon material continues to be deposited into the porous carbon fiber preform, wherein gas infiltration pressure during the chemical vapor infiltration is lowered at a rate defined by the formula where P(t) is the gas infiltration pressure in torr, N is a number from 10 through 50 corresponding to the initial gas infiltration pressure, “e” is a the natural logarithm base, “t” is elapsed time since the start of the CVI/CVD process, “T” is the empirically-determined time at which infiltration gas diffusion rate rather than infiltration gas pressure begins to control the rate of density increase in the chemical vapor infiltration of the particular carbon fiber preform being densified, and n is a number 0<n<N corresponding to a degree of lowering of gas infiltration pressure during deposition of deposable carbon material into the porous carbon fiber preform.