Pressure-pulsed chemical vapour infiltration of pyrolytic carbon to porous carbon preforms or two-dimensional-carbon/SiC particulate preforms from a gas system CH4-H-2-N-2

Pyrolytic carbon (pyrocarbon) was infiltrated to porous carbon preforms or two-dimensionally woven carbon fiber (2D-C)/SiC particulate preforms using pressure-pulsed chemical vapour infiltration from 20-100% CH4 diluted by H-2 or N-2. Pyrocarbon deposited from the gas system CH4-N-2 had a laminar microstructure oriented parallel to the macrosurface of the preform or the surface of the carbon fiber, whereas, laminar structure was not observed clearly in the pyrocarbon from the gas system CH4-H-2. After 4 x 10(4) pulses with a reaction time of 0.4 s per pulse at 1423 K from 50% CH4-H-2 or at 1373 K from 50% CH4-N-2, residual porosity of 2D-C/SiC particulate preforms decreased from 30% to 10%. Flexural strength of 2D-C/SiC particulate preforms increased from 32 to 125 MPa. (C) 1997 Elsevier Science S.A.