Accession Number:

ADA277349

Title:

Improved Oxidation Resistance of 3-D Carbon/Carbon Composites

Descriptive Note:

Final rept. 1 Jul 1992-28 Feb 1993

Corporate Author:

PHASEX CORP LEXINGTON MA

Report Date:

1994-01-14

Pagination or Media Count:

39.0

Abstract:

Carbon fiber reinforced silicon carbide matrix composites CSiC were made by a process termed Supercritical Fluid Infiltration. A preceramic polymer, e.g., a polycarbosilane which can pyrolyze to form SiC, is dissolved in a supercritical fluid, the solution conveyed into a tightly woven preform of carbon fiber, and the preceramic polymer caused to deposit in the interstitial volume surrounding the fibers. Subsequent pyrolysis of the polymer forms the SiC matrix and fiber coating. Supercritical propane at conditions of 140 deg C, 4000 psi dissolves polycarbsilane to a concentration level of 30 ww, a level that results on substantial infiltration and deposition of the polymer. The yield of SiC from the parent polymer upon pyrolysis was determined to be about 50 ww the polymer was fractionated using supercritical propane in a process termed increasing pressure profiling, and it was found that some of the low molecular weight fractions gave extremely low yields of SiC 25 whereas some of the high molecular weight fractions yielded over 80 SiC. When the parent polymer was used for the infiltration studies the deposited material was modular in appearance suggesting that the liquid low molecular weight portion of the polymer was predominately and adversely influencing the uniformity.

Subject Categories:

  • Physical Chemistry
  • Polymer Chemistry
  • Laminates and Composite Materials
  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE