Accession Number : ADA309358

Title :   Strength Degrading Mechanisms for CVD SCS-6 SiC Fibers in Argon Environments.

Descriptive Note : Technical memo.,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER

Personal Author(s) : Bhatt, Ramakrishna T. ; Hull, David R.

PDF Url : ADA309358

Report Date : MAY 1996

Pagination or Media Count : 20

Abstract : The room temperature tensile strengths of chemically vapor deposited SCS-6 silicon carbide fibers were measured after 1 to 400 hr heat-treatments in 0.1 MPa argon at temperatures to 2100 deg C. The fibers heat treated for 1 hr above 1400 deg C and those heat treated for 400 hr above 1300 deg C showed strength degradation. Scanning and transmission electron microscopic examination of the degraded fibers showed formation of a recrystallization region within the outer zone of the SiC sheath and the growth of SiC particles in the carbon-rich surface coating. The activation energies for the growth of the recrystallization region and the SiC particles were approx. 370 KJ/mole and approx. 320 KJ/mole, respectively. Strength of the fibers was found to vary as an inverse function of the recrystallized zone thickness.

Descriptors :   *DEGRADATION, *CHEMICAL VAPOR DEPOSITION, *STRENGTH(MECHANICS), *ARGON, *SILICON CARBIDES, SCANNING, METALS, THICKNESS, FIBERS, TENSILE STRENGTH, ENVIRONMENTS, CERAMIC MATRIX COMPOSITES, FIBER REINFORCED COMPOSITES, CARBON, ROOM TEMPERATURE, ELECTRON MICROSCOPY, TRANSMITTANCE, PARTICLES, EXTERNAL, INVERSION, HEAT, RECRYSTALLIZATION, ACTIVATION ENERGY.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Ceramics, Refractories and Glass
      Crystallography
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE