Oxidation of Non-Oxide Ceramics.
Annual rept. Apr 80-Apr 81,
CASE WESTERN RESERVE UNIV CLEVELAND OHIO DEPT OF METALLURGY AND MATERIALS SCIENCE
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Tracer studies involving CVD single crystals oxidized in oxygen 16 and oxygen 18 were unsuccessful in indicating the direction of diffusing species during oxidation of SiC. A refinement of this technique is planned. Research is also continuing on the characterization of the spherulitic growth which appears during oxidation. The influence on densification of pore curvature, dihedral angle, applied stress and internal pore pressure was undertaken from a theoretical point of view. The results using a simple model indicate that at low dihedral angle less than 60 degrees there is an equilibrium porosity in a polycrystalline material for such a material there is no barrier to nucleation of cavities in dense material. At intermediate dihedral angles, pores with few sides would shrink and disappear, whereas those with many sides would initially shrink but would reach an equilibrium size at which densification would stop. In this case grain growth of the large pores would reduce the number of sides for the pore and promote further densification. For such materials there would be a small barrier to nucleation. Author
- Physical Chemistry
- Ceramics, Refractories and Glass