Effect of AlN and Al2O3 additions on the phase relationships and morphology of SiC Part I Compositions and properties |
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Authors: | Greg E. Hilmas Tseng-Ying Tien |
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Affiliation: | (1) Department of Ceramic Engineering, University of Missouri-Rolla, Rolla, MO, 65409-0330;(2) Department of Materials Science and Engineering, The University of Michigan, Ann Arbor, MI, 48109-2136 |
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Abstract: | X-ray diffraction was utilized to follow the transformation from -SiC (3C) to the various -SiC polytypes in the presence of AlN and Al2O3 additives after hot pressing from 1700 to 2100°C. The 2H- and 6H-polytypes of -SiC were the predominate polytypes with additions of only AlN or Al2O3, respectively. The amount of 2H- and 6H-polytypes, and subsequently the microstructural morphology of the SiC materials, were found to be controlled by varying the amount of AlN and Al2O3. Improvements in fracture toughness to 9 MPa- m were achieved with flexural strengths ranging from 600 to 900 MPa. These results suggest that accurate control of the polytypic make-up of SiC-based materials, along with their mechanical properties, can be achieved through AlN and Al2O3 additions. |
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