Effect of AlN and Al2O3 additions on the phase relationships and morphology of SiC Part I: Compositions and properties

摘要

X-ray diffraction was utilized to follow thetransformation from β-SiC(3C) to the various α-SiC polytypesin the presence of AlN and Al2O3 additives after hot pressing from1700 to 2100℃. The 2H-and 6H-polytypes of α-SiC were thepredominate polytypes with additions of only AlN or Al2O3,respectively. The amount of 2H- and 6H-polytypes, andsubsequently the microstructural morphology of the SiC materials,were found to be controlled by varying the amount of AlN andAl2O3. Improvements in fracture toughness to ~9Mpa-m1/2 wereachieved with flexural strengths ranging from 600 to 900Mpa.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.