PREPARATION OF γ-Al2O3 NANOCRYSTALLITES BY SOL-GEL AUTO COMBUSTION PROCESS AND PRODUCTION OF Al-Al2O3 ALUMINUM MATRIX COMPOSITES

The gamma-Al2O3 nanocrystallites were synthesized successfully by combination of sol-gel auto-combustion process and ultrasonic method. The overall process involves three steps: formation of homogeneous sol at 50 degrees C; formation of dried gel at 90 degrees C, and experiments revealed that Al2O3 dried gel derived from glycine (as fuel) and nitrates sol exhibits self propagating combustion at 400 degrees C that it is ignited in air. After auto-combustion process, the Al2O3 nanopowders were calcined at 1100 degrees C. Also, aluminum alloy matrix composites reinforced with 0.75 and 1.5 vol.% gamma-Al2O3 nanoparticles were fabricated via stir casting method. Fabrication was performed at 850 degrees C temperatures. The resulting composites were tested for their nanostructure and present phases. Based on the obtained results, optimum amount of reinforcement and casting temperature were determined by evaluating the density, hardness and compression tests of the composites.