Synthesis of ZrO2 nanoparticle by combination of sol-gel auto-combustion method- irradiation technique, and preparation of Al-ZrO2 metal matrix composites

Nanocrystalline ZrO2 with particle size of about 38 nm was directly synthesized by sol-gel auto-combustion method. The overall process involved three steps: formation of homogeneous sol at 50-55°C; formation of dried gel at 110°C, and combustion of the dried gel at 400°C. Experiments revealed that ZrO2 dried gel derived from glycine (Fuel) and nitrate sol exhibited self propagating combustion at 400°C  that  it was ignited in air. The auto-combustion was considered as a heat-induced exothermic oxidation-reduction reaction between nitrate ions and carboxyl group. After auto-combustion, products were calcined at 650°C. ZrO2 nano particle were incorporated into the A356 aluminum alloy by a mechanical stirred at 850°C and after that, cylindrical specimens were cast. After preparing the samples, mechanical properties were measured. The results of microstructure, compression and hardness tests indicated that addition of ZrO2 nano particulates to aluminum matrix composites improved the mechanical properties. Also, Based on experiments, it was revealed that the presence of ZrO2 reinforcement    led to significant improvement in hardness and compressive strength.