PREPARATION OF NANO-STRUCTURAL Al۲O۳-TiB۲ IN-SITU COMPOSITE USING MECHANICALLY ACTIVATED COMBUSTION SYNTHESIS FOLLOWED BYINTENSIVE MILLING

Abstract: Nano-structural synthesized materials can be fabricated utilizing intensive milling after combustion synthesis. The Al۲O۳-TiB۲ ceramic composite has been synthesized by aluminothermic reactions between Al, Ti (TiO۲), and B (B۲O۳ or H۳BO۳). Boric acid (H۳BO۳) is less expensive than boron oxide, and after being dehydrated at ۲۰۰°C, boron oxide will be obtained. In this study, Al, TiO۲, and boric acid were used as the starting materials to fabricate an Al۲O۳-TiB۲ ceramic composite. After mechanical activation and thermal explosion processes, intensive milling was performed for ۵, ۱۰, and ۲۰h to assess the formation of a nano-structural composite. The X-ray phase analysis of the as-synthesized sample showed that considerable amounts of the remained reactants incorporated with the TiO phase were present in the XRD pattern. The results showed that the average crystallite size for alumina as a matrix were ۱۵۰, ۵۵ and ۳۳ nm, after ۵h, ۱۰h, and ۲۰h of intensive milling, respectively. The SEM microstructure of the as-milled samples indicated that increasing the milling duration after combustion synthesis causes a significant reduction in the particle size of the products, which leads to an increase in the homogeneity of particles size. A significant increase in the microhardness values of the composite powders was revealed after intensive milling process.