Abstract
Recycling alumina powder was used to prepare sintered alumina. Virgin alumina samples were fabricated by atmospheric sintering and were crushed into powder under 500μm in grain size by thermal shock treatment and automatic mortar crushing. Then, the crushed alumina powder was mixed with virgin alumina powder and was subjected to re-sintering to renewed alumina. The renewed alumina samples were subjected to four-point bending test and SEM observation of microstructure. Relative density and bending strength of renewed alumina decreased as the volume fraction of recycled alumina powder increased. Samples over 200MPa of average bending strength, however, were obtained by mixing 50vol% recycled alumina powder with grain size<32μm, which was much larger than that of virgin alumina powder. SEM observation indicated that pore distribution was inhomogeneous and pores were located along large polycrystal grain boundaries. Pores, consequently, formed cracks which markedly decreased bending strength. Furthermore, 10vol%-glass containing renewed alumina samples were fabricated by a procedure similar to that of monolithic alumina. These samples showed higher bending strength than monolithic renewed alumina.
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