Improving the properties of low temperature sintered alumina bodies with granite reject additions

Abstract

The use of industrial waste materials as additives in the manufacture of ceramic products has been attracting a growing interest from researchers in recent years and is becoming common practice. The continued depletion of natural resources throws a new light on the potential use of some industrial wastes and natural sub-products as full-fledged alternative ceramic raw materials. This work describes the research carried out on the low temperature manufacturing of alumina bodies using, as additive, granite reject as-produced by an ornamental stone processing industry that saws granite stones into blocks and slabs in Rio Grande do Norte, Brazil. This reject is produced in significant amounts and is discarded in sedimentation lagoons, landfill areas or simply thrown in rivers, resulting in environmental pollution. Samples containing up to 30 wt% granite reject and 5 wt% manganese oxide (constant) were uniaxially pressed and sintered in air in an electric furnace (1150-1350 °C, for 1 hour). Sintered test pieces were characterized by X-ray diffraction, apparent density, open porosity and flexural strength. The results showed that the addition of granite reject and manganese oxide enables low temperature sintering and remarkably improves the cold mechanical properties of the alumina body.