• Sequeira, Sara
• Monteiro, R. C. C.

Abstract

The effect of two sintering methods (conventional sintering and two-step sintering) and of alumina addition on the sintering behaviour of a ZnO-rich waste powder (ZnO > 95 wt%), a by-product from brass smelting industry, was studied aiming to improve the sintered density and grain size. Both conventional sintering and two-step sintering methods did not lead to fully dense powder compacts, as densification was conditioned by abnormal grain growth and the particle size of the ZnO-rich residue. When two-step sintering was used the grain growth was reduced comparatively to conventional sintering method. The highest relative sintered density (about 90%) was achieved when samples of ZnO waste and samples of ZnO waste with 2 wt% added Al2O3 were processed by two-step sintering and corresponded to a mean grain size of around 18 µm and 7 µm, respectively. XRD and SEM results indicated that alumina addition helped to inhibit grain growth due to the formation of gahnite spinel (ZnAl2O4) precipitates in the grain boundaries of zincite (ZnO) grains. ; preprint ; published

Topics

• density
• surface
• grain
• grain size
• scanning electron microscopy
• x-ray diffraction
• composite
• precipitate
• porosity
• ceramic
• sintering
• densification
• grain growth
• brass