engleski

Two-step sintering of alumina with the addition of waste alumina powder

The impact of the two-step sintering (TSS) process on the obtained microstructure of alumina ceramics with and without the addition of waste alumina powder was studied. Alumina samples were formed according to the slip casting method by preparing alumina suspensions with commercial alumina powder (99.9 mass%-Al2O3 content, 0.8 μm average particle size). The second set of alumina suspensions was prepared by mixing up to 20 dwb.% (expressed on a dry weight basis) of waste alumina powder with commercial alumina. The waste alumina powder (99.7 mass%-Al2O3 content, 3.4 μm average particle size) was collected after the green machining step in the industrial manufacturing process of alumina ceramics. Except for alumina powders, dispersant Tiron (0.05 dwb.%), binder Polyvinyl alcohol (0.1 dwb.%), sintering additive Magnesium Aluminum Spinel (0.2 dwb.%) were used to prepare stable alumina suspensions. After sintering ceramic green bodies, morphological analyses were performed. The intercept method was applied to determine the average grain size from the obtained SEM images, while sample porosity was calculated based on apparent densities. Furthermore, a comparison of the mechanical properties of alumina samples lacking and containing 20 dwb% of waste alumina powder obtained by TSS is presented. The indentation fracture toughness and Vickers hardness slightly increased compared to alumina samples lacking waste alumina powder. The better mechanical properties of ceramic samples containing waste alumina are a consequence of lower porosity. The reported results suggest the possibility of recycling waste alumina powder in a ceramic material.

two-step sintering, waste alumina powder, recycling

nije evidentirano