COMPACTION AND SINTERING BEHAVIOR OF A HIGH-PURITY ALUMINA POWDER TREATED WITH COUPLING AGENTS

Compaction and sintering behavior of a high purity alumina powder (>99.99%) treated with aluminate (A), silane (S) and titanate (T) coupling agents were investigated. The surface treatment increased the green density of pressed-bodies, the effectiveness of the coupling agents on the density increase being S (57.2%) > T (56.4%) > A (53.9%) >non-treated (51.4%) at 2 wt% addition. Microstructure development after firing for 2h at 1600-degrees-C was considerably dependent on the types of metals contained in coupling agents. Alumina treated with 2 wt% of aluminate (Al) exhibited uniform and fine grains similar to the non-treated system. Grain growth and densification were enhanced in the alumina treated with 2 wt% of titanate (Ti) and columnar grains were formed in the alumina treated with 2 wt% of silane (Si). Both bending strength and fracture toughness decreased by the addition of coupling agents. Intragranular fracture was observed in the alumina treated with 2 wt% of silane although intergranular fracture was prominent in other systems.