Effects of agglomerates on the sintering of alpha-Al 2O 3

Abstract

Alumina powder was consolidated by slipcasting of suspensions with pH between 2 and 9, and then fired under various time-temperature conditions. The effects of agglomerates on the pore structure in green compacts and on the microstructure development during sintering were studied. An increase in the pH value of the suspension from 2 to 9 increased the agglomerate size in the suspension, resulting in an increase in both pore size and pore volume in green compacts. The sintering behavior was studied for the compacts made from the suspensions of pH = 2 and 9. The pH = 2 compact densified faster than the pH = 9 compact, without any significant difference in the microstructure development, which was characterized by the formation of well-sintered regions during the early stage of sintering (density < 75%), followed by the development of a uniform grain structure (75% < density < 95%) and columnar grains during grain growth achieve a specific microstructure more so for the pH = 9 compact than for pH = 2 because of larger pore size in the green state.