| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1989: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1988: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
This report deals with the effects of pH value and salt concentration on the dispersion of powders in alumina, alumina-silica and alumina-zirconia aqueous suspensions and the structure of green compacts made by slip- casting of the suspensions.
1. The sispersion of alumina particles depended on pH and salt concentration. The green compacts made from well-dispersed suspensions had high density, small pore-size and good sinterability.
2. Strong interaction between alumina and silica particles was caused by heterocoaguration in the suspensions of pH between 3 and 8, and prevented separation of alumina and silica particles, although the green compacts had low densities. Composite particles, in which alumina particles were coated by silica particles, were formed in the suspension with pH = 2. Green compact with highly homogeneous component distribution and high density was obtained because of good-dispersibility of the composite particles.
3. Alumina and zirconia particles separated in the green coripacts made from well-dispersed suspensions. The suspensions with pH larger than 7 gave green compacts with better homogeneity than those with low pH, but the compacts were composed of agglomerates of each component. The suitable amounts of salt in the suspension with pH = 4.5 resulted in the formation of network structure between zirconia particles, which prevented sedimentation of alumina particles, leading to the formation of homogeneous green compacts.
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