Ceramic Processing Through Colloid Chemical Technique

本报告讨论了pH值和盐浓度对氧化铝、氧化铝-二氧化硅和氧化铝-氧化锆水悬浮液中粉末分散的影响，以及用滑铸法制备的绿色压坯的结构。氧化铝颗粒的分散与pH和盐浓度有关。由分散良好的悬浮液制成的绿色压坯具有密度高、孔径小、烧结性能好等特点。在pH值为3 ~ 8之间的悬浮液中，由于异混凝，氧化铝和二氧化硅颗粒之间的相互作用很强，阻碍了氧化铝和二氧化硅颗粒的分离，尽管绿色压实物密度较低。在pH = 2的悬浮液中形成氧化铝颗粒包覆二氧化硅颗粒的复合颗粒。由于复合颗粒的分散性好，获得了组分分布均匀、密度高的绿色致密体。氧化铝和氧化锆颗粒在由分散良好的悬浮液制成的绿色合同中分离。pH大于7的悬浮液形成的绿色压实物均匀性好于pH较低的悬浮液，但压实物由各组分的团聚体组成。在pH = 4.5的悬浮液中加入适量的盐，使氧化锆颗粒之间形成网状结构，阻止了氧化铝颗粒的沉降，形成均匀的绿色压块。

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.