Ceramic Processing Through Colloid Chemical Technique

本文研究了pH值和盐浓度对粉末在氧化铝、氧化铝-二氧化硅和氧化铝-氧化锆水悬浮液中分散性的影响，以及用注浆法制备的压坯的结构。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备的生坯具有密度高、孔径小、烧结性好的特点。氧化铝和二氧化硅颗粒之间的强相互作用是由于在pH值为3-8的悬浮液中发生的异凝作用造成的，并阻止了氧化铝和二氧化硅颗粒的分离，尽管生坯的密度较低。在pH=2的悬浮液中形成了包覆有二氧化硅颗粒的氧化铝复合颗粒，复合颗粒分散性好，获得了成分分布高度均匀、密度较高的绿色致密颗粒。氧化铝和氧化锆颗粒在由分散良好的悬浮液制成的绿色悬浮体中分离。PH>7的悬浮液比低pH值的悬浮液获得了更均匀的绿色压坯，但压坯是由各组分的团聚体组成的。在pH值为4.5的悬浮液中加入适量的盐，可在氧化锆颗粒之间形成网状结构，阻止氧化铝颗粒的沉积，形成均匀的绿色压坯。

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.