Ceramic Processing Through Colloid Chemical Technique

本文研究了pH值和盐浓度对粉体在氧化铝、氧化铝-二氧化硅和氧化铝-氧化锆水悬浮液中的分散性的影响，以及由这些悬浮液注浆成型的绿色坯体的结构.氧化铝粒子的分散度取决于pH值和盐浓度。由分散良好的悬浮液制备的绿色坯体密度高、孔径小、烧结性好.氧化铝和二氧化硅颗粒之间的强相互作用是由在pH 3和8之间的悬浮液中的异凝聚引起的，并且防止氧化铝和二氧化硅颗粒的分离，尽管绿色压坯具有低密度。在pH = 2的悬浮液中形成其中氧化铝颗粒被二氧化硅颗粒包覆的复合颗粒。由于复合颗粒的良好分散性，获得了成分分布均匀、致密度高的绿色压坯.氧化铝和氧化锆颗粒分离的绿色coripacts从分散良好的悬浮液。pH值大于7的悬浮液得到的绿色压块比pH值低的压块均匀，但压块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，可使氧化锆颗粒间形成网状结构，防止氧化铝颗粒的沉降，从而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.