Processing of Concentrated Aqueous Silicon Nitride Slips by Slip Casting

Abstract

The optimization of concentrated Si 3 N 4 powder aqueous slurry properties to achieve high packing density slipcast compacts and subsequent high sintered densities was investigated. The influence of pH, sintering aid powder (6% Y 2 O 3 , 4% Al 2 O 3 ), NH 4 PA dispersant, and Si 3 N 4 oxidative thermal treatment was determined for 32 vol% Si 3 N 4 slurries. The results were then utilized to optimize the dispersion properties of 43 vol% solids Si 3 N 4 -sintering aid slurries. Calcination of the Si 3 N 4 powder was observed to result in significantly greater adsorption of NH 4 PA dispersant and effectively reduced the viscosity of the 32 vol% slurries. Lower viscosities of the optimized dispersion 43 vol% Si 3 N 4 -sintering aid slurries resulted in higher slipcast packing density compacts with smaller pore sizes and pore volumes, and corresponding higher sintered densities.

Dense and near-net-shape fabrication of Si3N4 ceramics

“…This result implies that further addition of the dispersant beyond a certain level had no more measurable contribution to the interfacial charge of the powder because the adsorbent dispersant layers on powder surfaces are saturated. Other authors, for example Albano and Garrido [123] and Liu and Malghan [124] who used other experimental methods obtained similar results to the obtained by He et al [120] who concluded that the minimum viscosity (greatest degree of dispersion) occurred at 1 wt% Darvan dirpersant.…”

Dispersion of TiN in aqueous media

“…According to the dispersion of Si 3 N 4 particles [40][41][42][43][44][45], acrylic-type polymer is usually reported as dispersant for TiN in aqueous media [46,47]. However, based on the XPS results and pH IEP , a cationic polymer, PEI, is selected in this paper.…”

Fabrication of stable Al2O3 slurries and dense green bodies using soft-energy milling process

“…[1][2][3][4][5] It is known that a good dispersion of ceramic particles in an aqueous medium is very important to form homogeneous structure of green bodies. In general, ball milling and planetary ball milling are used to prepare ceramic slurries.…”