Study On Colloidal Forming Of High Performance Ceramics By Starch In-situ Consolidation

The in-situ consolidation forming technology is one of the hotspots of the research on high performance ceramics. To achieve in-situ consolidation forming of Al₂O₃ ceramics, the gelling network formed by swelling and gelatinization of starches or modified starches in heat uptake was used in this paper. The optimal technological parameters were achieved after the investigation on the effects of technological parameters, such as starches or modified starches content, dispersant content, solid volume loading, time of ball milling, etc. on the rheological behavior of ceramics slurry, the structure and character of formed green body, and by orthogonal experiments. The consolidation forming mechanism of alumina slurry containing starch was further studied based on the investigation of the effects of different kinds of starches or modified starches on the rheological behavior of alumina slurry and capability of formed bodies.The gelatination properties of starches or modified starches, including gelatinized temperature, viscosity and thermal stability of paste, and the ability of gel formation, etc. are greatly influenced by species of starch and modified methods. Some factors, such as concentration, temperature, pH value and dispersant, obviously affect the viscosity of starches or modified starches paste. The research of gelling properties provides a foundation that aim to the application of starch or modified starch in the in-situ consolidation forming of high performance ceramics, and will also probe further into the effect of starches and modified starches on the capability of formed bodies. Thereinto, gelatinized temperature of starch is the key factor which decides the consolidation formed temperature of alumina slurries.By researching on the dispersibility and stability of ceramics slurry, the optimal condition for the preparation of ceramics slurry with high dispersion, high stabilization and high solid volume loading by using alumina powder with different average particle size, is obtained. The result shows that the optimal pH ranges are 8.5⁹.5, 8.0⁹.0 and 10.0¹2.0 for average particle size of 2.47μm, 0.63μm and 0.15μm respectively. And the corresponding optimal dosages of dispersant are 0.03⁰.05%, 0.2% and 0.5% respectively.The research on rheological behavior of ceramic slurries is the base of successively casting for different shape ceramics parts and obtaining high performance ceramic products. The apparent viscosity of alumina slurries increases with the increment of acetate starch content and solid volume loading. The...