Pressure Slip Casting: A Novel Process for Producing Alumina Bodies with Superior Green Density

摘要

Shaping of alumina (Al_2O_3) green bodies through conventional slip casting (CSC) and pressure slip casting (PSC) processes has been comparatively evaluated. Cast samples with an external pressure of 30-35 bar exhibited green densities in the range of 60-61 % in comparison.to 49-52 % of the theoretical densities obtained with conventional slip cast processing. Higher green densities in the case of PCS specimens can be attributed to the electrostatically engineered slurry that undergoes particle to particle interlocking in the isostatic compressive stress field. High strength polymer moulds in combination with unique pore characteristics tolerate high operating pressures (~40 bar), which in turn results in a manifold increase in the casting rate in comparison to capillary suction driven CSC with POP moulds. Further, PCS green specimens exhibited water content as low as 10-12 % against CSC samples with 20-25 %, permitting instant deformation free demoulding. Higher green density in combination with low water content in the PCS bodies has the advantages of higher green strength, better handleability, low shrinkage, easy complex shaping and minimum dimensional distortion on further heat processing. Cast samples were further sintered and characterized for their sintered properties and microstructure.