Pressure slip cast processing of alumina (Al ₂ O ₃ ) products and comparative evaluation of mechanical properties

Pressure Slip Casting (PSC) using polymer moulds offers several advantages over Conventional Slip Casting (CSC) of ceramics such as enhanced productivity in combination with higher green density, homogeneity and low rejections. PSC is currently practiced in table-ware industries however, application to the technical ceramics is limited owing to the collapse of cast part while de-moulding during pressure cast cycle under pneumatic pressure. Current study focuses on this key issue and demonstrated pressure casting process successfully for the fabrication of alumina parts. Slips of a mixture of alumina with different particle sizes in the various proportions and solid loadings were prepared. Slip under PSC resulted in effective interlocking of the particles retaining the shape while de-moulding and achieved a sintered density of 98.6% of theoretical density (TD). Slurry on CSC exhibited a lower sintered density of 97% of TD. Selection of particles with sizes in optimised proportion for PSC results in effective interlocking of particles in green parts as well as grains on sintering as revealed by the microstructure. This leads to higher density and mechanical properties. Slip thus optimised were shaped into solid spheres of ϕ 60 mm by PSC targeting grinding applications.