Effects of cold isostatic pressing parameters on mechanical and insulation performances of a 95.5 wt% alumina ceramic

Abstract

The effects of cold isostatic pressing (CIP) pressure on the sintering densification, the mechanical and insulation performances of a 95.5 wt% alumina ceramic are investigated. The density of sintered ceramic increases with the increase of CIP pressure, and tends to level off when the CIP pressure is higher than a suitable pressure (120 MPa). This is attributed to the effect of CIP pressure on the pore size. The fracture strengths of green body and sintered ceramic both increases linearly with the increase of densities, which can be explained by the weakest-link assumption of fracture that initiates from pores. For the sintered ceramics, the direct current (DC) dielectric breakdown strength (DBS) increases exponentially with density, while the alternating current (AC) DBS prepared under different pressures have no noticeable difference, and this may be attributed to it that the large pores can discharge under DC while cannot discharge under AC. This work can contribute to fabricating ceramics with excellent performances on the premise of reducing costs.