Fabrication of transparent MgAl2O4 ceramics by gelcasting and cold isostatic pressing

摘要

Highly transparent MgAl2O4 ceramics have been fabricated by aqueous gelcasting combined with cold isostatic pressing (CIP), pressureless sintering and hot isostatic pressing (HIP) from high purity spinel nanopowders. The gelling system used AM and MABM as monomer and gelling agent. The influences of dispersant and PH on the Theological behavior of the MgAl2O4 slurries were investigated. The spinel slurry with low solids loading (25 vol %) and low viscosity (0.15 Pa s) was obtained by using 6 wt% Duramax-3005 (D-3005) as dispersant. After CIP, the green body had a relative density of 48% with a narrow pore size distribution. The influence of sintering temperature on densification and microstructure was studied, choosing 1500 degrees C as the sintering temperature. After HIP (1650 degrees C/177 MPa/5 h), transparent MgAl2O4 ceramic with the thickness of 3 mm was obtained, whose in-line transmittance was 86.4% at 1064 nm and 79.8% at 400 nm, respectively. The ceramic exhibited a dense microstructure with the average grain size of 23 mu m. The Vickers hardness and flexure strength of the sample reached 13.6 GPa and 214 MPa, respectively.