Fabrication of porous spinel (MgAl2O4) from porous alumina using a template method

A porous spinel body was fabricated from porous alumina using a template method. First, alumina with 72.5% porosity was fabricated by heating a compact from platelets at 1400 °C for 1 h. The resultant porous alumina was then immersed in an 8 mol/L magnesium nitrate solution, dried, and reheated at 1400 °C for 2 h to convert it to spinel. If necessary, this solution immersion and reheating treatment was performed up to five times. The influence of the number of treatments on the porosity, conversion ratio to spinel, compressive strength, and thermal conductivity was investigated. After five solution treatments, the conversion ratio to spinel was calculated to be approximately 30% in molar ratio, while the remaining majority maintained the morphology of the original alumina platelets. The porosity, compressive strength, and thermal conductivity of the final sample at room temperature were 61.0%, 13.0 MPa, and 1.8 Wm−1K−1, respectively.