Synthesis and microstructural characterization of aluminum borate whiskers

Porous ceramic with a framework structure of aluminum borate (9Al2O3·2B2O3) whiskers was in situ synthesized by firing above 1150 °C a green powder compact of a mixture of aluminum hydroxide, boric acid and an additive of nickel oxide. During sintering, the whiskers of aluminum borate grew in situ in the compact, and were bonded together. The porous aluminum borate consisted solely of whiskers with a porosity of 54–58%. The average diameters of the whiskers increased from 0.2 to 2 μm with increasing sintering temperature from 1150 to 1350 °C. However, the estimated whiskers aspect ratio decreased with increasing sintering temperature.