Abstract:
Aluminum borates synthesized via a precipitation process. Aluminum nitrate and calcium hexaboride (CaB6) as a source of B2O3 were used. Various proportions of aluminum nitrate were mixed with CaB6 powder and to solution of ammonium hydroxide. The resulting mixtures were evaporated and calcined up to 650oC. Porous ceramic with a framework structure of aluminum borate whiskers was in situ synthesized by firing the green compact bodies up to 1400oC under Ar gas avoiding the oxidation of the CaB6. The structure and morphology were investigated by XRD and SEM. The results indicate that whiskers exhibit a well-crystallized structure with an average diameter distribution about 500 nm and lengths ranging from 5 to 8 μm. Porous aluminum borate ceramic consisted of whiskers with a porosity of 9 – 21% for samples sintered up to 1400oC. Increasing the sintering temperature up to 1500oC and CaB6 addition (15wt.%) deteriorated both the flexural strength and modulus of elasticity of the ceramic bodies.