Preparation of mullite sol and mullite sol coated aluminum titanate powder

The stable mullite sol with different performances was prepared by the sol-gel method using tetraethyoxysilane(TEOS) and aluminium nitrate as main materials. Aluminium titanate(AT) powders were covered by mullite sol using the dipping film-coating method. The influences of performance and relative amount of mullite sol on the coating effect and improvement of performance of AT powders were researched. The results show that when the concentration of mullite sol is in the range of 0.18~0.30mol/L, viscosity of mullite sol 56~93mPa · s, pH value 3.0, and coating thickness 0.15~0.20μm, the mullite-aluminum titanate powder with better coating and mullite-aluminum titanate composite material with good performance can be obtained. The bending strength of mullite aluminum titanate composite material reaches 38~50MPa, which is 10~15 times that of aluminum titanate material, and the thermal expansion coefficient is 1.89~2.25×10^-6/℃(room temperature to 1000℃). The aluminium titanate powders covered with mullite film do not decompose at 1100℃ for 300h.The heated process and the feature of aluminium titanate before or after coating the film, and its compositions were investigated by TG-DSC, XRD, SEM, EPMA, etc. The relationships between performances and structure of the powders and the composite material of mullite-aluminum titanate were studied.