Effect of dolomite and spodumene on the performances of andalusite composite ceramics for solar heat transmission pipeline

Andalusite composite ceramics used for solar heat transmission pipeline were fabricated via pressureless sintering from andalusite, PSZ, Suzhou kaolin and talc. The effects of dolomite and spodumene on densification, mechanical properties, phase transformation, microstructure and thermal shock resistance of the composite ceramics were investigated. Results demonstrated that dolomite and spodumene used as flux materials promoted densification greatly, and the lowest sintering temperature of the composite ceramics was decreased significantly by 90–150 °C, comparing with the previous works with the usage of potassium feldspar and albite as flux materials. Introducing an appropriate amount(7 wt%) of spodumene improved thermal shock resistance of the composite ceramics since no cracks formed after 30 thermal shock cycles (air cooling from 1100 °C to RT) with a bending strength increasing rate of 22.41%. XRD patterns indicated that the dominant phases of samples before and after 30 thermal shock cycles were consistently mullite, ZrSiO4 and m-ZrO2, while the content of mullite increased after thermal shock, resulting in the enhancement of bending strength. It is believed that the andalusite composite ceramics can be a promising candidate material for heat transmission pipeline in the solar thermal power generation.