Anorthite-cordierite based binary ceramics from coal fly ash and steel slag for thermal and dielectric applications

Abstract

Studying the effects of cordierite crystallization with the anorthite phase, by benefiting from its high mechanical strength and good thermal performance, can hold promise for more practical applications of anorthite-cordierite based binary ceramics. Coal fly ash and steel slag were used as the main starting materials in the prospect of waste management. The effects of the cordierite precursor addition to that of the anorthite, in the range of 25–75 wt%, on the temperature-microstructure evolutions as well as the physical, mechanical, electrical, and thermal properties of the heated anorthite-cordierite materials were investigated. The results revealed that the addition of cordierite precursors to that of anorthite, in the range 25–75 wt%, inhibited the gehlenite formation and enhanced anorthite-cordierite crystallization at 1200 °C. When the amount of cordierite precursor was 25 wt%, the compressive strength decreased from 40 to 20 MPa, while the increase in the cordierite precursor addition up to 75 wt% improved the mechanical strength and reached 80 MPa. The obtained anorthite-cordierite based ceramics exhibited a thermal conductivity of 0.6–0.93 W/m.K and a heat capacity of 1.04–1.39 MJ/m.K, along with high mechanical strength, which promoted their applications for thermal insulator and thermal storage. The dielectric constant measurements (ε = 6–9 at 1 MHz) indicated that the anorthite-cordierite based ceramics from coal fly ash and steel slag can be useful for electronic applications.