A comparative study of thermal conductivity and thermal emissivity of high temperature solar absorber of ZrO2 /Fe2O3 and Al2O3/CuO ceramics

Abstract

Oxide ceramics are considered as promising high temperature solar absorber materials. The major aim of this work is the development of a new solar absorber material with promising characteristics, high efficiency and low-cost processing. Hence, this work provides a comparative and inclusive study of densification behavior, microstructure features, thermal emissivity and thermal conductivity values of the two new high temperature solar absorbers of ZrO2/Fe2O3 and Al2O3/CuO ceramics. Ceramic composites of ZrO2/(10–30 wt%) Fe2O3 and Al2O3/(10–30 wt%) CuO were prepared by pressureless sintering method at a temperature of 1700 °C/2hrs. Identification of the solar to thermal efficiency of the composites was evaluated in terms of their measured thermal emissivity. Thermal efficiency and heat transfer homogeneity were investigated in terms of thermal conductivity and diffusivity measurement. The results showed that both composites exhibited comparable densification behavior, homogenous and harmonious microstructure. However, Al2O3/10 wt% CuO composite showed higher thermal and solar to thermal efficiencies than ZrO2/Fe2O3 composites. It gave the lowest and the best thermal emissivity of 0.561 and the highest thermal conductivity of 15.4 W/m. K. These values proved to be the best amongst all those of the most known solar absorber materials made from the expensive SiC and AlN ceramics. Thus, Al2O3/CuO composites have succeeded in obtaining outstanding properties at a much lower price than its other competitive materials. These results may strongly identify Al2O3/CuO composites as promising high-temperature solar absorber materials instead of ZrO2 and the other carbide and nitride ceramics.