In-situ synthesis and thermal shock resistance of cordierite/silicon carbide composites used for solar absorber coating

Cordierite/silicon carbide (SiC) composite ceramics with 10, 20 and 30 wt% cordierite were in-situ prepared via pressureless firing technique using silicon carbide, alumina, Kaolin and talc as starting materials. The results show that the synthesized composites all exhibited the good physical and mechanical properties. Among those, A2 composite with 20 wt% in-situ cordierite fired at 1280 °C exhibited the better bending strength and thermal shock resistance. The improvement of thermal shock resistance could be attributed to the proper cordierite wrapped around SiC, the homogeneous distribution of pores, the well-grown grains, as well as the formation of some glass phase. During the thermal shock test, a small amount of glass phases generated from the oxidation of SiC could react with Al2O3 and MgO, and then more cordierite was formed due to the incorporation of nucleating agent TiO2. With in-situ cordierite content rising, both absorptance and emittance of composite reduced, but A2 composite had the better absorbing ability for the solar energy. It is believed that these in-situ cordierite/SiC composites should be a promising candidate to apply in the field of solar absorber coating owing to the better thermal shock resistance and absorptance of solar energy.