Modification of high temperature radiation absorption properties of solid particles with surface coating

Abstract

The coatings with different thermodynamic and optical properties can adjust and improve the overall performance of solid particles in solid particle solar receivers (SPSRs). In this work, the manganese iron black (PBK26) coating is prepared by water bath method and comprehensive performance of the coating is found to be the best when Fe/Mn molar ratio in PBK26 is 4:1. The high temperature radiation absorption performances of different solid particles coated by PBK26 are investigated. The results show that the spectral absorptivity of particles can be greatly improved by coating. The average spectral absorptivity of quartz sand, bauxite and mullite increases by 25.9%, 20.8% and 16.2%, respectively. However, the coated quartz sand appears coating shedding phenomenon at high temperatures, and the coating on bauxite is not complete. Only the coated mullite shows excellent coating effect and thermal stability. After long-period high temperature thermal stability experiments at 900 °C and cyclic thermal stability experiments of 30 cycles, the maximum mass loss of coated mullite is less than 0.4% and the spectral absorptivity is almost unchanged. In the wear resistance experiments the surface debris of the coated mullite increases. And there is a mass loss of 8.244% with a coating thickness loss of 27% and a spectral absorptivity decrease of 3.88% after 10 h of wear at 900 rpm. The results imply good high temperature thermal stability and acceptable wear resistance of PBK26 coated mullite, which provide an option for high temperature radiation improvement of solid particles.