Optical properties of solid particle receiver materials. II. Diffuse reflectance of Norton Masterbeads® at elevated temperatures

Abstract

An experimental system to measure the diffuse reflectance of a particulate sample over the wavelength range of 300 to 2500 nm at elevated temperatures up to 1000°C has been developed and implemented. A description of the experimental apparatus and measurement procedures, as well as optical reflectance data for the Masterbeads®, are presented. Using the high temperature measurement system, the diffuse reflectance of Masterbeads® changed by less than 1% for sample temperatures from 150°C to 930°C. However, after heating a sample for three hours at 1000°C in air, the solar absorptance measured at room temperature decreased from an initial value of 0.93 to 0.89. © 1986.