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arXiv · 2204.06640

Temperature-Dependent Diffuse Reflectance Measurements of Ceramic Powders in the Near- and Mid-Infrared Spectra

J. Michael Mayer·James A. Abraham·Bryan Kinzer·Rohini Bala Chandran
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Abstract

This study focuses on experimentally measuring temperature-dependent diffuse reflectance in the near- and mid-infrared spectra for ceramic particles with applications as heat-transfer and thermal-storage media in concentrated solar power (CSP) plants. Specifically, a commercially available sintered bauxite ceramic powder, ACCUCAST ID80, and its primary chemical constituents, alumina (Al2O3) and silica (SiO2), are measured using a Fourier transform infrared spectrometer (FTIR) coupled with a specialized diffuse reflectance accessory and a heated stage. Room-temperature diffuse reflectance measurements show increased absorption in tests with greater mass fractions of the ceramic samples. There is a strong correlation in the measured reflectance spectra of ACCUCAST with alumina and silica in the spectral range 2000-500 cm-1. For the first time, temperature-dependent diffuse reflectance measurements are reported for ACCUCAST, including a novel technique for accessing reflectance values above the limiting temperature of the background material KBr. All three materials exhibit a calculated emittance of ~0.9 at room temperature. However, this value drops to 0.68 at 1000 C for ACCUCAST and ~0.43 for alumina and silica. Thermal cycling in air from 25 C to 1000 C resulted in a visible color change from dark grey to light orange for ACCUCAST and a subsequent 5X greater increase in reflectance at 4000 cm-1 as compared to ACCUCAST thermally cycled at 1000 C in vacuum. Alumina and silica spectra proved to be largely unaffected by thermal cycling under atmospheric and evacuated conditions.

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J. Michael Mayer, James A. Abraham, Bryan Kinzer, Rohini Bala Chandran. 2022-04-13. Temperature-Dependent Diffuse Reflectance Measurements of Ceramic Powders in the Near- and Mid-Infrared Spectra. https://doi.org/10.1016/j.solener.2022.08.071

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