Annealing effect on the structural and optical properties of Cr/α-Cr 2 O 3 monodispersed particles based solar absorbers

A cost-effective and environmentally friendly green chemical method, the so-called aqueous chemical growth (ACG) method, was used to deposit chromium/alpha-chromium(III) oxide, Cr/α-Cr 2 O 3 , monodispersed particles, for solar absorbers applications. The deposited particles were annealed at various temperatures in a hydrogen atmosphere for 2 h to study the annealing temperature dependence of the structural, chemical and optical properties of the particles grown on tantalum substrates. The deposited Cr/α-Cr 2 O 3 was characterized by X-ray diffraction (XRD), attenuated total reflection (ATR), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and diffuse reflectance UV-vis-NIR spectroscopy. The XRD and ATR analysis indicated that by increasing annealing temperature, the particles crystallinity was improved and Ta 2 O 5 was formed around 600°C, due to the fast oxygen diffusion from the deposited α-Cr 2 O 3 toward the tantalum substrate. The optical measurements show that samples annealed at 400 and 500°C exhibit the targeted high absorbing optical characteristics of "Black chrome", while those annealed below 400°C and above 500°C show a significant low absorptivity and high emissivity. Copyright © 2012 Published by Elsevier B.V. All rights reserved.