Preparation and Properties of Co-Cr3C2-WC/Al2O3 Solar Selective Absorbing Coatings

SHAO Hao, ZENG Xian, LI Qing-yu, LIU Fu-sheng, LIU Tong-zhi, CHENG Xu-dong

Surface Technology ›› 2020, Vol. 49 ›› Issue (6) : 138-145.

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PDF(3696 KB)
Surface Technology ›› 2020, Vol. 49 ›› Issue (6) : 138-145. DOI: 10.16490/j.cnki.issn.1001-3660.2020.06.016
Surface Functionalization

Preparation and Properties of Co-Cr3C2-WC/Al2O3 Solar Selective Absorbing Coatings

  • SHAO Hao, ZENG Xian, LI Qing-yu, LIU Fu-sheng, LIU Tong-zhi, CHENG Xu-dong
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Abstract

The work aims to study the spectral emission and absorption properties of different Co-Cr3C2-WC absorbing layers and prepare Al2O3 anti-reflection films on the surface of the absorbing layer to obtain a novel mid-high temperature cermet-based solar selective absorbing coating. The Co-Cr3C2-WC absorbing layers were deposited on the stainless steel by high velocity oxygen-fuel spraying technology (HVOF), and the components were optimized. The Al2O3 anti-reflection films were then prepared on the surface of the absorbing layer by Sol-Gel method. The phase composition, elemental valence and micro-structure of the coatings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), separately. The root mean square roughness was measured by a surface roughness meter. The spectral reflectance of the coatings in the UV-Vis-NIR and far infrared bands was measured by Fourier infrared spectrometer and UV-Vis-NIR spectrophotometer, respectively. 90Co-5Cr3C2-5WC (wt.%) absorbing layer had the highest quality factor (α/?=0.805/0.308). In addition, the absorptance of the coating increased to 0.903, and the emittance decreased to 0.278 after Al3O2 anti-reflection films were added on the surface. The coating surface was dense and uniform and the roughness was reduced to 1.109 μm. After 100 hours of heat treatment at 750 ℃ in air, the absorptance of the coating increased to 0.910 and the emittance was 0.315, indicating stable selective absorption performance. The 90Co-5Cr3C2-5WC absorbing layer effectively improves the surface state of the thermal sprayed coating and reduces the emittance of the absorbing layer while maintaining a high absorption performance. The Al2O3 anti-reflection film further improves the absorptance of the composite coating by increasing the transmittance of short-wave light and sealing effect, thus enhancing the selective absorption and high-temperature serviceability. Therefore, such coating is expected to be used as a selective absorbing coating in mid-high temperature solar collector system.

Key words

Co-Cr3C2-WC/Al2O3; selective absorbing coating; optical performance; thermal stability; high velocity oxygen-fuel spraying; Sol-Gel method

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SHAO Hao, ZENG Xian, LI Qing-yu, LIU Fu-sheng, LIU Tong-zhi, CHENG Xu-dong. Preparation and Properties of Co-Cr3C2-WC/Al2O3 Solar Selective Absorbing Coatings[J]. Surface Technology. 2020, 49(6): 138-145
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