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Feng J.,Shandong University | Feng J.,CAS Shanghai Institute of Ceramics | Zhang S.,Shandong University | Lu Y.,Shandong University | And 11 more authors.
Solar Energy | Year: 2015

Spectrally selective TiAlN/TiAlSiN/Si3N4 multilayer coatings were deposited on stainless steel (SS) plate using a reactive direct current magnetron sputtering technique. In this tandem absorber system, TiAlN, TiAlSiN and Si3N4 act as the main absorbing layer, the semi-absorbing layer and the antireflection layer, respectively. An average absorptance (α) of 0.938 and emittance (ε) of 0.099 were achieved in coatings prepared under optimized conditions, which exhibit a fine-grained morphology and an amorphous microstructure as evidenced by SEM and XRD analysis, respectively. Absorptance and emittance data, as well as Raman spectra were collected for coatings exposed to different levels of thermal stresses (2h in air @200°C, 300°C, 400°C, 500°C, 600°C). These heat treated coatings showed negligible to small degradations in their selective absorbing capabilities as compared with the as-grown ones. There was no significant change of the coatings in their morphology or composition after the heat treatments, as evidenced by the SEM and Raman spectra analysis, respectively. The spectral selectivity of the coatings remained stable after a heat-treatment at 272°C in air for 300h. © 2014 Elsevier Ltd.

Feng J.,Shandong University | Feng J.,CAS Shanghai Institute of Ceramics | Feng J.,Shandong Solar Energy Corporation | Zhang S.,Shandong University | And 6 more authors.
Vacuum | Year: 2015

TiN/TiSiN/SiN solar selective absorbing coatings (SSACs) with and without a copper underlayer were deposited on stainless steel (SS) substrates via dc reactive magnetron sputtering. In this SSAC, SS/Cu or SS, TiN, TiSiN and SiN act as the metal reflector layer, high metal volume fraction layer, low metal volume fraction layer and anti-reflection layer, respectively. An absorptance (α) of 0.95 and a total hemispherical emittance (ε (70 °C)) of 0.04 were achieved in coatings with Cu underlayer. On the other hand, the SS/TiN/TiSiN/SiN SSAC showed a similar absorptance (∼0.95) but a poorer emittance and solar selectivity. X-ray diffraction analysis showed that the Cu layer is polycrystalline, while TiN, TiSiN and SiN are amorphous. The chemical-bonding states of each layer of the TiN/TiSiN/SiN SSAC were analyzed by using X-ray photoelectron spectroscopy. The solar selective absorbing performance of the Cu/TiN/TiSiN/SiN SSAC did not show significant changes after they were heat-treated in vacuum up to 700 °C. Raman spectra and atomic force microscopy images were collected to illustrate the structural and morphological stabilities of this SSAC upon heating in vacuum. Lastly, heat treatments in air for 150 and 300 h based on the PC nomenclature were carried out to demonstrate long term thermal stability of SS/TiN/TiSiN/SiN. © 2015 Elsevier Ltd.

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