Pengjun Ma

Microstructure and Optical Properties of SS/Mo/Al2O3 Spectrally Selective Solar Absorber Coating

Surface-textured Mo thin film is fabricated by magnetron sputtering through the adjustment of deposition parameters, which exhibits a high absorptance of 0.80 and a low emittance of 0.09. The single-layer Mo deposited on stainless steel (SS) is characterized by x-ray diffraction (XRD), ultra-high resolution scanning electron microscope, atomic force microscope and optical measurement. The controlled surface roughness combined with larger aspect ratio contributes much to the high absorptance and low emittance. Based on the SS/Mo coating, a spectrally selective coating (SS/Mo/Al2O3) is designed and fabricated. The coating shows an amorphous structure and exhibits an absorptance of 0.90 and an emittance of 0.08. Tauc-Lorentz and Drude free-electron models are used to modeling the optical properties of Al2O3 and Mo layers by phase-modulated spectroscopic ellipsometry.

Structure, optical properties and thermal stability of SS/TiC–ZrC/Al2O3 spectrally selective solar absorber

A tandem layer structured SS/TiC–ZrC/Al2O3 coating has been prepared by magnetron sputtering as a high temperature spectrally selective solar absorber. The coating consists of two layers; a TiC–ZrC layer and an Al2O3 layer. TiC and ZrC ceramics show inherent spectral selectivity, which is used to design spectrally selective solar absorbers. A co-sputtering technique was used to fabricate the absorptance layer (TiC–ZrC). The coating exhibits a high absorbance of 0.92 and a low emittance of 0.11, as well as good thermal stability with a selectivity of 0.92/0.13 even after annealing at 700 °C for 100 h under vacuum. The SS/TiC–ZrC/Al2O3 coating also shows good thermal stability at 400 °C for 5 h in air. The surface morphology, composition, structure and optical properties of the coating were characterized using SEM, XPS, XRD, Raman spectroscopy, UV-vis-NIR spectrophotometry and Fourier transform infrared spectroscopy. Benefiting from these advantageous features, the as-deposited SS/TiC–ZrC/Al2O3 coating can be a good candidate for concentrated solar power applications.

Enhanced absorptance of surface-textured tungsten thin film for solar absorber

To improve the absorptance and emittance, single layer surface-textured metal tungsten (W) thin film is fabricated by magnetron sputtering through the adjustment of deposition parameters. The surface-textured single layer W thin film exhibits a high absorptance of 0.74 and a low emittance of 0.05 due to the high aspect ratio subwavelength structures. Based on the surface-textured W coating, the SS/W/Al2O3 tandem spectrally selective solar absorber is designed and fabricated. Solar absorptance of 0.90 can be obtained with thermal emittance of 0.06. The surface-textured W and film structural of SS/W/Al2O3 tandem coating may open an new avenue for the spectrally selective solar absorber coating.

Spectrally selective Cu1.5Mn1.5O4 spinel ceramic pigments for solar thermal applications

In this work, Cu1.5Mn1.5O4 spinel ceramic pigments have been successfully prepared by a facile and cost-effective sol–gel self-combustion method and annealed at a temperature ranging from 500 °C to 900 °C for 1 h. The reaction process was discussed in detail through thermal analysis, X-ray diffraction (XRD), and Fourier transformation infrared spectroscopy (FTIR) techniques. The optical properties of the ceramic pigments annealed at various temperatures were also determined from the corresponding diffuse reflectance spectra in the 2.5–20 μm range, which elucidated that optimum spectrally selective paint coatings could be fabricated according to the pre-selection ceramic pigments. Ceramic pigments were utilized to fabricate thickness sensitive spectrally selective (TSSS) paint coatings by means of the convenient and practical spray-coating technique, and TSSS paint coatings based on pigments annealed at 700 °C showed absorptance of αs = 0.914–0.923 and emittance of eT = 0.244–0.357. Besides, thermal stability tests were carried out by a prolonged and extended accelerated thermal investigation at 227 °C. The TSSS paint coatings exhibited no observable visual changes and the performance criterion (PC) values reached the requirement needed.

Aqueous chemical solution deposition of spinel Cu1.5Mn1.5O4 single layer films for solar selective absorber

Herein, non-toxic, ample, and cheap water served as the solvent to dissolve Cu and Mn nitrate, chelating agent, and wetting agent, where a long-term stable sol solution could be easily obtained. The single layer solar absorber film derived from the above precursor has been successfully deposited on a stainless steel substrate via a facile and low-cost sol–gel dip-coating method. A spinel Cu1.5Mn1.5O4 phase for the single layer thin film could be achieved at the annealing temperature of 450 °C for 1 h. The effect of annealing temperature on the surface structure and optical properties of the thin film was systematically studied. The results revealed that the film thickness, integration of impurities, and surface texture (crystallinity, nanoporosity, and roughness) coordinately influenced solar absorptance and thermal emittance of the thin film. A Cu1.5Mn1.5O4 single layer thin film annealed at 500 °C exhibited excellent solar absorptance (αs = 0.914) and thermal emittance (e100 = 0.125). Furthermore, the single layer spinel thin film also showed benign thermal stability at the corresponding working temperature. Consequently, it could be used as a promising candidate for solar absorber thin films and safely applied in low-to-mid temperature regions.

Highly efficient visible-light-driven photocatalytic degradation of rhodamine B by a novel Z-scheme Ag3PO4/MIL-101/NiFe2O4 composite

The effectiveness of metal–organic frameworks (MOFs) as solid-state electron mediators for rhodamine B (RhB) degradation in a Z-scheme photocatalysis system is demonstrated. Novel Z-scheme Ag3PO4/MIL-101/NiFe2O4 (APO/MOF/NFO) composites were synthesized by an in situ precipitation method and employed to degrade RhB dye under visible-light irradiation. The photocatalytic activity results demonstrated that the Z-scheme APO/MOF/NFO(20%) photocatalyst showed relatively improved photocatalytic activity and stability in the degradation of RhB over the individual APO, NFO and APO/NFO materials. By the electrochemical and fluorescence measurements, the APO/MOF/NFO(20%) material also showed a larger transient photocurrent, lower impedance, and longer fluorescence lifetime (7.68 ns). Comparing the activity results with the characterization results, it was indicated that the photocatalytic activity depends on the rapid transfer of electrons from APO to NFO through the three-dimensional structure of the MOF. Furthermore, the possible mechanism for the photodegradation process of APO/MOF/NFO(20%) was proposed to illustrate excellent photocatalytic activity. The present study has paved a new way for using the attractive MOF in the design of a new and efficient system for organic dye degradation in wastewater.

Synthesis and characterization of CoCuMnOx spinel ceramic thin films for spectral selectivity absorption

CoCuMnOx ceramic films were deposited onto stainless steel (SS) substrates by a convenient and innovative aqueous solution chemical method. With this approach, the ubiquitous, inexpensive, and nontoxic water acting as a green solvent was employed to dissolve metal salts, chelating agent, and wetting agent, all of which are low-cost and available commercially. The obtained aqueous solution precursor, showed long-term stability and reproducibility, and could be utilized to prepare CoCuMnOx ceramic films for solar absorber applications. X-ray diffraction (XRD) peaks of the ceramic thin film that was annealed at 450 °C for 1 h corresponded to that of crystalline CoCuMnOx in the JCPDS database. Then, the influence of deposition parameters such as annealing temperature and withdrawal speed on chemical ingredients, film thickness, surface features, and optical properties of the ceramic films was investigated in detail. The result indicated that CoCuMnOx ceramic films exhibited a good spectral selectivity, which was obtained at a 500 °C annealing temperature with different withdrawal speeds. Subjected to an accelerated thermal stability test at 246 °C, the prepared ceramic films showed excellent thermally stability and performance criterion (PC) values below 0.05.