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The polymer-dielectric composite film is reported to obtain a hierarchical micro–nano structure. Composites exhibit excellent optical properties and their actual radiative cooling effect was tested in an outdoor environment.

A tailored synthesis method is used to yield AlTiZrHfNbN based coatings with excellent spectral selectivity, showing an ultrabroad absorption wavelength range at or beyond the level of solar selective absorber coatings.

Developing advanced materials with a high-entropy concept is one of the hot trends in materials science. The configurational entropy of high-entropy materials can be tuned by introducing different atomic species, which can also impart a result in excellent physical and chemical properties. In this work, we synthesized a solid-solution oxide (Cu, Mn, Fe, Cr)

Solar and radiative warming are smart approaches to maintaining the human body at a metabolically comfortable temperature in both indoor and outdoor scenarios. Nevertheless, existing warming textiles are ineffective in frigid climates because the solar absorption of selective absorbing coating is significantly reduced when coated on rough textile surface. Herein, for the first time, high-entropy nitrides based spectrally selective film (SSF) is introduced on common cotton through a one-step magnetron sputtering method. The well-designed refractive index gradient enables destructive interference effects, offering a roughness-insensitive high solar absorptance (92.8%) and low thermal emittance (39.2%). Impressively, the solar absorptance is 9.1% higher than the reported best-performing selective nanofilm-based textile. As a result, such a textile achieves a record-high photothermal conversion efficiency (82.2% under 0.6 suns, at 0 °C). This textile yields a 3.5 °C drop in the set-point of indoor air-conditioner temperature. Besides, in a winter morning with an air temperature of 7.5 °C, it warms up the human skin by as large as 12 °C under weak sunlight (350 W m

With the development of new materials and technology, high entropy alloy (HEA) nitride films have attracted much attention of researchers due to their excellent optical properties and mechanical properties. Herein, a novel SS/NbMoTaWN (HEAN)/NbMoTaWON (HEAON)/SiO2 coatings are prepared, which shows a high spectral selectivity of α/e = 0.944/0.12. The preparation and optimization of the coating are studied by combining experiments with ellipsometric program and CODE software. High temperature thermal stability test is performed in depth, which proves that the coating could bear 400 °C in air for 2 h, and 600 °C for 2 h in vacuum. Long-term thermal stability researches indicate that the SSACs still keep good optical properties (α = 0.902, e = 0.106) even after annealing at 600 °C for 100 h. The failure mechanism is analyzed by XRD and Raman spectra. In addition, neutral salt spray test is performed to investigate the anti-corrosion ability, which indicates the coating has a good optical performance after soaking in 3.5 wt% NaCl solution for 30 days. Obviously, this work provides a new strategy to construct solar absorber coatings based on NbMoTaW high entropy alloy.

High entropy alloys (HEAs), which is at the expense of high cost compared to traditional alloy, should not be confined to the mechanical properties, but should be employed to devise a novel combination with unique functional and mechanical performances. In this work, high entropy alloy nitride (HEAN) is utilized as a novel double absorption layer to improve solar absorption in the high temperature solar selective absorbing coatings (SSACs). Our primary motivation is to lower thermal emittance (e) and enhance solar absorptance (α). In order to realize this goal, coating design (CODE) software is employed to design and optimize the proposed HEAN based SSACs using appropriate dielectric function model. The ultimate as-deposited coating shows good optical properties with a high α value of 0.965 and a low e value of 0.086 (at 82 °C). The estimate of thermal stability tests indicates that HEAN based SSACs has the ability to resist instability in high working temperature, which keeps good optical properties (α = 0.925, e = 0.070) after annealing at 600 °C for 10 h.

Solar selective absorber coatings (SSACs), with the characteristics of efficient harvesting and conversion of solar energy into the heat work fluid, are considered to be one of the key components f...

Recent advances in high-entropy alloys have spurred many breakthroughs in the fields of high-temperature materials and optical materials and they provide incredible application potentialities for photothermal conversion systems. Solar-selective absorbers (SSAs), as key components, play a vital role in photothermal conversion efficiency and service life. The most pressing problem with SSAs is their inconsistent optical performance, an instability constraint induced by thermal stress. A feasible method of improving performance stability is the introduction of high-entropy materials, such as high-entropy alloy nitrides. In this study, enabled by an intrinsic MoTaTiCrN absorption layer, the solar configuration achieves greatly enhanced, exceptional thermotolerance and optical properties, leading to the formation of a scalable, highly efficient, and cost-effective structure. Computational and experimental approaches are employed to achieve optimum preparation parameters for thicknesses and constituents. The crystal structure of high-entropy ceramic MoTaTiCrN is fully investigated, including thickness-dependent crystal nucleation. High-temperature and long-term thermal stability tests demonstrate that our proposed SSA is mechanically robust and chemically stable. Moreover, a low thermal emittance (15.86%) at 500 °C promotes the photothermal conversion efficiency. In addition, due to the exceptional spectral selectivity (α/ε = 92.3/6.5%), thermal robustness (550 °C for 168 h), and photothermal conversion efficiency (86.9% at 550 °C under 100 sun), it is possible for our proposed SSA to enhance the practical realization of large-area photothermal conversion applications, especially for concentrated solar power systems.

The most recent advances in high-entropy materials provide impetus for the development of high-performance materials, simultaneously providing high-temperature robustness and excellent functional properties owing to the high configurational entropy and distorted lattices. Thus, in this work, double-layer high-entropy alloy nitride HfNbTaTiZrN with a well-designed metal content gradient is employed to fabricate a solar selective absorber coating (SSAC). We extensively investigated whether the coating meets the definition of a high-entropy material from the points of elemental analysis and phase structure, combined with thermodynamic calculation. Remarkably, the new, tailored SSAC exhibits an exceptionally high solar absorptance (α = 96%) and a suppressed thermal emittance (e = 8.2%) at 82 °C and omnidirectional absorption. Investigations of the long-term thermal stability indicate that the HfNbTaTiZrN-based SSAC due to the entropy-driven structural stabilization could endure heat treatment at 600 °C for 168 h, retaining a performance criterion (PC) value less than 0.05, which implies the feasibility of practical applications. More importantly, the photothermal conversion efficiency (η), which is utilized to quantitatively evaluate the performance at elevated temperatures, reaches 90.1% at a working temperature of 550 °C under 100 suns, and even after annealing at 600 °C for 168 h, the efficiency drop is still less than 5%. Overall, the combination of thermal robustness and photothermal conversion efficiency at working temperatures less than 600 °C provides significant potential to maximize solar energy harvesting and pioneers an opportunity to explore simultaneous multifunctional applications of high-entropy alloys.

The functional application of high entropy alloys, which emerge as a novel multi-principal component alloy, has been constantly expanding in the field of solar photothermal harvesting from optical materials to high temperature materials due to their excellent properties. A solar spectrally selective absorbing coating requires such materials that show not only outstanding optical properties but also prominent thermal stability. It is desirable but challenging to fabricate high performance solar absorbing coatings. A prospective strategy for the preparation of solar absorbing coatings is the introduction of high entropy alloys. In this work, we have developed a simple, cost-conscious, scalable and highly efficient solar selective absorbing coating using a single layer high entropy nitride AlCrTaTiZrN by choosing appropriate elemental compositions. The as-deposited coatings show an outstanding spectral selectivity of α/e = 92.8%/5.1% or 91.6%/5.1%. High temperature thermal stability tests are performed in depth, indicating that the coating could endure annealing treatment at 800 °C for 2 h with insignificant reflectance spectrum variation. A prolonged period of thermal stability characterization presents that this coating could maintain good optical performance after annealing at 650 °C for 300 h. Furthermore, high temperature thermal emittance can be suppressed to as low as 15.4% at 600 °C, which contributes to the state-of-the-art photothermal conversion efficiency under 100 suns (87.7% at 600 °C, and 84.6% at 650 °C). Overall, the high entropy nitride AlCrTaTiZrN based coating contributes to good thermal stability and optical properties, showing great potential for extensive applications in solar energy harvesting.

In the present work, a solar selective coating of ZrB2/Al2O3 was deposited onto stainless steel (SS) substrates using a magnetron sputtering system. The coating exhibited an good selective absorbing properties with an absorptance of 0.92 and an emittance of 0.11. To investigate the thermal stability of the coating, the samples were annealed at 500 °C and 600 °C for 100 h, respectively. Experimental results indicated that the coating was thermally stable at 500 °C. The structure and optical properties of the coating is also characterized using ultra-high resolution scanning electron microscope, UV–vis–NIR spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS). The reflectance spectra of the SS/ZrB2/Al2O3 coating was successfully simulated by CODE software.

Transition metal titanium diboride (TiB2) is a promising material for the solar selective absorbing coatings due to its favorable spectral selectivity and thermal stability. In this research, spectrally selective TiB2/Al2O3 tandem absorber is deposited on stainless steel (SS), which exhibits a high solar absorptance (αs = 0.93) and a low thermal emissivity (e = 0.11). In this tandem absorber, the TiB2 acts as the main absorber layer and the Al2O3 acts as an antireflection layer. The tandem absorber coating is systematically characterized by ultra-high resolution scanning electron microscope (SEM), UV–vis-NIR spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Micro-Raman techniques. The thermal stability in vacuum of the SS/TiB2/Al2O3 tandem absorber coatings is investigated in the temperature range of 400–800 °C for 2 h and 100 h, respectively. SEM and Raman spectra indicate that the change of surface morphology and chemical composition for the coating result in the degradation of optical performance. With the different annealed temperature, the SS/TiB2/Al2O3 tandem absorber coatings exhibit different color, which is further investigated using chromaticity diagram.

Transition metal borides are a kind of potential materials for high-temperature solar thermal applications. In this work, a novel SS/HfB2/Al2O3 tandem absorber was prepared, which exhibited high solar spectrum selectivity (α/e) of 0.920/0.109. The optical constants of the coating were obtained using spectroscopic ellipsometry, and the dispersion model of the HfB2 layer was modeled with the Tauc–Lorentz dispersion formula. In addition, the reflectance spectrum simulated by the CODE software corroborated well with the experimental results. The thermal stability test indicated that the HfB2/Al2O3 solar absorber coating was thermally stable in vacuum at 600 °C for 2 h. When extending the annealing time to 100 h, the coating could maintain high spectral selectivity after aging at 500 °C irrespective of whether in air or vacuum. All these results indicate that the coating has good solar selectivity and is a promising candidate for high-temperature solar thermal applications.

Due to the superior characteristics of strong localized surface plasmon resonance, low-cost consumption, and substantial chemical and thermal stability, conductive metal-ceramic nitrides, such as TiN, ZrN and HfN, are considered promising photothermal materials for solar-driven water evaporation and desalination. Transition metal carbides have also been proposed as promising solar absorbers, making them suitable candidates for solar-driven interfacial evaporation and desalination. However, little attention has been paid to this aspect thus far. Here, to gain new insights into the evaporation and desalination performance, we chose ZrC nanoparticles (NPs) as the experimental subject to fabricate an interfacial evaporation device. The highest evaporation rate and evaporation efficiency values were 1.43 ± 0.04 kg m−2 and 98 ± 2%, respectively, for the ZrC NP-integrated device at a loading mass of 85 g/m2. Desalination was further tested using simulated water (3.5% salinity) and collected saline water (21% salinity) as sources, and the evaporation rate and efficiency reached 1.38 ± 0.1 kg m−2 h−1 and 96 ± 0.75%, respectively, under 1 sun illumination. Measurement of ion concentrations following the desalination process demonstrates the effective removal of major saline ions (Na+, Mg2+, K+ and Ca2+).

A novel Mo/Al2O3 spectrally selective solar absorber coating is deposited onto stainless steel (SS) substrates using magnetron sputtering method, which exhibits a high absorptance (α) of 0.90 and a...

A tandem layer structured ZrC-ZrOx/Al2O3 coatings are deposited onto stainless steel (SS) substrates by the sputtering method for solar selective absorbing. The ZrC-ZrOx and Al2O3 layers work as an absorptance layer and an antireflectance layer, respectively. The substrate temperature has an important effect on the optical properties of the coating. With a high substrate temperature (300 °C), the SS/ZrC-ZrOx/Al2O3 coatings exhibit a relatively high absorptance of 0.92 and a relatively low emittance of 0.12. The composition, structure, optical properties and surface morphology of the coatings are characterized using SEM, EDS, XPS, Raman, UV–vis–NIR spectrophotometry and Fourier transform infrared spectroscopy. Detailed failure analysis of the SS/ZrC-ZrOx/Al2O3 coatings in vacuum and air is conducted.

With the rapid advance of science and technology, it is essential to research and develop new intrinsic solar absorber coatings with the simple production process and excellent photo-thermal conversion efficiency. Herein, we have developed a novel AlCrMoTaTiN intrinsic absorber layer by radio frequency (RF) reactive sputtering method via adjusting the deposition time and the flow rate of N2. The AlCrMoTaTiN intrinsic absorber layer exhibits a high absorptance of 0.752 and a low emittance of 0.074 at 82 °C. The AlCrMoTaTiN/Al2O3 solar absorber coating is deposited by using Al2O3 works as an anti-reflective layer and the spectral selectivity (α/e) is 0.929/0.082. This coating also possesses a good thermal stability, which can be stabilized at 300 °C in air and 500 °C in vacuum for 2 h, respectively. In addition, a prolonged period of thermal stability characterization is carried out, which indicates that this coating could keep good optical performance after annealing at 600 °C for 100 h. The corresponding failure mechanism is obtained by analyzing the Raman spectroscopy and XRD. Obviously, the AlCrMoTaTiN/Al2O3 solar absorber coating has a broad application prospect in large-scale and efficient industrial production.

This work is a continuation of earlier work where TiC/Al 2 O 3 spectrally selective solar absorbers were deposited onto stainless steel (SS). In this study, the optical simulation, corrosion behavior and long term thermal stability are investigated in detail. A series of TiC and Al 2 O 3 single layers are fabricated by magnetron sputtering using the same deposition parameters as described in the previous work. The optical constants and thicknesses of glass, stainless steel, TiC and Al 2 O 3 layers are obtained by CODE software using the suitable dielectric function model. Then, the structure model of SS/TiC/Al 2 O 3 is constructed and the reflectance spectra of the SS/TiC/Al 2 O 3 solar absorber is successfully simulated using CODE software. The anti-corrosion performance of SS/TiC/Al 2 O 3 solar absorbers is evaluated through electrochemical potentiodynamic polarization measurement and salt spray test. The SS/TiC/Al 2 O 3 solar absorbers have a good thermal stability in vacuum at 500 °C for 100 h. Raman analysis indicates that the increased sp 2 bonds of the coating is the main reason for the degradation of the optical properties.

A new spectrally selective solar absorber coating of TiC-WC/Al2O3 tandem layer is designed and prepared on stainless steel (SS) substrate by magnetron sputtering. The coating consists of an absorptance layer (TiC-WC) and an antireflectance layer (Al2O3) from substrate to top. The new SS/TiC-WC/Al2O3 coating exhibits excellent selective absorbing properties with a high solar absorptance of 0.92 and a low thermal emittance of 0.11. The SS/TiC-WC/Al2O3 coating presents a purple color, which is further investigated by chromaticity study. The thermal stability of the coating is evaluated and characterized by SEM, XRD, UV–vis–NIR spectrophotometer, Fourier transform infrared spectroscopy, and Raman spectroscopy. Experimental results indicate that the coating is highly stable in vacuum at 500 °C for 100 h with a good solar selectivity of 0.92/0.11.

Exploring a high performance spectrally selective solar absorber is one of the great challenges in the development of Concentrating Solar Power (CSP). Herein, a porous structure of SS/TiC-Y/Al2O3 solar absorber is developed by a facile and scalable method combined with a simple vacuum annealing process. The tandem SS/TiC-Y/Al2O3 solar absorber exhibits a high absorptance of 0.90 and a low emittance of 0.11 after vacuum annealed at 800 °C for 5 h. Long term thermal annealing result indicates that the SS/TiC-Y/Al2O3 solar absorber coating has a good thermal stability at 800 °C in vacuum for 100 h. Due to the addition of rare earth yttrium (Y) and post-annealing, the porous structure is formed, which makes contribution to the spectral selectivity. Benefiting from these advantageous features, the post-annealed SS/TiC-Y/Al2O3 coating can be good candidate for the Concentrating Solar Power application.

By replacing absolute ethanol, water was used as a ubiquitous and low-cost solvent to dissolve metal nitrates and organic additives to obtain a precursor solution that showed long-term stability and reproducibility. This precursor solution was used to deposit a CuMn 2 O 4 ceramic film on a stainless steel substrate using the convenient and inexpensive sol-gel dip-coating technique. The X-ray diffraction (XRD) profile of the ceramic film annealed for 1 h at 450 °C was found to coincide with that of crystalline CuMn 2 O 4 in the JCPDS database. The CuMn 2 O 4 ceramic film obtained at an annealing temperature of 500 °C exhibited excellent solar absorptance ( α s =0.905) and thermal emittance ( e 100 =0.120). By optimizing the deposition parameters, we systematically investigated the effect of the chemical components, surface texture, and thickness of the ceramic film on its optical properties. Subjected to a thermal stability test at 252 °C, the CuMn 2 O 4 ceramic film showed good thermal stability with performance criterion (PC) values below 0.05.

A new spectrally selective solar absorber coating of TiC/Al 2 O 3 is prepared on stainless steel substrate using a magnetron sputtering method. The new coating exhibits a high absorptance of 0.92 and a low emittance of 0.13 (82 °C). The tandem absorber is characterized using ultra-high resolution scanning electron microscope, UV–vis–NIR spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The formation of amorphous carbon is due to the dissociation of TiC layer deposited under high substrate temperature (300 °C). The diffused carbon at 600–800 °C with mixed sp 2 and sp 3 bonds is further demonstrated by XPS and Raman spectra. With an increase in annealing temperature, the surface structure becomes more graphitic. The tandem absorber is stable in vacuum up to 650 °C for 2 h, indicating its importance for high temperature solar selective applications.

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.

Transition metal borides are a kind of potential materials for high-temperature solar thermal applications. In this work, a novel SS/HfB

Simple technological process, low cost and high stability are important for large-scale production of the high temperature spectral selective solar absorber coatings. In this study, a simple Mo-HfC/Al2O3 coating that only contains an absorber layer (Mo-HfC) and an antireflection layer (Al2O3) deposited onto stainless steel substrate, which exhibits a high spectral selectivity (αs/eT) of 0.92/0.11. The experimental results indicate that the addition of Mo could greatly enhance the spectral selectivity of the coating. Thermal stability test demonstrates that the spectral selectivity of the coating remains unchanged even after annealed it at 600°C for 100 h in vacuum. Obviously, the coating shows a promising prospect in high temperature application. In addition, the optical degradation mechanism is also discussed in this work.

A novel TiC-TiN/Al2O3 tandem solar selective absorbing coating was successfully deposited on Si (1 0 0) and stainless steel (SS) substrates by reactive RF magnetron sputtering deposition. The spectral characteristics, microstructure, thermal stability and solar-thermal conversion efficiency of the coating before and after a long annealing in vacuum were investigated systematically. The optical constants of the coating are measured by an Ultraviolet–visible-near-infrared (UV/Vis/NIR) spectrometer, and the chemical composition analysis, structure information and surface morphology are investigated using XRD, XPS and FESEM. An excellent absorptance (α = 0.92) and a low emittance (e = 0.11) at 82 °C are obtained by the as-prepared coatings. After annealed at 500 °C for 100 h in vacuum, there is no significant change in micromorphology and optical properties of the coating, which produces a good solar-thermal conversion efficiency. These results indicate that it can be applied as a potential coating material to a high temperature concentrated solar power (CSP) system.

The present work is a continuation of our earlier work in which high entropy alloy MoNbHfZrTi is used as a raw material to prepare solar absorber coating. In this work, we have further investigated a novel Al/MoNbHfZrTiN/MoNbHfZrTiON/SiO2 multilayer color solar selective absorbing coating, including structure, optical properties, thermal stability and corrosion performance. The results of TEM and XRD indicate that the Al film has nanocrystalline nature and MoNbHfZrTiN, MoNbHfZrTiON and SiO2 are amorphous structure. The results of the mapping confirm the thickness of each layer and distribution of elements. The simulation of optical constants (n and k values) are carried out by CODE software, the results of which indicate that the n and k values decrease from substrate to surface. Neutral salt spray test is preformed to measure the ability of anti-corrosion, which indicates the coating has a good optical performance in 3.5% NaCl solution for 24 h.

Spinel Cu 1.5 Mn 1.5 O 4 thin films were fabricated by one step sol-gel dip-coating method using aqueous solution. The effect of deposition parameters on thickness, surface feature, and optical property of thin films was systematically studied. The results revealed that the increased withdrawal speeds and high concentration of metal ions in precursor were conducive to obtaining thicker films which exhibited excellent solar absorptance. Furthermore, the surface feature derived from the different concentrations of metal ions had a significant effect on optical behavior of the thin film. Consequently, excellent spectral selectivity of the thin film would be achieved by tuning those deposition parameters.

Traditional metal-dielectric composite coating has found important application in spectrally selective solar absorbers. However, fine metal particles can easily diffuse, congregate, or be oxidized at high temperature, which causes deterioration in the optical properties. In this work, we report a new spectrally selective solar absorber coating, composed of low Al2O3 ceramic volume fraction (Al2O3(L)-WC) layer, high Al2O3 ceramic volume fraction (Al2O3(H)-WC layer) and Al2O3 antireflection layer. The features of our work are: 1) compared with the metal-dielectric composites concept, Al2O3-WC nanocomposite ceramic successfully achieves the all-ceramic concept, which exhibits a high solar absorptance of 0.94 and a low thermal emittance of 0.08, 2) Al2O3 and WC act as filler material and host material, respectively, which are different from traditional concept, 3) Al2O3-WC nanocomposite ceramic solar absorber coating exhibits good thermal stability at 600 °C. In addition, the solar absorber coating is successfully modelled by a commercial optical simulation programme, the result of which agrees with the experimental results.

A series of spinel-type CuMn2O4 ceramic pigments were prepared by a facile and low-cost sol-gel solution combustion method and used as cost-effective materials to fabricate thickness sensitive spectrally selective (TSSS) paint coatings by a convenient spray-coating technique. The chemical component, crystalline morphology, and optical property of the copper manganese oxide ceramic pigment could be accurately controlled by altering the annealing temperature. X-ray diffraction (XRD) analysis confirmed that the ceramic pigments annealed at 500 °C for 1 h coincided well with the XRD patterns of crystalline CuMn2O4 in the JCPDS database, and there were segregated phases of CuO and Mn2O3. Furthermore, the pure spinel CuMn2O4 phase could be achieved at 900 °C for 1 h. The copper manganese oxide ceramic pigments could serve as an effective pigment for fabricating the TSSS paint coating, and the TSSS paint coatings based on ceramic pigments calcined at 900 °C showed solar absorptance of 0.895–0.905 and thermal emittance of 0.186–0.310. In addition, the accelerated thermal stability test revealed that the TSSS paint coating exhibited good thermal stability when it was exposed to air at a temperature of 300 °C for 300 h. Hence, the fabricated TSSS paint coating could be used as a solar absorber coating in the low-to-mid temperature domain.

Cu1.5Mn1.5O4-based ceramic spectrally selective (CSS) coating was deposited on aluminum substrate using a sol–gel dip-coating method. The citric acid introduced in the precursor system lowered the required calcining temperature of crystalline Cu1.5Mn1.5O4. X-Ray diffraction (XRD) peaks of coatings annealed above 450 °C were found to coincide exactly with that of crystalline Cu1.5Mn1.5O4 in JCPDS database. By optimizing the withdrawal rate and calcining temperature, coating with spectral selectivity as good as αs = 0.876 and e100 = 0.057 was achieved after only one dipping/annealing cycle. Subjected to an accelerated ageing test at 259 °C, the obtained CSS coating showed an excellent thermally durability with the performance criterion (PC) values below 0.05.

A series of CuCr2O4 spinel ceramic pigments have been successfully synthesized via a facile and cost-effective sol-gel self-combustion method. The reaction mechanism was systematically studied using the corresponding characterization technologies. The results suggested that CuCr2O4 spinel ceramic pigments could be obtained at annealing temperature of 600 °C for 1 h, and the size, morphology, and crystallinity of CuCr2O4 spinel were greatly influenced by the annealing temperature. The as-burnt powder and CuCr2O4 spinel ceramic pigment were then employed to fabricate thickness sensitive spectrally selective (TSSS) paint coatings by a convenient spray-coating technique. The results revealed that spectral selectivity of TSSS paint coatings based on CuCr2O4 spinel ceramic pigments was much better than that of paint coatings based on the as-burnt powders. Furthermore, the effect of surface features of TSSS paint coatings on its optical property and hydrophobicity was investigated in detailed.

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.