Stress‐Induced Failure Study on a High‐Temperature Air‐Stable Solar‐Selective Absorber Based on W–SiO₂ Ceramic Composite

Abstract

A stress‐induced failure study on a high‐temperature air‐stable ceramic composite solar selective absorber (SSA) based on a W–SiO2 system is reported. The as‐prepared SSA exhibits excellent spectral and structural stability after annealing in air at 500 °C for 36 h, proving its thermal stability against air corrosion. However, once the temperature is elevated to 600 °C, optical performance degradation and coating cracking happens. The X‐ray diffraction (XRD) patterns reveal that an O‐induced phase transition process from α‐W to β‐W occurs at the interface between the W IR reflector and W–SiO2 layer during deposition. The phase transition induces immense internal stress, which becomes the incentive of crack generation. Further increasing the annealing temperature, drastic structural changes of oxidized W become the driving force for crack propagation and hole expansion, leading to a failure analogous to a volcanic eruption. To improve the temperature limit of coating, a Ni–SiO2 stress buffer layer is introduced and successfully reduces the internal stress through Ni atom substitution for W atoms. Therefore, the optimized SSA keeps stable at 600 °C and the cracking temperature increases to 650 °C. These results suggest that the W–SiO2‐based SSA is a good candidate for air‐stable high‐temperature solar thermal conversion.

Air-Stability Improvement of Solar Selective Absorbers Based on TiW–SiO2 Cermet up to 800 °C

“…Therefore, after annealing at 600 °C, the internal stress would become the incentive of cracking. This stress-induced failure process has been elaborately discussed in our previous work …”

“…The particle sizes of β-W (2 0 0) (defined as D ) are shown in Table . The calculation of D abides by the Scherrer equation . On account of that the (2 0 0) plane is the preferred orientation, the D values are nearly equal to the thicknesses of the β-W phase.…”

“…The calculation of D abides by the Scherrer equation. 33 On account of that the (2 0 0) plane is the preferred orientation, the D values are nearly equal to the thicknesses of the β-W phase. The β-W (2 0 0) in the pristine sample, 650 °C-case, and 700 °C-case are all determined to be 34.2 nm, proving its great thermal stability.…”

“…The commonly reported failures of SSAs in the air atmosphere were caused by partial oxidation and inner diffusion. , For example, Ke et al claimed that the element diffusion between the substrate and absorber would result in local stress at the interface, and the local stress contributed to the increase of surface roughness, microcracks, holes, and other microdefects. In our previous work, a W-SiO 2 -based SSA was prepared by the co-sputtering method, and the coating is proved to be stable in the air at 500 °C for 36 h . However, it cracked at over 600 °C due to internal stress, and the subsequent oxidation at the cracking points led to the destruction of the coating.…”

Uninterrupted Self‐Generation Thermoelectric Power Device Based on the Radiative Cooling Emitter and Solar Selective Absorber

“…The RCE, the TEG, and the SSA were all bonded together by thermally conductive silicone grease. A 150 μm coating rod was used to coat PDMS (DC184, Dow Corning) on an electron‐polished Al substrate, and then cured at 90 °C for 1 h. The SSA was deposited on the polished Al substrate (thickness 1 mm) by the magnetron sputtering method following the previous work, [ 36 ] and the detailed sputtering parameters are given in Table 1 . The TEGs were purchased from TEC‐12 703 (Sagreon, China), and the corresponding measurement results of TEGs can be found in Figure S1 in the Supporting Information.…”