Microstructure building and thermal stability of cermet-basedphotothermal conversion coatings with layered structures br

To enhance the thermal stability of cermet-based photothermal conversion coatings, the present paperproposes a novel strategy to replace the randomly distributed nanoparticles with layered structure. This kind ofstructure can not only suppress the agglomeration and rapid growth of nanoparticles, but also enhance theinteraction between the absorber and sunlight. Thus, the thermal stability and selectivity can be simultaneouslyimproved by this unique kind of structure. Then, a Cr/AlCrN/AlCrON/AlCrO multilayer cermet-basedphotothermal conversion coating is designed and fabricated by multi-arc ion plating. The microstructure, opticalproperties and thermal stability of the multilayer coating are studied in detail. The optical properties tests showthat the absorptance and emittance of the as-deposited coating achieve 0.903 and 0.183, respectively. Moreimportantly, after being annealed at 500 degrees C in air for 1000 h, the absorptance reaches 0.913 and the emittancearrives at 0.199, implying the enhanced selectivity and thermal stability, which are ascribed to the formation ofnanolaminates, in which a series of alternating sublayers is observed in the AlCrON absorber. The nanolaminateis a two-phase composite structure composed of layered AlN and Cr2N nanoparticles distributed in amorphousdielectric matrix. According to the finite difference time domain (FDTD) simulations, this unique kind ofmicrostructure can trap photons in the coating, which is beneficial to enhancing the interaction intensity andtime between the sunlight and absorbing sublayer, and thus improving the absorption of sunlight. In addition,the reduction of particle spacing during annealing will lead to the red shift of extinction spectrum, which willbetter match the solar radiation spectrum. At the same time, this kind of structure can avoid the agglomerationof nanoparticles, which can simultaneously tune the optical properties and thermal stability