Study On Ni-Mo Based Non-vacuum Mid-high Temperature Solar Selective Absorbing Coatings Prepared By HVOF And APS

Solar selective absorbing coating has a high absorptance in UV-Vis-NIRspectral range and a low emitttance in the middle and far infrared range. For themoment, most processes used are magnetron sputtering, electrolytic deposition,sol-gel and so on. The coatings prepared by these methods have a good selectiveabsorbing performance, but ruled by the processes, the coatings can only be used invacuum or at a low temperature, which restrict their application in photothermalpower generation.We have designed A Visual Basic program to calculate the absorptance of thecoating, which meet the requirement of accuracy in calculating absorptance.After preparing an anti-reflection coating on the Ni-Mo-Co composite coatingsprepared by HVOF and APS,we test the selective absorbing performance, thermalshock resistance and neutral salt spray resistance.In the experiment, three composite powders are prepared by sprayinggranulation with keeping the Ni:Mo ratio at7:3and the composition of Co being5wt%,10wt%and15wt%respectively.Studies show that the absorptance of the coatings is about0.78, and theemittance of the coating by HVOF is0.39compared with0.56by APS. With theincreasing of Co content, both the absorptance and emittance of the coating rise,while the emittance of the coating prepared by APS has a much larger increase.Besides, the non-melted particles in the microstructure of the coating prepared byHVOF reduce with the increasing of Co. Comparing with the coating prepared byAPS, we find HVOF is a better method for the preparation of Ni-Mo-Co coatingswith better microstructure and lower emittance.SnO₂/Al₂O₃anti-reflection coatings are prepared by sol-gel on HVOFcoatings. Results show that the selective absorbing performance has risen a lot. Theabsorptance can reach0.904/0.880respectively, while the emittance has dropped to0.286/0.279respectively. After100times’ thermal shock test at600℃, theperformance of the composite coating keeps stable. The coating with SnO₂anti-reflection fails after48h NSST, while the coating with Al₂O₃anti-reflection keeps stable after96h NSST.All the results show that the coating prepared by HVOF with Al₂O₃anti-reflection has a good solar selective absorbing performance, thermal shockresistance and neutral salt spray resistance, which will have a good applicationprospects.