Preparation And Thermal Stability On Non-vacuum Medium-high Temperature Mo-Cu/Al₂O₃Solar Absorber Coatings

Solar energy selective absorbing coatings can effectively improve the conver-sion efficiency of solar thermal. As a core technology in solar thermal powergeneration, medium-high temperature solar absorbing coatings is the research focusin solar thermal utilization field, which has a broad application prospects. Targetingat those problems including poor thermal stability, high-costs etc. of currentmedium-high temperature solar absorbing coatings in practical applications underhigh temperature, this paper is going to talk about a new coating preparation process,and a new composite coatings that suitable for medium-high temperature andnon-vacuum conditions.To produce the Mo-Cu composite powder, which is the main absorber materialof coatings, the surface of the nano-molybdenum powder is coated with a layer ofcopper by electroless copper plating technology. Atomized granulation technology isadopted to produce loose nano-micro structure that suitable for plasma spraying ofmicron composite powder with Nano-Al₂O₃and Mo-Cu composite powder. Solarabsorbing coatings whose thickness is about2.5μm is sprayed on the pretreatedcopper base by plasma spraying technology. This coating production technics adoptsconventional plasma spraying technology instead of current commonly usedmagnetron sputtering technique, which greatly reduces the cost. As the lead to twoelements of the coatings containing mainly copper oxygen diffusion and oxidation ofcopper at high temperatures basement,The coatings absorption and emission rate, measured by UV-visible-nearinfrared spectrometer under different heat treatment temperatures shows nosignificant changes when heat treatment temperature is below600℃. The rate isabout0.86and0.347, which shows that the coating has a good high-temperatureoptical property. By observing the morphology and composition of the coatingsurface under different annealing temperature（100℃、200℃、300℃、400℃、600℃、800℃、900℃） for2h with SEM and EDS, nanoparticles reunion is found around theundissolved areas and semi-molten zone of the coatings. When the heat treatmenttemperature is above800℃, As the lead to two elements of the coating containingmainly copper oxygen diffusion and oxidation of copper at high temperaturesbasement, When the heat treatment temperature is above900℃, no open and splitoff phenomenon is found. All these prove that the coatings has good thermal stability below900℃. It can be used as an ideal selective absorbing coatings material insolar thermal power generation and building energy-conservation.At the end of this paper, the impact of the experimental process on coatingsperformance is discussed. It was found that when the volume ratio of metalcomponents in the composite powder controlled below30ï¼…, binder contentcontrolled below3.2wtï¼…, solid content controlled between40-60ï¼…, theperformance of composite solar selective absorbing coatings reaches the best.