The study of Al2O3-Black Ni solar spectrallyselective composite absorbers manufactured byelectroless composite coating technology

• Main Authors: an-zhou Jlang, 江安洲
• Other Authors: 蔡定侃
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/4e4b4m

碩士 === 國立虎尾科技大學 === 材料科學與綠色能源工程研究所 === 97 === The metal-dielectric composite spectrally selective solar absorbers were widely used in solar thermal collectors due to its excellent absorption. The manufacture cost of the metal-dielectric composite spectrally selective solar absorbers is expensive and that limits its applications. In this work, the electroless composite coating technology which possesses lower cost, simple equipment and easy to operate characteristics was used to fabricate the Al2O3-black nickel composite solar selective surface on Al substrate and the Sol-gel technique was used to fabricated the anti-reflection (AR) layer. The effects of the particle size(300 nm ,70 nm , 15 nm) and content(4 g/L , 8 g/L , 16 g/L , 24 g/L , 28 g/L) of Al2O3, the thickness of the Al2O3-Black nickel composite coatings and the AR layers of SiO2 and TiO2 on the optical properties of the absorbers were investigated. The Uv/Vis/NIR spectrophotometer was utilized to measure the reflectance of the absorbers in the wavelength interval of 300 – 2500 nm, and the FTIR spectrometer was utilized to measure that in the wavelength interval of 2500 – 20000 nm. SEM and AFM were used to observe the surface morphologies and the thickness of coatings. The chemical structures of coatings were studied by ESCA. The environment durabilities including thermal stability and humidity resistance of the samples with optimized optical properties were performed.. The content of 300 nm alumina increases from 8 g/L to 28 g/L , the solar absorptance α of Al2O3-Black nickel/Al absorber increase from 0.69 to 0.79, the thermal emittance ε increase from 0.08 to 0.11. The content of 70 nm alumina increases from 8 g/L to 28 g/L , the solar absorptance α increase from 0.79 to 0.84, the thermal emittance ε increase from 0.13 to 0.20. The content of 15 nm alumina increases from 4 g/L to 16 g/L , the solar absorptance α increase from 0.81 to 0.86, the thermal emittance ε increase from 0.09 to 0.15. The 2.7 μm Al2O3-Black Nickel composite coatings contained 16 g/L of 15 nm alumina have optimum optic properties, solar absorptance α = 0.89 and low emittance ε = 0.07, and high selectivity factor 12.71. The solar absorptance and thermal emittance of the Al2O3-Black Nickel/Al absorbers with SiO2-0.5M AR layers are 0.92 and 0.09, respectively. Those of the Al2O3-Black Nickel/Al absorbers with TiO2 AR layers are 0.83 and 0.19, respectively. The selectivity factor of Al2O3-Black Nickel/Al absorbers after 300 ℃thermal stability test for 75 h decreased from 12.71 to 9.4, and that of black Nickel/Al absorbers decreased from 17 to 4.84. After 95 % humidity condensation test for 75 h, the selectivity factor of Al2O3 - Black Nickel/Al absorbers decreased from 12.71 to 4.81, and that of Black Nickel/Al absorbers decreased from 17 to 5.61.