無電鍍複合鍍製備Ni-Al2O3太陽能選擇性複合吸收膜之性質探討

本研究利用無電鍍複合鍍在鋁基材上製備Ni-Al2O3太陽光譜選擇性吸收膜(spectrally selective absorbers)，並利用溶凝膠法（sol-gel）製備抗反射層，討論電介質（Al2O3）尺寸與含量、吸收層厚度以及雙層吸收膜對於太陽光吸收率(α)、熱輻射率(ε)的影響、並探討抗反射層對於吸收性之改善。使用SEM觀察吸收膜表面形貌及Al2O3粒子之分佈型態，並測量吸收層厚度，紫外光/可見光/近紅外光分光光譜儀（UV-Vis-NIR Spectrometer）量測在300nm~2500nm波長範圍之反射率，複立葉紅外線光譜儀(Fourier transform infrared spectrometer. FTIR)分析2500nm~10000nm波長範圍之反射率，所得之反射率經由公式算出吸收率與熱輻射率。當Al2O3粒子粒徑為70nm時，可以得到較佳之光學性質；當吸收層厚度為0.4μm、Al2O3含量從6 vol.% 增加到25 vol.%，α從0.50增加至0.75，ε從0.06增加至0.15；當Al2O3含量為25 vol.%時，吸收層厚度從0.4 μm增加到4.9 μm，α則從0.75減少至0.27，ε從0.15降為0.03。利用雙層不同Al2O3含量（9 vol.%與25 vol.%）之吸收膜可以得到α為0.77，ε為0.09之吸收膜性質，在此雙層吸收膜上塗上一層TiO2抗反射層，α從0.77提升到0.90，而ε則維持在0.09；Ni-Al2O3複合吸收膜經過72hr之熱穩定性與抗水性測試後，其光學性質並無太大之變化，顯示以無電鍍複合鍍製備ㄒNi-Al2O3太陽光譜選擇性吸收膜具有良好的光學性質與熱穩定性、抗水性。

關鍵字

無電鍍複合鍍；太陽能選擇性吸收膜；吸收率；熱輻射率

並列摘要

In this work, the metal-dielectric composite (Ni-Al2O3) solar spectally selective absorbers have been deposited on aluminum substrate using the electroless composite coating technology and the antireflection layers for the absorbers were fabricated by sol-gel method. The effects of the size and content of dielectric (Al2O3), the thickness of absorber, the double absorption layer and the antireflection layer on the absorbance (α) and thermal emittance (ε) of Ni-Al2O3 composite solar selective absorber were studied. The surface morphology of absorber and dispersion of Al2O3 in absorber were observed by scanning electron microscopy (SEM). The measurement of reflectance in the wavelength range 300-2500 nm was carried out by UV-VIS-NIR Spectrometer and that in the wavelength range 2500-10000nm were performed by Fourier transform infrared spectrometer (FTIR) . The Al2O3 with 70nm in absorber has better optical properties than that with 300nm.The α is increasing from 0.5 to 0.75 and the ε is increasing from 0.06 to 0.15 , as the Al2O3 content in absorber is increasing from 6 vol.% to 25 vol.% . The α is decreasing from 0.75 to 0.27 and the ε is decreasing from 0.15 to 0.03, as the thickness of absorber is increasing from 0.4 to 4.9 μm. The α and ε of the double absorption layer sample with 9 vol.% and 25 vol.% Al2O3 absorbers was 0.77 and 0.09 , respectively . The TiO2 antireflection layer is useful to promote the α from 0.77 to 0.90. The Ni-Al2O3 composite solar spectally selective absorbers with TiO2 antireflection layer after thermal stability test and humidity test for 72hr were preserved almost the same optical properties as the as-deposited samples.