中高温太阳能选择性吸收涂层的制备与研究
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摘要
太阳能选择性吸收涂层是太阳能集热器上最为关键的部分,直接制约着太阳能集热器的效率。受材料、结构、加工方法的影响,大多数涂层都只能应用于中低温环境,部分还只能应用于真空环境。目前,多采用磁控溅射工艺制备耐高温的金属陶瓷、多层渐变膜,这类涂层虽然能够应用于非真空高温环境,但是加工成本较高。等离子喷涂工艺及溶胶-凝胶法是常用的涂层制备方法,加工工艺简单,成本低廉,可以实现规模化生产。但是将这两种方法直接应用于制备太阳能选择性吸收涂层却鲜有报道,本文将分别采用这两种方法制备太阳能选择性吸收涂层。
本次实验以Cr2O3、Al2O3和SiO2为主要原料,采用喷雾干燥法制成球形团聚粉末,获得流动性好的喷涂用粉。采用等离子喷涂工艺,在不锈钢基体上制备了黑铬太阳能选择性吸收涂层。涂层具备较高的发射率,通过减小表面粗糙度及制备SnO2选择性透过膜的方法将涂层的发射率降低至0.5,使涂层具备了一定的选择性吸收性能。XRD分析表明,涂层相成分在喷涂及热震前后未发生变化,同时,涂层在600℃循环热震试验后,没有产生脱落现象。这表明涂层具备良好的高温稳定性。
本次试验还以Mn(CH3COO)2、乙醇为原料,通过溶胶-凝胶法制备了Cu1.5Mn1.5O4尖晶石结构太阳能选择性吸收涂层。干凝胶的TG-DSC分析结果表明,450℃时开始形成Cu1.5Mn1.5O4相.。XRD分析结果表明,500℃下退火1h后制备的前驱体粉末以Cu1.5Mn1.5O4为主要成分,并含有少量的CuO, Mn2O3。向溶胶中添加羟丙基纤维素后,溶胶的成膜性能得到提高。烧结过程中,控制升温速率为1℃/min,制备的涂层晶粒排列紧密、粒度平均,涂层表面没有产生明显缺陷。以20mm/min提拉速度提拉2次后制备的涂层厚度约1μm,吸收率0.88,发射率0.05。将涂层在500℃下保温1～30h后,涂层中的原有的少量CuO、Mn2O3转化为Cu1.5Mn1.5O4,涂层的吸收率及发射率均略微上升,吸收率最高至0.91,发射率至0.09,性能未发生衰减。SEM分析结果表明,在保温过程中,涂层中晶粒未发生长大现象,未产生裂纹,更未发生剥落,热稳定性能良好。
Solar spectrally selective absorbing coating which is the most important on the solar energy collector restricts the collector efficiency directly. Majority of the coatings were only for medium-low temperature application, and some even could only be used in vacuum environment due to the influence of materials, structures, and processing methods. Currently, magnetron sputtering technology was used to prepare high-tempeature resistent metal ceramics and multi-layer gradient films, which can be applied to non-vacuum high-temperature surroundings but costly. Plasma sprying technology and sol-gel method with the advantages of simply processing, low cost were popular employed in coating preparation, and large-scale production can be achieved. However, the above methods being directly used to prepare solar selective absorbing coating are rarely reported. As a result, this article completed the experiments.
During the experiment, Cr2O3、Al2O3 and SiO2 were taken as the main drugs, spray drying mathod was employed to obtain spherical powder agglomeration which is spraying powder with excellent mobility. Black chrome solar selective absorbing coating based on stainless steel was prepared by plasma spraying technology. Results indicated that the solar absorptance (α) and thermal emittance (ε) of the coatings were high. After being polished, the thermal emittance of the coatings fell to 0.76. The absorptance changed little but the emittance decreased to 0.50 after SnO2 films were fabricated. The composition did not change after thermal shock test by XRD analysis, it showed the coatings had excellent thermal stability and thermal erosion resistance.
We also obtained the solar selective absorbing coating of Cu1.5Mn1.5O4 with spinel structure from CuCl2, Mn(CH3COO)2 and ethanol through sol-gel method. The dry gel TG-DSC analysis shows that the Cu1.5Mn1.5O4 phase begins to form at 450℃. As can be seen from the XRD patterns analysis that the precursor power prepared by annealing 1 h at 500℃contains Cu1.5Mn1.5O4 mostly, as well as a small amount of CuO and Mn2O3.The gel film-forming property improved with adding hydroxypropyl cellulose into the gel.The coating grains prepared under the sintering heating rate of 1℃/min appeared tightly packing, uniform size, and no visible defects on the surface. After pulled with the speed of 20mm/min twice, we got the coating with the thickness of 1μm, absorption rate of 0.88 and emissivity rate of 0.05. After the coating insulated among 1 to 30h at 500℃, CuO and Mn2O3 transformed into Cu1.5Mn1.5O4, and coating absorption and emissivity rate increased slightly, of the maximum values 0.91 and 0.09, respectively. The SEM images show the coating grains are without growth, and of no cracks or peeling, which means the coating gets a wonderful thermal stability.
本次实验以Cr2O3、Al2O3和SiO2为主要原料,采用喷雾干燥法制成球形团聚粉末,获得流动性好的喷涂用粉。采用等离子喷涂工艺,在不锈钢基体上制备了黑铬太阳能选择性吸收涂层。涂层具备较高的发射率,通过减小表面粗糙度及制备SnO2选择性透过膜的方法将涂层的发射率降低至0.5,使涂层具备了一定的选择性吸收性能。XRD分析表明,涂层相成分在喷涂及热震前后未发生变化,同时,涂层在600℃循环热震试验后,没有产生脱落现象。这表明涂层具备良好的高温稳定性。
本次试验还以Mn(CH3COO)2、乙醇为原料,通过溶胶-凝胶法制备了Cu1.5Mn1.5O4尖晶石结构太阳能选择性吸收涂层。干凝胶的TG-DSC分析结果表明,450℃时开始形成Cu1.5Mn1.5O4相.。XRD分析结果表明,500℃下退火1h后制备的前驱体粉末以Cu1.5Mn1.5O4为主要成分,并含有少量的CuO, Mn2O3。向溶胶中添加羟丙基纤维素后,溶胶的成膜性能得到提高。烧结过程中,控制升温速率为1℃/min,制备的涂层晶粒排列紧密、粒度平均,涂层表面没有产生明显缺陷。以20mm/min提拉速度提拉2次后制备的涂层厚度约1μm,吸收率0.88,发射率0.05。将涂层在500℃下保温1～30h后,涂层中的原有的少量CuO、Mn2O3转化为Cu1.5Mn1.5O4,涂层的吸收率及发射率均略微上升,吸收率最高至0.91,发射率至0.09,性能未发生衰减。SEM分析结果表明,在保温过程中,涂层中晶粒未发生长大现象,未产生裂纹,更未发生剥落,热稳定性能良好。
Solar spectrally selective absorbing coating which is the most important on the solar energy collector restricts the collector efficiency directly. Majority of the coatings were only for medium-low temperature application, and some even could only be used in vacuum environment due to the influence of materials, structures, and processing methods. Currently, magnetron sputtering technology was used to prepare high-tempeature resistent metal ceramics and multi-layer gradient films, which can be applied to non-vacuum high-temperature surroundings but costly. Plasma sprying technology and sol-gel method with the advantages of simply processing, low cost were popular employed in coating preparation, and large-scale production can be achieved. However, the above methods being directly used to prepare solar selective absorbing coating are rarely reported. As a result, this article completed the experiments.
During the experiment, Cr2O3、Al2O3 and SiO2 were taken as the main drugs, spray drying mathod was employed to obtain spherical powder agglomeration which is spraying powder with excellent mobility. Black chrome solar selective absorbing coating based on stainless steel was prepared by plasma spraying technology. Results indicated that the solar absorptance (α) and thermal emittance (ε) of the coatings were high. After being polished, the thermal emittance of the coatings fell to 0.76. The absorptance changed little but the emittance decreased to 0.50 after SnO2 films were fabricated. The composition did not change after thermal shock test by XRD analysis, it showed the coatings had excellent thermal stability and thermal erosion resistance.
We also obtained the solar selective absorbing coating of Cu1.5Mn1.5O4 with spinel structure from CuCl2, Mn(CH3COO)2 and ethanol through sol-gel method. The dry gel TG-DSC analysis shows that the Cu1.5Mn1.5O4 phase begins to form at 450℃. As can be seen from the XRD patterns analysis that the precursor power prepared by annealing 1 h at 500℃contains Cu1.5Mn1.5O4 mostly, as well as a small amount of CuO and Mn2O3.The gel film-forming property improved with adding hydroxypropyl cellulose into the gel.The coating grains prepared under the sintering heating rate of 1℃/min appeared tightly packing, uniform size, and no visible defects on the surface. After pulled with the speed of 20mm/min twice, we got the coating with the thickness of 1μm, absorption rate of 0.88 and emissivity rate of 0.05. After the coating insulated among 1 to 30h at 500℃, CuO and Mn2O3 transformed into Cu1.5Mn1.5O4, and coating absorption and emissivity rate increased slightly, of the maximum values 0.91 and 0.09, respectively. The SEM images show the coating grains are without growth, and of no cracks or peeling, which means the coating gets a wonderful thermal stability.
引文
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[7]陈步亮. Al/Al-N选择性吸收膜.航天器环境工程,1998.54(1)：59-63.
[8]潘永强.直流磁控溅射Cr/Cr2O3金属陶瓷选择吸收薄膜的研究.真空科学与技术学报,2006.26(6)：517-521.
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[22]叶菲.Cr_20_3-MnO_2系高温红外陶瓷涂层的制备与研究.红外技术,2010.32(5)：263-267.
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[2]翟秀静.新能源技术.北京：化学工业出版社,2010：6-7.
[3]王修智.能量之源.济南：山东科学技术出版社,2007：90-91.
[4]左潞.太阳能烟囱发电技术研究进展.河海大学学报,2009.37(1)：41-44.
[5]葛新石.太阳能利用中的光谱选择性涂层.北京：科学出版社,1980.
[6]李金花,宋宽秀,王一平.中高温太阳能光谱选择性吸收涂层的研究进展.化学工业与工程,2004.21(6)：432-436.
[7]陈步亮. Al/Al-N选择性吸收膜.航天器环境工程,1998.54(1)：59-63.
[8]潘永强.直流磁控溅射Cr/Cr2O3金属陶瓷选择吸收薄膜的研究.真空科学与技术学报,2006.26(6)：517-521.
[9]侯玉芝.MOCVD法制备碳-氧化铝太阳能选择吸收涂层的研究.表面技术,2009.38(3)：10-12.
[10]黄群武,王一平,李金花.中温太阳光谱选择性吸收CuO涂层的研制.天津大学学报,2006.39(12)：1485-1489.
[11]黄群武.钼黑太阳能选择性吸收涂层的研制.太阳能学报,2007.28(11)：1217-1220.
[12]M.R. Bayati. Design of chemical composition and optimum working conditions for trivalent black chromium electroplating bath used for solar thermal collectors. Renewable Energy,2005. 30:2163-2178.
[13]赵玉文.硫化铅选择性涂层的研制.太阳能学报,1982.3(1)：61-66.
[14]郝雷.非真空高温太阳光谱选择性吸收涂层的研制.科学通报,2009.54(2)：251-254.
[15]BERGHAUS A, DJAHANBAKHSH A, THOMAS L K. Characterisation of CVD-tungsten-alumina cermets for high-temperature selective absorbers[J]. Solar Energy Materials and Solar cells,1998.54:19-26.
[16]吴桂初,粉末火焰喷涂法制备黑铬太阳能选择性吸收涂层的实验研究.太阳能学报,1999.20(2)：187-189.
[17]Xiaodong He. High emissivity coatings for high temperature application:Progress and prospect. Thin Solid Films,2009.517:5120-5129.
[18]R.M. Li. Radiation properties modeling for plasma-sprayed-alumina-coated rough surfaces for spacecrafts. Materials Science and Engineering,2006.132:209-214.
[19]周基炜.红外高发射陶瓷涂层发射率与厚度关系.复合材料学报,2007.24(2)：86-91.
[20]李丹虹.NiCr尖晶石型高热发射率陶瓷涂层的制备、结构与性能的研究：[硕士学位论文].武汉：武汉理工大学,2006.
[21]陈武.高温高发射率红外辐射涂层的制备与研究：[硕士学位论文].武汉：武汉理工大学,2006.
[22]叶菲.Cr_20_3-MnO_2系高温红外陶瓷涂层的制备与研究.红外技术,2010.32(5)：263-267.
[23]李西忠.FeMnCuO4/硅聚合物太阳光谱选择性吸收涂层的研究.合肥工业大学学报,1992.
15(3)：78-83.
[24]刘胜峰.太阳光谱选择性吸收涂层新型颜料的合成研究.太阳能学报,1994.15(3)：300-304.
[25]王华林.FeMnCuO4复合氧化物的光热转换.太阳能学报,1999.20(1)：79-80.
[26]杨开怀.溶胶-凝胶法制备CuMnCuO4复合氧化物的工艺研究.太阳能学报,2009.30(6)：769-773.
[27]Orel. Z.C. Spectrally selective paint coatings:Preparation and characterizations. Solar Energy Materials & Solar Cells,2001.68:337-353.
[28]宋文学.墨绿色太阳能选择性吸收涂层.太阳能学报,1997.18(2)：233-236.
[29]LEON KALULZA. Structural and IR Spectroscopic Analysis of Sol-Gel Processed CuFeMnO4 Spinel and CuFeMnO4/Silica Films for Solar Absorbers. Journal of Sol-Gel Science and Technology,2001.20:61-83.
[30]LEON KALULZA. Sol-gel derived CuCoMnOx spinel coatings for solar absorbers: Structural and optical properties. Solar Energy Materials & Solar Cells,2001.70:187-201.
[31]J. Vince. Solar absorber coatings based on CoCuMnOx spinels prepared via the sol-gel process:structural and optical properties. Solar Energy Materials & Solar Cells,2003.79: 313-330.
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