Stability of W-Al2O3 cermet based solar coating for receiver tube operating at high temperature
Stability of W-Al2O3 cermet based solar coating for receiver tube operating at high temperature
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DOI：
10.1016/j.solmat.2010.04.080
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发表时间：
2010-10-01
影响因子：
6.9
通讯作者：
Esposito, S.
中科院分区：
文献类型：
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作者：
Antonaia, A.;Castaldo, A.;Esposito, S.
采用磁控溅射技术制备了一种优化的W-Al_2 O_3梯度金属陶瓷太阳能多层膜。为了将这种涂层用于太阳能抛物槽式装置的接收管，它必须在真空下的高温（580摄氏度）下具有非常高的结构、物理和化学稳定性，在高太阳能吸收和低热发射率方面保持良好的性能。我们的涂层的稳定性进行了调查，通过在高温退火过程之前和之后的几种材料表征。在这项研究中出现的显着特点是部分氧化的钨纳米颗粒内的金属陶瓷形成壳的WOx，成核的纳米晶体多孔氧化铝γ相的基体中的主要非晶和相转变从β到α的钨背反射器。所有这些现象都是温度升高促进涂层反射率改变的原因。然而，我们证实这种光光学改性不是渐进的，而是在2天的退火时间下达到涂层光学性质的确定性调整，证明该太阳能涂层在真空下具有显著的热稳定性，并且使其非常适合在高温下使用。(C)2010爱思唯尔有限公司版权所有。
An optimized solar multilayer coating based on W-Al2O3 graded cermet layer was fabricated in our laboratories by magnetron sputtering technique. To use this coating for the receiver tube of solar parabolic trough plants it is necessary for it to have very high structural, physical and chemical stability at high temperature (580 degrees C) under vacuum, maintaining good performances in terms of high solar absorption and low thermal emissivity. An investigation on the stability of our coating was carried out by means of several material characterizations before and after annealing processes at high temperature. The salient characteristics emerging in this study were the partial oxidation of the tungsten nano-particles inside the cermet forming shells of WOx, the nucleation of a nano-crystalline porous alumina gamma phase in the matrix of the prevailing amorphous one and the phase transition from beta to alpha of the tungsten back-reflector. All these phenomena were responsible for the coating reflectance modification promoted by the increased temperature. However we verified that such light optical modification was not progressive but at an annealing time of 2 days a definitive adjustment of the coating optical properties was reached, attesting to a remarkable thermal stability of this solar coating under vacuum and making it very suitable to be used at high temperature. (C) 2010 Elsevier B.V. All rights reserved.