AlON/TiAlON_D/TiAlON_M/Cu光谱选择性吸收涂层高温真空稳定性研究

Thermal Stability of AlON/TiAlON_D/TiAlON_M/Cu Solar Selective Coating at High Temperature under Vacuum

利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、透射电镜(TEM)和俄歇电子能谱仪(AES)研究了AlON/TiAlON_D/TiAlON_M/Cu选择性吸收涂层高温真空条件下显微形貌、结构与化学成分的变化。结果表明,退火前后选择性吸收涂层的多层膜结构和微观形貌保持稳定。制备态涂层的AlON层和TiAlON_D层为非晶结构,TiAlON_M层由非晶基体和分散的晶粒组成。550℃高温真空退火24 h后,TiAlON_M层发生晶化,晶粒长大。退火过程中,O元素从AlON层扩散至TiAlON双吸收层,而N元素从TiAlON双吸收层扩散至AlON层,同时膜层界面区域变宽。高温真空处理后涂层的吸收率略有降低,而发射率保持不变。晶化导致TiAlON_M层吸光性能下降,以及N和O元素扩散导致最优化结构被破坏是涂层吸收率衰减的主要原因。涂层在真空下热稳定激活能为189.5 k J·mol^(-1),表明涂层具有较好的热稳定性。

Scanning electron microscope （SEM）, X-ray diffractometer （XRD）, transmission electron microscope （TEM） and Auger electron spectroscopy （AES） were used to study the micro-morphology, structure and profile chemical composition of AlON/TiA1OND/ TiAlONM/Cu solar selective coating. The results showed the muhilayer structure and micro-morphology of the coating kept stable after annealing. The A1ON and TiAlOND layers of as-deposited coating were amorphous and the TiAlONM layer was consisted of amorphous matrix and dispersive grains. The TiA1ONM layer got crystallized and the grains grew up after annealing at 550 ℃ for 24 h. In the process of annealing, N atoms diffused from TiAION double-absorbing layer into A1ON layer, whereas 0 atoms diffused from A1ON layer into TiA1ON double-absorbing layer. The elements diffusion also broadened the interfaces of the sub-layers. The absurptance of the coating slightly decreased and the emittance kept unchanged after annealing in vacuum. The degradation of the absorptance was due to the decrease of TiA1ONM layer＇s light-absorbing capacity caused by crystallization and the destruction of optimized structure caused by elements diffusion. The activation energy of the solar selective coating was 189.5 kJ·mol^-1, indicating a good thermal stability of the coating.