逆向热蒸发制备望远镜主镜银反射膜

以自上向下热蒸发大型镀膜机为实验平台,开展了逆向蒸发制备大口径银反射镜研究.通过设计特殊蒸发舟及优化相关工艺参数,实现了金属银膜稳定、高速向下蒸发.根据逆向热蒸发工艺特点,选取熔点低、升华型材料Cr和SiO及特殊设计的蒸发舟,以Cr或CrNx为粘结层,SiOx或SiOxNy为保护层,制备了三种具有四层结构的介质保护性银反射膜,并对所制备反射镜样品的反射率、断面形貌和环境稳定性进行了表征.实验结果表明:膜系结构为3 nmCr/120 nmAg/0.6 nmCrNx/150 nmSiOxNy的银反射膜具有较好的环境稳定性和光谱特性;通过了24小时湿热实验(50℃/相对湿度98％/)和盐雾实验,在400～1 800 nm波段光谱范围内,银反射膜的平均反射率达到97.8％.     

SiOx protective film thermally evaporated downwards for 2-m level primary mirror

The service life of the large primary mirror with aluminum coating can be effectively prolonged by a protective layer. The SiOx （1〈x〈2） protective material which is thermally evaporated from up to bottom is studied. Environmental adaptability experiment, spectral measurement and micro-morphology analysis are executed on bare SiOx coatings within different oxygen concentrations, and the repeatability verification is implemented by testing the SiOx protected aluminum coatings. The results show that the SiOx coatings can meet the protective qualification within oxygen flow of 50 sccm （p=5.6× 10-3 Pa）. The fine compactness of the coating has excellent moisture resistance with the average molecular spacing of 0.335 nm. In addition, the average reflectivity of the SiOx protected aluminum coating is 90.47% in the band 400 --2 500 nm and the coating is confirmed to have good environmental performance.