Abstract
A metal layer with high reflectance is widely used as the bottom mirror of smart radiation devices. Reduced solar absorption and enhanced emittance tunability are required for smart radiation devices applied in aerospace. Thus, reducing the absorption in the metal is also necessary. Here, Al films have been prepared by direct current magnetron sputtering on the fused silica substrate. The structure, morphology, and optical properties of the films have been analyzed at various deposition temperatures and deposition times. The spectrum absorption tends to increase with the increase of surface roughness due to the agglomeration and size increase of Al particles, which has been further demonstrated by the simulated results. The optimized Al film exhibits small solar absorption of 0.14 and low emittance of 0.02, which benefits the application for smart radiation devices and solar reflectors.
Highlights
The smart radiation device (SRD) is a promising technology for the thermal radiation regulation of spacecraft and satellites since they constitute the physical interface between the thermal management system and the space environment [1,2,3]
The Al films were deposited by the direct current magnetron sputtering (DCMS) method (MS650C, KeYou, Shenyang, China) from Al target (99.999%) onto 1 mm-thick fused silica substrate, which was dried after washing for 15 min both in acetone and ethyl alcohol using an ultrasonic cleaner to remove impurities on the substrate surface
The thin film was characterized by grazing incidence XRD in order to obtain Al characteristic diffraction peaks
Summary
The smart radiation device (SRD) is a promising technology for the thermal radiation regulation of spacecraft and satellites since they constitute the physical interface between the thermal management system and the space environment [1,2,3]. The most promising SRD configuration consists of a bottom mirror, followed by a dielectric resonant cavity, and an active VO2 film, which could dynamically regulate its radiation in response to the temperature [4]. An ideal dynamic SRD should have both a high infrared (IR) emittance tunability to achieve heat dissipation and preservation, and a low solar absorption to reflect the solar radiation [3,4]. To reduce the solar absorption of SRD, it is necessary to select the metal layer with low solar absorption. The aluminum (Al) film is widely used as the highly reflective broadband mirror for its low costs, easy preparation, and high intrinsic reflectivity from the far-ultraviolet to far-infrared [3,9]. Ning et al investigated the thermal emittance of Al films in the solar selective absorbing coating, and the lowest thermal emittance for the Al film with the optimal thickness of 78 nm was obtained [10]
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