Self‐Doped TiAl Nanoparticle/AlN Metal‐Cermet Solar Selective Absorbing Films

Abstract

which can absorb solar radiation with energy that larger than the bandgap. The photothermal conversion includes hightemperature use (100-400 °C), such as water heating, distillation and desalination. [12,13] At elevated temperatures from 400 to 500 °C or higher, such as parabolic trough collectors, SSAFs are required to have excellent thermal stability. [8,14] The high temperature thermostability is a key hurdle toward real applications of SSAFs. Hence, it is of great significance to study the high-temperature thermal stability of metal-dielectric composites.AlN has excellent attention in fabricating SSAFs due to the high thermal conductivity, dielectric resistance, and chemical stability. Meanwhile, Ti has high hardness and excellent thermal stability at high temperatures, as well as outstanding inoxidizability. Hence the Ti is a good candidate for IR reflector and diffusion barrier at elevated temperatures in SSAFs, while AlN is suitable for the absorber layer. In this type of SSAF, metal particles (NPs) are usually embedded in the highly infrared reflective substrate. While optical properties can be optimized by varying the NPs concentration, size and thickness. [15] Metal NPs are unstable at high temperature, which is unsuitable for usage. Alloying is an effective way to enhance metal high temperature stability. [16,17] Schuh et al. [18] propased alloy stability based on a novel thermodynamic model is applied to design stable nanostructured tungsten alloys. And an outstanding candidate alloy is Wti. [18,19] Since then, an alloy stability map was gradually demonstrated, including AgAl, [20,21] AgAu, [22] PtNi, [23] etc. To date, NPs have been proved to have excellent thermal stability at elevated temperatures up to ≈1000 °C, which is ascribed to the segregation and occupation of alloying. This is mainly due to the heterogeneous chemical distribution that is based on conventional bulk thermodynamics and plasmonic effect. [24][25][26] In recent years, Me-AlN (Me = metal) thin films with variable optical properties have been reported as the extraordinary photothermal material. [27] And due to its excellent hightemperature resistant performance in vacuum environment, which was widely used in all-glass evacuated solar collection tubes in China with large quantities. The main advantage of manufacturing Ti-AlN absorber coating is that the commercial production procedure requires only aluminum and titanium targets. But improving the films' high-temperature thermal stability is still one of the critical issues to be addressed. Besides, the SSAFs are usually black or dark blue to pursue high solar Metal-cermet solar selective absorber films (SSAFs) with nanoparticles embedded in dielectric matrix have been widely used in the field of solar thermal conversion. A new SSAF of TiAlN is fabricated via magnetron sputtering method. By co-sputtering Ti and Al targets, TiAl nanoparticles are embedded in AlN matrix to form self-doped absorber layer. And the outermost rough AlN antireflective layer further enhances the optical pr...

Guar Gum-Based Macroporous Hygroscopic Polymer for Efficient Atmospheric Water Harvesting

“…Solar-driven atmospheric water harvesting technology (SAWH) provides a sustainable and environmentally friendly method to generate fresh water, regardless of geographical location . In recent years, the technology has received increasing attention from researchers aiming to address the increasingly severe global water scarcity crisis. − SAWH has been inspired by solar interface evaporation − and passive radiative cooling, − which has been rapidly developed. Its basic principle is to use hygroscopic materials to spontaneously collect atmosphere moisture and store it inside the materials, effectively use sunlight to generate heat and as a driving force to promote the release of water vapor in the hygroscopic material, and finally convert the water vapor into droplets through direct condensation or other technical means to complete the collection of atmosphere moisture. , With the rapid development of SAWH, it has been gradually applied to agricultural irrigation − and human life. , …”