We report thermal radiation antennas that sustain large emissivity at a broad range of wavelengths and angles, as well as maintaining their emissivity at high temperatures (up to 1300 K) under atmospheric pressure. Two-dimensional arrays composed of tungsten (W) cones with high aspect ratio were fabricated by laser interference lithography followed by deep reactive-ion etching, then optically characterized by measuring the broadband (λ = 500–2500 nm) absorptivity spectra. The fabricated W radiation antennas yielded greater absorptivity in visible to near-infrared wavelengths by increasing the aspect ratio of the cones, resulting in a near two-fold enhancement in average absorptivity compared to a reference planar W substrate. The measured absorptivity spectra were reproduced well by electromagnetic simulations with the experimental optical constants of W. Electromagnetic simulations also verified that such broadband increases in absorptivity are mostly caused by the enlarged scattering cross-section of individual cones. A 120 nm-thick conformal alumina coating prepared by atomic layer deposition was employed to prevent surface oxidation of the fabricated W radiation antennas, which additionally improved their absorptivity through an amplified antenna effect. These experimental and theoretical findings are generalizable to different infrared spectra by simply scaling up the antenna structures, and thus will be extensively utilized in thermal radiation applications such as solar steamers, thermophotovoltaics, and radiative coolers.

Owing to their natural abundance and exceptional mechanical properties, cellulose fibers (CFs) have been used for reinforcing polymers. Despite these merits, dispersing hydrophilic CFs in a hydrophobic polymer matrix is challenging. To address this, an amphiphilic ammonium salt was employed as the dispersant for CFs in this study. The hydrophobic CFs were mixed with a healable polymer to produce CF-reinforced composites. As the thermosetting polymer was crosslinked with Diels–Alder (DA) adducts, it was mended and recycled via a retro DA reaction at 120 °C. Interestingly, the CF-reinforced polymer composites were mended and recycled as well. When 5 wt % of the hydrophobic CFs was added to the polymer, maximum tensile strength, elongation at break, Young’s modulus, and toughness increased by 70%, 183%, 75%, and 420%, respectively. After recycling, the CF-reinforced composites still featured better mechanical properties than recycled polymer.

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