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The application of phase-change materials (PCMs) for solar energy utilization and thermal energy storage is limited by their low thermal conductivity, undesirable solar-thermal conversion efficienc...

Development of low-cost equipment that can store clean energy, such as solar energy, is effective for alleviating environmental pollution. In this study, the shape-stabilized composite phase change materials (PCMs) based on paraffin wax and carbon foam were prepared. The carbon foam prepared from melamine foam had a good pore structure and was used to encapsulate paraffin wax. The latent heat of melting and cooling of composite PCMs were 221.1 J/g and 213.7 J/g, respectively. Even after 100 cycles, it still showed good thermal performance. Meanwhile, the composite PCMs exhibited good light-to-heat conversion efficiencies of 53.94% and 67.43% at light intensities of 200 mW cm−2 and 300 mW cm−2, respectively. Overall, composite PCMs with excellent thermal performance and cycle stability have application prospects in industries such as construction, solar energy, and battery temperature-control systems.

The limited light absorption, low thermal conductivity, and poor shape stability restrict the widespread application of organic phase change materials (PCMs). Herein, carbon foam (CF) with the light, inter-connective porous, and high-strength was developed based on the phenolic resin to encapsulate organic PCMs, and multi-walled carbon nanotubes (MWCNTs) were added to improve the compressive strength and light absorption at the same time. Then, the polyethylene glycol (PEG) was encapsulated in the CF/MWCNTs composite via a vacuum impregnation method. The modified CF composite could act as an efficient heat transfer channel to improve the thermal conductivity and light-thermal conversion efficiency of PEG. As a result, the PEG/CF composites displayed a high latent enthalpy (156.3 J/g to 170.9 J/g) and an excellent light-thermal conversion efficiency (61%–74%). Furthermore, the PEG/CF10 exhibited the highest thermal conductivity of 0.68 W/(m∙K), which is about 2.24 times higher than that of pure PEG. The as-prepared PEG/CF composites with mechanical strength and thermal stability could exhibit great potential in solar energy utilization, building energy conservation, and waste heat recovery.

A new optical thermometer material—Er3+-doped SrNb2O6—based on the fluorescence intensity ratio was synthesized and investigated by both theoretical calculation and experimental measurement, combining X-ray diffractometry (XRD), XRD Rietveld refinement, scanning electron microscopy, X-ray photon emission spectroscopy, photoluminescence (PL) and PL excitation of qualitative and quantitative analysis, to develop a novel green-emitting phosphor with excellent thermometry sensitivity. The Er3+ ions occupied 4e sites of SrNb2O6, and the stable activator occupation induces luminescence properties of emissions at 525, 531, and 550 nm. The SrNb2O6: Er3+ phosphor possesses an outstanding thermal sensitivity in the measurement region of 298–523 K, where Sa and Sr can achieve 6.15 × 10−3 K−1 and 1093.2711/T2, respectively, at 323 K. The optical thermal properties originated from the thermal excitation and formation of quashing thermal equilibrium between 2H11/2 and 4S3/2 levels, leading to photons on 4S3/2 → 4I15/2 transfer process thermally populate onto 2H11/2 → 4I15/2 transfer process. This work will lay a foundation for further exploration of activator suitability in columbite phosphors, making it practicable to foreseeably improve thermal sensitivity and PL for emergent applications in optical thermometer.

In this paper, a composite phase change material based on paraffin and carbon foam derived from starch was prepared. The paraffin was encapsulated in the carbon foam, which was prepared by using a foaming and steaming method at different carbonization temperatures. Carbon foams comprised amorphous carbon and were impregnated with paraffin to obtain the paraffin/carbon foam composites (PCCs). When carbonized at 1100 °C, the loading percentage of the carbon foam enabled to reach maximum 72.79%. Paraffin encapsulation did not result in any new structure or chemical bonds involved or change in the geometry. The latent heats of the sample were 174.3 J/g at the melting temperature (47.9 °C), and 151.4 J/g at the freezing temperature (52.8 °C). Thermal conductivity of PCCs reached up to 1.93 times than that of paraffin. The composite phase change material fabrication was cost–effective, environment friendly, chemically stable, and suitable for energy–efficient building applications.

The fabrication and luminescent performance of novel phosphors Na2YMg2V3O12:Dy3+ were investigated by a conventional solid-state reaction method. Under near-UV light, the Na2YMg2V3O12 host self-activated and released a broad emission band (400&ndash, 700 nm, with a peak at 524 nm) ascribable to charge transfer in the (VO4)3&minus, groups. Meanwhile, the Na2YMg2V3O12:Dy3+ phosphors emitted bright yellow light within both the broad emission band of the (VO4)3- groups and the sharp peaks of the Dy3+ ions at 490, 582, and 663 nm at a quenching concentration of 0.03 mol. The emission of the as-prepared Na2YMg2V3O12:Dy3+ phosphors remained stable at high temperatures. The obtained phosphors, commercial Y2O3:Eu3+ red phosphors, and BaMgAl10O17:Eu2+ blue phosphors were packed into a white light-emitting diode (WLED) device with a near-UV chip. The designed WLED emitted bright white light with good chromaticity coordinates (0.331, 0.361), satisfactory color rendering index (80.2), and proper correlation to a color temperature (7364 K). These results indicate the potential utility of Na2YMg2V3O12:Dy3+ phosphor as a yellow-emitting phosphor in solid-state illumination.