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The efficient use of solar energy can alleviate the energy shortage, so the photothermal conversion materials have been a hot spot for research. Improved thermal conductivity and higher enthalpy/flexibility can expand the practical application scenarios of photothermal conversion materials. Therefore, a flexible composite material for photothermal conversion is developed in this paper. Among them, carbon nanotube (MWCNT) is the photothermal conversion material, melamine foam (MF) is the supporting skeleton of the composite, and paraffin wax (PW) is the phase change material. According to the results, MWCNT/MF/PW has a high latent enthalpy of 240 J/g. The thermal conductivity of MWCNT/MF/PW (0.129 W/m·K) was improved by 95.5% compared to MF/PW (0.066 W/m·K). MWCNT/MF/PW have a high photo-thermal conversion efficiency (85.16%). Hence, MWCNT/MF/PW exhibit excellent shape recovery due to the response to light and heat. In addition, the outdoor light absorption experiment of the composite PCM water tank indicates that MWCNT/MF/PW as a shell wrapped water tank shows good light absorption and heat preservation effect, which is not available for general photothermal conversion materials. • The MWCNT, MF and PW composite phase change materials were prepared. • The light/heat shape recovery properties of CPCMs with MWCNT was investigated. • The light-absorbing property (85.16%) of composites was studied. • The insulating effect of MWCNT/MF/PW on tank temperature was investigated. [ABSTRACT FROM AUTHOR]

Green, stable, and high-performance phase change materials with photothermal/electrothermal capabilities are crucial for solar thermal utilization. In this paper, biomass cellulose nanocrystals (CNCs), konjac glucomannan (KGM), MXene (a two-dimensional material), and AgNO 3 were first mixed through a simple and fast physical process and then subject to directional freeze-drying and thermal annealing successively. The resulting lightweight porous carbon aerogels further adsorbed paraffin to yield a composite phase change material PMCKA. PMCKA had a high loading rate (95.16%), high enthalpy (231.38 J/g), exceptional conductivity (147.5 S/m), and remarkable cycle stability. Moreover, the photothermal and electrothermal conversion efficiencies of PMCKA might reach up to 97.45% and 98.89%, respectively. This finding demonstrates superior photothermal and electrothermal conversion performance of PMCKA in solar energy storage. Therefore, PMCKA can probably be widely applied to solar thermal conversion, industrial waste heat recovery, and thermal management of electronic equipment. [Display omitted] • The preparation method of bio-based PMCKA is simple and efficient. • PMCKA has ideal heat storage performance, excellent cycle stability, and thermal stability. • PMCKA has excellent photothermal conversion capability and can effectively recycle solar energy. • PMCKA has good electrothermal cycle stability and adjustability at different voltages. [ABSTRACT FROM AUTHOR]

In this study, expanded graphite (EG)/paraffin (PA)/silica (SiO 2) composite phase change materials (PCM), with good thermal conductivity and impermeability, were fabricated for potential applications in solar energy. The EG-PA was first prepared by vacuum adsorption and then encapsulated by SiO 2 through solid-phase wet grinding in the presence of sodium silicate. Our results show that the EG-PA-SiO 2 composite have optimal properties when the mass ratio of raw material is PA: sodium silicate: H 2 O = 1:9:2:8. The latent heat of melting of the EG-PA-SiO 2 composite prepared at this mass ratio is 106.2 J/g. The core material loss ratio, after washing with petroleum ether, is 4.79%. The thermal conductivity is 2.053 W/m·K, which is 8.5 times higher than that of pure paraffin wax, and the melt permeability is 9.35% after 120 min at 60 °C. Under simulated sunlight, the time required for the composite material to change from 30 °C to 65 °C is reduced by 70.78% compared to PA and the heat absorption and release times are nearly unchanged under multiple cycles. These results indicate that the material has a stable photothermal conversion efficiency. [Display omitted] • Expanded graphite, paraffin and silica composites were made by solid-phase wet grinding method. • Silica encapsulated the composite, reducing leakage. • Composites showed improved thermal conductivity and impermeability. • The composite has stable photothermal conversion, and there is no obvious leaking sign. [ABSTRACT FROM AUTHOR]