MXene/rGO grafted sponge with an integrated hydrophobic structure towards light-driven phase change composites

While phase change materials (PCMs) have great potential for use in solar energy storage, they suffer from a lack of shape stability and energy conversion ability. In this study, proper amination of melamine sponge (MS) was designed to construct an integrated MXene and reduced graphene oxide (rGO) structure. The MXene/rGO layer is sufficiently robust to endure the capillary pressure caused by solvent evaporation during the airdrying process. In addition, the reduction of GO using oleylamine (OA) contributes to the protection of MXene from oxidation by preventing the surface of MXene nanosheets from being exposed to oxygen and moisture. The as-designed MXene/rGO sponges have been shown to effectively enhance the thermophysical and photo absorption properties of paraffin wax (PW) in the composite PCM. The composite with the highest amount of MXene/rGO maintained 93.3% of the latent heat of pure PW. The photothermal storage efficiency can reach as high as 93.0% at an MXene content of around 1%. A thermal conductivity enhancement of 66.9% can be achieved compared to the pure MS/PW composite. Therefore, this study presents a new approach for designing of high-performance phase change composites for waste-heat recovery and solar thermal energy storage applications.</p

Parametric study on the thermal performance enhancement of a thermosyphon heat pipe using covalent functionalized graphene nanofluids

Heat transfer characteristics of copper sintered heat pipe explored using a modified graphene nanoplatelets (GNP)-containing nanofluid with great dispersion stability as a novel working fluid. Firstly, a water dispersible GNP with specific desire was synthesized by the reaction of GNP sheets with the diazonium salt (DS) of sodium 4-aminoazobenzene-4-sulfonate. An X-ray photoelectron spectroscopy (XPS) test shown successful covalent functionalization of GNP using DS which provided special water dispersibility characteristics. The results indicate that the thermal conductivity enhancement was up to 17% by adding modified GNP sheets in the base fluid. It also, exhibited a maximum sedimentation of 16% after 840 hrs. Further research works were carried on thermal performance of heat pipe by varying nanofluid concentrations, filling ratio, input heating powers and inclination angles of heat pipes. The results proof that the maximum enhancements of the effective thermal conductivity and reduction in thermal resistance for purposed nanofluid atφ = 5% were 105% and 26.4%, respectively. Moreover, these good features of the GNP/DS nanofluid make it a very promising working fluid to enhance the thermal performance and efficiency of the current heat pipe systems

Facile Preparation of Carbon Microcapsules Containing Phase-Change Material with Enhanced Thermal Properties

This study describes the hydrothermal synthesis of a novel carbon/palmitic acid (PA) microencapsulated phase change material (MEPCM). The field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) images confirm that spherical capsules of uniform size were formed with a mean diameter of 6.42 μm. The melting and freezing temperature were found to be slightly lower than those of pure PA with little undercooling. The composite retained 75% of the latent heat of pure PA. Thermal stability of the MEPCM was found to be better than that of pure PA. The thermal conductivity of MEPCM was increased by as much as 41% at 30°C. Due to its good thermal properties and chemical and mechanical stability, the carbon/PA MEPCM displays a good potential for thermal energy storage systems