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Graphene encapsulating paraffin (paraffin@graphene) microcapsules were fabricated by electrostatic interaction-based self-assembly. An aqueous dispersion of graphene sheets charged with cation, were mixed with a water-based emulsion containning negatively charged paraffin droplet spheres to form self-assembled microcapsules. The morphology of the microcapsules was characterized by scanning electron microscope (SEM). Results show that the microcapsules with a well-defined spherical structure were prepared successfully. Differential scanning calorimeter (DSC) results indicate that the phase change latent heat are all above 200 J g−1. With a graphene mass fraction of 8 wt%, the thermal conductivity of the fabricated composites can reach 1.73 W m−1 K−1. Attributing to the interlocking of graphene with each other, the microcapsules enable lock the paraffin in the shell thus successfully avoiding its leakage during phase change process. The prepared phase change microcapsules are expected to apply in energy storage field. [ABSTRACT FROM AUTHOR]

Two kinds of carbon aerogels, graphene aerogels (GA) and carbon nanotubes-graphene aerogels (CGA), were prepared by modified hydrothermal method. The form-stable phase change materials (PCMs) were fabricated by adsorbing paraffin into carbon aerogels. Morphology, structure, form stability and thermal property were characterized by scanning electron microscope (SEM),in situX-ray diffraction (in situXRD) and differential scanning calorimeter (DSC). The results showed that GA presented wrinkled surface textures with curling edges, and carbon nanotubes (CNTs) were interspersed or attached to GA sheets. The phase transition temperature and the phase change enthalpy of the GA/paraffin PCM composite were 48.7 °C and 223.2 J/g, respectively. Thermal and mechanical properties of PCM composites achieved a qualitative leap with the adding of carbon aerogels. The PCM composites had a thermal conductivity of about 2.182 W/m K at the carbon aerogels loading fraction of 2 wt%. The form-stable PCM composites with high thermal conductivity and high enthalpy could be promising for thermal energy storage applications in construction field. [ABSTRACT FROM PUBLISHER]

Abstract A series of paraffin/expanded graphite (EG) composites with various mass fraction were prepared. The microscopic geometry configuration, thermal conductivity and saturation sorption capacity of EG were obtained. In this paper, a method based on the experiments of EG pores was proposed for constructing geometric models. The geometric model constructed by this method has obvious anisotropy and has been employed in the calculation. Furthermore, the numerical results of thermal conductivity indicate anisotropy of a single-pore. Moreover, it had been observed by experiment that the anisotropy is weakened and transformed to isotropy in the process of combining geometric models with a large number of single pores. The final numerical results agree well with the experiments, which validates the precision and reliability of the proposed model. The increasement of thermal conductivity is also calculated and discussed during the phase change process of paraffin/EG. Highlights • A method of EG pores was proposed for constructing geometric models which has obvious anisotropy. • The SEM micrograph and saturation sorption capacity are employed to build the geometric models of EG pores. • Effective thermal conductivity during non-phase change process and the phase change process was calculated. • The numerical results agree well with the experiments. [ABSTRACT FROM AUTHOR]