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A simple graphene-carbon nanotube aerogel composite was prepared. In this paper, we studied the three-dimensional (3 D) thermally conductive frameworks with different ratios of graphene oxide (GO) and carbon nanotubes (CNTs). The effects of 3 D thermal conductive frameworks with different ratios of GO and CNT on the morphology, structure and thermal conductivity of phase change composites were also studied. The results show that the 3 D thermally conductive framework has the advantages of managing the thermal conductivity of phase change composites. The obtained phase change composite with only 1 wt% of graphene-carbon nanotube aerogels showed top-quality thermal conductivity of 0.76 W/m·K. The preparation process was simple and has the advantage of environmental protection, so which was suitable for practical applications using polyethylene glycol/graphene-carbon nanotube aerogel phase change composite as energy materials, and has manageable energy conversion, storage and thermal conductivity properties. [ABSTRACT FROM AUTHOR]

A novel kind of paraffin-based shape-stable phase change materials (SSPCMs) was prepared by introducing paraffin into reduced graphene oxide (rGO)/carbon nanotubes (CNTs) aerogel via vacuum-assisted impregnation method. The effects of ratio of rGO to CNTs in 3D network structure on morphology, structure and property of paraffin-based SSPCMs were investigated. The rGO/CNTs 3D network structure with high thermal conductivity, served as thermally conductive skeleton together. In particular, CNTs was used as a secondary heat conductive filler, which could be well dispered in the SSPCMs to conduct heat synergistically. The SSPCMs exhibited high thermal conductivity and excellent shape-stability. And the thermal conductivity of SSPCMs can be regulated by adjusting the ratio of rGO to CNTs in aerogels. These results indicate that 3D rGO/CNTs aerogels have advantages as thermally conductive skeleton, and can endow phase transition materials with stable shape, so as to realize the application of phase change materials in the field of heat dissipation. [ABSTRACT FROM AUTHOR]

• MF/GA double-skeleton with excellent mechanical property is constructed by in situ self-assembly method. • Dual-skeleton based MF/GA@PEG SSPCMs possess superior shape memory property and solar-thermal conversion ability. • Anti-leakage mechanism of MF/GA@PEG SSPCMs is proposed. • This design strategy provides a new application of MF/GA@PEG SSPCMs in microelectronic devices. Polyethylene glycol (PEG) is widely used for thermal energy storage, but its practical application is limited by its strong rigidity, poor shape stability. In this work, a kind of melamine foam/graphene aerogel (MF/GA) double-skeleton was prepared, then PEG was stably encapsulated into MF/GA by vacuum melt impregnation method to obtain MF/GA@PEG shape-stabilized phase change materials (SSPCMs). Structural characterization and performance tests were performed on MF/GA@PEG SSPCMs, including morphological observation, latent heat, thermal conductivity, shape stability, and photothermal conversion capability. The experimental results show that the MF/GA@PEG SSPCMs show high energy storage density (168.3 J/g), good shape stability, shape memory performance and excellent solar-thermal energy conversion capability with a high efficiency of 84.8%, the thermal conductivity of MF/GA@PEG SSPCMs is 161% higher than that of pure PEG. The MF/GA@PEG SSPCMs with comprehensive properties have promising application in solar-thermal energy storage and thermal management in microelectronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Shape-stabilized phase change material (SSPCM) are widely used as energy storage materials due to its advantages of easy preparation and adjustable scale. But the thermal conductivity enhancement of SSPCM still need to be further studied to improve the energy storage efficiency. In this work, silicone rubber (SR)/paraffin@SiO 2 (Pn@SiO 2)/graphene nanoplates (GNPs) shape-stabilized phase change materials (SPG) with different GNPs content were prepared. Pn@SiO 2 and GNPs can be homogeneously dispersed in the SR matrix due to the enhanced interfacial compatibility between Pn@SiO 2 and SR. The leakage rate of SPG composites was as low as 0.25% due to the protection of SiO 2 shell, SR matrix and GNPs. The SPG composites had excellent thermal storage properties, with the enthalpy about 50 J·g−1. The thermal conductivity of SPG composites was improved with the content of GNPs, the thermal conductivity of SPG reach 0.989 W·m−1·K−1 at a GNPs content of 10 phr. The low hardness of SPG composites above the phase change temperature can provide a more cohesive surface when applied to heat dissipation. The heat dissipation of the SPG composites in electric devices was simulated and demonstrated that the addition of GNPs made the heat dissipation rate of the SPG composites increased significantly. Therefore, the SPG composites can be applied in thermal energy storage and heat dissipation of electronic devices. [Display omitted] • The thermal conductivity enhancement of SSPCM was further discussed. • The interfacial compatibility of components in the SSPCM was enhanced by the rational strategy. • The leakage-prevention performance of SSPCM was improved with the multiple protection. • The thermal conductivity of SSPCM reach 0.989 W·m−1·K−1 due to the well-dispersed GNPs and Pn@SiO 2 in SR. • Numerical simulation was used to predict the thermal performance of SPG composites. [ABSTRACT FROM AUTHOR]

Microencapsulation of paraffin with melamine formaldehyde shell (Pn@MF) shows the drawbacks of low thermal conductivity. Hence, we constructed SiO2 shells on Pn@MF phase change microcapsules by interfacial polycondensation to obtain Pn@MF@SiO2 double‐shelled microcapsules. The effect of tetraethoxysilane (TEOS) contents on the performance of Pn@MF@SiO2 was discussed in detail. As the TEOS contents increased, the thermal conductivity of Pn@MF@SiO2 gradually increased, reaching up to 0.376 W m−1 K−1. The Pn@MF@SiO2 have exhibited superior leakage‐proof properties and thermal reliability through double‐shelled protection, and the highest reduction in leakage rate reached 45.06 % compared to Pn@MF microcapsules. The Pn@MF@SiO2‐3 with the lowest enthalpy still exhibit a latent heat storage capacity of more than 176 J/g, which displayed outstanding latent heat storage/release capability and good anti‐permeable property. [ABSTRACT FROM AUTHOR]

A kind of paraffin@graphene/silicone rubber (SR) composite form-stable phase change material (PCM) was prepared in this paper. Paraffin@graphene phase change microcapsules were fabricated by electrostatic self-assembly method, then the microcapsules were added to the SR matrix to prepare paraffin@graphene/SR composites. The microstructure of the composite was characterized by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) and thermal conductivity test results show that the phase change latent heat is 53.39 J g−1 and the thermal conductivity reaches 0.453 W m−1 K−1 for the composite with 30 phr paraffin@graphene microcapsules. The microcapsules enhance the thermal and mechanical properties of SR, which can be used for thermal energy storage. [ABSTRACT FROM AUTHOR]

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]

The storage of latent heat using phase change materials (PCM) is an effective method of energy storage. In this study, silicone rubber (SR)/graphene nanoplates (GNPs)/paraffin@SiO2 phase change microcapsules (Pn@SiO2) shape-stabilized phase change materials (SSPCM) with high thermal conductivity, low leakage rate and tunable thermal management capability are prepared by method of add phase change microcapsules and thermal conductivity enhancer graphene nanoplates. The effects of Pn@SiO2 content on properties of the SR/GNPs/Pn@SiO2 (SGP) composites were investigated by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry. The results show that the enthalpy of phase change composites can be adjusted from 25.6 to 78.56 J·g−1 by changing the addition amount of Pn@SiO2 microcapsules. Moreover, the effect of GNPs on the thermal conductivity of SR matrix is greater than that of Pn@SiO2 on SR, as a consequence, the thermal conductivity of SGP composites decreases with the increase of Pn@SiO2. In addition, the thermal conductivity of SGP phase change composites can also reach 0.567 W·m−1K−1 after the addition of microcapsules, which dramatically shortens the response time of the material in the application. In summary, SGP composites have promising applications in the field of thermal storage. [ABSTRACT FROM AUTHOR]

In this paper, a series of silicone rubber (SR)/thermochromic microcapsules (TC@MF)/cuprous oxide (Cu 2 O) flexible phase change composites (STC) with multi-colors and reversible thermochromic were prepared. In this composite, SR was used as polymer matrix and TC@MF with phase change enthalpy of 193 J/g was used as functional filler. Moreover, different contents of Cu 2 O were introduced to change color of composites and improve thermal conductivity and photothermal conversion. The STC composites could undergo reversible color changes from blue-violet to red with a color change temperature of approximately 52 °C. And it exhibited excellent leakage resistance with the leakage rate of STC-2 as low as 0.41%. The thermal conductivity of the STC-3 composite reached 0.33 W m−1 K−1 at Cu 2 O content of 9 phr. The STC composites were applied to dissipate heat from the battery and the maximum surface temperature was only 49.0 °C at 9.8 A discharge rate which represented 24.03 % reduction in surface temperature compared to the bare battery. This work offers an effective route for preparation of battery thermal regulation materials based on thermochromic microcapsules, which has significant potential for application in the field of battery thermal management. [Display omitted] • Cu 2 O can enhance the thermal conductivity and photothermal conversion of the composites. • TC@MF and Cu 2 O were cleverly utilized to synergistically improve the safety of the thermal management materials. • The composites exhibited excellent reversible thermochromic capacities with blue-violet to red transformation. • The composites showed efficient battery thermal management capacity. [ABSTRACT FROM AUTHOR]

A novel elastic shape-stabilized phase change materials (SSPCMs) were obtained by reducing and vulcanizing a graphene oxide (GO) modified phase change latex (PCL), which is composed of ethylene propylene diene monomer (EPDM) and paraffin. GO as Pickering emulsifier assisted in fabricating EPDM/paraffin PCL. The zeta potential showed that the PCL was stable. Meanwhile, optical microscope and particle size test indicated that the average particle size was 3–5 μm. Scanning electron microscopy (SEM) showed that the SSPCMs were composed of reduced GO (RGO)-coated phase change composite microspheres (PCCMs). The intact RGO coating was beneficial to prevent the leakage of paraffin. According to the leakage rate test, the leakage rate of SSPCMs were decreased. When the GO content was 0.5%, the leakage rate of SSPCMs was 0.3%. The mechanical properties test showed that the tensile strength and elongation at break were up to 2.26 MPa and 1663.53%, respectively. The comprehensive properties of the prepared SSPCM make it have great potential in the field of building temperature control. A novel elastic shape-stabilized phase change materials (SSPCMs) were obtained by reducing and vulcanizing a graphene oxide (GO) modified phase change latex (PCL), which is composed of ethylene propylene diene monomer (EPDM) and paraffin. When the GO content was 0.5%, the leakage rate of SSPCMs was 0.3%. The mechanical properties test showed that the tensile strength and elongation at break were up to 2.26 MPa and 1663.53%, respectively. Image 1 • Through Pickering emulsification method, GO modified EPDM/paraffin phase change latex is studied. • The effect of GO content on leakage rate and mechanical strength of SSPCMs was studied. • GO improves the thermal conductivity and thermal stability of SSPCMs and reduces the leakage rate. [ABSTRACT FROM AUTHOR]

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]

Paraffin, due to its linear chain and saturated hydrocarbons with low thermal conductivity, is difficult to transfer energy effectively. Using amphiphilicity of graphene oxide (GO), Pickering emulsion of paraffin@GO was obtained and then paraffin@graphene microencapsulated phase change materials (MEPCMs) were achieved by chemical reduction through adding hydrazine hydrate. Thermally conductive PCMs with segregated structure were constructed by hot compression of paraffin@graphene microencapsules. Scanning electronic microscopy, differential scanning calorimetry and thermal conductivity test were used to characterize microstructure and thermal properties of MEPCMs. Meanwhile, the effect of graphene on the phase change latent heat and phase transition temperature was investigated. Results indicated that GO did not react with paraffin during the process of chemical reduction and the obtained MEPCMs were regular spheres. These MEPCMs had paraffin content of 99% or even more. Graphene working as shell materials increased the phase change latent heat of paraffin from 227.6 to 232.4 J/g, without affecting the phase transition temperature. The hot-compress molding makes graphene shell form segregated structure with more thermal pathways, further enhancing thermal conductivity. The segregated-structure PCMs with high latent heat and thermal conductivity can be applied in energy storage field. [ABSTRACT FROM AUTHOR]