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    Development of pentadecane/diatomite and pentadecane/sepiolite nanocomposites fabricated by different compounding methods for thermal energy storage
    (John Wiley and Sons Ltd, 2019) Konuklu Y.; Ersoy O.; Erzin F.
    Global warming is one of the most important consequences of excess energy consumption. Phase change materials (PCMs) have prominent advantages in thermal energy storage owing to their high latent heat capacities and small temperature variations during the phase change process. However, leakage is a major problem that limits the use of PCMs. Leakage may occur in encapsulated PCMs or in composites where the PCM is attached to the surface of a supporting material or within the pores of that material. In this study, pentadecane/diatomite and pentadecane/sepiolite nanocomposites were fabricated by using unmodified and microwave-irradiated diatomite and sepiolite samples and by using different compounding processes, such as direct impregnation, vacuum impregnation, and ultrasonic-assisted impregnation methods. The microstructures and the chemical and thermal properties of the composites were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and differential scanning calorimetry. Subsequently, the thermal reliability and stability and the thermal conductivity of the PCM composites were also investigated. A melting temperature of 9.25°C and a latent heat capacity of 58.73 J/g were determined for the pentadecane/diatomite composite that was prepared with the direct impregnation method using a microwave-treated diatomite sample. The pentadecane/sepiolite composite prepared in the melting temperature range 7.98°C to 8.53°C and latent heat capacity range 41.05 to 46.02 J/g. The results of the thermal analysis indicate that fabricated diatomite-based or sepiolite-based PCM composites have good potential as thermal energy storage materials. © 2019 John Wiley & Sons, Ltd.
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    Experimental study on preparation of lauric acid/microwave-modified diatomite phase change material composites
    (Elsevier B.V., 2019) Konuklu Y.; Ersoy O.; Erzin F.; Toraman Y.Ö.
    The main aim of this study is to prepare and characterize PCM/diatomite composites with impregnation method using unmodified and microwave modified diatomite. The effect of microwave modification of diatomite on composites was investigated. In this study, lauric acid (LA) was used as the phase change material and the prepared PCM/diatomite composites were analysed by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and laser diffraction particle size analyser. Thermal stability of composites was demonstrated by thermal resistance test. The results show that the composites prepared with microwave-modified diatomite have higher heat capacities than those prepared with unmodified diatomite. According to the DSC analysis, composites with modified diatomite have melting and freezing temperatures of 40.4 and 39.5 °C, respectively. These composites also have the latent heats of melting and freezing of 55.7 and -49.9 J/g, respectively. According to the analysis and thermal resistance test, it was seen that composites were prepared successfully. After the determination of better thermal energy storage properties of microwave-modified diatomite containing composites than unmodified diatomite containing composites, we recommend that these composites can be used for thermal energy storage applications. © 2019 Elsevier B.V.
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    Preparation of pentadecane/poly(melamine-urea-formaldehyde) microcapsules for thermal energy storage applications
    (John Wiley and Sons Ltd, 2019) Konuklu Y.; Erzin F.
    Phase change materials (PCMs) with suitable melting ranges for thermal energy storage applications are alkanes, paraffins, fatty acids, eutectic mixtures, and inorganic PCMs. Paraffinic hydrocarbons and fatty acids with low solubility in water are usually the preferred candidates. Pentadecane, which is an alkane hydrocarbon with the chemical formula C15H32, was used as PCM in this study. The pentadecane was microencapsulated with a poly(melamine-urea-formaldehyde (MUF)) shell for thermal energy storage. Pentadecane/poly(MUF) microcapsules were prepared by in situ polymerization method. The morphological analysis of pentadecane microcapsules was analyzed with scanning electron microscopy (SEM). Thermal properties of microcapsulated pentadecane were determined by differential scanning calorimetry (DSC). The results demonstrated that pentadecane/PUF microcapsules were prepared successfully, and they offer proper phase transition temperature range (8.7°C and 8.1°C) and heat enthalpy values (84.5 and -88.2 kJ/kg) for thermal energy storage applications. According to the results, it was determined that pentadecane/poly(MUF) microcapsules have good potential for thermal energy storage applications. © 2019 John Wiley & Sons, Ltd.