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An innovative way to enhance the thermal conductivity of composite phase change materials (PCMs) is by carbonizing the carbohydrate-coated mineral substrate to modify its porous structure. Here, we study the effect of introducing different amounts of carbonized starch acting as a filler for enhancing the thermal conductivity of the shape-stabilized composite PCMs (ss-CPCMs) based on polyethylene glycol (PEG) and modified expanded vermiculite (MEV). The experimental exploration of the thermal behavior of composite PCMs has been explored sufficiently in depth. The MEV is shown by SEM images to tightly adhere to the carbon layer and to be composed of a dense micropore structure. Results from DSC indicate that the latent heat of the PEG/MEV ss-CPCMs gradually decreases with the increase of carbon layer mass fraction. Results obtained from FT-IR and TGA show that PEG/MEV ss-CPCMs exhibit good chemical and thermal stabilities. The thermal conductivity of the PEG/MEV ss-CPCMs increases with the carbon layer mass fractions and reaches up to 1.94 times that of PEG/EV ss-CPCMs. The PEG/MEV ss-CPCMs result in a promising material for applications in energy-efficient buildings due to its excellent thermal properties, ideal thermal conductivity and good chemical and thermal stability. [ABSTRACT FROM AUTHOR]

Stearic acid (SA) and modified expanded vermiculite (EV) shape-stabilized composite phase change materials (ss-CPCMs) with enhanced thermal conductivity were prepared. EV was impregnated with a starch solution, and then a composite of EV and carbon (EVC) was obtained by carbonizing starch in-situ in the EV layers. 63.12 wt % of SA was retained in the SA/EVC ss-CPCMs without leakage. Scanning electron microscopy (SEM) images showed that the EVC with highly porous micro-pores acted as a good support matrix for absorbing molten SA. The thermal conductivity of the SA/EVC ss-CPCMs was 0.52 W/(m K), and this was an increase of 52.9% compared with that of the SA/EV ss-CPCMs. The results from Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and thermal cycling tests indicated that the prepared SA/EVC ss-CPCMs are a promising material for energy efficient buildings because of their optimum phase-change temperature, a high enthalpy of phase change, ideal thermal conductivity, and good chemical and thermal stability. [ABSTRACT FROM AUTHOR]

In this study, novel form stable composite phase change materials (FS-CPCMs) from palmitic-lauric acid (PA-LA) eutectic mixture and carbonized abandoned rice (CAR) were prepared via vacuum impregnation. The CAR served as a good supporting material to prevent PA-LA from leaking and enhanced the thermal conductivity of PA-LA. SEM results showed that the CAR has a highly porous structure consisting of rough micro-pores and PA-LA did not leak from the CAR during the solid-liquid phase transition. DSC indicated that the latent heat and temperature of PA-LA/CAR FS-CPCMs during melt were 135.4 J/g and 34.3 °C, respectively, whereas, these values were 124.8 J/g and 28.6 °C during freezing, respectively. The thermal conductivity of PA-LA/CAR FS-CPCMs was 1.83 times that of PA-LA. The heat storage/release rate of the PA-LA/CAR FS-CPCMs is significantly more than that of PA-LA for practical applications. The results obtained from FTIR demonstrated that no new chemical bonds were formed between PA-LA and CAR. TGA and 200-cycle experiments showed that the PA-LA/CAR FS-CPCMs exhibit excellent thermal stability and form-stable performance. The PA-LA/CAR FS-CPCMs thus prepared were safe, environmentally friendly, and cost-effective; hence, they can be used as potential building materials for the applications of thermal energy storage. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Carbonization corn cobs were a perfect carrier matrix to form shape stabilized PCMs. • Carbonization corn cobs exhibit a highly porous structure comprising rough micropores. • Latent heat, stability, and thermal properties of PCMs were excellent. • The thermal conductivity of LA-SA/CNCC was 87.5% greater than that of LA-SA. Abstract In this study, novel form-stable composite phase change materials (FS-CPCMs) were prepared by the incorporation of a eutectic mixture of lauric-stearic acid (LA-SA) into carbonization corn cob (CNCC). CNCC served as a good supporting material that not only prevented the leakage of LA-SA but also enhanced its thermal conductivity. Scanning electron microscopy results demonstrated that CNCC exhibits a highly porous structure comprising rough micropores. The retention of 77.9 wt% of LA-SA in CNCC without leakage was observed. Differential scanning calorimetry results revealed that LA-SA/CNCC FS-CPCMs melt at 35.1 °C with a latent heat of 148.3 J/g and solidify at 29.7 °C with a latent heat of 144.2 J/g. The thermal conductivity of LA-SA/CNCC FS-CPCMs was approximately 87.5% greater than that of LA-SA. Thermogravimetric analysis and 200-cycle experiments indicated that the LA-SA/CNCC FS-CPCMs exhibit excellent thermal stability and form-stable performance. Therefore, the as-prepared LA-SA/CNCC FS-CPCMs demonstrate promise for building energy-efficiency applications. [ABSTRACT FROM AUTHOR]

In this study, novel polyethylene glycol @ Si 3 N 4 nanowires as phase-change materials (PCMs) were developed by using ultrasonic cell disruptor. The results obtained herein indicate that these nanowires can be a potential carrier for preparing PCMs. The results show that PEG is composited in a fluffy nano-network structure of Si 3 N 4 nanowires, which could not be easily leaked from this structure for the solid–liquid phase transition. X-ray diffraction and Fourier transform infrared spectroscopy were employed for investigating the structures of PCMs; the results show that a chemical reaction does not occur between PEG and Si 3 N 4 nanowires. Differential scanning calorimetry analysis results indicated that PCMs exhibit appropriate phase-change temperature and excellent high-phase change enthalpy. From the TGA results, PCMs exhibit perfect thermal stability. The PCMs could perfectly maintain their phase transition after 100 melting–freezing cycles. The thermal conductivity of PCMs-1 was 0.362 W/(mK), which was enhanced by 88.54% in comparison with that to pure PEG. The heat storage or release rate of PCMs is significantly more rapid than that of pure PEG for practical applications. [ABSTRACT FROM AUTHOR]

In this study, novel polyethylene glycol (PEG)/White Carbon Black (WCB) form-stable composite phase changes materials (FS-CPCMs) were prepared by super- ultrasound-assisted, which obviously decreases the reaction time. Test results showed that PEG does not easily leak from the fluffy network structure of WCB during solid-liquid phase transition. Results obtained from XRD and FTIR demonstrated that no new chemical bond is formed between PEG4000 and WCB. Results obtained from DSC and TGA analyses showed that FS-CPCMs exhibit excellent thermal stability and good form-stable performance. The phase change enthalpy of FS-CPCMs reached up to 101.1J/g, and the melting and solidifying times of FS-CPCMs were 34.43% and 30.51% less than that of pure PEG, respectively. The thermal conductivity data showed that WCB acted as the support material is very effective for enhancing the thermal conductivity of the FS-CPCMs. The FS-CPCMs thus prepared were safe, environmentally friendly, and cost-effective; hence, they can be used as potential building materials for the applications of thermal energy storage. [ABSTRACT FROM AUTHOR]