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The incorporation of carbon materials can effectively enhance the performance of thermoelectric materials. By optimizing the thermoelectric properties of the carbon scaffold, it is possible to further improve the thermoelectric performance of the prepared carbon-based composites. To elevate the thermoelectric performance of the carbon scaffold, this work introduces a novel mesoscopic design strategy, utilizing natural flake graphite to create a three-dimensional ordered porous framework. Highly controllable anisotropic conductivity and thermal conductivity of the porous graphite skeleton were achieved, by combining sizable sodium chlorine templates (37.5–250 μm) with a natural flake graphite matrix (50–150 μm). A porous graphite with high electrical conductivity and low thermal conductivity along the vertical axis was obtained by carefully regulating the parameters. The sample demonstrated exceptional thermoelectric conversion performance, achieving a thermoelectric power factor of 12.2 μW m−1 K−2 and a figure of merit value of 28.3 × 10−4. Furthermore, the thermoelectric property of the samples could be greatly improved by adding a small amount of ferric chloride, with a thermoelectric power factor reaching 41.9 × 10−4 and a thermoelectric figure of merit reaching 81.4 μW m−1 K−2. This work provides an effective scheme for the mesoscopic regulation of porous graphite carbon structures and offers a new strategy for enhancing the performance of thermoelectric generators. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, we focus on important global issue containing both environmental pollution control and energy saving. High density polyethylene (HDPE) is utilized as supporting material to load paraffin, while Al2O3 nano-powder is added into composite behaving as thermal conductivity enhancement to form composite phase change materials (paraffin-Al2O3/HDPE composite PCMs). By the adsorption test and differential scanning calomeritry (DSC) curves, the loading ratio of paraffin in paraffin/HDPE composite is 60%, via taking phase change enthalpy and thermal conductivity into integrated consideration, the adding ratio of Al2O3 is 3% in paraffin-Al2O3/HDPE composite. And CMT4304 universal tester results manifest paraffin-Al2O3/HDPE composites have high compressive strength. For paraffin-Al2O3/HDPE composite with 3 mass% Al2O3, Fourier transformation infrared (FT-IR) result indicates no chemical interaction among raw materials but physical combination. DSC results identify composite PCM happens solid–solid phase transition at 33.3 ºC with enthalpy value of 10.7 J g−1 and melts at 48.8 ºC with enthalpy value of 95.1 J g−1, and thermal cycling measurements demonstrate the form-stable composite PCM with adequate stability after 300 times melting/freezing cycles. Furthermore, the thermal conductivity of paraffin/HDPE composite is enhanced by 119.4% to attain 0.419 Wm−1 K−1 after addition of Al2O3. To sum up, form-stable and tough paraffin-Al2O3/HDPE composite PCMs look promising for application in building field as solar energy utilization materials. [ABSTRACT FROM AUTHOR]

A shape‐stabilized composite phase change material (SS‐CPCM) with paraffin (PA) and biological porous carbon (BPC) was prepared. Freeze‐dried biological‐cellulose include abandoned pomelo peel (APP) and tangerine peel (ATP) were carbonized in vacuum at 800 °C to obtain BPC to be used as a matrix material to prevent PA leakage and enhance thermal conductivity. A vacuum impregnation process was utilized to obtain the SS‐CPCM. Scanning electron microscopy showed that BPC (carbonized APP is subsequently referred to as BPC1 and carbonized ATP as BPC2) has a porous, honeycomb‐like structure, and that the paraffin encapsulated by the pores is evenly distributed. The SS‐CPCM2 (made from ATP) had the highest thermal conductivity (2.10 W/m K), which is 1.89 and 10 times that of the SS‐CPCM1 (made using APP) and pure PA, respectively. Differential scanning calorimetry and thermo‐gravimetric analysis were applied to determine the thermal performance and thermal reliability of the SS‐CPCM. Therefore, the prepared SS‐CPCM has potential in the field of energy storage. [ABSTRACT FROM AUTHOR]

Phase‐change materials (PCMs) have been widely investigated as candidates for thermal energy storage and solar thermal energy conversion. However, low thermal conductivity and poor shape stability during phase transition processes are detrimental to their practical applications. In this study, we designed composite PCMs based on carbon foam (CF) via the vacuum impregnation method to overcome these problems. CF with 3D interconnected microporous structures and good compressive strength was fabricated from phenolic resin (PF) using a combined process of carbonization and sacrificial template techniques. The developer material is considered a promising support material for PCMs. The as‐prepared polyethylene glycol/CF composite (PCC) exhibited a high energy‐storage density with a melting enthalpy of 135.7 J/g, and the thermal conductivity was enhanced by 109.8% compared to that of pure polyethylene glycol. In addition, the PCC showed excellent thermal stability and leakage‐proof performance after 100 heating/cooling cycles and good compressive strength. Because of the simple preparation process and low cost, PCC is a promising material for various thermal energy storage applications, especially in building energy storage systems. [ABSTRACT FROM AUTHOR]

In this study, tetradecanol–palmitic acid/expanded perlite composites containing carbon fiber (TD-PA/EP-CF CPCMs) were prepared by a vacuum impregnation method. Binary eutectic mixtures of PA and TD were utilized as thermal energy storage material in the composites, where EP behaved as supporting material. X-ray diffraction demonstrated that crystal structures of PA, TD, EP, and CF remained unchanged, confirming no chemical interactions among raw materials besides physical combinations. The microstructures indicated that TD-PA was sufficiently absorbed into EP porous structure, forming no leakage even in molten state. Differential scanning calorimetry estimated the melting temperature of TD-PA/EP-CF CPCM to 33.6 °C, with high phase change latent heat (PCLH) of 138.3 kJ kg−1. Also, the freezing temperature was estimated at 29.7 °C, with PCLH of 137.5 kJ kg−1. The thermal cycling measurements showed that PCM composite had adequate stability even after 200 melting/freezing cycles. Moreover, the thermal conductivity enhanced from 0.48 to 1.081 W m−1 K−1 in the presence of CF. Overall, the proposed CPCMs look promising materials for future applications due to their appropriate phase change temperature, elevated PCLH, and better thermal stability. [ABSTRACT FROM AUTHOR]

Phase change materials can be incorporated with building materials to make kinds of composite material, which can be applied in building systems due to their excellent thermal energy storage properties. In this study, a novel form-stable composite PCM CA-LA/Diatomite was prepared using vacuum impregnation method by combining a eutectic mixture of capric-lauric acid (CA-LA) as phase change material (PCM) and diatomite as supporting material. The composite products were characterized by using XRD, FT-IR and SEM analyzing methods. The thermal properties of the composite were measured by Differential Scanning Calorimetry (DSC). The results showed that the composite material melted at 23.61 °C with a latent heat of 87.33 J/g and solidified at 22.50 °C with the latent heat of 86.93 J/g. TGA investigation revealed that the composite had excellent thermal durability above their working temperature ranges. The thermal cycling test showed the composite has a good thermal reliability after 200 thermal cycles. What's more, the expanded graphite was added into the composite in order to increase the heat transfer performance. The results showed that the thermal conductivity of the composite increased gradually by 39.7%, 61.6%, 77.6% and 114.2% for the EG fractions of 3%, 5%, 7%, and 10%, respectively. As a result, the CA-LA/Diatomite/EG composite material of has a potential to be applied in modern buildings and solar energy systems due to its excellent thermal properties, good chemical and thermal reliability and high thermal conductivity. [ABSTRACT FROM AUTHOR]

Shape-stable and high-thermal conductivity composite phase change materials (c-PCMs) composed of polyethylene glycol (PEG) and biological porous carbon (BPC) are investigated. BPC based on potatoes and white radishes are obtained by the carbonization method. The thermal conductivity of the BPC increases with the rising of the carbonization temperature due to the higher graphitization degree. Especially, BPC calcined at 1300 °C for 2 h resulted in the optimum PEG supporting matrix candidate, showing an attractive honeycomb-like microstructure. Calcination above 1300 °C results in the destruction of the shape. BPC/PEG c-PCMs are synthesized via a vacuum impregnation approach. PEG equally distributed in the matrix material with a mass fraction of 85.36% approximately and it could keep its morphological stability after heating at 80 °C for 40 h. Moreover, the highest thermal conductivity is 4.5 W/m K, which is about 10 times higher than the pristine PEG. Furthermore, no chemical interaction is found between the PEG and BPC. The melting and solidifying temperature, and enthalpy not vary upon a 200 thermal cycles test. This confirms the excellent chemical and structure stability for c-PCMs, which are within the most promising materials in the area of building heat preservation by being clean, energy-saving and recycled materials. [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]

In this study, the effect of the introduction of carbon nanotubes (CNTs) as a filler for enhancing the thermal conductivity of paraffin-carbon nanotubes/expanded perlite form-stable composite phase change materials (PA-CNTs/EP FS-CPCMs) was experimentally investigated. Four samples of PA-CNTs/EP FS-CPCMs with different CNT mass fractions were prepared by vacuum impregnation. Scanning electron microscopy was employed to investigate the morphology and microstructure of CNTs, EP, and PA-CNTs/EP FS-CPCMs. Differential scanning calorimetry was employed to examine the thermal properties of PA-CNTs/EP FS-CPCMs, and results indicated that the latent heat and phase-change temperatures of the PA-CNTs/EP FS-CPCMs slightly change with the CNTs mass fractions. The thermal conductivity of PA-CNTs/EP FS-CPCMs5.27 (0.516 W m −1 K −1 ) was 4.82 times that of PA-CNTs/EP FS-CPCMs0. The thermal storage and release properties of PA-CNTs/EP FS-CPCMs were significantly improved as compared with those of PA-CNTs/EP FS-CPCMs0. Results obtained from Fourier transform infrared spectroscopy, thermogravimetric analysis, and thermal cycling tests showed that PA-CNTs/EP FS-CPCMs exhibit good chemical and thermal stabilities. The as-prepared PA-CNTs/EP FS-CPCMs demonstrate considerable potential as thermal energy storage materials. [ABSTRACT FROM AUTHOR]

In this study, polyethylene glycol/expanded perlite composite with carbon layer phase-change materials were prepared. EP was impregnated with a sucrose solution, followed by carbonation in situ by the carbon-bed method, for obtaining EPC composite, thus providing an important method for enhancing the thermal conductivity of composite PCMs. Scanning electron microscopy images showed that the EPC composite with a highly porous structure composed of rough micro-pores could act as a good supporting material for absorbing molten PEG. The results obtained from differential scanning calorimeter analysis indicated that the values for the latent heat and temperature of PEPC composite during melting were 134.93 J/g and 55.19 °C, respectively, while, these values were 129.27 J/g and 46.71 °C during freezing, respectively. The thermal conductivity of PEPC composite was 0.479 W/(mK), which was 2.975 times that of PEP composite. The results obtained from Fourier transform infrared spectroscopy and thermo-gravimetric analysis showed that PEPC composite exhibited good chemical stability and thermal stability, respectively. Furthermore, thermal cycling tests indicated that PEPC composite exhibited good thermal reliability after 200 melting/freezing cycles. In conclusion, PEPC composite with excellent thermal properties, ideal thermal conductivity, good thermal reliability and chemical stability could act as the promising building filler materials for the sustainable development of energy-efficient buildings. [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]

Lauric acid(LA)/expanded vermiculite (EVM) form-stable phase change materials were synthesized via vacuum impregnation method. In the composites, lauric acid was utilized as a thermal energy storage material and the expanded vermiculite behaved as the supporting material. XRD and FT-IR results demonstrate that lauric acid and expanded vermiculite in the composite do not undergo a chemical reaction and only undergo a physical combination. Microstructural analysis indicates that lauric acid is sufficiently absorbed in the expanded vermiculite porous network, while displaying negligible leakage even under the molten state. According to DSC results, the 70 wt.% LA/EVM sample melts at 41.88 °C with a latent heat of 126.8 J/g and solidifies at 39.89 °C with a latent heat of 125.6 J/g. Thermal cycling measurements show that the form-stable composite PCM has adequate stability even after being subjected to 200 melting/freezing cycles. Furthermore, the thermal conductivity of the composite PCM increased by approximately 78% with the addition of 10 wt.% expanded graphite (EG). Thus, the form-stable composite PCM is a suitable option for thermal energy storage for building and solar heating system applications. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) have attracted growing attention in clean energy storage fields. To improve the thermal conductivity of porous mineral-based composite PCMs (c-PCMs), pretreatment via in-situ carbonization is proposed to fill the pore structure with thermally conductive carbon. After vacuum impregnation, high-performance c-PCMs are obtained, comprising carbon-modified expanded perlite (EPC) and polyethylene glycol (PEG). The modified micro-pores optimize the heat transfer characteristic behaviors in c-PCMs and improve the adsorption stability of PEG. Thus, the load capacity of PEG reaches approximately 73.90 wt% in EPC/PEG c-PCMs, providing excellent chemical and structural stability among perlite matrix, carbon modifier and PEG PCMs. The thermal conductivity of the EPC/PEG c-PCMs is 0.521 W/(m·K), which is almost 1.3 times that of the pristine PEG. These performances indicate that the EPC/PEG c-PCMs could be used as an environmentally friendly material for external wall heat-insulation application. • The micro-pores and carbon skeleton were developed in expanded perlite modified by sucrose after a carbonation process. • Low-cost, high thermal conductivity, shape-stable c-PCMs were composed of modified expanded perlite and polyethylene glycol. • The mass fraction of PEG in PEG/EPC c-PCMs was 73.90% approximately. • The as-prepared c-PCMs exhibited excellent thermal energy storage performance. [ABSTRACT FROM AUTHOR]

Currently, electrospinning technology is the most used spinning technology. However, electrospinning exhibits low production rate and safety hazards, which has led to the development of the novel centrifugal spinning technology to extrude phase change fibres from composite solutions. The flexible composite phase change fibres based on Polyethylene glycol (PEG) and Polyvinylpyrrolidone (PVP) were prepared by centrifugal spinning. Moreover, carbon nanotubes acted as thermally conductive fillers to enhance the thermal conductivity of flexible composite phase change fibres. The microstructures of the fibres were observed with a scanning electron microscope (SEM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to determine the thermal properties of the fibres. The results showed that the concentrations of PEG and PVP had different influences on the diameter and smoothness of fibres, and the energy storage effect increased with the increasing PEG content. In summary, flexible composite phase change fibres based on PEG and PVP have very good application prospects for thermal insulation. Morphology and microstructure of centrifugal spinning composite fibres: (a) CNTs 1 wt %, (b) CNTs 3 wt %, (c) CNTs 5 wt % and (d) CNTs wrapped in composite fibres. Image 1 • The composite fibres with energy storage effect was prepared by centrifugal spinning. • PEG is encapsulated in PVP fibres with no leakage. • The thermal conductivity of the composite fibres with CNTs is 1.71 times higher than that of without CNTs. • The preparation process of the composite fibres was cost-effective, environment friendly, chemically stability, and harmless. [ABSTRACT FROM AUTHOR]

• The study focuses on a novel matrix material for loading phase change material. • Anodizing surface treatment is applied to preparing nano-porous TS-AS. • Nano-porous TS-AS can improve thermal conductivity and stability of composite PCM. • TS-AS/1-TD composite behaves excellent sustainability to guarantee long-term service. In this study, an innovative matrix material has been designed and prepared for supporting phase change materials (PCMs) to optimize the thermal property of composite PCM. The abandoned thin-slice aluminum substrate (TS-AS) is etched electrochemically into porous layer with peak-valley structure via anodizing surface treatment, nano-porous Al 2 O 3 film growing on the TS-AS surface is used to encapsulate 1-tetrapropanol (1-TD) to prepare nano-porous TS-AS/1-TD composite PCM. According to thermal properties test results, the melting temperature and phase change latent heat (PCHL) of TS-AS/1-TD composite are 36.9 °C and 97.4 J/g, and its thermal conductivity is enhanced by 560.0% compared to pure 1-TD by introducing porous TS-AS, both these thermal properties show excellent sustainability maintaining only ±1.4% variation even after 400 times melting/freezing thermal cycles, while the composite PCM performs good thermal stability beyond 144.7 °C, which enables them to behave as thermal energy absorbing materials applied to cooling the generated heat from running precision device. Besides, the anodizing mechanism inspires the further optimization of aluminum substrate or other metal substrates by regulating porous layer morphology and thickness. [ABSTRACT FROM AUTHOR]