Search

The problem of heat dissipation has become a key to maintain the operation state and extending the service time of electronic components. Developing effective thermal management materials and technologies is of great significance to solve this problem. Previously, passive cooling using phase change materials (PCMs) has been proposed as a thermal management method for electronic devices. In this work, a hybrid thermal management system coupling the heat storage of PCMs and the thermal conduction of high conductivity materials is designed toward thermal management of electronic devices. Specifically, ternary composite gels consisting of eicosane, styrene-ethylene-butylene-styrene (SEBS) and boron nitride (BN) are fabricated by liquid-phase blending and sol–gel transition toward the highly efficient thermal management of electronic devices. The van der Waals force between SEBS and eicosane and the π–π interaction between SEBS and BN enable the excellent form-stability of the ternary composite gels. Taking advantage of the merits of the functional components, the proposed ternary composite gels demonstrate a high thermal energy storage capacity of 157.5 Jg−1 and high thermal conductivity of 1.08 Wm−1 K−1. The ternary composite gels are applied in the thermal management of CPU and chip to reduce their working temperature via the synergistic effect of heat dissipation and heat storage. It is anticipated that the ternary composite gels create a state of the art alternative for the next-generation flexible and multifunctional thermal management devices. [ABSTRACT FROM AUTHOR]

Microencapsulated phase change materials (MEPCMs) have been widely used in many fields as thermal energy storage materials. This study reported a novel MEPCM with the functions of thermal energy storage, photothermal conversion, ultraviolet (UV) shielding, and superhydrophobicity, which was particularly suitable for intelligent textiles. The microcapsules based on an n-eicosane core and a CuO-doped polyurea shell with hierarchical structure were fabricated through a one-step interfacial polymerization. The morphology of the capsules and the hierarchical shell structure were identified through scanning and transmission electron microscopy. Thermal analysis indicated that the microcapsules had a high latent heat of 162.3 J/g and demonstrated a high thermal reliability. These microcapsules achieved a good photothermal conversion capability and can reduce UV radiation by approximately 30%. The water contact angle of the MEPCM was over 148° and showed a good superhydrophobic property. Cotton fabric coated with the prepared MEPCM was investigated. Results showed that it achieved a high phase change enthalpy of 36.8 J/g, an effective thermoregulation capability, and a large contact angle of 141.6°. [ABSTRACT FROM AUTHOR]

A phase-change window is a type of energy-saving window that is filled with phase change material (PCM). It can store solar radiant heat and effectively adjust room temperature. In this study, a type of phase-change gel with relatively high melting enthalpy is prepared with n-octadecane and styrene-b-ethylene-b-styrene (SEBS). This gel exhibits better leakproof characteristic and cycle stability compared with n-octadecane. We fill a double-layer glass with this gel to make a novel phase-change gel window (PCGW). Compared with a normal PCM window (PCMW), the phase-change gel will not leak out of the window during solid-liquid phase transition, and it exhibits an equivalent light transmittance during its melting state. Experimental results show that the PCGW achieves better thermal insulation than the PCMW. It can delay the time to reach peak temperature and lower the peak temperature. The temperature regulation performance of the PCGW is determined by its thickness and solar radiation intensity. When the thickness of the gel increases from 4 mm to 8 mm, the peak temperature of the inner surface of the PCGW is reduced by approximately 5.89% after being exposed to 700 W/m2 solar radiation for 120 min. When solar radiation intensity increases from 600 W/m2 to 800 W/m2, the peak temperature of the inner surface of the PCGW increases by approximately 3.25 °C. The PCGW can effectively regulate indoor temperature and benefit from natural light during daytime. It exhibits high application prospect in green energy buildings. • The gel prevents the PCM inside from flowing during solid-liquid phase transition.. • The phase-change gel exhibits a good stability after 1000 cycles. • The transparency of the gel in molten state is close to that of normal PCM glass. • The PCGW can regulate indoor temperature more effectively than the PCMW. • The thermal insulation of PCGWs depends on their thickness and solar intensity. [ABSTRACT FROM AUTHOR]

Two-dimensional transition-metal carbides/carbonitrides (MXenes) have demonstrated wide application prospect in energy conversion and storage, mostly in the form of electrochemical energy storage. Compared with the conversion between chemical energy and electrical energy, an energy conversion process initiated by solar energy and driven by the physical change of energy materials will be a sustainable and environmentally friendly strategy. Therefore, a high-performance MXene aerogel-based phase change material for solar energy conversion and thermal energy storage is constructed. MXene nanosheets with an extinction coefficient of 25.67 L/(g.cm) at 808 nm demonstrate excellent light absorption performance, which can spontaneously convert the solar energy into thermal energy. The polyethylene glycol (PEG) possessing high affinity with MXene acts the medium for thermal energy storage and release in the process of fusion and solidification. The MXene@PEG aerogels are lightweight, with a density about 30 mg/cm3. The MXene skeleton is introduced as supporting materials to keep the shape of MXene@PEG aerogel stable during the phase change process. The MXene nanosheets improve the thermal stability of PEG, the thermal decomposition temperatures can be increased by 40 °C. The actual fusion and solidification enthalpies of MXene@PEG aerogels can reach 167.72 and 141.51 J/g, respectively. The photothermal storage efficiency of MXene@PEG aerogels reaches a relatively high value of 92.5%. This work provides a new type of scaffold for lightweight and shape-stable photothermal carrier and paves the way for the application of non-graphene 2D materials toward solar energy utilization. Image 1 • A brand new concept of MXene aerogel-based phase change materials for solar energy conversion has been established. • The MXene aerogel-based phase change materials are lightweight and shape-stable. • The photothermal storage efficiency of Mxene@PEG aerogels reaches 92.5%. [ABSTRACT FROM AUTHOR]

The medium temperature phase change material gels (PCMGs) have a thermal storage capacity to meet the body's needs for thermal comfort in cold environments. However, traditional PCMGs are prone to leakage and break in solid-liquid phase change process towards personal thermal management (PTM) application. This study develops an innovative approach that uses covalent and ionic crosslinking to simultaneously maintain the form-stability and self-healing capabilities of sodium acetate trihydrate (SAT) PCMGs. The self-healing performance of SAT PCMGs is contributed to the dynamic interaction of ionic bonds and hydrogen bonds in sodium polyacrylate (PAAS) and calcium alginate (CA). The interaction between SAT and dual network (PAAS and CA) provides form-stability to SAT. To remove SAT's supercooling degree, sodium dihydrogen phosphate dihydrate is chosen as the nucleating agent. The proposed SAT PCMGs demonstrate high shape stability, high self-healing properties, high thermal conductivity (0.58 W m−1 K−1) and high thermal energy storage capacity (170.30 Jg-1). Germanium (Ge) membrane prepared by combining Ge powder with chitosan presents high solar absorption. A device consisting of Ge membrane and SAT PCMG is applied in static and dynamic PTM to produce thermal comfort by solar-thermal conversion, thermal energy storage and thermal energy utilization. With this effort, an advanced substitute for the upcoming solar-thermal PTM devices is created. • Novel phase change material gels confining sodium acetate trihydrate in double cross-linked network are proposed. • Sodium acetate trihydrate gels possess high thermal energy storage capacity of 155.11 Jg−1. • Sodium acetate trihydrate gels present excellent form-stability and high self-healing performance. • Sodium acetate trihydrate gels combined with Ge membrane realize the solar harvesting and personal thermal management. [ABSTRACT FROM AUTHOR]

Phase change cold storage, as an emerging cold chain method of maintaining a low-temperature environment and effectively ensuring the quality of biochemical reagents, is extensively utilized because of its benefits of high energy density, low cost, energy conservation and environmentally friendly mode. However, the low thermal conductivity of working medium affects its cold charging/discharging rate and operating efficiency. Meanwhile, the high leakage characteristic in the phase change process leads to a decrease of cold storage capacity and contamination of items. This work proposes the efficient utilization of cold energy enabled by leakage-free phase change cold storage brine gels with extraordinary high thermal conductivity towards biochemical reagent cold chain. Phase change thermal storage gel is prepared by confining brine in the sodium polyacrylate‑calcium alginate network and porous adsorption of expanded graphite. The prepared materials present leak free characteristics and almost 100% mass retention rate. Expanded graphite addition enables the thermal conductivity increase from 0.542 W m−1 K−1 to an extremely high value of 2.766 W m−1 K−1 (an increase of 510%). The enthalpy value of the cold storage brine gel is as high as 144 Jg−1, stably releasing cold at around −24 °C. By regulating the distribution of cold storage working medium, the minimum temperature difference inside the apparatus can be reduced from 6.7 °C to about 1 °C. Finally, performance-enhancing phase change cold storage materials and apparatus in the cold chain of biological reagents is fruitful, effectively providing a long-lasting and uniform low-temperature environment. • Porous medium adsorption and chemical crosslinking are used to fabricate phase change cold storage brine gels. • The brine gels possess a high thermal conductivity of 2.766Wm-1K-1 and a high latent heat of 144 Jg-1. • A novel method for achieving temperature uniformity in the cold storage equipment is proposed. • The assembled cold storage equipment is successfully applied in the biochemical reagents cold chain to ensure the quality. [ABSTRACT FROM AUTHOR]

• A ternary PCMGs consisting of octadecanol, SEBS and hydroxylated carbon nanotubes are proposed. • PCMGs present excellent flexibility, improved form-stability and high biocompatibility. • PCMGs possess high thermal energy storage capacity, high solar absorbance and high cost-effectiveness. • PCMGs are utilized for thermoelectric power generation and personal thermal management. The utilization of renewable biomass and the conversion of renewable energy are promising strategies for providing clean energy and meeting energy needs. In this work, a ternary phase change material gels (PCMGs) composed of octadecanol (OD), styrene-ethylene-butylene-styrene (SEBS) and hydroxylated carbon nanotubes (HCNTs) are proposed to realize the biomass utilization and solar energy harvesting. As a kind of biomass, OD possesses the characteristics of high phase change latent heat, low cost, renewability, environmental friendliness and biosafety. SEBS provides the crosslinked network to load the OD and introduce the free-standing feature. The HCNTs can realize the highly-efficient solar harvesting through the solar-thermal conversion. The Van der Waals force between SEBS and OD, the π-π interaction between SEBS and HCNTs and the hydrogen bond between OD and HCNTs enable the excellent form-stability. Taking advantages of the synergistic effect of the functional components, the proposed biomass-based PCMGs demonstrate high thermal energy storage capacity of 183.04 Jg−1, high solar absorbance of 95.68%, high cost-effectiveness of 3.92 × 10-5$J−1 and high cell viability of 117.9%. The biomass-based PCMGs are effectively applied in the thermoelectric power generation and personal thermal management. This work creates a state-of-the-art alternative for the next-generation solar-thermal materials devices. [ABSTRACT FROM AUTHOR]

• A method was developed for preparing D-mannitol@silica/graphene oxide nanocapsules. • Graphene oxide incorporation had little effect on latent heat of the nanocapsules. • The thermal stability of the nanocapsules was enhanced. • The thermal reliability index was 96.1% after repeated thermal cycling. • The thermal conductivity was increased to 129% through nanoencapsulation. Sugar alcohols have considerable potential for usage in medium-temperature thermal energy storage applications; however, they suffer from poor thermal reliability and low thermal conductivity. Nanoencapsulation is an effective approach to improve the thermal energy storage performance of the phase-change materials. Until now, nanoencapsulation of sugar alcohols with a high phase-change performance has been rarely reported. The objective of this study is to develop a method for the nanoencapsulation of sugar alcohols with an enhanced phase-change performance. D-mannitol nanocapsules with a silica–graphene oxide composite shell were synthesized and investigated to demonstrate the validity of this novel method. The morphology, size distribution, and core–shell microstructure of the nanocapsules were observed using a scanning electron microscope, particle size and zeta potential analyzer, and transmission electron microscope. In addition, the phase-change performance of the nanocapsules was studied using a differential scanning calorimeter, a thermogravimetric analyzer, and weight loss and appearance investigation. The results demonstrate that the melting and solidifying latent heat of the nanocapsules are 216.7 and 174.4 kJ/kg, respectively. The energy storage efficiency of the nanocapsules was 75.8% and its 96.1% was maintained after repeated thermal cycling. Compared with pure D-mannitol, the thermal conductivity of the nanocapsules was observed to increase by up to 128.6%. The novel nanocapsules exhibited good medium-temperature thermal energy storage prospects. [ABSTRACT FROM AUTHOR]

Sugar alcohols with high latent heat have great potential for medium temperature thermal energy storage. Micro/nano-encapsulation can effectively improve the performance of phase change materials (PCMs), such as avoiding leakage and enhancing thermophysical properties. However, only a few work have been reported on the microencapsulation of sugar alcohol, and the reported methods showed some drawbacks such as requiring strictly controlled reactions or resulting in disability for the capsules to solidify. This paper reports for the first time the synthesis and properties of nanocapsules of a sugar alcohol D-mannitol (DM) by a facile sol-gel method. The nanoencapsulation was confirmed by various characterization using Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD), and transmission electron microscope (TEM). Uniform size distribution of the nanoencapsulated DM (NEDM) in 100–200 nm was observed by scanning electron microscope (SEM). The phase change performance of the NEDMs were investigated by differential scanning calorimeter (DSC). The results show that the NEDMs with a melting temperature of 166.2 °C, a melting enthalpy of 220.3 J/g, and an encapsulation ratio of 76.5% were obtained. The thermal reliability of the NEDMs was demonstrated by thermal cycling experiments. The thermal stability of the NEDMs was enhanced compared to DM as investigated by thermogravimetric analyzer (TGA). The NEDMs exhibited great potential for applications in medium temperature thermal energy storage and transfer. • A facile method for nanoencapsulation of D-mannitol was developed. • Nanocapsules with uniform size distribution in 100–200 nm were obtained. • Melting enthalpy of the nanocapsules was up to 220.3 kJ/kg. • The nanocapsules exhibited improved phase change performance and thermal stability. [ABSTRACT FROM AUTHOR]

• Sandwich structured thermal energy storage material constructed by encapsulating inorganic PCM gel in organic PCM gel is proposed. • The thermal energy storage gel makes full use of the advantages of inorganic PCM, organic PCM and gel materials. • The thermal energy storage gel possesses superior thermophysical properties and wearability. • The thermal energy storage gel is applied in wearable PTM to generate thermal comfort for human body. It is still a big challenge to develop state-of-art thermal energy storage materials based on phase-change materials (PCMs) with superior thermophysical properties and wearability for efficient advanced personal thermal management (PTM). A novel strategy for synthesizing thermal energy storage gel with sandwich structure by confining the inorganic PCM gel in the organic PCM gel was proposed to maximize the advantages of inorganic PCMs, organic PCMs and gel materials. Octadecane and sodium sulfate decahydrate were selected as the organic PCM and inorganic PCM, respectively to satisfy the requirements of the working temperature of PTM. The thermal energy storage gels with sandwich structure demonstrate superior thermophysical properties, such as the absence of supercooling (0 °C), high latent heat (158.65 J g−1), high form-stability (no leakage), high cyclic stability (200 cycles) and high economic benefits (4.85 × 10−3 ¥ J−1). Besides, they also have excellent wearability, such as high flexibility, self-healing feature and high biocompatibility. Due to the synergistic enhancement effect and various merits, the novel thermal energy storage gels are successfully utilized in the wearable PTM for human body thermal comfort. The inorganic–organic combination methodology is promising for the highly efficient applications of PCMs in the next-generation PTM. [ABSTRACT FROM AUTHOR]

Sodium acetate trihydrate (SAT) with a working temperature of about 58 °C is a significant working medium in thermal energy storage and solar energy utilization. However, supercooling effect inevitably hinders its heat release in practical applications. Typically, nucleating agents can effectively eliminate the supercooling of SAT. A concomitant problem is that the nucleating agent addition reduces the thermal energy storage capacity. In this work, a state-of-the-art methodology is constructed to eliminate the supercooling and preserve the thermal energy storage capacity of SAT synchronously by utilizing the sodium dihydrogen phosphate dihydrate (SDPD) as a novel nucleating agent. The supercooling of SAT can be reduced from 34.8 °C to 0 °C when increasing the SDPD content from 0% to 1.2%. The corresponding latent heat is slightly increased from 227.30 Jg-1 to 248.77 Jg-1. Thermal conductivity is maintained at a relatively high level of 0.6 Wm−1K−1. Polypyrrole (PPY) with strong solar absorption is assembled with the SAT/SDPD composites to realize the solar energy harvesting. Taking the advantages of the functional components, the proposed SAT/SDPD/PPY device is applied in personal thermal management and the thermoelectric power generation to produce thermal comfort and clean electric energy by the solar-thermal conversion, thermal energy storage and thermal energy utilization. This work provides a new strategy for manufacturing advanced inorganic PCMs and paves the way for the application of inorganic PCMs toward solar energy utilization. [Display omitted] • SAT/SDPD composite is proposed for thermal energy storage and solar energy utilization. • SDPD can eliminate the supercooling and retain the latent heat of SAT. • The supercooling, latent heat and thermal conductivity reach 0 °C, 248.77 Jg-1 and 0.6 Wm−1K−1. • SAT/SDPD composite is assembled with polypyrrole to realize solar harvesting. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel concept of self-healing IHSG with energy storage capacity is proposed. • The dynamic hydrogen bond and dynamic ionic bond enable the self-healing feature. • The IHSGs are applied in the wearable personal thermal management. Thermal comfort is of great significance to maintain the normal metabolism of life. Personal thermal management (PTM) that passively regulates the immediate environment around the human body is a promising alternative. In this work, we report a state-of-the-art concept of self-healing inorganic hydrated salt gels (IHSGs) constructed by ionic crosslinking, covalent crosslinking and hydrogen bond crosslinking for wearable PTM. Sodium sulfate decahydrate (SSD) is selected as the energy storage medium on account of its phase change temperature near the human body temperature. The calcium alginate and the sodium polyacrylate construct the double gel network to anchor the SSD. The dynamic hydrogen bond and the dynamic ionic bond enable the self-healing feature of the SSD IHSGs. The proposed SSD IHSGs with 4% borax, 0.1% sodium hexametaphosphate and 8% sodium polyacrylate demonstrate suppressed phase separation, eliminated supercooling, highly form-stability, high instinct thermal conductivity (0.80 Wm-1K−1), high energy storage capacity (147.14 Jg−1), high self-healing rate (94.3%) and highly cost-effectiveness (energy storage cost 2.44 × 10-3 ¥J−1). Taking advantages of the above merits, the IHSGs are applied in wearable PTM in the static and dynamic modes to meet the thermal comfort requirements. It is anticipated that the one-stop IHSG solution offers great prospect for the advanced wearable PTM. [ABSTRACT FROM AUTHOR]

Novel light-driven and electro-driven polyethylene glycol (PEG)/two-dimensional MXene composite (PEG@MXene) with enhanced thermal conductivity and electrical conductivity as form-stable phase change material (FSPCM) is first obtained via the simple vacuum impregnation by employing MXene as the supporting skeleton as well as thermally conductive and electrically conductive filler and PEG as the phase change working substance. Fourier transform infrared spectroscopy (FT-IR) indicates that no chemical reaction occurred between PEG and MXene during adsorption process, but X-ray diffraction (XRD) results show the crystalline regions of PEG was decreased by the incorporation of MXene. The differential scanning calorimetry (DSC), polarizing microscope (POM), as well as XRD results demonstrate that the MXene nanosheets act as heterogeneous crystal nuclei and promote the crystallization of PEG. The melting and freezing latent heats of PEG@MXene are as high as 131.2 and 129.5 J/g, respectively, the relative enthalpy efficiency is 80.3%, and the thermal conductivity and electrical conductivity are 2.052 W/mK and 10.41 S/m, respectively. The obtained PEG@MXene has excellent light-to-thermal conversion, electro-to-thermal conversion and thermal energy storage performance. All these results demonstrate that the obtained PEG@MXene will have a great potential application for thermal energy storage. Image 1 • A novel light-driven and electro-driven PEG@MXene FSPCM is first obtained. • The thermal conductivity and electrical conductivity of PEG@MXene are significantly improved. • The obtained PEG@MXene will have a great potential application for thermal energy storage. [ABSTRACT FROM AUTHOR]