Composite Phase Change Research Articles

Thermal and Mechanical Robust Solid‐Solid Phase Change Materials Enabled by Reactive Crosslinkable Poly(Ethylene Glycol)s via Facile Thiol‐Ene Photo‐Click Chemistry

AbstractSolid–solid phase change materials (SSPCMs) are among the most promising candidates for thermal energy storage and management. Excellent shape stability, high heat storage capacity, and satisfying mechanical properties are essential for the practical applications of SSPCMs, yet giving PCMs these characteristics at the same time remains an unmet challenge. Herein, the synthesis of PEG‐PVEG copolymers is reported with various vinyl content using a synergistic catalysis strategy, leading to novel cross‐linked PEG‐based SSPCMs via a thiol‐ene photo‐crosslinking reaction. These PCMs exhibit excellent shape stability and remarkable energy storage capabilities with latent heat up to 128.3 J g−1. The materials exhibit exceptional thermal stability and retain their energy storage capacity after 500 heating‐cooling cycles. Notably, the materials show superior mechanical strength and excellent toughness. Furthermore, the latent heat enthalpy can be further improved to 146.8 J g−1 without erosion of shape stability by the encapsulation of PEG into present SSPCM. The enhancement of both thermal and electrical conductivities is also demonstrated by the phase change composites (PCCs) incorporating multi‐walled carbon nanotubes (MWCNTs). Overall, this study presents a convenient and feasible strategy for developing SSPCMs with excellent shape stability, high latent heat and satisfying mechanical properties for thermal management.

3D printing, leakage-proof, and flexible phase change composites for thermal management application

Phase change composites (PCCs) have attracted much attention in the fields of thermal management due to their high latent heat. However, their risk of leakage and poor shape designability greatly limit their industrial applications. Therefore, there is an urgent need to develop leakage-proof and customizable PCCs to meet the emerging requirements of thermal management applications. Some scholars have proposed the concept of preparing PCCs by 3D printing technology, aiming to meet customized thermal management requirements of various electronic devices. Nevertheless, the phase change material leaking of PCCs under high temperature is still a tough problem to solve. In this study, expanded graphite (EG) is used as the carrier for paraffin wax (PW), which names as EP can tightly enveloping PW in its porous structure. Then, an innovative carbomer gel ink is prepared for 3D printing using EP and short carbon fiber (SCF) as thermal conductive fillers. Freeze-drying and polydimethylsiloxane (PDMS) infiltrating procedures are furtherly performed to ensure the flexibility of final PCCs samples. A maximum thermal conductivity of 2.89 W/(m·K) is obtained when the content of SCF/EP filler is 10 wt%. Importantly, the flexible PCCs prepared through this method effectively prevent the PW leaking during thermal management applications, thereby avoiding the consequent safety risks and enhancing the lifespan of electronic devices. This work opens up a promising pathway for the rapid fabrication of leakage-proof, customizable and flexible PCCs.

Active and passive infrared emittance tuning using optically transparent unpatterned ITO thin films

Tailoring of thermal emittance has applications in smart radiators, camouflage, infrared (IR) scene generation, stealth, and thermal management. Various studies have explored avenues to achieve both passive and active emittance tuning using methods such as meta-surfaces, phase change materials, composites, nanostructure arrays and multi-layer stacks. Most of these methods often involve complex fabrication processes like multilayer depositions and micro/nano patterning, limiting their scalability for large-scale applications. This study presents a straightforward and scalable approach for passive and active emittance tuning using Indium Tin Oxide (ITO) films deposited on a high emissivity flexible polyethylene terephthalate (PET) substrate. By changing the deposition time, the thickness of the ITO film is controlled which changes the observed emissivity of the ITO/PET composite structure over a wide range (0.2–0.94) while maintaining optical transparency. Using this approach for passive emittance tuning, we demonstrate an IR scene generation application. As the ITO film is conducting, by applying voltage to the ITO/PET sheet, its temperature is changed using which active emittance tuning is also achieved. Compared to existing methods of emittance tuning, the presented approach is simpler, gives flexible films with optical transparency, and has the potential for large-scale integration, enabling cost-effective and scalable manufacturing of emittance-tuned surfaces.

Polystyrene shell-based “coconut-like” and “pomegranate-like” microencapsulated phase change materials: Formation mechanism, thermal conductivity/stability enhancement and their application in thermal management

Encapsulation of phase change materials (PCMs) using polystyrene (PS) can be an effective solution to the leakage of PCMs, but the low thermal conductivity/stability of the prepared microencapsulated phase change materials (MEPCMs) remain unresolved. Here, we investigated the formation mechanism of PS shell-based MEPCMs via Pickering emulsion polymerization: coconut-like and pomegranate-like MEPCMs were obtained for the first time before and after the introduction of divinylbenzene (DVB), and the thermal conductivity and stability of the former were lower than that of the latter with the same graphene nanosheets (GNSs). Among them, MEPCM-4–7 wt% GNSs (St:DVB=1:1) has the highest thermal conductivity of 0.9358 W∙m−1∙k−1 (222.47 % higher than MEPCM without GNSs) and optimal anti-leakage performance. The thermal stability (thermogravimetric results) is slightly weaker than MEPCM-3–7 wt% GNSs (St:DVB=5:1), but has the highest thermal reliability (the melting enthalpy only decreases by 0.19 % after 100 cycles). The phase change composites (PCCs) was prepared by dispersing MEPCMs in PDMS matrix and applied to the simulated chip thermal management, which can achieve a 10.85 % decrease in the chip equilibrium temperature compared with PDMS. The method of improving the heat transfer properties and thermal stability of MEPCMs based on their structure provides a new idea to solve the problem of low thermal conductivity and stability of MEPCMs, and the prepared PCCs show great potential for practical applications in the field of thermal management.

Dual-Mode MXene-Based Phase-Change Composite Towards Enhanced Photothermal Utilization and Excellent Infrared Stealth.

Solar thermal collectors based on phase change materials (PCMs) are important to promote the civilian use of sustainable energy. However, simultaneously achieving high photothermal efficiency and rapid heat transfer of the PCM carrier typically involves a high proportion of functional materials, contradicting a satisfying energy storage density. In this work, a surface-engineered anisotropic MXene-based aerogel (LMXA) integrated with myristic acid (MA) to produce phase change composites (LMXA-MA) is reported, in which the laser-treated surface composed of the hierarchically-structured TiO2/carbon composites act as a light absorber to improve solar absorption (96.0%), while the vertical through-hole structure allows for fast thermal energy transportation from surface to the whole. As a result, LMXA-MA exhibits outstanding thermal energy storage (192.4 J·g-1) and high photothermal conversion efficiency (93.5%). Meanwhile, benefiting from the intrinsic low emissivity of MXene material, thermal radiation loss can be effectively suppressed by simply flipping LMXA-MA, enabling a long-term temperature control ability (605 s·g-1). The excellent heat storage property and switchable dual-mode also endow it with an infrared stealth function, which maintains camouflage for more than 240 s. This work provides a prospective solution for optimizing photothermal conversion efficiency and long-term thermal energy preservation from surface engineering and structural design.

Evaluation of the energy flow characteristics and efficiency of photothermal functional phase change materials for efficient solar thermal harvesting

Photothermal functional phase change materials (PCMs) have attracted considerable attention due to their large energy density, which can solve the inherent imbalance defects of solar energy. However, the efficiency determination of the PCM-based photothermal utilization process (including photon absorption, photothermal conversion, thermal storage, and thermal release) is still unclear, especially with different or even contradictory quantitative indexes for the same process, resulting in inaccurate photothermal utilization performance and unfair comparison in various efforts. Herein, we clarified the photothermal utilization sub-processes of phase change composites via optical characterizations and photothermal conversion experiments and highlighted the energy dissipation mechanism of photothermal conversion process by fluorescence and femtosecond transient absorption examination. Besides, the energy flow features of these sub-processes were explored by determining the energy flow and optical/thermal losses. More importantly, we standardized the efficiency of the four sub-processes by proposing evaluation indexes and established the relationship among the four sub-processes to derive the total photothermal utilization efficiency. This work provides a paradigm for a comprehensive investigation of PCM-based photothermal utilization systems, especially establishing consistent criteria for subsequent efficiency determination, laying a solid foundation for developing and quantifying solar thermal utilization systems.

Flexible loofah sponge-based phase change composite for thermal protection and wearable thermal management

To address the escalating demand for sophisticated thermal management in electronics, energy batteries, and wearable devices, extensive research has been dedicated to developing shape-stabilized and highly thermally conductive phase change composites (PCCs). However, their inherent rigidity and limited flexibility pose significant challenges for practical applications. In response, we have engineered a novel and flexible PCC by integrating loofah sponge (LS) and styrene-isoprene-styrene block copolymer (SIS) as co-supporting framework with paraffin wax (PW) as heat storage medium, further enhanced with carbon nanotubes (CNTs). The process began with the vacuum adsorption of PW into an ammonia-softened LS, which forming a fibrous network. This was followed by the introduction of a mixed melt of SIS and PW, physically cross-linked and dispersed with CNTs, into the LS fibrous network. The composite was then cooled and shaped to produce the (final) PCC. The resultant PCC exhibited remarkable ductility with an elongation of approximately 780 % and a maximum tensile strength of ∼2 MPa. Furthermore, it maintained thermal reliability and dimensional stability over long-term usage, with a melting heat enthalpy as high as 146.4 J/g. This flexible PCC, which combines high latent thermal energy storage, temperature regulation, and thermally induced assembly properties, shows considerable promise for thermal protection and portable thermal management in electronic devices.

Ti3C2Tx MXene/Graphene hybrid frameworks for constructing thermally conductive phase change composites with solar-thermal conversion ability

Application of three-dimensional (3D) carbon framework in phase change material (PCM) has aroused a tremendous interest. However, implementing a high alignment carbon framework with low interfacial thermal resistance (ITR) remain challenging. Herein, we demonstrated a synergetic effect strategy by Ti3C2Tx MXene and graphene nanoplate (GNP) to achieve a 3D thermally conductive framework with high alignment skeleton and low filler-to-filler ITR. Typically, the 3D anisotropic carbon framework is fabricated by unidirectional ice template freezing cellulose nanofibers (CNF)/GNP solution with the assistance of MXene. The abundant functional groups of MXene and the similar layered structure promote the dispersion stability of GNP in CNF aqueous solution, resulting in the significant improvement in GNP alignment and the filler-to-filler ITR. Therefore, the final phase change composites obtained by impregnating polyethylene glycol (PEG) into the framework achieves a satisfactory thermal conductivity (TC) of up to 3.49 W/m K at only 6.25 vol% filler loading. Combining the solar-thermal conversion ability of graphene and MXene, the PCM reveals a rapid energy conversion, transfer and storage capability. More importantly, the phase change enthalpy of the PCM can be as high as 164.3 J/g, with little change even after 50 heating-cooling cycles, and the existence of carbon framework can effectively prevent the leakage phenomenon in solid-liquid conversion process, ensuring its shape stability.

Preparation and performance studies on organic-inorganic phase change composites based on zeolitic imidazolate and paraffin for reducing gun barrel erosion

With the increasing requirements of tank guns for higher muzzle velocity and faster firing rate, some high energetic additives, such as cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HMX), have been widely used in high energy gun propellants. Consequently, the gun barrel erosion induced by the burning of high energy gun propellants has been an important issue that affects the lifespan of gun barrels. In order to address this problem, erosion reducing additives, including TiO2, paraffin, polyurethane or a combination of these, were introduced into the gun propellant or propellant charge system to alleviate the gun barrel erosion. In this study, a novel organic-inorganic phase change composite paraffin/ZIF-67 with solid paraffin (SP) as the phase change component and zeolitic imidazolate framework-67 (ZIF-67) as the matrix was designed and prepared as anti-erosion additives. The designed composite has a high thermal storage capacity of 93.88 J/g when the ZIF-67 content is 5 wt%. The erosion reducing effect of paraffin/ZIF-67 was determined by erosion tube test. The results show that the introduction of paraffin/ZIF-67 can improve the erosion-reducing efficiency of gun propellants. Compared with the control sample, the erosion-reducing efficiency of paraffin/ZIF-67 exhibited a faster increase with the increase of their contents, having the maximum erosion-reducing efficiency of 39.2 % when the addition of paraffin/ZIF-67 is 3.2 wt%. The incorporation of paraffin/ZIF-67 in the composites has a cooperative effect of each component on reducing gun barrel erosion. The developed organic-inorganic phase change composites exhibit great potential in the application of reducing gun barrel erosion, providing a new way for the development of erosion reducing additives.

Phase-Change Stamp with Highly Switchable Adhesion and Stiffness for Damage-Free Multiscale Transfer Printing.

Transfer printing is a technology widely used in the production of flexible electronics and vertically stacked devices, which involves the transfer of predefined electronic components from a rigid donor substrate to a receiver substrate with a stamp, potentially avoiding the limitations associated with lithographic processes. However, the stamps typically used in transfer printing have several limitations related to unwanted organic solvents, substantial loading, film damage, and inadequate adhesion switching ratios. This study introduces a thermally responsive phase-change stamp for efficient and damage-free transfer printing inspired by the adhesion properties observed during water freezing and ice melting. The stamp employs phase-change composites and simple fabrication protocols, providing robust initial adhesion strength and switchability. The underlying mechanism of switchable adhesion is investigated through experimental and numerical studies. Notably, the stamp eliminates the need for extra preload by spontaneously interlocking with the ink through in situ melting and crystallization. This minimizes ink damage and wrinkle formation during pickup while maintaining strong initial adhesion. During printing, the stamp exhibits a sufficiently weak adhesion state for reliable and consistent release, enabling multiscale, conformal, and damage-free transfer printing, ranging from nano- to wafer-scale. The fabrication of nanoscale short-channel transistors, epidermal electrodes, and human-machine interfaces highlights the potential of this technique in various emerging applications of nanoelectronics, nano optoelectronics, and soft bioelectronics.

Anisotropic and shape-stable sugarcane-based phase change composites in the application of solar thermal energy storage

The study of anisotropically thermal conductive phase change composites (PCCs) with shape-stability is of great importance to improve the intermittent issues in solar thermal utilization, while some drawbacks like the high cost, low thermal conductivity, and poor durability of current PCCs restrains their practical applications. Herein, a cheap and scalable biomass-based PCC containing carbonized sugarcane (CSC), polyethylene glycol (PEG), and graphene (GF) is proposed. The abundant vessels inside CSC result in a high PEG loading rate of 82.48 %. The naturally occurring anisotropic structure inside CSC can drive GF to be oriented along the lengthwise direction, which gives PCC a high thermal conductivity anisotropy degree of 1.45. The prominent anisotropy improves the lengthwise thermal diffusion and restrains the transverse heat leakage to the environment. Besides, the loaded GF can further enhance the light absorption of PCC to 98 %. As a result, the prepared PCC can achieve high solar-thermal energy storage efficiencies of 79.3–91.7 % with variable solar intensity from 1 to 2 suns. Meanwhile, good anti-leakage and durability performances promote the practical utilization of PCCs. The present work paves a promising road for manufacturing biomass-based anisotropic PCCs in efficient solar thermal energy storage.

Enhancing the safety and thermal stability of polyurethane filling materials in the mining industry through expanded graphite-based hydrated salts

The utilization of Polyurethane foaming materials (PUF) to seal coal fissures presents a significant challenge due to the substantial heat generated during the reaction process, potentially accelerating fires. In order to study this issue, we propose a novel low-heat polymerization mechanism by incorporating a hydrated salt phase change composite that efficiently absorbs polymerization heat while encapsulating liquid water using expanded graphite (EG). Our findings demonstrate that integrating 10 % EG-6 leak-free phase change material effectively reduces the reaction temperature to a safer 91.4 °C, ensuring minimal impact on the inherent properties of the material. Thorough analyses via TGA and in-situ IR experiments reveal a noteworthy 17 °C elevation in the modified PUF's thermodynamic characteristic temperature point. Additionally, we developed a mixed combustion model of PUF and coal to investigate the gas generation pattern of polyurethane in the mine-filled state where fire occurs. Specifically, the introduction of PUF reduced O2 consumption and CO production while increasing CO2 and C2H4 production, which is consistent with the reality of increased carbon hydrocarbon gases being monitored downhole. These findings suggest a synergistic, mutually beneficial relationship between the two during the low-temperature oxidation stage. This research offers perspectives for the development of polymer materials for coal mines and the safe application of actual filling.

Cellulose-reinforced foam-based phase change composites for multi-source driven energy storage and EMI shielding

To address the increasingly serious environmental pollution and energy crisis, there is an urgent need to develop multi-source-driven energy storage materials, the field of new energy sources, such as solar thermal power generation, but electromagnetic pollution has become a primary problem that needs urgent resolution. Therefore, the development of multifunctional phase change composites (CPCMs) with multi-source drive capabilities and excellent electromagnetic shielding integration is crucial. In this study, polypyrrole (PPy)-coated conductive fibers were crosslinked with polyvinyl alcohol (PVA) to form a three-dimensional network, which was then combined with metal foam to prepare Ni–F/PPy@CNF-PVA (PCN) dual-network carriers with high electrical conductivity by vacuum-assisted adsorption and freeze-drying methods. Polyethylene glycol (PEG) was subsequently encapsulated via vacuum impregnation to get the shape-stable PEG/Ni–F/PPy@CNF-PVA (PPCN) phase change composites. The PPCN exhibited good stability and high energy storage density (melt enthalpy up to 126.18 J/g, relative enthalpy efficiency over 99 %). Benefiting from its outstanding electrical conductivity (186680 S/m for PPCN-3), light-absorbing properties, and magnetism, the PPCN also exhibits highly efficient photothermal, electrothermal, and magnetothermal conversion capabilities. The electromagnetic interference shielding efficiency reaches up to 110.37 dB within the X-band frequency range (8.2–12.4 GHz). In conclusion, PPCNs are significant for multi-source-driven energy storage and electromagnetic shielding.

Microscopic molecular insights of different carbon chain fatty acids on shape-stabilized phase change composite

Microscopic molecular insights of different carbon chain fatty acids on shape-stabilized phase change composite

Superelastic Polymer Aerogel with Superamphiphilicity.

Elastic aerogels have become a research hot spot in both academia and industry recently. The reported elastic aerogels are all made of hard materials by controlling their shapes. Herein we report an elastic aerogel made of a polymer elastomer with entropy elasticity. In the aerogel, cross-linked carboxyl nitrile rubber nanoparticles with hydrophilicity are dispersed in hydrophobic derivative of styrene-maleic anhydride alternating copolymer, forming a very special micro-nano surface structure with hydrophilic protrusions and hydrophobic depressions on the aerogel wall; therefore, the aerogel is not only superelastic but also superamphiphilic. A leak-free phase-change composite was prepared using the aerogel and paraffin, which can maintain at phase change temperature of paraffin for a longer time than the traditional one. The aerogel is also extremely suitable for desalination evaporators in solar-driven interfacial evaporation technology due to its superamphiphilicity, superelasticity, and ability to absorb sunlight. Exceptional evaporation rate of 2.78 kg·m-2·h-1 and evaporation efficiency of 170% could be reached even without using expensive light-absorbing materials. The evaporation rate exceeds that of most evaporators with expensive light-absorbing materials, and the evaporation efficiency exceeds the theoretical limit of conventional 2D solar evaporators. Both the phase-change composite and the evaporator can be easily recovered because the novel superelastic aerogel reported in this work is also recyclable.

Expression of Concern for article entitled “Melamine foam-based shape-stable phase change composites enhanced by aluminum nitride for thermal management of lithium-ion batteries”

Expression of Concern for article entitled “Melamine foam-based shape-stable phase change composites enhanced by aluminum nitride for thermal management of lithium-ion batteries”

Municipal sludge-based low-carbon phase-change composite towards energy storage: Fabrication and investigation

The integration of municipal sludge with phase change materials for composite energy storage material fabrication benefits to sludge significant reduction and recycling, heavy metal fixation, and minimizing environmental pollution. This groundbreaking work proposed municipal sludge-derived phase-change composites utilizing potassium nitrate as phase change material to produce cost-effective, low-carbon thermal energy storage materials. Five samples with varying mass fractions of municipal sludge incineration ash and potassium nitrate were prepared through a cold-compression & hot-sintering process and then thermal properties, microscopic structure, mechanical strength, and chemical compatibility between components was investigated extensively to explore the feasibility of municipal sludge recycling for composite energy storage material fabrication. The results revealed successful encapsulation of heavy metals within the phase change composites, and the composite with a 50:50 ratio of ash to potassium nitrate exhibited superior overall performance, which boasts a thermal energy storage capacity of 330.34 J/g with temperature rising from 100 up to 380 °C, a peak thermal conductivity of 1.04 W/(m·K), remarkable mechanical strength of 153.78 MPa, and excellent thermal stability. In addition, the components of the municipal sludge incineration ash and potassium nitrate displayed exceptional chemical compatibility. This novel phase change composite holds significant potential for engineering application compared to traditional alternatives.

Carbon-based phase change composites with directional high thermal conductivity for interface thermal management

Phase change materials (PCMs) can provide a buffer platform for thermal management systems to deal with thermal runaway problems. However, prompt heat dissipation and cost-effective thermal regulation in desired devices are still limited by insufficient thermal transport behavior and liquid leakage of PCMs. Here, we report a facile strategy to develop high-power-density device by carbon-based phase change composites (PCCs) with directional high thermal conductivity. The synergistic effect of self-assembled aligned graphite nanoplatelets (GNPs) inside the resultant PCCs on thermal transport and structural reinforcement enable the PCCs to show high thermal conductivity (in-plane KPCCs of up to 32.86 W m−1 K−1), large heat storage density (158.2–248.3 J g−1), thermal cycling stability, and leakage-proof properties. Furthermore, a PCC-based high-power-density energy device is demonstrated for the tunable thermal regulation by coordinating the orientation of GNPs heat conduction skeleton inside the PCCs with the thermal transport direction of device. The PCC-based module maintains a suitable temperature range of 149–151 °C under various operating conditions and exhibits a decrease of ∼10 °C in the surface peak temperature of power device, showing excellent temperature control performance. Our work holds promising application prospects in the engineering scalable functional PCCs for thermal regulation of electronics and interface thermal management.

Porous carbonated wood/polyethylene glycol/MXene phase change composites: preparation, structure and performances

Porous carbonated wood/polyethylene glycol/MXene phase change composites: preparation, structure and performances

Form-Stable phase change composites with high thermal conductivity and enthalpy enabled by Graphene/Carbon nanotubes aerogel skeleton for thermal energy storage

Thermal energy storage offers enormous potential in energy utilization and phase change materials (PCMs) plays a crucial role in energy management. However, the intrinsically low thermal conductivity, easy liquid leakage and low latent heat of PCMs are great challenges for enabling their use. Herein, a novel method was developed to solve the drawbacks of PCMs by encapsulation of reduced graphene oxide/carbon nanotubes hybrid aerogels (rGCA). The rGCA with interconnected network structures was prepared through chemical reduction and self-assembly under atmospheric pressure drying using carbon nanotubes as the supporting skeleton. The rGCA as 3D scaffold could accommodate paraffin wax (PW) to obtain PW/rGCA phase change composites, which showed excellent shape stability even heating above melting point of PW, and no obvious liquid leakage occurred. PW/rGCA exhibited excellent phase change ability with high phase change enthalpy of 236.7 J/g, which was close to that of pure PW. Moreover, the phase change enthalpy of PW/rGCA still maintained 96.5 % of initial PW even after 100 cycles, revealing the good long-term thermal and chemical stability. The pre-constructed continuous 3D thermally conductive network enabled the thermal conductivity of PW/rGCA up to 1.897 W/mK, much higher than that of pure PW and PW/rGA. The higher thermal diffusion of PW/rGCA resulted in the faster temperature change rate, exhibiting highly reversible thermal behavior of absorbing and releasing heat energy. Furthermore, crosslinked natural rubber (NR) chains were introduced into rGCA to enhance the mechanical property and elasticity, and PW/NR@rGCA composites showed excellent shape stability, good phase change ability and high thermal conductivity, revealing promising applications in energy storage.