Form-Stable Solar Thermal Heat Packs Prepared by Impregnating Phase-Changing Materials within Carbon-Coated Copper Foams

High-Performance Roller Tube-Shaped Copper Foam Solar Evaporators with Copper Foil Integration for Enhanced Thermal Control

The growing global freshwater shortage and climate crisis are increasing the dependence on water desalination technologies. To meet this pressing demand, innovative solutions that utilize renewable energy sources like solar power, with an emphasis on improving evaporation processes, are essential. Although considerable research has been conducted on a variety of materials and structural designs, the development of highly efficient solar steam generators for large-scale use remains a challenge. Here, we introduce a novel design: a two-layer vertical evaporation cylinder in a roll format that integrates a small, inverted cone-shaped pure copper (ICPC) foam and etched copper foil to enhance thermal management. The primary objective is to advance direct solar desalination and interfacial evaporation by effectively capturing both direct and reflected light while preventing salt accumulation through self-cleaning. This design leverages the optical properties of the three materials─absorption, reflection, and transmission─while providing deeper insights into seawater behavior within the foam's interconnected pores. It also addresses common challenges encountered by traditional solar evaporators, such as salt buildup, uncontrolled water flow, and poor thermal management. This cutting-edge solar evaporation system exhibits exceptional performance, remarkable adaptability to diverse configurations, and represents a breakthrough in sustainable chemistry, featuring an advanced engineering design that achieves an outstanding evaporation rate of 17.15 kg·m-2·h-1 under 1 sun irradiation.

Simulation and Experimental Investigation of the Effect of Pore Shape on Heat Transfer Behavior of Phase Change Materials in Porous Metal Structures

With the gradual increase in energy demand in global industrialization, the energy crisis has become an urgent problem. Due to high heat storage density, small volume change, and nearly constant transition temperature, phase change materials (PCMs) provide a promising method to store thermal energy. In this work, we designed and fabricated three kinds of porous metal structures with hexagonal, rectangular, and circular pores and explored the phase change process of PCMs within them. A two-dimensional numerical model was established to investigate the heat transfer process of PCMs within different shapes of porous metal structures and analyze the influence of heat source location on the thermal performance of the thermal storage units. Visualization experiments were also carried out to reveal the melting process of PCMs within different porous metal structures by a digital camera. The results show that paraffin in a porous metal structure with hexagonal pores has the fastest melting rate, while that in a porous metal structure with circular pores has the slowest melting rate. Under the bottom heating mode, the melting time of the paraffin in porous metal structures with hexagonal pores is shortened by 18.6% compared to that in porous metal structures with circular pores. Under the left heating mode, the corresponding melting time is shortened by 16.7%. These findings in this work will offer an effective method to design and optimize the structure of porous metal and improve the thermal properties of PCMs.

Carboxymethyl chitosan-based hydrogel-Janus nanofiber scaffolds with unidirectional storage-drainage of biofluid for accelerating full-thickness wound healing

Self-pumping wound scaffolds designed for directional biofluid transport are extensively investigated. They efficiently extract excessive biofluids from wounds, while maintaining an optimally humid wound environment, thus facilitating rapid wound healing. However, the existing designed scaffolds are insufficiently focused on stimulating the hydrophobic layer at the wound site, thereby exacerbating inflammation and impeding the wound healing process. Herein, we engineered and fabricated a hydrophilic-hydrophobic-hydrophilic sandwich-structured hydrogel-Janus nanofiber scaffold (NFS) employing a Layer-by-Layer (LbL) method. This scaffold comprises a hydrophilic carboxymethyl chitosan/silver (CMCS-Ag) hydrogel component in conjunction with a poly(caprolactone)/poly(caprolactone)-poly(citric acid)-co-ε-polylysine (PCL/PCL-PCE) Janus NFS. It is noteworthy that the hydrogel-Janus nanofiber scaffold not only demonstrates outstanding water absorption (202.2 %) and unidirectional biofluid transport capability but also possesses high breathability (308.663 m3/m2 h kPa), appropriate pore size (6.7-7.5 μm), excellent tensile performance (270 ± 10 %), and superior mechanical strength (26.36 ± 1.77 MPa). Moreover, in vitro experimentation has convincingly demonstrated the impeccable biocompatibility of hydrogel-Janus NFS. The inherent dual-antibacterial properties in CMCS-Ag and PCE significantly augment fibroblast proliferation and migration. In vivo studies further underscore its capability to expedite wound healing by absorption and expulsion of wound exudates, thereby fostering collagen deposition and vascularization. As such, this work potentially provides fresh insights into the design and fabrication of multifunctional biomimetic scaffolds, holding immense potential in the medical field for efficient wound healing.

Nanoencapsulation of Organic Phase Change Materials in Poly(3,4-Ethylenedioxythiophene) for Energy Storage and Conversion

This work focuses on the encapsulation of two organic phase change materials (PCMs), hexadecane and octadecane, through the formation of nanocapsules of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) obtained by oxidative polymerization in miniemulsion. The energy storage capacity of nanoparticles is studied by preparing polymer films on supporting substrates. The results indicate that the prepared systems can store and later release thermal energy in the form of latent heat efficiently, which is of vital importance to increase the efficiency of future thermoelectric devices.

Form-Stable Composite Phase Change Materials Based on Porous Copper-Graphene Heterostructures for Solar Thermal Energy Conversion and Storage

Solar-thermal energy conversion and storage technology has attracted great interest in the past few decades. Phase change materials (PCMs), by storing and releasing solar energy, are able to effectively address the imbalance between energy supply and demand, but they still have the disadvantage of low thermal conductivity and leakage problems. In this work, new form-stable solar thermal storage materials by impregnating paraffin PCMs within porous copper-graphene (G-Cu) heterostructures were designed, which integrated high thermal conductivity, high solar energy absorption, and anti-leakage properties. In this new structure, graphene can directly absorb and store solar energy in the paraffin PCMs by means of phase change heat transfer. The porous structure provided good heat conduction, and the large surface area increased the loading capacity of solar thermal storage materials. The small pores and superhydrophobic surfaces of the modified porous G-Cu heterostructures effectively hindered the leakage issues during the phase change process. The experimental results exhibited that the thermal conductivity of the prepared form-stable PCM composites was up to 2.99 W/(m·K), and no leakage took place in the solar-thermal charging process. At last, we demonstrated that the PCM composites as an energy source were easily integrated with a thermoelectric chip to generate electric energy by absorbing and converting solar energy.

Novel protic ionic liquids-based phase change materials for high performance thermal energy storage systems

Phase change materials (PCMs) are an important class of innovative materials that considerably contribute to the effective use and conservation of solar energy and wasted heat in thermal energy storage systems (TES). The performance of TES can be improved by using environmentally friendly PCMs called ionic liquids (ILs) based on ethanolamines and fatty acids. The 2-hydroxyethylammonium, bis(2-hydroxyethyl)ammonium, and tris(2-hydroxyethyl)ammonium palmitate ILs, which function is in the temperature range of 30-100 °C and provide a safe and affordable capacity, are introduced in this study for the first time as PCMs. PCMs' chemical composition and microstructure were examined using fourier transformation infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), respectively. DSC was used to evaluate the ILs' latent heat of fusion and specific heat capacity, while TGA was used to establish their thermal stability. Finally, a home-made device with a PCMs (synthesized ILs) container cell and a commercial thermoelectric generator device to record the real-time voltage (V) was used to convert thermal energy into electrical energy.

Phase Change Thermal Storage Materials for Interdisciplinary Applications

Functional phase change materials (PCMs) capable of reversibly storing and releasing tremendous thermal energy during the isothermal phase change process have recently received tremendous attention in interdisciplinary applications. The smart integration of PCMs with functional supporting materials enables multiple cutting-edge interdisciplinary applications, including optical, electrical, magnetic, acoustic, medical, mechanical, and catalytic disciplines etc. Herein, we systematically discuss thermal storage mechanism, thermal transfer mechanism, and energy conversion mechanism, and summarize the state-of-the-art advances in interdisciplinary applications of PCMs. In particular, the applications of PCMs in acoustic, mechanical, and catalytic disciplines are still in their infancy. Simultaneously, in-depth insights into the correlations between microscopic structures and thermophysical properties of composite PCMs are revealed. Finally, current challenges and future prospects are also highlighted according to the up-to-date interdisciplinary applications of PCMs. This review aims to arouse broad research interest in the interdisciplinary community and provide constructive references for exploring next generation advanced multifunctional PCMs for interdisciplinary applications, thereby facilitating their major breakthroughs in both fundamental researches and commercial applications.

ZnO nanorods loading with fatty amine as composite PCMs device for efficient light-to-thermal and electro-to-thermal conversion

Phase change materials (PCMs) with ideal light-to-thermal conversion efficiency play an important role in solar energy storage and conversion. Hence, we report the fabrication of a novel composite PCMs (CPCMs) device based on ZnO nanorods deposited indium tin oxide (ITO) glass loading with fatty amines. ZnO nanorods were deposited on the ITO glass using a three-electrode electrodeposition method, and 1-Hexadecylamine (HDA) was loaded on the ITO glass via spin-coating, followed by spraying polypyrrole (ppy) on the surface of CPCM device to improve thermal conductivity and solar absorption. The as-prepared CPCM device exhibits excellent light-to-thermal conversion efficiency, achieving a high conversion efficiency of 90.2% obtained at 1sun owing to its high light absorption (80%), enhanced thermal conductivity (improved by 57.8%), and the unique vertical aligned nanorods structure which could significantly decrease tortuosity, thereby reducing thermal route and lowering thermal response time. Furthermore, the electro-to-thermal conversion efficiency of the CPCMs device has also been investigated and the results show that it can reach up to 69.8% under a low voltage of 5 V, indicating that the CPCM device has a high potential in the field of electro-to-thermal conversion. Based on the benefits listed above, the CPCM device may serve an ideal platform for a wide range of solar energy storage and conversion applications.

Solar-heating superhydrophobic modified melamine sponge for efficient recovery of viscous crude oil

Developing self-heating sorbents for rapid clean-up of viscous oil spills by using clean solar energy is attracting attention. Still, simple and scalable fabrication approaches of solar-heating sorbents remain challenging. Herein, a facile and practical modification strategy was presented to develop a solar-heating modified melamine sponge (rGO/CNT/MS) by dip-coating layer-by-layer (LBL) electrostatic assembly of GO and CNT with opposite charges onto MS skeleton followed by thermal reduction, without any complicated microfabrication and hydrophobic modification processes. Based on the intercalation of CNT into rGO layers and strong conjugation/hyperconjugation synergy of rGO and CNT, the light sorption ability, photothermal conversion, hydrophobicity and mechanical properties of the rGO/CNT/MS sorbent were further improved compared to rGO/MS and CNT/MS. The surface temperature could reach 75 ℃ in 100 s under 1 sun radiation (1 kW m^-2), which would effectively absorb crude oil by in-situ sunlight-heating to reduce its viscosity. The sorption speed increased by about 30 times compared with no sunlight irradiation, and the continuous sorption capacity was up to 1.71 g/cm² at 610 s driven by pump force. The easily-prepared solar-assisted rGO/CNT/MS with high photothermal performance, corrosion resistance, mechanical compressibility, coating firmness and oil sorption ability showed huge potential application in oil spill recovery.

Fabrication and Thermal Performance of 3D Copper-Mesh-Sintered Foam/Paraffin Phase Change Materials for Solar Thermal Energy Storage

Due to its large latent heat and high energy storage capacity, paraffin as one of the phase change materials (PCMs) has been widely applied in many energy-related applications in recent years. The current applications of paraffin, however, are limited by the low thermal conductivity and the leakage problem. To address these issues, we designed and fabricated form-stable composite PCMs by impregnating organic paraffin within graphite-coated copper foams. The graphite-coated copper foam was prepared by sintering multilayer copper meshes, and graphite nanoparticles were deposited on the surface of the porous copper foam. Graphite nanoparticles could directly absorb and convert solar energy into thermal energy, and the converted thermal energy was stored in the paraffin PCMs through phase change heat transfer. The graphite-coated copper foam not only effectively enhanced the thermal conductivity of paraffin PCMs, but also its porous structure and superhydrophobic surface prevented the paraffin leakage during the charging process. The experimental results showed that the composite PCMs had a thermal conductivity of 2.97 W/(m·K), and no leakage occurred during the charging and discharging process. Finally, we demonstrated the composite PCMs can be readily integrated with solar thermoelectric systems to serve as the energy sources for generating electricity by using abundant clean solar-thermal energy.

Polymer Encapsulation Strategy toward 3D Printable, Sustainable, and Reliable Form-Stable Phase Change Materials for Advanced Thermal Energy Storage

Form-stable phase change materials (PCMs) have garnered tremendous attention in thermal energy storage (TES) owing to their remarkable latent heat. However, the integration of intelligent manufacturing, recycling, and optimized multifunction is considered not feasible for form-stable PCMs due to the restriction of encapsulation technology. Here, an excellent polymer encapsulation strategy is proposed to prepare 3D printable, sustainable, and reliable form-stable PCMs (Si_PCM-x), which are universal for petroleum-based and biobased long alkyl compounds. Si_PCM-x have top-class latent heat, and the phase-change temperatures are tunable from body temperature to high temperature. The in situ formative bottlebrush phase-change polysiloxane networks are used as supporting materials, and the encapsulation mechanism is clarified. Si_rbw-250 can be degraded and re-encapsulated to achieve recycling. Besides, Si_rbw-250 is fabricated as the customer-designed objects with shape-changing behavior via 3D printing. By introducing the metal foams and nano-coatings, the resulting phase-change composites simultaneously exhibit excellent superhydrophobicity, mechanical properties, thermal conductivity, electromagnetic interference shielding behavior, and solar-, electric-, and magnetic-to-thermal energy conversion ability. Besides, S-Ni-Si_PCM-250 can be applied in the wearable functional devices and movable solar-thermal charging. This strategy will lead to huge renovation in the TES field and provide an efficient guideline for designing advanced form-stable PCMs.

High Thermal Effusivity Nanocarbon Materials for Resonant Thermal Energy Harvesting

Carbon nanomaterials have extraordinary thermal properties, such as high conductivity and stability. Nanocarbon combined with phase change materials (PCMs) can yield exceptionally high thermal effusivity composites optimal for thermal energy harvesting. The progress in synthesis and processing of high effusivity materials, and their application in resonant energy harvesting from temperature variations is reviewed.

Conjugated Polymer/Graphene Oxide Nanocomposites—State-of-the-Art

Graphene oxide is an imperative modified form of graphene. Similar to graphene, graphene oxide has gained vast interest for the myriad of industrial applications. Conjugated polymers or conducting polymers are well known organic materials having conducting backbone. These polymers have semiconducting nature due to π-conjugation along the main chain. Doping and modification have been used to enhance the electrical conductivity of the conjugated polymers. The nanocomposites of the conjugated polymers have been reported with the nanocarbon nanofillers including graphene oxide. This review essentially presents the structure, properties, and advancements in the field of conducting polymer/graphene oxide nanocomposites. The facile synthesis, processability, and physical properties of the polymer/graphene oxide nanocomposites have been discussed. The conjugated polymer/graphene oxide nanocomposites have essential significance for the supercapacitors, solar cells, and anti-corrosion materials. Nevertheless, the further advanced properties and technical applications of the conjugated polymer/graphene oxide nanocomposites need to be explored to overcome the challenges related to the high performance.

Application and research progress of phase change materials in biomedical field

Phase change materials (PCMs) are widely used in solar energy utilization, industrial waste heat recovery and building temperature regulation. However, there have been few studies on the application of PCMs in the field of biomedicine. In recent years, some scholars have carried out research in the biomedicine field using the characteristics of PCMs. It was observed that the excellent properties of PCMs enhance the quality of a variety of biomedical applications with many advantages over existing applications, which provide new methods for the treatment of disease. PCMs have broad application prospects in the field of biomedicine. Therefore, a timely review of relevant research progress is of great significance for the continuous development of new methods. Innovatively, from the unique perspective of the biomedical field, this paper systematically reviews the application and related research progress of PCMs from four aspects: cold chains for vaccines and medicines, drug delivery systems, thermotherapy/cold compress therapy and medical dressings. In addition, we summarize and discuss the general principles of the design and construction of PCMs in the biomedical field. Finally, existing problems, solutions and future research directions are also put forward in order to provide a basis for guidance and promote the future applications of phase change materials in the biomedicine field.

Carbon-Based Composite Phase Change Materials for Thermal Energy Storage, Transfer, and Conversion

Phase change materials (PCMs) can alleviate concerns over energy to some extent by reversibly storing a tremendous amount of renewable and sustainable thermal energy. However, the low thermal conductivity, low electrical conductivity, and weak photoabsorption of pure PCMs hinder their wider applicability and development. To overcome these deficiencies and improve the utilization efficiency of thermal energy, versatile carbon materials have been increasingly considered as supporting materials to construct shape-stabilized composite PCMs. Despite some carbon-based composite PCMs reviews regarding thermal conductivity enhancement, a comprehensive review of carbon-based composite PCMs does not exist. Herein, a systematic overview of recent carbon-based composite PCMs for thermal storage, transfer, conversion (solar-to-thermal, electro-to-thermal and magnetic-to-thermal), and advanced multifunctional applications, including novel metal organic framework (MOF)-derived carbon materials are provided. The current challenges and future opportunities are also highlighted. The authors hope this review can provide in-depth insights and serve as a useful guide for the targeted design of high-performance carbon-based composite PCMs.

Magnetic cellulose nanocrystals hybrids reinforced phase change fiber composites with highly thermal energy storage efficiencies

The intrinsic intermittence of solar energy raises the necessity for thermal energy storage (TES) systems to balance the contradiction between energy supply and demand energy. This work experimentally provides solid-liquid phase change materials (PCMs) with sufficient storage capacity and discharging rate to offer heating for agriculture products by enhancing heat transfer in phase change fiber composites (PCF). To achieve this, we prepared dipole responsive magnetic/solar-driven PCF composites reinforced with magnetic cellulose nanocrystals hybrids (MCNC). The obtained PCF/MCNC-5% showed excellent magnetic property with a saturation magnetization (MS) value of 1.3 emu/g and effective latent heat phase change enthalpies of 69.2 ± 3.5 J/g - 83.1 ± 4.2 J/g. More importantly, PCF/MCNC-5% showed robust high magnetic to thermal energy storage efficiency of 32.5 % and solar light accelerated energy storage efficiency of 58.5 %. These advantages make the PCF composites promising and more desirable for drying and preservation of the fruits and other agriculture products.

Self-dispersible graphene quantum dots in ethylene glycol for direct absorption-based medium-temperature solar-thermal harvesting

Poor dispersion stability of carbon nanofluids is one of the key issues limiting their solar-thermal applications especially under medium-to-high temperatures. Herein, this work reported a facile way to prepare stably dispersed graphene quantum dot-ethylene glycol (GQD-EG) medium-temperature solar-thermal nanofluids. The hydroxyl-terminated GQDs were synthesized by a scalable hydrothermal approach. The obtained GQDs have a small particle size, narrow particle size distribution and are self-dispersible within EG fluids. The GQD-EG nanofluids maintained their uniform dispersion after continuous heating at 180 °C for 7 days. The hydrogen bonding between the hydroxyl group on the surface of GQDs and the EG molecules helped achieve homogenous dispersion of GQDs in the nanofluids, and the small particle size and low density of GQDs helped mitigate the sedimentation tendency. The dispersed GQD-EG nanofluids have demonstrated broadband absorption of sunlight, high specific heat capacity and low viscosity, which are all desired for high-performance direct absorption-based solar-thermal energy. The prepared GQD-EG nanofluids have exhibited consistent volumetric harvesting of solar-thermal energy under concentrated solar illumination with a heating temperature up to 170 °C.

Self-dispersible graphene quantum dots in ethylene glycol enable stable nanofluidic solar-thermal energy harvesting at medium temperatures.

Infiltration properties of n-alkanes in mesoporous biochar: The capacity of smokeless support for stability and energy storage

Biochar, also named biocarbon, is a solid particulate material produced from the thermal decomposition of biomass at moderate temperatures. It has progressively become the topic of scientific interest in energy storage and conversion applications due to its affordability, environment friendliness, and structural tunability. In this study, biochar (obtained 600 °C pyrolysis) was introduced as phase change materials (PCMs) support. Three different n-alkanes (such as dodecane, tetradecane, and octadecane) are used as PCMs. The PCMs were infiltrated in the biochar network via the vacuum impregnation method. Among the biochar/n-alkane composites, one from octadecane exhibited a high latent heat storage capacity of 91.5 kJ/kg, 15.7 % and 25.9 % higher than that of dodecane and tetradecane-based composites, respectively. The molecular length of the PCMs and intermolecular interaction between the functional groups play an imperative role. The infiltration ratio of PCM in the biochar reached 50.1 % with improved thermal stability and chemical compatibility. This is attributed to the favorable morphological and structural properties (e.g., large BET surface area and mesopore structure) of the biochar that resides the n-alkanes found in the nanosized chain length. Hence, this report will lay a foundation for the application of biochars in thermal energy management systems.

Large-Scale Fabrication of Robust Artificial Skins from a Biodegradable Sealant-Loaded Nanofiber Scaffold to Skin Tissue via Microfluidic Blow-Spinning

Given that many people suffer from large-area skin damage, skin regeneration is a matter of high concern. Here, an available method is developed for the formation of large-area robust skins through three stages: fabrication of a biodegradable sealant-loaded nanofiber scaffold (SNS), skin tissue reconstruction, and skin regeneration. First, a microfluidic blow-spinning strategy is proposed to fabricate a large-scale nanofiber scaffold with an area of 140 cm × 40 cm, composed of fibrinogen-loaded polycaprolactone/silk fibroin (PCL/SF) ultrafine core-shell nanofibers with mean diameter of 65 nm. Then, the SNS forms, where the gelling reaction of fibrin sealant occurs in situ between thrombin and fibrinogen on PCL/SF nanofiber surface, to promote the migration and proliferation of fibroblasts, accelerating skin regeneration. Through an in vivo study, it is shown that the SNS can rapidly repair acute tissue damage such as vascular bleeding and hepatic hemorrhage, and also promote angiogenesis, large-area abdominal wall defect repair, and wound tissue regeneration for medical problems in the world. Besides, it avoids the risk of immune rejection and secondary surgery in clinical applications. This strategy offers a facile route to regenerate large-scale robust skin, which shows great potential in abdominal wall defect repair.

Three-Dimensional Porous Solar-Driven Interfacial Evaporator for High-Efficiency Steam Generation under Low Solar Flux

Solar steam generation is critical for many important solar-thermal applications, but is challenging to achieve under low solar flux due to the large evaporation enthalpy of water. Here, we demonstrate a three-dimensional porous solar-driven interfacial evaporator that can generate 100 °C steam under 1 sun illumination with a record high solar-to-steam conversion efficiency of 48%. The high steam generation efficiency is achieved by localizing solar-thermal heating at the evaporation surface and controlling the water supply onto the porous evaporator through tuning its surface wettability, which prevents overheating of the evaporator and thus minimizes conductive, convective, and radiative heat losses from the evaporator. The design of steam outlet located at the sidewall of the evaporator rather than from the solar absorber surface not only facilitates the collection of generated steam, but also avoids potential blockage of solar radiation by the condensing steam. The high-efficiency solar-driven evaporator has been used to generate hot steam for outdoor removal of paraffin on the wall of oil pipelines, offering a promising solution to mitigate the wax deposition issue in petroleum extraction processes.