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Inorganic hydrated salt phase change materials (PCMs) have received great attention due to their capabilities to reduce building energy consumption and improve building thermal comfort. In this work, a modified PCM (DHPD-STP) with a low supercooling degree was first prepared by using disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O, DHPD) as the matrix and sodium thiosulfate pentahydrate (Na2S2O3·5H2O, STP) as a nucleating agent. Then expanded graphite (EG) was added to DHPD-STP to afford a novel form-stable composite phase change material (CPCM). The novel CPCM obtained had a phase transition temperature (34.74 °C) appropriate for building thermal management, an excellent phase change enthalpy (184.39 J/g), and an extremely low supercooling degree (1.1 °C). The addition of EG greatly improved the form stability and cycle stability of the CPCM. Even after 200 cycles, the CPCM prepared still had a high enthalpy of phase changes (164.54 J/g). More importantly, the use of CPCM-loaded roofs effectively mitigated the variation of room temperature and improved indoor thermal comfort. The above results demonstrate the great potential of the CPCM prepared for passive building thermal management.Graphical Abstract

A composite phase change material (PCM) was prepared by incorporating paraffin (PA) with expanded graphite (EG) and nano-metal particles to improve the thermal conductivity and reduce the leakage performance of PA once it melts and, consequently, develop a more efficient PCM for a personal phase change cooling system. A series of experiments was carried out by a scanning electron microscope, a differential scanning calorimeter, a hot-disk thermal analyzer, and leakage tests on the composite PCM with various mass fractions of EG and metals (i.e., Cu, Al, Ni, and Fe). Through comprehensive consideration of the thermal conductivity, leakage, and homogeneity, a composite PCM with the optimal proportion (PA-EG11%-Cu1.9%) was screened out. Its thermal conductivity was significantly improved nine times, while the phase change enthalpy showed a minimal decrease. In addition, the relationships of the composite PCM with its temperature and density were systematically investigated. The experimental results are important for determining the proper package density of PCM for application into a personal cooling system because its weight is crucial for the system design and benefits the performance comparison of various PCMs prepared under various conditions. Lastly, the heat storage efficiency of the PA–EG–Cu material was investigated using heat storage tests. Cooling performance clearly improved compared to the PCM without nano-particles added.

Highlights The prepared Ge/SA biomass aerogel with multiple crosslinked networks have excellent flame retardancy and thermal insulation properties. The prepared SAT/TPEE/EG composite phase change material (CPCM) has a thermal storage density as high as 811.9 J g –1 and good flame retardancy. In the composite material of CPCM coupled with aerogel, the CPCM continuously absorbs heat for the aerogel, thus maximizing heat transfer and spreading. Thermal runaway (TR) is considered a significant safety hazard for lithium batteries, and thermal protection materials are crucial in mitigating this risk. However, current thermal protection materials generally suffer from poor mechanical properties, flammability, leakage, and rigid crystallization, and they struggle to continuously block excess heat transfer and propagation once thermal saturation occurs. This study proposes a novel type of thermal protection material: an aerogel coupled composite phase change material (CPCM). The composite material consists of gelatin/sodium alginate (Ge/SA) composite biomass aerogel as an insulating component and a thermally induced flexible CPCM made from thermoplastic polyester elastomer as a heat-absorbing component. Inspired by power bank, we coupled the aerogel with CPCM through the binder, so that CPCM can continue to ‘charge and store energy’ for the aerogel, effectively absorbing heat, delaying the heat saturation phenomenon, and maximizing the duration of thermal insulation. The results demonstrate that the Ge/SA aerogel exhibits excellent thermal insulation (with a temperature difference of approximately 120 °C across a 1 cm thickness) and flame retardancy (achieving a V-0 flame retardant rating). The CPCM exhibits high heat storage density (811.9 J g −1 ), good thermally induced flexibility (bendable above 40 °C), and thermal stability. Furthermore, the Ge/SA-CPCM coupled composite material shows even more outstanding thermal insulation performance, with the top surface temperature remaining at 89 °C after 100 min of exposure to a high temperature of 230 °C. This study provides a new direction for the development of TR protection materials for lithium batteries.

To find a medium temperature phase change heat storage material with high thermal conductivity and heat storage ability, expanded graphite (EG) with high thermal conductivity is used as the carrier material, and the binary mixed molten salt of 88 wt% LiNO3–12 wt% NaCl is used as the phase change material (PCM). EG and PCM are uniformly dispersed by ultrasound crushing method. To get the right EG addition ratio, LiNO3–NaCl/EG composite PCMs (LNE) with EG mass ratio of 10 %, 15 %, 20 %, and 30 % are prepared by static melt adsorption method. The melting point, phase change enthalpy and other parameters of the composite material are tested and analyzed. The experimental results show that the melting temperature and the phase change enthalpy of LNE gradually decrease with the increase of EG mass proportion. For all LNE samples, the adsorption ratio of PCM exceeds 90 % to 95 %. The thermal conductivity of the PCM greatly improves with the increase of EG mass proportion. The thermal conductivity of the composites with 15 wt% EG is 6.532 W·m−1·K−1, which is about 3.7 times that of the binary mixed molten salt. The thermal conductivity increases with the increase of the apparent density. The composite PCM has stable performance. The 85 wt% LiNO3–NaCl/15 wt% EG composite PCM has the best overall performance.

Form-stable composite phase change materials exhibit considerable application prospects in the insulation of submarine oil and gas pipelines due to their good chemical stabilities, levels of thermal insulation, and leakage resistances. In this study, composite phase change materials (PU-MPCM) were prepared for application in submarine oil and gas pipelines using a polyurethane (PU) matrix and different contents of a microencapsulated phase change material (MPCM). The unsteady heat transfer of PU-MPCM was studied using the COMSOL Multiphysics modeling software, and an insulation study was conducted using the composites. PU-MPCM exhibited a high thermal storage performance and favorable shape stability, and the relative effective enthalpy coefficients of PU-MPCM with different MPCM contents were greater than 80%. The maximum amount of added MPCM was 24 wt% (PU-MPCM24), and the melting enthalpy of PU-MPCM24 reached 35.95 kJ/kg, with an effective thermal conductivity as low as 0.16 W/(m K). The holding time of PU-MPCM24 could be increased by 229.79% compared to that of pure PU, and PU-MPCM exhibited good mechanical properties and low water absorption, rendering it suitable for use in underwater environments. These excellent thermal properties indicate the considerable potential of PU-MPCM24 for use in the thermal management and insulation of submarine oil and gas pipelines.Graphical AbstractPolyurethane composite embedded with microencapsulated phase change materials shows excellent thermal storage performance and good adaptability to underwater environments.

Exploiting an advanced material simultaneously with effective thermal management (TM) and electromagnetic interference (EMI) shielding capacity is ungently demanded yet challenging for the miniaturized and integrated electronics. Anisotropic networks can be impregnated with phase change materials (PCMs) to fabricate multifunctional shape-stable PCMs (ss-CPCMs) simultaneously with excellent TM and EMI shielding, which is rarely reported. Herein, the anisotropic cellulose/polyacrylamide/graphene nanosheet/silver nanowire (CPGxAy) hybrid aerogels were successfully prepared using directional freeze-drying method, and then utilized as supporting skeletons to embed polyethylene glycol (PEG) via vacuum-assistant impregnation. Profited by the synergistic effect of graphene nanosheets (GNPs) and silver nanowires (AgNWs), the resultant polyethylene glycol@cellulose/polyacrylamide/graphene nanosheet/silver nanowire hybrid aerogel (PEG@CPGxAy) ss-CPCMs exhibit fascinating thermal conductivity (TC) of 0.84 W/m·K (200% increase in comparison with that of pure PEG) and anisotropic average EMI shielding effectiveness (SE) of 71.08 dB along the transverse direction and 35.21 dB along the longitudinal direction, while remaining high melting and crystallization enthalpy efficiency of 93.47% and 93.08%, respectively. In addition, PEG@CPGxAy ss-CPCMs also display great shape stability, thermal stability, and cyclic reusability in the storing/releasing latent heat processes. This investigation sheds new light on designing and fabricating ss-CPCMs with pretty comprehensive properties for TM and EMI shielding of modern electronics.Graphical Abstract

Based on existing studies, we identified that the heat sinks used in wearable thermoelectric coolers (WTECs) are predominantly bulky, which limits their practicality and comfort. To address this issue, we propose the use of phase-change composite materials (PCCMs) due to their inherent flexibility and thermal properties. Through comprehensive theoretical analysis, numerical simulations, and experimental validation, we successfully optimized the design of a WTEC.

Alumina supported copper oxide (CuO/Al2O3) and Nickel Oxide (NiO) loaded polymer composite matrices supported n‐hexadecane (HD) based composite phase change materials (PCMs) are prepared and characterized. The polymer composites assigned as supporting matrices for shape‐stabilization of PCM are synthesized by emulsion‐templating approach, and the composite PCMs are prepared by impregnation of HD into polymer composite matrices. The effect of CuO/Al2O3 and NiO particles of different sizes used as heat transfer promoters in the supporting matrices, on the morphological properties, thermal stabilities, and latent heat storage characteristics (LHS) of the composite PCMs are evaluated using different characterization methods. The melting temperature of the obtained composite PCMs is found to be ≈18 °C and the latent heat of melting values varied in the range of 95.0−114.5 J g−1. The heat transfer properties of the composite PCMs are investigated by performing a T‐History test for obtaining heat storage and release curves. The composite PCMs with NiO loaded supporting matrices are exhibited higher thermal stability and heat storage capacity in addition to enhanced thermal conduction properties than the CuO/Al2O3 included composite PCMs. According to the results, it is revealed that shape‐stabilized, thermally enhanced composite PCMs are remarkable energy storage materials with the potential for use in low‐temperature thermal energy storage systems. This study focuses on the preparation of CuO/Al2O3 and NiO loaded polymer composite matrices supported n‐hexadecane based composite PCMs. The effect of CuO/Al2O3 and NiO particles as heat transfer promoters in supporting matrices, on the morphological properties, thermal stabilities, and latent heat storage characteristics of the composite PCMs are evaluated. The shape‐stabilized, thermally enhanced composite PCMs are remarkable materials for use in thermal energy storage systems.

The utilization of phase change materials (PCMs) for effective thermal management applications is limited due to their inherently low thermal transport properties. This study explores the enhancement of thermal properties for the organic mixture (OM34) PCM through the addition of environmentally friendly coconut shell carbon powder (CP) and highly conductive graphene platelets (GP). The composite phase change materials (CPCM) were prepared by dispersing GP and CP in OM34 with different mass concentrations. The FTIR spectrum peaks designated no chemical reaction, only physical interaction, upon the addition of carbonaceous materials. Differential scanning calorimetry (DSC) results indicated that the latent heat capacity of pure PCM was enhanced by 6.3% during melting and 8.4% during freezing for 1.0% of CPCM. The results indicated a considerable increase in the specific heat capacity of pure PCM with the addition of 1.0% CPCM, about 1–2% in solid states and 2–4% in liquid states. In addition, the dispersion of GP and CP prolonged the thermal degradation of pure PCM without compromising its chemical structure and favorable thermal properties. The results confirmed that 1.0% of CPCM exhibited the highest thermal conductivity enhancement of 69.27% in solid states and 59.46% in liquid states. In conclusion, this composite material holds potential applications in solar thermal, and electronic cooling, addressing the limitations of traditional PCMs in thermal management.

Phase change cold storage materials are functional materials that rely on the latent heat of phase change to absorb and store cold energy. They have significant advantages in slight temperature differences, cold storage, and heat exchange. Based on the research status of phase change cold storage materials and their application in air conditioning systems in recent years, this paper provides an overview of the materials and their enhanced research progress. It summarizes the types of phase change cold storage air conditioning systems, optimization schemes, and system applications. This paper also identifies the current issues in phase change cold storage air conditioning and discusses the development trends in cold storage materials and air conditioning systems. It anticipates that future advancements will focus on composite phase change cold storage materials and low-energy consumption intelligent phase change cold storage air conditioning systems in steam compression using spherical capsules and concave–convex plate PCM.