Multifunctional Phase Change Materials Research Articles

Dual-encapsulated phase change composites with hierarchical MXene-graphene monoliths in graphene foam for high-efficiency thermal management and electromagnetic interference shielding

Multifunctional phase change materials (PCMs) simultaneously combining high-efficiency thermal management and electromagnetic interference (EMI) shielding performance are urgently desirable yet highly challenging for miniaturized and integrated electronics. Herein, an innovative polyethylene glycol (PEG) composite is developed based on a dual-encapsulation design of vertically aligned MXene-graphene monoliths in graphene foam (MGGF hybrid aerogel). The MXene-graphene monoliths are first incorporated with reticulated graphene foam via unidirectional freezing to construct a hybridized semi-interpenetrated framework, followed by thermal annealing and encapsulating molten PEG, synchronously forming orientational-interlinked thermal pathways in PCM matrix. Impressively, the resultant MGGF/PEG composite achieves a high through-plane thermal conductivity of 11.39 W m−1 K−1 and excellent EMI shielding effectiveness of ∼56.6 dB, as well as desirable latent heat density up to 160.3 J g−1, leakage-proof ability, and superior thermal reliability. Additionally, the MGGF/PEG-based device is demonstrated for thermal energy management toward versatile demands in electronics cooling and solar-thermoelectric conversion. This work sheds new light on designing multifunctional composite PCMs and raises tremendous application prospects for electronic thermal management and solar energy utilization.

MoS2-decorated carbonized melamine foam/reduced graphene oxide network for constructing polyethylene-glycol-based multifunctional phase change materials toward multiple energy harvesting and microwave absorbing applications

The limited functions of traditional phase change materials (PCMs), such as thermal energy storage and temperature regulation, cannot fully satisfy the diversified requirements of various fields. Therefore, the development of multifunctional PCMs (MPCMs) is gradually gaining significant research attention. Herein, a functional MoS2-decorated carbonized melamine foam (CMF)/reduced graphene oxide (rGO) network (CMF/rGO/MoS2) is designed for developing MPCMs, in which CMF acts as a template, while rGO and MoS2 serve as functional fillers. Polyethylene glycol (PEG) is introduced into the network as a PCM using a vacuum‐assisted impregnation method. The obtained PEG@CMF/rGO/MoS2 composite has a high PEG content of 92.1 wt%, which contributes to its high melting and crystallization enthalpies of 169.3 and 165.9 J g−1, respectively. Simultaneously, the hybrid of rGO and MoS2 possesses good photon harvesting ability and electrically conductive properties, and endows the composite with light-to-thermal and electric-to-thermal energy conversion functions. Moreover, the synergistic effect of the three-dimensional porous structure and high dielectric loss capability of CMF/rGO/MoS2 render the composite a microwave absorbing material. As a result, the minimum reflection loss and maximum efficient bandwidth of PEG@CMF/rGO/MoS2 are −32.49 dB and 6.16 GHz at a thicknesses of 2.1 and 2.4 mm, respectively. Hence, our study provides an efficient strategy for developing MPCMs adaptable to different application requirements.

Multi-functional phase change materials with anti-liquid leakage, shape memory, switchable optical transparency and thermal energy storage

Multi-functional phase change materials with anti-liquid leakage, shape memory, switchable optical transparency and thermal energy storage

Multifunctional Phase Change Composites Based on Elastic MXene/Silver Nanowire Sponges for Excellent Thermal/Solar/Electric Energy Storage, Shape Memory, and Adjustable Electromagnetic Interference Shielding Functions.

Multifunctional phase change materials (PCMs) are highly desirable for the thermal management of miniaturized and integrated electronic devices. However, the development of flexible PCMs possessing heat energy storage, shape memory, and adjustable electromagnetic interference (EMI) shielding properties under complex conditions remains a challenge. Herein, the multifunctional PCM composites were prepared by encapsulating poly(ethylene glycol) (PEG) into porous MXene/silver nanowire (AgNW) hybrid sponges by vacuum impregnation. Melamine foams (MFs) were chosen as a template to coat with MXene/AgNW (MA) to construct a continuous electrical/thermal conductive network. The MF@MA/PEG composites showed a high latent heat (141.3 J/g), high dimension retention ratio (96.8%), good electrical conductivity (75.3 S/m), and largely enhanced thermal conductivity (2.6 times of MF/PEG). Moreover, by triggering the phase change of the PEG, the sponges displayed a significant photoinduced shape memory function with a high shape fixation ratio (∼100%) and recovery ratio (∼100%). Interestingly, the EMI shielding effectiveness (SE) can be adjusted from 12.4 to 30.5 dB by a facile compression-recovery process based on shape memory properties. Furthermore, a finite element simulation was conducted to emphasize the advantage of the MF@MA/PEG composites in the thermal management of chips. Such flexible PCM composites with high latent heat storage, light-actuated shape memory, and adjustable EMI shielding functions exhibit great potential as smart thermal management materials in military and aerospace applications.

Next Generation Phase Change Materials as Multifunctional Watery Suspension for Heat Transport and Heat Storage

AbstractThe phase change materials (PCM) are known since years with high thermal storage capacity but with limited applications. The modified PCM mainly paraffin watery suspensions, so called PCM slurry, improve some PCM drawbacks (thermal conductivity) and as paraffin multifunctional fluids can work in both, heat transport and heat storage for cooling technology applications. The structural and thermophysical properties of two types PCM slurry were good basis for comparison of their efficiency: paraffin microcapsule slurry (A) and paraffin emulsion slurry (B), both working in temperature range of phase transition from 2-12 degreesC. The equipments as differential scanning calorimetry (DSC), model NETZSCH DSC 200 PC; scanning electron microscopy (SEM), JOEL model JSM-5510; hot stage optical microscopy, LINKAM model TMS 94 and hand made thermal cycling system operational with Danfoss cooling machine that ensured 2 kW cooling capacity at 40oC; gave accurate results, characterizing completely, from structural and thermal point of view both types of PCM multifunctional structured fluids. Structural stability of the advanced phase change multifunctional fluids was discussed on sample imaging in variable magnifications made by method of Hot Stage microscopy and precise SEM study. Systematization of the DSC results obtained, including temperature range of phase transition and thermal storage capacity, measured before and after repeatable thermal cycling of the PCM multifunctional fluids, allowed selection of the PCM slurry working samples with relatively high thermal capacity applicable to further development in prototypes. Heat absorbed/released, calculated by NETZSCH DSC software, was for PCM slurry A in the range of 80 to 82 kJ/kg, while PCM slurry B showed thermal storage capacity from 56 to 53 kJ/kg. Correlation between the structural properties and thermal storage capacity of the phase change multifunctional fluids led to practical conclusions concerning: homogeneity; crystal growth/conditions; structural compatibility between components; prediction of the heat flow behavior of multifunctional PCM slurries in cooling technology for storage and transport of heat.