1成果简介 

电子设备的快速微型化使功率密度呈指数级增长，导致热量积聚和瞬态热冲击成为主要瓶颈。相变热界面材料（PC-TIMs）提供了一种有前景的解决方案，但其应用受到固有热导率较低和液体泄漏问题的制约。此外，传统的由外而内浸渍策略在提高热导率与保持潜热之间存在严重的权衡。基于此，本文西北工业大学李铁虎教授、党阿磊副教授团队在《ACS Applied Materials & Interfaces》发表名为"Breaking the Thermal Conductivity–Latent Heat Trade-Off: Hierarchical Core–Shell Phase-Change Graphene Fiber Frameworks for Advanced Thermal Management"的论文，提出一种分层"由内而外"的结构工程策略，通过同轴湿法纺丝将聚乙二醇（PEG）芯致密封装于氧化石墨烯（GO）壳内，再经真空浸渍与化学还原构筑出核-壳型相变石墨烯纤维框架（GFF@PEG），用以突破浸渍型相变材料固有的性能权衡。

此外，该工作利用真空浸渍与化学还原产生的"热焊接（thermal soldering）"效应，将离散纤维桥接为表面-表面互连，把原本电阻性的点-点接触转化为连续贯通的 3D 声子传输高速通道，从结构设计层面根除了传统浸渍型复合材料（GA@PEG）严重的界面热阻与液体泄漏隐患。经同轴湿法纺丝、GO 浸渍、冷冻干燥与化学还原的逐级构筑，该 GFF@PEG 复合材料在保持约 90 J g?1 潜热容量的同时实现了 77.67 W·m?1·K?1 的卓越热导率；同时，该坚固的石墨烯外壳确保在 600 次热循环后泄漏趋近于零，并在 20 W·cm?2 的模拟芯片冷却系统中带来 60.7 °C 的显著降温，验证了其双模式热管理能力。

本研究提出了一种全包裹式核-壳相变石墨烯纤维框架新范式，以"由内而外"的层级结构同时满足了高导热与高储热的双重需求，为大功率电子器件提供了一种可扩展、高稳健的双模式（稳态导热 + 瞬态相变缓冲）先进热管理解决方案。

2图文导读

Figure 1.Schematic illustration of the fabrication process and thermal management application of the GFF@PEG composite. (a) Preparation of the core–shell phase-change graphene fiber via ① coaxial wet-spinning and the dual-directional diffusion of Ca2+ from both the coagulation bath and the core dope facilitates rapid and robust cross-linking of the GO shell. (b) Schematic of the subsequent fabrication route and TIM packaging configuration: the assembled fiber network undergoes ② GO impregnation, followed by ③ freeze-drying and ④ chemical reduction to yield the final GFF@PEG composite, which is applied as a thermal interface material in a typical chip packaging structure.

Figure 2.Morphological and structural characterizations of the core–shell fibers and the GFF@PEG composite. (a) Surface and (b) cross-sectional SEM images of the hollow GO fiber without the PEG core. (c) The controllable thickness of the GO shell as a function of the sheath/core spinning speed ratio. Cross-sectional SEM images of (d) the core–shell phase-change GO fiber and (e) the magnified view of the encapsulated PEG core. (f) SEM image illustrating the continuous reduced rGO network tightly wrapping and bridging the core–shell phase-change fibers in the GFF@PEG composite (the fiber is false-colored green for clarity). (g) Raman spectra, (h) XRD patterns, (i) XPS survey spectra, and (j) high-resolution C 1s XPS spectra of the composite before (GOFF@PEG) and after chemical reduction (GFF@PEG).

Figure 3.Thermal conductivity performance characterization and mechanism. (a) Thermal conductivity (orange bars, left y-axis) and thermal diffusivity (blue bars, right y-axis) of pure PEG, GA@PEG, and GFF@PEG. (b) Comparison of the thermal conductivity of GFF@PEG with other advanced thermal management materials reported in the literature, including liquid metal (LM), graphene, and boron nitride (BN)-based composites. (c) Schematic illustration of the heat transfer mechanisms, revealing how the insulating PEG coating on graphene aerogel disrupts thermal pathways in GA@PEG, whereas the interconnected GFF@PEG framework establishes unimpeded and continuous phonon transport pathways. (d) Schematic of the setup for evaluating heat dissipation performance using a ceramic heater. (e) Heating and (f) cooling temperature-time profiles of pure GFF, GA@PEG, and GFF@PEG, highlighting the distinct phase-change plateaus.

Figure 4.Finite element simulation of transient heat transfer and phase change behavior. Temperature profiles and corresponding contour maps of (a, b) GA@PEG and (c, d) GFF@PEG at the same heating time; liquid fraction profiles and corresponding contour maps of (e, f) GA@PEG and (g, h) GFF@PEG. All one-dimensional profiles are extracted along the vertical dashed lines marked in the contour maps, which are selected along the dominant heat transfer path of each structure to reveal the regulatory effect of structural design on phase change front evolution.

Figure 5.Thermal energy storage, shape stability, and long-term cyclic reliability of the GFF@PEG composite. (a, b) DSC endothermic and exothermic curves, alongside (c) the corresponding melting and solidification enthalpies of pure PEG, GA@PEG, and GFF@PEG. (d) TGA curves and corresponding loading fractions of the components. (e) Comparison of the thermal conductivity and latent heat of the GFF@PEG composite with other state-of-the-art phase-change materials reported in the literature. (f) Optical photographs demonstrating the shape stability and leakage behavior of the samples placed on a heating stage at 80 °C. (g) Residual mass retention of GA@PEG and GFF@PEG over 600 continuous heating-cooling cycles. (h) XRD patterns of the GFF@PEG composite before and after 600 thermal cycles.

Figure 6.Practical performance evaluation of the GFF@PEG composite as a PC-TIM for advanced electronic cooling. (a) Schematic illustration of the customized CPU cooling simulation system. (b) Infrared thermal images of the simulated chip with and without the GFF@PEG TIM at steady state under 20 W cm?2; the green wireframe marks the central region for temperature data sampling, located directly above the heating source. (c) Corresponding transient temperature-time profiles of the simulated chip operating at a power density of 20 W cm?2. (d) Temperature evolution of the simulated chip under stepwise escalating power densities from 5 to 20 W cm?2. (e) Equilibrium surface temperature of the heater as a function of the input power density. (f) Schematic illustration of the dual thermal protection mechanism of the GFF@PEG TIM under different heat loads. Under low steady heat flow, heat is efficiently conducted through the interconnected rGO fiber skeleton; under high transient heat flow, the PEG core absorbs latent heat via phase transition to provide thermal buffering. (g) Long-term dynamic thermal cycling stability test of the GFF@PEG composite.

3小结 

总而言之，通过合理的同轴湿法纺丝与二次网络桥接策略，本研究成功开发出一种高度可靠、超导热的核心-壳层相变石墨烯纤维框架（GFF@PEG）。这种分级核-壳结构从根本上解决了浸渍型相变复合材料（GA@PEG）长期存在的液体泄漏与严重界面热阻问题——石墨烯壳层作为受限 PEG 芯的密闭物理屏障，使 600 次连续热循环后泄漏耐久性趋近于零；而插层还原氧化石墨烯将离散纤维无缝焊接为完整的 3D 声子传输通道。因此，GFF@PEG 在突破传统性能权衡的同时，以 77.67 W·m?1·K?1 的卓越热导率兼具约 90 J·g?1 的潜热容量，并经有限元模拟与真实芯片散热验证，展现出"稳态快速导热 + 瞬态相变缓冲"的双模式热管理能力，为大功率电子器件的先进热管理提供了高度可扩展且稳健的解决方案。

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