西北工业大学《ACS AMI》：打破热导率与潜热权衡！层级核心-壳层相变石墨烯纤维框架用于高级热管理

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。本文，西北工业大学李铁虎 教授、党阿磊 助理研究员等在《ACS Appl. Mater. Interfaces》期刊发表名为“Breaking the Thermal Conductivity–Latent Heat Trade-Off: Hierarchical Core–Shell Phase-Change Graphene Fiber Frameworks for Advanced Thermal Management”的论文，研究提出了一种分层“由内而外”的结构工程策略，用于制备芯-壳型相变石墨烯纤维框架（GFF@PEG）。通过同轴湿法纺丝，将聚乙二醇（PEG）芯紧密封装在氧化石墨烯壳内。

随后的真空浸渍和化学还原产生了“热焊接”效应，将离散的纤维连接起来，将电阻性的点对点接触转化为面与面的互连，从而建立了一条连续的3D声子传输通道。因此，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。与此同时，坚固的石墨烯外壳确保在600个热循环中泄漏率接近于零。在模拟的芯片冷却系统（20 W cm⁻²）中，该材料实现了60.7 °C的显著降温效果。最终，这种全包裹式设计模式突破了传统的界面热障，为大功率电子设备提供了高度稳健的双模式热管理解决方案。

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.

小结

总而言之，通过合理的同轴湿法纺丝和二次网络桥接策略，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）。这种分级核心-壳层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和严重的界面热阻问题。石墨烯壳层作为被限制的PEG芯层的密闭物理屏障，确保即使经过600次连续热循环，其泄漏耐久性仍接近于零；而插层还原氧化石墨烯则将离散的纤维无缝焊接成一条完整的3D声子传输通道。因此，GFF@PEG复合材料突破了传统的性能权衡，在实现77.67 W m−1 K−1的卓越导热系数的同时，还具备极具竞争力的潜热容量（约90 J/g）。通过有限元法（FEM）模拟和实际芯片散热评估的验证，该复合材料展现出卓越的双模式热管理能力——既能快速散逸稳态热量，又能通过向内传播的相变机制有效缓冲瞬态热冲击。最终，这种全包裹式结构工程范式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。

文献：https://doi.org/10.1021/acsami.6c10088