Graphene is usually embedded into polymer matrices for the development of thermally conductive composites, preferably forming an interconnected and anisotropic framework. Currently, the directional self‐assembly of exfoliated graphene sheets is demonstrated to be the most effective way to synthesize anisotropic graphene frameworks. However, achieving a thermal conductivity enhancement (TCE) over 1500% with per 1 vol% graphene content in polymer matrices remains challenging, due to the high junction thermal resistance between the adjacent graphene sheets within the self‐assembled graphene framework. Here, a multiscale structural modulation strategy for obtaining highly ordered structure of graphene framework and simultaneously reducing the junction thermal resistance is demonstrated. The resultant anisotropic framework contributes to the polymer composites with a record‐high thermal conductivity of 56.8–62.4 W m−1 K−1 at the graphene loading of ≈13.3 vol%, giving an ultrahigh TCE per 1 vol% graphene over 2400%. Furthermore, thermal energy management applications of the composites as phase change materials for solar‐thermal energy conversion and as thermal interface materials for electronic device cooling are demonstrated. The finding provides valuable guidance for designing high‐performance thermally conductive composites and raises their possibility for practical use in thermal energy storage and thermal management of electronics.

As the power density and integration level of electronic devices increase, there are growing demands to improve the thermal conductivity of polymers for addressing the thermal management issues. On the basis of the ultrahigh intrinsic thermal conductivity, graphene has exhibited great potential as reinforcing fillers to develop polymer composites, but the resultant thermal conductivity of reported graphenebased composites is still limited. Here, an interconnected and highly ordered graphene framework (HOGF) composed of high-quality and horizontally aligned graphene sheets was developed by a porous film-templated assembly strategy, followed by a stress-induced orientation process and graphitization post-treatment. After embedding into the epoxy (EP), the HOGF/EP composite (24.7 vol %) exhibits a record-high in-plane thermal conductivity of 117 W m −1 K −1 , equivalent to ≈616 times higher than that of neat epoxy. This thermal conductivity enhancement is mainly because the HOGF as a filler concurrently has high intrinsic thermal conductivity, relatively high density, and a highly ordered structure, constructing superefficient phonon transport paths in the epoxy matrix. Additionally, the use of our HOGF/EP as a heat dissipation plate was demonstrated, and it achieved 75% enhancement in practical thermal management performance compared to that of conventional alumina for cooling the high-power LED.

The rapid increase of operation speed, transmission efficiency, and power density of miniaturized devices leads to a rising demand for electromagnetic interference (EMI) shielding and thermal management materials in the semiconductor industry. Therefore, it is essential to improve both the EMI shielding and thermal conductive properties of commonly used polyolefin components (such as polyethylene (PE)) in electronic systems. Currently, melt compounding is the most common method to fabricate polyolefin composites, but the difficulty of filler dispersion and high resistance at the filler/filler or filler/matrix interface limits their properties. Here, a fold fabrication strategy was proposed to prepare PE composites by incorporation of a well-aligned, seamless graphene framework premodified with MXene nanosheets into the matrix. We demonstrate that the physical properties of the composites can be further improved at the same filler loading by nanoscale interface engineering: the formation of hydrogen bonds at the graphene/MXene interface and the development of a seamlessly interconnected graphene framework. The obtained PE composites exhibit an EMI shielding property of ∼61.0 dB and a thermal conductivity of 9.26 W m −1 K −1 at a low filler content (∼3 wt %, including ∼0.4 wt % MXene). Moreover, other thermoplastic composites with the same results can also be produced based on our method. Our study provides an idea toward rational design of the filler interface to prepare high-performance polymer composites for use in microelectronics and microsystems.

The rapid development of highly integrated microelectronic devices causes urgent demands for advanced thermally conductive adhesives (TCAs) to solve the interfacial heat‐transfer issue. Due to their natural 2D structure and isotropic thermal conductivity, metal nanoflakes are promising fillers blended with polymer to develop high‐performance TCAs. However, achieving corresponding TCAs with thermal conductivity over 10 W m−1 K−1 at filler content below 30 vol% remains challenging so far. This longstanding bottleneck is mainly attributed to the fact that most current metal nanoflakes are prepared by “bottom‐up” processes (e.g., solution‐based chemical synthesis) and inevitably contain lattice defects or impurities, resulting in lower intrinsic thermal conductivities, only 20–65% of the theoretical value. Here, a “top‐down” strategy by splitting highly purified Ag foil with nanoscale thickness is adopted to prepare 2D Ag nanoflakes with an intrinsic thermal conductivity of 398.2 W m−1 K−1, reaching 93% of the theoretical value. After directly blending with epoxy, the resultant Ag/epoxy exhibits a thermal conductivity of 15.1 W m−1 K−1 at low filler content of 18.6 vol%. Additionally, in practical microelectronic cooling performance evaluations, the interfacial heat‐transfer efficiency of the Ag/epoxy achieves ≈1.4 times that of the state‐of‐the‐art commercial TCA.

Metrics & MoreArticle Recommendations I t has come to our attention that the scale bar in Figure 1d is mislabeled. To avoid misunderstanding by readers, we have made a revision, with the corrected Figure 1d included here. Except for Figure 1d, the other panels in Figure 1 are unchanged. This correction does not require any additional changes to the Article text and also does not change the conclusions of the work. The authors sincerely apologize for the error.