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The developments in the high-power densities and high integration of electronic devices have put forward higher requirements for advanced thermal management materials (TMMs) to meet the rising demand for heat dissipation. However, it has remained a major challenge to achieve significant enhancement of thermal conductivity (TC) of TMMs without compromising their mechanical and dielectric properties. Here, we report a flexible, thermally conductive composite film that contain aramid nanofiber (ANF) and silver nanoparticles (AgNPs) decorated with boron nitride (BN), the in-plane TC of which is up to 12 W/mK at 40 wt.% filler contents. Such a high TC is attributed to the bridging role of AgNPs, which greatly reduces the interfacial thermal resistance of composites. At the same time, the as-prepared composite films possess outstanding mechanical strength (>126 MPa), owing to the coupling between the ANF network and the favourable hydrogen bonding interaction between the ANF and the functional BN. Moreover, a low dielectric loss (<0.05), high electrical resistivity (~1014 Ω·cm), and high decomposition temperature (>500°C) are simultaneously achieved for the composite films. These findings offer a facile strategy for the design of multifunctional TMMs, which hold great promising for application in electric devices. [ABSTRACT FROM AUTHOR]

Polymer-based dielectric films with desirable heat dissipation property hold great promise as thermal management materials in advanced electronics and high power devices. Herein, we report a new strategy for preparing thermally conductive films by synergistically combining one-dimensional (1D) aramid nanofiber (ANF) with 2D edge-hydroxylated boron nitride nanosheet (OH-BNNS) via a vacuum-assisted self-assembly technique. The obtained ANF/OH-BNNS film exhibits an ultrahigh in-plane thermal conductivity of 32.3 W m−1K−1 at 40 wt% BNNS-OH loading, which is 3530% greater than that of the pure ANF film. The excellent thermal conductivity results from the special 'brick-and-mortar' layered structure of ANF/OH-BNNS, in which the increased contacting and overlapping of OH-BNNS promotes the formation of the thermal conduction pathways. In addition, the rigid ANFs act as bridges linking OH-BNNS by favorable hydrogen bonding interactions, which efficiently enhance phonon propagation and stress transfer in the film. Moreover, the ANF/OH-BNNS film simultaneously shows low dielectric loss (~0.03), high tensile strength (~88 MPa), and a high decomposition temperature (>510 °C). We believe that these findings are of great importance for the fabrication and practical application of thermal management materials in high-temperature electronics and devices. [ABSTRACT FROM AUTHOR]