Increasing
power density makes modern electronic devices and power
equipment generate excess heat, which greatly restricts the applications
of polymeric materials because of their poor thermal conductivity.
In the present work, inspired by the structure and production process
of millefeuille cakes, we show that electrostatic spraying of boron
nitride nanosheets (BNNSs) onto electrospun poly(vinyl alcohol) (PVA)
nanofibers can produce highly thermally conductive, electrically insulating,
flexible, and lightweight nanocomposites via a scalable method of
building a multilayer PVA/BNNS nanonetwork structure. The PVA/BNNS
nanocomposites exhibit an ultrahigh in-plane thermal conductivity
of 21.4 W/(m·K) at 22.2 vol % BNNS addition, realized by an orientated
BNNS network structure with overlapping interconnections. The BNNS
networks exhibit low thermal resistance and interfacial heat scattering
between BNNSs. Moreover, for heat dissipation applications, the nanocomposites
with an overlapping BNNS network show higher efficiency in dissipating
hot spots than randomly dispersed BNNS or directly hot-pressed BNNS
composites. These PVA/BNNS nanocomposites can be used as high-performance
lateral heat spreaders in next-generation thermal management systems.
Phase change materials (PCMs) can be used for efficient thermal energy harvesting, which has great potential for cost-effective thermal management and energy storage. However, the low intrinsic thermal conductivity of polymeric PCMs is a bottleneck for fast and efficient heat harvesting. Simultaneously, it is also a challenge to achieve a high thermal conductivity for phase change nanocomposites at low filler loading. Although constructing a three-dimensional (3D) thermally conductive network within PCMs can address these problems, the anisotropy of the 3D framework usually leads to poor thermal conductivity in the direction perpendicular to the alignment of fillers. Inspired by the interlaced structure of spider webs in nature, this study reports a new strategy for fabricating highly thermally conductive phase change composites (sw-GS/PW) with a 3D spider web (sw)-like structured graphene skeleton (GS) by hydrothermal reaction, radial freeze-casting and vacuum impregnation in paraffin wax (PW). The results show that the sw-GS hardly affected the phase transformation behavior of PW at low loading. Especially, sw-GS/PW exhibits both high cross-plane and in-plane thermal conductivity enhancements of ~ 1260% and ~ 840%, respectively, at an ultra-low filler loading of 2.25 vol.%. The thermal infrared results also demonstrate that sw-GS/PW possessed promising applications in battery thermal management.
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