Thermal Conductive Network Construction and Enhanced Thermal Conductivity in Mica Tape Composites for Large Generators by Pre-Placed h-BN@PDA-Modified Mica Paper

Abstract

The lower thermal conductivity (TC) of mica tape hinders the evolution of large generators towards higher voltage and capacity. To enhance the TC of the mica tape, with the help of the three-dimensional (3D) multi-layer framework of the mica paper, a 3D polydopamine-coated boron nitride (h-BN@PDA) TC network was constructed by pre-placing h-BN@PDA inside the mica paper. Additionally, the above mica paper and epoxy-impregnated glass fabric were pressed to manufacture mica tape composites. Although the h-BN percentage remained constant, the TC of the h-BN@PDA/mica paper (or tape) composites could be further enhanced by depositing PDA over the h-BN surface. The TC of the 25wt.% h-BN@PDA/mica paper and mica tape composites reached 1.12 and 0.435 W/(m·K), which were 169.23% and 83.5% in comparison to pure mica paper and mica tape, respectively, also higher than those of the 25wt.% h-BN/mica paper and mica tape composites (1.07 and 0.416 W/(m·K), respectively). As calculated from theoretical modelling, this enhancement is due to the ability of the PDA coating to act as a ‘bridge’ to reduce the interfacial thermal resistance (ITR). In conclusion, the 3D TC network construction method in this research offers a new concept and strategy for manufacturing high-TC mica tapes.