Abstract:With the gradual development of power equipment towards high voltage, large capacity, and high integration, higher requirements have been put forward for the insulation materials of its thermal conductivity. This article drew inspiration from the biomimetic structure of the natural pearl. The composite insulation paper was constructed by using the one-dimensional aramid nanofibers (ANF) with high-temperature resistance as the skeleton network, and the two-dimensional boron nitride nanosheets (BNNS) with high thermal conductivity as the functional units. Firstly, the lithium citrate was used as a surfactant to peel hexagonal boron nitride (h-BN) into BNNS through a combination of ultrasound and hydrothermal reaction. Its microstructure and dispersion characteristics were also studied. Then, the concentrated alkali deprotonation method was used to peel the Kevlar fiber (AF) into ANF. Using ANF and BNNS as nanocomposites, the BNNS/ANF composite insulation paper was prepared through the vacuum assisted filtration technology. Its microstructure, thermal conductivity, mechanical properties, and breakdown performance were further analyzed. The results show that the thin layer BNNS prepared by peeling has a high aspect ratio, and the uniform accumulation between BNNS and ANF forms a dense brick mud structure. This brick mud structure helps to improve the breakdown performance and mechanical properties of the composite insulation paper. When the filling mass fraction of BNNS is 20%, the standard breakdown field strength of the BNNS/ANF composite insulation paper reaches 313.04 kV/mm, and its tensile strength reaches 216.64 MPa, which are 166.47% and 126.38% of the corresponding parameters of the pure ANF insulation paper, respectively. In addition, the directional distribution of BNNS in the ANF network forms a continuous thermal conductivity bridge, which significantly improving the thermal conductivity of the composite insulation paper. When the filling mass fraction of BNNS is 30%, the thermal conductivity of the composite insulation paper reaches 5.31 W/(m·K), which is 211.55% of that of the pure ANF insulation paper. Thus, the composite insulation paper has high thermal conductivity, good mechanical properties and excellent electrical insulation, which can effectively solve the problem of equipment insulation and heat dissipation. It is expected to be widely used in electrical equipment.