Magnetic field-induced alignment of nickel-coated copper nanowires in epoxy composites for highly thermal conductivity with low filler loading

Abstract In this work, the large-scale produced copper nanowires (Cu NWs) were coated by nickel nanoparticles (Ni NPs) lay, i.e., Cu NWs@Ni. And under external magnetic field condition, Cu NWs@Ni as thermally conductive fillers were filled into epoxy (EP) resin to prepare the composites with high thermal conductivity (TC). The results showed that, when the magnetic field was 80 mT, Cu NWs@Ni (molar ratio of Cu:Ni = 10:5, and saturation magnetization (Ms) = 20.3 emu/g) can distribute in EP resin in an orderly manner along the direction of the magnetic field, endowing the composite with excellent TC at lower loading. Especially, when only 9 vol.% Cu NWs@Ni was filled, the TC along the direction of the magnetic field can reach 2.90 W/mK, which was 12.81 times than that of neat EP resin. Even so, the composite still maintained outstanding insulation properties, namely, the volume resistivity and the dielectric strength were 1.79 × 1015 Ω cm and 12.88 kV/mm, respectively. In addition, compared to that of neat EP resin, the composite still possessed splendid heat stability and mechanical properties. For the above positive improvement, the corresponding mechanisms were also discussed in detail.