Fabrication of highly conducting nickel-coated graphite composite particles with low Ni content for excellent electromagnetic properties

Abstract Nickel-coated flaky graphite particles (FGP@NiCPs) have been widely employed as key fillers of electromagnetic functional composites. However, the existing such fillers suffer from disadvantages of uncompacted shells, unsatisfactory conductivity or high nickel content, making it hard to meet high requirements for electronic connection and electromagnetic compatibility. Herein, we have demonstrated an efficient approach to achieving sufficiently heterogeneous nucleation coupled with electroless Ni plating to fabricate highly conducting FGP@NiCPs with low Ni content for excellent electromagnetic properties of polymer-matrix composites. Preparation of the typical FGP@NiCPs consists of rinsing flaky graphite particles (FGPs), adsorbing nickel ions, in-situ reduction into nickel nuclei and electroless Ni plating. On the one side, the hydrophilicity of FGPs can be improved by soxhlet extraction. This is one of important factors to adsorb more nickel ions on FGPs because they can be uniformly dispersed or fully exposed to NiSO4 solution. On the other side, the rinsed FGPs are immersed into a high concentration ([NiSO4]) solution, which facilitates to further adsorb enough nickel ions through electrostatic attraction. Subsequently, these nickel ions adsorbed on FGPs are in-situ reduced into a lot of nickel nuclei, indicating that increasing hydrophilicity and immersing into a high [NiSO4] for FGPs synergistically favor heterogeneous nucleation burst. Finally, low content nickel densely-coated FGPs composite particles are successfully synthesized by controllable electroless Ni plating. As-obtained FGP@NiCPs exhibit dense shells, low Ni content and excellent electrical conductivity compared to the commercial FGP@NiCPs (CFGP@NiCPs). Furthermore, shielding effectiveness of composites containing the typical FGP@NiCPs is between 28.0 and 35.2 dB with frequency of electromagnetic wave ranging from 30 to 1500 MHz, and stronger than that of composites containing CFGP@NiCPs, owing to the relatively high electrical conductivity. Consequently, this work holds a promising potential for electromagnetic functional polymer-matrix composites.