Facile preparation of graphite particles fully coated with thin Ag shell layers for high performance conducting and electromagnetic shielding composite materials

Abstract

We have demonstrated a facile surface-functionalization method to achieve a high density of thiol groups on natural graphite particles (NGPs), which facilitates the fabrication of compact silver shells of about 50 nm in thickness on the surface of NGPs by electroless silver plating. In our protocol, the addition of water and ammonia in the modification not only promotes the condensation of free hydrolyzed 3-mercaptopropyltrimethoxysilane (MPTMS) molecules with the hydroxyl groups on NGPs, but also enhances their self-polymerization due to MPTMS being grafted on the NGPs. In this way, simply optimizing the volume ratio of H₂O to MPTMS (V_H2O : V_MPTMS) in the modification can make the density of thiol groups (N_SH) on the surface of NGPs to be as high as ∼52 –SH groups per nm², which subsequently produces thin and compact silver shells on NGPs by creating dense Ag nuclei. Compared with the previously reported silver-coated non-metallic core–shell composite particles, the as-synthesized NG@Ag core–shell composite particles (NG@Ag CSCPs) show a high conductivity of 1.71 × 10⁶ S m⁻¹ even when the Ag content is as low as 32 wt%, implying the advantages of low density, high thermal stability and low cost. The polymer-based composite materials based on them exhibit excellent conductivity, strong shielding effectiveness and good anti-sedimentation, as well as good mechanical properties, conducting stability and small filling volume percentage, suggesting that the as-synthesized NG@Ag CSCPs are promising materials for applications in conductive and electromagnetic shielding composite materials.