Rapid Microwave Synthesis of SiO2@C/Graphite Nanocomposites as Water-Based Lubricant Additives

Abstract

Rapid construction of stable zero-dimensional/two-dimensional (0D/2D) lubricant additives remains challenging because exposed inorganic nanoparticles can agglomerate or separate from layered supports under shear. Here, a SiO2@C/graphite (SiO2@C/G) nanocomposite was prepared by a 2 min microwave treatment of SiO2 nanoparticles, naphthalene, and graphite. In this composite, carbon-coated SiO2 nanoparticles are anchored on and partially intercalated between graphite sheets, forming a plate-sphere-plate architecture. At 1.0 wt % in water, SiO2@C/G reduced the coefficient of friction from 0.74 for water to 0.12 and the wear rate from 4.40 × 10−4 to 0.39 × 10−4 mm3 N−1 m−1. Relative to a microwave-treated SiO2/graphite (SiO2/G) dispersion, the friction coefficient and wear rate decreased by 29.4% and 86.3%, respectively. Worn surface microscopy and elemental mapping indicate that by inhibiting SiO2 delamination, the carbon shell facilitates the synergistic co-transfer of the composite spheres and graphite sheets into the contact zone. The performance is attributed to interfacial conversion from direct SiO2/G contact to a carbon-shell/graphite interface together with rolling-sliding cooperation between the coated spheres and graphite sheets. This work provides a rapid route to carbon-coated 0D/2D nanocomposites for water-based tribological applications.