Ionic liquid stabilized Ag@C composite for improvement of triboactivity

Abstract

Abstract Synthesis of carbon spheres and their composite Ag@C was accomplished by the hydrothermal method. The composite Ag@C was stabilized by the ionic liquid, 1-decyl 3-methyl imidazolium boron tetrafluoride (DMIM BF4) to yield (IL-Ag@C). The Fourier Transform Infrared(FT-IR) spectra approved the formation of composites. The powder XRD patterns of the composites matched with JCPDS files. Examination of morphological characteristics of Ag@C by scanning electron microscopy/high-resolution scanning electron microscopy(SEM/HR-SEM), transmission electron microscopy/high-resolution transmission electron microscopy(TEM/HR-TEM) revealed spherical nanoparticles of about 30–40 nm size embedded on carbon spheres of 1.2–1.6 μm. Upon addition of ionic liquid, the composite appears to be wrapped in it. Energy-dispersive X-ray(EDX) analysis associated with SEM exhibited the presence of additional elements of ionic liquid, fluorine and nitrogen, besides silver and carbon in IL-Ag@C confirming its formation. The binding energy data obtained from X-ray photoelectron spectroscopy (XPS) corroborated the formation of IL-Ag@C. Triboactivity of the carbon nanospheres and the composites were assessed in base lube PEG-200 at 0.5% w/v concentration on a four-ball tester under ASTM D4172 and ASTM D5183 conditions. Based on tribological data namely coefficient of friction(COF), mean wear scar diameter(MWD), load-carrying capacity and loss of frictional power, the relative order of activity of different additives could be established as: IL − Ag @ C > Ag @ C > IL > C spheres > PEG − 200 The above order was authenticated by morphological studies of the wear scar by SEM and AFM(Atomic Force Microscopy) techniques. The EDX analysis of the wear scar surface lubricated with IL-Ag@C showed iron also in addition to the constituent elements of the composite. Thus, active participation of the adsorbed additive towards tribofilm formation is validated. The XPS studies of the same surface, further confirm the presence of boron nitride, boron carbide along with iron oxide. These boron compounds have, indeed, enriched the tribofilm for improved triboactivity.