Nanohybrid Cu@C: synthesis, characterization and application in enhancement of lubricity

Abstract

ABSTRACT Carbon nanospheres, copper nanoparticles and their composite Cu@C having copper nanoparticles embedded in carbonaceous material were synthesized hydrothermally. The analytical techniques; powder X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM) with energy-dispersive X-ray spectroscopy(EDX), transmission electron microscopy/high- resolution transmission electron microscopy(TEM/HR-TEM), Raman and X-ray photoelectron spectroscopy (XPS) have been employed for their characterization. Tribological behavior of blends of the synthesized additives with paraffin oil has been investigated on a four-ball lubricant tester using ASTM D4172 and ASTM D5183 at 0.1% w/v concentration. Comparative activity of the base oil and the blends has been adjudicated considering the experimental data for mean wear scar diameter (MWD), coefficient of friction (COF), load-carrying capacity and wear rates collected from the above standard tests. The admixture-containing nanohybrid, Cu@C appears to show the best activity followed by that of copper nanoparticles and then carbon spheres. The relative activity of different admixtures is verified by atomic force microscopy(AFM) and scanning electron microscopy(SEM) with EDX results of the wear pathway. The EDX spectrum of Cu@C shows the existence of copper together with carbon on the wear scar surface confirming their contribution in the formation of in situ tribofilm. Thus, these additives may be approved for enhancing lubrication.