Synthesis of Hard Carbon/Iron Microspheres and Their Aqueous-Based Tribological Performance Under Magnetic Field

We present a tribological investigation of hard carbon/iron microspheres (HC/Fe_μspheres) which were prepared by hydrothermal reaction. The formation of HC/Fe_μspheres is studied by micrographs and chemical analysis. A series of ball on disk tribological tests are carried out on a universal materials tester. Results show that adding HC/Fe_μspheres aqueous dispersion in magnetic field can significantly reduce the friction coefficient between the two friction surfaces. In addition, the relationship between friction coefficient and particle size, sliding speed is addressed. It is proposed that the magnet placed at the upper friction pairs helps to gather the HC/Fe_μspheres at the contact area during the friction test and maintain a stable friction coefficient when loading from 0.1 to 4.7 N. We demonstrate a novel application of magnetic particles as aqueous lubricants with a potential to tune the coefficient of friction by changing external magnetic field.