Submicron-Lubricant Based on Crystallized Fe3O4 Spheres for Enhanced Tribology Performance

We demonstrate in this paper a novel finding of submicron-lubricant exemplified by crystallized magnetite (Fe3O4) submicrometer spheres. Optimized tribological performance of lubricant particles occurs when the particles are submicrometer sized and spherical. The tribology of lubricant particles is thus verified to be size and shape dependent. Owing to the unique heating and quenching process involved in pulsed laser irradiation, Fe3O4 submicrometer spheres are acquired through phase transformation and reshaping. The formation process of the regular Fe3O4 spheres in deionized water was investigated by choosing different laser fluences and irradiation times. The shape and phase transformation mechanisms are elucidated as well. Tribological properties of the obtained Fe3O4 submicrometer spheres have been explored, inspired by their spherical shape and smooth surfaces. Crystallized magnetite submicrometer spheres under optimized conditions show a reduction in friction and wear by up to 40% and 20%, respectively. Control experiments revealed that nanoparticles, nonspherical submicrometer particles, and micrometer particles could not reach such good tribology performance, indicating the potential of adopting crystallized Fe3O4 submicrometer spheres in the application of mechanical energy saving.