Tribological properties of nitrogen, carbon and titanium ion implanted PET against steel

A 25 μm thickness polyethylene terephthalate (PET) film was implanted with 120 keV ions of nitrogen, carbon, and titanium to doses of 1 × 10¹⁴, 1 × 10¹⁵, 5 × 10¹⁵ and 1 × 10¹⁶ ions cm^-2, respectively. The structure of the implanted PET was characterized by X-ray photoelectron spectroscopy (XPS), and the friction and wear behaviors of both implanted and unimplanted PET were investigated using a one-way reciprocating friction tester against a steel ball. Results indicate that ion implantation at a dose of 1 × 10¹⁵ ions cm^-2 increased the friction coefficient, whereas the carbon ion implantation at a dose of 1 × 10¹⁶ ions cm^-2 decreased the friction coefficient. All the tests showed that ion implantation lowered the wear rate, other than carbon ion implantation at a dose of 1 × 10¹⁶ ions cm^-2. XPS analysis revealed the break of C=O and C-O bonds and the formation of C-N bonds during the process of nitrogen and carbon ion implantation; however, titanium was not detected by XPS after the implantation.