Polymer tribology by combining ion implantation and radionuclide tracing

Radionuclide tracers were ion implanted with three different techniques into the ultra-high molecular weight polyethylene polymer. Tracer nuclei of ⁷Be were produced with inverse kinematics via the reaction p(⁷Li,⁷Be)n and caught by polymer samples at a forward scattering angle with a maximum implantation energy of 16 MeV. For the first time, ⁹⁷Ru, ¹⁰⁰Pd, and, independently, ¹¹¹In have been used as radionuclide tracers in ultra-high molecular weight polyethylene. ⁹⁷Ru and ¹⁰⁰Pd were recoil-implanted following the fusion evaporation reactions ⁹²Zr(¹²C,α3n) ⁹⁷Ru and ⁹²Zr(¹²C,4n)¹⁰⁰Pd with a maximum implantation energy of 8 MeV. ¹¹¹In ions were produced in an ion source, mass-separated and implanted at 160 keV. The tribology of implanted polymer samples was studied by tracing the radionuclide during mechanical wear. Uni-directional and bi-directional sliding apparatus with stainless steel actuators were used. Results suggest a debris exchange process as the characteristic feature of the wear-in phase. This process can establish the steady state required for a subsequently constant wear rate in agreement with Archard's equation. The nano-scale implantation of mass-separated ¹¹¹In appears best suited to the study of non-linear tribological processes during wear-in. Such non-linear processes may be expected to be important in micro- and nanomachines.