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 (7)Be were produced with inverse kinematics via the reaction p((7)Li,(7)Be)n and caught by polymer samples at a forward scattering angle with a maximum implantation energy of 16 MeV. For the first time, (97)Ru, (100)Pd, and, independently, (111)In have been used as radionuclide tracers in ultra-high molecular weight polyethylene. (97)Ru and (100)Pd were recoil-implanted following the fusion evaporation reactions (92)Zr((12)C,alpha 3n) (97)Ru and (92)Zr((12)C,4n)(100)Pd with a maximum implantation energy of 8 MeV. (111)In 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 (111)In 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. (C) 2010 Elsevier B.V. All rights reserved