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CPP: Chemische Physik und Polymerphysik

CPP 15: POSTER: Polymers and Biomaterials

CPP 15.25: Poster

Dienstag, 9. März 2004, 17:00–19:00, B

High frequency microtribology of polymer thin films with quartz crystal resonators — •Binyang Du and Diethelm Johannsmann — Institute of Physical Chemistry, Technical University Clausthal,Arnold-Sommerfeld-Str. 4, 38678 Clausthal-Zellerfeld, Germany

In present experiments, quartz crystal resonators coated with a polystyrene film in contact with a ceramic sphere have been used to study the micro scale tribology at high frequency (15MHz)and a shear amplitude in the nanometer range. The experiment is based on the ring-down of the resonator, where the electrical excitation is periodically interrupted and the free decay of the oscillation is analyzed. When a small ceramic sphere is put onto the center of quartz surface, the shear motion of the quartz is perturbed due to the external stress of sphere, which can be used to study force ∼ displacement and force ∼ speed relations in the contact zone. A nonlinear spring constant κ (x) and a nonlinear friction coefficient ξ (ẋ) are explicitly derived. Two transitions are observed with increasing shear amplitude, one is from stick-to-partial slip and the other is from partial slip to-total slip. The nonlinear spring constant is in good agreement with the microslip model, which indicates a maximum lateral force and diverges in the transition of partial slip to total slip. The friction force depends linearly on lateral speed in the partial slip region and nonlinearly in total slip region, respectively.