Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 13: POSTER New Experimental Techniques
CPP 13.12: Poster
Dienstag, 28. März 2006, 17:00–19:00, P3
Interfacial strength of the contacts between glass spheres and a solid surface investigated by torsional and thickness-shear quartz resonators — •Binyang Du, Alexander Martin König, and Diethelm Johannsmann — Institute of Physical Chemistry, Clausthal University of Technology,Arnold-Sommerfeld-Str. 4, 38678 Clausthal-Zellerfeld
A torsional quartz resonator and a thickness-shear quartz resonator were used to study the interaction between a monolayer of glass spheres and the resonator surface. The glass sphere induces a negative or a positive frequency shift, depending on the mass of the sphere ms, the spring constant of the sphere-plate contact, κs, and the frequency of the resonator ω. This behaviour can be explained by the ”Mass-Spring-Model”. [1] The sphere is considered as a second small resonator with a resonance frequency ωs = (κs/ms)1/2. For ωs≫ω, the spheres are rigidly attached to the crystal and behave like a Sauerbrey film. The frequency shift is negative. In the opposing limit of ωs≪ω, inertia holds the spheres in place. The sphere-plate contact increases the overall stiffness of the composite resonator and therefore increases the resonance frequency in proportion to the spring constant. Employing both thickness-shear resonators and torsional resonators and varying the sphere size, different regimes were mapped out. Interestingly, varying humidity of the environment changes κs as well as ωs, leading to a cross-over from positive frequency shift to negative frequency shift. The results indicate that quartz resonators can probe interfacial capillary aging.
[1] G. L. Dybwad, Journal of Applied Physics 58, 2789 (1985)