Dresden 2006 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 12: POSTER Colloids, Nanoparticles and Self-Organizing Systems

CPP 12.20: Poster

Dienstag, 28. März 2006, 17:00–19:00, P3

Experimental and theoretical investigation of vibrational modes in ringing gels — •Erik Järmstorp, Barbara Drossel, and Rudolf Feile — Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr., 64289 Darmstadt

Ringing gels exhibit a strong acoustic emission of sound waves when they are excited by knocking onto the containers they were prepared in. This distinguishes them from other gels, which do not show this ringing sound. To start a detailed investigation of the physical basis of the phenomenon we have investigated the vibrational modes of silica gels which show this ringing behaviour. Experimentally, we have developed a non-contact method using the reflection of a laser beam to study the oscillatory motion of the gel surface within a cylindrical container. This method allows a clear separation of gel modes from other acoustic emissions caused by the specific excitation process (knocking) and the experimental set-up which was not possible in former experiments /1/. We were also able to study the time development of the gelation process. Theoretically, we solved the wave equation of motion for vector displacements of volume elements according to the boundary conditions for the experimental set-up in cylindrical symmetry. The results are compared with a scalar ansatz presented in /1/, and are discussed in respect to the experimental results. The results from the gelation experiments are compared with different models for the microscopic processes involved in the gelation.

/1/ C. Sinn, J. Non-Cryst. Solids 347, 11-17 (2004)