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CPP: Chemische Physik und Polymerphysik

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

CPP 12.21: Poster

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

Brillouin and ultrasonic study of the gelation of ringing silica gels — •Benjamin Dönigus, Andreas Köhler, Oliver Meseth, and Rudolf Feile — Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 8, 64289 Darmstadt

Ringing gels are distinguished from other gels by a strong acoustic emission of sound waves excited by knocking onto the containers they were prepared in /1/. Brillouin and ultrasonic experiments were performed on the influence of the microscopic network formation on the elastic properties of the bulk gel during the gelation and further aging process. We find a reduction of the speed of sound when the gelation proceeds. The decrease of the sound velocity is compared with existing theoretical predictions /2,3/. Additionally, both experimental methods indicate a two-step process in the gelation.

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

/2/ M.A. Biot, J. Acoust. Soc. Am. 28, 168 (1956); 28, 179 (1956); J. Appl. Phys. 33,1482 (1962)

/3/ D. L. Johnson, J.Chem.Phys. 77,1531-1539 (1982)