No abstract

A non-destructive chloride sensitive sensor element for use in cement based porous materials is presented. The sensor element determines the activity of the free chloride ions in solutions and in porous cement based materials such as cement paste, mortar or concrete. The calibration in synthetic pore solution showed a response according to Nernst law over three decades of chloride concentration. The sensor element has shown excellent reproducibility and long term stability. The sensor element has been used to monitor the chloride uptake into mortar specimens. The results show a good agreement between the free chloride content determined by the sensor and by pore water expression. Applications in monitoring of reinforced concrete structures and their limitations are discussed.In der vorliegenden Arbeit wird ein Chloridsensor zur zerstörungsfreien Erfassung des Chloridgehalts in zementösen Materialien beschrieben. Der Sensor bestimmt die Aktivität der freien Chloridionen in Lösungen und in Zementstein, Mörtel oder Beton. Die Kalibrierungskurve in synthetischer Betonporenlösung zeigt das erwartete Nernst'sche Verhalten über mehr als drei Konzentrationsdekaden. Der Sensor weist eine sehr hohe Reproduzierbarkeit und Langzeitstabilität auf. Der Chloridsensor wurde eingesetzt, um das Eindringen der Chloridionen in Mörtelprüfkörpern zu untersuchen. Ein Vergleich der Chloridkonzentration bestimmt durch Auspressen der Porenlösung am Ende der Versuche mit den von Sensoren bestimmten Chloridkonzentration zeigt eine sehr gute Ü bereinstimmung. Praktische Anwendungen und die Einsatzgrenzen des Sensors werden diskutiert. 440Elsener, Zimmermann and Böhni Materials and Corrosion 54, 440-446 (2003)

Nanocomposites of gelatine and gold were prepared by reduction of AuC1,H in a gelatine solution, followeu' by a spin coating process and a brief washing. The thickness of the films thus obtained was typically 200-400 nm. The surface of the nanocomposites was investigated by scanning electron microscopy (SEM) and surface profilometry. The size of the gold particles is in the range of ca. 2-10 nm, as elucidated by transmission electron microscopy (TEM). Refractive indices were measured by ellips o m e t y at wavelengths of 632.8 and 1300 nm. The refractive index depends linearly on the volume fraction of gold, at least at 1300 nm. The lowest refractive indices measured are 1.008_+0.060 at 1300 nm and 0.963 f 0.062 at 632.8 nm (limits are 95% confidence interval). These values are, to our best knowledge, the lowest reported for a polymer or polymer composite.

No abstract