Impedance spectroscopy has a high potential to detect chemical reactions in flowing systems. In this work, the approach using impedance spectroscopy as a possible analytical tool for a continuous hydrothermal syntheses (CHTS) is presented. With the CHTS-process, it is possible to produce metalloxide nanoparticles with a close particle size distribution and specific surface properties. For this, it is necessary to evaluate the electrode geometry, frequency and other factors influencing the impedance with respect to concentration measurements. In case of frequency-sweep measurements possible electrode geometries for C4D-Sensors (capacitively coupled contactless conductivity detection) are evaluated. Then distinguishability and reproducibility are tested applying titration measurements to show the ability for concentration detection in constant flow systems. The possibility to measure concentration changes in flowing systems in a reproducible and fast manner as well as with high distinguishability for the test solution cerium nitrate will be presented. Furthermore, the major influencing-factors like electrode geometry, frequency etc. could be determined. It has been shown that with increasing electrode spacing and electrode width, the distinguishability of the concentrations increases and shifts them to lower frequencies.
Die kontinuierliche hydrothermale Synthese (CHTS) stellt ein vielversprechendes Verfahren zur Herstellung metalloxidischer Nanopartikel dar. Das Prinzip beruht auf der Vermischung einer kalten wa ¨ssrigen Metallsalzlo ¨sung mit einem nahe-/u ¨berkritischen Wasserstrom. Durch die außergewo ¨hnlichen Eigenschaften des u ¨berkritischen Wassers kommt es zur Partikelbildung. Neben der Studie des Einflusses der Prozessparameter auf die resultierende Partikelgro ¨ße und -verteilung ist die Restkonzentration an gelo ¨stem Metallsalz von Interesse. Diese kann mittels der Impedanzspektroskopie analysiert werden. Dazu werden an einer modifizierten CHTS-Anlage Vorversuche durchgefu ¨hrt, um zuku ¨nftig die Restkonzentration direkt bestimmen zu ko ¨nnen.
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