Electroacoustic and Acoustic Attenuation Spectroscopy as New Tools for In Situ-Monitoring of Metal Oxide Precursor Preparation in Liquid Phase

Abstract

The in situ-monitoring of a solid synthesis was realised by electroacoustic and acoustic attenuation spectroscopy. These techniques were applied to track the crystal growth of alumina precursor nanoparticles used as model compound. A commercially available set-up with a circular flow detector cell for joint electroacoustic and attenuation measurements was used. Course of zeta potential as well as particle growth was measured during continuous hydrolysis of dry Al-sec-butoxide in isopropanol. Zeta potential shows minima and maxima with increasing water amount, whereas particles start to grow significantly after a defined time of operation. In some experiments the synthesis was stopped ahead of time and the formed solids were additionally studied ex situ by characterisation methods such as solid-state NMR or transmission electron microscopy. Measured ultrasound data can be correlated to elemental processes during particle formation. First experiments on monitoring of synthesis scale-up show potential for future application of this technique.