Resonance Properties of Quartz Crystal Microbalance Immersed in High Solid Content Suspensions

Publication date: Available online 18 April 2019Source: Colloids and Surfaces A: Physicochemical and Engineering AspectsAuthor(s): J.A. Botha, T.N. Hunter, D. Johannsmann, D. Austin, C.S. Hodges, G.A. Mackay, S.E. Woodbury, S. Biggs, D. HarbottleAbstractThe resonance properties, frequency and half-band-half-width, of a quartz crystal microbalance (QCM) immersed in concentrated suspensions of 16.2 vol% TiO2 are shown to be a function of pH. The overall QCM response is dependent on the complex interactions between the QCM sensor and overlying particle suspension. Atomic force microscopy confirms pH dependent interaction forces between the QCM sensor (gold-coated) and a TiO2 particle: a strong attraction is measured between pH 4 – 4.5, and the interaction becomes increasingly repulsive at all pH > 6.5. Yield stress measurements of the concentrated TiO2 suspensions also confirm the changing particle-particle interaction strength as the pH is adjusted from acidic to basic conditions. For the chosen system, the total potential energy of interaction (VT) between the sensor-suspension (Au-TiO2) is comparatively stronger than the particle-particle (TiO2-TiO2) interaction; hence the QCM responds to changes in VT sensor-suspension, as verified by the calculated interaction energy between two dissimilar surfaces (Hogg-Healy-Fuerstenau (HHF) theory), and not the suspension yield stress. Slight deviation between the measured QCM responses and the theoretical sphere-plate interactio...

Source: Colloids and Surfaces A: Physicochemical and Engineering Aspects - April 19, 2019 Category: Chemistry Source Type: research