| AVS 61st International Symposium & Exhibition | |
| Fundamentals & Biological, Energy and Environmental Applications of Quartz Crystal Microbalance Focus Topic | Thursday Sessions |
| Session QC+AS+BI+MN-ThM |
| Session: | Fundamentals and Method Development of QCM |
| Presenter: | Boray Torun, University of Paderborn, Germany |
| Authors: | B. Torun, University of Paderborn, Germany C. Kunze, University of Paderborn, Germany C. Zhang, Johannes Gutenberg University Mainz, Germany T.D. Kühne, Johannes Gutenberg University Mainz, Germany G. Grundmeier, University of Paderborn, Germany |
| Correspondent: | Click to Email |
During the past decade nanoparticles attracted a great deal of attention and found many applications in various fields ranging from pigments and antibacterial agents to highly effective catalysts. In this context, the handling and processing of nanoparticle powders play an important role. In contrast to macroscopic particles, nanoparticle flow properties are manly governed by the particle-particle interactions. The forces determining these interactions strongly vary not only with the material properties but also with surface chemical composition as well as the environmental conditions. Hence, a fundamental understanding of the processes and forces involved plays a key role for the prediction of nanoparticle powder behavior.
In the presented study [1], water adsorption and capillary bridge formation within a defined layer of SiO2 nanoparticles was studied by means of a novel in-situ analytical setup allowing for combined quartz crystal microbalance with dissipation analysis (QCM-D) and Fourier transformation infrared reflection absorption spectroscopy (FT‑IRRAS). On the one hand, the QCM-D gave insights on both, mass change (Δf) and changes in the contact mechanics, indicated by dissipation changes (ΔΓ), whereas on the other hand FT-IRRAS allowed for the characterization of the adsorbed water structure. Employing peak deconvolution to the OH-signal in the region of 3400 cm-1, “ice-like” and “liquid-like” water structures could be clearly identified.
Combined measurements show that for a monolayer of monodisperse SiO2 particles with a diameter of about 250 nm the adsorption of water leads to a linear increase in dissipation for relative humidity (RH) values up to 60%. Subsequently, the strong increase in dissipation between 60% and 80% RH was attributed to the actual liquid bridge formation. This result was supported by the predominant growth of “liquid-like” water during the bridge formation phase indicated by the corresponding FT-IR data. Furthermore, for RH>90% a decrease in dissipation was detected indicating the merging of capillaries and the onset of a water film formation. Overall, our results indicate that combined in-situ QCM-D and FT-IRRAS analysis enables the qualitative and quantitative analysis of water adsorption and capillary bridge formation in particle layers.
[1] Torun, B. et al., Phys. Chem. Chem. Phys., 2014, 16, 7377-7384