Project Details
Projekt
Molecular UHV-FTIR studies of adsorbate covered TiO2-microparticle surfaces
Applicant
Professor Dr.-Ing. Guido Grundmeier
Subject Area
Mechanical Process Engineering
Term
from 2010 to 2017
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 169597163
The project aims at the study of contact forces between particles and oxidic substrates based on the molecular control of the adsorbate structure concerning the orientation, thickness and mobility via AFM based and spectroscopic techniques. As model systems, SiO2 and TiO2 will be used as their surface modification is of high interest for the flow properties of particle powders. The methodology is based on the hypothesis that ultrahigh vacuum (UHV) and also clean liquid phases allow for the adjustment of the interfacial chemistry of particles without the influence of environmental contaminations. Furthermore the AFM colloidal probe technique as a force analytical method allows in both media the quantification of the influence of this interface structure on the interaction in the contact zone of the particles. As organic adsorbates organophosphonic acids will be used, as they are of large interest for the tailoring of surface properties of the considered particles and enable the preparation of monolayers of different ordering and chemical functionality. The adsorption of water on bare or chemically modified surfaces is done at the interface to ultrahigh vacuum or an organic liquid phase. The UHV analytical setup includes an X-ray photoelectron spectrometer (XPS) for the analysis of the adsorbate chemistry and an UHV-AFM which allows the measurement of contact forces on bare and adsorbate covered surfaces. A particular interest is the mobility and ordering of the adsorbate layers as a function of the chemical properties and temperature. By means of atmospheric AFM the formation of capillary bridges and their influence on contact forces as a function of surface chemistry and temperature is investigated. To avoid the influence of atmospheric adsorbates, the experiments will be performed in an apolar, organic phase with a controlled activity of water. Hence at hydrophilic interfaces different amounts of water will be available for the temperature dependent interaction involving ice-like water layers of capillary bridges. Via in-situ FTIR spectroscopy and in-situ surface plasmon resonance these water layers will be characterized concerning their thickness and structure.
DFG Programme
Priority Programmes
