Alexandra Teleki, Department of Mechanical and Process Engineering, Swiss Federal Institute of Technology Zurich, Particle Technology Laboratory, Sonneggstrasse 3, Zurich, CH-8092, Switzerland, Robert Wengeler, Institut für Mechanische Verfahrenstechnik und Mechanik, Universität Karlsruhe (TH), Karlsruhe, 76128, Germany, Hermann Nirschl, Chemical and Process Engineering, University of Karlsruhe, Institute for Mechanical Process Engineering and Mechanics, Strasse am Forum 8, Karlsruhe 76131, Germany, and Sotiris E. Pratsinis, Particle Technology Laboratory, Institute of Process Engineering, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, Zurich, CH-8092, Switzerland.
The potential of high pressure dispersion (HPD) and dynamic light scattering (DLS) is explored [1] for rapid and quantitative estimation of the extent of particle aggregation and agglomeration by analyzing the entire particle size distribution [2]. Commercially available and tailor-made TiO
2 particles by flame spray pyrolysis (FSP) were characterized by X-ray diffraction, nitrogen adsorption and transmission electron microscopy (TEM). Volume distributions of these particles were obtained by DLS of their electrostatically stabilized (with Na
4P
2O
7) aqueous suspensions. Dispersing these suspensions through a nozzle at 200 to 1400 bar reduced the size of agglomerates (particles bonded by weak physical forces) resulting in bimodal size distributions composed of their constituent primary particles and aggregates (particles bonded by strong chemical or sinter forces). Sintering FSP-made titania particles from 200 to 800 °C for four hours progressively increased the minimum primary particle size (by grain growth) and aggregate size (by neck growth and phase transformation).
[1] Wengeler, R., A. Teleki, M. Vetter, S.E. Pratsinis, and H. Nirschl, “High pressure liquid dispersion and fragmentation of flame-made silica agglomerates,” Langmuir 22, 4928-4935 (2006).
[2] Teleki, A., R. Wengeler, L. Wengeler, H. Nirschl, and S.E. Pratsinis, “Distinguishing between aggregates and agglomerates of flame-made TiO2 by high pressure dispersion,” Powder Technol. 181, 292-300 (2008).