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Research Article

High-Pressure Liquid Dispersion and Fragmentation of Flame-Made Silica Agglomerates

Robert Wengeler,^† Alexandra Teleki,^‡ Markus Vetter,^†^‡ Sotiris E. Pratsinis,^‡ and Hermann Nirschl*^†

Institute for Mechanical Process Engineering and Mechanics, Universitt Karlsruhe (TH), D-76128 Karlsruhe, Germany, and Particle Technology Laboratory, Department of Mechanical and Process Engineering, ETH Zrich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland

Langmuir, 2006, 22 (11), pp 4928–4935

DOI: 10.1021/la053283n

Publication Date (Web): April 18, 2006

†

Universität Karlsruhe (TH).

‡

ETH Zürich.

Corresponding author. Address: Universität Karlsruhe (TH), 76128 Karlsruhe, Germany. Phone: +49 (721) 608 2400. Fax: +49 (721) 608 2405. E-mail: Hermann.nirschl@mvm.uni-karlsruhe.de.

Abstract

The influence of primary particle diameter and the degree of agglomeration of flame-made silica agglomerate suspensions in aqueous solutions is studied by high-pressure dispersion (up to 1500 bar) through a nozzle with a 125 μm inner diameter. These particles were produced (4−15 g/h) by oxidation of hexamethyldisiloxane (HMDSO) in a coflow diffusion flame reactor. Their average primary particle size (10−50 nm) and degree of agglomeration were controlled by varying the oxygen and precursor flow rates. The particles were characterized by nitrogen adsorption, electron microscopy, and small-angle X-ray scattering. Hydrodynamic stresses break up soft agglomerates and yield hard agglomerate sizes in the range of 100−180 nm, as characterized by dynamic light scattering. Soft agglomerates exhibited decreasing light scattering diameters with increasing dispersion pressure, while hard agglomerates were insensitive.

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