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DS: Fachverband Dünne Schichten
DS 22: Trends in atomic layer deposition I (Focused session – Organizer: Nielsch)
DS 22.6: Talk
Wednesday, March 28, 2012, 17:00–17:15, H 0111
Templated ALD for Synthesis of Magnetic Nanotube Suspensions — •Robert Zierold1, Zhenyu Wu2, Carl E. Krill III2, and Kornelius Nielsch1 — 1University of Hamburg — 2Ulm University
Commercial ferrofluids usually consist of spherical, superparamagnetic nanoparticles suspended in a carrier liquid. The application of an external magnetic field, however, can trigger network formation and a concomitant increase in the liquid’s viscosity—its so-called magnetoviscosity. Herein, we show how magnetic nanotubes can be prepared by ALD in porous alumina templates. In this process, the iron oxide deposited from the reaction of ferrocene with ozone is sandwiched between two silica layers (APTES, water, ozone) for protective reasons. The combination of a template, the sub-nm layer thickness control afforded by ALD, and proper adjustment of the H2 reduction parameters for the converting amorphous iron oxide to magnetite allow the experimentalist to tailor all geometric tube parameters (length, diameter, wall thickness) as well as the type of magnetism manifested by the nanotubes—superparamagnetism/ferromagnetism. Viscosity measurements performed on mixtures of commercial ferrofluids (consisting of spherical particles) with nanotubes reveal a significant enhancement in the strength of the magnetoviscous effect compared to samples without additives. The different fluid-mechanical properties of such hybrid ferrofluids might pave the way for new engineering applications.
Financial support was provided by the state of Hamburg through the Excellence Cluster "Nanotechnology in Medicine"