Electronic Material Properties - und Geowissenschaften ...

Corrosion
Phenomena of aqueous corrosion of metals, depending on their chemical composition,
phase and structure, are investigated by electrochemical and trace analytical methods.
The methods include potential-time and current-potential (polarization, cyclic voltammetry)
measurements, Electrochemical Noise Analysis (ENA) and Electrochemical Impedance
Spectroscopy (EIS). Immersion tests with chemical analysis of the dissolved material are
carried out by e.g. Atomic Absorption Spectrometry and ICP Optical Emission
Spectrometry. The materials investigated are the metals aluminium, magnesium, and iron,
and alloys.
A special topic is the corrosion of thin films, formed by plasma and ion beam methods,
such as diamond-like amorphous carbon, or by sol-gel synthesis in combination with spin
coating, such as zirconium oxide. These films (on the nanometer scale, i.e. nanofilms)
suffer from microporosity which greatly influences the film/substrate corrosion
performance. The underlying corrosion mechanisms and the correlation between film
deposition parameters and corrosion protection ability are investigated.
Nanopores and nanowires
In collaboration with Gesellschaft für Schwerionenforschung (GSI), membranes or
microfilters are formed by irradiation of polymer foils (polycarbonate, polyimide) and
chemical etching the latent ion tracks to pores. These ion track filters (ITNF: ion track
nanofilters, when the pores have diameters < 100 nm) can be used for filtering liquids from
particles, collecting aerosols, for gas separation, and for analyzing small molecules and
molecular fragments by translocation.
In a further process step, the nanopores are galvanically filled with metals, such as copper
or gold, forming nanowires. The nanowires can be gained by dissolution of the polymer
template. Dimensions, surface topography, microstructure, and crystallinity are
investigated. Further, properties such as electrical conductivity and thermal stability are
studied. The wires decay upon heating to a chain of spheres (Rayleigh instability). This
effect is investigated.
Materials in Radiation Fields
In a number of applications, such as in nuclear facilities, particle accelerators and in
space, materials are exposed to energetic ionizing radiation. The irradiation may lead to a
degradation of the materials properties. Polymers are particularly sensitive towards
ionizing radiation. In a collaboration with GSI, polyimide and polyepoxide, which are
components of superconducting beam guiding magnets, were irradiated with relativistic
heavy ions and characterized for their properties, such as network degradation and
electrical conductivity. Another material is polycrystalline graphite, which is being used as
the target wheel and as the beam dump.
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