Michael Thieme

Generation of Ultrahydrophobic Properties of Aluminium – A first Step to Self‐cleaning Transparently Coated Metal Surfaces

In the last few years, significant efforts have been made to provide surfaces with self-cleaning properties. This approach utilises principles wich have been discovered in nature, like the well known lotus-effect. The transformation of this strategy to metallic surfaces is a scientifically and technologically challenging target. This publication focuses on the investigation of different routes for the generation of the necessary micro-morphological propoerties of Al

Titanium powder sintering for preparation of a porous functionally graded material destined for orthopaedic implants.

This work focuses on basic research into a P/M processed, porous-surfaced and functionally graded material (FGM) destined for a permanent skeletal replacement implant with improved structural compatibility. Based on a perpendicular gradient in porosity the Youngs modulus of the material is adapted to the elastic properties of bone in order to prevent stress shielding effects and to provide better long-term performance of the implant-bone system. Using coarse Ti particle fractions the sintering process was accelerated by silicon-assisted liquid-phase sintering (LPS) resulting in a substantial improvement of the neck geometry. A novel evaluation for the strength of the sinter contacts was proposed. The Youngs modulus of uniform non-graded stacks ranged from 5 to 80 GPa as determined by ultrasound velocity measurements. Thus, the typical range for cortical bone (10–29 GPa) was covered. The magnitude of the Poissons ratio proved to be distinctly dependent on the porosity. Specimens with porosity gradients were successfully fabricated and characterized using quantitative description of the microstructural geometry and acoustic microscopy.

Wettability Of Methacrylate Copolymer Films Deposited On Anodically Oxidized And Roughened Aluminium Surfaces

The wetting behavior of water on methacrylate copolymer films was studied on anodically oxidized and micro-roughened aluminium surfaces and also on smooth model surfaces. The copolymerization of tert-butyl methacrylate with a methacrylate containing a fluoroorganic side chain led to a considerable decrease of the surface free energy, but not to a superhydrophobic behavior of polymer-coated, micro-roughened aluminium surfaces. However, copolymers containing both hydrophobic and hydrophilic sequences are able to form superhydrophobic films. X-ray photoelectron spectroscopy showed that an enrichment of the interface between the solid phase and the air by fluorine-containing polymer components was the reason for the strong decrease of the surface free energy. The hydrophilic segments of the copolymers improved the ability to wet the highly polar aluminium surface and to form films of higher density.

Modern Speciation Techniques Applied to Environmental Systems

Many nuclear facilities in the U. S., Europe and elsewhere have reached the end of their designed life expectancy. Often contamination extends beyond the main technical parts of the installations slated for controlled decommissioning or is contained by methods not totally reliable for long-term storage. Large cleanup programs are already under way in the U.S. for former nuclear sites (USDOE, 1989; USDOE, 1990). Other areas contaminated by nuclear accidents, the worst case resulting from Chernobyl, will have to undergo remediation actions (Eisenbud, 1987). And finally, regions affected by the very first step in the nuclear cycle, i.e., the mining and processing of uranium ore, are also listed for restoration measures (BfS, 1992).