10-07/08 :: July/August 2010

nanotimes News in Brief

where it doesn’t,” says Nicholas Winzer, researcher at IWM.

The researchers use the results from the laboratory tests for computer simulation, with which they calculate the hydrogen embrittlement in the metals. In doing so, they enlist atomic and FEM simulation to investigate the interaction between hydrogen and metal both on an atomic and a macroscopic scale. “Through the combination of special laboratory and simulation tools, we have found out which materials are suitable for hydrogen, and how manufacturing processes can be improved. With this knowledge, we can support companies from the industry,” says Dr. Wulf Pfeiffer, head of the process and materials analysis business unit at IWM.

Contact: Dr. Nicholas Winzer, Fraunhofer-Institute for Mechanics of Materials: http://www.iwm.fraunhofer.de

Researchers at the Fraunhofer Institute for Mecha- nics of Materials IWM in Halle, Germany, have created a new generation of filtration membranes: They developed ceramic membranes with a uniform pore structure and a very tight and even pore size distribution. High-precision filtration membranes with a high porosity level.

“Compared to the ceramic membranes we have seen previously, they offer better mechanical stabi- lity and considerably higher flow rates. As a result, for the first time they are also able to replace poly- mer membranes,” notes Annika Thormann, project manager at IWM. These membranes guarantee much more reliable filtration results than polymer

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membranes do. Electron microscope images of the membranes prove: The pores are regularly aligned alongside one another like the honeycombs in a beehive, one identical to the next.

“We use highly pure aluminum that we mold to the desired shape using extrusion equipment and ther- momechanical structuring,” Thormann explains. But just how can you create tiny pores on an aluminum plate with such precision?

“A chemical reaction does the job,” Thormann says. The molded aluminum part is placed in an acid bath where anodic oxidation takes place. An oxide layer just a few microns thick forms on the surface during electrolysis. “Tiny pores form in the alumi- num during oxidation,” Thormann explains. These nanopores are honeycomb-shaped, vertical to the surface, and are arrayed parallel to one another.

“To set the pore size, we have to keep the voltage and the concentration of the acid stable,” Thor- mann notes. The thickness of the nanoporous layer – and hence the flow rate of the membrane itself – can be fine-tuned as well via the duration of the oxidation process. In the end, the only step remai- ning is to open up the pores. This step is accom- plished with chemical etching to remove unneeded residual aluminum.

“We can vary pore diameters between 15 and 450 nanometers,” says Thormann. At 15nm, even the smallest viruses don’t stand a chance of slipping through. The new filtration membranes are parti- cularly beneficial to biotechnology. Aside from use of the filtration properties to produce sterile media the membranes can also facilitate tissue engineering