Analytics

Colloidal characterization of particles of steel

The outstanding mechanical properties as well as the exceptionally good weldability of low-alloy steels is due to carbonitride nanoparticles generated in the steels during production.

In cooperation with Dillinger Hütte, a steel producer in Saarland, we are investigating the chemical composition, morphology and size distribution of the particles present in the steel.  Particle characterization is performed using methods that we have developed for colloids. These statistically relevant methods have so far been little used in metallography.

Agglomeration of nanoparticles in microgravity

Modern methods of "self-arrangement" allow us to produce even larger structures from nanoparticles whose geometry is defined to a certain degree. This is very interesting for materials: For example, electrically conductive metal nanoparticles can be arranged in an insulating matrix in this way to maximize or minimize conductivity, depending on whether you need a dielectric or an electrical conductor.
Unfortunately, gravity gets in the way: larger arrays of metal particles are very delicate, but heavy enough to be torn apart by their own weight, so that connectivity and thus conductivity are lost, for example. In project ARNIM, with the support of the German Aerospace Institute (DLR), we are investigating whether this can be prevented by switching off gravity. To this end, we are initially using a drop tower (ZARM in Bremen) and "throwing" agglomeration experiments in such a way that gravity is suspended for a few seconds. In the future, experiments aboard rockets or the international space station are also planned, which will allow longer agglomeration experiments.
If it turns out that the agglomerates are indeed destroyed by their weight, we will have to strengthen them - for example, by using nanowires. But it could also be that it is not gravity at all, but details of the agglomeration process. These questions are therefore the focus of the project.