Joining Technologies and Corrosion Lab

Understanding boundaries

Apr 19, 2013 | MARCO PETER
"Joining Technology and Corrosion" laboratory since February 2012. Among other things, his team deals with solder connections, corrosion, local electrochemistry and the design of functional alloys, surfaces and boundary layers. Jeurgens originally became involved in this science because of his fascination with rocks.
Lars Jeurgens and his colleague Thomas Suter (right side) check a new test set-up.

As a teenager, Lars Jeurgens was fascinated with minerals and fossils. He looked after and cared for his collection with enthusiasm. It was this passion that influenced him to make the decision to study geology in Utrecht. He quickly noticed that geologists (at the time) were also concerned with matters concerning materials science. For example, one goal was to discover how heavy metals got into the atmosphere and what effect they had there. This topic caught Jeurgens’s interest. He focused his attention on how chromium and tungsten could be filtered out of the environment, rivers, for instance, and experimented with porous oxides for binding the dissolved metals in water, therefore making an initial excursion into the chemistry of boundary layers.

From drill holes to turbine blades
After completing his master’s degree, the 23-years-old changed track and applied his knowledge in physics and chemistry to his job working for mineral oil company Shell. During his work in the laboratory, he had used nuclear magnetic resonance spectroscopy (NMR) to investigate pore fluids in oil-bearing rocks. The method can also be used to analyze the oil content of undersea rock layers. This kind of research was "extremely interesting" in Jeurgens's words, though, without a doctorate, he could not continue to pursue it as project leader.

After working for Shell for a year he therefore enrolled at Delft Technical University. During his doctorate he studied the initial stages of metal oxidation and, as a postdoc, he looked into heat-resistant coatings for the blades of airplane turbines. Jeurgens was involved in the development of a surface treatment that would extend the service life of such a protective coating. Among other things, the scientists collaborated with a Dutch company that was taken over by the Swiss Sulzer Group shortly afterwards. "The partners from the aircraft industry patented our procedure, although it remains a closely-guarded secret as to whether it is actually being used in the field", explains Jeurgens with his soft Dutch accent, which the Swiss find so agreeable.


In his current position at Empa, Jeurgens is still working with surface treatments and coating technologies. Among other things, his team is now investigating how the implant surfaces can be made more corrosion-resistant and biocompatible using an oxidative pretreatment. Because if an implant made from a material such as stainless steel starts to corrode within the human body it can release iron, chromium or nickel, which, in turn, can lead to complications such as inflammation.

Basic research at the Max Planck Institute
Before Jeurgens joined Empa, he had worked at the Max Planck Institute for Metals Research in Stuttgart for almost ten years. His family – by then, Jeurgens had got married to a Swiss lady whom he had met on the train during a pre-university Interrail trip – moved from Holland to Germany, and the young father of two took on several responsibilities at once. On the one hand, he was responsible for services in the surface analysis area, and on the other hand he led his own research group, which was involved in the analysis of the chemical processes and phenomena on surfaces and in boundary layers. And they were successful: The Deutsche Gesellschaft für Materialkunde (German Society for Materials Science) awarded Jeurgens's work the Masing Memorial Prize in 2008. He also taught at the University of Stuttgart and the "Max Planck International School for Advanced Materials".

But the wind of change was starting to blow: Jeurgens wanted to use his knowledge in basic research – as is carried out at the Max Planck Institute – for more practical uses in industry. Because: "We published our results but never really found out what industry really did with it."


It’s the team that counts
The timing of the job opening at Empa, which was looking for a new laboratory head, was just about perfect. And the job looked extremely interesting, too: The objective was to merge the "Joining Technology" and "Corrosion" laboratories. To Jeurgens, it was an extremely sensible idea: "In both cases, it’s all about reactions in boundary layers."

The work with boundary layers does not just keep him busy in the lab but also when his leadership capabilities are in demand: "Team mentality is what counts as far as I’m concerned. There are people here in the lab with an unbelievable amount of experience. I am bringing in my own experiences, so now it is a case of combining our accumulated knowledge." He and his team now frequently work with industry partners and develop innovative solutions for practical use – i.e. in exactly the way he had imagined it during his time at the Max Planck Institute. In cooperation with companies from the medical engineering area they are developing surface treatments for magnesium-based materials for use in biodegradable implants, for example. The keyword here is biocompatibility.



A sample with 200 overlaid nanolayers is heated to 700 degrees. As soon as molten copper penetrates through the barrier layers, an extremely weak current flows. In order to rule out electrical interference, the entire test set-up is shielded with sheets of copper.



Nano enters joining technology
In his work with nanostructured soldering foil for use in joining technology Lars Jeurgens is faced with a major challenge. He wants to develop methods and procedures for soldering nanomaterials or electronic components at low temperatures, among other things.

Materials as heat-sensitive as these do not join well using conventional methods because their microstructures would change at the high process temperatures and they would, therefore, lose some of their advantageous mechanical or physical properties. The trick: Jeurgens coats the heat-sensitive materials with a nanostructured, metallic soldering material. For example, nanocrystalline titanium is provided with a coating system consisting of nanoscale copper and ultra-thin aluminum nitride barriers. The copper layers that are enclosed by aluminum nitride are so thin that they melt at a temperature of about 550 degrees C (rather than the usual 1083 degrees) and join the titanium materials to each other.

The melting behavior is determined by the sensitive equilibrium of the energy contributions of volume and boundary layers in the nanoscale system. This sensitive energy balance and therefore the melting behavior can be adjusted by means of specific changes to the boundary layers and the thickness of the copper coating. This might sound easy, but in practice it is quite challenging. It must also be ensured that the copper maneuvers itself through the thin barrier coatings as required when melting occurs, to react with the basic materials. This procedure could soon be used in innovative process technologies for the manufacture of heat-sensitive components and nanomaterials.

Jeurgens is entering new territory with his research in the nanorange. Only a few of the laws that apply when working with nanomaterials are known. The Empa researcher wants to do his part in conquering this unknown terrain of materials science for industry.


Text Marco Peter. This article appeared in EmpaNews No. 40, April 2013.




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