Justin Chen: Atmospheric-Pressure Plasma Sprayed Films (Fraunhofer IFAM)

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Back in early 2020, my research supervisor, Prof. Reinhold Dauskardt, started a collaboration with the Fraunhofer Institute for Manufacturing Technology and Advanced materials (IFAM) in the city of Bremen, Germany. However, due to COVID, the timeline for this collaboration was delayed and initial plans for a researcher exchange and extended stay were cancelled. Fortunately, the support from GRIP allowed me the opportunity this past summer to visit Fraunhofer IFAM and conduct meaningful research that would supplement my ongoing research at Stanford. I was fortunate to spend ten weeks at Fraunhofer IFAM where I performed research with supervisor Dr. Uwe Lommatzsch, and colleagues Dr. Laura Schilinksy and Annika Stalling.

Atmospheric-Pressure Plasma and Open-Air Spray Deposition of Mixed Organic-Inorganic Films

At Fraunhofer IFAM, I was in the department of atmospheric-pressure plasma and surface treatments. Atmospheric-pressure plasma, as the name suggests, is a highly ionized gas operating at normal, atmospheric conditions (as opposed to low-pressure plasmas). This plasma can be used for a variety of applications focused on changing the surfaces properties of a film. In my research project, I was investigating the effects of spraying a mixed organicinorganic siloxane blend, and then using the plasma to cure the wet film into a solid film. I compared two different experimental setups: 1) spraying the liquid directly into the exhaust of the plasma (i.e. direct injection) or 2) spraying the liquid film first and then subsequent treatment by the plasma (i.e. separate injection). I discovered that films made using the latter experimental setup were significantly more uniform, and that direct injection caused intense chemical reactions that resulted in a premature powder formation and non-uniform film. The plasma dosage had to be just right – too little and the film was still wet, but too much and the film could be damaged.

Films for Corrosion Protection

With the successful demonstration of sprayed films, the second step was to determine an application for the material. We decided to test the anti-corrosion properties of the films made by direct or separate injection. For this, we deposited films on coupons of cold-rolled steel and then aged them in chambers containing a 5% salt (NaCl) solution environment. After a few hours, it was clear that the separate injection films provided the best corrosion protection and performed even better than a standard hexamethyldisiloxane (HMDSO) barrier film.

Although the internship was quite short at just ten weeks, we were able to gather significant results that demonstrated the effectiveness of our film. Before I left, I made several more films that are currently being analyzed using more advanced techniques such as X-ray Photoelectron Spectroscopy (XPS) and Fourier-Transform Infrared Spectroscopy (FTIR). These characterizations may help explain the chemical basis for why the films form differently from the different injection setups and why the films performed differently for anti-corrosion protection. After collecting this new data, my team and I plan to submit a manuscript for publication.

On the weekends, I traveled to a number of cities including Bremerhaven (a port where a number of Germans left for the Americas), Hamburg, Berlin, and Munich. I loved trying all the different foods including pork knuckle, currywurst, Fischbrötchen, and even foods more local to northern Germany such as labskaus. Some of my favorite weekends were just walking along the Altstadt or by the beautiful promenade. Oh, and the beers are top notch.