Prof. Philipp Rudolf von Rohr
Institute of Process Engineering, Switzerland
Plasma-assisted surface modifications of powders and granular particles

Non-thermal plasma treatment is a powerful tool for the surface treatment of temperature sensitive substrates. It allows to beneficially influence substrate surface properties like wettability, dissolution behavior, resistibility, flowability, electrochemical characteristics or microbial contamination (see Figure 1), while bulk properties remain mostly unaffected.In addition, chemical reactions can be efficiently executed, even if they require high reaction enthalpies, due to energetic electrons present in the plasma, while at the same time a low overall temperature of the process can be maintained, due to the low-energy heavy particles (ions, neutrals). 

With a reactive gas plasma (e.g. oxygen containing plasma) the wettability and dissolution behavior of powders can be increased by incorporating polar oxygen groups into the substrate surface. We successfully applied this approach to HDPE powder and salicylic acid powder by plasma treatment in a low pressure inductively coupled tubular plasma reactorfor only 0.1 s. We also transferred this technique to the atmospheric pressure domain where we developed a novel plasma device based on the dielectric barrier discharge principleand applied it for the treatment of PMMA substrates and HDPE powders. 

In a second type of process, coherent films or scattered nanoparticles can be formed in the plasma zone from the addition of organic or organometallic precursors. While the deposition of a coherent film can act as a protective layer or a catalyst, the attachment of nanoparticles (spacers) to the surface increases the flowability of the substrate powder. We successfully implemented these processes in low pressure plasma systems and currentlyare transferring them tothe atmospheric pressure domain. Furthermore, we are investigating the feasibility of graphite powder coating for the improvement of capacity retention and electrolyte compatibility in battery applications. Non-thermal plasma treatment can also be applied for the inactivation of microorganisms and we applied this technique for the decontamination of wheat grains in a low-pressure plasma circulating fluidized bed reactor and an atmospheric pressure dielectric barrier discharge. Currently, we are investigating the inactivation of microorganisms on sprout seeds.


Since 1992       Professor in Process Engineering @ ETH Zurich 

2014               Head of Swiss Competence Center of Research, Efficiency in Industrial Processes 

1999-2001       Department head D-MAVT, ETH Zurich 

1996-1998       Division head D-MAVT, ETH Zurich 

1989-1992       Director at Bertrams, Muttenz, Switzerland 

1984-1989       Head R&D at Bertrams, Muttenz, Switzerland 

1982-1983       Postdoc at MIT, Cambridge, USA 

1979-1983       Scientific collaborator and doctoral student at ETH Zurich 

1978               Diploma in process engineering, ETH Zurich 

Main publications/books 

Total publications > 150

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