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Plasma Chemical Processes

The research program “Plasma chemical Processes” focusses on the physics and chemistry of reactive plasmas, develops new concepts for plasma reactors as well as approaches and methods for controlling plasma chemical processes.

To this end, the composition of various plasmas, i.e. the concentrations of charged and uncharged plasma components, the energy distribution in the plasma, the radiation emitted by the plasma and the interaction of the plasmas with the boundary surfaces are analyzed. Among other aspects, the focus is on developing new methods for controlling plasmas for surface treatment and plasma-chemical conversion of gases.

State-of-the-art methods of infrared absorption spectroscopy are available for the investigations, which are highly sensitive for the determination of the concentration of molecules in plasmas and can also capture their kinetics. In addition, fast imaging methods can record the formation of the plasmas and discharge regimes, which to explore the correlation between discharge physics and plasma chemistry. In addition, models and simulation tools are available for the detailed analysis of multiphysical processes. New plasma reactors are also designed or optimized based on the findings of basic research, long-term experience in the construction of plasma sources and their electrical characterization. The work is often carried out in close cooperation with partners in science and industry.


Application fields

Non-thermal plasmas that can be operated at atmospheric pressure are an important technology today. Such atmospheric pressure plasmas, whose gas temperature barely exceeds room temperature, are used to modify sensitive surfaces, in the treatment of gases and in medical applications. The research program investigates plasma jets and barrier discharges, among other plasma sources. On the one hand, the processes of plasma formation, i.e. the mechanisms of electrical breakdown, are of interest, and on the other hand, the determination of the reactive species and the identification of the dominant plasma-chemical conversion processes.
To study the electrical breakdown, high-end techniques of fast imaging and spectroscopy, ICCD and streak cameras and single-photon counting with time resolutions down to the sub-nanosecond range, as well as time-resolved electrical measurements are carried out. Another important research question is the extent to which the concentrations of the resulting reactive species can be specifically controlled. To this end, the absolute concentration of key species is determined and the most important production and consumption mechanisms are identified using models. For atmospheric pressure plasmas, classical plasma diagnostics methods cannot be used or to a limited extent only. Therefore, the further development of diagnostic techniques, such as absorption spectroscopy, in particular cavity ring-down spectroscopy, is one of our activities, see also the website of the Plasma Diagnotic Group.

The coupling of plasmas and catalysts enables synergies and offers a complex field of research that can pave the way for the synthesis and decentralized production of new materials and special, value-added chemicals. Non-thermal plasmas enable chemical processes with high activation energy while the selectivity can be improved and optimized with catalysts. The interaction is extremely complex and not yet fully understood. We are interested in how the physical and chemical properties of catalytically active components affect the discharge physics and how reactive plasma components influence chemical processes on the catalyst.

Investigations of non-thermal reactive plasmas cover barrier discharges and plasma jets at atmospheric pressure as well as low-pressure plasmas. The focus is on the analysis of plasma-chemical processes, the interaction of plasmas with its boundaries and the optimization of plasma sources for various applications. The models and simulation tools available at the INP enable a time-dependent and spatially multidimensional description and detailed analysis of plasma-physical and reaction-kinetic effects, see also the website of the Department of Plasma Modeling and Data Science.

Nonthermal plasmas at atmospheric pressure are state of the art in ozone synthesis and the degradation of odors. The discharge type of dielectric barrier discharge, which is mostly used, is characterized by its relatively simple operation, robust operation and very good scalability. The development of new plasma reactors is based on the sound understanding of these mostly filamentary plasmas (streamer breakdown) using experimental methods and multidimensional plasma modeling. Electrical equivalent circuit diagrams allow the determination and monitoring of plasma operation and can predict the influence of changing conditions. In addition, we are working on similarity principles in order to develop scaling concepts to enable a successful transfer into industrial practice.

The complex chemical nature of molecular plasmas is a challenge for conventional absorption-based diagnostics. For example, a spectrometer based on low bandwidth cw lasers can only measure a few transitions of some molecular species. With careful selection of the spectral range, other species can be measured simultaneously, but the problem of cross-sensitivity prevails. In contrast, broadband spectrometers such as Fourier transform infrared (FT-IR) spectrometers and dispersion-based spectrometers have broad spectral coverage and can measure multiple species in the plasma almost simultaneously. However, FT-IR spectrometers that use incoherent light sources have limited spectral resolution. Another challenge in absorption spectroscopy of molecular plasmas is the lack of accurate spectroscopic parameters. To address these challenges, we are developing and applying frequency comb-based spectroscopy techniques for broadband, fast and precise measurements of absorption spectra of molecular species in plasmas as well as in reference gas samples at elevated temperatures.

The terahertz (THz) range of the electromagnetic spectrum is located between microwave and infrared radiation and offers many potential applications, ranging from basic research to security scanning and biomedicine. THz radiation is also of great importance for plasma physics, as many physical phenomena and effects in plasmas take place in an energy range that corresponds to that of THz radiation. This enables the detection of certain atoms and molecules, but also electrons and ions, which is highly important for understanding plasma chemical processes. At the INP, we are investigating different THz spectroscopic methods to determine absolute densities of a variety of technologically relevant species, such as oxygen atoms. Our novel approach is based on the detection of the fine structure transition of ground-state oxygen atoms at 4.75 THz using compact THz quantum cascade lasers. These lasers have been developed and manufactured in close cooperation with the Paul-Drude-Institut für Festkörperelektronik (PDI).

Plasma technology plays a key role in the production of microelectronics; almost every second step in the manufacturing process is a plasma process. Despite the wide range of applications the chemical and physical aspects are not fully understand yet. However, this knowledge is important for optimizing the processes, for example, for smaller and faster circuits. In addition, process control in the semiconductor industry is becoming increasingly important. The duration of the processes and the quality of the layers being produced needs to be optimized. In particular, the detection of atoms, e.g. oxygen or fluorine atoms, is of great importance, but so far is a challenge due to the lack of suitable methods for their detection in the industrial practice. In addition to the development of highly sensitive diagnostics, fundamental questions about plasma-surface interactions are investigated at the level of basic research. These activities are considered primarily in tight interactions with simulations.


Project topics

The application of atmospheric pressure plasmas for coating or modification of surfaces has attracted considerable interest since the 1990s. Despite the considerable application potential of an atmospheric pressure PECVD (e.g. for solar cells, in corrosion protection, in glass industry, for textiles or in pharmaceutical technology), the current level of knowledge of the physico-chemical mechanisms of layer deposition is comparatively low. One open question is whether layer formation takes place via radicals or ions. The main idea of the "FiloSurf" project is to utilize the characteristic properties of dielectric barrier discharges with short gas retention times in order to improve the understanding of the ongoing mechanisms. The project is a cooperation with the TU Braunschweig. Our efforts are aimed to the role of excited argon atoms as important energy carriers for ionization, dissociation and excitation processes, both experimentally, in particular by means of laser absorption spectroscopy, and by means of numerical modelling.

The aim of the "PlasCCO2" project is to use carbon dioxide as a raw material for the production of higher hydrocarbons. The Federal Ministry of Education and Research is supporting the project as part of the funding measure "CO2-Win". PlasCO2 stands for 'Plasma-induced generation of carbon monoxide from carbon dioxide and its chemical utilization'. We are working on new processes to produce synthesis gas from carbon dioxide and hydrogen using a plasma reactor. The synthesis gas obtained in this way can then be used for the manufacture of chemical products. The project consortium is coordinated by Evonik and consists of the INP, the Leibniz Institute for Catalysis e.V. (LIKAT) and Rafflenbeul Anlagen Bau GmbH.

In this project, funded by the DFG and the NSF, the conversion of nitrogen oxides into nitrogen by plasma catalysis is to be investigated experimentally and by means of modeling. In particular, the role of short-lived species for catalytic processes in narrow discharge geometries will be examined. Project partners are the TU Hamburg and the University of Minnesota. The work at the INP focuses on modeling the processes.

The overall goal of biogeniV (www.biogeniv.de) combines the challenges of climate change and energy transition with the potential of the bioeconomy in the eastern region of Mecklenburg-Vorpommern by converting up to know unused biogenic residues and biogenic carbon dioxide for material or energy use. The embedded project bV-A1 "Decentralized biomethanol production" bundles the research and development of new technologies for the utilization of biogenic carbon dioxide for the synthesis of fuels and valuable materials. The aim is to investigate and further qualify process approaches that have the potential to store volatile renewable energy at decentralized biomass processing plants. The partners are TAB Maschinen- und Stahlbau GmbH, Stralsund University of Applied Sciences with the Institute for Regenerative Energy Systems (IRES), the Leibniz Institute for Catalysis (LIKAT) and the Fraunhofer Institute for Ceramic Technologies and Systems in Hermsdorf.

The aim of this DFG project is to develop and test two suitable detection methods of a frequency comb in the mid-infrared range for highly sensitive multispecies detection in plasma nitrocarburizing processes. Specifically: (i) a Fourier transform spectrometer, which allows the detection of all absorbances of the predominant C-H and N-H containing species (e.g. CH4, C2H2, HCN, and NH3) within the comb bandwidth, and (ii) a so-called Virtually Imaged Phased Array (VIPA) spectrometer, which allows a time resolution of microseconds for kinetic measurements of volatile radicals (e.g. CH3, CH2, NH, and NH2). With the implementation of an optical resonator, the VIPA spectrometer will be further developed to increase the detection sensitivity for radicals by at least four orders of magnitude. Furthermore, it is intended to elucidate the complex chemistry of hydrogen cyanide (HCN) due to its role also in other carbon, nitrogen and hydrogen containing plasmas. Particular attention will be paid to the isomerization to the more reactive isocyanide isomer HNC, which is assumed to influence plasma properties due to its reactivity. The determination of concentration profiles as a function of gas composition and plasma power as well as a comparison with a kinetic model will be used to postulate and validate previously missing elementary [H,C,N] mechanisms. In the future, the methods to be developed in this project can also contribute to the characterization of complex gas matrices, for example in aerosol chemistry.


Partner

  • Universitäten Greifswald, Rostock und Kiel, HS Stralsund, TU Hamburg, LIKAT Rostock, TU Braunschweig, TU Freiberg, Fraunhofer IKTS, Paul-Drude-Institut
  • Evonik, Rafflenbeul-Anlagenbau, Cosun Beet Company Anklam, TAB Barth, RÜBIG, Menlo Systems
  • University of Minnesota, TU Eindhoven, LAPLACE  Toulouse, Masaryk University Brno, University of Leeds, University of Birmingham, Umea University, University of York, Université Sorbonne Paris Nord, NIST

 

Publications


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Contact

Leibniz Institute for Plasma Science and Technology
Felix-Hausdorff-Str. 2
17489 Greifswald

Prof. Dr. Ronny Brandenburg
Programme Manager "Plasma Chemical Processes"

Phone: +49 3834 - 554 3818
Fax: +49 3834 - 554 301

brandenburginp-greifswaldde
www.leibniz-inp.de

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