Conferences and exhibitions

The International Conference on Plasma Surface Engineering will take place for the 17^th time this year. The conference location has been moved to Erfurt. The biennial PSE conference is a well-established forum for discussing the challenges, recent developments and new knowledge in the field of plasma as well as ion- and particle-beam assisted surface modification and thin film technologies. It is equally about the basics and applications of plasma technology. The main topic of the conference, the industrial workshop as well as the Smart Mind Pitch is “Plasma Technology for new Energy Concepts“.

26 topical sessions and 3 poster sessions, 9 plenary lectures (45 min) 26 keynote lectures (30 min) and 160 lectures (20 min) are planned.

The Fraunhofer IST participates in the exhibition of the conference on September 8^th and 9^th as part of the joint booth of the Competence Network INPLAS and in the scientific conference program.

Scientists from the Fraunhofer IST supplement the program of this year's Special PSE 2020 with contributions as part of one of the three tutorials, the scientific program and the poster presentations.

Monday, September 7, 2020

Tutorial 1: Fundamentals and Trends of Plasma Surface Processing

1:15 - 2:15 pm

»Surface engineering with atmospheric-pressure plasmas«, Lecture

Dr. Michael Thomas 

Tuesday, September 8, 2020

Session C1: Plasma polymerisation 

»Adhesive-free bonding of web-like plastic-metal combinations at low temperatures«, Lecture

Annika Mann

Innovative materials often form the basis of modern industrial products in all areas of life. One example are special films, such as films for food packaging, flexible circuit boards, decorative and protective films, whose markets are constantly growing. These materials must meet a wide range of requirements, such as permeation to oxygen and water vapor, optical transparency, temperature stability, easy processability. Laminated films are particularly suitable for such complex functions because the different layers of which they are made of combine different material properties. These composites are often made of plastics and metals and are currently being joined using various adhesives. In addition to the high quantities of adhesives, long-term stability, creep tendency and migration are often problematic. In this paper, a new adhesive-free low-temperature bonding process is presented as an interesting alternative for joining plastic and metal foils. Thin coatings were applied on the polymer and metal surfaces using an Atmospheric-pressure Plasma enhanced CVD process (AP-PECVD). 3-Aminopropyltrimethoxysilane (APTMS) forms a nm-thick adhesive layer, which covalently bonds to the activated webs. Besides polyethylene and aluminium, on which the focus was placed, the adhesion between polyvinylchloride and aluminium was also investigated. In a subsequent step the materials were bonded using a thermocompression bonder at moderate pressure (1,85 N/mm²) and low temperature (< 100°C). Best results were achieved for the bonding of polyethylene with aluminium with adhesives forces up to 2.2 N/mm. By an optimal adjustment of the parameters, such as pre-treatment time, precursor concentration, plasma power and layer thickness, it was possible to generate composites with a high long-term stability. The deposited layers and composites were examined in a basic and application-specific manner by FTIR spectroscopy, contact angle measurements and peel tests on fresh and aged samples. 

Session A1: Simulation and modelling of growth, structure and properties

»Development of a model to predict the s-phase thickness of plasma nitrided austentitic steels«, Lecture

Phillip Marvin Reinders

Austenitic steels are known for their high corrosion resistance but at the same time possess low hardness which results in low wear resistance. A common way to improve the tribological properties of austenitic steels is plasma nitriding. The formation of the so-called s-phase leads to a strong lattice distortion in the surface area which leads to an increase in the hardness. At the same time, in order to retain the corrosion resistance, process parameters such as temperature and duration must not exceed a certain threshold, otherwise chromium nitrides may be formed. The aim of this study is to develop a model which predicts the thickness of the s-phase in plasma nitriding processes. For this purpose, a number of processes were executed and analyzed under specific variation of temperature ranging from 360 °C to 450 °C and duration of 10 to 24 h. Other process parameters such as voltage, pressure, pulse-pause ratio and gas mixture remained constant. A temperature dependent growth rate could be determined after the analysis of the results. On one hand this allows to predict the thickness of the s-phase for any given treatment temperature and process duration in the given temperature window, while on the other hand one of the two process parameters regarding treatment temperature and process duration can be explicitly selected via iso-thickness progressions line and combined with the other to obtain the required thickness of the s-phase. In this way a possible formation of chromium nitride by the plasma treatment can be avoided. The developed model was verified by control experiments and shows a maximum relative error of 5.5 %. The model is currently being extended by an additional parameter, namely the chemical composition of the material, in order to enable transferability. A factor for the transfer of the nitriding depth to other microstructures or steel classes is also conceivable. Subsequently, additional factors for other process parameters, e.g. voltage, gas mixture or pressure, will be included.

Session E3: Plasma diffusion 

Wednesday, September 9, 2020

»Newest developments in Plasma Diffusion Treatment«, Lecture

Peter Kaestner

Plasma diffusion treatment has been used in industry for more than forty years now. Many of the long-standing processes are still used daily. However, extensive new developments were necessary to keep plasma diffusion treatment competitive. Industrial use of plasma nitriding and plasma carburizing of ferritic steel started in the 70s and 80s. Surface hardness and wear resistance were the important technical features at this time. Nowadays, the requirements of surface treatment processes are much more versatile. As a matter of course the wear protection is still the reason for most of the plasma diffusion treatments, but properties like corrosion protection, electrical conductivity or surface morphology become more and more important. Therefore, over the years, plasma diffusion processes were optimized and tailored to operating conditions. Besides the desired technical properties of treated parts, the development of new steel alloys and the application of austenitic stainless steel required changes in the methods. A brief introduction to the plasma diffusion treatment outlines the way to the current state of the technology. Then the contribution exemplifies the influence of high plasma voltage on the growth rate of the compound layer of alloyed steel. The high voltage is possible due to the modern arc-management system in the latest generation of plasma generators. After 2 h at 800 V the compound layer thickness is the same as after 16 h at 500 V. A second example of plasma diffusion is the boriding of tool steel without the formation of pores. PVD diffusion treatment, a B₄C coating with additional heat treatment, allows understanding the diffusion processes and the reason for the formation of pores. The latest scientific research shows efforts focused on plasma diffusion treatment of steel, titanium, nickel-based alloy and aluminum.

Poster Session: D

Thursday, September 9, 2020

»An automated evaluation for the Rockwell indentation test«, Poster

Reinhold Bethke

Coating adhesion is one of the most important parameters for evaluating the quality and functional reliability of thin-films for tribological purposes. The Rockwell indentation test, standardized in ISO 26443 and DIN 4856, is an established test method in industry and research for determining coating adhesion. A hardness indentation according to Rockwell C is performed on the coated component. Any damage to the coating around the indent is qualitatively assessed and classified into adhesion classes according to the visual impression. For this purpose, comparative images are used which schematically show typical crack and spalling patterns in various forms. The evaluation can only be carried out by experienced personnel, but nevertheless, evaluation differences occur with different persons. The documentation is complex and there is no possibility for automation. This procedure no longer meets the current requirements of quality assurance. Therefore, there is an urgent need to be able to carry out an automated quality check of the layer adhesion. In a project, funded by the Federal Ministry for Economic Affairs and Energy, (PtJ_03TNH023A) the basics for an automated coating adhesion test are developed. The overall objective of the project is to move the Rockwell indentation test for evaluating the adhesion of hard coatings from a subjective assessment to an objective measurement and to prepare the results for standardization. The Poster will show the automatic Rockwell indentation device, the technical innovation of the software and fields of application.

Session G1: Plasma treatment

Friday, September 10, 2020

»Treatment of soft-PVC with dielectric barrier discharge to reduce the migration of plasticizers«, Lecture

Dr. Thomas Neubert 

Polyvinyl chloride (PVC) is a frequently used, cost-effective and very durable polymer. For many of its applications (e.g. blood bags, medical tubes, flooring laminate, electrical insulation) a high flexibility of the material is required. Therefore, considerable amounts of plasticizers (in the order of 40% by weight) are added to produce so-called soft-PVC. As these plasticizers are not chemically bound to the PVC, migration may occur. This leads to a shortened service life of these PVC products due to embrittlement or migration of plasticizers into the surrounding material. The latter is particularly critical for applications in the medical sector, as the plasticizers used here are often harmful phthalates that accumulate in the human body as a result. We have found that by treating soft-PVC surfaces in a dielectric barrier discharge under atmospheric pressure in argon gas, the migration of plasticizer molecules from the plastic can be almost completely reduced within treatment times of only 1 minute. To analyze the migration, we exposed the treated surfaces to well-defined amounts of n-decane and measured the dissolved plasticizer amount by ATR-FTIR spectrometry. Since there are no layer-forming precursors, the effect can only be attributed to structural changes of the polymer surface itself. The migration barriers created by this treatment are stable at room temperature for more than 4 months and can withstand short-term heating to 80 °C or storage in aqueous media. In our work we have also investigated the influence of different process conditions (process gas composition, power, treatment time, design of the plasma source) on the migration barrier efficiency for different plasticizers. Especially contamination of the argon gas with more than 1% oxygen or hydrogen led to a significant reduction of the barrier efficiency. Furthermore, the influence of short-wave UV radiation generated in the plasma was studied as well.