Dekontamination von Primärverpackungen mittels Atmosphärendruckplasmen

Decontamination of primary packaging by means of atmospheric plasmas The increasing demand of perishable products in urban areas as well as the globalisation of the markets also rises up the requirements for packaging. The storage life of these products is provided by microbial reduction in food and packaging, which is realized by aseptic filling or diffusion barriers. Furthermore, in pharmaceutical products it is recommended that preserving agents should not be added to avoid allergic reactions. Therefore packaging with low microbial load up to sterility is needed. Sterilization in wet (peracetic acid) or dry (hydrogen peroxide) set ups are currently available and used in the beverage industry. Pharmaceutical and food industry would prefer decontamination methods without hazardous substances. The possibility of plasma to generate antimicrobial effective components such as UV light, charged particles (ions, electrons) and reactive radicals offers an alternative to common decontamination methods. Plasmas can be separated in two main groups, the low‐pressure plasma and the atmospheric pressure plasma which have advantages and disadvantages. However, both are expected to require lower total process times than the current chemical methods. The construction for bottle treatment used in this study is based on microwave‐driven self propagating discharge. A careful design of the plasma source by using simulation tools is necessary to avoid hot spots during the bottle treatment. Minimization of process times before and after the decontamination treatment is necessary for industrial processes. The lock in and lock out of the bottles into the microwave area may be a limitative factor. Therefore the development of a barrier‐free transport system for 200 ml PET bottles was realized in this work. Temperature investigations of the material PET showed a critical temperature range above 60 °C at 4 cycles of 1000 W. After an 1 second plasma treatment a maximal reduction rate of 2 log10 was observed. A longer treatment time of 5 minutes led to an inactivation of 4 to 5 log10 for vegetative bacteria and of 2 to 3 log10 for Bacillus spores. Moreover an optimization of plasma generation inside the bottles may increase the microbiological inactivation. An optimization of the antimicrobial efficiency is necessary and detailed investigations of inactivation mechanisms of atmospheric pressure plasma should follow.     

Charakterisierung der Oberflächenmodifikation von Edelstahlproben nach Elektronen- und Ionenbombardement mittels REM,AES und XPS

The interaction of an inert or reactive gas plasma with the surface of stainless steel was investigated with the aim, to modificate the surface and to influence by this the outgassing rate of the material. This question is especially interesting in applications of these materials in large UHV devices, where a heat treatment of surfaces at the vacuum side is not favourable because of the high energy costs. The investigated samples were exposed to the influence of electrons, argon and oxygen ions either in a DC glow discharge or in a microwave discharge. After this pretreatment the surfaces of the samples were investigated with respect to the topography and the chemical composition (depth profile) by Secondary Electron Microscopy (SEM), Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS). These surface modifications as a result of the different treatments of the samples were correlated with the measurements of the outgassing rate.     

Hochvakuumpumpe gegen Atmosphäre

High vacuum pump working against atmosphere The OnTool^TM Booster vacuum pump consists of side channel and Holweck pump stages, achieves 10⁻⁵ mbar (10⁻³ Pa) pressure and works against atmosphere. Research, which is done on side channel pump stages, shows ways to increase the compression and pumping speed and to reduce their power consumption. The experiments show that rotors with radial blades machined on both sides at the periphery of the rotor have a better performance than rotors with radial blades machined only on one side of the rotor, rotors with semicircular blades or rotors with straight blades. It was also shown that the compression ratio of side channel pump stages depends on the number of radial blades at the periphery of the rotor. The compression ratio of side channel pump stages achieves its maximum at a specific number of radial blades in the rotor N_m = D · k_m because the momentum and energy transfer from rotor to gas in the side channel has its maximal value with this number of radial blades. Reduction of the axial gaps between the rotor and the stator increases the compression ratio of side channel pump stages as expected due to lower leakage along the gaps.     

Mikrowellen‐Plasmabrenner bei Atmosphärendruck

Microwave Plasma Torch at Atmospheric Pressure The development of the microwave plasma torch shows that a combination of two resonators is targeting for a reliable ignition under atmospheric pressure and stable continuous operation at high power conditions. An adapted gas management with jacket flow and good mixing can be produced by the coaxial design. The spectroscopic investigation of the torch gives information about the spatial temperature distribution in the plasma. The distribution of the OH‐rotation‐vibration band is observed in the line of sight with a high spectroscopic resolution. In an air plasma a constant core gas temperature of 3600 K is determined. It is independent of the outside parameters, like microwave power or gas flow. Only the plasma volume adapts, in order to keep the energy content constant.     

Plasmachemisches Ätzen und Beschichten bei Atmosphärendruck

Atmospheric pressure plasma‐chemical etching and deposition. Application in crystalline silicon photovoltaics. For industrial processing of wafer based crystalline silicon solar cells a variety of different technologies are applied. The combination of these requires a complex wafer handling; increasing not only investment costs, but also the risk of wafer breakage. Application of plasma technologies offers the possibility to manufacture crystalline silicon solar cells without any wet chemical or vacuum processes. At Fraunhofer IWS all etching steps necessary for the production of solar cells and the deposition of silicon nitride as passivation and anti‐reflection coating were demonstrated successfully using atmospheric pressure plasma technologies.     

Plasmachemische Gasphasenabscheidung und Plasmaätzen bei Atmosphärendruck

Plasma enhanced Chemical Vapour Deposition and plasma etching at atmospheric pressure Plasma processes are applied for a variety of surface modifications. Examples are, e.g. coatings to achieve an improved corrosion and scratch protection, or surface cleaning and texturising. Since these processes, however, usually take place in vacuum, they are unfortunately not applicable for large area industrial use. Plasma enhanced CVD processes at atmospheric pressure enable the deposition of functional coatings on components and semi‐finished parts with in a continuous air‐to‐air process without the use of expensive vacuum systems. By their integration into in‐line production processes the substrate handling and the coating costs are definitely reduced. A thermal plasma source, basing on a linearly extended DC arc discharge at atmospheric pressure, has been tested for the deposition of silicon nitride at substrate temperature of less than 300° in a continuous PECVD process. Furthermore this source has been tested for plasma‐chemical etching and texturising of silicon as well.     

Schichtabscheidung mittels Ionenstrahlzerstäuben

Ion Beam Sputter Deposition – Fundamentals and Application for Tailoring Thin Film Properties Ion beam sputter deposition (IBSD) is a PVD technique, which, in comparison to other PVD techniques, is known to produce thin films with desirable properties, for instance, with improved adhesion, dense film structure, less defects, higher purity, less particle contamination, and better controlled composition. Recent systematic and comprehensive investigations of the fundamentals of the whole IBSD process revealed previously unemployed opportunities for tailoring thin film properties over a wide range. The main process parameters were identified to be the scattering geometry and the ion species, or, to be more precise, the mass of the primary ion relative to the mass of the target particle. By choosing these parameters appropriately, structural, optical or electrical properties, to name but a few, can be adjusted according to the technological requirements. The present contribution aims on illustrating these opportunities by presenting the main fundamentals and selected examples.     

Mikrowellen‐PECVD für kontinuierliche Großflächenbeschichtung bei Atmosphärendruck

Microwave PECVD for continuous wide area coating at atmospheric pressure Plasma processes are applied for a variety of surface modifications. Examples are coatings to achieve an improved corrosion and scratch protection, or surface cleaning. Normally, these processes are vacuum based and therefore suitable to only a limited extend for large area industrial applications. By use of atmospheric pressure plasma technology integration in continuously working manufacturing lines is advantageously combined with lower costs and higher throughput. Microwave plasma sources present powerful modules for plasma enhanced chemical vapour deposition at atmospheric pressure. At Fraunhofer IWS processes and equipment as well as application specific materials are developed. The coatings are suitable for scratch resistant surfaces, barrier and corrosion protective layers or anti‐reflex layers on solar cells. The film properties achieved are comparable with those produced by low pressure processes.     

Gesteinbearbeitung mittels dünner Kreissägeblätter

Treatment of stones by means of thin circular saw blades Circular saws and/or abrasive machining of granite or marble blocks takes place in the industry by block circular saws with 40 to 80 circular saw blades on a shaft. Each of these tools with a tool diameter of approx. 1,000 mm produces a kerf of approx. 6.5 mm. By use of a case‐hardened quality for the master sheets the master sheet thickness and the kerf can be reduced approx. 1 mm. Related to the block which can be separated substantial material savings result in the case of sawing of high‐quality raw materials. Because the used tools are to finish very difficulty with conventional, mechanical technologies, the laser technology became develops for stretching and arranging the disk‐shaped tools. The Laser application is a requirement for the automizableness these work procedures.     

Herstellung von Präzisionsschichten mittels Ionenstrahlsputtern

Precise thin film synthesis by ion beam sputter deposition Ion beam sputter deposition (IBSD) is a promising technique for the fabrication of high performance thin films because of the well defined and adjustable particle energies, which are rather high in comparison to other PVD techniques. Recent developments concerning long‐term stability and lateral uniformity of the ion beam sources strengthen the position of the IBSD technique in the field of precise thin film synthesis. Furthermore, IBSD offers a more independent choice of relevant deposition parameters like particle energy and flux, process gas pressure and deposition rate. In this paper we present our currently installed large area IBSD facility “IonSys 1600”, which was developed by Fraunhofer IWS Dresden and Roth & Rau company (Hohenstein‐Ernstthal). Substrate sizes of up to 200 mm (circular) or up to 500 mm length (rectangular) can be coated and multilayer stacks with up to six different materials are possible. Tailored 1‐ or 2‐dimensional film thickness distributions with deviations of < 0.1 % can be fabricated by a relative linear motion of the substrate holder above an aperture. In order to demonstrate the advantages of the IBSD technique especially for sophisticated materials and films with high requirements concerning purity, chemical composition or growth structure, several examples of deposited multilayers for various applications are presented.     

Applikation ausscheidungshärtender Bronzeschichten mittels Hochgeschwindigkeitsflammspritzen

Application of age hardenable‐copper‐based‐coatings trough HVOF‐spraying Thermal spraying of age hardenable copper based alloys, enables the producing of wear resistant coatings with high conductivity. With high velocity flame spraying it is possible to create dense coatings with good adhesion to the substrate. The coatings are produced in two steps the thermal spray process itself and the followed heat treatment. The characterisation of the produced specimen shows promising results. The achieved wear resistance of the coatings is similar to bulk material and better than pure copper.     

Lebensdauerabschätzung an Kunststoffrohren mittels Zeitstand‐Innendruckversuch

Lifetime Prediction of Plastic Pipes by means of Internal Pressure Creep Test The Lifetime Prediction of plastic pipes is based, according to the current set of relevant technical regulations, mainly on the Internal Creep Rupture Test. In this examination, the test for the pipes performed in an accelerated mode with a defined internal pressure and at increased temperatures. In compliance with the applicable Arrhenius rate law, an extrapolation of the measured values then takes place.     

Flächige Abdichtung erdberührter Bauteile mittels Injektion

Die Schirminjektion ist ein Injektionsverfahren zur Abdichtung von erdberührten Bauwerken gegenüber Grundwasser, bei denen aufgrund der speziellen Gegebenheiten eine Behebung der Undichten des Baukörpers technisch nicht möglich oder ökonomisch nicht sinnvoll erscheint. Durch die Schirminjektion werden die Wasserwege im anstehenden Boden mit Kunstharzgelen verfüllt und abgedichtet, so dass der injizierte Boden die Funktion einer neuen Abdichtungsebene übernimmt. Der Beitrag beschreibt die Eigenschaften der verwendeten Gele und die qualitätsbestimmenden Schritte von der Voruntersuchung des Mauerwerks, über die Planung und Ausführung bis zur Qualitätssicherung und Dokumentation. Auch ökologische Aspekte der Injektion im Boden werden angesprochen. Waterproofing of Subgrade Constructions by Curtain Grouting. Curtain grouting is a method for waterproofing subgrade constructions where the sealing of the leakages in the construction is technically not possible or economically not sensible. By this kind of grouting the capillaries and cavities in the soil surrounding the construction are filled and sealed with polymeric gels. The grouted soil forms a new waterproofing body outside the structure. The properties of the used gels are described as well as the necessary steps to control the quality, including preliminary enquiries of the masonry, planning and execution of the grouting process, quality control and documentation. Also ecological aspects of grouting in soil are discussed.     

Elektronenstrahlschweißen an Atmosphäre – von der Entwicklung bis zum industriellen Einsatz

Non vacuum electron beam welding – from development to industrial application Attributable to the increasing degree of standardisation in many fields of industrial manufacturing, the saving of resources and thus the demand for light weight constructions and also the rapid development on the material sector have made joining tasks increasingly complex. This involves the joining method which must meet the metallurgical demands of the base materials to be welded and also the method’s profitability. In this connection, electron beam welding in atmosphere – NV‐EBW ‐ as a joining method is getting more and more important and is, from the side of the industry, becoming increasingly popular. NV‐EBW combines the many, well‐known advantages of electron beam welding in vacuum with the possibility to work under normal ambient pressure. With an equipment efficiency of more than 50 % and very high, achievable welding speeds of up to 60 m/min for aluminium materials, the electron beam in atmosphere is an efficient and profitable tool for welding. Under the direction of Professor U. Dilthey, the ISF has for many years and in close contact with industrial partners carried out research work in the field of the NV‐EBW technology. At that, elementary contribution to the development of rotationally‐symmetrical orifice assemblies and also to the testing and optimization of the method with regard to respective welding tasks has been carried out.