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.     

Holzoberflächenmodifikation mittels Atmosphärendruckplasma

Plasma surface modification of wood and wood‐based materials In this article, plasma technical, analytical and application relevant aspects of the plasma treatment of wood and wood‐based materials are presented. With the help of surface energy determinations and adhesion tests it is shown that the surfaces of wood and wood‐based materials can be changed for specific applications. Surface characteristics, which are application‐technological interesting for a later coating or adhesion, can be specifically generated with the use of air plasma. With surface energy determinations of wood and wood‐based materials, a significantly increased polar part of surface energy could be detected after a plasma treatment. Atomic force microscopy analyses of wood composites show that a plasma treatment with the use of ambient air effects an abrasion and a changed surface roughness. Tensile tests and shear tests of coated or adhered wood‐based materials with a plasma treatment show a clearly increased adherence.     

Beidseitige Innen‐ und Außenbeschichtung von PET‐Getränkeflaschen

Double‐sided interior and exterior coating of PET beverage bottles Plasma‐enhanced methods for the interior coating of PET beverage bottles have already been put into practice in the industry. Thereby the achieved barrier properties are limited due to defects in the coating, which emerge during the layer growth and allow a higher permeability. One possible way to improve barrier properties is the double‐sided coating. The implementation of the concept in form of a demonstrator plant is presented. By means of optical emission spectroscopy (OES) as a very versatile and easy to use method for the surveillance of industrial plasma processes, the influence of the gas composition on the plasma homogeneity and barrier properties of the coating is demonstrated. Permeation measurements are carried out, showing the potential of the combined coating process for the deposition of effective coatings.     

Beschichtung und Reinigung von Oberflächen mit Atmosphärendruck‐Plasmen. Coating and cleaning of surfaces with atmospheric pressure plasmas

Since long time dielectric barrier discharges have been in use for technical applications such as ozone synthesis and surface activation treatment of polymers for subsequent printing, pasting, or laquering. A new field of applications for these discharges is opened by their use for plasma‐based coating and cleaning processes at atmospheric pressure. By introducing gaseous monomers (like hydrocarbons, fluorocarbons, silicon‐organic compounds) into the discharge zone, coatings can be deposited on electrically conductive or insulating substrates. Barrier discharges in oxygen containing gases can also be used for the degreasing of surfaces. Owing to the possibility, to sustain barrier discharges in very small volumes, new perspectives are opened for the geometrically structured modification of chemical and physical properties of surfaces as well as for the modification or coating of internal surfaces in microfluidic devices.     

Langzeitverhalten und Einsatzgrenzen von plasmagespritzten CeO2‐ und Y2O3‐ stabilisierten ZrO2‐Wärmedämmschichten

Long‐term behaviour and application limits of plasma‐sprayed CeO₂‐ and Y₂O₃‐stabilized ZrO₂ thermal barrier coatings Investigations of changes in phase composition and mechanical properties of CeO₂ – and Y₂O₃ – stabilized plasma‐sprayed ZrO₂‐based thermal barrier coatings (TBC) after long‐term heat treatments at typical service temperatures were performed. Experimental studies include X‐ray diffraction and mechanical testing. TBCs with a high amount of the tetragonal equilibrium phase t (8 mol‐% CeO₂) show strong degradation due to the high amount of transformation to the monoclinic phase and the related decrease in strength. TBCs with a high amount of tetragonal or cubic non‐equilibrium phases t′ or c′ are more suitable. Among these, TBCs with higher CeO₂‐stabilizer contents (19.5 mol‐% CeO₂/1.5 mol‐% Y₂O₃ and 35 mol‐% CeO₂) show less amounts of monoclinic phase with respect to Y₂O₃‐stabilized TBCs (4.5 mol‐% Y₂O₃), as commercially used. Therefore they seem to have a high potential for long‐term applications.     

Plasmagestützte Flascheninnenbeschichtung

Application of substrate biasing for plasma enhanced inner coating of plastic bottles to improve barrier properties The article summarizes the results of a research project aiming at the improvement of the barrier performance of plastic beverage bottles by means of plasma enhanced barrier coatings. A pilot plant for the biased barrier coating of PET‐bottles was designed and successfully commissioned within the scope of the investigations. In the process, two excitation types are examined: the so‐called in‐plasma process and a single‐sided plasmaline process for the deposition of barrier coatings. Advantages as well as draw backs of both processes are investigated with respect to an industrial implementation. As a result, improvement of the barrier performance by adjustment of the substrate bias is estimated by a factor of 2‐3. At the same time, substantial challenges for the realization of the processes as well as possible approaches for their solution are identified with the support of gas flow simulations.     

Plasmaborieren – Untersuchungen zum Einfluß der Glimmentladung beim Borieren in einer BCl3‐H2‐Ar‐Atmosphäre

Plasma Boriding – Influence of Glow Discharge Conditions Using a BCl₃‐H₂‐Ar‐Atmosphere The plasma boriding process using BCl₃‐H₂‐Ar‐atmosphere is analized by characterisation of glow discharge conditions using optical emission spectroscopy. Additional exhaust‐examination by mass spectrometry depending on treatment parameters contributes to the determination of the reaction mechanisms. Effects that have influence on plasma boriding using BCl₃ are investigated by comparison of the treatment results with the characterisation of the glow discharge. The etching mechanism on the substrate surface can be effectively reduced selecting optimised parameters. So the plasma boriding process using BCl₃‐precursor gets interesting for industrial application.     

Entwicklung von Oxid – Keramik zur Anwendung als Wärmedämmschichten

Development of Oxide Ceramics for an Application as TBC The standard thermal barrier coating material yttria stabilised zirconia (YSZ) is limited in long term operation to a maximum temperature of about 1200°C. As a result further increase of the gas inlet temperature and hence the efficiency of gas turbines are hardly to achieve with YSZ coatings. In a screening procedure especially perowskite (ABO₃, A = Sr,Ba, B = Zr) and pyrochlore (A₂B₂O₇, e.g. A = La and other rare earth elements, B = e.g. Zr) materials have been identified as possible candidates for thermal barrier coatings. Basic physical properties (e.g. thermal expansion coefficient, thermal diffusivity and conductivity) of several candidates have been determined using sintered, dense samples. The possibility of optimization of the properties by using specific compositions will be discussed. From promising materials powders which are suitable for plasma‐spraying have been produced by spray‐drying. New TBC systems consisting of new materials (BaZrO₃, La₂Zr₂O₇) deposited by atmospheric plasma spraying and vacuum plasma sprayed MCrAlY bondcoats were tested in a gas burner facility. Especially La₂Zr₂O₇ coatings gave promising results. A further improvements could be achieved by the use of layered or graded coatings with a YSZ coating at the bondcoat interface and on top a layer of the new TBC material. First results of thermal cycling tests with 1250 and 1350°C surface temperature will be presented.     

Fluor‐Kohlenstoff‐Nanoschichten zur gezielten Oberflächenfunktionalisierung. Fluorine‐Carbon Nano Coatings for Specific Surface Functionalization

This article concerns some aspects of the research and development work, which is done within a project of the German Federal Ministry of Education and Research (BMBF) entitled: “nano functionalization of interfaces for data‐, textile‐, building‐, medicine‐, bio‐, and aerospace‐ technology”. In the following the broad field of applications of a surface modification on a nanometer scale is discussed. Also some scientific methods to characterize surface modifications of this kind are discussed. By means of low pressure plasma technology it is possible to functionalize surfaces and thus to well adjust their properties with respect to their application. This is done without changing the bulk material characteristics. The surfaces of the treated workpieces are covered by an ultrathin, i.e. only a few nanometer thick, fluorine‐carbon polymer layer by a plasma process. The physical and chemical surface properties, such as surface energy, roughness (on nanometer scale), dynamic wetting behaviour, or the adhesion properties against other materials, can be simple changed by varying the plasma process parameters. It is shown, that in future this surface modification will meet a broad field of applications.     

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.     

Modifizierung der Gasabgabe von Edelstahloberflächen durch Ionenimplantation

Several years ago there were established a new ion-implantation technique, the so called Plasma source ion-implantation. This technique was applied on stainless steel samples to implant ions of nitrogen or oxygen into the surface in a controlled manner and to create barrier layers of nitrides or oxides, respectively. With the help of surface-analytical methods it could be shown that oxygen or nitrogen were incorporated homogeneously in a certain depth region below the outermost surface. Some measurements of the outgassing behavior of these plasma treated surfaces will be shown. The results are discussed as originated from the surface modification by the plasma treatment and the creation of the implantation layer.     

Anti‐Eis‐Oberflächenbeschichtungen

Anti‐icing coating — optimization by means of plasma technology Ice on surfaces can significantly limit the function of devices and has to be removed by processes with high energy consumption. E. g., the formation of ice on rotor blades of wind turbines is not desired, on the wings of aircrafts it is even dangerous. With the aid of plasma technology, the Fraunhofer IGB has developed an anti‐icing coating for polymeric surfaces. Water‐repellent micro‐ and nanostructured coatings are applied to polymer foils made of impact‐resistant and shockproof polyurethane. Optimization of various process parameters has made it possible to produce ultra‐thin coatings, which reduces the ice's adhesion by over 90 percent. The new nanostructured foils open a wide range of applications.     

Beschichtungen für Zahnräder

Coatings for gear wheels In order to optimize the goal, steel gear wheels regarding load‐carrying capacity and wear, thin film coatings were tested. Different coating systems were examined numerically with the software ELASTICA® for their suitability. The characteristics of the coating systems were determined dependent on the material, its surface treatment as well as the diameters of relevant rolling partners. Differences were made between macroscopic rolling contacts between the teeth profiles and microscopic contacts with surface roughness and abrasion particles. First the four best suitable coating systems were deposited on simplified rollers and examined under different conditions. Two coating systems were determined, which show special suitability for the coating of the gear wheels. The first system is an a:C‐H coating with an CrN interlayer. The second system is an a:C‐H coating wtih an CrN interlayer on a plasma‐nitrided substrat (Duplex‐process). In order to protect the coatings on the teeth, their involute profile was provided with a tip relief. As gear wheel materials 16MnCr5, 42CrMo4 as well as the special steel ETG®88 were used. Two kinds of flow fats were used as lubricants and additional the unlubricated operation was examined. The gear wheels were tested at three different speeds on a test machine especially built for it. The testing routine was carried out in so‐called power‐stages. Each stage means a defined number of contacts and a certain Hertzian stress on the teeth profiles. With each stage the Hertzian stress was increased. The end of operation time is the beginning of cavitation pitting. The test results showed that in particular with the steel 16MnCr5 and 42CrMo4 the used Duplex‐systems leads to considerable increases of the load‐carrying capacity of the tooth flanks and the wear resistance. This increase was observed both with fat‐lubricated and with unlubricated gear wheels. The results for the special steel ETG®88 were less promising. An unlubricated operation could be made possible by the described coatings, which would not have been possible without the coatings. However the results are not as good as the results of uncoated gear wheels wih use of minimum fat lubrication. The reason could be an insufficient nitriding‐depth. For the selected steel the plasma‐nitriding parameters were investigated with the goal of optimized nitriding‐depth. Unfortunately up to the end of this project the gear wheels could not be treated with the optimized Duplex‐Process. At present the attempts with optimally plasma‐nitrided gear wheels are carried out. After that it would be possible to give recommendations for the plasma‐nitriding process and the necessary coating as well as the selection of the fat.     

Einfluss einer PVD‐Al‐Zwischenschicht auf die Eigenschaften eines thermisch gespritzten Wärmedämmschichtsystems nach Temperaturwechselbelastung

Thermal barrier coatings (TBC) generally consist of a metallic bond coat (BC) and a ceramic top coat (TC). Co–Ni–Cr–Al–Y metallic super alloys and Yttria stabilised zirconia (YSZ) have been widely used as bond coat and top coat for thermal barrier coatings systems, respectively. As a result of long‐term exposure of thermal barrier coatings systems to oxygen‐containing atmospheres at high temperatures, a diffusion of oxygen through the porous ceramic layer occurs and consequently an oxidation zone is formed in the interface between ceramic top coat and metallic bond coat. Alloying components of the BC layer create a so‐called thermally grown oxides layer (TGO). One included oxide type is α‐Al₂O₃. α‐Al₂O₃ lowers oxygen diffusion and thus slows down the oxidation process of the bond coat and consequently affects the service life of the coating system positively. The distribution of the alloying elements in the bond coat layer, however, generally causes the formation of mixed oxide phases. The different oxide phases have different growth rates, which cause local stresses, micro‐cracking and, finally, delamination and failure of the ceramic top coat layer. In the present study, a thin Al inter‐layer was deposited by DC‐Magnetron Sputtering on top of the Co–Ni–Cr–Al–Y metallic bond coat, followed by thermal spraying of yttria‐stabilised zirconia (YSZ) as a top coat layer. The deposited Al inter‐layer is meant to transform under operating conditions into a closed layer with high share of α‐Al₂O₃ that slows down the growth rate of the resulting thermally grown oxides layer. Surface morphology and microstructure characteristics as well as thermal cycling behaviour were investigated to study the effect of the intermediate Al layer on the oxidation of the bond coat compared to standard system. The system with Al inter‐layer shows a smaller thermally grown oxides layer thickness compared to standard system after thermal cycling under same conditions.     

Gefilterte Bogenbeschichtung – alte Probleme und neue Lösungen

Currently, the vacuum arc deposition (VAD) technique is well established in industry, primarily to deposit wear protective hard coatings such as metal nitrides and carbides onto tools and components. From the beginning of the industrial development of the vacuum arc deposition, it was obvious that the emission of macroparticles or droplets is a fundamental drawback of this coating technology. The emission is caused by the highly dynamic process of plasma generation and limits the fields of application significantly. Different methods have been proposed to minimize the macroparticle flux to the substrate surface. But the only way to hinder droplets from reaching the substrate reliable is to separate the plasma from particles by using curved magnetic fields. This filtered arc technique has proven its superiority of depositing high quality films compared to conventional arc applications in numerous laboratory tests. Current demands have stimulated new developments at the Fraunhofer IWS of more compact and higher productive filtered arc sources. One important application of ultra thin protective films is the topcoat on hard disks. In order to increase the storage density, the head‐to‐media spacing as well as the thickness of the overcoat has been reduced continuously. Until now, the thickness of the sputtered films was reduced to about 4 nm. The limit for this technology seems to be achieved. Filtered arc deposition is one of the most promising candidates for the deposition of thinner films – down to 1.3 nm with an even improved mechanical and chemical resistance. Another application area is the manufacturing of metallic lines and interconnections with high aspect ratios in the deep sub‐micron region in microelectronics. The excellent properties of this new filtered source for the deposition of conducting lines in microelectronics were been demonstrated. Actually, the technology for the subsequent deposition of barrier films and conducting wires is under development. Besides the micro technologies, there are a lot of applications requiring higher quality but not (yet) such a perfect film surface. Therefore, using a quite simple filter design – the so‐called Venetian blind filter – a filter unit was developed which can be used at the common industrial vacuum arc deposition machines. The filter does not reduce the deposition area, so the standard deposition processes can be used furthermore. With this filter, the number of droplets can reduced dramatically. A plasma transmission through the filter of approximately 20 % could be measured. Such filter module was realized and is in use now.     

Near‐Infrared‐Light‐Activatable Nanomaterial‐Mediated Phototheranostic Nanomedicines: An Emerging Paradigm for Cancer Treatment

Cancer is one of the most deadly diseases threatening the lives of humans. Although many treatment methods have been developed to tackle cancer, each modality of cancer treatment has its own limitations and drawbacks. The development of minimally invasive treatment modalities for cancers remains a great challenge. Near‐infrared (NIR) light‐activated nanomaterial‐mediated phototherapies, including photothermal and photodynamic therapies, provide an alternative means for spatially and temporally controlled minimally invasive treatments of cancers. Nanomaterials can serve as nanocargoes for the delivery of chemo‐drugs, diagnostic contrast reagents, and organic photosensitizers, and can be used to directly generate heat or reactive oxygen species for the treatment of tumors without the need for organic photosensitizers with NIR‐light irradiation. Here, current progress in NIR‐light‐activated nanomaterial‐mediated photothermal therapy and photodynamic therapy is summarized. Furthermore, the effects of size, shape, and surface functionalities of nanomaterials on intracellular uptake, macrophage clearance, biodistribution, cytotoxicities, and biomedical efficacies are discussed. The use of various types of nanomaterials, such as gold nanoparticles, carbon nanotubes, graphene, and many other inorganic nanostructures, in combination with diagnostic and therapeutic modalities for solid tumors, is briefly reviewed.     

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.     

Increase of load‐carrying capacity of masonry with textile reinforced rendering / Erhöhung der Tragfähigkeit von Mauerwerk mit textilbewehrtem Putz

Contemporary externally bonded structural upgrading schemes for masonry structures employ Fiber Reinforced Polymer (FRP) systems (a technique that was extended from concrete to masonry structures) and technical textiles (structural fiber grids) embedded in inorganic matrices. The latter account for a multitude of systems depending on the type of grid – fiber material, bundle treatment (dry, coated or even impregnated), grid geometry, manufacturing method etc. – and matrix – binder (e.g. cement or lime), rheology etc. – resulting in the derivation of many different acronyms (FRCM, TRM, CMG, IMG or other – see for definitions below). The mechanical behavior of such systems and their interaction with different substrates may vary significantly (e.g. dry vs. impregnated fiber grids embedded in mortars). This paper aims to summarize all reported efforts to increase the load‐carrying and/or deformation capacity of unreinforced masonry walls against in‐plane loading and second‐order phenomena (eccentric compressive loading).     

Kalte Normaldruck‐Jetplasmen zur lokalen Oberflächenbehandlung

Cold non‐thermal plasma jets for local surface treatment under normal pressure Plasmas at normal pressure are of considerable interest for surface technology because the industrial application requires no vacuum devices. Among other approaches, cold non‐thermal plasma jets represent an emerging technique to generate plasmas at normal pressure with attractive advantages. They allow ambient process temperatures and require only moderate operating voltages (1.5‐2.5 kV). They offer the advantage that the treated surfaces are not placed between the electrodes thus favoring local treatment of non flat, structured 3D surfaces. Moreover, the dimension of the sources is scalable and their integration into automated processes is simple. A capacitively coupled version (27.12 MHz) of a cold plasma jet suitable for surface treatment at atmospheric pressure is presented along with its plasma physical and technical properties and a series of successful applications, including plasma activation of surfaces for increasing printability, adhesion control, surface cleaning, microfluidics, decontamination, its use in plasmamedicine and for deposition of thin SiO₂ films as protective coatings. The device allows the operation with rare gases (e.g. Ar) and reactive gases as N₂, air or admixtures of silicon‐containing compounds.     

Verallgemeinerungsfähige Merkmale und Besonderheiten des Sprühkompaktierens

Characteristic Features and Specific Qualifications of the Sprayforming Process to be Generalized The solidification and cooling process of spray formed materials predominates the extent of any segregation and separation process, which is conducive to avoid macro‐segregation and to diminish concentration of alloying components at the grain boundaries. The risk of coarse porosity or of hot cracking is reduced significantly by the momentum of the mass flow during spray deposition. This means that those materials which e.g. during the casting process tend to establish strong segregation effects and cavities and/or hot cracks as well as those which tend to create filaments of carbides, nitrides or sulphides during rolling can be generated by the spray forming process in large dimensions with chemical homogeneity and without any of those defects. A characteristic feature of spray formed materials is the fine equiaxed grain structure and the high ductility. Specific features of this new free forming process will be discussed.