Abschirmung von Kunststoffen durch Beschichtung im Vakuum

Vacuum coating for shielding of plastics Shielding coatings can be deposited selectively on plastic housings by vacuum assisted processes. The mechanical properties of the polymer material are not affected. Uncoated areas maintain their visual appearance, i.e. refinishing operations are not required. Due to their high electrical conductivity, Aluminium and Copper films provide a high shielding effectiveness for electromagnetic waves. They are applied successfully to devices in a wide variety of industrial sectors if electromagnetic compatibility (EMC) has to be ensured. If applications under harsh environmental conditions are encountered, protective coatings deposited during the same vacuum cycle, are the best solution. Similarly, combinations of properties like shielding and solderability can be achieved by vacuum coating, e.g. with Copper / Tin layers. In case that for example transparency in the visual regime is specified in conjunction with dissipation of electrostatic charges or with attenuation of high – frequency interferences, indium tin oxide (ITO) films are well proven.     

Haftfeste Direktmetallisierung von Kunststoffen durch Beschichtung mit Ionen

Direct metallization of plastics by high powerimpulse magnetron sputtering Even if polymers are today industrially used for decades the direct metallization of plastics is still a hot topic for research and development. Especially in light of the ban of hexavalent chromium an increasing demand for well‐adhering plastic metallization arises. High power impulse magnetron sputtering HIPIMS is a recent technology that can offer a high potential for successfully solving this challenge. This article focuses on the direct metallization of plastics by HIPIMS. In the frame of the investigations any pretreatment was ignored and the different polymers were directly under vacuum metallized. Compared to conventional mid‐frequency sputtering a significant improvement in adhesion was shown for different polymers. In detail the metallization of Plexiglas (PMMA) was investigated, since this polymer is highly challenging with respect to plasma processes. Due to the UV radiation damage of PMMA during plasma deposition direct metallization is usually not possible. Using ionized deposition it was possible to directly metallize the substrates with excellent adhering films without any interface layers or special pretreatments. The characterization of the substrate‐coating interface showed that for the well adhering films a cohesive fracture, i.e. a fracture within the polymer occurred.     

Neuartige dekorative Farbschichten durch Plasma‐Beschichtung

Novel decorative color coatings using plasma deposition The market does not stop to demand for novel products. Only those who offer innovative products will explore new segments of the market and will not loose against the cheap suppliers from far eastern countries. This is even more important in the field of surface technology. Many products would not be competitive without plasma technology. Companies changing surfaces with plasma technology expect a noticeable growth between 20 and 50 % within the next years [1]. The deposition of thin layers using plasma makes it possible to obtain highly brilliant color coatings, specially mixed color effects (rainbow like) as well as color changes depending of the observation angle. These optical special effects would not be feasible with common painting techniques. Thus plasma deposition opens a new field for surface coating. In these layers the colors are created via interference effects of the light being used for illumination. They are called interference colors, well known to the most of us from thin oil films on a wet street.     

Plasmaunterstützte DLC‐Beschichtung von Kunststoffen

Plasmaenhanced deposition of DLC on polymers The formation of diamond‐like carbon (DLC) coatings on polyethylene (PE) is accompanied with the formation of an interlayer. Therefore the original surface structure of the plastic material is reorganized and gradually changes into the disordered structure of the DLC layer. Before DLC can be deposited in a hydrocarbon plasma with the PECVD method, all substrates are cleaned using an oxygen plasma. This first step is extremely important for the growth of the DLC layer since the sample's surface is already ablated and partly flattened. Plastic materials can be successfully improved in stability and provided with extra properties and new functionalities due to the deposition of DLC. First microscopic explanations for the macroscopic phenomena and application‐relevant questions have been identified. In spite of this limits of production are also addressed. Methods shown here will now be adapted for other materials and coatings.     

Plasmavorbehandlung und Beschichtung von Kunststoffolien. Teil 1: Beschichtung von unbehandelten Kunststoffolien

Plasma Pretreatment and Coating of Polymer Films. Part 1: Coating of Non-treated Polymer Films The food packaging industry demands cheap polymer films possessing a high barrier against permeation of gases, moisture and flavor. Candidates for the most successful materials fulfilling these requirements are vacuum web coated biaxial oriented polypropylene (BOPP) films containing a thin inorganic barrier layer. For a good adhesion of the barrier layer on the BOPP films, the polymer film must be pretreated. The industry uses the Corona atmosphere plasma. This work is separated in three parts. The first part describes the experimental setup and the properties of vacuum web coated layers on polymer films. The next part contains the results of the systematic modification of polymer surfaces by atmosphere and low pressure plasmas. The influence of the surface properties on the final functionality of the coated films is given. In the last part, the discussion of the results of the first and second part reveals systematic relations between the production parameters of the high barrier films and their final functionality. These results firstly reveal the adhesion mechanism of the inorganic barrier layers of the polymer films and the necessary surface properties of the polymer films, in order to get cheap high barrier films by vacuum web coating.     

Lichtbogengestützte Prozesse zur Beschichtung von Kunststoffen

In the past ten years plasma enhanced deposition techniques have gained much increased importance due to the possibilities of improving and developing new film properties. Among these properties are adhesion and film structure. One of the new plasma assisted film deposition techniques is the Arc enhanced thermal evaporation technique. This new deposition technique and the film properties that are possible with this technique and its applications are described in this paper.     

Schwerpunkte und Grenzen in der Behandlung von Modellen für Computersysteme durch Simulation und durch analytische Verfahren

Zusammenfassung Die vorliegende Arbeit hat zum Ziel, die Anwendbarkeit von analytischen Verfahren und der Simulationstechnik zur Behandlung aktueller Problemstellungen in der Praxis der Leistungsanalyse von Computersystemen zu diskutieren. An einem Beispiel wird dann das uns für viele Fälle geeignet erscheinende hybride Verfahren gezeigt und die damit mögliche Flexibilität erläutert; gleichzeitig weisen wir aber auch auf die dabei entstehenden Probleme hin.

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Summary The central interest of this work is to discuss the applicability of analytical and simulation methods to practical problems in performance prediction of computer systems. With an example we show the flexibility but also the existing problems of a hybrid technique.

     

Plasmagestützte Beschichtung von Bauteilen bei niedrigen Temperaturen

The deposition of wear resistant coatings is possible nowadays at low temperature by the Plasma Assisted CVD process using metall organic precursors. Thus a coating of temperature sensitive materials like aluminium, magnesium and polymer at low temperature is realised. The wear resistant coatings TiCN and ZrCN were deposited on light metals at a temperature below 160°C. The mechanical properties of the layers show the potential of the coatings for parts with wear and friction. The surface hardness, the abrasive wear and the friction value are improved compared to the properties of substrate material and steel. Transparent BCN‐coatings can be used as scratch resistant coatings on polymers like polycarbonate. The layers offers good transmission by high hardness.     

Thermochromes VO2 für die Beschichtung von Architekturglas

In recent years vanadium dioxide films were discussed as thermochromic window coatings. Up to now it is not possible to deposit films, the properties of which are well-suited for technical application. In the following properties of reactively rf sputtered VO₂ films on a laboratory scale are reported. Besides optical measurements, analytical techniques as photoelectron spectometry, electron energy loss spectrometry, and secondary ion mass spectrometry are applied to VO₂ films for the first time. We expect that these investigations will result in a better understanding of the metal-to-semiconductor transition, and other film properties as for example electronic defects and diffusion profiles at the interfaces and their effects on the band structure, thus aiming at superior film processing. In the following a survey over first results is presented.     

Kunststoffoptiken mit Antireflex‐ und Antibeschlageigenschaften durch Plasmaätzen und Beschichtung

Plastic optics exhibiting anti‐reflection and anti‐fogging properties produced by plasma etching and coating Plasma treatments are capable to generate antireflective surface structures on various polymers. On PMMA a self organized surface with nep‐like bumps exhibits excellent optical properties. Many other materials like polycarbonate, zeonex and lacquers can be etched after depositing a very thin initial layer to form a more holey structure. These surfaces attain high transmission values too and can be better stabilized by coatings than the nep‐ structure on PMMA. Interesting for practical applications are hydrophilic top‐layers to provide anti‐fogging properties in combination with improved transmission.     

Verbesserung der knöchernen Integration von Schanz’ Schrauben durch eine Poly(D,L‐laktid) Beschichtung

Improvement of bony integration of Schanz’ screws by means of a Poly(D,L‐laktid) coating Pin track infections and pin loosening are major complications in fracture treatment by means of external fixation. In this study, the influence of Poly(D,L‐lactid)‐coating on osseous integration of Schanz screws was analysed during bone healing. In sixteen sheep, osteotomies of the right tibia were stabilized by means of monolateral external fixators. In addition, mechanically unloaded Schanz' screws were inserted. One half of the implanted screws was coated with Poly(D,L‐lactid). After nine weeks in vivo, the screws were extracted, rolled on blood agar plates and microbiologically analysed, followed by histological, immunhistochemical and histomorphometrical analyses of the pin tracks. Even though no clinical signs of infection were observed, micro biological evaluation indicated a contamination by Staphylococcus aureus of 15 % in the coated screws and of 29 % in the uncoated screws. The histological analyses showed an improved osseous interagtion in the coated screws (p=0,0006) compared to the uncoated implants. In histomorphometry, the group of the uncoated screws showed an increased bone remodelling (p = 0,006) and an increased osteoclast activity (p = 0,019). Mechanically loaded screws had increased callus formation at the pin exit site (p = 0,048). The poly(D,L‐lactid) coating of Schanz' screws seems to enhance the osseous integration by reducing cortical remodelling and osteoclast activity.     

Beizung von BIOHOCH®-Reaktoren als Vorbehandlung für eine Beschichtung

Pickling of Steel Tanks for Use in Biological Water Purification Plants as a Pretreatment to the Application of an Organic Coating High-level tanks made from structural steel, so called BIOHOCH®-Reaktoren for biological purification of chemical waste water, had to be protected against corrosion by an organic coating. After the usual pretreatment, which means cleaning of the steel surface by sand or furnaceslag blasting, pittinglike corrosion was observed in two cases. Therefore, the required grade of surface preparation was not available. Nevertheless, to get good preconditions for a sufficient service life, both tanks with a volume of about 20 000 m³ were pickled in such a manner, that the final furnace blasting operation furnished the presumed white metal state. The problematic nature of organic coatings, which has recommended the pickling of the steel surface, is discussed. The selection, realization and controlling of this treatment are specified.     

CVD ZrO2‐Beschichtung von Fasern bei Normaldruck

Atmospheric pressure CVD of ZrO₂ on fibers Two different Chemical vapor deposition processes on fiberbundles (number of fibers a few thousand, diameter of the single fiber ≈10 µm) with zirconium dioxide at atmospheric pressure have been developed (AiF project 12783N): 1) ZrO₂ thin films on SiTiC fibers were grown by flame‐CVD using zirconium dipivaloylmethanate or acetylacetonate as precursors. The total deposition rate of 3·10^–5 mol·m^–2·s^–1 was achieved in a 4 cm long deposition zone. 2) In a new atmospheric pressure CVD process the deposition took place via hydrolysis of zirconium dipyvaloylmethanate in water vapor. The total deposition rate of 7·10^–6 mol·m^–2·s^–1 has been achieved in a 60 cm long pilot setup. This value allows to deposit continuously a 10 nm thick ZrO₂ films on fibers moving with velocity of 30 m/h. The deposition rate demonstrated in this work is the highest achieved so far for ZrO₂ CVD at atmospheric pressure.     

Innovative magnesiumgerechte Gießtechnik

Innovative Magnesium adepted Casting Technology A main reason for the relatively small use of magnesium alloys as construction material is the demanding casting technology. The reactivity with ambient atmosphere and several other materials, the low specific heat values like heat capacity and heat of fusion, the small melting range and comparatively high liquidus temperatures of alloys with improved properties demand the optimizing of excisting and development new casting processes. In the scope of the Thrust Research Program SFB 390 “Magnesium Technology” founded by the German Research Council (DFG) the project B10 “Casting Technology” is engaged in the development and optimisation of casting techniques for Mg‐alloys. The emphasis of the developments in the Institute of Materials Science (IW) of the Universtity of Hanover is set on reliable, low contaminated processes of melting, melt handling and mould filling for the production of low defect structural components, even dealing with alloys difficult to handle.     

Beschichtung von dreidimensionalen Substraten mit einem magnetfeldunterstützten Mikrowellen-Plasma bei Raumtemperatur

Microwave plasmas exhibit a high electron density and energy as compared to glow discharges at direct current and high frequency (13.56 MHz). Electron cyclotron resonance is reached by magnetic fields, allowing a stable glow discharge at low pressure (～ 1 Pa) and power input. In chemical vapour deposition the magnetic fields can be used in conjunction with the gas supply to guide the plasma and the deposition. The microwave power is transmitted via a helix slow-wave structure. It is demonstrated that an effective inner coating of polyethylene bottles is possible. With amorphous Si:H-films from the deposition of SiH.₄ in Ar a highly effective diffusion barrier up to 93% for hexane/polyethylene is obtained.