Plasmachemische Mikrostrukturierung von polymeren Oberflächen für Pharmazie und medizinische Diagnostik

The plasma masking technology is a method applied to get locally selective, physical‐chemical structuring on nearly all plastic surfaces in the micrometer range. Such generated chemically functionalised, polymer‐based surface structures are suited for use as biochips and will promote the application of low priced polymer materials with appropriate modified surfaces. Provided with a biochemical treatment for analytical methods, they are used in medical diagnostics and pharmaceutical drug research. This technique supports the increasing application of high throughput screening systems (HTS) including micro arrays for genomics and proteomics as well as the development of cell biochips.     

Ionen- und plasmagestützte Verfahren der Oberflächentechnik für die Randschichtbehandlung von Leichtmetallwerkstoffen

Surface engineering of light weight materials with ion- and plasma-assisted methods Increasing applications of light weight materials are expected in the future. Pursuing this trend surface engineering of these materials – especially ion- and plasma-assisted methods – swill be of increasing interest to enhance their wear and corrosion resistance. In a research co-operation some promising methods were examined on different aluminium and titanium alloys to assess their potential to increase the surface properties. Among these were magnetron sputtering of chromium nitride, ion beam assisted deposition of Cr/CrN and Al/A₂O₃ layers, ion implantation and ion beam assisted nitriding. Compared to the steel substrates the assessment of the mechanical properties such as the critical load of the scratch test of the coated light weight materials is different. Furthermore, it could be shown that both spherical section and glow discharge optical spectroscopy are useful methods to characterize the near-surface zone influenced by ion implantation.     

Anorganisch‐organische Hybridschichten für die Entspiegelung optischer Oberflächen

Inorganic‐organic hybrid coatings for antireflection of optical surfaces The application of nanostructures for optical surfaces has been discussed since antireflective nanostructures have been discovered on the eyes of night‐flying insects. On injection molded plastic lenses, antireflective nanostructures can easily be produced by plasma etching. The procedure has now been adapted to vacuum evaporated organic layers. Complex coatings composed of inorganic layers and organic nanostructures are especially suitable for realizing broadband antireflection properties on glass lenses.     

Schützende Oberflächen für metallische Werkstoffe

Coatings for Metallic Materials . The most important coating techniques are characterized and critically described. Among the various possibilities to protect the surface of metallic materials against mechanical, chemical or mechanical-chemical attack, the coatings which are looked upon are ranging from metallic coatings over nonmetallic anorganic to the organic ones.     

Präparation von nichtmetallischen Werkstoffen für die lichtmikroskopische Untersuchung

Preparation of Non-Metallic Materials for Examination under an Optical Microscope Tests carried out show that the comparatively elaborate procedures necessary to produce thin polished sections can in many cases be satisfactorily replaced by more economical machining techniques. Considerable time and cost savings have been made possible by preparing monolithic specimens using a high-speed milling machine and microsections using a low-speed saw. This applies particularly to the use of the low-speed saw in quality control for components made of glass fibre reinforced polyesters. Another important application is the preparation of specimens of synthetic resin-impregnated graphite for corrosion resistance tests using a high-speed milling machine.     

Plasmapolymerschichten als Basis für maßgeschneiderte funktionale Oberflächen

Plasmapolymer coatings for tailor‐made functional surfaces The tailoring of surface properties via polymer coatings is currently a strongly pursued topic in various fields ranging from microsystem technology to bioanalytics. A precise tuning of surface properties, however, is only possible if chemically well‐defined processes are used that usually require reactive surface moieties to which molecules can be coupled. In this contribution we summarize studies that aimed at the modification of inert surfaces. For this purpose reactive groups at the surfaces are generated by plasma polymerisation of allyl amine which results in layers that contain amino groups. Initiator molecules for free radical polymerization processes are then coupled to these amino groups resulting in surfaces from which polymers can then be grown via surface‐initiated polymerization. Using these processes, polymer monolayers with very different properties can be generated by simply using different monomers.     

Die thermische Stabilität von Eigenspannungen in kugelgestrahlten Oberflächen

Thermal Stability of Residual Stresses in Shot Peened Surfaces . In industry shop peening represents a well-known process to improve the fatigue properties of metallic components. However, the beneficial effect of the induced compressive residual stresses can be reduced if a component is subjected to higher temperatures during service. In this work the relief of the residual stresses as a function of time and temperature is calculated for a 12 %-chromium steel. Specifically, the results can be used for the prediction of the stress relief behaviour of gas turbine compressor blades. This model can also be applied to the determination of the mechanisms which are responsible for the residual stress relief. At temperatures above approximately 300 °C in this material the dominating mechanism is diffusion controlled creep whereas at lower temperatures the stress relief is caused by logarithmic creep.     

Plasmavorbehandlung problematischer Kunststoff-Oberflächen für die Lackierung

Plasma Treatment of Problematic Plastic Parts before Painting There are some well known difficulties in coating or painting polymers without any surface preparation. Reasons for that may be contaminations of the surface by human perspiration or polymer additives. These contaminations can be responsible for poor adhesion between coating and polymer surface. On the other hand a lack of wetting and spreading may cause adhesion-problems, especially with water based coatings. Both problems (contamination and lack of spreading) can be solved by low pressure-plasma treatment. In this paper some examples will be presented, that demonstrate the potential of low presure-plasma treatment in adhesion enhancement on the one side and the necessity of suitable quality control methods for optimisation purposes on the other side.     

Beurteilung der Zuverlässigkeit von Schmiermitteln für die Feinwerktechnik

Assessment of the Reliability of Lubricants for Precision Machinery. The critical examination of the reliability of lubricants for instruments and precision machinery needs first the recognition of all the parameters influencing the efficiency of the lubricants. Afterwards these parameters have to be classified according to their significance of the application of the instruments and precision machinery. These numerous influences cause unexpected and very complicated interactions which often can only be recognized, if the instruments and precision machinery are tested under practical conditions. The very small quantities of lubricants used in the instruments and precision machinery require new techniques for examining the lubricated bearings. A well equipped laboratory and a serious planning of the tests as well are therefore indispensable.     

Untersuchung von Oberflächenschutzschichten von Gasturbinenlegierungen

Investigations on protective coatings on gasturbine alloys. It has been found by investigations of specimens of a combustion chamber pilot plant and also by experiences with gasturbines that aluminide or chromium aluminide coatings are only slightly protective under working conditions of industrial gasturbines. Chromium coatings have a distinctive better protective efficacy and are surpassed in this quality by silicide coatings. It was possible to give information on the development of silicide phases on Nimonic 105. Under the conditions of corrosive attack a surface layer of Nickelolivine is formed and the silicide phases are changed in direction of ternary phases. Even when chromium sulfides are formed in the silicide layer the specimens are stable under the test conditions. By investigations on an airfoil made from B 1900 with a protective coating of Aluminium and Silicon the presence is shown of a ternary Laves phase with Silicon.     

Streuung der Werkstoffestigkeit und die Wahrscheinlichkeit für das Versagen von Probenstäben an ausgesuchten Beispielen

Scattering of Strength and Probability to Failure of Smooth Test Bars – on Selected Examples . The influence of scattering of material properties (distribution density function f) and of the loading spectrum (distribution density function g) on the probability to failure is discussed. For the distribution density functions f and g, simple model functions (Gaussian function, δ-function) were used. It is shown that in typical design situations, a small reduction of the scatter of the material properties may reduce the probability to failure to some orders of magnitude. The width of the loading spectrum is shown to be less important compared to the width of the scatter of the material properties. For materials with a large scatter of properties e.g. ceramics, the probability to failure is really high, even if a large safety factor is used. A satisfactory reliability for designs made from such materials can be reached, if lower limits of strength can be guaranted – e.g. applying advanced methods of material testing. Under this special condition, the width of the loading spectrum and the safety factor gains a large influence on the probability to failure.     

Laserakustik für Schicht‐ und Oberflächenprüfung

Laser‐acoustics for Testing Coatings and Material Surfaces A laser‐acoustic test method is presented, which can be used for the non‐destructive characterization of coatings and material surfaces. The method measures the dispersion of surface acoustic waves induced by short laser pulses. The technique is based on the fact that the propagation velocity of the wave depends on the frequency in coated and surface modified materials. Measuring the dispersion of the surface acoustic wave enables to determine important properties of the material surface. Three examples demonstrate that the laser‐acoustic method can solve very different problems of surface engineering. The wear resistance of diamond‐like carbon film with a thickness of few nano‐meters was evaluated. The elastic modulus of thermally sprayed coatings which are typically some hundred micro‐meters thick was measured, which allows to conclude on the defect structure of the coatings. The depth of sub‐surface damage layers in semi‐conductor materials was determined, which are created when the wafer is sliced from the ingot.     

Oberflächenspannungsmesstechnik für den Prozesseinsatz

Using Surface Tension Measurement in Applications When cleaning surfaces it is crucial for the process stability that the optimum surfactant concentration is maintained. The concentration of free surfactants can be measured by determining the surface tension. SITA Messtechnik has developed an innovative sensor based on the bubble pressure method. This sensor makes it possible to continuously measure surface tension with a high reliability. With this application for monitoring cleaning baths the potential to save money arises in regard to the use of raw materials, waste disposal and the costs resulting from undiscovered production failures.     

Der Lasermikrospektralanalysator als Anregungsgerät für die Emissionsspektralanalyse

The Laser-Microprobe as an Excitation Device for Electrochemical Analysis . The laser-microprobe, which has been commercially available for some years, is specially suited for the purpose-oriented microanalysis. The equipment set-up permits the laser-microprobe or the spark unit to be used as excitation device with out change. The low initial cost compared to other equipments of similar efficiency will in the future ensure a wider use of this multi-purpose equipment in microanalysis, despite some inherent imperfections.     

Die Bedeutung der Werkstoffauswahl für die Gebrauchstauglichkeit von Chemieapparaten Auswahlkriterien und Prüfverfahren

Materials selection and service properties of chemical plants – criteria of selection and testing methods . Materials selection and technical design – operating temperature and limit of stress – corrosion and abrasion resistance – corrosion testing methods – testing of corrosion behavior of welded joints.     

Plasmaprozesse für funktionelle Polymeroberflächen

Plasma Processes for Functional Polymer Surfaces Plasma‐based processes were originally developed for microelectronics, but have exceeded this limits since then. Today the plasma technology is a key technology with numerous applications. A great technological potential can be seen particularly in the field of surface modification because in a plasma any organic bond can be broken and thus reactions can be initiated which cannot be carried out wet‐chemically. Besides, the small depth effect leaves the bulk properties of the material unchanged. This article points out the fundamental characteristics of non‐thermal low pressure plasmas and shows some procedure examples, which were developed at the Fraunhofer‐Institut für Angewandte Polymerforschung (IAP). Finally analysis methods (XPS, labeling techniques) are presented, which are essential for an effective development of plasma processes.