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.     

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.     

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.     

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.     

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.     

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.     

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.     

Verringerung der Belagbildung durch beschichtete Oberflächen

Fouling on heat exchangers is a well known but unsolved problem in the area of heat transfer. This additional layer could be formed by crystallization, particles, biological systems or by chemical reaction. It was estimated that the costs due to fouling in industrialized countries are about 0.25 % of the GDP (6.2 bn. Euro for Germany, 2008). Due to the isolating effect of the fouling layer, the total heat transfer of the equipment is declined. To maximize the operation time between cleaning cycles of the heat exchanger and to minimize cleaning time, a defined change in the molecular interaction between fouling layer and heat transfer surface is required. PACVD (Plasma Assisted Chemical Vapor Deposition) coatings can realize this and have shown their potential to mitigate fouling. Especially modified DLC (Diamond Like Carbon) were investigated. The operation time of a heat exchanger in lab scale could be extended by the factor of 10 with a tailor made surface.     

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.     

Raster-Tunnel-Mikroskopie zur Untersuchung und Modifizierung von Festkörperoberflächen

We present a short review of the capabilities and prospects offered by the scanning tunneling microscopy (STM). Ultra-high vacuum — in general not necessary for STM operation at all — ensures without doubt well-defined surface and tunneling conditions. The latter are especially important for atomic resolution and spectroscopic applications. Shining examples selected from an almost exhaustiveless amount of original papers illustrate the new quality in local surface structural analysis, spectroscopy and modification achieved due to the establishment of STM and related scanning probe techniques.     

Einfluß der Oberflächenbeschaffenheit auf die Schwingfestigkeit von Aluminium-Druckguß

Effect of Surface Condition on Fatigue Strength of Die-Cast Aluminium Surface processing like milling or shot peening involves modifications of the surface and subsurface condition of a material that can be described by changes of the residual stresses, the hardness, and the surface roughness. Moreover, there is the possibility of introducing additional surface defects. In this paper the influence of these modifications on the fatigue behaviour of the aluminium die-casting alloy GD-AlSi8Cu3 is presented. S-N curves are determined for four surface conditions produced by milling, shot peening, and a combined treatment. The improvement of fatigue limit by shot peening is confirmed for this material. The additional effect of mean stresses is determined. Investigations of the fatigue fracture surfaces show that pores and pipes as well as surface defects induced by shot peening act as fatigue crack initiation sites.     

Heliumlecktestgeräte für die Qualitätsprüfung von Gehäusen für Vakuumverdichter

Helium leak test devices for the quality inspection of housings for vacuum compressors The well‐known and wide‐spread helium leak test method is a safe and fast quality testing method for construction units of any kind. Due to its safe examination and the short time of examination it is predominantly inserted into automated production lines as e.g. in the automobile supporting industry up to the examination by Airbags and rims of wheel. Likewise in addition, for the construction units, machines and devices of the vacuum engineering. From this the demand results simple and in particular economical devices for the helium leak test of construction units with small numbers of items of under 200 pieces per day. For these manufacturing profiles economical ways for the helium leak test are pointed out.