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.     

Bedeutung von Prüfmethoden für die Auslegung verschleißbeanspruchter Bauteile

Test Methods and Dimensioning of Tribologically Loaded Parts Owing to the complexity of tribological systems the testing of wear components is of particular significance. Here is an effort to show the advantages and disadvantages of product tests, component tests and model tests. Even with model tests good results for the products are attainable when relevant parameters are systematically varied. Hereto some examples are given.     

Einsatz von Mikroplasmen für die Herstellung von Silizium‐Mehrlagenaufbauten

Micro Plasma Processes for MEMS Packaging The encapsulation of MEMS devices can be difficult, since released micromechanical parts (e.g. membranes, valves, and cantilevers) tend to stick to the surrounding surfaces. Area‐selective surface modification is a new approach, developed by the Fraunhofer‐Institute for Surface Engineering and Thin Films (IST), to overcome these problems. From a more general point of view, area‐selective surface tailoring with microplasmas is an attractive topic for micro systems production. The business transfer of the technique by implementation into the SU SS mask is currently being evaluated.     

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.     

Ellipsometrische Charakterisierung von C‐Schutzschichten für die Speichertechnologie

Spectroscopic Ellipsometry is a fast, non‐destructive and reliable method for characterizing thin films, based on interaction between incident light and a multilayer system. For our investigations, light in the visible spectral range has been used to characterize protective carbon coatings with thicknesses of 2‐7nm on magnetic hard disks. The specific disk layer stack has been described with an adequate one‐layer model. With regard to an accurate analysis of the covering carbon coating a reproducible procedure for determining the underlying metallic material has been developed. The measured ellipsometric parameters (ψ, Δ) display a linear dependence on carbon film thickness which shows an appropriate application of the used model down to a thickness of 2 nm. By means of simulation calculations, criteria for the selection of optimized wavelengths with respect to film characterization has been established. Furthermore, an increasing extinction coefficient κ with rising nitrogen content in the carbon coating could be stated. Apparent time instabilities in the determination of layer thickness d and extinction coefficient κ of the carbon film could be explained as due to adsorption processes on the surface.     

Prüflecks für Schnüffel‐Lecksucher

In the testing of leak tightness and in the localisation of leaks by means of a test gas, proper operation and sensitivity of the employed instrument must be checked by a certified reference leak. In the so‐called sniffer mode of operation, the component under test is filled to overpressure with the test gas, so that in case of a leak there is a gas flow from the component to atmosphere. The atmospheric gas is sucked by the instrument and probed for its test gas content. For checking the instruments performance, commercial test leaks are available for various gas species, which deliver a well‐defined leakage. Construction and properties of such a test leak are described. The leak has an internal gas reservoir and a capillary as leak element. Because the inlet pressure at the capillary is kept constant by a pressure controller, the leakage remains constant over several years despite the gradual pressure decrease in the gas reservoir. The calibration of the leakage via the volume flow rate is described in detail. The volume flow rate can be measured by a liquid drop in a measuring capillary as well as a displacement piston in a dosing syringe.     

Ionenbeschuss von Polymeren für die Medizintechnik

Ion Bombardment of Polymers for Biomedical Applications Ion implantation, a standard technology in the semiconductor industry, is also used since the 1960s for biomaterials. In the following, a variation of the method is presented for illustrative — plasma immersion ion implantation (PIII). In PIII treatments process times of less than a minute are found to be sufficient to change the surface energy at least for several weeks. In addition, a modified coefficient of friction, wear and topography can be obtained, with reduced wear rates and an increased roughness having a positive impact on the biocompatibility and the bioactivity. For combined coating and implantation processes with simultaneous energetic ion bombardment, an excellent adhesion is obtained even at room temperature. In addition to the formation of photo‐active surfaces, which may have an antibacterial effect here also an osteoinductive topography can be achieved.     

Umformtechnik für die Produkte von morgen

Metal forming for the products of tomorrow An increasing global competition, shorter product lifetimes and a higher demand for functionality, environmental soundness and quality, represents a large challenge for metal forming. Due to newly developed processes, metal forming at the same time has the possibility to expand into areas at present controlled by other manufacturing methods.     

Plasmapolymerisation für die Hartbeschichtung von Kunststofflinsen

The use of plastic as a substrate material for optical lenses has been increasing in importance due to smaller density, simpler machining and lower price. However scratches present a major problem wherever the lens surface is exposed to the environment. Various processes have thus been developed to protect the surfaces with hard coatings. The most common technique is the dipping process while spinning or spraying are other methodsto apply lacquer. Common to all these techniques are the required post treatments such as drying and heat or UV curing. Safety considerations as well as the long processing time and the handling required between the different steps, gave rise to the development of new technologies. Plasma polymerization, a technology relying on plasma enhanced chemical vapor deposition (PECVD), is used to deposit dense organic layers with reproducible, well defined surface properties. In contrast to dip coating, plasma polymerization even coats strongly curved structures with good uniformity. This is important for bifocal or trifocal lenses, featuring sharp edges on the surface. Due to the wide range of refraction indexes (about n = 1.5–1.8) available by using different monomers, even the latest high index materials can be coated without disturbing interference fringes. After a survey of plasma polymerization basics, some aspects of industrial equipment and processes for ophthalmic applications are presented. An outlook into the future of plasma polymerization for optical applications concludes the paper.     

ta‐C beschichtete Werkzeuge für die Trockenumformung von Aluminiumblechen

ta‐C coated tools for dry forming of aluminum sheets The suitability of ta‐C coated tool surfaces for sheet forming of aluminum alloys was examined by strip‐draw testing. It was shown that ta‐C coatings, which are known as DLC coatings with superior wear resistance are also favourable concerning the anti‐adhesive behaviour. In attempts with AlMg5Mn‐ as well as Al99Mg1‐sheet materials several hundred sheets could be formed without noticeable aluminum adhering at the ta‐C coated tool surface. Neither the coefficients of friction nor the surface qualities of the aluminum sheets worsened during the observed period. Compared with tests of uncoated tools in combination with lubricants, the dry ta‐C coated tool behaves comparable with a good lubricant. In a real clinch test with aluminum sheets the positive results from strip‐draw experiments were confirmed. Using ta‐C coated clinching stamps and no lubricants a large number of clinching processes could be performed without noticeable adhering and increase of stripping forces.     

Werkstoffkennwerte für die Lebensdauerberechnung von Strukturen aus Stahlfeinblechen für den Automobilbau

Materials Data for Fatigue Life Calculation of Steel Sheet Structures for Automotive Engineering Within a joint project of the steel and automotive industry 17 steel sheet materials for automotive engineering in various delivery and forming conditions at temperatures of –40 °C, 22 °C and 100 °C were investigated. In the course of 37 test series strain controlled fatigue curves to crack initiation and stress‐strain‐curves under monotonic and cyclic loading were determined. All experimental data, hysteresis loops and determined cyclic properties are available in a database. A correlation between the mechanical properties from tensile tests and the properties from strain controlled cyclic experiments seems to be possible.     

Die Entwicklung von Strukturmaterialien für die Kernfusion

The Development of Structural Materials for Fusion Reactors Structural materials for the First Wall and breeding blankets of future fusion reactors will be exposed to intense neutron irradiation and thermal wall loading. Fusion‐specific selection criteria for the proper choice of materials are primary damage parameters, a minimum of produced radioactivity (low activation materials) and also conventional properties like strength and corrosion resistance. Three major material groups are under discussion: ferritic‐martensitic 7–12%Cr steels, SiC‐fiber‐enforced compound materials of type SiC_f/SiC and specific vanadium‐based alloys. A short status of development and a survey on necessary further research work is given to fulfil the material requirements for the construction of the next fusion reactor devices. Finally the necessity for an appropriate 14 MeV neutron source as test bed for the material development is mentioned.     

Modellierungskonzept für die Versagensbewertung von Laserschweißverbindungen

Failure assessment of laser weldments based on numerical modelling Classical fracture mechanics based assessments are no more sufficient to provide realistic predictions of the deformation and failure behaviour of welded structures. This situation can be improved by numerical modelling based on damage mechanics. A new concept will be provided, which is based on a cohesive model for crack growth simulation. The determination of the relevant material parameters is also considered where testing is combined with numerical simulation. For a laser weld joint, the gradient of the material properties has to be properly characterized. With miniature sized specimens, the material properties can be discretized by homogeneous layers. A new method, based on the digital image technique, has been introduced to determine the stress‐strain curves also in the large strain region due to necking. Test results on small bend bars containing a thin laser weld and a crack like defect in the centre show different crack path developments resulting from a competitive fracture situation. Mainly shear fracture mode occurs, in some cases also a pure normal fracture mode or a combination of both were observed. The concept presented is able to consider the crack development, if all occuring fracture modes are included in the analysis. However, a complete simulation of an extensive crack extension through a heterogeneous structure has not yet been verified.     

Werkstoffe für die direkte Nutzung der Sonnenstrahlung

Materials for Conversion of Solar Energy Materials for thermal, electrical and chemical conversion of solar energy are reviewed together with information on the physical basis common to all kinds of conversion. The natural and economical limits of the various techniques are mentioned.     

Verfügbarkeit von Metallrohstoffen für die Dünnschicht‐Photovoltaik

Availability of raw materials for the thin‐film photovoltaic on the example of gallium, indium and tellurium Gallium, tellurium, and indium are essential components used in the thinfilm technology which are predicted a growing demand. Their occurrence in the earth's crust is comparatively scarce thus they are produced and technically applied in small quantities. The trace metals are produced as a by‐product during extraction and refining of bulk metals such as aluminium, copper, or zinc. Essentially, the mining, processing and refining of the carrier element determines the maximum available production capacity. The global processing capacities of by‐products are limited, and the potentials of extraction are not fully utilized by current methods. Increasing the production of the by‐products would be achieved by increasing the production of the carrier elements or by extending the extraction capacities within an established production route. Moreover, the supply could be enhanced by processing currently untreated ores and concentrates as well as by treating residues from mining and processing.