Herstellung und Untersuchung aufgedampfter Funktionsschichten zum Einsatz in modularen Mikrosensoren

Fabrication and characterization of functional layers evaporated for the application in modular micro sensors A new concept aims at the development of genetically intelligent (“gentelligent^TM”)devices, which bequeath production or application data to their next generation. To support such an approach, it is necessary to gather various data from the device. To do so, afamily of modular sensors is under development, which is capable of measuring strain, force, magnetic properties, and temperature. Such micro sensor sconsist of structural and functional patterned thin films. A technology particularly well suited for such thin films is the vacuum deposition. This process allows to deposit rather different materials for conductors, insulators, and alloys for creating functional films. This work describes the technology development for fabricating temperature sensitive metallic functional films of Cu and Pt by means of electron beam evaporation and of an insulating SiO₂ film by means of thermal evaporation. The latter film is deposited by evaporating SiO and its thermal oxidation to SiO₂.     

Detonationsflammspritzen hartstoffhaltiger Funktionsschichten

Detonation flamespraying of functional surfaces Thermal spraying is well known for its possibilities to improve the surface of tools. Depending on the purpose advanced properties can be achieved by the coating. Electrical and thermal isolation, wear resistance and corrosion protection are typical applications. The assignment to develop composite coatings for grinding stone and concrete is a new field of investigation. Compared to complex and restrictive sintering and brazing processes the production of grinding tools based on thermal spraying can be an alternative option. With high geometric variability and lower process costs it has a high economic potential. In order to create high performance tools in future, fundamentals of process optimisation are evaluated in this research work. Based on the detonation flamespraying process for embedding large superabrasive particles into a copper‐based matrix has been studied. Bonding quality, coating morphology and hard particle allocation have been examined regarding to the profile requested. In addition the influence of process and substrate temperatures on the properties of the MMC‐compound have been analysed.     

Elektronenbeugung zur Analyse dünner Funktionsschichten

Electron Diffraction for Analysis of thin Functional Layers A short history of the diffraction techniques in crystallography is given and the basics of electron diffraction in transmission electron microscopy are explained: electrons as waves, Bragg's law, selected area and convergent beam electron diffraction. The possibilities of the often used selected area electron diffraction are demonstrated by two typical examples: determination of the crystallographic orientation in single crystalline layers (piezoelectric LiTaO₃) and phase analysis in polycrystalline structures (Ni‐Al‐O hard coatings).     

Organische LEDs

Certain polymers are able to generate luminescence when being applied to an electric field. Basically, this effect allows to manufacture luminous flat displays on a low cost basis. However, most processes involved are still in a development stage. High vacuum evaporation is applied for the conductive layers and is also used to deposit the low molecular organic material. Co‐evaporation, fine tuning of evaporation sources and prevention of cross‐contamination are basic demands on process equipment. Materials involved are sensitive to Oxygen and water vapour. Therefore they need to be handled by load lock transfer systems or under inert gas. Integrating vacuum deposition systems into inert gas glove boxes is a state‐of‐the‐art solution.     

Organische UV‐Schutzschichten für die Polycarbonatverglasung

Organic UV‐protective coatings for polycarbonate glazing Polycarbonate as glazing material in outdoor applications requires functional UV protective and scratch resistant coatings. The vacuum coating technology offers a wide range of deposition processes to produce such complex coatings. The Fraunhofer IOF developed an effective UV protection by the deposition of organic UV absorbers. Thermal evaporated organic compounds were investigated as single layers and hybrid layers in a SiO₂ matrix. The UV‐stability of such coatings was increased significantly.     

Organische Polymere als funktionelle Werkstoffe für chemische Sensoren

Organic polymers as functional materials for chemical sensors The function of many chemical sensors for measurements in liquids and in gases with ambient temperature is based on the combination of a transducer with organic membranes. These membrans determine essential sensor properties as selectivity, sensitivity and response characteristics. In addition they protect the detection system against external influences. Therefore the selection and synthesis of polymer membranes are an essential constituent of the sensor investigation and sensor development. Electrical, optical and biological properties of the polymers are important in this case. A survey of the materials used in the remote sensing is given. Of special interest to the sensor investigation are in last time intrinsic conducting polymers (ILP) whose properties opened new possibilities of the sensor development. With the help of an electrochemical pH glass electrode with inner solid contact it is shown that polypyrrole can be used as a material for a long‐lived inner solid contact and as substitute for inner secondary reference electrode. Practice tests confirm the suitability of this polymer material. Aspects of the transport mechanism of electrical charges through the boundary surface conducting polymer | glass are discussed.     

Organische Bindemittel zum Wärmearmen Fügen

Organic adhesives for low heat joining techniques. The applications of adhesives have been greatly extended by the using of synthetic organic polymers which cures physically or chemically. They give satisfactory adhesion to different materials, flexibility, and mechanical properties even at high temperatures. A particulary important advance was the introduction of chemically or mechanically blocked polymer systems, which reduces curing time and costs of curing equipment.     

Holz und Holzwerkstoffe in der Technik von heute und morgen

Wood and Woodmaterials in the Technology of Today and Tomorrow. Though wood on the market is under the pressure of numerous competing materials, its production and consumption increases on the whole world. Available are round logs, sawn lumber, sheetlike wood based materials such as plywood, particleboard, fiber building board and since some time glued structural parts. Continuous wood consumption is necessary for securing the beneficial effects of forests. In the Federal Republic of Germany and in most industrialized countries the production of particleboard increased in a parabolic manner. A special stimulation of wood consumption came by glued laminated structural parts. Firms working on this field founded the organization Glulam with the aim to standardize the production methods, the permissible stresses, the classification and dimensions of the sawn wood, the calculation of glued wood constructions and its behaviour in fire. On the basis of test results the minimum dimensions for fire resistance grades F 30 and F 60 (30 min. and 60 min.) are given. Large spans e. g. for halls, serving for various purposes, gymnasiums, covered tennis courts, ice rink halls, swimming baths, churches, warehouses, factory buildings, storage sheds, filling stations, shell roofs and bridges can be built with no other materials besides laminated timber with so little dead weight.     

Spannungs-Dehnungsverhalten und Lebensdauer ungekerbter und gekerbter Proben und Bauteile

Stress-Strain and Fatigue Life Behaviour of Unnotched and Notched Specimens and Components In contrast to unnotched specimens where the cross section and the surface area are uniformly deformed, when external loads are applied at the specimens, notched specimens and components show severe concentrations of stress and deformations at the notches. In the paper different type of notches are considered and the effect of the notches under different loading conditions (monotonic, cyclic loading) is described. Some possibilities for predicting the crack initiation of notched components are also outlined and the effect of corrosive environments is briefly discussed.     

Gefriertrocknung in Labor- und Industrieanwendungen

For preservation and extension of shelf life time for food, pharmaceutical and biotechnical products, Freeze Drying has been proven to be the most effective and economical technology. The freeze dried products remain unchanged in structure, keep their colour, aroma, nutrition and their biological consistence, In the following the author would like to present an overview of the definition, technology with its restrictions and the process with the use of vacuum.     

Oberflächenschutzverfahren und ihr Einsatz in der Werkstoff- und Tribo-Technik

Hardfacing-Methods and their Application in the Materials-Technology and Tribology During the last few years more and more efforts have been made to reduce or even avoid material losses, caused either by mechanical or corrosive attack, by the means of protecting metal surface protection. In fact, the expenses needed in the Plastic-Technology for the disposition of wear-spares in West Germany amount to half a billion DM a year [1]. If all the damages by wear and corrosion are included, the losses world-wide rise to more than 80 billion DM/year. Thus not only technical but most of all economical reasons promote the rapid development of different hardfacing methods. The various methods are presented with ascending temperature of the working materials (s. Fig. 1).     

Langsames Ermüdungsrisswachstum in Aluminium‐ und Magnesiumgusslegierungen in Raumluft und in Vakuum

Slow fatigue crack growth in aluminium and magnesium cast alloys in ambient air and in a vacuum The influence of ambient air on near threshold fatigue crack growth in the magnesium cast alloys AZ91 hp, AM60 hp and AS21 hp and in the aluminium cast alloy AlSi9Cu3 has been investigated. Fatigue crack growth properties at a cycling frequency of 20 kHz in ambient air and in a vacuum are significantly different. In a vacuum, the threshold stress intensity amplitude of the aluminium alloy is 30% higher than in ambient air, and the threshold values of the magnesium alloys in a vacuum are up to 85% higher than in ambient air. Moisture of ambient air is responsible for accelerated crack growth at growth rates below 1–3 × 10⁻⁹ m/cycle (AlSi9Cu3) and 2–5 × 10⁻⁸ m/cycle (magnesium alloys), respectively. In ambient air a minimum crack growth rate of 5 × 10⁻¹¹ − 2 × 10⁻¹⁰ m/cycle was observed, whereas far lower minimum growth rates were found in a vacuum.