Charakterisierung von Glas und Glasbeschichtung mittels oberflächensensibler Sondenverfahren

The presented results of investigations by surface and microanalytical methods confirm the suitability of electron beam and scanning probe techniques for process monitoring, support of process development and defect analyses in the glass industry. More and more glass and coating specialists use the high tech service provided by an external laboratory with its wide range of experience and knowledge.     

Charakterisierung von Aluminiumoxidschichten

Characterization of Aluminium Oxide Layers Adhesive bonding aluminium sheets is a manufacturing process which is very relevant in aircraft construction. In order to produce bonds featuring adequate strength and long-term stability, an aluminium oxide layer having certain properties must be generated on the sheet surface during pretreatment. The properties of aluminium oxide layers which are required and adequate in the light of current findings are delineated in this paper and the analytics prepared for the purpose of checking these properties are presented. Al₂O₃ layers produced by means of pickling and chromic acid and phosphoric acid anodic oxidation can be characterized adequately by means of the following:

• chemical composition (impurity)
• layer thickness
• structure
• morphology

The following methods of physical analysis are employed in order to determine these properties:

• Surface analysis (AES, ESCA, SIMS) in conjunction with ion etching for the obtention of depth profiles.
• Electron diffraction in reflection and transmission as well as X-ray diffraction.
• High-resolution scanning electron microscopy (resolution 30 Å).
• Transmission electron microscopy.

Further more, the methods of investigation which in our opinion are necessary and adequate for checking in the practice the proper pretreatment of aluminium sheets for subsequent bonding are also presented.     

Charakterisierung der Oberflächenmodifikation von Edelstahlproben nach Elektronen- und Ionenbombardement mittels REM,AES und XPS

The interaction of an inert or reactive gas plasma with the surface of stainless steel was investigated with the aim, to modificate the surface and to influence by this the outgassing rate of the material. This question is especially interesting in applications of these materials in large UHV devices, where a heat treatment of surfaces at the vacuum side is not favourable because of the high energy costs. The investigated samples were exposed to the influence of electrons, argon and oxygen ions either in a DC glow discharge or in a microwave discharge. After this pretreatment the surfaces of the samples were investigated with respect to the topography and the chemical composition (depth profile) by Secondary Electron Microscopy (SEM), Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS). These surface modifications as a result of the different treatments of the samples were correlated with the measurements of the outgassing rate.     

Charakterisierung von Schichten und Platten

Characterization of layers and sheets – nondestructive and contactless testing with the help of microwaves With the help of microwaves a variety of materials in the form of layers, plates, or objects of complex geometry can be characterized in terms of their material properties, geometry and defects. The test is non‐destructive and can be performed quickly and without contact. In transmission mode non‐metallic and electrically slightly conductive materials can be investigated with a thickness of up to several cm while in metallic materials the testable thickness is in the micronand nanometer‐range. In reflection mode materials with higher electric conductivity can be tested, too.     

Eine Charakterisierung der Unterhalbstetigkeit von Restriktionsmengen

Zusammenfassung Die vorliegende Arbeit will charakterisieren, wann sich Restriktionsmengen bei konvexen bzw. quasikonvexen Optimierungsproblemen in Abhängigkeit von den Restriktionsfunktionen unterhalbstetig ändern. Zu diesem Zweck wird die Unterhalbstetigkeit des mengentheoretischen Durchschnitts für konvexe Mengen untersucht, und sie erweist sich als gleichwertig mit der Nicht-Trennbarkeit der gegebenen konvexen Mengen. Dieses abstrakte Ergebnis liefert sofort die Lösung für die Unterhalbstetigkeit der Restriktionsmengen.

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Summary This paper tries to characterize lower semicontinuous dependence of constraint sets on the constraint functions in convex and quasiconvex optimization. For this purpose the lower semicontinuity of the set theoretic intersection for convex sets is investigated, and we will see, that it is equivalent with the Non-Separability of the given convex sets. This abstract result contains obviously the solution for the lower semicontinuity of the constraint sets.

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Diese Arbeit stellt eine Weiterentwicklung einiger Ergebnisse in [5] dar. Für die Anregung und hilfreiche Unterstützung möchte der Autor Herrn Prof. Dr. G. Heindl danken.     

Charakterisierung der Verbundschichten von magnetoelastischen Sensoren

Characterisation of composite layers in magnetoelastic sensors Carbon fibre surfaces, coated with magnetoelastic materials and structured by methods of micro‐manufacturing can serve as strain and tension sensitive sensor systems capable to support safety and health monitoring functions in parts made of composite materials. In cooperation with the Institute for Microtechnology Hannover the fabrication method based on thin‐film deposition technology and micro‐structuring by means of Focused Ion Beam machining was developed. Carbon fibres with multiple layers deposited by Physical or Chemical Vapor Deposition techniques show novel properties. The characterisation of this spectrum of mechanical, electrical and physical properties is topic of this research. The first results of all examinations will be presented.     

Untersuchung von IBBD-Aluminium-Schichten mittels elektrochemischer Rauschanalyse

Examination of IBDA-aluminum-layers by electrochemical noise analysis The quality of extremely thin surface coatings for wear and corrosion protection is significantly influenced by pores and film defects (voids, micro cracks, coated impurities), which can occure in the processing stage. These sites are substantially responsible for a mechanical or chemical degradation of the coating at contact with respective surrounding conditions. To meet the requirements of protection the processing stage is optimized by minimizing pores and flaws. Therefore a suitable testing method is necessary to detect the dissolution of the substrate at voids in the earliest stage and to examine large series with acceptable time expenditure for a statistical accuracy. Investigations for the optimization of coating parameters were carried out by means of Electrochemical noise analysis (ENA) on IBAD-aluminum-layers (ion beam assisted deposition) at mild steel(Ck45).     

Die Bewertung von Kreditgarantien mittels Hyperoptionen

Zusammenfassung. Aus finanzwirtschaftlicher Sicht k?nnen Kreditgarantien als Verkaufsoptionen auf das anteilige Gesamtverm?gen einer Unternehmung interpretiert werden. Die Bewertung von Kreditgarantien erfolgt üblicherweise mit dem Ansatz von Merton. Bei diesem Modell wird jedoch unterstellt, da? sowohl für den garantierten Kredit als auch für das nicht garantierte Fremdkapital vor Ablauf der Laufzeit keinerlei Zins– und Tilgungszahlungen geleistet werden. Unsere Arbeit pr?sentiert ein Modell zur Bewertung von Garantien auf Kredite mit beliebigen Zins– und Tilgungsmodalit?ten. Das vorgeschlagene Bewertungsmodell wird auf Kredite mit unterschiedlichen Tilgungsformen angewendet. Darüber hinaus werden Sensitivit?tsanalysen bezüglich der Einflu?faktoren auf die aus dem Modell resultierenden Pr?miens?tze durchgeführt. Eingegangen: 2. Februar 1999 / Angenommen: 9. Dezember 1999     

Charakterisierung von ferrocen-FeOCl-intercalat-phasen durch tieftemperatur-Mössbauerspektroskopie

Fe (C₅H₅)₂⁺ (6FeOC1) · e^? intercalation phases were studied by Mössbauer spectroscopy at 4 K. The absorption lines of the guest and host iron components are clearly separated. The isomer shift of the Fe (C₅H₅)⁺₂ guest species relative to α-Fe metal lies between δ = 0.44 ? 0.48 mm/sec. When prepared at room temperature, the intercalated compound represents, at 4 K, a single phase with a paramagnetic and an antiferromagnetic component, as expected for Fe (C₅H₅)₂⁺ (6FeOC1) · e^?. In preparations at higher temperature however, two magnetically ordered systems are revealed at 4 K, both of which differ in their magnetic and quadrupol data from the previously mentioned phase.     

Charakterisierung plasma‐ modifizierter Polymere mittels SSXPS und XPS‐Imaging

For many years now, engineering polymers with tailor‐made surface properties are of widespread interest. One of the most commonly used technique to functionalize or coat polymers is the plasma technique. One of the most important reasons is the possibility to tailor the surface properties without alteration of the versatile bulk properties. Many engineering polymers applied in medical equipment, life‐science, and biotechnological purposes demand monofunctionalized and structured surfaces. Those can be obtained with appropriate process parameters. The characterization of such tailored surfaces as well as of surfaces with structured functionality can be performed by several analytical tech niques. Besides AFM and FTIR the photoelectron spectroscopy (XPS, ESCA) is used.     

Komplexe Bewertung von Indentereindrücken zur Charakterisierung von Konstruktionskeramik

The induction of indentations in brittle materials and their evaluation result in information useful for the characterization of materials. In addition to the fracture-mechanical evaluation of the indentations, i.e. of the incipient cracks resulting from them, which cracks are used for determining the fracture toughness. Information regarding the hardness, critical size of surface defects, characteristic quantities of crack propagation, durability as well as existing internal stresses can be derived.     

Gezielte Entwicklung von Magnesiumlegierungen mittels angewandter Thermochemie

No abstract The principle and the methodology of focused alloy development by means of applied thermochemistry are described. The Calphad method is described briefly. As an example, calculations used for applications are shown in the system Mg‐Al‐Sc. In more detail the development of creep resistant alloys in the system Mg‐Mn‐(Sc, Gd, Y, Zr) is discussed. One aim is to produce a sufficiently large quantity of efficient precipitations in the structure in order to improve the mechanical properties with a minimum of expensive alloying addition. The large number of possible combinations of the alloying elements in the system Mg‐Mn‐(Sc, for Gd, Y, Zr) on the one hand and the time and cost of technological experiments on creep stability on the other hand require a preselection of the systems and the alloy compositions. Thermodynamic phase equilibrium and phase amount diagrams were calculated, which give indications on the selection of the promising alloying elements. A priority list of three quaternary systems is produced: Mg‐Mn‐Gd‐Sc, Mg‐Mn‐Sc‐Y and Mg‐Mn‐Y‐Zr. For technical investigations the alloy MgMn1Gd5Sc0.8 (wt.%) is most promising, furthermore the alloys MgMn 1Gd5Sc0.3 and MgMn1Y5Sc0.8 seem promising. Very many other alloys could be eliminated as doubtfull or useless with this method. The entire quaternary Mg‐Mn‐Y‐Zr system was disqualified because of characteristics of the phase diagram, which are harmful for the desired microstructure. This focused alloy development saves time and cost‐intensive technical investigations.     

Bestimmung von Ausgas- und Desorptionsraten mittels Restgasanalysator

Determination of Outgassing and Desorption Rates by Means of Residual Gas Analysis Especially when using plastic materials in vacuum chambers it is essential to know the amount of gases outgassing from the surface of those materials. Depending on the so-called outgassing or desorption rate one can decide if the proposed plastic material is suited for the desired application and how the vacuum system has to be configured, so that the use of the particular material makes sense. The article will demonstrate by means of 2 examples that there exist temperature-dependent outgassing behaviors of different materials. It also gives an overview of the measuring equipment set up to determine the outgassing rates.     

Barriereausrüstung von Kunststoffen mittels PECVD

Effect Mechanisms in PECVD Barrier Coating of Plastics Especially optical transparency as well as very high barrier functionality, preventing the transmission of gas and aroma, qualifies silicon‐oxide as material of choice for thin PECVD‐coatings on plastics. Whereas permeation through plastics can be described by the Arrhenius‐model, there is no universal model for transport mechanisms through single or multilayer PECVD‐coatings. Models that do exist describe diffusion through defects. These models presume that no permeation besides transmission through these defects occurs. Topic of this research is to determine which model fits the experimental data of oxygen‐ and water vapour‐transmission of experimental data. In order to investigate the applicability of different models, single‐ and both‐sided are compared using different layer architectures.     

Bruchmechanische Charakterisierung des Ermüdungsverhaltens von SiSiC

Fracture Mechanics Characterization of Fatigue in SiSiC The behaviour of microscopic “natural” cracks and of artificial sharp cracks was investigated on a fracture mechanics base for extruded and slip casted SiSiC. The resulting strength and crack propagation data were used to calculate relations between loading time and probability of fracture and thus provide a base for the practical application of the investigated materials in structures. Examples of calculated life times and probabilities of failure as well as results of experiments performed to check the calculations are discussed.