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  • 1
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ionic Structures of 4- and 5-coordinated Silicon. Novel Ionic Crystal Structures of 4- and 5-coordinated Silicon: [Me3Si(NMI)]+ Cl-, [Me2HSi(NMI)2]+ Cl-, [Me2Si(NMI)3]2+ 2 Cl-. NMIMe3SiCl forms with N-Methylimidazole (NMI) a crystalline 1:1-compound which is stable at room temperature. The X-ray single crystal investigation proves the ionic structure [Me3Si(NMI)]+Cl- 1 which is the result of the cleavage of the Si—Cl bond and the addition of an NMI-ring. The reaction of Me2HSiCl with NMI (in the molar ratio of 1:2), under cleavage of the Si—Cl bond and co-ordination of two NMI rings, yields the compound [Me2HSi(NMI)2]+Cl- 2. The analogous reaction of Me2SiCl2 with NMI (molar ratio 2:1) leads to a compound which consists of Me2SiCl2 and NMI in the molar ratio of 1:2. During the sublimation single crystals of the compound [Me2Si(NMI)3]2+ 2 Cl-. NMI 3 are formed.
    Notes: Me3SiCl bildet mit N-Methylimidazol (NMI) eine bei Raumtemperatur beständige, kristalline 1:1 Verbindung. Nach der Röntgenstrukturanalyse entsteht unter Spaltung der Si—Cl-Bindung und Anlagerung eines NMI-Rings eine Verbindung ionischer Struktur [Me3Si(NMI)]+Cl- 1. Die Reaktion von Me2HSiCl mit NMI (Molverhältnis 1:2) führt unter Spaltung der Si—Cl-Bindung und Koordination von zwei NMI-Ringen zur Verbindung [Me2HSi(NMI)2]+Cl- 2. Bei der analogen Umsetzung von Me2SiCl2 mit NMI (Molverhältnis 2:1) entsteht eine Verbindung, die Me2SiCl2 und NMI im Molverhältnis 1:2 enthält. Bei der Sublimation werden Einkristalle der Verbindung [Me2Si(NMI)3]2+ 2 Cl-· NMI 3 erhalten.
    Additional Material: 3 Ill.
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  • 2
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: One of the basic prerequisites for rational and high quality production of plastic parts is a tool layout tailored to the production process. To date, both design and construction have generally been based on values acquired by experience. This first, necessitates highly qualified personnel and second, involves what is frequently time consuming and costly finishing work. Experience acquired so far with computer-aided layout of injection molds shows that even a designer with little experience reaches the target more quickly and more reliably. At the same time he is able to draw on the results of intricate calculation and simulation methods which he was unable to apply in the past for reasons of time alone. This paper thus sets out the possibilities currently open and the experience available for computer-aided mold layout. The chief point of focus here is a system for the layout of injection molds. Working on from this system, however, the potentials for computer application are presented for blow mold- and foaming mold-design. After finding the mold principle, mold layout essentially divides up into two major areas, namely dimensioning calculations (CAE) and compilation of production documents (CAD). In dimensioning, the different functional elements of the mold are calculated. The aids that have been developed and the potentials of computer-aided dimensioning are presented with examples from the fields of rheological, thermal, and mechanical mold layout. Computer-aided rheological layout divides up into two steps. The first gives information on qualitative filling behavior (filling picture, flow paths) and the second provides quantitative results (pressures, shear stresses, temperatures). Computer-aided thermal layout similarly divides up into part steps. These are a rough overall energy balance, a rough layout of the tempering system, a segmented layout, and a homogeneity check, which involves simulating the temperature conditions in the mold by means of difference methods. When it comes to mechanical layout of the mold, programs are available for deformation calculations on basic cases and these will frequently be sufficient. For more complex cases of loading and deformation, a finite element program is used. Graphic data processing units can be used to supply extra facilities - first, to provide an aid for the simulation programs in dimensioning and second, to rationalize the compilation of the production documents. An illustration of a CAD workplace is given, incorporating the necessary computer configuration and peripherals. Compiling production documents is essentially a problem of variant design. The variants in this case are the individual components of the mold and a number of standardized accessories that can be called up as “standardized components.” The mold cavity, however, always has to be a free design. All programs are dialogue driven and are in a standardized manner so that even designers with no data processing experience can use the computer as an aid. The CAD/CAE system presented duly fulfils all these requirements. It allows the designer, at a single computer work station, to carry out both simulation and dimensioning calculations, to obtain information on material data, and to compile production documents on the basis of variant and free design. This provides the designer with a readily manageable aid and makes a considerable contribution towards improving the design result. Finally, the capacity of different computer concepts and the CAE/CAD/CAM systems on the market are discussed. For the future it will be possible to establish a computer-aided link between the different areas of design, from development of the molded part, via mold design and production, through setting the processing parameters of the injection molding machine.
    Additional Material: 43 Ill.
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  • 3
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Investigations of the corrosion fatigue behaviour at a super pure martensitic stainless steel X5CrNiCuNb 17 4 PH in comparison to the soft martensitic stainless steel X4CrNiMo 16 5 1 ESR in chloride containing aqueous media  -  Part 2: Corrosion fatigue tests and crack initiation mechanismsThe following report concerns the study of the corrosion fatigue behaviour of the soft martensitic steel X4CrNiMo 16 5 1 ESR and the precipitation hardened X5CrNiCuNb 17 4 PH in sodium solution in the temperature range between 20° and 150 °C and the determination of their general corrosion properties and the mechanism of crack propagation. Their corrosion fatigue limits were compared with each other. A comparision was also made between an electro-slag-remelted soft martensitic steel and a charge without an ESR aftertreatment. Microfractographical fracture and crack path investigation were carried out for interpretation of the experimental results.It was observed that in both super pure steels (soft martensitic and precipitation hardened) the oxidic inclusions are not responsible for the crack intiation, as it was found in the non ESR treated steels. In the 17-4 PH steel copper containing inclusions in the crack initiation areas were observed. In concentrated sodium solution pitting corrosion was found at both steels.
    Notes: Untersuchungen zum Schwingungsrißkorrosionsverhalten des weichmartensitischen Stahles X4CrNiMo 16 5 1 ESU und des Martensitaushärters X5CrNiCuNb 17 4 PH in NaCl-haltigen Lösungen im Temperaturbereich zwischen 20° und 150 °C. Bestimmung der Korrosionseigenschaften und der Rißeinleitungsmechanismen. Vergleich zwischen einem Elektro-Schlacke-umgeschmolzenen Weichmartensiten und einer Charge, die nicht ESU-behandelt worden ist. Mikrofraktographische Bruch- und Rißverlaufsbeurteilung zur Deutung der Versuchsergebnisse.Die fraktographischen Untersuchungen ergaben, daß bei dem hochreinen weichmartensitischen und dem martensitaushärtenden Stahl oxidische Einschlüsse bei der Rißeinleitung keine Rolle spielen. Beim martensitaushärtenden Stahl wurden Cu-haltige Einschlüsse im Rißausgangsbereich nachgewiesen. In konzentrierter Salzlösung trat bei beiden Stählen Lochfraß auf, der rißinitiierend wirkte.
    Additional Material: 17 Ill.
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  • 4
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Pack aluminizing of low alloyed steel: Metallurgical aspects of the coating procedure and coating reliability in high temperature serviceThis study concentrates on metallurgical aspects of the pack aluminizing coating procedure of a low alloyed 1% Cr½% Mo steel (13 CrMo 44) as well as on the coating reliability in high temperature service.It is reported, how the coating procedure can be optimized by controlling coating temperature and time as well as the composition of the powder mixture.In high temperature service a protective coating has to withstand diffusion and corrosion reactions. Creep and low cycle fatigue of a component also can result in coating failure.Optimized coatings on low alloyed steels withstand high temperature sulfidation up to 600°C, where no increase in layer thickness or decrease of aluminium concentration in the specimen surface occurs. Even after creep strains of six percent no cracks are found in the coating.Thermal cycling of coated specimens results in nucleation and growth of cracks in the coating and thus represents the life limiting damage process of aluminized low alloyed steel.
    Notes: In einer Fallstudie am Beispielk des niedriglegierten Stahles 13 CrMo 44 wird in der vorliegenden Arbeit aufgezeigt, wie Schutzschichten auf Hochtemperaturwerkstoffen zunächst durch gezielte Einstellung der Beschichtungsparameter Pulvermischung, Beschichtungstemperatur und Beschichturgsdauer optimiert werden, wobei der metallographischen Analyse der Schutzschichten eine besondere Bedeutung zukommt (Abb. 11a).Die Schutzschicht muß im Hochtemperatureinsatz einem Beanspruchungskollektiv aus Diffusions- und Korrosionsreaktionen mit überlagerten mechanischen Beanspruchungen, wie Kriechen und thermische Ermüdung, standhalten (Abb. 11b). In der vorliegenden Untersuchung wurde das Beanspruchungskollektiv in seine Einzelkomponenten zerlegt. Es zeigte sich, daß Abdiffusion, Hochtemperatursulfidierung und Kriechen von einer optimierten Alitierschicht gut ertragen werden.Temperaturwechselbeanspruchungen führen zu Ermüdungsrißbildung in Pulveraluminierschutzschichten und stellen daher einen sehr wichtigen, die Lebensdauer bestimmenden Bestandteil des Beanspruchungskollektivs im Hochtemperatureinsatz dar.
    Additional Material: 11 Ill.
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  • 5
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Investigations of the corrosion fatigue behaviour at a super pure martensitic stainless steel (X 5 CrNiCuNb 17 4 PH) in comparison to the soft martensitic stainless steel X 4 CrNiMo 16 5 1 ESR in chloride containing aqueous media  -  Part 1: Corrosion investigations and stress corrosion tests to optimize the heat treatment according to the stress corrosion resistanceThe aim of this investigation was to improve the reliability of operation and the economy of corrosion fatigue stresses of structural elements, especially at elevated temperatures, by optimizing the material. This investigation is of great interest both to the industry and to related fields. It concerns the influence of a higher degree of purity achieved by the secondary metallurgical aftertreatment of soft martensitic steel X4CrNiMo 16 5 1 ESR (ESR-electroslag remelting) in comparison to the corrosion fatigue behaviour of the precipitation hardening steel X5CrNiCuNb 17 4 PH, which was specially heat-treated with respect to stress corrosion cracking resistance.The stress corrosion was investigated for all heat-treatments of the 17-4 PH in 22% NaCl(pH3) solution. The precipitation hardening steel was most resistant to stress corrosion in concentrated NaCl-solution after a three-stage heat-treatment.There was no improvement of corrosion fatigue resistance after metallurgical aftertreatment of soft martensitic steel compared to the untreated material. This is due to the instable passive behaviour of the material which led to crack initiation, especially during the 150°C experiments, at chloride-induced places of pitting.The investigation of the electrochemical corrosion behaviour of both materials showed that the pH-value hardly influences corrosion restistance. An increase of the salt content leads to higher pitting induction. At temperatures of 80°C in a saturated NaCl-solution the material showed no corrosion resistance. In potentiokinetic investigations, a direct transition from the active area to the pitting potential was observed. In accordance with both the corrosion fatigue and the stress corrosion cracking investigations, it was found that pitting at the martensite precipitator starts primarily around Cu-containing or oxidic inclusions.
    Notes: Durch eine Optimierung der Werkstoffe sollte die Betriebssicheheit und Wirtschaftlichkeit von SwRK-beanspruchten Bauteilen, insbesondere bei erhöhten Temperaturen, verbessert werden. Deshalb wurde der Einfluß eines erhöhten Reinheitsgrades durch sekundärmetallurgische Nachbehandlung am elektroschlacke-umgeschmolzenen, weichmartensitischen Stahl X4CrNiMo 16 5 1 ESU ermittelt, sowie das SwRK-Verhalten des martensitaushärtenden Stahles X5CrNiCuNb 17 4 PH mit einem im Hinblick auf die Spannungsrißkorrosionsbeständigkeit gezielten Wärmebehandlungszustand untersucht.Die SpRK-Untersuchungen wurden für alle Wärmebehandlungszustände des 17-4 PH in 22% NaCl/pH3-Lösung, und bei einer Temperatur von 80 bis 150°C durchgeführt. Der martensitaushärtende Stahl zeigte mit einer dreistufigen Wärmebehandlung die höchste Beständigkeit gegen SpRK.Die metallurgische Nachbehandlung des weichmartensitischen Stahles brachte keine Verbesserung der SpRK-Beständigkeit gegenüber dem nicht behandelten Werkstoff. Dies ist durch das instabilpassive Verhalten des Werkstoffes bedingt, das insbesondere bei den 150°C-Versuchen zur Rißeinleitung an chlorid-induzierten Lochfraßstellen führt.Die Untersuchung des elektrochemischen Korrosionsverhaltens beider Werkstoffe zeigte, daß der pH-Wert nur einen geringen Einfluß auf die Korrosionsbeständigkeit hat. Ein Erhöhen des Salzgehaltes führt zu einer gesteigerten Lochfraßinduzierung. Bei Temperaturen von 80°C in gesättigter NaCl-Lösung kann nicht mehr von einem Passivbereich gesprochen werden. In potentiodynamischen Untersuchungen war ein direkter Übergang vom Aktivbereich zum Lochfraßpotential zu beobachten. Auch hier konnte in Einklang mit den SwRK- (Teil II) und SpRK-Untersuchungen festgestellt werden, daß ein frühzeitiger Ausfall des 17-4 PH eintritt, wenn Cu-haltige bzw. Oxidische Einschlüsse an der Oberfläche vorhanden sind.
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  • 6
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: An Folien (Dicke 100 pm) aus isotaktischem Polypropylen mit verschiedenen Antioxidansgehalten (0,0% bis 0,1%) wird die thermooxidative Alterunq mit der isothermen Langzeit-Differential-Thermo-Analyse (ILDTA) bis zu Temperaturen weit unter dem Kristallitschmelzbereich verfolqt und die Messwerte mit Ergebnissen aus dem Zeitstand-Zugversuch korreliert. Dabei zeigt sich, daß aus Messunqen mit der ILDTA bereits vor Einsetzen der autokatalytischen Zersetzunq sreaktion Ruckschlüsse auf die thermische Vorqeschichte der Proben und Aussagen auf das rnit einem Abfall der mechanischen Eigenschaften verbundene Ende der thermo-oxidativen Stabilität des Polymeren getroffen werden können.Weiters bietet die ILDTA die Moglichkeit, durch den direkten Zusamenhang zwischen Oxidationszeit und Antioxidansögehalt die örtliche Stabilisatorverteilung in Platten und in Folien zu bestimmen und damit Diffusionsvorqange zu verfolgen.
    Notes: Thermo-oxidative ageing processes were investigated in films (100 μm thick) made from isotactic polypropylene with different antioxidant concentrations between 0% and 0.1% using isothermal long-term differential thermal analysis (ILDTA). The end of the oven life of polypropylene coincided with the loss of mechanical properties which was confirmed by tensile tests at temperatures far below the crystallite melting range. Already prior to the beginning of autocatalytic decomposition, ILDTA experiments permits conclusions to be drawn on the thermal history of the specimens and statements made regarding the end of thermo-oxidative stability of the polymer, which is accompanied by a deterioration in the mechanical properties.In consequence of the correlation between oxidation time and antioxidant concentration the local antioxidant concentration in sheets or films can be measured by ILDTA. Thus, investigating the diffusion of an antioxidant in polypropylene using ILDTA is possible.
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1988 (1988), S. 603-604 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Chiral Auxiliary Groups: Formation of a Phenylaza Analogue of Camphanic Acid after Change of N/O-Regioselectivity of a Ring-Contraction ReactionBy treating α-bromo imide (-)-1 with sodium methylate an earlier observed mode of ring contraction is altered from O- to N-alkylation and the bicyclic lactam (+)-3b is formed.
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  • 8
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: At the coagulation of polymer blend solutions highly porous structures are formed. This paper presents a mathematical formalism for the prediction of the expected pore volume and results on the influence of concentration, kind and quantity of the added polymer. The experimental results are in good agreement with calculated values and thus confirm our concept of the mechanism of pore formation by coagulation of mixtures of polymer solutions.
    Notes: Bei der Koagulation von Polymermischungslösungen entstehen hochporöse Fällungsstrukturen. In dieser Arbeit werden neben dem mathematischen Formalismus zur Vorhersage des zu erwartenden Porenvolumens Ergebnisse zum Einfluß der Konzentration, Art und Menge an Zusatzpolymer mitgeteilt. Der Vergleich von berechneten und gemessenen Porenvolumina zeigt gute Übereinstimmung und bestätigt damit die Vorstellungen zum Porenbildungsmechanismus bei der Koagulation von Polymermischungslösungen.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Using the so-called bicomponent principle, which consists in the preparation of a compound film of two polymer solutions followed by separation of this bicomponent compound in two bicomponent membranes, polymer membranes with new structures having a high degree of asymmetry could be made. A variant of this principle is suggested where the bicomponent slit die dips into the liquid coagulation medium. The effect of the coagulation conditions, especially of the composition of the coagulation medium, on the structure and the separation properties of the resulting membranes is discussed with the examples of poly(acrylonitrile), cellulose-2.5-acetate, and polyurethane.
    Notes: Mit Hilfe des Bikomponentenprinzips, bei dem ein Verbundfilm aus wei Polymerlösungen hergestellt and dieser komponentenverbund in zwei sogenannte Bikomponentenmembranen aufgetrennt wird, lassen sich neuartige Polymer-membranstrukturen mit hohem Asymmetriegrad herstellen. Es wird cine Variante vorgestellt, bei der eine Bikomponentenbreitschlitzdüse in ein flüssiges Koagulationsmittel eintaucht. Die Einflüsse der Koagulationsbedingungen, insbesondere der Koagulationsmittelzusammensetzung, auf die Struktur und die Trenneigenschaften der resultierenden Produkte werden am Beispiel Polyacrylnitril, Cellulose-2,5-acetat und Polyurethan dargestellt und diskutiert.
    Additional Material: 11 Ill.
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  • 10
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Light induced aging of the investigated photoconductors is studied by UV-VIS and EPR spectrometry. The reasons for the deterioration of the electrophotographic properties are discussed. It is supposed, that the holes generated by exposure are radical cations, which are able of R-abstraction and recombination with other free radicals.
    Notes: Die lichtinduzierten Alt erungsreaktionen der genannten Photoleiter werden durch UV-VIS- und EPR-Spektrometrie untersucht und die Ursachen für die Verschlechterung der elektrophotographischen Eigenschaften diskutiert. Es wird angenommen, daß die photogenerierten Defektelektronen sich chemisch wie Radikalkationen verhalten und zur R-Abstraktion sowie zur Rekombination mit anderen freien Radikalen befähigt sind.
    Additional Material: 6 Ill.
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