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  • Polymer and Materials Science  (11)
  • Computational Chemistry and Molecular Modeling  (3)
  • Chemical modification  (2)
  • 11
    Electronic Resource
    Electronic Resource
    Beitrag zur Methodik der Messung von Lochfraßpotentialen an austenitischen Chrom-Nickel-Stählen (1971)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 22 (1971), S. 686-690 
    Details
    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: Contribution to the methodology of pitting corrosion potential measurement on austenitic chromium nickel steelsReproducible values of the pitting potential and the incubation period are obtained only when definite techniques are applied to the specimen preparation. When the specimens are to be masked for the purpose of suspension they must be passivated without this mask because otherwise there would occur some type of crevice corrosion in the boundary zone between mask and open specimen surface. The corrosion potential in this is more negative (by 150 mV for a steel AISI 316) the the pitting potential as such. Preferential dissolution occurs in this zone when the pitting potential is attained. When, on the other hand, the passivation is effected without the mask, uniform pitting is achieved across the whole free surface and the pitting potential may be measured without difficulty. This potential turns out to be independent from the duration of passivation, while the incubation period distinctly increases with passivation time.
    Notes: Reproduzierbare Werte des Lochfraßpotentials und der Inkubationszeit erhält man nur, wenn bei der Vorbehandlung der Proben bestimmte Techniken eingehalten werden. Wenn die Proben zur Aufhängung teilweise abgedeckt werden sollen, müssen sie ohne die Abdeckung passiviert werden , da es sonst in der Grenzzone zwischen Abdeckung und Probenoberfläche zu einer Art Spaltkorrosion kommen kann. Das Korrosionspotential liegt dort z.B. für einen Stahl AISI 316 um 150 mV negativer als das eigentliche Lochfraßpotential. In diesem Bereich tritt dann auch bei Erreichen des Lofraßpotentials bevorzugte Auflösung ein. Passiviert man hingegen ohne Maske, so erreicht man gleichmäßigen Lochfraß über die ganze unbedeckte Oberfläche und kann auch das Lochfraßpotential einwandfrei bestimmen. Dieses erweist sich als unabhängig von der Passivierungsdauer, während die Inkubationszeit deutlich mit der Passivierungsdauer zunimmt.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19710220804
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  • 12
    Electronic Resource
    Electronic Resource
    Die Inhibition von KühlkreisläufenVorgetragen am 214. DECHEMA-Kolloquium am 28. November 1974. (1975)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 26 (1975), S. 192-199 
    Details
    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: The inhibition of cooling systemsThe choice of an efficient corrosion inhibitor has to take in account the type of the cooling system, the materials used as well as the specific operating conditions, for instance - very low or very high velocities of the cooling water- heat transfer- the inhibitor may be asked to have some lubricating properties- vibrations, that can cause cavitation or fatigue corrosion- interaction between the corrosion inhibitor and other electrochemical systems of corrosion protection (cathodic protection).In numerous applications it is necessary to improve the inhibition by an addition of other effective substances (like dispersants, hardness stabilizers, mixture of inhibitors with selective protection properties).
    Notes: Die Auswahl eines Kühlwasserinhibitors richtet sich nach der Art des Kühlsystems und der darin verwendeten Werkstoffe sowie nach den spezifischen Beanspruchungen, so z. B.- extrem hohe oder niedrige Strömungsgeschwindigkeiten des Kühlmediums,- hohe Wärmebelastung der zu Kühlenden Metallwand,- Reibungsvorgänge, wobei der Inhibitor zusätzlich eine Schmierfunktion ausüben muß,- Vibrationen, die zu Kavitationserscheinungen oder zur Werkstoffermüdung führen Können,- Wechselwirkungen des Inhibitors mit anderen elektrochemischen Schutzverfahren (z. B. lokaler kathodischer Schutz von hochbeanspruchten Zonen des Kühlsystems).In zahlreichen Fällen ist es zudem notwendig, die Wirksamkeit der Inhibierung durch den Zusatz von weiteren Wirkstoffen zu unterstützen (Dispergiermittel, Härtestabilisatoren, Gemische von Inhibitoren mit selektiver Schutzwirkung).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19750260304
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  • 13
    Electronic Resource
    Electronic Resource
    Prüfung und Auswahl von KavitationsinhibitorenVortrag, gehalten an der Università di Ferrara anläßlich des 4. Europäischen Symposiums über Korrosionsinhibitoren, September 1975. (1976)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 27 (1976), S. 425-431 
    Details
    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: Testing and Selecting Cavitation InhibitorsAn investigation has been made into possibility of using electrochemical procedures as well as the gravimetrical method for testing cavitation inhibitors. The relation between the structure of the inhibitor, the nature and form of the cavitation attack and the mechanism of destruction was also examined. This work was performed with a group of conventional cooling water inhibitors and some pyridine compounds.It was shown that electrochemical investigations are less suitable for enabling inhibitors to be selected for high cavitation intensities, because electrochemical losses amount to only a relatively small part of the total loss of material. Nevertheless they are indispensable as a supplement to magnetostrictive investigations for appraising the overall performance of an inhibitor, because it has been found that a good cavitation inhibitor does not always achieve the same success against electrochemical corrosion.Furthermore it was demonstrated that interface inhibitors generally yield better results than membrane inhibitors or passivators. The protection afforded by interface inhibitors depends on their structure, the chain length and in the case of the pyridine components investigated the nature and position of the substituents in the pyridine ring.
    Notes: Es wurde untersucht, ob für die Erprobung von Kavitationsinhibitoren neben der gravimetrischen Methode auch elektrochemische Prüfverfahren eingesetzt werden können. Es wurde ferner der Zusammenhang zwischen Struktur des Inhibitors, Art und Form des Kavitationsangriffes und Mechanismus der Zerstörung untersucht. Diese Arbeit wurde mit einer Gruppe herkömmlicher Kühlwasserinhibitoren sowie mit einigen Pyridinverbindungen durchgeführt.Wie es sich zeigte, sind elektrochemische Untersuchungen weniger geeignet, eine Inhibitorauswahl bei hohen Kavitationsintensitäten zu ermöglichen, da die elektrochemische Metallauflösung nur einen relativ kleinen Teil des gesamten Abtrags ausmacht. Sie sind aber als Ergänzung zu magnetostriktiven Untersuchungen für die Beurteilung des Gesamtverhaltens eines Inhibitors unbedingt notwendig, da es sich gezeigt hat, daß nicht immer ein guter Kavitationsinhibitor mit demselben Erfolg gegen elektrochemische Korrosion eingesetzt werden kann.Wie sich außerdem herausstellte, liefern Grenzflächeninhibitoren in der Norm bessere Resultate als Membraneninhibitoren oder Passivinhibitoren. Bei den Grenzflächeninhibitoren ist die Schutzwirkung von der Struktur des Inhibitors abhängig, wobei insbesondere Kettenlänge und - bei den untersuchten Pyridinverbindungen - Art und Stellung der Substituenten eine wichtige Rolle spielen.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19760270606
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  • 14
    Electronic Resource
    Electronic Resource
    Theoretical investigation of the enantioselective hydrogenation of α-ketoesters over pt/alumina modified with cinchonidine (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 191-197 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantioselective hydrogenation of α-ketoesters with cinchona-modified platinum catalysts has been studied theoretically in order to rationalize the interaction between the chiral modifier and the substrate. The structure of the probable transition complex has been calculated for the system methyl pyruvate (substrate)-cinchonidine (modifier) using quantum chemistry techniques at both ab initio and semiempirical levels and molecular mechanics. The calculations indicate that crucial interaction occurs via hydrogen bonding of the quinuclidine nitrogen and the oxygen of the α-carbonyl moiety of methyl pyruvate and confirm earlier experimental evidence that the quinuclidine nitrogen of the cinchonidine is involved in the interaction leading to enantiodifferentiation. The resulting complex, which resembles to a half-hydrogenated state of the substrate, is shown to be a possible transition state for the enantioselective hydrogenation of α-ketoesters. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520119
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  • 15
    Electronic Resource
    Electronic Resource
    Comparison of the performance of various gradient-corrected exchange and correlation functionals in density functional theory: Case studies of CO and N2O molecules (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 753-762 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An investigation of the influence of various gradient-corrected exchange and correlation functionals on the bond lengths and dipole moments of CO and N2O has been carried out using density functional theory. It is shown that whereas some functionals are found to be more sensitive to the basis set quality than are others, the more commonly used gradient-corrected functionals lead to properties in very good agreement with experiment provided that a sufficiently large basis set is employed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560560611
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  • 16
    Electronic Resource
    Electronic Resource
    A multichannel electro-optical detector for rapid acquisition of X-ray photoelectron spectroscopy data (1979)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 1 (1979), S. 45-46 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An electro-optical detector easily adaptable to any hemispherical sector photoelectron spectrometer is described. The detector consists of a channel plate electron multiplier array, phosphor screen, silicon intensified target vidicon an optical multichannel analyzer control unit. Data collection rates are improved by more than two orders of magnitude over conventional single channel detectors.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740010109
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