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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 49 (1961), S. 238-240 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 3 Tab.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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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: The radiotracer technique as a means to investigate the corrosion of zirconium, tantalum, and a Ta-40Nb alloy in fluoride containing azeotropic nitric acidZirconium and tantalum as well as the tantalum 40% niobium alloy are of considerable technical importance due to their high corrosion resistance against numerous corrosive media. With respect to corrosion testing in analytically pure azeotropic nitric acid in the temperature range between 20 and 121°C, corrosion rates were determined for zirconium: 7 · 10-6 to 5 · 10-4 mm/y, for tantalum: 10-8 to 4 · 10-6 mm/y, and for the Ta-40Nb alloy: 2 · 10-7 to 8 · 10-6 mm/y [1]. These corrosion rates will be markedly increased by adding small amounts of fluorides or by fluoride impurities.The radiotracer method after neutron activation was applied to determine the corrosion rates in azeotropic fluoride containing nitric acid. Even minute additions of fluorides strongly affect the corrosion resistance of zirconium. In the range between 0.15 and 10 ppm F- and at a temperature of 108°C, corrosion rates between 5.3 · 10-3 and 3.1 mm/y were measured. It was impossible to establish a limit for the fluoride concentration, below which the corrosion rate of zirconium will not be adversely influenced.The corrosion rates of tantalum and the Ta-40Nb alloy are considerably increasing above a fluoride concentration of 10 ppm. The highest corrosion rates measured were between 8.4 · 10-3 mm/y at 50°C/280 ppm F- and 1.4 · 10-2 mm/y at 110°C/320 ppm F-. Within the range of this investigation, the corrosion resistance of tantalum was higher than that of the Ta-40Nb alloy by one order of magnitude.The corrosion resistance of zirconium and tantalum was not influenced by any treatment of the samples before testing.
    Notes: Wegen ihrer hohen Korrosionsbeständigkeit gegenüber zahlreichen Angriffsmitteln sind Zirconium und Tantal sowie die Legierung Tantal-40Niob von großer technischer Bedeutung. Die bisher in azeotroper Salpetersäure p.a. zwischen 20 und 121°C gemessenen Abtragungsraten liegen für Zirconium zwischen 7 · 10-6 und 5 · 10-4 mm/a, für Tantal zwischen 10-8 und 4 · 10-6 mm/a und für die Legierung Ta-40Nb zwischen 2 · 10-7 und 8 · 10-6 mm/a [1]. Diese Abtragungsraten werden durch geringe Fluoridzustände oder -verunreinigungen wesentlich erhöht.Mit der Radiotracermethode nach Neutronenaktivierung wurden die Abtragungsraten in azeotroper, fluoridhaltiger Salpetersäure bestimmt. Zirconium ist schon gegen kleinste Fluoridspuren sehr empfindlich. Im untersuchten Bereich von 0.15 bis 10 ppm F- liegen bei 108°C die Abtragungsraten zwischen 5.3 · 10-3 und 3.1 mm/a. Eine Grenzkonzentration, unterhalb der das Fluorid die Korrosionsgeschwindigkeit nicht mehr beeinflußt, kann für Zirconium nicht angegeben werden.Bei Tantal und der Legierung Ta-40Nb nimmt oberhalb einer Grenzkonzentration von 10 ppm F- die Korrosionsgeschwindigkeit stark zu. Die höchsten Abtragungsraten liegen zwischen 8.4 · 10-3 mm/a bei 50°C/280 ppm F- und 1.4 · 10-2 mm/a bei 110°C/320 ppm F-. Dabei ist Tantal über den gesamten erfaßten Bereich um etwa das Zehnfache beständiger als die Legierung Ta-40Nb.Sowohl bei Tantal als auch bei Zirconium stellt sich die Abtragungsrate unabhängig von Vorbehandlungen ein.
    Additional Material: 5 Ill.
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  • 4
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The Ti5Ta alloy shows interesting corrosion behaviour and is becoming technologically important, e.g. for chemical plant construction. Welding and further mechanical tests gave good mechanical properties. Therefore, the corrosion of this alloy was studied in comparison with the corrosion of unalloyed Ti and Ta. The samples were corroded for up to 24 days in hot 67.5% nitric acid.The resulting surface layers were investigated with SEM, transmission electron microscopy (TEM), energy dispersive x-ray microanalyses (EDX), AES and sputtered neutral mass spectrometry (SNMS). Under these conditions, the oxide growth seems to be dependent on the orientation of the crystallites at the surface, which was not observed under milder attack. When Ti5Ta samples were immersed for 5 days in boiling HNO3, the oxide layer was ∼300 nm thick and a particular crack pattern developed on some grains during drying in air at room temperature. This was observed only for oxide layers thicker than 300 nm.After corroding Ti5Ta in boiling HNO3 we observed a TaTi atomic ratio of up to 1:1 using ESCA and up to 5 μm thick Ta oxide-rich scales. The selected area diffraction pattern in the TEM indicates that the oxide film may contain mixed Ti/Ta oxides. The extraordinary Ta oxide enrichment, which is due to the selective dissolution process of Ti, is believed to cause the good corrosion resistance of the alloy. It was not observed after heat treatment in air up to 800 °C or after corrosion tests in HNO3 at room temperature.
    Additional Material: 8 Ill.
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  • 5
    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: Solutions and low molecular fractions of the reaction products of thermosetting epoxides based on bisphenol-A-diglycidylether (BADGE) and butane-1,4-diol (BD) with Mg(ClO4)2. 2H2O as accelerator were investigated by means of GPC, FTIR, and high resolution 13C-NMR. Conclusions concerning the development of the structure were drawn.
    Notes: Mittels GPC, FTIR und hochauflösender 13C-NMR wurden Lösungen sowie niedermolekulare Fraktionen der bei der Heißhärtung von Epoxiden auf der Basis von Bisphenol-A-Diglycidethern (BADGE) mit Butan-1,4-Diol (BD) in Gegenwart von Mg(ClO4)2. 2H2O als Beschleuniger entstehenden Reaktionsprodukte untersucht und Aussagen über die Strukturbildung getroffen.
    Additional Material: 6 Ill.
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  • 6
    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 application of radiotracer technique for the determination of small corrosion rates of tantalum, a tantalum-niobium-alloy and zirconium in azeotropic nitric acidThe radiotracer technique following neutron activation is a suitable means to measure hitherto hardly detectable, very low corrosion rates. In azeotropic nitric acid, tantalum and the tantalum-40niobium alloy show at 20 to 120°C approximately the same corrosion rates between 0.2 · 10-6 and 8 · 10-6 mm/a; the apparent activation energies are 30 to 40 kJ/mol.In the temperature region from 20 up to 81°C the corrosion rates of zirconium are between 7 · 10-6 and 5 · 10-4 mm/a; the apparent activation energy is 47 kJ/mol.In the case of zirconium, check measurements (analysis of the corrosive medium with AAS and ICP) with non-activated sheet-metal sections resulted in similar corrosion rates.
    Notes: Die Radiotracer-Methode nach Neutronenaktivierung ist geeignet, bisher kaum erfaßbare, sehr geringe Abtragungsraten zu bestimmen. Tantal und die Tantal-40Niob-Lergierung zeigen in azeotroper Salpetersäure bei 22 bis 120°C annähernd gleiche Abtragungsraten von 0,2 · 10-6 bis 8 · 10-6 mm/a; die scheinbaren Aktivierungsenergien betragen 30 bis 40 kJ/mol.Die Abtragungsraten von Zirconium liegen im Temperaturbereich von 20 bis 81°C zwischen 7 · 10-6 und 5 · 10-4 mm/a; die scheinbare Aktivierungsenergie ergibt sich zu 47 kJ/mol.Im Falle des Zirconiums führten Kontrollmessungen (Analyse des Angriffsmittels mit AAS und ICP) an nicht aktivierten Blechabschnitten zu vergleichbaren Abtragungsraten.
    Additional Material: 5 Ill.
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  • 7
    ISSN: 1057-9257
    Keywords: II-VI compound ; SrS : Ce ; Photoluminescence ; Concentration quenching ; Phosphorescence ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The luminescence efficiency of SrS: Ce powders in the doping range from 0.01 to 1.0 at.% was investigated by photoluminescence decay studies. The radiative decay time of Ce3+ in SrS was determined to be 27 ns. The onset of concentration quenching at concentrations higher than about 0.7 at.% has been obtained. The photoluminescence spectrum of Ce3+ exhibits two emission bands as a consequence of the ground state splitting. The Huang-Rhys factor of the 5d-4f transition was estimated to be about 6. The inhomogeneous broadening of the emission band of samples with higher doping level has been investigated by site-selective and time-resolved spectroscopy.
    Additional Material: 9 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 26 (1992), S. IV 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 64 (1992), S. 864-865 
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 1990-05-01
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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