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  • Polymer and Materials Science  (15)
  • 61.40  (3)
  • STRUCTURAL MECHANICS  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 54 (1992), S. 40-46 
    ISSN: 1432-0630
    Keywords: 61.40 ; 71.55 ; 82.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Amorphous (a-) semiconductors like a-Si:H and the chalcogenide glasses possess a general tendency to establish an overall equilibrium between the electronic system and the lattice with its dopant and defect sites. In the present paper the chemical interactions which establish these equilibria within the bulk of the a-semiconductor lattices are compared to chemical interactions in liquid electrolytes, particularly to those in H2O. These considerations reveal close similarities between autocompensation doping in a-semiconductors and acid/base reactions in H2O. The effects of light and field-effect induced defect formation, on the other hand, are shown to be related to the phenomenon of electrolysis in H2O. The consideration of these analogies further emphasizes the roles of charge-carrier localization and that of H-diffusion in promoting dopant and defect equilibration reactions in a-semiconductors.
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  • 2
    ISSN: 1432-0630
    Keywords: 61.40 ; 61.80 ; 72.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract n-type a-Si:H films have been irradiated with light, electrons, protons and heavy ion beams. It is shown that the non-thermal creation of dangling-bond defects activates significant densities of previously inactive phosphorus dopants. The relevance of these results is discussed with respect to equilibration phenomena in doped material and with respect to degradation phenomena in a-Si:H solar cells.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 53 (1991), S. 235-240 
    ISSN: 1432-0630
    Keywords: 61.40 ; 61.80 ; 72.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Hydrogenated amorphous silicon (a-Si:H) films have been irradiated with H+, B+, P+, and Ar+ ion beams. The accumulation and the annealing of irradiation-induced defects has been investigated through a series of electronic transport and PDS measurements. We find that for all projectiles damage accumulation is dominated by atomic displacement collisions with the damage saturating for energy transfers in excess of about 10 eV/target atom. Annealing at elevated temperatures causes the conductivity of doped and irradiated a-Si:H films to increase according to stretched exponential decay curves. All annealing parameters derivable from such fits scale with the energy originally dissipated into atomic displacement collisions. For energy transfers up to 10 eV/target atom the activation energy for annealing increases up to a saturation value and, at the same time, an increasing fraction of the irradiation-induced defects becomes stable against annealing at moderate temperatures (T a〈250° C). We discuss these results with respect to damage accumulation data in crystalline silicon (c-Si) and with regard to the annealing of metastable defects in a-Si:H.
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  • 4
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    In:  CASI
    Publication Date: 2016-06-07
    Description: Apollo project - progress and national benefits
    Keywords: STRUCTURAL MECHANICS
    Type: Proceedings of the Fourth National Conference on the Peaceful Uses of Space; NASA-SP-51
    Format: application/pdf
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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: 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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  • 6
    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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  • 7
    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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  • 8
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A model system was developed to study the influence of the rubber formulation and/or the aging conditions on the adhesion between brass and rubber. The bonding compounds were vulcanized on thin, homogeneous brass layers that had been prepared by sputtering onto special polymeric substrates; some of these compounds were steam-aged under controlled conditions subsequently. After the separation of the polymeric film, combined analytical electron microscopy (transmission electron microscopy/energy dispersive spectroscopy; TEM/EDS) and sputter neutral mass spectrometry (SNMS) analyses were performed. While the TEM/EDS studies offer a detailed insight into the morphological structure of the interphase, the SNMS depth profiles allow a rapid and reliable differentiation between various rubber formulations. With these model samples the beneficial effect of boric acid esters on the adhesion of cobalt-containing bonding compounds, which is observed in a typical short-term adhesion test after steam-aging, can be explained: boric acid esters act with cobalt salts as corrosion inhibitors for brass, preventing the growth of a thick intermediate ZnO/Zn (OH)2 layer that is the starting point for delaminations.
    Additional Material: 7 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: The extinction coefficients of the CH3 deformation vibrations of short chain branchings in saturated polymeric hydrocarbons was determined in dependence on the length of side chains in model substances. The number of CH2 groups arranged between the main chain and methyl group of alkyl branchings affects essentially the intensity of the absorption at 1378 cm-1. The results were applied in the quantitative evaluation of CH3 vibrations for the calculation of the number of branchings in high pressure polyethylene.
    Notes: Die Extinktionskoeffizienten der CH3-Deformationsschwingung von kurzen Kettenverzweigungen in gesättigten polymeren Kohlenwasserstoffen wurden in Abhängigkeit von der Seitenkettenlänge an Modellsubstanzen ermittelt. Die Zahl der CH2-Gruppen, die sich zwischen Hauptkette und Methylgruppe der Alkylverzweigung befinden, beeinflußt wesentlich die Intensität der Absorption bei 1378 cm-1. Die Ergebnisse werden auf die quantitative Auswertung der CH3-Schwingung zur Berechnung von Verzweigungszahlen im Hochdruckpolyethylen angewendet.
    Additional Material: 4 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: The short chain branching in low density polyethylene obtained under various conditions were determined by γ-irradiation followed by gaschromatography of the gaseous scission products. The pressure and temperature of polymerization were found to affect the kind and number of branchings. The branching structure and reaction parameters are related and discussed on a kinetic concept.
    Notes: Die Kurzkettenverzweigung von unter verschiedenen Bedingungen synthetisierten Hochdruckpolyethylenen wurde mit Hilfe der γ-Bestrahlung und nachfolgender gaschromatographischer Analyse der Spaltgase bestimmt. Es wurde experimentell belegt, daß Reaktionsdruck und Polymerisationstemperatur Art und Anzahl der Seitenzweige beeinflussen. Verzweigungsstruktur und Reaktionsparameter werden zueinander in Beziehung gesetzt und auf der Grundlage kinetischer Überlegungen diskutiert.
    Additional Material: 11 Ill.
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