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  • 1
    Electronic Resource
    Electronic Resource
    Initiation of Self-Propagating Combustion Waves in Dense Mo + 2Si Reactants through Field-Activation (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Because of kinetic limitations, self-sustaining combustion synthesis reactions cannot be initiated in dense powder compacts. In compacts of Mo + 2Si, self-propagating waves can be initiated in samples with less than 78% relative density. At this and higher densities, no waves could be initiated without field-activation. In the presence of an electric field (at values of 7 and 13 V·cm-1), reactant compacts with densities up to 95% could sustain a combustion wave to produce MoSi2. In the absence of a field (for lower-density samples) the wave propagated in a non-steady-state (pulsating) mode, while under the influence of a field the wave propagated in a steady-state mode. The dependences of wave velocity and combustion temperature on the relative density of the reactants were qualitatively similar, showing maxima at a relative density of about 65%. These observations are explained in terms of the contribution of a liquid phase in the MoSi2-Mo5Si3 binary to the synthesis kinetics. Although not detected by X-ray diffraction analysis, small amounts of Mo5Si3 were discerned at the grain boundaries of the MoSi2 product. The particle size of the silicide synthesized from 95% dense reactants was significantly smaller than those synthesized from reactants with lower densities, but the reason for this observation is not well understood at this time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01937.x
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  • 2
    Electronic Resource
    Electronic Resource
    Field-assisted self-propagating synthesis of β-SiC (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1927-1928 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the effect of an electric field on the self-propagating reaction between silicon and carbon to synthesize β-SiC. In the absence of a field at a threshold level, no self-sustaining reaction is observed, and as the applied voltage increases, a linear increase in the velocity of the reaction wave is observed. This first demonstration of the effect of fields on such reactions is explained in terms of a model in which the role of the field is confined to the reaction zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357677
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  • 3
    Electronic Resource
    Electronic Resource
    Buried monocrystalline aluminum layers in beryllium using ion implantation (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2651-2653 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A buried monocrystalline aluminum layer was formed in (101¯0) beryllium by implanting 200 keV Al+ to a dose of 1.1×1018 Al/cm2 and subsequently annealing the implanted beryllium at 500 °C for 1 h. Rutherford backscattering showed layer formation was critically dependent on aluminum dose. Electron microscopy revealed a correlation between this critical dependence and the dose dependence of the density of columnar beryllium defects extending through the aluminum layers from the beryllium overlayer to the beryllium bulk. Several common features found between the formation of this elemental layer and formation of buried compound layers strongly suggest that similar precipitate coarsening behavior is responsible for both.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103793
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of a nearly pure aluminum layer in beryllium using ion implantation (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 326-328 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A nearly pure subsurface layer of an implanted element was created using aluminum implantation into beryllium. In particular, post-implant annealing of polycrystalline beryllium samples implanted with 200 keV aluminum caused a dramatic increase in the peak aluminum concentration as determined by Rutherford backscattering. The effect was observed for all three doses studied: 0.46, 1.1, and 4.6×1018 Al/cm2 . For the 1.1×1018 Al/cm2 case, cross-sectional transmission electron microscopy of the annealed sample revealed a distinct subsurface layer with the structure of crystalline aluminum. Auger sputter profiles of individual grains showed the layer purity to be as high as 98 at. % aluminum. However, there were indications that the layer formation and/or purity were grain dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100977
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  • 5
    Electronic Resource
    Electronic Resource
    The propagation of a solid-state combustion wave in Ni-Al foils (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5039-5045 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of thin foils to investigate the propagation of a combustion wave has been demonstrated for the nickel-aluminum system. The initiation of a reaction wave in the foils was found to be triggered by the melting of nickel regardless of the composition of the foil ensemble. In contrast, the propagation rate decreased with increasing nickel content in the foil ensemble. Considerable interactions, observed in advance of the combustion front, are contrary to assumptions made in existing models on the dynamics of self-sustaining reactions. The nature and sequence of reactions between foils of Ni and Al and their relationship to the combustion front were determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343777
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of Dense, High-Defect-Concentration B4C through Mechanical Activation and Field-Assisted Combustion (2004)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 87 (2004), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dense fine-grained B4C was synthesized by the spark plasma sintering (SPS) method using mechanically activated elemental powders. Relative densities of up to 95% were achieved. When characterized by X-ray line broadening methods, the grains of the resulting product were determined to be nanometric in scale. However, transmission electron microscopy (TEM) observations showed the product to be composed of a mixture of fine (nanometric) crystallites and grains in the micrometer range. The TEM images showed a highly defective structure containing a high density of twins. Their presence is the reason for the discrepancy between the X-ray and TEM results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.00779.x
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  • 7
    Electronic Resource
    Electronic Resource
    Simultaneous dynamic thermogravimetry and mass spectrometry of the evaporation of alkali metal nitrates and nitrites (1983)
    Springer
    Journal of thermal analysis and calorimetry 27 (1983), S. 401-408 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Sechs Alkalimetallnitrate und -nitrite wurden in Vakuum, bei konstanter Erwärmungsgeschwindigkeit in einer kombinierten massenspektroskopischen und thermogravimetrischen Vorrichtung verdampft. Für LiNO3, NaNO3, KNO3, Na/KNO3, NaNO2 und KNO2 wurden die zeitzerlegten Profile der Zersetzungsgase, sowie die Kinetik erhalten. Für die Verdampfung dieser Salze wurden die Aktivationsenergien berechnet, und mit früheren Ergebnissen der isothermischen Versuche verglichen. In dem Temperaturbereich 650 bis 850 K wird von den zerfallenden Nitraten NO, N2 und O2 befreit, die Nitrite entwickeln dagegen nur NO und N2.
    Abstract: Резюме Шесть нитратов и нитр итов щелочных металл ов были испарены в вакуу ме в обьединенном совмещ енном МС-ТГ приборе пр и постоянной скорости нагрева. Временно-раз решенные профили разложения г азов и кинетика реакц ии были получены для LiNO3, NaNO3, KNO3, Na/KNO3, NaNO2 и KNO2. Вычислены э нергии активации реакции испарения этих солей и сопостав лены с предыдущими ре зультатами изотермических изме рений. Разложение нитратов в температурной обла сти 650–850 К происходит с выделен ием моноокиси азота, азота и кислоро да, а нитритов — моноок иси азота и азота.
    Notes: Abstract Six alkali metal nitrates and nitrites were evaporated in vacuum at a constant heating rate in a combined mass spectrometric and thermogravimetric apparatus. Time resolved profiles of decomposition gases and kinetics were obtained for LiNO3, NaNO3, KNO3, Na/KNO3, NaNO2 and KNO2. Activation energies for the evaporation of these salts were calculated and compared to previous results of isothermal experiments. In the temperature range 650–850 K, the decomposing nitrates released NO, N2 and O2 while the nitrites released only NO and N2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01914677
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  • 8
    Electronic Resource
    Electronic Resource
    The decomposition of iron(III) sulfate in air (1989)
    Springer
    Journal of thermal analysis and calorimetry 35 (1989), S. 967-976 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Anfänglich hydratiertes Eisen(III)-sulfatpulver wurde in Luft im Temperaturbereich 823–923 K zersetzt. Für die Reaktionsordnung des Zersetzungsprozesses, der als Endprodukt festes Fe2O3 lieferte, wurde Null und für die Aktivierungsenergie 219 kJ·mol−1 ermittelt. Die Art des Produktes und der Kinetik der Zersetzung war in Luft und Argon gleich. Unter den gleichen Bedingungen wurden auch Sulfatproben mit Zusätzen von FeS und Fe2O3 zersetzt. Die Ergebnisse bekräftigen sowohl die nullte Reaktionsordnung (im Falle von Fe2O3 Zusätzen) als auch einen fehlenden Einfluß von FeS auf die Zersetzung von Eisen(III)-sulfat.
    Abstract: Резюме Разложение гидратир ованных порошков сульфата трехвалент ного железа было проведено при темпер атуре 823–923 К в воздушной атмосфере. Показано, что реакция разложения, приводящ ая к образованию твер дого оксида трехвалентного желе за, имеет нулевой порядок с энергией ак тивации равной 219 кдж·м оль−1. В атмосфере воздуха и а ргона характер образующихся продук тов и кинетика процес са разложения были один аковыми. Образцы сульфата железа с доб авками FeS и Fe2O3 были также подвергнуты разложе нию в аналогичных условиях. Результаты подтвердили нулевой порядок реакции (в случае доба вки Fe2O3) и отсутствие какого-ли бо влияния сульфида двухвалентного желе за на разложение суль фата железа.
    Notes: Abstract The decomposition of initially hydrated powders of iron(III) sulfate was carried out in air over the temperature range 823–923 K. The decomposition process, which gave Fe2O3 as a solid product, was seen to have zero-order kinetics and an activation energy of 219 kJ·mol−1. The nature of the product and the kinetics of decomposition were the same for samples decomposed in air and in argon. Sulfate samples with additives of FeS and Fe2O3 were also decomposed under similar conditions and the results confirmed the zero-order kinetics (for the case of the Fe2O3 additives) and the lack of effect of FeS on the decomposition of iron(III) sulfate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02057253
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  • 9
    Electronic Resource
    Electronic Resource
    Cyclic reduction-oxidation of haematite powders (1989)
    Springer
    Journal of materials science 24 (1989), S. 3913-3923 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The cyclic reduction-oxidation of haematite (Fe2O3) powders was investigated over the temperature range 723 to 873 K. The hydrogeon reduction of haematite had an approximate activation energy of 53 KJ mol−1. The air oxidation of the resulting iron gave a product whose composition depended on the thermal history of the sample (number of cycles and temperature). At the lowest cycling temperature (723 K) the primary oxide was Fe3O4 and the only influence of cycling was on the relative amount of unreacted iron. At the higher temperatures (798 and 873 K) the primary oxide was Fe2O3 at the end of one cycle but changed to Fe3O4 for a higher number of cycles. The effect of cycling is explained in terms of sintering during both the reduction and oxidation reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01168954
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  • 10
    Electronic Resource
    Electronic Resource
    Interfacial reactions between thin metal films and polar {0001} oriented CdS substrates (1992)
    Springer
    Journal of materials science 27 (1992), S. 1149-1156 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The interaction between thin films of copper and gold and polar {0001} substrates of CdS was investigated. The out-diffusion of sulphur into the copper film resulted in a broad interface, but because of relatively weak sulphur-copper bonding, chemical trapping was not observed. For both cases (Cu-CdS and Au-CdS) no difference in behaviour was observed between the A (0001) and B (000¯1) oriented CdS substrates. The non-stoichiometric out-diffusion of the substrate components (S and Cd) into the Cu, Au, and AL was similar to the case when III–V compounds were the substrates. The dependence of the Cd/S concentration ratio on metal film thickness showed a clear division between reactive and non-reactive metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01142011
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