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  • 1990-1994  (29)
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  • 1
    Electronic Resource
    Electronic Resource
    Precipitation Processes in DC-Cast AlMn(Fe,Si) Alloys (1991)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 44-45 (Jan. 1991), p. 247-256 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/58/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.44-45.247.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    The Effect of Precipitation on the High Temperature Mechanical Properties of DC-Cast AlMn(Fe,Si) Alloys (1991)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 44-45 (Jan. 1991), p. 257-264 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/58/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.44-45.257.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Threshold stress in dispersionally strengthened superplastic Al alloys (1990)
    Springer
    Journal of materials science 25 (1990), S. 4767-4771 
    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 It is important for practical applications that some commercial alloys with stabilized finegrained structure should exhibit superplastic behaviour at high temperatures. In this paper the results of impression creep tests conducted on AlMgZn alloys are reported and the strain rate sensitivity and activation enthalpy were determined. The mechanical behaviour of the alloys as a function of the strain rate sensitivity can be divided into three regions. At low and high stresses the strain rate sensitivity parameter is low and the deformation process is not superplastic. Superplastic deformation takes place only at intermediate stresses. The microstructural interpretation of these processes involves, in general, the change of the micromechanisms controlling the different deformation processes. It was determined that by the supposition of a threshold stress depending strongly on temperature, the two regions due to low and intermediate stresses of the deformation can be described by the same constitutive equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01129939
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  • 4
    Electronic Resource
    Electronic Resource
    Superplasticity of AlMgSi alloys (1992)
    Springer
    Journal of materials science 27 (1992), S. 6141-6145 
    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 Commercial AlMgSi alloy sheets produced by thermomechanical treatment are found to be superplastic between 500 and 570°C at strain rates of 10−5–10−3 −1 The strain rate sensitivity,m, is about 0.4. It was found that the highly alloyed sample contains pre-existing cavities in higher volume fraction than the alloy of lower concentration. An exponential growth of cavity volume fraction was found during superplastic deformation which is characteristic of plasticity controlled cavitation. The growth rate of the cavity volume fraction can be decreased by applying back pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133763
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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of the true activation enthalpy of superplastic flow including a threshold stress (1994)
    Springer
    Journal of materials science 29 (1994), S. 2341-2344 
    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 A new method is suggested for the evaluation of the true activation enthalpy for alloys where the strain rate of the superplastic flow varies with a power of an effective stress σe = σ-σo, where σ and σo are the applied stress and a threshold stress, respectively. Some earlier results concerning superplastic AlMgZnCu alloys containing chromium and in which a strongly temperature-dependent threshold stress can be revealed, are reanalysed. The results are in good agreement with the previous ones. It has been shown further that for the alloys investigated the true activation energy increases with increasing chromium content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00363424
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  • 6
    Electronic Resource
    Electronic Resource
    Bildung siliciumorganischer Verbindungen. 109. Reaktionen vollhydrierter Carbosilane mit LithiumalkylenProfessor Ulrich Wannagat zum 70. Geburtstage gewidmet (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 1491-1493 
    Details
    ISSN: 0044-2313
    Keywords: Reactions of Perhydrogenated Carbosilanes with Alkyl-Lithium ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Formation of Organosilicon Compounds. 109. Reactions of Perhydrogenated Carbosilanes with Alkyl-Lithium CompoundsSi-hydrogenated linear carbosilanes react with MeLi or nBuLi to give the Si-alkylated derivatives. In contrast to the Si-methylated derivatives of (H3Si—CH2)2SiH2 1 and (H3Si)2CH2 2 and to (Me2Si—CH2)3 no lithiation of CH2 groups is observed. Such, 1 with nBuLi yields nBuH2Si—CH2—SiH2—CH2—SiH3 5 and (nBuH2Si—CH2)2SiH2 6. 2 reacts with nBuLi to give nBuH2Si—CH2SiH3 7 and (nBuH2Si)2CH2 8 besides of 1, 5 und 6. The latter results from a cleavage of a Si—C bond in 2 Producing nBuSiH3 and LiCH2—SiH3 which combines with 2 to 1. Subsequently 1 forms 5 and 6. No higher alkylated derivatives of 1 or 2 could be detected.
    Notes: Si-hydrierte, lineare Carbosilane reagieren mit MeLi bzw. nBuLi unter Alkylierung der SiH- und nicht unter Lithiierung der CH2-Gruppen, wie sie von den Si-methylierten Derivaten von (H3Si—CH2)2SiH2 1, (H3Si)2CH2 2 und (Me2Si—CH2)3 bekannt sind. 1 bildet mit nBuLi H3Si—CH2—SiH2—CH2—SiH2nBu 5 und (nBuH2Si—CH2)2—SiH2 6. Die Umsetzung von 2 führt zu H3Si—CH2—SiH2nBu 7 und (nBuH2Si)2CH2 8 neben den Verbindungen 1, 5 und 6. Diese sind auf die Spaltung der Si—C-Bindung in 2 zurückzuführen (Bildung von nBuSiH3 und LiCH2—SiH3). LiCH2—SiH3 reagiert mit 2 zu 1 und diese mit nBuLi weiter zu 5 und 6. Höheralkylierte Derivate von 1 und 2 werden nicht beobachtet. Es erfolgt keine Lithiierung der CH2-Gruppe.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19936190902
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  • 7
    Electronic Resource
    Electronic Resource
    tBu2P—P=P(X)tBu2-Ylide (X = Cl, Br, I) durch Halogenierung von [tBu2P]2P—SiMe3 (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1364-1366 
    Details
    ISSN: 0044-2313
    Keywords: Halogenation of [tBu2P]2P—SiMe3, tBu2P—P=P(X)tBu2 Ylide (X = Cl, Br, I) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: tBu2P—P=P(X)tBu2 Ylides (X = Cl, Br, I) by Halogenation of [tBu2P]2P—SiMe3[tBu2P]2P—SiMe3 1 with halogenating agents as Br2, I2, Br-succinimide, CCl4, CBr4, CI4 or C2Cl6 via cleavage of the Si—P bond in 1 produces the ylides tBu2P—P=P(X)tBu2 (X = Cl, Br, I). This proceeds independent from the formerly known pathway - [tBu2P]2PLi + 1,2-dibromoethane - and shows that the Li-phosphide must not be present as a necessary requirement for the formation of ylides.
    Notes: [tBu2P]2P—SiMe3 1 reagiert mit Halogenierungsmitteln (Br2, I2, Bromsuccinimid, CCl4, CBr4, CI4, C2Cl6) über die Spaltung der Si—P-Bindung in 1 zu den Yliden tBu2P—P=P(X)tBu2 (X = Cl, Br, I). Dieser Weg ist unabhängig von dem bisher bekannten - [tBu2P]2PLi + 1,2-Dibromethan [1] - und zeigt, daß das Li-Phosphid nicht eine unabdingbare Voraussetzung für die Ylidbildung darstellt.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200806
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  • 8
    Electronic Resource
    Electronic Resource
    Reaktionen des tBu(Me3Si)P—P(Li)—P(tBu)2 mit CH3Cl und 1,2-Dibromethan (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1367-1368 
    Details
    ISSN: 0044-2313
    Keywords: tBu(Me3Si)P—P=P(Me)tBu2, tBu(Me3Si)P—P(Br)—P(tBu)2, tBu(Me3Si)P—P=P(Br)tBu2, {tBuP—P[P(tBu)2]}2 from tBu(Me3Si)P—PLi—P(tBu)2 with MeCl or 1,2-Dibromoethane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of tBu(Me3Si)P—P(Li)—P(tBu)2 with CH3Cl and 1,2-DibromoethanetBu(Me3Si)P—P(Li)—P(tBu)2 · 0.95 THF 1 with CH3Cl (-70°C) yields tBu(Me3Si)P—P = P(Me)(tBu)2 2 at -70°C, with 1,2-Dibromoethane tBu(Me3Si)P—PBr—P(tBu)2 3 (main product) and tBu(Me3Si)P—P=P(Br)tBu2 4. 3 eliminates Me3SiBr yielding the cyclotetraphosphane {tBuP—P[P(tBu)2]}2 5.
    Notes: tBu(Me3Si)P—P(Li)—P(tBu)2 · 0,95 THF 1 bildet mit CH3Cl bei -70°C das Ylid tBu(Me3Si)P—P=P(Me)(tBu)2 2, mit 1,2-Dibromethan tBu(Me3Si)P—PBr—P(tBu)2 3 (Hauptprodukt), sowie tBu(Me3Si)P—P=P(Br)tBu2 4. Aus 3 entsteht unter Abspaltung von Me3SiBr das Cyclotetraphosphan {tBuP—P[P(tBu)2]}2 5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200807
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  • 9
    Electronic Resource
    Electronic Resource
    [iPr2P]2P—SiMe3 und [iPr2P]2PLi - Synthese und Reaktionen Struktur des [iPr2P]2P—P[PiPr2]2 (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1369-1374 
    Details
    ISSN: 0044-2313
    Keywords: Synthesis of [iPr2P]2P—SiMe3 1 and [iPr2P]2PLi 2. Reactions of 1 with CBr4, of 2 with 1,2-dibromoethane, and MeCl, yielding iPr2P—P=P(Br)iPr2, [iPrP]2P—P[PiPr2]2, iPr2P—P=P(Me)iPr2, crystal structure of Tetrakis(di-isopropyl-phosphino)diphosphane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: [iPr2P]2P—SiMe3 and [iPr2P]2PLi - Synthesis and Reactions Structure of [iPr2P]2P—P[PiPr2]2[iPr2P]2P—SiMe3 1 and [iPr2P]2PLi 2 were prepared to investigate the influence of the bulky alkyl groups on formation and properties of the ylides R2P—P=P(X)R2 (R = iPr, tBu; X = Br, Me) in reactions of 1 with CBr4 and of 2 with 1,2-dibromoethane or MeCl, resp. Compared to the iPr groups the tBu groups favour the formation of ylides. With CBr4 1 forms iPr2P—P=P(Br)iPr2 5 just as a minor product which decomposes already below -30°C. With 1,2-dibromoethane 2 yields only traces of 5 but [iPr2P]P—P[P(iPr)2]2 7 as main product. With MeCl 2 gives iPrP—P=P(Me)iPr2 9 and [iPr2P]2PMe 10 in a molar ratio of 1:1. 9 is considerably more stable than 5. 7 crystallizes triclinic in the space group P1 (No. 2) with a = 10.813 Å, b = 11.967 Å, c = 15.362 Å, α = 67.90°, β = 71.36°, γ = 64.11° and two formula units in the unit cell.
    Notes: [iPr2P]2P—SiMe3 1 und [iPr2P]2PLi 2 wurden synthetisiert. Die Umsetzungen von 1 mit CBr4 und von 2 mit 1,2-Dibromethan bzw. MeCl ermöglichen einen Vergleich des Einflusses der iPr- bzw. tBu-Gruppen auf Bildung und Eigenschaften der Ylide R2P—P=P(X)R2 (R = iPr, tBu; X = Br, Me) bei analogen Reaktionen.Die tBu-Gruppe begünstigt gegenüber der iPr-Gruppe die Ylidbildung. 1 bildet mit CBr4 das iPr2P—P=P(Br)iPr2 5 als Nebenprodukt, das sich schon unterhalb -30°C zersetzt. 2 bildet mit 1,2-Dibromethan das Ylid 5 nur in Spuren, aber [(iPr)2P]2P—P[P(iPr)2]2 7 als Hauptprodukt. 2 reagiert mit MeCl zum iPr2P—P=P(Me)iPr2 9 und [iPr2P]2PMe 10 im Molverhältnis 1:1. 9 ist erheblich beständiger als 5. 7 kristallisiert triklin in P1 (Nr. 2) mit a = 10,813 Å, b = 11,967 Å, c = 15,362 Å, α = 67,90°, β = 71,36°, γ = 64,11°. Die Elementarzelle enthält zwei Formeleinheiten.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200808
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  • 10
    Electronic Resource
    Electronic Resource
    Zur Bildung und Struktur der Phosphinophosphiniden-phosphorane tBu2P—P=P(Me)tBu2 1, tBu(Me3Si)P—P=P(Me)tBu2 2 und tBu2P—P=P(Br)tBu2 3Professor Kurt Issleib in memoriam (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 2033-2040 
    Details
    ISSN: 0044-2313
    Keywords: Phoshinophosphinidene-phosphoranes, tBu2P—P=P(Me)tBu2, tBu(Me3Si)P—P=P(Me)tBu2, tBu2P—P=P(Br)tBu2 ; Synthesis ; Structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structure of Phosphinophosphinidene-phosphoranes tBu2P—P=P(Me)tBu2 1, tBu(Me3Si)P—P=P(Me)tBu2 2, and tBu2P—P=P(Br)tBu2 3A new method for the synthesis of 1 and 2 (Formulae see „Inhaltsübersicht“) is reported based on the reaction of 5 with substitution reagents (Me2SO4 or CH3Cl). The results of the X-ray structure determination of 1 and 2 are given and compared with those of 3. While in 3 one P—P distance corresponds to a double bond and the other P—P distance to a single bond (difference 12.5 pm) the differences of the P—P distances in 1 and 2 are much smaller: 5.28 pm in 1, 4.68 pm in 2. Both 1 and 2 crystallize monoclinic in the space group P21/n (Z = 4). 2 additionally contains two disordered molecules of the solvent pentane in the unit cell. Parameters of 1: a = 884.32(8) pm, b = 1 924.67(25) pm, c = 1 277.07(13) pm, β = 100.816(8)°, and of 2: a = 1 101.93(12) pm, b = 1 712.46(18) pm, c = 1 395.81(12) pm, β = 111.159(7)°, all data collected at 143 K. The skeleton of the three P atoms is bent (PPP angle 100.95° for 1, 100.29° for 2 and 105.77° for 3). Ab initio SCF calculations are used to discuss the bonding situation in the molecular skeleton of the three P atoms of 1 and 3. The results show a significant contribution of the ionic structure R2P—P(-)—P(+)(X)R2. The structure with (partially) charged P atoms is stabilized by bulky polarizable groups R (as tBu) as compared to the fully covalent structure R2P—P(X)—PR2.
    Notes: Es wird ein neuer Weg zur Bildung von tBu2P—P=P(Me)tBu2 1 und tBu(Me3Si)P—P=P(Me)tBu2 2 mitgeteilt, der auf der Umsetzung von LiP[P(tBu)2]2 5 mit Substitutionsreagenzien (Me2SO4, CH3Cl) basiert. Die Ergebnisse der Kristallstrukturuntersuchung von 1 und 2 werden mitgeteilt und mit denen des tBu2P—P=P(Br)tBu2 3 verglichen. Während in 3 der eine Abstand einer Doppelbindung entspricht und der andere einer Einfachbindung (Differenz 12,5 pm) sind die Differenzen der P—P-Abstände in 1 und 2 weit geringer, in 1 5,28 pm, in 2 4,68 pm. 1 und 2 kristallisieren beide monoklin in der Raumgruppe P21/n mit vier Formeleinheiten in der Elementarzelle. Bei 2 werden zusätzlich zwei fehlgeordnete Moleküle des Lösungsmittels Pentan in der Elementarzelle eingebaut. Parameter von 1: a = 884,32(8) pm, b = 1 924,67(25) pm, c = 1 277,07(13) pm, β = 100,816(8)°, 2: a = 1 101,93(12) pm, b = 1 712,46(18) pm, c = 1 395,81(12) pm, β = 111,159(7)°, jeweils bei der Meßtemperatur 143 K. Das Gerüst der drei P-Atome ist gewinkelt, Winkel in 1 100,95°, in 2 100,29° und in 3 auf 105,77° aufgeweitert. Mit Hilfe von ab initio SCF-Rechnungen werden die Bindungsverhältnisse im Molekülgerüst der drei P-Atome in 1 und 3 diskutiert. Es zeigt sich ein deutlicher Beitrag der ionogenen Struktur R2P—P(-)—P(+)(X)R2. Die Struktur mit separierten (Teil-)Ladungen wird durch große, polarisierte Gruppen R wie tBu im Vergleich zur (unpolaren) normalvalenten Verbindung R2P—P(X)—PR2 stabilisiert.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946201204
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