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  • 1
    Digitale Medien
    Digitale Medien
    Composition-Graded Solid Electrolyte for Determination of the Gibbs Energy of Formation of Lanthanum Zirconate (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: A composition-graded solid electrolyte has been used to determine the standard Gibbs free energy of formation of lanthanum zirconate (La2Zr2O7) from the component oxides lanthana (La2O3) (A-rare earth) and zirconia (ZrO2) (monoclinic) in the temperature range of 870–1240 K. The cell used for measurement can be represented as Pt, O2, CaO + CaF2∥ CaF2| (LaF3)x(CaF2)1-x∥LaF3+ La2Zr2O7+ ZrO2, O2, Pt x=0 x=0.32 A composition-graded electrolyte has been introduced to compensate the solubility effects of the electrode material (lanthanum fluoride, LaF3) in the solid electrolyte (calcium fluoride, CaF2). The ability of the graded electrolyte to gen-erate a Nernstian response is demonstrated, using electrodes with known fluorine chemical potentials. For the reaction La2O3 (A-rare earth) + 2ZrO2 (monoclinic) → La2Zr2O7 (pyrochlore), the Gibbs free energy change (ΔG°f,ox) is given by the formula −133800 −10.32T (±4500) (in units of J/mol). The enthalpy and entropy of formation of La2Zr2O7 obtained in this study are in good agreement with calorimetric data. The “third-law” enthalpy of formation of La2Zr2O7, from the component oxides at 298.15 K, is −133.8 ± 5 kJ/mol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02568.x
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  • 2
    Digitale Medien
    Digitale Medien
    Solid-State Immiscibility and Thermodynamics of the Calcium Oxide-Strontium Oxide System (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: Solid-state miscibility gap in the pseudo-binary calcium oxide-strontium oxide (CaO-SrO) system is delineated by X-ray diffractometry studies on samples equilibrated either under vacuum or in a flowing inert-gas atmosphere at temperatures of 973-1273 K. For the CaxSr1−xO solid solution, an asymmetric phase boundary that is characterized by a critical temperature of 1173 (±3) K and a composition of x= 0.53 (±0.01) is obtained. The excess Gibbs energy of mixing of the solid solution, which is derived from the experimental phase-boundary compositions and temperatures, can be represented by the expression ΔGE=x (1−x)[(27040 − 5.82 T) x+ (24915 − 5.34 T)(1 −x)] (in units of J/mol). It is necessary to include excess entropy terms to obtain a good fit to the experimental data. The chemical spinodal curve is computed from the thermodynamic parameters. The results obtained in this study are compared with phase-diagram and calorimetric information that is available in the literature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02451.x
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  • 3
    Digitale Medien
    Digitale Medien
    Electrochemical Determination of the Gibbs Energy of Formation of MgAl2O4 (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: The standard Gibbs energy of formation of the spinel MgAl2O4 from component oxides, MgO and α-Al2O3, has been determined in the temperature range 900 to 1250 K using a solid-state cell incorporating single-crystal CaF2 as the solid electrolyte. The cell can be represented as—Pt,O2,MgO+MgF2|CaF2|MgF2+MgAl2O4+α-Al2O3,O2,Pt—The standard Gibbs energy of formation from binary oxides, computed from the reversible emf, can be represented by the expression—capdeltaG°f,ox=−23600 − 5.91T(±150) J/mol—The ‘second-law’ enthalpy of formation of MgAl2O4 obtained in this study is in good agreement with high-temperature solution calorimetric studies reported in the literature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02316.x
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  • 4
    Digitale Medien
    Digitale Medien
    Haploidy in Jute ( Corchorus olitorius L.) (1961)
    [s.l.] : Nature Publishing Group
    Nature 192 (1961), S. 288-289 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] From a selection of X-ray-irradiated progenies of 70,000 r. treatment of the X, generation of Gor-ohorua olitorius (i7.nO 632) in 1960, seven variants were found from a culture of healthy, vigorously growing normal plants. These plants with comparatively slender stom and small leaves were very ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/192288b0
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  • 5
    Digitale Medien
    Digitale Medien
    Heterobimetallische Vanadium- und Thallium-2-(dimethylaminomethyl)ferrocenyl-Verbindungen (1997)
    Springer
    Monatshefte für Chemie 128 (1997), S. 337-351 
    Details
    ISSN: 1434-4475
    Schlagwort(e): Vanadium ; Thallium ; Heterobimetallic ; 2-(Dimethylaminomethyl)ferrocenyl ; Orthometallation ; Electron transfer ; Möβbauer spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Summary Syntheses and properties of 2-(dimethylaminomethyl)ferrocenylderivatives of the composition (FcN) n VCl3−n (FcN=2-(dimethylaminomethyl)ferrocenyl;n=1 (1), 2 (2), 3 (3)), which are formed from VCl3·3THF and (FcN) Li (I), are reported. WhereasCp 2VCl2 (Cp=C5H5) reacts withI under formation ofCp 2V(FcN) (4), VO(acac)2 (acac=anion of acetylacetonate, C5H7O2) can be transformed into the 2-(dimethylaminomethyl)-ferrocenyl compound of tetravalent vanadium (FcN)VO(acac),5). However, when VOCl2·2THF reacts withI, the organovanadium(III)-derivative Li[(FcN)2V(O)Cl] (6) is formed. Reactions of VCl4·2THF,Cp 2VCl2, VOCl3, andCpVOCl2 with (FcN)3Tl (II) lead to thermally instable vanadiumorganic compounds under formation of (FcN)2TlCl (7). A detailed characterization of1–7 was carried out by elementary analysis, determination of effective magnetic moments, IR, mass and1H NMR spectroscopy as well as — especially referring to the formation of possible chelate structures — by UV/Vis andMöβbauer spectroscopy.
    Notizen: Zusammenfassung Synthesen und Eigenschaften von 2-(Dimethylaminomethyl)ferrocenyl-Derivaten der Formel (FcN) n VCl3−n (FcN=2-(Dimethylaminomethyl)ferrocenyl;n=1 (1), 2 (2), 3 (3)), die aus VCl3·3THF und (FcN) Li (I) entstehen, werden mitgeteilt. WährendCp 2VCl2 (Cp=C5H5) mitI unter Bildung vonCp 2 V(FcN) (4) reagiert, läßt sich VO (acac)2 (acac=Anion des Acetylacetonates, C5H7O2) in die 2-(Dimethylaminomethyl)ferrocenyl-Verbindung des vierwertigen Vanadiums (FcN)VO(acac),5) überführen. Dagegen entsteht bei Umsetzungen von VOCl2·2THF mitI das Organovanadium (III)-Derivat Li [(FcN)2V(O)Cl] (6). Reaktionen von VCl4·2THF,Cp 2VCl2, VOCl3 undCpVOCl2 mit (FcN)3Tl (II) führen unter Bildung von (FcN)2TlCl (7) zu thermisch instabilen vanadiumorganischen Verbindungen. Eine eingehende Charakterisierung von1–7 erfolgte durch Elementaranalysen, Ermittlung der effektiven magnetischen Momente, IR-, Massen- und NMR-Spektroskopie sowie, insbesondere hinsichtlich der Ausbildung möglicher Chelatstrukturen, durch UV/Vis und Mößbauer-Spektroskopie.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00810770
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  • 6
    Digitale Medien
    Digitale Medien
    Heterobimetallische [(2-Dimethylaminomethyl)ferrocenyl](pentamethylcyclopentadienyl)-Komplexe der Lanthanoide: Synthesen und Mößbauer-Untersuchungen (1997)
    Springer
    Monatshefte für Chemie 128 (1997), S. 165-175 
    Details
    ISSN: 1434-4475
    Schlagwort(e): Organolanthanides ; Heterobimetallic complexes ; Ferrocene ; Mößbauer spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Reactions of 2-(dimethylaminomethyl)ferrocenyl-lithium ((FcN)Li,1) with various cerium(IV) precursors lead to the formation of heterobimetallic organocerium(III) complexes. The compounds Li3[(FcN)2CeF4(THF)3] (2), (FcN)2CeF(DME)2 (3), Li4[(FcN)CeCl6] (4), and Li[(FcN)CeCl3(DME)] (5) have been isolated by redox reactions. Similar treatment of (C5Me5)2 Ce(μ-Cl)2K(THF)2 with one equivalent of1 affords the neutral species (C5Me5)Ce(FcN)Cl (6)via displacement of one C5Me5 ligand. Complexes of the type (C5Me5)Ln(FcN)Cl have also been isolated forLn=Pr (7), Nd (8), and Sm (9). These and related heterobimetallic lanthanideFcN complexes have been studied by Mößbauer spectroscopy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807305
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  • 7
    Digitale Medien
    Digitale Medien
    Berechnung der Potentialströmung um Profile mit Absaugung und Ausblasen (1963)
    Springer
    Archive of applied mechanics 32 (1963), S. 51-65 
    Details
    ISSN: 1432-0681
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00536502
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  • 8
    Digitale Medien
    Digitale Medien
    Self-organization of recent rhythmic iron-manganese precipitations in underground mines in the Harz mountains (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 29-37 
    Details
    ISSN: 1437-3262
    Schlagwort(e): Banded mineralization ; Harz mountains ; Self-organization ; Iron, manganese, ferrihydrite, birnessite ; Time-series analysis ; Aquatic systems ; Iron bacteria ; Ostwald ripening
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract A recent early diagenetic banded iron-manganese mud has been forming underground in a closed lead-zinc mine for approximately 40 years. The processes leading to the banded structure of the precipitate were studied during a period of 2 years. Therefore, 19 physical and chemical parameters were measured regularly in short intervals. The resulting time series were analysed with respect to the data sets of the monthly chemical analyses of the descendent mine water, the daily rainfall and the mineral content. The results reveal that the precipitated material undergoes internal self-organization due to interaction of redox, colloid-chemical, microbial, electrical and ripening processes, and not exclusively produced by seasonal fluctuations of material input. Thus, the primary banding of the material, caused by externally forced fluctuations of the redox conditions within the mine water, is reorganized after a short time. The finally observed bands are controlled by non-linear coupling of reaction and transport processes within the mud. A genetic model for the banded mineralization was developed and verified by numerical simulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00192057
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  • 9
    Digitale Medien
    Digitale Medien
    Morphological instabilities in pattern formation by precipitation and crystallization processes (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 19-28 
    Details
    ISSN: 1437-3262
    Schlagwort(e): Anastomoses ; Crystal zoning ; Snow bands ; Liesegang rings ; Ostwald ripening ; Self organization ; Siderite ; Supersaturation theory ; Zebra rock
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract Morphological instabilities in periodic patterns occurring both in precipitation and crystallization processes (Liesegang rings and crystal zoning) are investigated and compared with similar patterns in geological samples (zebra rocks and mud bands in snow sediments). In classical Liesegang systems, undisturbed parallel or concentric precipitation bands are emanated from even or concentric diffusion sources in homogeneous diffusion matrices of gelatine or other gels. In the case of superposing diffusion sources, sources with undulatory curvatures or local diffusion barriers there may occur several types of instabilities within the sequence of regular patterns: (a) gaps within the bands forming radial alleys free of precipitate, (b) transition from broken bands to speckled patterns and (c) apparent branching of bands linked together by so-called anastomoses. Calculations with a competitive particle growth (CPG) model show that lateral instabilities in Liesegang bands (gaps and radial alleys of gaps) are the result of Ostwald ripening effects taking place after precipitation. Apparent branching of bands or formation of anastomoses can be simulated with a prenucleation model according to Ostwald's supersaturation theory. Similar irregularities can be observed in zebra rocks (e.g. banded siderite) whose bandings are commonly explained by sequential sedimentation processes. A very different mechanism is assumed to be responsible for the origin of mud bands in snow sediments. An initially homogeneous distribution of intrinsic mud in snow sediments can be arranged into parallel bands according to a crystal zoning mechanism which is based on repeated thawing and freezing of the snow sediment due to the daily alternation of sun and darkness.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00192056
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  • 10
    Digitale Medien
    Digitale Medien
    Phosphorus distribution profiles in 100-silicon using a spin-on source at low temperatures (1996)
    Springer
    Applied physics 64 (1996), S. 77-81 
    Details
    ISSN: 1432-0630
    Schlagwort(e): PACS: 66; 81.40
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract.  Incorporation of phosphorus into silicon from a spin-on dopant layer (SOD) at 400 °C is described. Annealing experiments were carried out with SOD films deposited on (100) silicon substrates by using the spin-on technique. Conventional heating on a hotplate in normal atmosphere and a temperature range up to 400 °C was used to study the dopant incorporation. After removing the SOD-films one part of the silicon substrates was annealed at higher temperatures. Investigations were carried out by SIMS, SAM, XPS, HTEM, stripping Hall and Van der Pauw measurements before and after the high temperature annealing. Chemical phosphorus concentration profiles obtained from low temperature annealed samples showed diffusion depths of 60–80 nm (extrapolated to a substrate doping level of 1016 cm-3) and surface concentrations of 1019–1020 cm-3. Electron concentration profiles exhibiting maximum values around 2⋅1019 cm-3 could be measured on high temperature annealed samples only.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003390050447
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