Interdiffusion in the Co-Ni system-I concentration penetration curves and interdiffusion coefficients

The interdiffusion in the Co-Ni system has been investigated in the temperature range of 950 to 1150 °C, by means of diffusion specimens of pure Co and Ni. The concentration curvesN(x, t) obtained with the aid of an JXA-3 A JEOL electron microprobe were evaluated using the smoothing cubic spline method by means of the Boltzmann-Matano equation. The obtained interdififusion coefficient values ¯D increase with the increasing Ni concentration and satisfy the Arrhenius equation at temperaturesH 990 °C. At lower temperatures the influence of high diffusivity paths may be effective, resulting in higher ¯D values. No expressive influence of atomic (Ni₃Co) or magnetic order on the interdiffusion has been detected. The activation enthalpyH values were found almost concentration independent. A Kirkendall effect study has been carried out with positive results which are presented in Part II of this paper. A new method for the determination of diffusants concentration in the Kirkendall plane was proposed. With the use of this method and of Darken equations the intrinsic diffusion coefficients were calculated. These results are given in Part III.     

Liquid-vapor interface of square-well fluids of variable interaction range

Properties of the liquid-vapor interface of square-well fluids with ranges of interaction lambda=1.5, 2.0, and 3.0 are obtained by Monte Carlo simulations and from square-gradient theories that combine the Carnahan-Starling equation of state for hard spheres with the second and third virial coefficients. The predicted surface tensions show good agreement with the simulation results for lambda=2 and for lambda=3 in a temperature range reasonably close to the critical point, 0.8相似文献   

A novel MCR of isocyanates, aldehydes, and dienophiles

[reaction: see text] A novel one-pot procedure for the three-component coupling reaction of isocyanates, aldehydes, and dienophiles (IAD reaction) has been developed. Condensation of isocyanates and aldehydes and subsequent Diels-Alder reactions with electron-deficient dienophiles furnishes endo-selective amino-substituted cyclohexenes in good yield.     

Beitrag zur Asphaltanalytik bei Braunkohlenteeren und Hydrierprodukten

Zusammenfassung Das Studium der Fällungsbedingungen für Asphalte aus Teeren und Hydrierprodukten hat zur Entwicklung einer Bestimmungsmethodik mit Vorfällung des Asphaltes durch Erdölschmieröle geführt. Die Verwendung des Schmieröles ermöglicht die Abscheidung der Asphaltstoffe in einer für die nachfolgende Extraktion sehr günstigen, großoberflächigen, pulvrigen Form, wenn man dafür sorgt, daß ein Schmelzen oder Klebrigwerden durch zu hohe Temperaturen beim Fällungsvorgang vermieden wird. Die Dispergierung des zu fällenden Produktes wird durch die gute Lösefähigkeit des Erdölschmieröles für die Nichtasphaltstoffe sehr gefördert und ermöglicht eine gute Verteilung. Auf die Zusammensetzung der Teer- bzw. Entschlammungsasphalte wird näher eingegangen und ihre Bedeutung für die Weiterverarbeitung kurz gestreift.Herrn Professor Dr. A. Kurtenacker zum 70. Geburtstag gewidmet.Herrn Friedrich Ganteför und Fräulein Reiher sei an dieser Stelle für die umfangreiche Mitarbeit bei der praktischen Durchführung der Versuche herzlichst gedankt.     

An SCF study of 10-vertex and 12-vertex boranes and heteroboranes

For symmetry-constrained boranes B₁₀H, B₁₂H, and their valence isoelectronic analogues containing a single hetero atom, completely optimized geometries were obtained using Hartree–Fock SCF calculations with the 3-21G and 6-31G* basis sets. For the anionic and dianionic species, the geometry optimization was also carried out using the 6-31 + G* basis set. Harmonic vibrational frequencies were obtained at HF/3-21G level. The results compare well with experiment where available.     

Synthesis of amino sugars via isoxazolines DL- and D-lividosamine (2-amino-2,3-dideoxy-ribo-hexose) derivatives from 4-vinyl-1,3-dioxolanes and nitroacetaldehyde acetals

1,3-Dipolar cycloaddition of nitrile oxides, generated from nitroethanol and nitroacetaldehyde derivatives 3, 21 and 22, respectively, and of benzonitrile oxide to 4-vinyldioxolanes 1, 2 gave ca 4:1 erythro/threo mixtures of corresponding isoxazolines. LAH reduction of erytho isoxazolines proceeded with similar (ca 4:1) selectivity to furnish protected ribo-amino-polyols 11, 15,19, DL- and D-lividosamines 31 and 33, respectively, as main products. The DL-lividosamine derivative 33 was obtained pure by crystallization. In the D-series, the corresponding ribo/arabino mixture D-31/D-32 was transformed to the known α-methyl D-lividosaminide D-37.     

Synthesis and Characterization of Sterically Encumbered Derivatives of Aluminum Hydrides and Halides: Assessment of Steric Properties of Bulky Terphenyl Ligands

The synthesis and characterization of several sterically encumbered monoterphenyl derivatives of aluminum halides and aluminum hydrides are described. These compounds are [2,6-Mes(2)C(6)H(3)AlH(3)LiOEt(2)](n)() (1), (Mes = 2,4,6-Me(3)C(6)H(2)-), 2,6-Mes(2)C(6)H(3)AlH(2)OEt(2) (2), [2,6-Mes(2)C(6)H(3)AlH(2)](2) (3), 2,6-Mes(2)C(6)H(3)AlCl(2)OEt(2) (4), [2,6-Mes(2)C(6)H(3)AlCl(3)LiOEt(2)](n)() (5), [2,6-Mes(2)C(6)H(3)AlCl(2)](2) (6), TriphAlBr(2)OEt(2) (7), (Triph = 2,4,6-Ph(3)C(6)H(2)-), [2,6-Trip(2)C(6)H(3)AlH(3)LiOEt(2)](2) (8) (Trip = 2,4,6-i-Pr(3)C(6)H(2)-), 2,6-Trip(2)C(6)H(3)AlH(2)OEt(2) (9), [2,6-Trip(2)C(6)H(3)AlH(2)](2) (10), 2,6-Trip(2)C(6)H(3)AlCl(2)OEt(2) (11), and the partially hydrolyzed derivative [2,6-Trip(2)C(6)H(3)Al(Cl)(0.68)(H)(0.32)(&mgr;-OH)](2).2C(6)H(6) (12). The structures of 2, 3a, 4, 6, 7, 9a, 10a, 10b, 11, and 12 were determined by X-ray crystallography. The structures of 3a, 9a, 10a, and 10b, are related to 3, 9, and 10, respectively, by partial occupation of chloride or hydride by hydroxide. The compounds were also characterized by (1)H, (13)C, (7)Li, and (27)Al NMR and IR spectroscopy. The major conclusions from the experimental data are that a single ortho terphenyl substituent of the kind reported here are not as effective as the ligand Mes (Mes = 2,4,6-t-Bu(3)C(6)H(2)-) in preventing further coordination and/or aggregation involving the aluminum centers. In effect, one terphenyl ligand is not as successful as a Mes substituent in masking the metal through agostic and/or steric effects.     

Structure and mechanical properties of poly(l-lactide)/layered silicate nanocomposites

Poly(ε-caprolactone) (PCL) masterbatches with the intercalated and the exfoliated morphology were prepared by ring opening polymerization of ε-caprolactone in the presence of organomodified montmorillonite (MMT) Cloisite 30B. Poly(l-lactide) (PLLA) nanocomposites with Cloisite 30B or PCL masterbatches were prepared by melt blending. The effects of the silicate type, MMT content and the nanocomposite morphology on thermal and mechanical properties of PLLA nanocomposites were examined. The montmorillonite particles in PLLA/Cloisite 30B and PLLA/intercalated masterbatch nanocomposites were intercalated. In contrary to expectations, the exfoliated silicate layers of exfoliated masterbatch were not transferred into the PLLA matrix. Due to a low miscibility of PCL and PLLA, MMT remained in the phase-separated masterbatch domains. The stress-strain characteristics of PLLA nanocomposites, Young modulus E, yield stress σ_y and yield strain ε_y, decreased with increasing MMT concentration, which is associated with the increase in PCL content. The expected stiffening effect of MMT was low due to a low aspect ratio of its particles and was obscured by both plastifying effects of PCL and low PLLA crystallinity. Interestingly, in contrast to the neat PLLA, ductility was enhanced in all PLLA/Cloisite 30B materials and in PLLA/masterbatch nanocomposites with low MMT concentrations.     

Antiferromagnetism of poly(3-dodecylthiophene) irradiated by γ-beams

The magnetic properties of poly(3-dodecyl-thiophene) (PDDT) irradiated by -beams have been studied by measuring the magnetic susceptibility and EPR spectra. The irradiated PDDT is characterized, similarly as the non-irradiated one, by an antiferromagnetic course of magnetic susceptibility with a Néel temperature of 237 K. It is suggested that the antiferromagnetic properties of PDDT are caused by transformation of polarons to bipolarons, which takes place at lower temperatures.     

Axially Dissymmetric Diphosphines in the Biphenyl Series: Synthesis of (6,6′-Dimethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine)(‘MeO-BIPHEP’) and Analogues via an ortho-Lithiation/Iodination Ullmann-Reaction Approach

The new axially dissymmetric diphosphines (R)- and (S)-(6,6′-dimethoxybiphenyl-2,2′-diyl)bis(diphenyl phosphine) ((R)- and (S)- 5a ; ‘MeO-BIPHEP’) and the analogues (R)- and (S)- 5b and 5c have been synthesized in enantiomerically pure form. These ligands have become readily available by a synthetic scheme which employs, as key steps, an ortho-lithiation/iodination reaction of the (m-methoxyphenyl)diprienylphosphine oxides 8 and a subsequent Ullmann reaction of the resulting iodides 9 to provide the racemic bis(phosphine oxides) 10 . The bis(phosphine oxides) 10 subsequently are resolved with (?)-(2R,3R)- and (+)-(2S,3S)-O-2,3-dibenzoyltartaric acid and reduced to diphosphines 5 . The Ullmann reaction constitutes a new and efficient route to 2,2′-bis(phosphinoyl)-substituted biphenyl systems. Absolute configurations were established for (R)- 5a by X-ray analysis of the derived Pd complex (R,R)- 17a , and for 5b and 5c by means of ¹H-NMR comparisons of the derived Pd complexes 16 or 17 , respectively, and by means of CD comparisons. The MeO-BIPHEP diphosphine 5a proved to be as efficient as the previously described BIPHEMP diphosphine ((6,6′-dimethylbiphenyl-2,2′-diyl)bis(diphenylphosphine)) in enantioselective isomerizations and hydrogenations.