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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 28 (1982), S. 900-907 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During their industrial processing, polymer liquids are usually subjected to complex flow histories. In principle, these can be taken into account in the constitutive equations. In reality, difficulties arise for complex flows. This fact can be illustrated by the spinning process. Here, experiments are presented in which the upstream section of a spinning device has been changed systematically. A constitutive model and a calculation procedure are suggested that permit an analysis of the upstream effects in the spinning flow. The results indicate that this analysis predicts well the spinning dynamics in the present experiments, using shear flow characteristics for the liquids. It is also concluded that the spinning flow can be altered by upstream changes. The changes in structure seem to be the most pronounced ones.
    Additional Material: 10 Ill.
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  • 2
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 23 (1977), S. 224-232 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An efficient and simple numerical technique is presented for analyzing nonisothermal nip flow of viscous liquids. It has been applied on calendering to calculate the design parameters as well as the interaction effects between roller characteristics, operation conditions, and material properties. Viscous heating is shown to drastically change the mechanics near the nip exit if the rollers rotate at different speeds. Consequences for scaling-up and model experiments are indicated.
    Additional Material: 7 Ill.
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  • 4
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The non-Newtonian viscosities of polymerically stabilized colloidal suspensions are usually predicted and correlated on the basis of data and scaling principles for Brownian hard spheres. Here, the specific effect of the stabilizer layer is investigated using suspensions of monodisperse PMMA particles with a chemically attached stabilizer layer. The ratio between particle radius and stabilizer layer thickness is changed between 5 and 61. At high values of this ratio the data show Brownian hard sphere behavior. At lower values deviations appear. As a first approximation, the “softness” of the particles can be characterized through the concentration at maximum packing. A more detailed comparison with hard sphere data provides a measure for softness that changes with concentration and shear rate. A theoretical estimate of the concentration effect is in line with the experiments. The critical shear stress (or Peclet number) is not a constant but goes through a maximum when the concentration is increased.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 545 (1987), S. 43-46 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Rutile-Type Structure with Chains of Tetrahedra: The Compound CaCu4P2CaCu4P2 was prepared by heating the elements (slight excess of Cu, 850-950°C) and investigated by single crystal X-ray methods. The compound crystallizes tetragonally in a rutile-type structure (P42/mnm, a = 729.0(2) pm, c = 383.1(1) pm) built up by Ca and P atoms in which Cu atoms occupy the vacancies in form of chains of edge-shared tetrahedra.
    Notes: CaCu4P2 wurde aus den Elementen dargestellt (geringer Cu-Überschuß, 850-950°C) und röntgenographisch mit Einkristallmethoden untersucht. Die Verbindung kristallisiert tetragonal (P42/mnm, a = 729, 0(2) pm, c = 383, 1(1) pm) in einer von Ca- und P-Atomen aufgebauten Rutilstruktur, bei welcher Cu-Atome in Form kantenverknüpfter Tetraederketten die noch freien Plätze besetzen.
    Additional Material: 1 Ill.
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  • 6
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 561-565 
    ISSN: 0044-2313
    Keywords: Ternary palladium phosphide ; erbium ; crystal structure ; band calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Er3Pd7P4  -  Crystal Structure Determination and Extended Hückel CalculationsEr3Pd7P4 was prepared by heating the elements (1050°C) and investigated by means of single-crystal X-ray methods. The compound crystallizes in a new structure (C2/m; a = 15.180(3) Å, b = 3.955(1) Å, c = 9.320(1) Å, β = 125,65(1)°; Z = 2) with a three-dimensional framework of Pd and P atoms and with Er atoms in the holes. The Pd atoms are surrounded tetrahedrally, trigonally or linearly by P atoms, which are coordinated by nine metal atoms in the form of a tricapped trigonal prism. Therefore the atomic arrangement of Er3Pd7P4 is related to the structures of ternary transition metal phosphides with a metal: phosphorus ratio of 2:1. Band calculations using the Extended Hückel method show strong covalent Pd—P bonds and weak bonding interactions between Pd atoms with Pd—Pd distances shorter than 2.9 Å.
    Notes: Er3Pd7P4 wurde durch Erhitzen der Elemente auf 1050°C dargestellt und röntgenographisch mit Einkristallmethoden untersucht. Die Verbindung kristallisiert monoklin (C2/m; a = 15,180(3) Å, b = 3,955(1) Å, c = 9,320(1) Å, β = 125,65(1)°; Z = 2) in einer neuen Struktur mit einem dreidimensionalen Gerüst aus Pd- und P-Atomen, in dessen Lücken sich die Er-Atome befinden. Die P-Umgebung der Pd-Atome ist tetraedrisch, trigonal oder linear. Die P-Atome ihrerseits werden von 9 Metallatomen in Form eines dreifach überkappten trigonalen Prismas koordiniert. Der Aufbau von Er3Pd7P4 ist dementsprechend verwandt mit den Strukturen ternärer Übergangsmetall-Phosphide mit einem Metall: Nichtmetallverhältnis von 2:1. Extended Hückel Rechnungen zeigen u. a. neben starken kovalenten Pd—P-Bindungen schwache bindende Wechselwirkungen zwischen denjenigen Pd-Atomen, deren Abstände voneinander kürzer als 2,9 Å sind.
    Additional Material: 5 Ill.
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  • 8
    ISSN: 0044-2313
    Keywords: ternary aluminium germanides ; yttrium ; rare earth ; crystal structure ; band calculations ; electron localization ; superconductivity ; zintl-compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Y2AlGe3 - a Superconductive Metallic Zintl CompoundY2AlGe3 was prepared by heating the elements (950°C) and investigated by means of single-crystal X-ray methods. The compound crystallizes in a new structure (Pnma; a = 6.785(1) Å, b = 4.189(1) Å, c = 17.676(2) Å; Z = 4) with a three-dimensional framework of Al and Ge atoms and with Y in the cavities. The Al atoms are surrounded tetrahedrally by Ge atoms, which are arranged in the form of planar (Ge2-)∞ chains and isolated from each other respectively. Although Y2AlGe3 is a metallic conductor and no valence compound, it achieves the structural requirements of Zintl's concept. This picture is supported by electrondensity and ELF calculations, which reveals covalent Al—Ge and Ge—Ge bondings, therefore Y2AlGe3 is interpreted as a metallic Zintl-Compound, down-playing the metallic propertys. Y2AlGe3 becomes superconductively at 4.5 K. Isotypic compounds are found for Ln2AlGe3 with Ln = Dy, Ho, Er, and Tm (For lattice constants see “Inhaltsübersicht”).
    Notes: Y2AlGe3 wurde durch Erhitzen der Elemente auf 950°C dargestellt und röntgenographisch mit Einkristallmethoden untersucht. Die Verbindung kristallisiert in einer neuen Struktur (Pnma; a = 6,785(1) Å, b = 4,189(1) Å, c = 17,676(2) Å; Z = 4) mit einem dreidimensionalen Gerüst aus Al- und Ge-Atomen, in dessen Lücken sich die Y-Atome befinden. Al ist tetraedrisch von Ge-Atomen umgeben, die ihrerseits ebene (Ge2-)∞-Ketten bilden bzw. voneinander isoliert vorliegen. Trotz nicht valenzmäßiger Zusammensetzung gemäß Y3+ Y3+ Al3+ (Ge2)4- Ge4- und metallischer Leitfähigkeit weist Y2AlGe3 die Strukturmerkmale einer Zintl-Verbindung auf. Diese Interpretation wird gestützt durch Berechnungen der Elektronendichte und Elektronenlokalisierungsfunktion (ELF), die kovalente Ge—Ge- und Al—Ge-Bindungen zeigen. Die Verbindung wird demnach als metallische Zintl-Verbindung angesehen. Y2AlGe3 wird bei 4,5 K supraleitend. Isotyp kristallisieren die Verbindungen Ln2AlGe3 (Ln = Dy—Tm) mit den Gitterkonstanten: Dy2AlGe3: a = 6,785(3) Å, b = 4,171(1) Å, c = 17,665(7) Å Ho2AlGe3: a = 6,753(2) Å, b = 4,158(1) Å, c = 17,580(4) Å Er2AlGe3: a = 6,732(1) Å, b = 4,147(3) Å, c = 17,517(3) Å Tm2AlGe3: a = 6,706(3) Å, b = 4,061(5) Å, c = 17,550(9) Å.
    Additional Material: 3 Ill.
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  • 9
    ISSN: 0044-2313
    Keywords: Ternary cadmium pnictides ; europium ; ytterbium ; crystal structure ; magnetism ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: AM2X2 Compounds with the CaAl2Si2-Type Structure. XI. Structure and Properties of ACd2X2 (A: Eu, Yb; X: P, As, Sb)EuCd2P2, EuCd2As2, EuCd2Sb2, YbCd2As2, and YbCd2Sb2 were prepared by heating mixtures of the elements and investigated by means of single-crystal X-ray methods. The compounds are isotypic (lattice constants see “Inhaltsübersicht”) and crystallize in the CaAl2Si2-type structure (P3m1; Z = 1). Magnetic measurements showed, that Eu is divalent and that the compounds order magnetically at low temperatures.
    Notes: Durch Erhitzen entsprechender Elementgemenge wurden EuCd2P2 (a = 4,325(1) Å, c = 7,179(1) Å), EuCd2As2 (a = 4,439(1) Å, c = 7,328(1) Å), EuCd2Sb2 (a = 4,698(1) Å, c = 7,723(1) Å), YbCd2As2 (a = 4,388(1) Å, c = 7,149(2) Å) und YbCd2Sb2 (a = 4,650(1) Å, c = 7,565(2) Å) dargestellt und röntgenographisch mit Einkristallmethoden untersucht. Die Verbindungen sind isotyp und kristallisieren im CaAl2Si2-Strukturtyp (P3m1; Z = 1). Eu ist in den betreffenden Verbindungen zweiwertig, die Substanzen ordnen bei tiefen Temperaturen magnetisch.
    Additional Material: 4 Ill.
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  • 10
    ISSN: 0044-2313
    Keywords: Ternary nickel phosphides ; strontium ; barium ; crystal structure ; phase transition ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: About Polymorphism of SrNi2P2 and Crystal Structure of BaNi2P2SrNi2P2 and BaNi2P2 were prepared by heating mixtures of the elements and investigated by single crystal X-ray methods. The Sr compound at room temperature crystallizes in a superstructure of the ThCr2Si2 type (NT-phase; Immm; Z = 6; a = 3.951(2), b = 11.853(2), c = 10.432(2) Å), which is caused by displacements of the atoms from the ideal positions; the P—P distances are 2.45 and 3.28 Å. With increasing temperature at 45°C (ambient pressure) and increasing pressure at 4 kbar (room temperature) respectively the compound undergoes first order phase transitions and crystallizes after that in the undistorted ThCr2Si2 type (I4/mmm; Z = 2). While the P atoms of the high temperature phase (HT-SrNi2P2: a = 3.948(1), c = 10.677(3) Å; 100°C) are isolated from each other (dp p: 3.12 Å) they most probably form pairs in the high pressure phase (HD-SrNi2P2: a = 4.003(1), c = 9.761(2) Å; ca. 4 kbar). This will be discussed on the basis of band structure calculations. BaNi2P2 (a = 3.947(1), c = 11.820(1) Å) also crystallizes in the ThCr2Si2 type structure, the P—P distance is extended to 3.71 Å.
    Notes: SrNi2P2 und BaNi2P2 wurden durch Erhitzen entsprechender Elementgemenge dargestellt und röntgenographisch mit Einkristallmethoden untersucht. Die Sr-Verbindung kristallisiert bei Normaltemperatur in einer Überstruktur des ThCr2Si2-Typs (NT-SrNi2P2: Immm; Z = 6; a = 3,951(2), b = 11,853(2), c = 10,432(2) Å), die durch Auslenkung der Atome aus den idealen Positionen verursacht wird. Die P—P-Abstände längs [001] betragen 2,45 und 3,28 Å. Die Verbindung durchläuft mit steigender Temperatur bei 45°C (Normaldruck) sowie mit zunehmendem Druck bei ca. 4 kbar (Normaltemperatur) jeweils eine Phasenumwandlung 1. Ordnung und kristallisiert dann im unverzerrten ThCr2Si2-Strukturtyp (I4/mmm; Z = 2). Während bei der Hochtemperaturphase (HT-SrNi2P2: a = 3,948(1), c = 10,677(3) Å; 100°C) der P—P-Abstand längs [001] 3,12 Å beträgt, liegt er bei der Hochdruckphase (HD-SrNi2P2: a = 4,003(1), c = 9,761(2) Å; ca. 4 kbar) dem c/a-Verhältnis zufolge vermutlich bei 2,45 Å. Die Gründe für die Phasenumwandlungen werden an Hand der elektronischen Struktur diskutiert, BaNi2P2 (a = 3,947(1), c = 11,820(1) Å) kristallisiert ebenfalls im ThCr2Si2-Typ, der P—P-Abstand längs [001] ist hier auf 3,71 Å aufgeweitet.
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