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  • Polymer and Materials Science  (3)
  • crystal structure  (3)
  • Wiley-Blackwell  (6)
  • 1
    Digitale Medien
    Digitale Medien
    Mechanical relaxations and diffusive changes in linear low density polyethylene (LLDPE) films subject to induced stretching (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 767-778 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: An analysis of the diffusion of oxygen and carbon dioxide through linear low density polyethylene (LLDPE) subjected to longitudinal and transversal induced stretching in the ratio 2:1, is presented in this paper. The relaxation behavior of two coextruded LLDPE films prepared from copolymers of ethylene-1-octene is reported as well. The spectra, expressed in terms of loss tan δ, present a γ relaxation shifted 5°C to 10°C in the LLDPE1 with respect to the LLDPE2 when the stretching was longitudinal. This relaxation is lower in intensity than the one exhibited for conventional low-density polyethylene of the same crystallinity. Increasing the temperature order, a β relaxation process appears as an ostensible shoulder of the first of two relaxation processes, called α′ and α″, detected in the α region. The β relaxation, which is believed to be produced by motion taking place in the amorphous and interfacial regions, appears as two overlapping peaks centered at -36°C and -30°C for a longitudinal stretching and at -34°C and -28°C for a transversal stretching at 1 Hz. In relation to this fact, we observed a slight increase in the Tα of the LLDPE2 with respect to the LLDPE1, which is greater in the transversally stretched polymers than in the longitudinal ones. The values of the activation energy corresponding to the second peak of the β relaxation were obtained for the films subjected to stretching in longitudinal and transversal directions to the processing orientation. The study of the diffusional characteristics of oxygen and carbon dioxide through the films shows the temperature is related to the region for which the α processes are given. An anomalous behavior of the diffusion coefficient with the temperature is observed, suggesting general movements around the amorphous segments and crystalline entities. The increase with the temperature of both parameters (diffusion and permeability) can be attributed to a change in the gas solubility. This increase is greater for CO2 than for O2 which we interpret as a plastificant effect of the CO2. Finally, the activation energies from diffusion coefficent and permeability are analyzed in terms of Arrhenius. The results show that the temperature dependence of the diffusive parameters may not be a simply activated process as a consequence of the fact that the diffusional characteristics of the films depend on their morphology which, in turn, is changing with temperature. Little changes are observed when the films are subjected to any kind of stretching. In this sense, we think that the orientation by tensile drawing will decrease the conformational entropy involved in melting processes and, as a consequence, will reduce both the permeability and the apparent diffusion coefficients. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Comparative study of the corrosion behavior of MA-956 and conventional metallic biomaterials (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 31 (1996), S. 313-317 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: In this work the corrosion behavior of a new biomaterial, the MA-956 superalloy, immersed in Hank's solution is evaluated. A comparison with conventional metallic alloys used as articular implants is established. To determine the corrosion behavior we employed electrochemical methods: evaluation of corrosion potential Ecorr, electrochemical impedance spectroscopy (EIS), and anodic polarization curves. The corrosion resistance of the MA-956 superalloy preoxidized at 1100°C during 100 h is at least two orders of magnitude higher than for the other alloys. This satisfactory behavior is stationary with time. Also the probability of the appearance of the pitting corrosion process is very low. When cracking is generated in the α-alumina layer the repassivation process is assured because of the high Cr content in the superalloy. This study is the first step in proposing this new alloy as a biomaterial. The low toxicity of these metallic alloys in the physiological environment suggests that in vivo their biocompatibility could be satisfactory. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Thermal and dielectric behaviors of poly(vinylidene fluoride-trifluoroethylene) copolymers at the curie transition (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 27 (1989), S. 709-722 
    Details
    ISSN: 0887-6266
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The thermal and dielectric behaviors of poly(vinylidene fluoride-trifluoroethylene) copolymers near the ferroelectric-to-paraelectric phase transition are investigated for samples with 20, 25, 30, and 40 mol% trifluoroethylene (TrFE). The data suggest that the transition becomes continuous for a particular composition near 50 mol% TrFE. Experimental data are sensitive to thermal history (kinetics of crystallization, and kinetics and cycling over the structural transition). It is found that several anomalies are present at the structural change, and in particular the 30 mol% TrFE sample shows the most marked anomalies. These phenomena can be attributed to defects, but another possibility would be the existence of an intemediate supplementary phase. Both hypotheses are discussed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/polb.1989.090270315
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Ba7Fe6F32 · 2H2O: Original isolated trimers [Fe3F16]7- in a new defective jarlite-type compound (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 1025-1032 
    Details
    ISSN: 0044-2313
    Schlagwort(e): Barium iron fluoride ; crystal structure ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Ba7Fe6F32 · 2H2O: isolierte [Fe3F16]7--Trimere in einer neuen Verbindung vom Defekt-Jarlit-TypBa7Fe6F32 · 2H2O wurde aus wäßriger HF-Lösung in einer Teflon-Bombe (Berghof) bei 180°C dargestellt. Ein teilweiser F-/OH--Austausch erfolgt in verdünnterem HF-Medium und führt zu Ba7Fe6F32-x(OH)x · 2H2O. Die Verbindungen kristallisieren im monoklinen System, Raumgruppe C2/m (Z = 2) mit a = 17,023(1) Å, b = 11,482(1) Å, c = 7,624(1) Å, β = 101,13(1)° für x = 0 und a = 17,036(2) Å, b = 11,489(1) Å, c = 7,620(2) Å, β = 101,48(1)° für x ≍ 5,3. Die Struktur wurde aus 2 256 bzw. 1 343 unabhängigen Reflexen für x = 0 bzw. x ≍ 5,3 mit einem Siemens AED2 Vierkreisdiffraktometer (MoKα) bestimmt; für x = 0: R = 0,0235, Rw = 0,0240; für x ≍ 5,3: R = 0,0324, Rw = 0,0335. Die eng mit dem Jarlit-Typ verwandte Struktur wird aus isolierten Oktaedertrimeren [Fe3F16]7- aufgebaut, die durch Ba2+-Ionen verknüpft werden. Die Lage der Anionen und Wassermoleküle wird mittels Valenzband-Rechnungen diskutiert. Magnetische-und Mössbauer-Untersuchungen werden diskutiert.
    Notizen: Ba7Fe6F32 · 2H2O was prepared from HF aqueous solution in a teflon bomb (Berghof) at 180°C. A partial exchange F-/OH- can be realized in more diluted HF medium and leads to Ba7Fe6F32-x(OH)x · 2H2O. The compounds crystallize in the monoclinic system, space group C2/m (Z = 2) with a = 17.023(1) Å, b = 11.482(1) Å, c = 7.624(1) Å, β = 101.13(1)° for x = 0 and a = 17.036(2) Å, b = 11.489(1) Å, c = 7.620(2) Å, β = 101.48(1)° for x ≍ 5.3. The structures were determined from 2 256 and 1 343 independent reflections for x = 0 and x ≍ 5.3 respectively, collected with a Siemens AED2 four-circle diffractometer with the MoKα radiation (R = 0.0235 and Rw = 0.0240 for x = 0 and R = 0.0324 and Rw = 0.0335 for x ≍ 5.3). The structure, closely related to that of the Jarlite-type, is built up from isolated octahedra trimers [Fe3F16]7-, connected together by Ba2+-cations. The location of anions and water molecules is discussed from bond valence calculations. Magnetic and Mössbauer studies are reported and discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/zaac.19956210622
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Crystal Structure of a New Acentric Oxide Fluoride of VIV: BaVOF4 (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 309-312 
    Details
    ISSN: 0044-2313
    Schlagwort(e): Barium vanadium oxide fluoride ; synthesis ; crystal structure ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Kristallstruktur eines neuen azentrischen Oxidfluorids des VIV: BaVOF4Die Struktur von BaVOF4, erhalten durch hydrothermale Synthese, wurde röntgendiffraktometrisch aus Einkristalldaten bestimmt: Raumgruppe Fdd2 (azentrisch), Z = 16, a = 7,920(1), b = 27,608(2), c = 7,375(1) Å mit R = 0,0262, Rw = 0,0273 für 1 508 unabhängige Reflexe und 64 Parameter. Das Gitter wird von cis-verknüpften VOF5-Oktaedern aus gewinkelten unendlichen Ketten entlang [101] und [101] gebildet, die über Barium-Kationen verbunden sind. Die Lage der O2- und F- wird mittels Valenzband-Rechnungen diskutiert. Wie für BaTiOF4 und einige Verbindungen aus der Reihe AIIMIIIF5 (A = Ba, Sr und M = Ga, Al, Mn) kann die Struktur durch quasi-hexagonal dichteste Ebenen aus Stapeln von Ba2+, O2-- und F--Ionen beschrieben werden.
    Notizen: The structure of BaVOF4 has been determined by X-ray diffraction data from a single crystal obtained by hydrothermal synthesis: S.G. Fdd2 (acentric), Z = 16, a = 7.920(1), b = 27.608(2) and c = 7.375(1) Å with R = 0.0262 and Rw = 0.0273 for 1 508 independent reflections and 64 parameters. The network is built up from cis-linked VOF5 octahedra forming infinite kinked chains running along the [101] and [101] directions, connected by barium cations. The location of O2- and F- ions is discussed using bond valence calculations. As for BaTiOF4 and some compounds in the series AIIMIIIF5 (A = Ba, Sr and M = Ga, Al, Mn), the structure can be described in terms of a quasi hexagonal compact planes stacking of Ba2+, O2- and F- ions.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/zaac.19946200216
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Synthesis and Crystal Structure of Ba4Mo2O5F7(HF2)3 · H2O (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 439-443 
    Details
    ISSN: 0044-2313
    Schlagwort(e): Barium ; molybdenum oxyfluoride ; crystal structure ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Synthese und Kristallstruktur von Ba4Mo2O5F7(HF2)3 · H2OEinkristalle von Ba4Mo2O5F7(HF2)3 · H2O wurden durch hydrothermale Synthese erhalten. Die Röntgenstrukturbestimmung ergab: Raumgruppe Pnnm, Z = 4, a = 16,497(1), b = 8,6939(5), c = 11,5174(6) Å (R = 0,0295, Rw = 0,0354 für 2425 unabhängige Reflexe und 126 Parameter). Mo ist im MoO3F3 verzerrt oktaedrisch umgeben. Zwei Oktaeder bilden, übereck verbunden durch O2-, (Mo2O5F6)4--Einheiten entlang der c-Achse. Die Ba-Atome liegen in zwei unterschiedlichen Umgebungen vor: einem quasi dreifach bekappten Kubus für Ba1 und Ba3 und einem dreifach bekappten trigonalen Prisma für Ba2.
    Notizen: Single crystals of Ba4Mo2O5F7(HF2)3 · H2O are grown by hydrothermal synthesis. The structure is determined from X-Ray diffraction data: space group Pnnm, Z = 4, a = 16.497(1) Å, b = 8.6939(5) Å, c = 11.5174(6) Å (R = 0.0295, Rw = 0.0354 for 2425 independent reflections and 126 adjustable parameters). Mo atoms are in a distorted octahedral environment MoO3F3; two octahedra are linked by one O2- corner forming (Mo2O5F6)4- units lying along the c axis. Ba atoms present two kinds of environment: a quasi tricapped cube for Ba1 and Ba3 and a tricapped tricapped trigonal prism for Ba2.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/zaac.19976230170
    Standort Signatur Erwartet Verfügbarkeit
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