Materials Literature
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Shape memory thermoplastic polyurethanes (TPUs), based on amorphous soft segment from the reaction of hexamethylene diisocyanate and 1,2-butane diol, and the crystalline hard segment from 4,4′-methylenediphenyl diisocyanate and 1,6-hexanediol, were modified by hydrophilic segments, diol-terminated poly(ethylene oxide)…
Using the embedded-atom method, the structure of small copper clusters on Au(111) electrodes has been investigated both by static and dynamic calculations. By varying the size of roughly circular clusters, the edge energy per atom is obtained; it agrees quite well with estimates based on experimental results. Small th…
Crack-free antiferroelectric PbZrO3(PZ) thin films were prepared by a two-step annealing technique via a modified sol-gel process. Although x-ray diffraction results showed that single phase of perovskite PbZrO3 was obtained in the thin films annealed at 550, 700, and 550 °C/700 °C, double P-E hysteresis loop indicati…
Weit reichende Wechselwirkungen findet man bei einer neutralen, schichtartig aufgebauten Kupferverbindung, bei der die CuII-Ionen abwechselnd über End-on- und End-to-End-ständige Azide verbrückt sind (siehe Bild). Magnetische Messungen deuten auf ungewöhnliche ferromagnetische Wechselwirkungen zwischen den CuII-Ionen…
Die katalysierte Epoxidierung und Hydroxylierung von Kohlenwasserstoffen durch 30proz. H2O2 sowie die Bildung von Oxoeisen(IV)-Porphyrin-Intermediaten mit m-Chlorperbenzoesäure (m-CPBA) wird durch den anionischen axialen Ligandeneffekt des elektronenarmen Eisen(III)-Porphyrinkomplexes [Fe(tpfpp)X] markant beeinflusst…
Mindestens einige Tage beständig ist der lichtinduzierte metastabile High-Spin-Zustand eines Stark-Feld-FeII-Komplexes bei ≥20 K (siehe Schema). Die Lebensdauer dieses Zustands ist damit mehr als acht Größenordnungen länger als nach der Theorie des Inverse-Energy-Gap-Law erwartet.
Dreidimensionale Kanäle durchziehen ein Netz aus {[Dy4(OH)4(asp)3(H2O)8](ClO4)2⋅10 H2O}-Clustern (siehe Bild). Die Synthese gelang aus Dy(ClO4)3 und L-Asparaginsäure in wässriger Lösung bei pH 6.5. Diese Verbindung mit offener Gerüststruktur ist ein Beispiel für die Anordnung diskreter Lanthanoidcubane zu einem Superc…
This letter investigates the role of postdeposition oxygen treatments upon their luminescent properties by synthesizing Eu:Y2O3 films by pulsed laser deposition under different conditions and subjecting them to various postdeposition oxygen treatments. Our results have shown that Eu:Y2O3 films grown in 300 mTorr oxyge…
Rodlike amphiphilic molecules that contain exclusively aromatic building-blocks and no flexible alkyl chains have been synthesized and their mesomorphic properties investigated. These novel compounds bear diol head groups of different size (2,3-dihydroxypropyloxy or 5,6-dihydroxy-3-oxahexyloxy groups) at one end of a…
A microcavity composed of porous silicon multilayer mirrors was electrochemically etched and doped with erbium. Measurements of the reflectivity and photoluminescence spectra are presented. Thermal processing under a nitrogen atmosphere optically activated the erbium ions. Photopumping yielded room temperature emissio…
A butterfly structure and competing magnetic exchange interactions between the manganese(II) ions and organic, ruthenocene-substituted α-nitronyl nitroxide (NIT) radicals characterize the spin frustration system of a new dimeric MnII complex (see scheme, IMH=reduced form of the imino nitroxide).
A series of transition metal substituted polyfluorooxometalates (PFOM) [M(L)H2F6NaW17)55]q-, M= Zn2+ , Co2+, Mn2+, Fc2+, Ru2+, Ni2+ and V5+ and L=H2O, O2-, of quasi-Wells-Dawson structure, was synthesized. In the series prepared, only the nickel-substituted polyfluorooxometalate was capable of catalytic activation of…
That guest atoms donate electrons to framework atoms is a generally accepted concept. Nevertheless, evidence for the presence of neutral guest atoms in thermoelectric clathrate structures is presented in the form of experimental X-ray charge density analysis and X-ray absorption near-edge structure (XANES) data. The p…
Bei der Katalyse durch Dendrimere induzieren die katalysierenden Einheiten aufgrund ihrer räumlichen Nähe nützliche kooperative Effekte (siehe Bild). Kommerziell erhältliche Dendrimere wurden mit chiralen [Co(salen)]-Komplexen derivatisiert und wiesen bei der hydrolytischen kinetischen Enantiomerentrennung eine höhere…
We have heteroepitaxially deposited Ba0.6Sr0.4TiO3 (BST) thin films on (001)-oriented MgO substrates using pulsed-laser deposition. By optimizing the deposition temperature and adjusting the film thickness, we have successfully increased the dielectric nonlinearity and decreased the dielectric loss of BST films. BST t…
The Wiedemann–Franz law for electron transport in metals was historically a linch pin for the free-electron theory of metals; it states that, at moderately low temperatures, the ratio of thermal conductivity K to electrical conductivity σ is proportional to absolute temperature, with a proportionality constant called…
Abstract Carbonate and sulphate scales are the most common types of mineral deposit associated with the recovery and processing of hydrocarbon and associated produced water. In three high temperature fields (>140C) within the North Sea more usual scale types have been observed namely zinc and lead sulphide. Con…
Electron density distributions were obtained using the maximum entropy method with synchrotron radiation powder data. In the metallic Al12Re, metallic bonding was observed for the icosahedral Al12 cluster with central Re atom. In the nonmetallic alpha-AlMnSi 1/1 approximant, covalent bonds were found in the electron d…
We report the first solid state X-ray crystal structure for a Eu(II) chelate, [C(NH2)3]3[Eu(II)(DTPA)(H2O)].8H2O, in comparison with those for the corresponding Sr analogue, [C(NH2)3]3[Sr(DTPA)(H2O).8H2O and for [Sr(ODDA)].8H2O (DTPA5 = diethylenetriamine-N,N,N',N",N"-pentaacetate, ODDA2- =1,4,10,13-tetraoxa-7,16-diaz…
A marked influence on the catalytic epoxidation and hydroxylation of hydrocarbons by aqueous 30 % H2O2 in an aprotic solvent and on the formation of oxoiron(IV) porphyrin intermediates in m-chloroperoxybenzoic acid (m-CPBA) reactions in polar solvent is shown by the anionic axial ligands of an electron-deficient iron(…