Materials Literature
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The isothermal crystallization and melting behavior of the poly(ε-caprolactone)(PCL)/poly(ethylene oxide)(PEO) diblock copolymer has been studied by WAXD, SAXS, and DSC methods. Only the PCL block is crystallizable; the PEO block of weight fraction 20% cannot crystallize, although its corresponding homopolymer has str…
Ab initio molecular-dynamics simulations have been used to investigate the structure, dynamics and electronic properties of the liquid alloy Ag(1-x)Se(x) at 1350 K and at the three compositions x=0.33, 0.42 and 0.65. The calculations are based on density-functional theory in the local density approximation and on the…
Reactions of (silylamino)silanetriols RN(SiMe 3 )Si(OH) 3 (R = 2,4,6-Me 3 C 6 H 2 ( 1 ) and 2,6-Me 2 C 6 H 3 ( 2 )) with i -Bu 2 AlH in 1:1 molar ratio at −78 °C afford aluminosiloxanes [RN(SiMe 3 )Si(OH)O(OAlBu- i ·dioxane)] 2 (R = 2,4,6-Me 3 C 6 H 2 ( 3 ) and 2,6-Me 2 C 6 H 3 ( 4 )) and [RN(SiMe 3 )Si(OAlBu- i )(OAl…
Diffusion in homogenous membranes molecular simulations of sorption and diffusion in amorphous polymers free-volume theory transport phenomena in polymer membranes supermolecular structure of polymer solids and its effects on penetrant transport translational dynamics of macromolecules in melts.
In order to access the dynamics of surface diffusion or of surface chemical reactions it is necessary to determine the spatial probability distributions of the adsorbed atoms or molecules rather than their average positions. Here we demonstrate how such a distribution can be determined from scanned-energy mode photoel…
Zwei gegabelte Wasserstoffbrückenbindungen legen die Vorzugskonformation I des unten gezeigten Catenans im Festkörper und in unpolaren Lösungsmitteln fest; in polaren Lösungsmitteln ist Konformation II die dominierende. magnified image
The microstructure of (001)p-oriented (subscript p indicates the choice of a pseudocubic unit cell) potassium niobate (KNbO3) thin films grown by metalorganic chemical vapor deposition on (100)p lanthanum aluminate and having a large second-order nonlinear optical response is examined. Transmission electron microscopy…
An efficient, electrically conductive, chemical barrier for the integration of piezoelectric Pb(Zr,Ti)O3 (PZT) films on reactive metal substrates has been developed, opening new possibilities for PZT integration on micromechanical and semiconductor devices. Very reactive zirconium films have been taken in order to tes…
The disorder-to-order transition in asymmetric diblock copolymers of polystyrene/polyisoprene is studied using small angle x-ray scattering. In between the homogeneously disordered state at high temperature and the bcc ordered array of spheres we find a stable state of liquidlike order between the spherical domains. Q…
Si ions were implanted into thermally grown SiO2 films on crystalline Si at an energy of 120 keV and with a dose of 1016 cm−2. Under an ultraviolet excitation of ∼5.0 eV, the implanted films exhibit blue luminescence with a peak of ∼2.7 eV at room temperature. The blue emission is caused by oxygen vacancies in the fil…
The electronic structures of the perovskite oxides, ${\mathrm{LaMnO}}_{3}$ and ${\mathrm{CaMnO}}_{3}$, are studied using density-functional methods. Antiferromagnetic insulating (AFI) solutions are obtained for both compounds within the local-density approximation (LDA). For ${\mathrm{LaMnO}}_{3}$ the Jahn-Teller dist…
Polycrystalline diamond films have been grown by microwave assisted chemical vapor deposition from methane/hydrogen gas mixtures. The addition of small amounts of nitrogen with concentrations below 50 ppm to the process gas was found to drastically increase the deposition rate depending on the microwave power. At 4.2…
The hardness, elastic modulus, and structure of several amorphous carbon films on silicon prepared by cathodic-arc deposition with substrate pulse biasing have been examined using nanoindentation, energy loss spectroscopy (EELS), and cross-sectional transmission electron microscopy. EELS analysis shows that the highes…
Introduction of pentagon-heptagon pair defects into the hexagonal network of a single carbon nanotube can change the helicity of the tube and alter its electronic structure. Using a tight-binding method to calculate the electronic structure of such systems we show that they behave as nanoscale metal/semiconductor or s…
For the directed synthesis of polyoxometalates the linking of the heteropolyanion 1 (schematic representation shown on the right) to form the dimeric anion 2 is extremely significant. The formation of the corresponding potassium salts of 1 and 2 from K2MoO4 and As2O3 is controlled merely by the pH value of the solutio…
Direct oxygen transfer to an olefinic bond is possible from the FeIII complex 2 if the double bond is electron-deficient as in 1 [Eq. (a)]. Complex 2 is analogous to intermediates proposed for cytochrome P450 type enzymes.
Ninety chiral centers and a molecular mass of 11354 Da are the outstanding features of the largest C 3 ‐symmetric, chiral dendrimer to date. As general approach to these chiral polyether compounds (1) styrenes or stilbenes are converted into 1,2‐diols by asymmetric dihydroxylation; (2) the resulting building blocks ar…
Two dianionic caps, linked by four lithium atoms, characterize the structure of the Li salt 1 of the tripodal ligand [S(NtBu)3]2−. On addition of THF to 1 one lithium atom leaves the inner region and coordinates to only two N atoms and a THF molecule. Oxidation of white 1 with O2 or iodine leads to a dark blue, stable…
High activity and negligible coke formation in the course of the catalytic partial oxidation of CH 4 to syngas are characteristics of the Ni/Ca 4‐ x Sr x TiO 3 catalyst, which is readily accessible by the citrate method from nickel nitrate, alkaline earth metal carbonates, and tetraisopropoxidotitanium. The properties…
Abstract Single crystals of (I) CuDyMo 2 O 8 and (II) CuYbMo 2 O 8 have been prepared by crystallisation from melts. Both com pounds crystallize with orthorhombic symmetry, space group D 15 2h -Pbca with (I): a = 10.195(1), b = 9.721(2), c = 14.563(3); (II): a = 10.094(6), b = 9.628(9), c = 14.467(8) Å, Z = 8. The cr…