Materials Literature
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Molecular structure, morphological characteristics and electrical conduction in syndiotactic polypropylene (sPP) are studied. sPP is found to be highly resistant to thermal oxidation. The crystallinity measured by the x-ray diffraction meter is very low and shows no significant change with annealing, compared with tha…
Irreversible adsorption/deposition processes are defined as processes in which, once adsorbed, the particles can neither desorb from nor diffuse along the surface. These processes are commonly encountered when macromolecules or colloidal particles deposit on solid surfaces. This article presents a general and unified…
Our recent study on the incorporation of Sn in the lattice of MgAl-layered double hydroxides (LDHs) indicated that about 30 atom % of Al 3+ could be isomorphously substituted by Sn 4+ to form a new MgAlSn ternary LDH. In the present study, similar NiAlSn- and CoAlSn-LDHs were synthesized by a coprecipitation method. T…
We studied the dynamics of spontaneously spreading drops of viscous liquids over several decades of time. We show that there exist at least two different time scale behaviors which are compatible with the recently proposed combined theory of spreading dynamics.
Novel bent-core (banana-shaped) liquid crystals without Schiff-base units have been synthesized and investigated by polarized light optical microscopy, differential scanning calorimetry, X-ray scattering, and electrooptical investigations. These molecules are 4-(4-alkylbenzoyloxy)benzoates and 4-(4-alkoxybenzoyloxy)be…
We have combined the original diffusion-limited aggregation model introduced by Witten and Sander with the surface thermodynamics of the growing solid aggregate. The theory is based on the consideration of the surface chemical potential as a thermodynamic function of the temperature and nearest-neighbor configuration.…
The coupling between the superconducting planes of YBa2Cu3O{7-δ}/ PrBa2Cu3O{7-δ} superlattices has been measured by c-axis transport. We show that only by changing the thickness of the superconducting YBa2Cu3O{7-δ} layers, it is possible to switch between quasi-particle and Josephson tunneling. From our data we deduce…
We have performed a theoretical study of the magnetic circular dichroism in the x-ray absorption spectra (XMCD) of the equiatomic CoPt and FePt ordered alloys as a function of the spin quantization axis. We found that the magnetization axis is along the [001] direction and the magneto-crystalline anisotropy energy (MC…
Several boron-modified polysilazanes of general type {B[C 2 H 4 Si(R)NH] 3 } n (C 2 H 4 = CHCH 3 or CH 2 CH 2 ) were synthesized and their thermal behavior studied. In contrast to the known derivatives with R = alkyl or aryl, we describe ceramic precursors in which the bulky moieties R are substituted with lower weigh…
Magnetron sputtering of transparent conductive oxides (zinc oxide, indium tin oxide, tin oxide) is a promising technique which allows the deposition of films at low temperatures with good optical and electronic properties. A special advantage is the scalability to large areas. The principles underlying magnetron sputt…
The crystal structures of Ca 2 (Fe 0.933 Al 0.067 ) 2 O 5 and Ca 2 (Fe 0.722 Ga 0.278 ) 2 O 5 have been determined from single crystals grown from a CaCl 2 flux. Both are isostructural with Ca 2 Fe 2 O 5 (C 2 F), belonging to space group Pnma. Lattice constants are a = 5.420(1) A, b = 14.743(3) A, c = 5.597(1) A and a…
Optical and photoemission experiments reveal unexpected spectral signatures of one-dimensional band insulators. In the model compound (NbSe (4))3I the optical conductivity decays as a power law sigma(1)(omega) approximately omega(-4.25) above a sharp gap edge. Photoemission observes both the valence and a shadow band,…
We have performed magnetic and transport measurements on La0.67Ca0.33MnO3 polycrystalline and partially melted samples. The magnetization and resistance decrease as sintering temperature is increased. The insulator-to-metal transition temperature is remarkably enhanced in the partially melted sample, enabling its poss…
The X-ray crystal structure of a reaction centre from Rhodobacter sphaeroides with a mutation of tyrosine M210 to tryptophan (YM210W) has been determined to a resolution of 2.5 A. Structural conservation is very good throughout the body of the protein, with the tryptophan side chain adopting a position in the mutant c…
Clinopyroxenes along the solid solution hedenbergite-aegirine M2[Ca2+1-xNa+xM1{Fe2+1-xFe3+x}Si2O6 were synthesized using hydrothermal techniques at 4 kbar. Different temperatures and redox conditions were used to determine optimum synthesis conditions and the stability range of individual compositions in the T - log f…
Our ab initio studies show that surface defects cause redistribution of the electron density which can increase substantially the binding energy of metal atoms to oxide surfaces. The results for electron (F(0)(s)) and hole (V(0)(s)) centers in the adhesion of Ag atoms (at 1:4 and 1:1 coverages) to a MgO(100) surface,…
The reduction of a solid NiAl2O4 cylinder to a metal-ceramic composite consisting of Ni particles in an Al2O3 matrix was monitored in situ at 1220 °C with neutron powder diffraction. The reaction kinetics was determined with a time resolution of 30 min. The reduction is associated with a volume shrinkage. A comparison…
Vegetable oil has been added in small amount to the rubber compound during mixing. It has been observed that the extent of cure obtained from the rheometric torque is lower for vegetable oil-containing compounds. This has been manifested from their physical and tensile properties. The lower abrasion and hardness of ve…
The simultaneous interaction of methyl radicals (CH3) and atomic hydrogen (H) with the surface of amorphous hydrogenated carbon (a-C:H) film is investigated. Two identical quantified beam sources for H and CH3 are used. The growth and/or erosion during the simultaneous interaction of the two beams with an amorphous hy…
Homoepitaxial diamond layers grown by chemical-vapor deposition in the presence of H2S, which were published to exhibit n-type conductivity, are carefully analyzed both electrically and structurally. Hall-effect measurements as a function of temperature clearly show the samples to exhibit p-type conduction, with an ac…