Materials Literature
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Ion implantation induced dc electrical conductivity changes in polycrystalline WO3 thin films was examined. Helium, argon, and tungsten ions were implanted under the following conditions: helium at 90 keV, argon at 360 keV, and tungsten at 300 keV. The fluence range studied was from 1×1017 to 3×1017 cm−2 for helium an…
A method for crystallizing oriented samples of the γ-phase of isotactic polypropylene (iPP) under atmospheric pressure in the presence of nucleating fibers has been developed. The technique uses iPP grades of high molecular weight and high isotacticity and produces a mixture of α and γ-phase crystals within the matrix…
A Landau free energy is derived for the weak segregation regime (WSR) of melts belonging to a very general class of statistical multiblock copolymers, referred to as “multiple segment-type statistical multiblock copolymers.” Copolymer chains in this class consist of sequences of up to M⩾2 chemically different types of…
Poly(dimethylsiloxane) was studied by laser Raman spectroscopy and differential scanning calorimetry. The SiOSi skeletal mode at 489 cm−1 and the CSiC deformation bands at 188 cm−1 and 158 cm−1 were studied as functions of temperature from ambient to −130°C, and effects of temperature interpreted in accordance wit…
Barium dicobalt(II) bis(phosphate) is built up from BaO12 polyhedra [dav(Ba—O) = 2.995 (1) Å], CoO6 octahedra [dav(Co—O) = 2.098 (2) Å] and PO4 tetrahedra [dav(P—O) = 1.544 (2) Å]. The structure has a strongly layered nature, with Ba2+ cations interspersing infinite sheets of edge-sharing CoO6 groups, which are capped…
${}^{29}\mathrm{Si}$ nuclear magnetic resonance spectra were measured to characterize porous silicon structures. ${}^{29}\mathrm{Si}$ nuclei close to surface were selectively detected both in cross-polarization and non-cross-polarization spectra. The spectra were different from those for amorphous silicon and amorphou…
The thermal response of tussah (Antheraea pernyi) silk fibroin films treated with different water–methanol solutions at 20°C was studied by means of dynamic mechanical (DMA) and thermomechanical (TMA) analyses as a function of methanol concentration and treatment time. The DMA curves of α-helix films (treated with ≥80…
We report the results of an optical study of the Mott transition in ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ carried out by time- and frequency-domain spectroscopies. We have observed time-resolved spectra through the Mott transition with oscillations in reflectivity associated with the fully symmetric modes. As a consequen…
We present a band structure study of orbital polarization and ordering in the two-dimensional triangular-lattice transition metal compounds LiVO 2 and NaTiO 2 . It is found that while in NaTiO 2 the degeneracy of t 2 g orbitals is lifted due to the trigonal symmetry of the crystal and the strong on-site Coulomb intera…
A measurement of electrical conductivity and Hall effect has been made for thin film La0.5Sr0.5CoO3−δ (LSCO) prepared on (001) SrTiO3 substrates by pulsed laser deposition under reduced oxygen pressures. A considerable effect of oxygen stoichiometry on electrical resistivity of LSCO thin films has been observed. The s…
The photoconductivity of tetrahedral amorphous carbon (ta-C) and hydrogenated tetrahedral amorphous carbon (ta-C:H) has been studied as a function of temperature, photon energy, and light intensity in order to understand the transport and recombination processes. ta-C and ta-C:H are found to be low mobility solids wit…
The Ginzburg criterion, which is based on the three coefficients in the Landau–Ginzburg (LG) expansion of the Helmholtz free energy density of a nonuniform system, is believed to give a reasonable estimate for the temperature scale on which crossover occurs. To compute the contribution of the square-gradient term in t…
Complete polarizabilities and first hyperpolarizabilities (which include zero-point-vibrational averaging and other vibrational corrections) have been calculated at the self-consistent-field and Møller–Plesset second order perturbation levels of approximation for CH4, CF4, and CCl4. As well as the static values, α(−ω;…
The Raman response of the radial breathing mode in single-wall carbon nanotubes was analyzed for excitation with 10 different laser lines. The line shape was fitted with 14 Voigtian oscillators which could be correlated to tubes of different helicity. The strongest lines were observed between 172 and 199 cm −1 . For a…
Computer simulation by numerically solving the time-dependent Schr\"odinger equation was used to investigate image formation during scanning tunneling microscope (STM) imaging of three-dimensional objects with radii of curvature comparable with that of the STM tip. The results were compared with experiment. When the n…
General topological rules determine the carbon ring structures in arbitrary sp2-bonded structures, particularly nanotube junctions.Received 23 June 1998DOI:https://doi.org/10.1103/PhysRevB.58.12671©1998 American Physical Society
Living ring opening polymerization of ε-caprolactone initiated from the numerous chain-end hydroxymethyl groups of the analogous dendrimeric and hyperbranched polyesters derived from 2,2-bis(hydroxymethyl) propionic acid is described. By controlling the size of the dendritic macromolecule and the molar ratio of ε-capr…
We describe real-space imaging measurements of the interactions and elastic properties of charge-stabilized colloidal crystals. Interactions between charge-stabilized latex spheres self-assembled into colloidal crystals are extracted from single-particle dynamics using new techniques in digital video microscopy. The s…
In order to investigate subtle differences in the local structure and bonding of amorphous ices, glassy liquid water was produced by rapid cooling of micrometer sized water droplets. Samples were first studied with power x-ray diffraction (PXRD) and differential scanning calorimetry (DSC) to ensure that the production…
Hard spheres with a polydispersity above approximately 8% are shown to crystallise into two phase-separated solid phases. A polydispersity above 8% is too large to be tolerated by a single solid phase but phase separation produces two fractions with polydispersities sufficiently narrow to allow them to crystallise. It…