Materials Literature
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The drying mechanism of semicrystalline poly(vinyl alcohol) (PVA) was investigated. PVA samples of various molecular weights were crystallized by annealing at temperatures slightly above the glass transition temperature of PVA, and swollen in water for different time periods. The water volume fraction in the sample wa…
The effect of substrate temperature on the homoepitaxial growth process of a SrTiO3(001) surface has been investigated using our crystal growth molecular dynamics simulation code. SrO molecules were continuously deposited one by one on the SrTiO3(001) surface terminated by TiO2 atomic plane at 300 K. Two-dimensional a…
Three-amide oligomers of nylon 6 and nylon 6 6 have been investigated using electron microscopy (imaging and diffraction), X-ray diffraction, and computational modeling. A new crystal structure has been discovered for the three-amide oligomer of nylon 6. This material crystallizes from chloroform/dodecane solutions in…
Optical absorption spectra of nanoclusters of lead iodide, synthesized by the colloidal technique, have been investigated. It is shown that the absorption peaks are due to different orders of interband transitions of a nominally single size of particles rather than the first-order transitions of a number of discrete s…
In this article we will focus on the dielectric properties of laminates and blends of a partially conducting (the liquid crystalline copolyesteramide Vectra B950) and an insulating (polypropylene or mica) phase. Dielectric spectroscopy was used as a tool to obtain information about the influence of the dimensions of t…
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…