Materials Literature
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Director configurations in nematic Liquid Crystals can be determined by minimizing their elastic free-energy density, on the basis of elastic constants and of specific boundary conditions; in some published cases, this has been obtained by numerical procedures where the elastic free-energy density plays the same role…
The relationship between the growth rate of the hydroxyapatite (0001) face and bulk supersaturation of a simulated body fluid was measured by real-time Moire phase shift interferometry. It was found that the (0001) face grew in the multiple two-dimensional nucleation mode, from surface observation by atomic force micr…
Cathodic reduction of a mixed metal nitrate solution containing La 3+ and Mn 2+ ions leads to the deposition of an X-ray amorphous mixed hydroxide coating, which on heat treatment (950 °C, 2 h) yields an adherent coating of LaMnO 3 . This method can be adapted as a simple alternative to such conventional methods of fa…
The likely mechanism which allows the required migration of functional groups for solid-state polymerization (SSP) of polyamides and polyesters is shown to be interchange reactions. This “chemical diffusion” of functionality has exactly the same mathematical form as that of classical diffusion of small molecules. The…
Molecular weight driven competitive adsorption of PEO [poly(ethylene oxide)] from aqueous solutions on silica was studied by employing total internal reflectance fluorescence (TIRF) and near-Brewster angle reflectivity. Coumarin tags on PEO chain ends facilitated the distinction between two competing populations diffe…
A method for producing diffractive optical elements (DOE's) for multiple wavelengths without chromatic aberration is described. These DOE's can be designed for any distinct wavelength. The DOE's are produced from two different optical materials, taking advantage of their different refractive indices and dispersions.
The structure and dynamics of the “strong” glass of poly( n -decyl methacrylate) (PnDMA) have been studied, respectively, with X-ray diffraction and dielectric spectroscopy, dynamic light scattering, and rheology at temperatures below and above the glass transition temperature T g ∼ 215 K. We find three dielectrically…
An overview is presented of size-selective photoetching experiments on nanocrystalline semiconductor particles. Four different compounds (CdS, ZnS, PbS, and ZnO) have been prepared by standard colloid−chemical synthetic methods. For CdS, the initial mean radius of 35 Å could be gradually decreased to 7.5 Å by size-sel…
We introduce a kinetic model of coarsening of transient polymer networks during the intermediate stages of phase separation in polymer systems. The model explicitly takes into account the effect of the connectivity of polymer chains. We show that during the intermediate stages the size of the droplet grows according t…
This paper focuses attention on the intrazeolite anchoring of ruthenium carbonyl clusters and their catalytic performances. The synthesis involves the adsorption of metal carbonyl species or metal ion exchange into zeolite cages followed by reductive carbonylation under a mixed CO and H 2 atmosphere. The characterizat…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTSynthesis of Soluble Fluorinated Vinyl Ether Copolymers by Ionic Addition of Fluoroolefins to Poly(vinyl alcohol)Andrew E. Feiring and Edward R. WonchobaView Author Information DuPont Central Research & Development, Experimental Station, P.O. Box 80328, Wilmington, Delaware 198…
The magnetization of Ni_{1-x}Mo_{x} single crystals with x=4,6,8 and 10 % by weight have been measured at 4.2K using a vibrating sample magnetometer and a Superconducting Quantum Interference Device (SQUID). The magnetization of the alloy at these low concentrations and at 0 K have been theoretically determined by usi…
The well-known and general “compressibility theorem” for pure substances relates κT =−(∂ ln V/∂p)N,T to a spatial integral involving the pair correlation function g(2). The isochoric inherent structure formalism for condensed phases separates g(2) into two fundamentally distinct contributions: a generally anharmonic v…
The exact mean-field phase behavior of the Semenov–Vasilenko model for rod-coil diblock copolymers is studied by applying self-consistent field techniques. The behavior depends on three quantities: the rod/coil immiscibility χN, the coil volume fraction f, and the ratio ν of the characteristic coil to rod dimensions.…
The electron transport coefficients, the drift velocity W , the product of the gas number density and the longitudinal diffusion coefficient and the ratio of the longitudinal diffusion coefficient to the electron mobility of electrons were measured in pure oxygen over the range 1.7-350 Td and in two oxygen-argon mixtu…
Solid phase epitaxial growth of ion beam-amorphized α-quartz has been studied by means of Rutherford backscattering spectrometry in channeling geometry. α-quartz single crystals were irradiated with Cs+ and Xe+ ions and annealed in air or in vacuum at 500–900 °C. Complete epitaxial regrowth has been observed in the Cs…
Fatigue phenomena occurring in Pb(ZrxTi1−x)O3 ferroelectric thin-film capacitors (FECAP) with Pt electrodes are studied by means of conduction measurements in the cold-field-emission (tunneling) regime. We have determined that conduction in virgin FECAPs is controlled by tunneling at temperatures 100–140 K and electri…
Based upon kinetic Monte Carlo simulations of crystallization in a simple polymer model we present a new picture of the mechanism by which the thickness of lamellar polymer crystals is constrained to a value close to the minimum thermodynamically stable thickness. This description contrasts with those given by the two…
Non-dipolar effects in the angular distribution of core level photoemission are shown to have a substantial influence on the interpretation of x-ray standing wavefield determinations of surface adsorption structures when the x-ray absorption is monitored by photoemission, even at photon energies below 3 keV. Results f…
We observed the emission of correlated electron pairs from the valence band of solids following the absorption of single photons in the vacuum ultraviolet range. Applying a time-of-flight technique, we measured the energy distributions of correlated electron pairs emitted from clean Cu(001) and Ni(001) crystals. Signi…