Materials Literature
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X-ray scattering studies on aligned films of binary mixtures of the normal alkanes ${\mathrm{C}}_{23}$${\mathrm{H}}_{48}$ and ${\mathrm{C}}_{28}$${\mathrm{H}}_{58}$ reveal, for the first time in such materials, the existence of a new equilibrium phase having the symmetry of a smectic crystal, possibly a hexatic. This…
Abstract Olefinic double bounds of a model styrene–isoprene diblock copolymer were hydrogenated using diimide (generated by a thermal decomposition of p ‐toluenesulfonyl hydrazide). The presence of byproducts and/or main‐chain structural alterations (e.g., degradation or cross‐linking), as a possible side effect of th…
Abstract In this article we consider characterization of the branching distribution of LLDPE by analytical TREF and by DSC techniques. Qualitatively, both methods yield parallel information, provided that the DSC samples are prepared at very slow cooling rates. Analytical TREF provides more quantitative information, h…
Abstract Six kinds of polyimide films with different molecular structures were synthesized and carbonized up to 1100°C. The carbonization behavior of polyimides was followed by measuring the changes in weight, size, and electrical conductivity. Pyrolysis gases evolved on the way to carbonize up to 1000°C were analyzed…
The forward and reverse water-gas shift reactions have been studied in detail in our laboratory over clean Cu(111) and Cu(110) single-crystal surfaces, which serve as good kinetic models for high-area Cu/ZnO catalysts. We review here the results of those studies. The steady-state kinetics of these reactions have been…
Heterogeneous catalysis is an important part of the technology that supports industrially developed societies. Production of transportation fuels, pollution control, production of low-cost and high-quality raw materials are just some of the areas in which heterogeneous catalysis impacts. The Council on Competitiveness…
Control over crystal growth by acidic matrix macromolecules is an important process in the formation of many mineralized tissues. Earlier studies on the interactions between acidic macromolecules and carboxylate- and carbonate-containing crystals showed that the proteins recognize a specific stereochemical motif on th…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLow-barrier hydrogen bonds and low fractionation factor bases in enzymic reactionsW. W. ClelandCite this: Biochemistry 1992, 31, 2, 317–319Publication Date (Print):January 21, 1992Publication History Published online1 May 2002Published inissue 21 January 1992https://pubs.acs…
The self-consistent theory of the structural, dynamical, and thermodynamic surface properties of anharmonic crystals previously given for one- and two-dimensional models is extended to the surfaces of three-dimensional crystals which take into account the surface anisotropy. After considering the reference system, in…
The temperature dependence of the lattice parameters in the beta -phase (BCC structure) of pure Zr and Zr-2 at.%Co was determined between 900 and 1550 degrees C by neutron diffraction. All diffraction patterns show a high diffuse background, which is identified as thermal diffuse scattering and originates from particu…
A microscopic model of liquid crystals, with frustrated dipolar, van der Waals, and benzene-ring steric hindrance interactions, yields reentrant phase diagrams with the sequence nematic--smectic-${\mathit{A}}_{\mathit{d}--}$nematic--smectic-${\mathit{A}}_{1--}$smectic-C. The Lindemann criterion of melting is adapted t…
We report the first direct measurement of the relaxation of plasma oscillations in a solid. Via the second-harmonic autocorrelation of femtosecond laser pulses, the lifetimes of localized plasma oscillations in silver island films were investigated. Decay times of 40\ifmmode\pm\else\textpm\fi{}7 fs were obtained, whic…
Model colloids composed of two widely separated sizes of poly- styrene spheres are studied at high volume fractions using an optical, multiple-scattering technique. These measurements probe hydrodynamic forces between unlike particles, as well as static, structural predictions made using the Percus-Yevick approximatio…
A reverse mode operation has been achieved in a polymer dispersed liquid crystal (PDLC) film by a novel methodology. A mixture of a dual frequency addressable liquid crystal (crossover frequency (fc): 13 kHz at 298 K), an acryl monomer and an acryl oligomer was irradiated by UV light under the application of an electr…
The third-order nonlinear optical properties of several porphyrin derivatives incorporated in thin films of polymethylmethacrylate have been measured by degenerate four-wave mixing at 598 nm with 1 ps pulses. Both the magnitude and dynamics of the nonlinear response are measured, with each system exhibiting both a sub…
The initial stages of oxidation of the Si(001)-2×1 surface have been studied using scanning tunneling microscopy and spectroscopy. Among the new sites generated by the exposure of this surface to O2 are 1.4 Å high bumps on top of the surface. Upon annealing the O2-exposed surface, or upon O2 exposure at an elevated te…
An investigation of subnanosecond switching of 119-microm radiation achieved by irradiating high-resistivity silicon wafers with 1.7-ns, 337-nm pulses from a nitrogen laser is presented. The experimental results are compared with a one-dimensional numerical multilayer model, which accounts for the generation, recombin…
Amorphous aluminum oxide thin films were prepared on glass and silicon (100) substrates by a low-temperature atmospheric-pressure chemical vapor deposition method. The raw material was aluminum acetylacetonate, which is nontoxic and easy to handle. The substrate temperature could be lowered to 250 °C by the thermal de…
It is demonstrated that photoluminescent porous Si (PS) layers exhibit definitely visible electroluminescence (EL). The PS layers were formed by anodization of single-crystal nondegenerate p-type Si wafers in an HF solution. The experimental EL cells are of the form semitransparent metal/PS layer/p-type Si/Al electrod…
ZnO-SnO2 thin films are deposited by rf sputtering using a sintered oxide target. As-deposited films show different crystal structures of a hexagonal ZnO, a spinel type intermediate compound Zn2SnO4 or an amorphous by experimental conditions. The Zn2SnO4 films show higher than 80% transmissivity over the visible range…