Materials Literature
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Aggregation in the nondoped polyaniline, emeraldine base (EB), as observed by GPC in a N -methyl-2-pyrrolidinone (NMP) solution, was found to be closely related to the fraction of the imine nitrogen atoms in the nondoped polymer, i.e., to the oxidation state of the polymer. As EB was reduced to leucoemeraldine base (L…
Dielectric, ferroelectric and piezoelectric pŕoperties of a BNT-based solid solution, (1-x)(Bi1/2Na1/2)TiO3-xNaNbO3, that is, Bi(1-x)/2Na(1+x)/2 Ti1-x Nb x O3 (BNTN-100x), are studied from the viewpoint of a new group of lead-free piezoelectric ceramics. The conventional ceramic fabricating technique was used to prepa…
The corrosion behavior of copper in aqueous solutions of different pH values was investigated using electrochemical and surface analysis methods. It was shown that the corrosion mechanism changed with pH and was associated with morphology of the surface films formed. In solution of pH 3, the copper surface was covered…
The syntheses of two new derivatives of 3,4-ethylenedioxythiophene (EDOT), specifically 5-octyldioxeno[2,3- c ]thiophene (EDOT-C 8 ) ( 2 ) and 5-tetradecyldioxeno[2,3- c ]thiophene (EDOT-C 14 ) ( 3 ), and their polymers are reported in this paper. Cyclic voltammetry of 2 and 3 in 0.1 M TBAP/CH 3 CN show irreversible m…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSelective Catalytic Hydroxylation of a Steroid by an Artificial Cytochrome P-450 EnzymeRonald Breslow, Xiaojun Zhang, and Ying HuangView Author Information Department of Chemistry, Columbia University New York, New York 10027 Cite this: J. Am. Chem. Soc. 1997, 119, 19,…
Polycatenar mesogens have a shape intermediate between classical rod‐like and disc‐like liquid crystals which allows practically all the mesomorphic symmetrics to be obtained with the same molecular core by varying the temperature or the number and position of grafted chains (see Figure: R = H(CH 2 ) n O). The synthes…
Hexagonally closed packed monolayers of colloids have found more and more applications, e.g. as lithographic masks. The monolayers are usually produced with the help of a self-organizing process where a suspension of colloids is applied to the desired substrate and left to dry. This method requires a good wettability…
Low-rate dynamic contact angles and static advancing contact angles of 13 liquids were measured, respectively, by axisymmetric drop shape analysis (ADSA) and a conventional goniometer technique, on two copolymers, poly(propene- alt - N -( n -propyl)maleimide) and poly(propene- alt - N -( n -hexyl)maleimide); both have…
High‐density nickel–dispersed‐alumina (Al 2 O 3 /nickel) composites with superior mechanical properties were obtained by the hydrogen reduction and the hot pressing of alumina–nickel oxide (Al 2 O 3 /NiO) mixed powders. The mixtures were prepared by using NiO or nickel nitrate (Ni(NO 3 ) 2 · n H 2 O) as a dispersion s…
The first mesoporous materials (pore diameter between 20 and 100 Å) were discovered just five eyars ago. A new approach to mesoporous materials by direct templating of lyotropic liquid crystals is reviewed and compared with strategies reported previously. The direct templating method is shown to be very verstile. It i…
This paper describes the tensile, impact, flexural properties and aging behavior of short banana fiber reinforced polyester composites with special reference to the effect of fiber length and fiber content. Maximum tensile strength was observed at 30 mm fiber length while impact strength gave the maximum value for 40…
Multilayer thin films comprised of sequentially adsorbed layers of partially doped polyaniline and a polyanion, sulfonated polystyrene, were fabricated via the use of a simple layer-by-layer molecular-level processing scheme. Using this simple multilayer polymer adsorption process, uniform thin films of polyaniline in…
The electronic dynamics of gold nanocrystals, passivated by a monolayer of alkylthiol(ate) groups, were studied by transient spectroscopy after excitation with subpicosecond laser pulses. Three solution-phase gold samples with average particle size of 1.9, 2.6, and 3.2 nm with size distribution less than 10% were used…
The distribution and orientation of platelet‐shaped particles of α‐alumina in a fine‐grained alumina matrix is shown to template texture development via anisotropic grain growth. The textured microstructure ranges from 4 wt% oriented platelet particles in calcined samples to nearly 100% oriented α‐Al 2 O 3 grains afte…
The fiber morphology of the dragline silk of Nephila clavipes has been investigated by the detailed analysis of wide-angle X-ray diffraction (WAXD) patterns. WAXD gives the crystal lattice dimensions, the orientation distribution, the crystalline fraction, and an estimate of the crystal size. It is found that the crys…
The influence of Mott-Hubbard electron-electron correlations on the electronic structure and structural stability of uranium dioxide (UO2) has been analysed using the local spin-density approximation (LSDA) + U approach. We have found that the inclusion of a term describing the Hubbard on-site repulsion between 5f ele…
A variable-temperature, -pressure, and -ionic strength (1)H NMR study of the DOTA complexes of different trivalent cations (Sc, Y, La, Ce --> Lu) (DOTA = 1,4,7,10-tetraaza-1,4,7,10-tetrakis(carboxymethyl)cyclododecane) yielded data that are in contradiction with the hitherto used model of only two enantiomeric pairs o…
Superlattices consisting of alternating layers of extremely thin films often demonstrate strong quantum size effects that have been utilized to improve conventional devices and develop new ones. The interfaces in these structures also affect their thermophysical properties through reflection and transmission of heat c…
A new method has been used to obtain pore size characteristics of MCM-41 catalyst supports and vanadium-substituted MCM-41 catalysts. The approach is based on the nonlocal density functional theory (NLDFT) model for nitrogen and argon adsorption in MCM-41, proposed recently. Samples with pore sizes varying from ca. 25…
The optical absorption edge and the near-absorption edge characteristics of undoped ZnO films grown by laser ablation on various substrates have been investigated. The band edge of films on C [(0001)] and R-plane [(1102)] sapphire, 3.29 and 3.32 eV, respectively, are found to be very close to the single crystal value…