Materials Literature
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The structures of the polar surfaces of ZnO are studied using ab initio calculations and surface x-ray diffraction. The experimental and theoretical relaxations are in good agreement. The polar surfaces are shown to be very stable; the cleavage energy for the (0001)-Zn and (0001;)-O surfaces is 4.0 J/m(2) comparable t…
Field emitters comprised of aligned carbon nanotubes are shown to be promising as a primary electron source in an x-ray tube working in a nonultrahigh vacuum ambience. At a pressure of 2×10−7 Torr, the nanotube emitters continue to emit electrons for more than 1 h, and yield better resolved x-ray images than do thermi…
The origin of ultrahigh piezoelectricity in the relaxor ferroelectric ${\mathrm{PbZn}}_{1/3}{\mathrm{Nb}}_{2/3}{\mathrm{O}}_{3}\ensuremath{-}{\mathrm{PbTiO}}_{3}$ was studied with an electric field applied along the [001] direction. The zero-field rhombohedral $R$ phase starts to follow the direct polarization path to…
We have measured, as a function of temperature and frequency, the velocity and attenuation of sound down to the glass transition of the fragile glass-forming molecular liquid m-toluidine. The mechanical relaxation process is compared with the dielectric one recently studied on the same substance. The Arrhenius plot of…
We have used molecular dynamics simulation and thermodynamic arguments to analyze the pressure-area curve resulting from the compression of a monolayer of nanoparticulates at a liquid–vapor interface. The pressure–area isotherm produced by molecular dynamics simulation shows characteristics common to experimental isot…
To study the liquid–solid and solid–solid phase transitions of a confined O2, we performed x-ray diffraction measurements of O2 confined inside the cylindrical pores of six kinds of regular mesoporous adsorbents (MCM-41 and SBA-15) with different pore radii (R=2.1, 2.9, 3.9, 4.5, 5.3, and 7.0 nm) as a function of temp…
Wide band dielectric spectroscopy has been used to study the bulk dynamics of the simple supercooled liquid m-toluidine. Following the temperature and frequency dependence of the dielectric response we find a stretched relaxation process, the stretching parameter of which is temperature dependent. The observed decoupl…
Electron and phonon transport in nanostructures is characterized by interface effects and can deviate significantly from the assumption of local thermal equilibrium underlying the transport equations at macroscale. In this article, we elucidate some basic nonequilibrium characteristics for phonon and electron transpor…
Past studies suggest that phonon confinement and the associated group velocity reduction are the causes of the observed drop in the cross-plane thermal conductivity of semiconductor superlattices. In this work, we investigate the contribution of phonon confinement to the in-plane thermal conductivity of superlattices…
A new pyridinium compound, (C5H5NH)5Bi2Br11, has been synthesized. The x-ray diffraction studies indicate that its structure is built up of four independent pyridinium cations and isolated Bi2Br115− groups. At room temperature it crystallizes in the monoclinic space group P21/n. Two phase transitions of second- and fi…
A solar cell illuminated by circularly-polarized light generates charge and spin currents. We show that the spin polarization of the current significantly exceeds the spin polarization of the carrier density for the majority carriers. Based on this principle we propose a semiconductor spin-polarized solar battery and…
Size exclusion chromatography in combination with multiangle laser light scattering and viscometry was applied for the study of the branched structures of commercial dextrans. Shrinking factors g = R g, i 2 branch / R g, i 2 linear and g ‘ = [ η ] i,branch /[ η ] i,linear were calculated, where the radii of gyration o…
The synthesis and characterization of the first metal phosphate containing 4,4‘-bipyridine in two distinct forms is described; the structure consists of phosphate-bridged vanadium(III) chains, which are linked through 4,4‘-bipyridine ligands to form anionic {[V2(HPO4)4(4,4‘-bpy)2]2-}∞ sheets with the charge-compensati…
We present here the results of neutron and X-ray reflectivity studies on the effects of solvent flow on the height and density profile of polymer chains chemically end-tethered to a surface. Our system consists of perdeuterated polystyrene chains, molar mass 80 000, that were chemically tethered to a silicon oxide sur…
The interaction of CO with K-free and K-covered Mo 2 C/Mo(100) surfaces has been investigated by HREELS, AES, and TPD. CO adsorbed molecularly on the clean Mo 2 C/Mo(100) surface at 140 K. A part of the adsorbed CO desorbed from the saturated adlayer with T p = 330 K, which was accompanied by dissociation of the molec…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSpectroscopic Evidence for Nitric Oxide Binding with Cob(II)alaminDonghong Zheng and Ronald L. BirkeView Author Information Department of Chemistry and Center for Analysis of Structures and Interfaces (CASI), The City College of New York, and The Graduate School and Un…
Brightly and uniformly colored passive layers on Ti are formed by application of ac polarization in aqueous NH 4 BF 4 . A wide spectrum of well-defined colors is accomplished by varying the ac voltage. The passive films are stable in the ambient and in aqueous chloride, perchlorate, and sulfate solutions. Optical micr…
Stereoregular polymerization of ( p -3-methylbutoxy)phenylacetylene (p3MBPA) was successfully performed with a [Rh(NBD)Cl] 2 catalyst to afford poly( p -3-methylbutoxy)phenylacetylene (Pp3MBPA) having a cis-transoid form in high yields when ethanol or 1-butanol in the presence of triethylamine was used as the polymeri…
We report a study of the effect of shear deformation on the static structure factor, S ( q ), of a thermoreversible gel of organophilic colloidal silica ( a = 40 nm) in the solvent hexadecane. Small- and wide-angle light scattering measurements show that the quiescent structure of these gels is consistent with that of…
Novel dendritic polyphenylazomethines (DPAs), which consist of a pi-conjugated backbone, were synthesized up to the fourth generation by the convergent method via dehydration of aromatic ketones with aromatic amines in the presence of titanium(IV) tetrachloride. The obtained dendrimers, DPA G1-4 (designated as GX, whe…