Materials Literature
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We calculate the transverse effective charges of zincblende compound semiconductors using Harrison's tight-binding model to describe the electronic structure. Our results, which are essentially exact within the model, are found to be in much better agreement with experiment than previous perturbation-theory estimates.…
A three-dimensional structure of two carbon nanotubes (CN) joined by a connecting region containing a pentagon and heptagon pair is given by the use of a projection method. The connecting joint is uniquely determined for the given two chiral vectors of CN by a vector which defines a three-dimensional dihedral angle. T…
The electronic structures of a wide range of early transition-metal (TM) compounds, including Ti and V oxides with metal valences ranging from 2+ to 5+ and formal d-electron numbers ranging from 0 to 2, have been investigated by a configuration-interaction cluster model analysis of the core-level metal 2p x-ray photoe…
Superlattices of $\mathrm{Si}/{\mathrm{SiO}}_{2}$ have been grown at room temperature with atomic layer precision using state of the art molecular beam epitaxy and ultraviolet ozone treatment. Photoluminescence was observed at wavelengths across the visible range for Si layer thicknesses $1<d<3\phantom{\rule{0ex…
Possible origins of ``colossal magnetoresistance'' (CMR) behavior in the ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ca}}_{\mathit{x}}$${\mathrm{MnO}}_{3}$ system are studied using the local spin-density method. These calculations allow the quantification of the effects of Mn d--O p hybridization tha…
Field-induced insulator-to-metal transitions have been found in ${\mathrm{Pr}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}(0.3<~x<~0.5)$ single crystals, which are accompanied by a melting of the insulating charge-ordered (i.e., ${\mathrm{Mn}}^{3+}$/${\mathrm{Mn}}^{4+}$ ordered) state. The tra…
By combining electron paramagnetic resonance (EPR), optical absorption, and photoluminescence (PL) spectroscopy, a strong correlation is observed between the green 510 nm emission, the free-carrier concentration, and the density of singly ionized oxygen vacancies in commercial ZnO phosphor powders. From these results,…
Ionic transport properties and battery discharge studies on the fast ion conducting quenched mixed glass system x[0.75AgI:0.25AgCl]: (1 - x)[ ] are reported, where in molar wt %. The conventional host AgI has been replaced by an alternative compound: `a quenched [0.75AgI:0.25AgCl] mixed system'. The compositional rati…
A theoretical treatment, based on the Devonshire theory of ferroelectrics, is presented to describe the storage of electrostatic energy in ferroelectric and paraelectric materials at very high field strengths. In all cases, optimal energy density is achieved by using compositions with Curie temperatures well below the…
The effect of the energy overlap integral, due to the partial overlap of the adjacent wave functions of impurities, on the dielectric response ε of n-type semiconductor is examined. The proposed model suggests that ε diverges as the overlap increases, i.e. as the impurity concentration n is increased and essentially g…
Polystyrenes with different molecular weights were chemically modified with maleic anhydride by use of certain cationic catalysts of Lewis acid type (BF3·OEt2, AICI3, TiCL4, ZnCl2, FeCl3, and SnCl4) in chloroform. The effects of molecular weight of polystyrene, as well as type of Lewis acid used, on properties and str…
Toughening of polypropylene was carried out by adding two types of ethylene-propylene rubber (EPR) having different ethylene content, and three commercial types of EPR containing high density polyethylene (PE). The concentration of EPR was varied from 0–30%. Globular morphology of the dispersed phase was observed at a…
New fluorinated thermoplastic elastomers (FTE) with perfluoropolyether (PFPE) blocks have been synthesized by reacting a fluorinated macrodiol with aromatic diisocyanates in the presence of a solvent, followed by subsequent chain extension with low molecular weight aliphatic or aromatic diols. Tensile properties measu…
An interfacial model was proposed for the ternary thermoplastics (matrix)/elastomer/rigidparticle filler composite with high strength, high toughness, and high modulus. A dispersed phase of rigid particle as a core and elastomer as a shell that has a good interfacial adhesion with the matrix is the key point of the mo…
ADVERTISEMENT RETURN TO ISSUEPREVArticleMetalloporphyrins as Initiators for Living and Immortal PolymerizationsTakuzo AidaTakuzo AidaDepartment of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, JapanMore by Takuzo Aida and Shohei Inoue*Shohei InoueDep…
Three complexes of the general form [SbCl 3 ] 4 ·[Ph−Ph] ([Ph−Ph] = bibenzyl, trans -stilbene, or diphenylacetylene) have been isolated in high yield as crystalline solids. The characteristics of the new materials significantly differ from those of the precursors, and their solid state structures have been determined…
A general kinetic model to describe the interaction of two dissimilar olefins with cobalt(II) tetrakis(anisyl)porphyrin complexes in the presence of organic radicals has been developed. The kinetic scheme presumes the formation of organometallic products both by radical addition to Co(II) and by reaction of hydridocob…
We present a theoretical approach to study the dielectric properties of porous ceramics and composite materials and explain the experimentally observed notable influence of the coupling between the components of a saturated porous ceramic on the final behavior of the sample. This model is based on the assumption of a…
The results of susceptibility and neutron inelastic scattering measurements on the pyrochlore compound are presented. The crystal-field ground state of the ion has zero spontaneous magnetization, and a virtually dispersionless crystal-field excitation is observed. It is concluded that the crystal-field interaction dom…
The effect of crystallization temperature on the electrical properties of sol-gel derived Pb(Zr,Ti,Nb)O3 or PNZT capacitors with La0.5Sr0.5CoO3 (LSCO) electrodes has been investigated. It is demonstrated that LSCO//PNZT(4/30/70)//LSCO capacitors can be fabricated at temperatures as low as 550 °C without significant de…