Materials Literature
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Chrysotile asbestos is formed by densely packed bundles of multiwall hollow nanotubes. Each wall in the nanotubes is a cylindrically wrapped layer of Mg(3)Si(2)O(5)(OH)(4). We show by experiment and theory that the infrared spectra of chrysotile present multiple ionic-plasmon resonances in the Si-O stretching bands. T…
The phenomenally large enhancement in conductivity observed when Li-doped MgO crystals are oxidized at elevated temperatures was investigated by dc and ac electrical measurements in the temperature interval 250--673 K. The concentration of $[\mathrm{Li}{]}^{0}$ centers (substitutional ${\mathrm{Li}}^{+}$ ions each wit…
In-plane anisotropy of the resistivity and thermopower was measured for single crystal Bi2-xPbxSr2Co2Oy. There is large in-plane anisotropy, which is attributed to the anisotropic pseudogap formation due to the different crystal symmetry between the square Bi2Sr2O4 layer and the triangular CuO2 layer. The magnitude of…
We use synchrotron x-ray and precision electron diffraction techniques to determine accurately the structure factors of selected reflections that are sensitive to the valence electron distribution in the superconductor MgB2. These values deviate significantly from calculated structure factors using the scattering fact…
Controlling growth: Large arrays of oriented conducting polymer nanowires were prepared by controlled nucleation and growth during a stepwise electrochemical deposition process, without the use of porous membrane supports (see scheme and electron micrographs).
Es bien sabido que las interacciones de canje inducidas entre materiales ferromagneticos (FM) y antiferromagneticos (AFM) cuando son enfriados desde una temperatura superior a la temperatura de Neel, TN, del AFM, hacen aumentar la coercividad, HC, del componente FM. Nosotros hemos analizado los efectos de hacer una mo…
Abstract The degradation of polyfuran in a wet acetonitrile solution and in an aqueous solution has been investigated with a cyclic voltammetry technique, along with Fourier transform infrared and Fourier transform Raman spectroscopy techniques. Infrared spectroscopy shows that the main defects that exist in polyfuran…
Luminescence is reported from the ${}^{2}{\mathrm{I}}_{11/2}$ level of ${\mathrm{Er}}^{3+},$ in the cubic elpasolite lattices ${\mathrm{Cs}}_{2}{\mathrm{NaErCl}}_{6}$ and ${\mathrm{Cs}}_{2}{\mathrm{NaYCl}}_{6}.$ Altogether, with the use of ultraviolet laser excitation, 11 transitions from ${}^{2}{\mathrm{I}}_{11/2}$ $…
Abstract A water‐swellable rubber (WSR), compatibilized by the amphiphilic block copolymer, has been prepared by blending a natural rubber (NR) matrix with crosslinked sodium polyacrylate (CSP), poly(ethylene oxide)‐b‐poly(butyl acrylate) (PEO‐b‐PBA), poly(ethylene glycol) (PEG), reinforced filler, and vulcanizing age…
This work presents the spectroscopic characterization of Tm 3+ doped gallium lanthanum sulfide (GaLaS) chalcogenide glass through absorption, fluorescence and lifetime measurements of excited 3 H 4 and 3 F 4 states, and a study of Tm 3+ :Tm 3+ energy transfer. The cross relaxation 3 H 4 , 3 H 6 → 3 F 4 , 3 F 4 respons…
MP2/6-31+G(d) calculations are used to compare the static electronic first hyperpolarizability (β) of planar and twisted sesquifulvalenes. The longitudinal component of β which is dominant in both structures is more than five times larger in the twisted form where it points in the opposite direction from the dipole mo…
Polymer-embedded La 2/3 Sr 1/3 MnO 3 (LSMO) composites, (LSMO) 1 −x (PPP) x (PPP is polyparaphenylene, and x is the weight fraction of PPP), were prepared by mixing pre-prepared LSMO and PPP powders. Thermogravimetric analysis, x-ray diffraction, and infrared spectra show that the composites are stable when calcined a…
Abstract Simple blends with different viscosity ratios of the components as well as compatibilized blends varying both in type and content of compatibilizers were used to study the relation between interfacial tension and dispersed‐phase particle size for PP/EPDM (80/20 wt %) blends in this work. Four compatibilizing…
Abstract A method, based on microtoming and GC analysis, for studying migration of additives inside polymers as a function of space and time was validated for Irganox 1076 migrating from low‐density polyethylene to ethanol. The consistency of the mass balance of the total amount of Irganox 1076 in the polymer and the…
Abstract We carried out a feasibility study of the use of black rice husk ash (RHA) as a filler in epoxy resin for embedding material in electrical and electronic applications. We made a comparison by mixing RHA and two commercial fillers, fused and crystalline silica, with epoxy resin at weight fractions ranging from…
Abstract Optically active alicyclic polyimides were prepared for the first time from (−)‐[1 S *,5 R *,6 S *]‐3‐oxabicyclo[3.2.1]octane‐2,4‐dione‐6‐spiro‐3′‐(tetrahydrofuran‐ 2′,5′‐dione) [(−)‐DAn] via polycondensation with diamines and subsequent chemical or thermal imidization. The dianhydride (−)‐DAn was synthesized…
A theoretical approach is developed for reconstructing phonon dispersion in Si nanocrystals. It is found that for Si nanocrystals with size larger than 2 nm, smeared phonon dispersion could be established. The evolution of nanocrystal phonons into bulk ones is studied. Frequency shifts of bulk-like phonons versus nano…
Abstract Polarized Fourier transform infrared (FTIR) and ultraviolet‐visible (UV‐VIS) spectroscopy were used to investigate the photodegradation direction of polarized UV (PUV)‐irradiated polyimide (PI) films based on pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA). PI films strongly absorb below 350 nm, r…
We report here photoluminescence of CdS nanoparticles suspended in vacuum. The CdS nanoparticles, whose size distribution was bimodal having peaks at 11.3 and 43.1 nm, were produced by the gas-evaporation method and the nanoparticle beams were formed within the rarefied inert-gas flow. The band-edge emission and surfa…
Abstract Ultrafine carboxylated styrene–butadiene rubber(CSBR) powders were prepared by using gamma irradiation and following spray‐drying method. The influences of dose rate, absorbed dose, and sensitizer content on the crosslinking density of CSBR latices were studied in detail. Then the ultrafine CSBR powders were…