Materials Literature
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We report the observation of the pressure-induced high-spin to low-spin transition in FeS using new high-pressure synchrotron x-ray emission spectroscopy techniques. The transition is evidenced by the disappearance of the low-energy satellite in the Fe K$β$ emission spectrum of FeS. Moreover, the phase transition is r…
We present an analytical study of the spatial decay rate $γ$ of the one-particle density matrix $ρ(\vec r,\vec r')\sim\exp(-γ|\vec r-\vec r'|)$ for systems described by single particle orbitals in periodic potentials in arbitrary dimensions. This decay reflects electronic locality in condensed matter systems and is al…
Abstract A computer scaling study was conducted to predict the possibility of scale formation when seawater is injected into the northern Kuwaiti oilfields for reservoir pressure maintenance. Results indicated that the seawater is likely to be self-scaling with respect to calcium carbonate at reservoir conditions. The…
We consider the problem of a diblock copolymer thin film melt on a striped surface. The striped surface induces the lamellae to orient perpendicularly to the surface and align commensurate with the stripes at the bottom of the film. In all practical cases at the top of the thin film the free surface will prefer one bl…
The mode-coupling theory for the evolution of glassy dynamics in simple liquids yields correlation functions that, outside the transient regime, can be written as a superposition of relaxators with a broad distribution of relaxation rates. The known asymptotic laws for the dynamics near an ideal glass transition imply…
Heat-resistant flexible-film optical waveguides were fabricated from fluorinated polyimides. These waveguides operated in single mode and had low optical loss (0.3 dB/cm) at a wavelength of 1.3 microm for TE and TM polarizations. They also had good flexibility: The optical loss did not significantly change above a min…
Using rheometry and light scattering, we have studied the viscoelasticity of gels formed by the kinetically arrested phase separation in an emulsion−polymer mixture; to prevent the gels from collapsing under their own weight, we have used an isopycnic solvent. At constant osmotic pressure (set by the polymer concentra…
A new method is presented to generate and to fixate compositional gradients in blends of two miscible and amorphous polymers. A compositional gradient is introduced into a solution of a polymer in a monomer by use of a centrifugal field, and this gradient is subsequently fixated by polymerization of the solvent-monome…
Molecular reorientation in the two amorphous phases of triphenyl phosphite, namely the supercooled liquid (phase aI) and the newly discovered second amorphous phase (phase aII), was investigated by dielectric relaxation and by two-dimensional (2D) nuclear magnetic resonance spectroscopy (NMR) in the time and frequency…
Ikaite, calcium carbonate hexahydrate, has by means of X-ray diffraction analyses of frozen samples been identified as the mineral component of the white spots formed in the shell of frozen shrimp during storage. When the shrimp thaw and the shell material is dried and kept at room temperature, ikaite rapidly transfor…
The valence change of samarium from trivalent to divalent in strontium hexaborate (SrB 6 O 10 ) prepared in air is observed. The temperature dependence of the luminescence and vibronic transitions of Sm 2+ are studied. The Sm 2+ ions occupy three crystallographic sites. With increasing temperature, the 5 D 0 → 7 F 0 t…
Nonlocal density functional theory [DFT] has been used to compute vibrational frequencies and intensities of nickel porphine and of several isotopomers via a scaled quantum mechanical [SQM] force field [FF]. The results support and extend those obtained from a revised empirical FF. The force constants are similar for…
The thermally stable second-order nonlinear optic (NLO) hybrid materials were successfully prepared by a sol−gel process using dye-attached sol−gel monomers (ormosils) of difunctionalized or trifunctionalized second-order NLO chromophores attached to silicon atoms. The dye-attached sol−gel monomers were synthesized by…
A layered double hydroxide with the hydrotalcite-like structure containing Ni(II) and Fe(III) cations in the brucite-like layers with the formula [Ni 0.7 Fe 0.3 (OH) 2 ](CO 3 ) 0.15 ·0.94 H 2 O has been prepared by coprecipitation. On hydrothermal treatment, a coproduct, identified as a NiFe 2 O 4 spinel, is formed. B…
We revisit the transport properties of La-Ca manganites in detail, since they have been confirmed in a number of CMR-exhibiting materials. We also discuss new data considered the hallmark of an unusually high electron-phonon coupling responsible for charge localization and small polaron transport.
A versatile single source thermal ablation (SSTA) technique is demonstrated, enabling the deposition of high-quality films of organic−inorganic hybrid materials. The SSTA process involves rapidly heating the organic−inorganic compound using a resistively heated sheet. The organic and inorganic components ablate from t…
Dimensionality plays a critical role in determining the properties of materials due to, for example, the different ways that electrons interact in three-dimensional, two-dimensional (2D), and one-dimensional (1D) structures.1-5
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTPreparation of Narrowly Distributed Stable and Soluble Polyacetylene Block Copolymer NanoparticlesChi Wu, Aizhen Niu, Louis M. Leung, and T. S. LamView Author Information Department of Chemistry The Chinese University of Hong Kong Shatin, N.T., Hong Kong The Open Labor…
Nanotubes of hexagonal boron nitride ( h -BN) have been synthesized by arc discharge between ZrB 2 electrodes in a nitrogen atmosphere. A new morphology of BN nanotubes at their tips, exhibiting a “triangular flag” like shape, was observed by transmission electron microscopy. This morphology suggests the presence of e…
We have studied the isothermal cold crystallization of poly(ether−ether−ketone) (PEEK) by atomic force microscopy, densitometry, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and small- and wide-angle X-ray scattering (SAXS and WAXS). A two-stage process was clearly evidenced. The first s…