Materials Literature
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Excitation spectra of visible luminescence in CsF (2.5-5.6 eV), CsCl (3.9-6.0 eV), CsBr (4.4-6.2 eV), and RbF (2.6-6.2 eV) have been measured at room temperature with use of synchrotron radiation for the energy range up to 40 eV. It is shown that the excitation thresholds of these luminescence bands are located at the…
The electrical conductivity and differential thermal analysis (DTA) characteristics of RECoO 3 (RE=La, Nd, Gd, Ho, Y) have been reexamined. In general, the data are quite different from those previously reported. In particular, first-order semiconductor-to-metal transitions of YCoO 3 , LaCoO 3 and HoCoO 3 are not obse…
There is no fundamental reason that fluids should not be ferroelectric. However, the only knownferroelectric fluids are chiral smectic-$C$ liquid crystals and related structures. We examine the possibility that molecules with permanent dipole moments can form a ferroelectric nematic phase, the least ordered conceivabl…
We have simulated the cooling of Lennard-Jones fluids from liquid temperatures to below the glass transition by using molecular-dynamics calculations and periodic boundary conditions. At higher temperatures the "inherent" structure is independent of temperature, but slightly above the glass transition temperature ${T}…
Introduction It has long been appreciated that advances in solid state science depend critically on the availability of single crystal specimens. As a result, an enormous amount of labor and care has been lavished on the development of growth techniques. In terms of crystal size, purity, and perfection, the achievemen…
We prepared highly crystalline, low-silica X zeolite (LSX) in a self-bound form directly from porous, preformed metakaolin pellets. In the appropriate cation form, these materials should have Improved adsorption properties for weakly Interacting adsorbates such as nitrogen. The composition of the synthesis medium, sub…
Laser emission has been observed in a samarium3+-doped silica optical fibre in a Fabry-Perot-type laser cavity. The emission is centred on 651 nm and corresponds to stimulated transitions from the 4G5/2 level to the 6H9/2 level. The fluorescence and absorption associated with the metastable level are seen to be unusua…
A field effect transistor has been fabricated with organic semiconductors: scandium diphthalocyanine and nickel phthalocyanine. The electrical characteristics are studied in air atmosphere. The influence of the diphthalocyanine film thickness has been detected.
A microdomain structure was found in the alloy ${\mathrm{V}}_{41}$${\mathrm{Ni}}_{36}$${\mathrm{Si}}_{23}$ after rapid solidification. It behaves like a structural constituent giving electron diffraction patterns similar to those from a decagonal quasicrystal though its high-resolution electron microscopic image shows…
High-resolution x-ray scattering measurements have revealed a second critical length scale at the cubic-to-tetragonal transition in SrTi${\mathrm{O}}_{3}$, corresponding to very large correlation lengths of the order of 2500 \AA{} at ${T}_{c}+1$ K. The correlation length becomes substantially larger still after the sa…
The dielectric function $\ensuremath{\epsilon}(\mathbf{q},\ensuremath{\omega})$ of Li-intercalated graphite (Li${\mathrm{C}}_{6}$) with $\mathbf{q}\ensuremath{\parallel}c$ axis was deduced from inelastic x-ray scattering data and compared with $\ensuremath{\epsilon}(\mathbf{q},\ensuremath{\omega})$ of pristine graphit…
Abstract Postcrosslinking of such linear polyesters as poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) are known to be attractive means to improve their thermal resistances without sacrificing their melt processibilities. Effective melt‐blend‐type ultraviolet‐induced crosslinking agents were…
Abstract A polytheylene composite was prepared and tested. It was consisted of a high‐density polyethylene (HDPE) matrix and uniaxial gel‐spun high‐modulus PE fiber. Aided by the similarity between matrix and fiber, transcrystallization of HDPE melt on the PE fiber surface was generated. Nucleating agents were not emp…
Abstract A new class of high performance engineering resins, poly(aryl ether ketone)s, has emerged with a property balance not offered by existing polymeric materials. Blends of poly(aryl ether ketone)s with other polymers have not been described in the open literature, although several patents have revealed interesti…
Abstract The oxygen index test is a fundamental tool in basic research on polymer combustion and on mechanisms of fire retardance. Although the oxygen index should provide an evaluation of intrinsic flammability of polymeric materials, its response may depend on geometry of the specimen. This is shown by comparing the…
The temperature dependence of the yield-stress of mono- and poly-crystalline α-brasses containing 5 to 35 at% zinc in the range 4 to 300 K is analysed in terms of the kink-pair model of solid-solution hardening. The parameter W0 in the theoretical relation τ = τo exp (–mkT/W0), where m is a constant equal to about 25,…
The scattering of conduction electrons at grain boundaries in polycrystalline copper, molybdenum, and iron is studied. Linear functions of the specific electrical resistance versus concentration of grain boundaries are determined. Coefficients of conduction electron scattering kGB at grain boundaries as well as the sp…
The effect of crystallite sizes L smaller than 100 nm on the integrated Raman cross section Σc of the transverse optical (TO) mode of fcc silicon was studied experimentally in fully nanocrystallized thin films. The Σc/Σa (amorphous) ratio of this mode is shown to be 1 up to L=30 Å, and to decay exponentially down to 0…
Sr 2 Sb 2 O 7 cristallise dans Imma avec a=7,4557, b=10,3708 et c=7,6860 A, Z=4; affinement jusqu'a R=3,48%
We measured, via LIF, time-dependent concentrations of OH resulting from the reaction of O(3 P) with B2H6 and C2H6. The oxygen atoms were generated by titrating microwave discharged N2 /He with NO to the chemiluminescent end point. The operating pressures in the flow reactor ranged from 5 to 15 Torr; the mixtures cons…