Materials Literature
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Abstract The thermal behavior of various cellulose samples with different degrees of crystallinity as measured by X‐ray diffraction techniques was studied with a differential scanning calorimeter (DSC). The broad endothermic peak which appears between 110 and 160°C is due to loss of absorbed (bound) water. Since a dir…
Abstract The effects of temperature, molecular weight and its distribution, side chain branching, and the structure of polymers on the elastic behavior of bulk homopolymers were investigated, by using logarithmic plots of first normal stress difference ( N 1 ) against shear stress (σ 12 ) and logarithmic plots of stor…
We have measured the elastic constants of two series of glasses in the Ge-As-Se system. Each series consisted of samples whose compositions were chosen to produce an average atomic coordination ($〈r〉$) which ranged from 2 to nearly 3. Different local structures were produced by our making one series much higher in As…
The effect of hydrogen plasma treatment on indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and indium-doped zinc oxide (IZO) films has been studied. X-ray photoelectron spectroscopy analysis shows that ITO and FTO surfaces get reduced to yield elemental indium and tin, respectively. Annealing of the plasma tre…
The crystal structure of BaCo2FeI6027 W-type hexagonal ferrite is refined from room-temperature X-ray single crystal data. This compound is hexagonal: a = 0.59043(7) nm and c = 3.2910(7) nm, the space group is P63/mmc and the cell contains two formula units (Z = 2); the structure can be described by the sequence… RS̄S…
The fundamental optical absorption bands have been found at about 4.5 eV in the alkali cuprous halide (ACH) crystals of K 2 CuCl 3 , K 2 CuBr 3 , Rb 2 CuCl 3 , and Rb 2 CuBr 3 , and from 3.9 to 5.2 eV in Rb 2 CuI 3 . From the measured ultraviolet photoelectron spectra of the ACH's and the alkali silver halide (ASH) cr…
Nb${\mathrm{Te}}_{4}$ is a quasi-one-dimensional metallic compound. The crystal structure is tetragonal and is modulated by an incommensurate distortion wave at room temperature. We show that on the cooling of the crystal into the temperature range 100-50 K, two distinct sets of sharp spots can occur along the streaks…
Hexagonal lattice parameters a and c of the NiAs-type NiS 1- y Se y expand with increasing y below the solubility limit y L =0.20. The first-order transition temperature T t ( y ) [between the antiferromagnetic less-conductive and the Pauli-paramagnetic high-conductive states] decreases with increasing y , and is supp…
The band structure of ${\mathrm{C}}_{8}$K is investigated both experimentally and theoretically. For this purpose we have used low-energy electron-energy-loss spectroscopy (LEELS) on ${\mathrm{C}}_{8}$K and also calculated the density of states using the band structure of Ohno, Nakao, and Kamimura (ONK) and the charge…
The polarization of the x-ray-induced blue luminescence from synthetic quartz has been measured between 80 and 225 K. Two overlapping bands having different polarizations are observed; one peaks at 2.48 eV and is almost completely polarized perpendicular to the $c$ axis, while the other peaks at 2.74 eV and is polariz…
A theory is presented which explains recurrent precipitation bands (‘‘Liesegang rings’’) as dissolution patterns in a previously produced essentially homogeneous and continuous colloid. This picture is consistent with recent experimental evidence that the formation of Liesegang bands is a postnucleation phenomenon. Ma…
The temperature dependence of chromium photoluminescence spectra and lifetimes have been measured in ordered perovskite (${\mathrm{Cs}}_{2}$${\mathrm{NaYCl}}_{6}$, ${\mathrm{K}}_{2}$${\mathrm{NaScF}}_{6}$, and ${\mathrm{K}}_{2}$${\mathrm{NaGaF}}_{6}$) host crystals. Analysis of lifetime data yields thermal-quenching a…
Nematic cyanobiphenyl molecules are aligned normal to a glass electrode by a polymerized DMOAP silane coating. Under the action of a normal electric field, oriented toward the bulk nematic, a weak diffuse surface splay bend is observed, above a field threshold ∼ 0.1 V/μm. This polar instability can be attributed to th…
We have measured by spectroellipsometry the dielectric function \ensuremath{\epsilon} of pure and ultraheavily doped germanium from the near-infrared (\ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\simeq}1.6 eV) to the near-ultraviolet (\ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\simeq}5.6 eV) regions. The…
Using diagrammatic valence-bond calculations, we have investigated the interplay between neutral-ionic (N-I) and regular-dimerized stack interfaces in mixed-stack organic charge-transfer (CT) crystals. The interactions relevant to the above two interfaces, that is, the intersite Coulomb and the electron-lattice phonon…
The magnetic properties of the 4:1, 6:1, 9:1, and 19:1 mixed crystals of galvinoxyl (4-[[3,5-bis(1,1-dimethylethyl)-4-oxo-2,5-cyclohexadien-1-ylidene]methyl]-2,6 -bis(1,1-dimethylethyl) phenoxy) radical and its precursory closed shell compound, hydrogalvinoxyl, have been studied. From the measurements of the temperatu…
Ultraviolet-sensitive photodiodes have been made using the Schottky barrier formed in the contact layer between a thin sputtered layer of ZnO and Au. The sputtering parameters for the ZnO layer were optimized. The IV characteristics and the sensitivity spectra of the ZnO–Au photodiodes were investigated.
Step structure models for hydrogenated and clean Si(110) surfaces are proposed by kinematical analysis of low-energy electron diffraction patterns. The step structures are described as periodically up and down sequence of terraces with [1\ifmmode\bar\else\textasciimacron\fi{} 1\ifmmode\bar\else\textasciimacron\fi{} 2]…
The EPR data for strained ruby have been reanalyzed using a model in which the mixing of five excited multiplets into the ground state are considered. Consistent crystal-field superposition-model parameters were obtained. Tables of the necessary superposition-model ``projection'' coefficients for both trigonally and t…
We analyse the integro-differential equation giving the shape of steady dendrites growing from a weakly undercooled melt in two spatial dimensions. A generalized WKB method shows that solutions at small velocities can exist with anisotropic surface tension only, a result completely out of reach of regular perturbation…