Materials Literature
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Dielectric and dilatometric investigations of (NH2(CH3)2)2CoCl4 crystals were performed in the temperature range 290 to 430 K. Anomalies characteristic of phase transitions have been found at the temperatures 419, 380, 353, and 313 K (in a heating run). In certain phases the investigated crystal shows anomalously high…
The Al-Ni-Fe decagonal quasicrystalline phase is thermodynamically stable between about 847 and 930 °C. The features of its transformation below 847 °C into three neighboring crystalline phases (Al13(Fe, Ni)4, Al3Ni2(Fe), and Al3Ni(Fe)) are reported.
Composite films of ZnS and SiO2 were prepared by co-evaporation from two separately controlled sources. Pure ZnS films were found to consist of crystallites with mean diameter between 10 and 15 nm for films thicker than about 100 nm. The addition of SiO2 to ZnS seems to be very efficient in reducing crystallinity and…
Clear time (tcl), the time required for the turbid mixture of terephthalic acid (TPA) and ethylene glycol (EG) to be clear, was measured to examine the effect of poly(ethylene terephthalate) (PET) prepolymer (DP of 1–5) on the kinetics of dissolution and/or ester-ification of TPA with EG. The tcl of the mixture of TPA…
When isotactic polypropylene is quenched at 0°C from the molten state, a biphasic material, amorphous-smectic, is obtained. The smectic phase has an intermediate order between the amorphous and the crystalline. In this study the intrinsic birefringence of the smectic phase was determined. Tapes with different draw rat…
Sorption and diffusion of benzene and methyl-substituted benzenes were investigated through natural rubber reinforced with four types of carbon black: superbrasion furnace, intermediate superabrasion furnace, high-abrasion furnace, and semireinforcing furnace. The rubber loaded with superabrasion furnace took the lowe…
Anharmonic decay rates are calculated for a realistic atomic model of amorphous silicon. The results show that the vibrational states decay on picosecond timescales and follow the two-mode density of states, similar to crystalline silicon, but somewhat faster. Surprisingly little change occurs for localized states. Th…
Segmented polyurethanes containing soft segments with lower molecular weight exhibit shape-memorizing properties. Structure and properties of shape-memorizing polyurethanes (S-PUs) were studied. S-PUs are characterized by a rather high glass transition temperature: Tg of S-PUs is usually in the range of 10–50°C. A Ppl…
Alloys of PrCo13−xSix (1.5≤x≤4.0) have been prepared by arc melting and subsequent annealing. X-ray powder diffraction proved that the alloys crystallized in the cubic NaZn13-type structure for x=1.5, and in the tetragonal NaZn13-derivative one for x≥2.0. Their Curie temperatures are almost independent of the Si conte…
Interlayer interactions in the prototype stage-1 graphite intercalation compound ${\mathrm{LiC}}_{6}$ are probed by neutron diffraction measurements of c-axis compressibility ${\mathrm{\ensuremath{\kappa}}}_{\mathit{c}}$ at 300 K and c-axis thermal expansion ${\mathrm{\ensuremath{\alpha}}}_{\mathit{c}}$ in the interva…
We have measured experimentally and analyzed theoretically the Ti 2 p X-ray photoemission spectra (XPS) and the resonant enhancement of valence photoemission at the Ti 2 p threshold for Ti 2 O 3 . A satellite structure of the 2 p XPS is interpreted as the charge transfer (CT) satellite based on the analysis with a clu…
The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by a spherical or spheroidal island, and the temperature effects on the surface plasmon are accounted for via a slightly…
The first-principles divide-and-conquer density-functional approach has been extended to solid-state systems. The method has the following features. (1) It divides a periodic solid-state system into equivalent primitive cells and further divides each cell into subsystems. The electron density of each subsystem is dete…
The deuteration of oxygen adatoms on the Ru(001) surface has been investigated by means of temperature programmed desorption and high-resolution electron energy loss spectroscopy. Exposure of gas-phase atomic deuterium to the p(1×2) oxygen overlayer with a fractional adatom coverage of oxygen of 0.5 leads to the produ…
We made measurements of dielectric constant, pyroelectric current, magnetic susceptibility and magnetoelectric effect of single crystals of YbMn 2 O 5 . From the results, we concluded that there were two phase transitions besides antiferromagnetic transition at approximately 40 K. The first transition at 32 K is chara…
Colossal magnetoresistance (CMR) properties have been evidenced for the manganese perovskites La0.7−xYxCa0.3MnO3−δ with 0.01≤x≤0.20. This system is compared to the manganites Pr0.7Ca0.3−xSrxMnO3−δ that exhibit the same Mn(III)/Mn(IV) ratio. Like for this second system, one observes that the transition temperature T1 i…
The ground and excited state properties of the Cr3+ ion doped into the cubic host lattices Cs2NaYCl6 and Cs2NaYBr6 have been studied using density functional theory. A new symmetry based technique was employed to calculate the energies of the multiplets 4A2g, 4T2g, 2Eg, and 4T1g. The geometry of the CrX3−6 cluster was…
A systematic study of porous silicon anodic oxidation is reported. We have studied the evolution of the lattice parameter versus oxidation levels for p- and p+-type materials by using high-resolution x-ray diffraction, which gives a determination of the strains of the porous layer. The analysis of an asymmetric reflec…
Laser deposition technique has been applied to synthesize (Sr0.2Ba0.8)TiO3 thin films. The crystal structure of the films and the effect of deposition parameters on them have been systematically examined. Among the important deposition parameters, the substrate temperature and the chamber oxygen pressure affect the ch…
Small-angle x-ray scattering (SAXS) from single-phase melts and solutions of polystyrene-block-polyisoprene (SI) having various degrees of polymerization N and compositions f were analyzed on the basis of Landau-type mean-field theory developed by Leibler. The effective Flory interaction parameter χeff per segment in…