Materials Literature
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The pyrolytic transformation of hybrid gels, obtained by hydrolysis−condensation of diethoxydimethylsilane and zirconium n -propoxide mixtures with different Si/Zr ratio, has been studied using TG−GC−MS coupled techniques, FTIR spectroscopy, and N 2 adsorption analysis. The starting gels have been described as nanocom…
Conformation of a flexible linear polymer (polyacrylic acid, PAA) in a binary mixture ( $\mathrm{water}+2$,6-lutidine, LW) near the critical point of LW is studied using dynamic light scattering (DLS) by which the diffusivities of the polymer molecules and the critical composition fluctuation of the LW are measured. T…
A self-regulation hydrothermal reaction to synthesize nanocrystalline zinc gallate (ZnGa2O4) complex oxides was proposed: The Zn2+ ion concentration and the pH value of the solution and the nucleation and growth of ZnGa2O4 were well auto-controlled under these simple hydrothermal conditions.
A series of nondiscoid rhodium and iridium dicarbonyl β-diketonate complexes have been shown to organize in columnar liquid crystal phases with hexagonal disordered structures (Col hd ). The shape and dipolar attributes of these materials produce highly correlated antiparallel pairwise arrangements. This organization…
Neutron diffraction has been used to determine the two P-O bond lengths which occur in the threefold-linked tetrahedral structural units of vitreous . The large maximum momentum transfer which is available on the LAD instrument at the ISIS spallation neutron source gives high real-space resolution which enables a clea…
Using a “two-steps” synthesis mode, the homogeneity ranges of the perovskites Ln 1 - x Ba x MnO 3 were extended up to x = 0.60 for the Pr-based samples and x = 0.50 for the La ones. Two new perovskites, a cubic form and a P-type tetragonal phase (with a C × a C × 2 a C parameters) have been isolated. The HREM study sh…
Intense ultraviolet photoluminescence centered at 370 nm was observed from magnetron-sputtered silicon oxide films after they were annealed at about 1000 °C in N2 atmosphere. This photoluminescence is found to be associated with the formation of nanocrystal silicon particles in the specially structured SiO2, which hig…
Silica/surfactant mesophases have been synthesized in 14 water:cosolvent mixtures by combining tetramethoxysilane with a basic 2 wt % CTAB solution. The effects of the water-to-cosolvent ratio on the formation of supramolecular surfactant templates and ultimately silica/surfactant mesophases is reported for: diethyl e…
Polycrystalline diamond films have been found to display p-type surface conductivity. No bulk impurity is added to the films; the p-type characteristics of the undoped diamond are thought to be due to a surface or near surface hydrogenated layer. Carrier concentrations within the range 1017–1019 cm−3 have been measure…
We present structural and magnetic properties of epitaxial Sm–Co/Co superlattice films prepared via magnetron sputtering. X-ray diffraction and cross-sectional transmission electron microscopy show that the films are structurally coherent. The oriented nature of the interleaved ferromagnetically “hard” and “soft” laye…
A saturation voltage method is described for determining the unified surface-anchoring energy, which has been proposed theoretically by Sugimura and co-workers [Phys. Rev. E, 52, 681 (1995)], at the interface of nematic (4-pentyl-4′-cyanobiphenyl) and its alignment layer (polyvinyl cinnamate). The method proposed can…
Ferroelectric lead lanthanum titanate (PLT) thin films with various lanthanum concentration were fabricated by sol-gel spin-on process onto Pt/Ti/SiO2/Si substrates. We investigated the crystal structure, microstructure, and dielectric and ferroelectric properties of PLT films according to lanthanum doping concentrati…
Time-resolved in situ energy-dispersive X-ray diffraction studies on the intercalation of dicarboxylate anions (Na 2 C 4 H 4 O 4, Na 2 C 6 H 8 O 4, Na 2 - trans -C 4 H 2 O 4, Na 2 - cis -C 4 H 2 O 4, Na 2 - l -C 4 H 4 O 5, Na 2 -1,2-C 8 H 4 O 4, Na 2 -1,4-C 8 H 4 O 4 ) into [LiAl 2 (OH) 6 ]Cl·H 2 O have revealed the r…
The colloidal synthesis of ZnO−WO 3 heteroaggregates composed of 3−5 nm particles is presented. These sols can be used to prepare nanocrystalline ZnWO 4 xerogels, powders, and thin films with strong blue fluorescence (quantum yield between 25 and 50% at room temperature). The conversion of the precursor aggregates int…
HRTEM image of a single Ge nanocrystal. The image has been rotationally filtered to improve clarity. The lattice fringes imaged are for Ge 〈111〉, with a d spacing of 3.27 Å. Reaction between the Zintl salt NaGe and GeCl4 is shown to produce Ge nanocrystals. The reaction proceeds readily in refluxing diglyme at ambient…
Hydrothermal treatment of elemental indium and sulfur in the presence of the organic structure directing agent dimethylamine yields the novel open framework material DMA-InS-SB1. This material contains [In10S20]10- supertetrahedra that corner link to form an interpenetrating “double-diamond” lattice.
The origin of the first-sharp diffraction peak (FSDP) in supercooled liquid ${\mathrm{ZnCl}}_{2}$ (a network-forming, intermediate strength fluid) is studied by computer simulation. Measures are introduced to characterize voids in the spatial distribution of cations and the existence of transient layered structures an…
A strong enhancement of the 1.54 μm fluorescence of Er 3+ has been achieved in highly concentrated II−VI semiconductor quantum dot environments. A new preparation strategy allowed to incorporate up to 20 at. % Er 3+ into ZnS, CdS, and CdSe as well as ZnO semiconductor clusters and nanocrystals (sizes 1.5−5 nm). All cl…
A detailed analysis of polarization reversal in ferroelectrics has been performed, in the framework of the Landau model for phase transitions. Some important characteristics of homogeneous switching have been emphasized and later used in studying the more general case of inhomogeneous switching. The two extremes of sw…
Details of the synthesis and structural and physical characterization of oxides with the nominal composition NaTiO 2 are presented. The highest sodium loading we have achieved is Na 0.99(2) TiO 2 determined using diffraction methods. The results are not consistent with a localized moment d 1 system. High-resolution ne…