Structural modifications in stretch-induced crystallization in PVDF films as measured by small-angle X-ray scattering

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A thermoporometry and small-angle x-ray scattering study of wet silica sonogels as the pore volume fraction is varied

Silica sonogels with different porosities were prepared by acid sono-hydrolysis of tetraethoxysilane. Wet sonogels were studied using small-angle x-ray scattering (SAXS) and differential scanning calorimetry (DSC). The DSC shows a broad thermal peak below the normal water melting point associated with the melting of confined ice nanocrystals, or nanoporosity. The nanopore size distribution was determined from the Gibbs-Thomson equation. As the porosity is increased, a second sharp DSC thermal peak with onset temperature at the water melting point is apparent, which was associated with the melting of ice macrocrystals, or macroporosity. The DSC result could be causing misinterpretation of the macroporosity because water may not be exactly confined in very feeble silica network regions in sonogels with high porosity. The structure of the wet gels can be described fairly well as mutually self-similar mass fractal structures with characteristic length. increasing from similar to 1.8 to similar to 5.4 nm and mass fractal dimension D diminishing discretely from similar to 2.6 to similar to 2.3 as the porosity increases in the range studied. More specifically, such a structure could be described using a two-parameter correlation function gamma(r) similar to r(D-3) exp(-r/xi), which is limited at larger scale by the cut-off distance xi but without a well-defined small scale cut-off distance, at least up to the maximum angular domain probed using SAXS in the present study.

Intense blue and green photoluminescence emissions at room temperature in barium zirconate powders

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Morphology and Blue Photoluminescence Emission of PbMoO4 Processed in Conventional Hydrothermal

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ferroelectric fatigue endurance of Bi4-xLaxTi3O12 thin films explained in terms of x-ray photoelectron spectroscopy

The nature of defects in polycrystalline Bi4-xLaxTi3O12 (BLT) thin films with x=0.00, 0.25, 0.50, and 0.75 was evaluated by x-ray photoemission spectroscopy measurements. The influence of oxygen vacancies and substitution of Bi for La atoms were discussed. In the BLT thin films, it was found that the oxygen ions at the metal-oxygen octahedral were much more stable than those at the [Bi2O2] layers. on the other hand, for Bi4Ti3O12 (BIT) thin film, oxygen vacancies could be induced both at the titanium-oxygen octahedral and at the [Bi2O2] layers. The oxygen-vacancy defect pairs determined in BIT and Bi3.75La0.25Ti3O12 (BLT025) can pin the polarization of surrounding lattices leading to fatigue of capacitors. Meanwhile, the concentration of similar defect pairs is relatively low in heavily doped BIT films and then good fatigue resistance is observed.

X-ray diffraction and mossbauer spectra of nickel ferrite prepared by combustion reaction

Nickel ferrite powders with a nominal NiFe2O4 composition were synthesized by combustion reaction using urea as fuel. The powder was obtained using a vitreous silica basin heated directly on a hot plate at 480 degrees C until self-ignition occurred. After combustion, the powder was calcined at 700 degrees C for 2 h. The formation of the spinel phase and the distribution of cations in the tetrahedral and octahedral sites of the crystal structure were investigated by the Rietveld method, using synchrotron X-ray diffraction data and Mossbauer spectroscopy. The material presented a crystallite size of 120 nm and magnetic properties. The resulting stoichiometry after the Rietveld refinement was (Fe-0.989(2) Ni-0.011(2)) [Fe-1.012(2) Ni-0.989(2)] O-4.

Voltage-composition profile and synchrotron X-ray structural analysis of low and high temperature LixCoO2 host material

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synchrotron X-ray powder diffraction data of atorvastatin

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crystal Structure Determination of Mebendazole Form A Using High-Resolution Synchrotron X-Ray Powder Diffraction Data

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The interaction between atoms of Au and Cu with clean Si(111) surface: A study combining synchrotron radiation grazing incidence X-ray fluorescence analysis and theoretical calculations

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

X-ray diffraction data of tibolone Delta(4) isomer (isotibolone)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crystal structure of propylthiouracil determined using high-resolution synchrotron X-ray powder diffraction

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Powder X-ray characterization of lithium thiazoildine-4-carboxylate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural investigations of tungsten silver phosphate glasses by solid state NMR, vibrational and X-ray absorption near edge spectroscopies

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electronic structure, growth mechanism and photoluminescence of CaWO4 crystals

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)