Search results for "NANOCRYSTALLINE"

Mechanically Activated SHS Reaction in the Fe-Al System: In Situ Time Resolved Diffraction Using Synchrotron Radiation

1998

The Mechanical Activation Self propagating High temperature Synthesis (M.A.S.H.S.) processing is a new way to produce nanocrystalline iron aluminide intermetallic compounds. This process is maily the combination of two steps ; in the one hand, a mechanical activation where the Fe - Al powder mixture was milled during a short time at given energy and frequency of shocks and in the other hand, a Self propagating High temperature Synthesis (S.H.S.) reaction, for which the exothermicity of the Fe + Al reaction is used. This fast propagated MASHS reaction has been in -situ investigated using the Time Resolved X - Ray Diffraction (TRXRD) using a X - ray synchrotron beam and an infrared thermograp…

Preparation and Characterization of Tin Tungstate Thin Films

2015

Tin tungstate thin films were prepared by dc magnetron sputtering method and studied by x-ray diffraction, confocal microscopy and Raman spectroscopy. It is shown that the films are composed mainly of nanocrystalline α-SnWO4 phase. The possibility to use these films as write-once optical recording media is demonstrated.

New zeolite-like RUB-5 and its related hydrous layer silicate RUB-6 structurally characterized by electron microscopy.

2020

RUB-5 and its related hydrous layer silicate RUB-6 were synthesized in the 1990s, but so far their structures have remained unknown due to their low crystallinity and disorder. The combination of 3D electron diffraction, X-ray powder diffraction, high-resolution transmission electron microscopy, structural modelling and diffraction simulations has enabled a comprehensive description of these two nanomaterials, revealng a new framework topology and a unique silica polymorph.

Template-based synthesis of nickel oxide

2015

Nanocrystalline NiO has been produced using a facile template-based synthesis from nickel nitrate solutions using cellulose as a template. Thus obtained oxides were studied by scanning electron microscopy, x-ray diffraction, Raman scattering spectroscopy, photoluminescence spectroscopy and confocal spectromicroscopy. The filamentary/coral morphology of the samples has been evidenced and is built up of agglomerated nanocrystallites with a size in the range of about 26-36 nm. The presence of two-magnon contribution in Raman scattering spectra suggests the existence of antiferromagnetic ordering at room temperature. Finally, the observed near-infrared photoluminescence band at 850 nm has been …

Ab Initio Structure Determination of Vaterite by Automated Electron Diffraction

2012

tion that is fundamental for understanding material properties. Still, a number of compounds have eluded such kinds of analysis because they are nanocrystalline, highly disordered, with strong pseudosymmetries or available only in small amounts in polyphasic or polymorphic systems. These materials are crystallographically intractable with conventional Xray or synchrotron radiation diffraction techniques. Single nanoparticles can be visualized by high-resolution transmission electron microscopy (HR-TEM) up to sub�ngstrom resolution, [2] but obtaining 3D information is still a difficult task, especially for highly beam-sensitive materials and crystal structures with long cell parameters. Elec…

Applications of automated diffraction tomography (ADT) on nanocrystalline porous materials

2013

Abstract Many porous materials, both inorganic and hybrid organic–inorganic, can only be synthesized as nanocrystals. X-ray powder diffraction delivers one-dimensional data from the overall sample and is therefore often limited by peak overlap at low or medium resolution and by peak broadening. Thus, structure solution of materials with large unit cells and low symmetry, disorder or pseudosymmetry, or available only in polyphasic systems, turns out to be problematic or even impossible. Electron diffraction allows collecting three-dimensional structure information from nanocrystalline materials, but is traditionally biased by low completeness of the diffraction data, dynamical scattering and…

Transient absorption studies of the Ru(dcbpy)2(NCS)2 excited state and the dye cation on nanocrystalline TiO2 film

2001

We have measured dynamics of the Ru(dcbpy)2(NCS)2 [dcbpy = 4,4′-dicarboxy-2,2′-bipyridine] excited state and the dye cation on nanocrystalline TiO2 film in the wavelength region 700–900 nm. The dye in ethanol solution and Ru(dcbpy)2(NCS)2 sensitized nanocrystalline Al2O3 films were used as non-injecting reference samples for excited state identification. For TiO2/Ru(dcbpy)2(NCS)2 film the `reactant' decay and `product' formation kinetics observed at different probe wavelengths showed that the resolved transient absorption picosecond components (1.1±0.2), (12±2) and (100±5) ps are related to electron injection from the excited states of the dye to the semiconductor TiO2.

Supermolecular control of charge transfer in dye-sensitized nanocrystalline TiO2 films: towards a quantitative structure-function relationship.

2005

Sensitization of nanocrystalline TiO2 with 3,4,9,10-perylene tetracarboxylic acid

2014

Optical properties of 3,4,9,10-perylene tetracarboxylic acid (PTCA) in the presence of nanocrystalline TiO2 (nominal diameter 15 nm) have been investigated in ethanol solution and in the solid state by UV-Vis absorption spectroscopy and steady-state and time-resolved fluorescence. Experimental results show that, in ethanol, the presence of TiO2 nanoparticles causes significant changes in the typical absorption and fluorescence bands of PTCA and in the fluorescence relaxation time. Similar effects are also detected in solid samples, obtained by electrospray deposition technique. The nonlinear optical properties of the PTCA-TiO2 in ethanol solutions were investigated using the single-beam Z-s…

Structure and composition heterogeneity of a FeAl alloy prepared by one-step synthesis and consolidation processing and their influence on grain size…

2006

Abstract This paper aims to characterize a bulk dense FeAl (47 at.%) alloy synthesized and consolidated by one-step current-activated pressure-assisted processing of nanocrystalline elemental powders. The end-product was analyzed using a combination of scanning (SEM) and transmission electron microscopies (TEM), electron back-scattering diffraction (EBSD) as well as electron probe microanalysis (EPMA). Special attention was paid to verify the grain size (32–89 nm) previously determined by X-ray diffraction peak profile analysis. It has been found that this material displays equiaxed grains (0.8–4 μm in size) and contains limited structural defects like subgrains and dislocations. The EPMA r…