Search results for "Diffraction"
showing 10 items of 1584 documents
A study of KNbO3in the pressure range to 12 GPa using synchrotron radiation
1997
Abstract Orthorhombic KNbO3 has been studied by x-ray diffraction as a function of pressure. The lattice cell parameters, volume and stability range of this phase have been determined as a function of the applied pressure. No structural transformation has been observed up to 12 GPa. The resulting P-V data are fitted to a Murnaghan equation state of first-order.
Subwavelength surface waves with zero diffraction
2011
We identified nanostructured devices sustaining out-of-plane nondiffracting beams with near-grazing propagation and a transverse beamwidth clearly surpassing the diffraction limit of half a wavelength. This type of device consists of a planar multilayered metal-dielectric structure with a finite number of films deposited on a solid transparent substrate. We assumed that the nondiffracting beam is launched from the substrate. The construction of the subwavelength diffraction-free beam is attended by plane waves which are resonantly transmitted through the stratified medium. Therefore, light confinement and wave amplification occurs simultaneously. We performed an optimization process concern…
High-energy X-ray diffraction and topography investigation of CdZnTe
2005
High-energy transmission x-ray diffraction techniques have been applied to investigate the crystal quality of CdZnTe (CZT). CdZnTe has shown excellent performance in hard x-ray and gamma detection; unfortunately, bulk nonuniformities still limit spectroscopic properties of CZT detectors. Collimated high-energy x-rays, produced by a superconducting wiggler at the National Synchrotron Light Source’s X17B1 beamline, allow for a nondestructive characterization of thick CZT samples (2–3 mm). In order to have complete information about the defect distribution and strains in the crystals, two series of experiments have been performed. First, a monochromatic 67 keV x-ray beam with the size of 300×3…
Pressure-induced transition in titanium metal: a systematic study of the effects of uniaxial stress
2005
Abstract The effects of uniaxial stress on the pressure-induced α → ω transition in pure titanium (Ti) are investigated by means of angle dispersive X-ray diffraction in a diamond-anvil cell. Experiments under four different pressure environments reveal that: (1) the onset of the transition depends on the pressure medium used, going from 4.9 GPa (no pressure medium) to 10.5 GPa (argon pressure medium); (2) the α and ω phases coexist over a rather large pressure range, which depends on the pressure medium employed; (3) the hysteresis and quenchability of the ω phase is affected by differences in the sample pressure environment; and (4) a short-term laser heating of Ti lowers the α → ω transi…
XAFS analysis of the low symmetry octahedral molybdenum and tungsten oxides
1995
Abstract Comparative XAFS analysis of the main isostructural crystalline phases of W(Mo)O3 oxides and W(Mo)O3·nH2O hydrates has been done at the W L3 and Mo K edges. These compounds have (1) 3D perovskite-type (PT) structure (m-WO3); (2) 2D PT structure (WO3·H2O and MoO3·nH2O (n = 1,2)); (3) 2D hexagonal-type structure (WO3·1/3H2O) and (4) 2D double layered structure (α-MoO3). The detailed analysis of X-ray absorption fine structure (XAFS) in the low-symmetry structures shows that in order to simulate the experimental spectrum, it is sufficient to take into account single-scattering contributions in the range from 1.7 to ∼ 5.0 A and a number of multiple-scattering paths from nearly linear a…
Apoferritin-encapsulated Ni and Co superparamagnetic nanoparticles
2006
Ni and Co nanoparticles (average diameters 3 and 3.5 nm) have been prepared within the apoferritin cavity. The protein shell prevents bulk aggregation of the metal particles, rendering them water soluble. X-Ray diffraction, transmission electronic microscopy and magnetization measurements have been used for characterizing the nanoparticles. The magnetic study of both nanoparticles confirmed the expected superparamagnetic behavior.
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.
Water vapor sensors based on the swelling of relief gelatin gratings
2015
We report on a novel device to measure relative humidity. The sensor is based on surface diffraction gratings made of gelatin. This material swells and shrinks according to the content of water vapor in air. By sending a light beam to the grating, diffracted orders appear. Due to the gelatin swelling or shrinking, first order intensity changes according to the relative humidity. Calibration curves relating intensity versus relative humidity have been found. The fabrication process of diffraction gratings and the testing of the prototype sensing devices are described.
Water Vapor Sensors Based on the Swelling of Relief Gelatin Gratings: Recent Advances and Development
2021
We report on a novel device to measure relative humidity. Materials used in the measurement of relative humidity are of different kinds. The sensor is based on surface diffraction gratings made of gelatin. This material swells and shrinks according to the content of water vapor in air. By sending a light beam to the grating, diffracted orders appear. Due to the gelatin swelling or shrinking, first order intensity changes according to the relative humidity. Calibration curves relating intensity versus relative humidity have been found. The fabrication process of diffraction gratings and the testing of the prototype sensing devices are described.
Dihypoiodites stabilised by 4-ethylpyridine through O–I–N halogen bonds
2021
Four bis(O–I–N) compounds have been synthesised from various dihypoiodites and 4-ethylpyridine. The compounds were characterised in both the solution and solid states by NMR spectroscopy (1H, 15N), X-ray diffraction, and computational calculations. peerReviewed