Search results for "ALLOYS"
showing 10 items of 1689 documents
Mechanism of photoluminescence in intrinsically disordered CaZrO3 crystals: First principles modeling of the excited electronic states
2017
Abstract CaZrO3 (CZO) powders obtained by the polymeric precursor method at 400 °C, and then, the samples were annealed at different temperatures (400, 600, 800, and 1000 °C) and characterized by X-ray diffraction, Raman and ultraviolet–visible spectroscopic methods, along with photoluminescence (PL) emissions. First principle calculations based on the density functional theory (DFT), using a periodic cell models, provide a theoretical framework for understanding the PL spectra based on the localization and characterization of the ground and electronic excited states. Fundamental (singlet, s ) and excited (singlet, s* , and triplet, t* ) electronic states were localized and characterized us…
Surface plasmon assisted thermal coupling of multiple photon energies
2006
A novel optical effect can be observed in a thin gold foil due to the excitation of surface plasmons which permits a form of all-optical modulation at low pulse rates. Modulated excitation of surface plasmons by infrared photons is shown to couple to several beams at visible-photon energies. The coupling is manifested by the observation of the visible photons being pulsed by the action of the infrared pulses, and by the far field diffraction of the visible beams into concentric rings. When each visible beam also excites surface plasmons, then a quadratic dependence of the visible photon power upon the infrared incident power is measured. The decay of surface plasmons is implicated as the pr…
Vapor growth of Hg1−xCdxI2 on glass using CdTe buffer
2001
Abstract Vapor phase epitaxy (VPE) of Hg1−xCdxI2 layers on glass substrates covered by a CdTe buffer layer has been studied. The buffer layers of 2–4 μm thickness were formed by VPE using polycrystalline CdTe and Cd metal sources. The Hg1−xCdxI2 layers were grown using a (Hg1−yCdy)1−z(I2)z polycrystalline source, with a composition in the range of y=0.1–0.5 and z=0.5–0.8. Scanning electron microscopy and X-ray diffraction studies have shown that the composition and structure of Hg1−xCdxI2 layers depend strongly on the VPE conditions. Varying the growth time and source composition, it has been possible to obtain Hg1−xCdxI2 layers with the composition x in the range from approximately 0 (HgI2…
An X-ray scattering study of lipid monolayers at the air-water interface and on solid supports
1988
Abstract Monolayers of the lipid arachidic acid (C20) and of the phospholid dimyristolyphosphatidic acid (PMDA) have been studied by X-ray reflection and diffraction technique, using a purpose-built Langmuir trough installed at the sample stage of our high-resolution X-ray diffractometer at the DORIS synchroton X-ray source in Hamburg. For comparison we also report data for monolayers of C20 on a solid support using a 10 kW rotating anode X-ray source. By the X-ray reflection method, the density profile across the interface is probe, while in-plane diffraction measurements gauge the two-dimensional crystalline properties of the monolayers. Flourescence microscopy experiments of DMPA monolay…
Structural and elastic properties of defect chalcopyrite HgGa2S4 under high pressure
2014
In this work, we focus on the study of the structural and elastic properties of mercury digallium sulfide (HgGa2S4) at high pressures. This compound belongs to the family of AB(2)X(4) ordered-vacancy compounds and exhibits a tetragonal defect chalcopyrite structure. X-ray diffraction measurements at room temperature have been performed under compression up to 15.1 GPa in a diamond anvil cell. Our measurements have been complemented and compared with ab initio total energy calculations. The axial compressibility and the equation of state of the low-pressure phase of HgGa2S4 have been experimentally and theoretically determined and compared to other related ordered-vacancy compounds. The pres…
Study of plastic deformation modes in zirconium by color image analysis
2004
Abstract Twinning, as a deformation mode, is a complement to slip. This paper deals with the study from a qualitative point of view, as well as from a quantitative one. Besides techniques widely used in materials science studies such as electron backscattered diffraction (EBSD) or X-ray diffraction (XRD), colour image analysis technique are presented here. Its results manage to confirm or complete the ones obtained, thanks to others methods.
Digital signal processing for rail monitoring by means of ultrasonic guided waves
2007
Recent train accidents have reaffirmed the need for developing rail defect detection systems that are more effective than those used today. One of the recent developments in rail inspection is the use of ultrasonic guided waves (UGWs) and non-contact probing techniques to target transverse-type defects. Besides the obvious advantages of non-contact probing, that include robustness and a potential for large inspection speed, such a system can theoretically detect transverse defects under horizontal shelling or head checks. This paper demonstrates the effectiveness of digital signal processing to enhance the damage detection sensitivity of the non-contact system. The method proposed here comb…
Targeted steel frames by means of innovative moment resisting connections
2021
Abstract The present paper proposes the use of stepped cross section devices on steel frames aiming at reproducing a pre-established target push-over curve. To this aim a Limited Resistance Plastic Device (LRPD) to be inserted along selected structural members is proposed. The following two main specific features for LRPD are required: any elastic flexural stiffness variation of the original selected member must be avoided; an ultimate plastic bending moment value equal to an assigned percentage of the original limit resistance value must be ensured. Steel frames equipped with LRPD are modeled by means of an extension of a recently proposed Fibre Smart Displacement Based (FSDB) beam element…
Pd nanoparticles immobilized on the poly-dopamine decorated halloysite nanotubes hybridized with N-doped porous carbon monolayer: A versatile catalys…
2020
A hybrid catalyst, Pd@Hal-pDA-NPC, with the utility for promoting both C–C coupling reactions (Sonogashira, Heck and Suzuki reactions) and hydrogenation of nitrocompounds is prepared through two main steps. First, Pd(0) nanoparticles was immobilized on the poly-dopamine decorated halloysite nanotubes (Hal-pDA) and then Pd@Hal-pDA was hybridized with the layers of a novel multi-N-doped porous carbon monolayer derived from 4,4′,4″-((1,3,5-triazine-2,4,6-triyl)tris(azanediyl))tribenzonitrile. The results established that the catalyst could catalyze all the reactions efficiently under mild reaction condition. Moreover Pd@Hal-pDA-NPC exhibited high recyclability (up to ten reac…