Search results for " COMPOSITES"
showing 10 items of 1620 documents
Influence of Ce codoping and H2 pre-loading on Er/Yb-doped fiber: Radiation response characterized by Confocal Micro-Luminescence
2011
International audience; Confocal microscopy luminescence measurements were applied to study the X-ray radiation response of Er/Yb-doped optical fibers in connection with H2 pre-loading and with the addition of another lanthanide element (Cerium) in the core composition. Laser excitations at 488 nm and 325 nm allow deriving the emission and absorption pattern of Er3+, the latter derived from the dips appearing in a wide luminescence band related to defects in silica. We found that the luminescence spectrum of the X-irradiated Er/Yb-doped core fiber evidences an increase in the emission intensity around 520 and 660 nm; in contrast, no changes are induced by radiation neither after H2 pre-load…
Hybrid organic-inorganic mononuclear lanthanoid single ion magnets
2019
The first family of hybrid mononuclear organic-inorganic lanthanoid complexes is reported, based on [PW11O39]7− and 1,10-phenanthroline ligands. This hybrid approach causes a dramatic improvement of the relaxation time (×1000) with a decrease of the optimal field while maintaining the Ueff of the inorganic analogues.
Extended dipyrrin ligands : candidates for optical metal ion detection under competitive conditions
2017
Acylhydrazone based extended dipyrrins L1-H and L2-H are introduced as complexometric ppb sensitive metal ion detectors. The binding of lanthanide, transition as well as post-transition metal ions is followed by UV-Vis measurements. The carbohydrate based ligand L2 is water soluble and thus can act as a metal ion sensor in this medium.
Slow magnetic relaxation in carbonato-bridged dinuclear lanthanide(iii) complexes with 2,3-quinoxalinediolate ligands
2012
The coordination chemistry of the 2,3-quinoxalinediolate ligand with different lanthanide(iii) ions in basic media in air affords a new family of carbonato-bridged M 2 III compounds (M = Pr, Gd and Dy), the Dy 2 III analogue exhibiting slow magnetic relaxation behaviour typical of single-molecule magnets. This journal is © 2012 The Royal Society of Chemistry.
Synthesis, crystal structure, optical, thermal and magnetic studies of a new organic-inorganic hybrid based on tetrachloroferrate (III)
2021
Abstract A new organic metal halide hybrid, benzyltrimethylammonium tetrachloroferrate (III), 1, ((BzMe3N)FeCl4) was synthesized by slow evaporation. The single crystal X-ray diffraction reveals that 1, crystallizes in the P-1 triclinic space group with the parameters a = 7.158 (5), b = 8.814 (8), c = 12.922 (4) A, α = 82.44 (5), β = 86.14 (4), γ = 87.13 (7)°, V = 805.7 (10) A3 and Z = 2. The structure packing exhibits a cationic and anionic layers alternation linked by means of C─H⋯Cl hydrogen interactions. The Hirshfeld surface and the lattice energy of 1 were calculated. The material purity was verified using X-ray powder diffraction and Rietveld refinements. The TG-DTA a…
Raman spectroscopic study of some lead phosphate glasses with tungsten ions
2006
Abstract The structure of x WO 3 · (100 − x )[2P 2 O 5 · PbO] glass system with 0 ⩽ x ⩽ 50 mol% was investigated by Raman spectroscopy. The characteristic bands of these glasses due to the stretching and bending vibrations were identified and analyzed by the increasing of WO 3 content. This fact allowed us to identify the specific structural units which appear in these glasses and thus to point out the network modifier role of tungsten oxide for low concentrations and its former role at high concentrations.
Comparison of numerical modelling techniques for impact investigation on a wind turbine blade
2019
Wind turbine blades are exposed to numerous impact risks throughout their lifetimes. The impact risks range from bird collisions during operation to impacts with surrounding structures at the time of transportation and installation. Impact loads on the fibre composite blades can induce several complex, simultaneously interacting and visually undetectable damage modes and have a high potential to reduce the local and global blade stiffness. An assessment of such impact-induced damages is therefore necessary and usually involves high computational costs using numerical procedures, especially when analysing large composite components. To minimise this computational expense, different numerical…
Numerical investigation of rain droplet impact on offshore wind turbine blades under different rainfall conditions: A parametric study
2020
The leading edge of a fiber composite wind turbine blade (WTB) is prone to erosion damages due to repeated rain droplet impact during its service life. Such damages are critical to the blade's aerodynamic as well as structural performance, ultimately resulting in substantial repair costs. An effective design of a coating material for WTB is necessary and its analysis must include variables associated with erosive rain droplets such as (1) droplet diameter, (2) impact velocity, and (3) droplet impact angle. The present paper develops and validates a coupled fluid structure interaction (FSI) computational model for simulating rain droplet impact on WTBs, where the structure domain is modelled…
Heterogeneity at the glass transition: what do we know?
2002
We critically discuss the information that can be obtained from experiments with respect to the existence, the life time, and the length scale of dynamical heterogeneity in glass-forming liquids. The ability to select a dynamically distinguishable subensemble and observe its return to the full equilibrium ensemble is illustrated by examples from multi-dimensional NMR. We also discuss non-resonant hole burning spectroscopy as an example for which two separate time scales are involved.
Length-scale effects in the nucleation of extended dislocations in nanocrystalline Al by molecular-dynamics simulation
2001
The nucleation of extended dislocations from the grain boundaries in nanocrystalline aluminum is studied by molecular-dynamics simulation. The length of the stacking fault connecting the two Shockley partials that form the extended dislocation, i.e., the dislocation splitting distance, rsplit, depends not only on the stacking-fault energy but also on the resolved nucleation stress. Our simulations for columnar grain microstructures with a grain diameter, d, of up to 70 nm reveal that the magnitude of rsplit relative to d represents a critical length scale controlling the low-temperature mechanical behavior of nanocrystalline materials. For rsplit>d, the first partials nucleated from the bou…