Search results for "FFR"
showing 10 items of 1798 documents
Influence of Lithium Substitution on Structure, Electric and Pyroelectric Properties of Sodium Niobate Ceramics
2012
Li0.02Na0.98NbO3 ceramics were prepared by a conventional method. A single-phase perovskite structure was identified by an X-ray diffraction method. The SEM and EDS studies revealed that the Li0.02Na0.98NbO3 samples were perfectly sintered and chemically homogeneous. Electric measurements showed that Li0.02Na0.98NbO3 was sensitive to the frequency of the applied electric field and revealed that the ac conductivity changed with frequency according to the formula: σ(ω) = σdc +Aωn where n < 1. These results were discussed with a reference to the conduction mechanism as a type of polaron hopping.
A comparative study of heterostructured CuO/CuWO4 nanowires and thin films
2017
Authors are grateful to Reinis Ignatans for XRD measurements.
Mechanical and structural characterizations of gamma- and alpha-alumina nanofibers
2015
Abstract We investigate the applicability of alumina nanofibers as a potential reinforcement material in ceramic matrix compounds by comparing the mechanical properties of individual nanofibers before and after annealing at 1400 °C. Mechanical testing is performed inside a scanning electron microscope (SEM), which enables observation in real time of the deformation and fracture of the fibers under loading, thereby providing a close-up inspection of the freshly fractured area in vacuum. Improvement of both the Young's modulus and the breaking strength for annealed nanofibers is demonstrated. Mechanical testing is supplemented with the structural characterization of the fibers before and afte…
A multi-technique, micrometer- to atomic-scale description of a synthetic analogue of chukanovite, Fe-2(CO3)(OH)(2)
2014
International audience; A synthetic analogue of chukanovite Fe-2(CO3)(OH)(2) is formed during experimental work on iron-clay interactions simulating the cooling of containers in radioactive waste repositories. Despite its small size and the mixture with other minerals it is undoubtedly identified by X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy and Transmission Electron Microscopy. For the first time, the structural characterisation of a synthetic chukanovite is carried out thanks to the combination of Automated Diffraction Tomography and Precession Electron Diffraction. Refinement results and comparison with literature data show that the structure…
RF magnetron-sputtered coatings deposited from biphasic calcium phosphate targets for biomedical implant applications
2017
Bioactive calcium phosphate coatings were deposited by radio-frequency magnetron sputtering from biphasic targets of hydroxyapatite and tricalcium phosphate, sintered at different mass % ratios. According to Raman scattering and X-ray diffraction data, the deposited hydroxyapatite coatings have a disordered structure. High-temperature treatment of the coatings in air leads to a transformation of the quasi-amorphous structure into a crystalline one. A correlation has been observed between the increase in the Ca content in the coatings and a subsequent decrease in Ca in the biphasic targets after a series of deposition processes. It was proposed that the addition of tricalcium phosphate to th…
Shaping graphene with optical forging: from a single blister to complex 3D structures
2020
Properties of graphene, such as electrical conduction and rigidity can be tuned by introducing local strain or defects into its lattice. We used optical forging, a direct laser writing method, under an inert gas atmosphere, to produce complex 3D patterns of single layer graphene. We observed bulging of graphene out of the plane due to defect induced lattice expansion. By applying low peak fluences, we obtained a 3D-shaped graphene surface without either ablating it or deforming the underlying Si/SiO2 substrate. We used micromachining theory to estimate the single-pulse modification threshold fluence of graphene, which was 8.3 mJ cm−2, being an order of magnitude lower than the threshold for…
Single-Crystal X-Ray Diffraction Study of Pressure and Temperature-Induced Spin Trapping in a Bistable Iron(II) Hofmann Framework.
2020
High-pressure single-crystal X-ray diffraction has been used to trap both the low-spin (LS) and high-spin (HS) states of the iron(II) Hofmann spin crossover framework, [FeII (pdm)(H2 O)[Ag(CN)2 ]2 ⋅H2 O, under identical experimental conditions, allowing the structural changes arising from the spin-transition to be deconvoluted from previously reported thermal effects.
Relative proportions of rutile and pseudo-brookite phases in the Fe(III)-TiO2 system at elevated temperature
1997
Abstract The Fe(III)-TiO2 system has been studied at T ≥ 1023 K in the range of concentration 2–10 at.% of iron by powder X-ray diffraction, transmission and scanning electron microscopy, and optical microscopy. The relationship between the relative proportions of the TiO2 rutile phase and the pseudo-brookite phase Fe2TiO5, has been investigated in powder samples. Single crystals of pure rutile and rutile doped with 0.5 at.% of iron have been examined to elucidate the microstructures found in the powders. The results suggest that a low degree of solid solubility exists and that doped crystals contain planar faults on 101 planes.
Zinc Chalcogenide Seed-Mediated Synthesis of CdSe Nanocrystals: Nails, Chesses and Tetrahedrons
2015
Systematically shape-controlled synthesis of colloidal semiconductor nanocrystals (NCs) has attracted increasing attention recently for both fundamental and technological interest. The study on the synthesis of colloidal CdSe NCs has given rise to well-developed methods for producing diverse shapes such as rods, wires, cubs and discs. In the current study, we demonstrate the shape evolution of CdSe NCs by using a seed-mediated approach by control reaction temperature and injection methods. The synthesis utilizes small (2.0–3.0 nm) zinc chalcogenide NCs with zincblende structure as seeds for subsequent growth, which results in distinct shapes of nail-shaped, tetrahedron-shaped, chess piece-s…
Holographic recording optimization in amorphous As-Se-S films
2003
The holographic recording parameters of amorphous chalcogenide semiconductor (AChS) thin films under optimization depend on hologram type. So, using self-enhancement effect during recording and wet etching after recording enable possibility to decrease recording energy and increase of signal/noise ratio for embossed holograms. Choosing the appropriate light exposure permit us to achieve equal values of diffraction efficiency (DE) for different diffraction orders during fabrication of light splitting holographic optical elements (HOE). Changing film thickness and recording wavelength it is possible to find optimal conditions for high DE holographic gratings readable at infrared region of lig…