Search results for "NANOCRYSTALLINE"

Impact of gadolinium on the structure and magnetic properties of nanocrystalline powders of iron oxides produced by the extraction-pyrolytic method

2020

The work has been done in frame of the TransFerr project. It has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 778070. This research was also supported by Latvian Research Council project lzp-2018/1-0214. A.I.P. appreciates support from the Estonian Research Council grant (PUT PRG619).

Advances in Design, Simulation and Manufacturing IV

2021

This book reports on topics at the interface between mechanical and chemical engineering, emphasizing design, simulation, and manufacturing. Specifically, it covers recent developments in the mechanics of solids and structures, numerical simulation of coupled problems, including fatigue, fluid behavior, particle movement, pressure distribution. Further, it reports on developments in chemical process technology, heat and mass transfer, energy-efficient technologies, and industrial ecology. Based on the 4th International Conference on Design, Simulation, Manufacturing: The Innovation Exchange (DSMIE-2021), held on June 8-11, 2021, in Lviv, Ukraine, this second volume of a 2-volume set provide…

Time-Resolved Luminescence of Nanocrystalline Inorganic Complex Oxides

2007

Two types of complex nanosized oxides – cerium doped Y3Al5O12 (YAG) and CaWO4– have been studied by means of time-resolved luminescence spectroscopy. Comparative study of time-resolve luminescence characteristics of cerium doped YAG single crystal, nanopowders and nanoceramic as well as for CaWO4 macro- and nanocrystals has been done. Two components in the decay kinetic of Ce3+ related emission in YAG nanocrystals were detected and it was suggested that a different energy transfer rate to volume and surface Ce3+ ions takes place. It is shown that the segregation of Ce3+ ions near nanoparticles surface and/or dislocation lines plays a crucial role in degradation of light yield of cerium rela…

Zn K-edge XANES in nanocrystalline ZnO

2007

Zn K-edge XANES in ZnO has been calculated within the full-multiple-scattering (FMS) and finite difference method (FDM) formalism using the ab initio FDMNES code. The influence of non-muffin-tin potential, bulk defects, surface termination and polarization effects on XANES has been analysed. The obtained theoretical results are compared with available experimental data for polycrystalline and nanocrystalline zinc oxide systems.

Nanocrystalline FeAl Synthesis by MASHS with <i>In Situ</i> and Post Mortem Characterizations

1999

Ba 6 P 12 N 17 O 9 Br 3 – A Column‐Type Phosphate Structure Solved from Single‐Nanocrystal Data Obtained by Automated Electron Diffraction Tomography

2011

Oxonitridophosphate Ba6P12N17O9Br3 was synthesized by heating a multicomponent mixture of BaBr2, BaS, phosphoryl triamide and thiophosphoryl triamide in an evacuated and sealed silica-glass ampoule to 750 °C. Ba6P12N17O9Br3 was obtained as the main product as a nanocrystalline powder. The crystal structure was determined ab initio on the basis of electron diffraction data acquired from a single needle-shaped nanocrystal by automated diffraction tomography. Ba6P12N17O9Br3 crystallizes in the hexagonal space group P63/m (no. 176) with unit cell parameters a = 14.654(19), c = 8.255(9) A and Z = 2. Its structure includes triangular, column-shaped anions of ∞1{(P12N17O9)9–}, which are built from…

Compressibility and Structural Stability of Nanocrystalline TiO2 Anatase Synthesized from Freeze-Dried Precursors

2014

The high-pressure structural behavior of 30 nm nanoparticles of anatase TiO2 was studied under hydrostatic and quasi-hydrostatic conditions up to 25 GPa. We found that the structural sequence is not sensitive to the use of different pressure transmitting media. Anatase-type nanoparticles exhibit a phase transition beyond 12 GPa toward a baddeleyite-type structure. Under decompression this phase transition is irreversible, and a metastable columbite-type structure is recovered at ambient conditions. The bulk modulus of anatase-type nanoparticles was determined confirming that nanoparticles of TiO2 are more compressible than bulk TiO2. Similar conclusions were obtained after the determination…

Some aspects of pulsed laser deposition of Si nanocrystalline films

2009

International audience; Nanocrystalline silicon films were deposited by a picosecond laser ablation on different substrates in vacuum at room temperature. A nanocrystalline structure of the films was evidenced by atomic force microscopy (AFM), optical and Raman spectroscopies. A blue shift of the absorption edge was observed in optical absorption spectra, and a decrease of the optical phonon energy at the Brillouin zone centre was detected by Raman scattering. Early stages of nanocrystalline film formation on mica and HOPG substrates were studied by AFM. Mechanism of nanocrystal growth on substrate is discussed.

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…

Correlation between milling parameters and microstructure characteristics of nanocrystalline copper powder prepared via a high energy planetary ball …

2007

The microstructure evolution of Cu-nanostructured powders versus the ball milling conditions was investigated by whole peak profile powder pattern modeling method. This method allows defining in some approach the characteristics of as-milled Cu powder microstructure in terms of crystallite size, type and density of dislocations and twin faults density. It is shown that the change of microstructure characteristics of as-milled Cu powder versus the ball milling conditions (under constant time of the ball milling) depend on only some energy parameters of the milling, for example, average size of crystallite is uniquely defined by energy of the shock, whereas the portion of edge and screw compo…