scholarly journals Synthesis of Non-Cubic Nitride Phases of Va-Group Metals (V, Nb, and Ta) from Metal Powders in Stream of NH3 Gas under Concentrated Solar Radiation

2021 ◽  
Vol 5 (2) ◽  
pp. 19
Author(s):  
Nobumitsu Shohoji ◽  
Fernando Almeida Costa Oliveira ◽  
José Galindo ◽  
José Rodríguez ◽  
Inmaculada Cañadas ◽  
...  
Keyword(s):  
Lattice Structure ◽  
Solar Furnace ◽  
Degree Of Crystallinity ◽  
Nitride Phase ◽  
Face Centered Cubic ◽  
Metal Powders ◽  
Group Metal ◽  
Ε Phase ◽  
Δ Phase ◽  
Face Centered

Using a high-flux solar furnace, loosely compacted powders of Va-group transition metal (V, Nb, and Ta) were reacted with stream of NH3 gas (uncracked NH3 gas) being heated by concentrated solar beam to a temperature (T) range between 600 and 1000 °C. From V, sub-nitride V2N (γ phase) and hypo-stoichiometric mono-nitride VN possessing fcc (face-centered cubic) crystal lattice structure (δ phase) were synthesized. On the other hand, in the reaction product from Nb and Ta, hexagonal mono-nitride phase with N/M atom ratio close to 1 (ε phase) was detected. The reaction duration was normalized to be 60 min. In a conventional industrial or laboratory electric furnace, the synthesis of mono-nitride phase with high degree of crystallinity that yield sharp XRD peaks for Va-group metal might take a quite long duration even at T exceeding 1000 °C. In contrast, mono–nitride phase MN of Va-group metal was synthesized for a relatively short duration of 60 min at T lower than 1000 °C being co-existed with lower nitride phases.

Epitaxial Ni nanoparticles on CaF2(001), (110) and (111) surfaces studied by three-dimensional RHEED, GIXD and GISAXS reciprocal-space mapping techniques

2017 ◽  
Vol 50 (3) ◽  
pp. 830-839 ◽  
Author(s):  
S. M. Suturin ◽  
V. V. Fedorov ◽  
A. M. Korovin ◽  
N. S. Sokolov ◽  
A. V. Nashchekin ◽  
...  
Keyword(s):  
Lattice Structure ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
High Energy ◽  
Reciprocal Space ◽  
Mapping Technique ◽  
Face Centered Cubic ◽  
X Ray ◽  
Cubic Lattice ◽  
Face Centered

The development of growth techniques aimed at the fabrication of nanoscale heterostructures with layers of ferroic 3dmetals on semiconductor substrates is very important for their potential usage in magnetic media recording applications. A structural study is presented of single-crystal nickel island ensembles grown epitaxially on top of CaF2/Si insulator-on-semiconductor heteroepitaxial substrates with (111), (110) and (001) fluorite surface orientations. The CaF2buffer layer in the studied multilayer system prevents the formation of nickel silicide, guides the nucleation of nickel islands and serves as an insulating layer in a potential tunneling spin injection device. The present study, employing both direct-space and reciprocal-space techniques, is a continuation of earlier research on ferromagnetic 3dtransition metals grown epitaxially on non-magnetic and magnetically ordered fluorides. It is demonstrated that arrays of stand-alone faceted nickel islands with a face-centered cubic lattice can be grown controllably on CaF2surfaces of (111), (110) and (001) orientations. The proposed two-stage nickel growth technique employs deposition of a thin seeding layer at low temperature followed by formation of the islands at high temperature. The application of an advanced three-dimensional mapping technique exploiting reflection high-energy electron diffraction (RHEED) has proved that the nickel islands tend to inherit the lattice orientation of the underlying fluorite layer, though they exhibit a certain amount of {111} twinning. As shown by scanning electron microscopy, grazing-incidence X-ray diffraction (GIXD) and grazing-incidence small-angle X-ray scattering (GISAXS), the islands are of similar shape, being faceted with {111} and {100} planes. The results obtained are compared with those from earlier studies of Co/CaF2epitaxial nanoparticles, with special attention paid to the peculiarities related to the differences in lattice structure of the deposited metals: the dual-phase hexagonal close-packed/face-centered cubic lattice structure of cobalt as opposed to the single-phase face-centered cubic lattice structure of nickel.

scholarly journals Ti-V-C-Based Alloy with a FCC Lattice Structure for Hydrogen Storage

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 552
Author(s):  
Bo Li ◽  
Liqing He ◽  
Jianding Li ◽  
Hai-Wen Li ◽  
Zhouguang Lu ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Room Temperature ◽  
Lattice Structure ◽  
Activation Process ◽  
Face Centered Cubic ◽  
Hydrogen Storage Materials ◽  
Fcc Lattice ◽  
Bcc Structure ◽  
Face Centered ◽  
Fcc Structure

Here we report a Ti50V50-10 wt.% C alloy with a unique lattice and microstructure for hydrogen storage development. Different from a traditionally synthesized Ti50V50 alloy prepared by a melting method and having a body-centered cubic (BCC) structure, this Ti50V50-C alloy synthesized by a mechanical alloying method is with a face-centered cubic (FCC) structure (space group: Fm-3m No. 225). The crystalline size is 60 nm. This alloy may directly absorb hydrogen near room temperature without any activation process. Mechanisms of the good kinetics from lattice and microstructure aspects were discussed. Findings reported here may indicate a new possibility in the development of future hydrogen storage materials.

Analytical model of the elastic behavior of a modified face-centered cubic lattice structure

2019 ◽  
Vol 98 ◽  
pp. 357-368 ◽  
Author(s):  
Markel Alaña ◽  
Aitziber Lopez-Arancibia ◽  
Ainara Pradera-Mallabiabarrena ◽  
Sergio Ruiz de Galarreta
Keyword(s):  
Analytical Model ◽  
Lattice Structure ◽  
Elastic Behavior ◽  
Face Centered Cubic ◽  
Cubic Lattice ◽  
Face Centered

Approximate model for the crystal structure of precipitates in NaF doped with AlF3

1993 ◽  
Vol 49 (6) ◽  
pp. 846-853 ◽  
Author(s):  
K. Suzuki
Keyword(s):  
Crystal Structure ◽  
Mixed Crystal ◽  
Lattice Structure ◽  
Approximate Model ◽  
Face Centered Cubic ◽  
Cubic Symmetry ◽  
Rotation Axes ◽  
High Form ◽  
Face Centered ◽  
Almost All

The crystal structure of precipitates in a mixed crystal of NaF and 1 mol% AlF3 has been studied at room temperature using both stationary-crystal and rotating-crystal X-ray photographic methods. It has been found that almost all the reflections can be assigned to a face-centered-cubic (f.c.c.) lattice with unit-cell parameter 7.77 Å. The main feature of the diffraction pattern is that the 311 reflection is very strong while the 222 reflection is practically zero, in contrast to the case of high-form cryolite, i.e. cubic Na3AlF6. These features are explained by assuming an f.c.c. arrangement of AlF6 octahedra that are rotated around the 〈111〉 axes by about 47° from the highest-symmetry orientation. It has also been shown that the F ions in each octahedron make large overlaps with the Al ion at the center of the octahedron. A random distribution of rotation axes is also proposed to conform to the cubic symmetry of the lattice structure of the precipitate.

Transformation Crystallography and Plasticity of the δ→α′ Transformation in Plutonium Alloys

2003 ◽  
Vol 802 ◽  
Author(s):  
C. R. Krenn ◽  
M. A. Wall ◽  
A. J. Schwartz
Keyword(s):  
Habit Plane ◽  
Room Temperature ◽  
Face Centered Cubic ◽  
Thermally Activated ◽  
Delta Phase ◽  
Transmission Electron ◽  
Δ Phase ◽  
Face Centered ◽  
Prime Phase

ABSTRACTIn delta phase Pu-Ga alloys, the transformation from the ductile face-centered cubic (fcc) δ phase that is retained at room temperature to the brittle low-temperature monoclinic alpha-prime phase is a thermally activated diffusionless transformation with double-c kinetics. Accurate modeling of the phase transformation requires detailed understanding of the role of plastic flow during the transformation and of the crystallographic transformation path. Using transmission electron microscopy (TEM), we find a significant increase in dislocation density in δ near the α′ plates, which suggests that plastic deformation contributes to the accommodation of the 20% reduction in volume during the transformation. Analysis of a series of optical micrographs of partially transformed alloys suggests that the α′ habit plane is usually nearly perpendicular to <111> δ. However, a small number of TEM observations support a habit plane near <112> or <123>, in agreement with earlier work.

scholarly journals Nanocrystalline Formation during Mechanical Attrition of Cobalt

2006 ◽  
Vol 503-504 ◽  
pp. 751-756 ◽  
Author(s):  
J. Zhou ◽  
C. Sun ◽  
X. Wu ◽  
N.R. Tao ◽  
Gang Liu ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Surface Mechanical Attrition Treatment ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Cubic Phases ◽  
Mechanical Attrition ◽  
Dislocation Arrays ◽  
Ε Phase ◽  
Planar Dislocation ◽  
Face Centered

The nanocrystalline (nc) formation was studied in cobalt (a mixture of ε (hexagonal close packed) and γ (face-centered cubic) phases) subjected to surface mechanical attrition treatment. Electron microscopy revealed the operation of { 10 10 }〈 1120 〉 prismatic and {0001}〈 1120 〉 basal slip in the ε phase, leading to the successive subdivision of grains to nanoscale. In particular, the dislocation splitting into the stacking faults was observed to occur in ultrafine and nc grains. By contrast, the planar dislocation arrays, twins and martensites were evidenced in the γ phase. The strain-induced γ→ε martensitic transformation was found to progress continuously in ultrafine and nc grains as the strain increased. The nc formation in the γ phase was interpreted in terms of the martensitic transformation and twinning.

Evolution of Oxide Particles during Fabrication Processes of 12Cr ODS Steel

2012 ◽  
Vol 1383 ◽  
Author(s):  
Xiaodong Mao ◽  
Tae Kyu Kim ◽  
Sung-Soo Kim ◽  
Chang Hee Han ◽  
Kyu Hwan Oh ◽  
...  
Keyword(s):  
Hot Rolling ◽  
Rolling Process ◽  
Face Centered Cubic ◽  
Metal Powders ◽  
Heat Treated Sample ◽  
Ods Steel ◽  
Treated Sample ◽  
The Matrix ◽  
Oxide Particles ◽  
Face Centered

ABSTRACT12Cr ODS steel samples were prepared by mechanical alloying of the metal powders with 20-30 nm Y2O3 particles followed by isostatic pressing, hot rolling and final heat treatment. Evolutions of oxide particles such as YTaO4 and YCrO3 after each fabrication step were investigated by using TEM with EDS. Crystallographic correlation between oxide particles and the matrix was investigated in a HIPped sample, and interactions between dislocations and oxide particles were observed in hot rolled or heat treated sample. Size distributions of oxide particles were measured by carbon replica samples and it was found that coarsening of oxide particles from 9 to 12 nm occurred during hot rolling process. Additional isothermal annealing at 1250 ˚C revealed that phase transformation of oxide particles from monoclinic YTaO4 to face centered cubic Y3TaO7 was observed.

scholarly journals STUDY ON INFLUENCE OF TEMPERATURE AND DURATION OF HYDROTHERMAL TREATMENT TO PROPERTIES OF NANO FERRITE NiFe2O4 MATERIALS

2018 ◽  
Vol 54 (1A) ◽  
pp. 1 ◽  
Author(s):  
Tran Quang Dat
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Hydrothermal Treatment ◽  
Superparamagnetic Nanoparticles ◽  
Degree Of Crystallinity ◽  
Face Centered Cubic ◽  
Influence Of Temperature ◽  
Face Centered ◽  
Co Precipitation ◽  
Increasing Temperature

NiFe2O4 superparamagnetic nanoparticles have been prepared by the method of spraying - co-precipitation subsequent by hydrothermal treatment. This procedure allowed to produce efficiently nanoparticles with high performances. Different techniques such as XRD, TEM, EDX, VSM were used to investigate the morphology, structure and magnetic properties of the obtained materials. It is shown that the materials have face-centered cubic trevorite structure, and their degree of crystallinity and magnetic properties improved with increasing temperature and time of hydrothermal treatment. After 32 hours of hydrothermal treatment at 160°C, NiFe2O4 nanomaterial has particle size of about 23 nm and saturation magnetization (Ms) of 49 emu/g.

Monte carlo study of the phase diagrams of binary alloys with face centered cubic lattice structure

1981 ◽  
Vol 29 (9) ◽  
pp. 1655-1665 ◽  
Author(s):  
Kurt Binder ◽  
Joel L. Lebowitz ◽  
Mohan K. Phani ◽  
Malvin H. Kalos
Keyword(s):  
Monte Carlo ◽  
Phase Diagrams ◽  
Lattice Structure ◽  
Binary Alloys ◽  
Monte Carlo Study ◽  
Face Centered Cubic ◽  
Cubic Lattice ◽  
Face Centered

scholarly journals Control of Microstructure for Co-Cr-Mo Fibers Fabricated by Unidirectional Solidification

Crystals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 11
Author(s):  
Shoki Abe ◽  
Yuui Yokota ◽  
Takayuki Nihei ◽  
Masao Yoshino ◽  
Akihiro Yamaji ◽  
...  
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Growth Direction ◽  
Unidirectional Solidification ◽  
Face Centered Cubic ◽  
Close Packed Structure ◽  
Ε Phase ◽  
Hexagonal Close Packed Structure ◽  
Packed Structure ◽  
Face Centered

Co-Cr-Mo alloy fibers of 2 mm in diameter were fabricated from the melt at 1, 2, and 5 mm/min growth rates by unidirectional solidification using an alloy-micro-pulling-down (A-µ-PD) method to control the microstructure. All elements, Co, Cr, and Mo, were distributed in stripes elongated along the growth direction due to constitutional undercooling. Both Co-Cr-Mo fibers fabricated at 2 and 5 mm/min growth rates were composed of the γ phase with a face-centered cubic structure (fcc-γ phase) and ε-phase with a hexagonal close-packed structure (hcp-ε phase), and the ratio of the fcc-γ phase in the fiber fabricated at 5 mm/min growth rate was higher than that in the fiber fabricated at 2 mm/min. The results suggest that a faster growth rate increases the ratio of the fcc-γ phase in the Co-Cr-Mo fiber fabricated by unidirectional solidification.

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