Structural changes in titanium dioxide nanocrystals during plastic deformation

2005 ◽  
Vol 38 (5) ◽  
pp. 749-756 ◽  
Author(s):  
Ulrich Gesenhues
Keyword(s):  
Structural Changes ◽  
Crystal Size ◽  
Lower Layer ◽  
High Energy ◽  
Primary Crystal ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Hall Method ◽  
Means Of Transmission

The polygonization of 200 nm rutile crystals during dry ball-milling at 10gwas monitored in detail by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The TEM results showed how to modify the Williamson–Hall method for a successful evaluation of crystal size and microstrain from XRD profiles. Macrostrain development was determined from the minute shift of the most intense reflection. In addition, changes in pycnometrical density were monitored. Accordingly, the primary crystal is disintegrated during milling into a mosaic of 12–35 nm pieces where the grain boundaries induce up to 1.2% microstrain in a lower layer of 6 nm thickness. Macrostrain in the interior of the crystals rises to 0.03%. The pycnometrical density, reflecting the packing density of atoms in the grain boundary, decreases steadily by 1.1%. The results bear relevance to our understanding of plastic flow and the mechanism of phase transitions of metal oxides during high-energy milling.

scholarly journals Structural Evolution in Wet Mechanically Alloyed Co-Fe-(Ta,W)-B Alloys

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 800
Author(s):  
Vladimír Girman ◽  
Maksym Lisnichuk ◽  
Daria Yudina ◽  
Miloš Matvija ◽  
Pavol Sovák ◽  
...  
Keyword(s):  
Structural Changes ◽  
Magnetic Measurements ◽  
Structural Evolution ◽  
High Energy ◽  
Control Agent ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Transmission Electron ◽  
X Ray Absorption

In the present study, the effect of wet mechanical alloying (MA) on the glass-forming ability (GFA) of Co43Fe20X5.5B31.5 (X = Ta, W) alloys was studied. The structural evolution during MA was investigated using high-energy X-ray diffraction, X-ray absorption spectroscopy, high-resolution transmission electron microscopy and magnetic measurements. Pair distribution function and extended X-ray absorption fine structure spectroscopy were used to characterize local atomic structure at various stages of MA. Besides structural changes, the magnetic properties of both compositions were investigated employing a vibrating sample magnetometer and thermomagnetic measurements. It was shown that using hexane as a process control agent during wet MA resulted in the formation of fully amorphous Co-Fe-Ta-B powder material at a shorter milling time (100 h) as compared to dry MA. It has also been shown that substituting Ta with W effectively suppresses GFA. After 100 h of MA of Co-Fe-W-B mixture, a nanocomposite material consisting of amorphous and nanocrystalline bcc-W phase was synthesized.

Mechanism of Achieving Nanocrystalline AIRu By Ball Milling

1988 ◽  
Vol 132 ◽  
Author(s):  
E. Hellstern ◽  
H. J. Fecht ◽  
C. Garland ◽  
W. L. Johnson ◽  
W. M. Keck
Keyword(s):  
Ball Milling ◽  
Crystal Size ◽  
Shear Bands ◽  
Nanocrystalline Structure ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Energy Ball ◽  
Small Grains

ABSTRACTWe investigated through X- ray diffraction and transmission electron microscopy the crystal refinement of the intermetallic compound AIRu by high- energy ball milling. The deformation process causes a decrease of crystal size to 5–7 rum and an increase of atomic level strain. This deformation is localized in shear bands with a thickness of 0.5 to 1 micron. Within these bands the crystal lattice breaks into small grains with a typical size of 8–14 rum. Further deformation leads to a final nanocrystalline structure with randomly oriented crystallite grains separated by high- angle grain boundaries.

scholarly journals Multiscale Copper-µDiamond Nanostructured Composites

2012 ◽  
Vol 730-732 ◽  
pp. 925-930
Author(s):  
Daniela Nunes ◽  
Vanessa Livramento ◽  
Horácio Fernandes ◽  
Carlos Silva ◽  
Nobumitsu Shohoji ◽  
...  
Keyword(s):  
Pure Copper ◽  
Thermal Stabilization ◽  
Hot Extrusion ◽  
Processing Parameters ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Optimal Processing ◽  
Novel Approach ◽  
Transmission Electron

Nanostructured copper-diamond composites can be tailored for thermal management applications at high temperature. A novel approach based on multiscale diamond dispersions is proposed for the production of this type of materials: a Cu-nDiamond composite produced by high-energy milling is used as a nanostructured matrix for further dispersion of micrometer sized diamond. The former offers strength and microstructural thermal stability while the latter provides high thermal conductivity. A series of Cu-nDiamond mixtures have been milled to define the minimum nanodiamond fraction suitable for matrix refinement and thermal stabilization. A refined matrix with homogenously dispersed nanoparticles could be obtained with 4 at.% nanodiamond for posterior mixture with mDiamond and subsequent consolidation. In order to define optimal processing parameters, consolidation by hot extrusion has been carried out for a Cu-nDiamond composite and, in parallel, for a mixture of pure copper and mDiamond. The materials produced were characterized by X-ray diffraction, scanning and transmission electron microscopy and microhardness measurements.

Effect of Nitridation Magnetic Properties of Nanocrystalline Fe-Co Alloy Powders

2010 ◽  
Vol 654-656 ◽  
pp. 1106-1109
Author(s):  
Ya Qiong He ◽  
Chang Hui Mao ◽  
Jian Yang
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Alloy Powder ◽  
High Energy ◽  
X Ray Diffraction ◽  
Powder Mixtures ◽  
X Ray ◽  
Transmission Electron ◽  
Nitridation Temperature ◽  
Microstructure And Magnetic Properties

Nanocrystalline Fe-Co alloy powders, which were prepared by high-energy mechanical milling, were nitrided under the mixing gas of NH3/H2 in the temperature range from 380°C to 510°C. X-ray diffraction (XRD) was used to analyze the grain size and reaction during the processing. The magnetic properties of the nitrided powders were measured by Vibrating Sample Magnetometer (VSM). The results show that with the appearance of Fe4N phase after nitride treatment, and the grain-size of FeCo phase decreases with the increase of nitridation temperature between 380°C to 450°C.The saturation magnetization of nitrided alloy powder treated at 480°C is about 18% higher than that of the initial Fe-Co alloy powder, accompanied by the reduction of the coercivity. Transmission electron microscope (TEM) was used, attempting to further analyze the effect of Fe4N phase on microstructure and magnetic properties of the powder mixtures.

Size dependent behavior of Fe3O4crystals during electrochemical (de)lithiation: an in situ X-ray diffraction, ex situ X-ray absorption spectroscopy, transmission electron microscopy and theoretical investigation

2017 ◽  
Vol 19 (31) ◽  
pp. 20867-20880 ◽  
Author(s):  
David C. Bock ◽  
Christopher J. Pelliccione ◽  
Wei Zhang ◽  
Janis Timoshenko ◽  
K. W. Knehr ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
X Ray ◽  
Size Dependent ◽  
Transmission Electron ◽  
Dependent Behavior ◽  
X Ray Absorption

Crystal and atomic structural changes of Fe3O4upon electrochemical (de)lithiation were determined.

scholarly journals Enhanced Photocatalytic Activity of Vanadium-Doped SnO2 Nanoparticles in Rhodamine B Degradation

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
H. Letifi ◽  
Y. Litaiem ◽  
D. Dridi ◽  
S. Ammar ◽  
R. Chtourou
Keyword(s):  
Photocatalytic Activity ◽  
Rhodamine B ◽  
Crystal Size ◽  
Sno2 Nanoparticles ◽  
X Ray Diffraction ◽  
Optical Studies ◽  
Vanadium Concentration ◽  
X Ray ◽  
Transmission Electron ◽  
20 Nm

In this paper, we have reported a novel photocatalytic study of vanadium-doped SnO2 nanoparticles (SnO2: V NPs) in rhodamine B degradation. These NPs have been prepared with vanadium concentrations varying from 0% to 4% via the coprecipitation method. Structural, morphological, and optical properties of the prepared nanoparticles have been investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscope (TEM), and UV-Vis and photoluminescence (PL) spectroscopy. Structural properties showed that both undoped and SnO2: V NPs exhibited the tetragonal structure, and the average crystal size has been decreased from 20 nm to 10 nm with the increasing doping level of vanadium. Optical studies showed that the absorption edge of SnO2: V NPs showed a redshift with the increasing vanadium concentration. This redshift leads to the decrease in the optical band gap from 3.25 eV to 2.55 eV. A quenching in luminescence intensity has been observed in SnO2: V NPs, as compared to the undoped sample. Rhodamine B dye (RhB) has been used to study the photocatalytic degradation of all synthesized NPs. As compared to undoped SnO2 NPs, the photocatalytic activity of SnO2: V NPs has been improved. RhB dye was considerably degraded by 95% within 150 min over on the SnO2: V NPs.

Epitaxial growth of BaO and SrO with new crystal structures using mass-separated low-energy O+ beams

1993 ◽  
Vol 8 (2) ◽  
pp. 321-323 ◽  
Author(s):  
Ryusuke Kita ◽  
Takashi Hase ◽  
Hiromi Takahashi ◽  
Kenichi Kawaguchi ◽  
Tadataka Morishita
Keyword(s):  
Lattice Constant ◽  
High Energy ◽  
Low Energy ◽  
Diffraction Reflection ◽  
High Energy Electron ◽  
Bulk Crystals ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Cubic Structure

The growth of BaO and SrO on SrTiO3(100) substrates using mass-separated low-energy (50 eV) O+ beams has been studied using x-ray diffraction, reflection high-energy electron diffraction, and high-resolution transmission electron microscopy. It was found that the BaO and SrO films have been epitaxially grown with new structures different from those of corresponding bulk crystals: The BaO films have a cubic structure with a lattice constant of 4.0 Å, and the SrO films have a tetragonal structure with a lattice constant of a = 3.7 Å parallel to the substrate and with c = 4.0 Å normal to the substrate.

scholarly journals Characterization of Pr-Doped LaF3 Nanoparticles Synthesized by Different Variations of Coprecipitation Method

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
M. S. Pudovkin ◽  
D. A. Koryakovtseva ◽  
E. V. Lukinova ◽  
S. L. Korableva ◽  
R. Sh. Khusnutdinova ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Optical Spectroscopy ◽  
Coprecipitation Method ◽  
Luminescence Lifetime ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Hall Method ◽  
Stoichiometric Proportion

A set of Pr3+:LaF3 nanoparticles (NPs) were synthesized via coprecipitation method at three stoichiometric proportions of La(NO3)3, Pr(NO3)3, and NaF (1 : 0.8, 1 : 1, and 1 : 6, respectively). Two ways of mixing of the La(NO3)3, Pr(NO3)3, and NaF solutions (dropwise and swift addition) were used. One sample was subjected to microwave (MW) treatment for 30, 90, and 180 min. All the samples were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). For all the samples, optical spectroscopy experiments were carried out. The XRD data were analyzed via the Debye-Scherrer and Williamson-Hall methods. It was revealed that the way of mixing of the La(NO3)3, Pr(NO3)3, and NaF solutions strongly affects the shape of the NPs. The slow dropwise addition of the NaF solution leads to the plate-like NP (PLNP) formation; otherwise, the swift addition of the NaF solution leads to the formation of more sphere-like NPs (SLNPs). The size and regularity in shape of the NP increase with the increasing stoichiometric proportion of La(NO3)3, Pr(NO3)3, and NaF from 1 : 0.8 to 1 : 6. The size and regularity in shape of the SLNPs increase with the increasing time of MW treatment. The Debye-Scherrer and Williamson-Hall methods confirmed the anisotropic shape of the PLNPs. The Williamson-Hall method showed that the values of strain are almost similar for all the samples (around 14∗10-4). Optical spectroscopy experiments revealed that although all the samples have an equal chemical composition, the luminescence lifetimes for different samples differ between each other. The luminescence lifetime of the PLNPs is less than that of the SLNPs having an equal stoichiometric proportion of La(NO3)3, Pr(NO3)3, and NaF. The luminescence lifetime of the 1 : 1 SLNPs increases with the increasing time of MW treatment.

The structural changes of polycrystalline film C60/C70: Ni caused by Ni diffusion

1996 ◽  
Vol 11 (12) ◽  
pp. 3146-3151 ◽  
Author(s):  
E. Czerwosz ◽  
P. Byszewski ◽  
R. Diduszko ◽  
H. Wronka ◽  
P. Dluźewski ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Raman Spectroscopy ◽  
Structural Changes ◽  
Thermal Conditions ◽  
Vacuum Deposition ◽  
X Ray Diffraction ◽  
Polycrystalline Structure ◽  
X Ray ◽  
Transmission Electron

C60/C70: Ni films with 1.5 wt. % Ni concentration obtained by vacuum deposition under different thermal conditions have been investigated. The structural changes of the layers were investigated by transmission electron microscopy, electron and x-ray diffraction, and Raman spectroscopy. The polycrystalline structure was detected for the layers grown at approximately 450 K on the substrate. At elevated temperature and maintained temperature gradient on the substrate during the process, the changes of the layer's structure and the formation of Ni microcrystals were observed. The Ni microcrystals (5–10 nm in the diameter) and the elongated shapes dimensioned 10 × 150 nm were perceived.

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