scholarly journals Extraction of Tantalum Powder via the Magnesium Reduction of Tantalum Pentoxide

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 205 ◽  
Author(s):  
Seon-Min Hwang ◽  
Jei-Pil Wang ◽  
Dong-Won Lee
Keyword(s):  
Acid Leaching ◽  
Argon Atmosphere ◽  
Tantalum Pentoxide ◽  
Tantalum Powder ◽  
Mixed Structure ◽  
Crystallite Sizes ◽  
The Mean ◽  
Reduction Effect ◽  
Maximal Reduction ◽  
Hcl Solution

The metallic tantalum powder was successfully synthesized via reduction of tantalum pentoxide (Ta2O5) with magnesium gas at 1073~1223 K for 10 h inside the chamber held under an argon atmosphere. The powder obtained after reduction shows the Ta–MgO mixed structure and that the MgO component was dissolved and removed fully via stirring in a water-based HCl solution. The particle size in the tantalum powder obtained after acid leaching was shown to be in a range of 50~300 nm, and the mean internal crystallite sizes measured by the Scherrer equation varied from 11.5 to 24.7 nm according to the increase in reduction temperatures. The temperature satisfactory for a maximal reduction effect was found to be 1173 K because the oxygen content was minimally saturated to about 1.3 wt %.

ROLE OF PROCESS CONTROL AGENTS ON MILLING BEHAVIOR OF Al AND TiO2 POWDER MIXTURE TO SYNTHESIZE TiAl/Al2O3 NANO COMPOSITE

2012 ◽  
Vol 05 ◽  
pp. 638-645 ◽  
Author(s):  
S. ALAMOLHODA ◽  
S. HESHMATI-MANESH ◽  
A. ATAIE ◽  
A. BADIEI
Keyword(s):  
Process Control ◽  
Tio2 Powder ◽  
Nano Composite ◽  
Powder Mixtures ◽  
Gaussian Method ◽  
Opposite Behavior ◽  
Crystallite Sizes ◽  
The Mean ◽  
Milled Powders

In this study effect of adding various process control agents (PCAs) to powder mixtures of Al and TiO 2 which are mechanically activated so as to form TiAl - Al 2 O 3 nano-composite have been investigated. Phase constitutions and morphology of the milled powders were evaluated by XRD and SEM techniques, respectively. The mean crystallite sizes of the milled powders were calculated by Cauchy-Gaussian method. Thermal behavior of the milled powders was also studied by DTA to investigate formation of the final phases. The results showed that the mean crystallite size of the milled powders in the presence of PCAs was smaller than that of the sample milled without PCA addition. DTA traces showed that addition of PCAs retards the reduction of TiO 2 by Al . In samples milled in presence of PCA, the reductive reaction generally took place after melting of Al particles whereas the sample milled without PCA addition showed an opposite behavior. Also, in comparison with the sample milled with no PCA addition, in other samples the reductive reaction took place at relatively lower temperatures.

scholarly journals Structural and magnetic properties of mechanochemically synthesized nanosized yttrium titanate

2012 ◽  
Vol 66 (3) ◽  
pp. 309-315 ◽  
Author(s):  
Tanja Barudzija ◽  
Alexey Gusev ◽  
Dragana Jugovic ◽  
Milena Marinovic-Cincovic ◽  
Miroslav Dramicanin ◽  
...  
Keyword(s):  
Quantum Interference ◽  
Single Phase ◽  
High Energy ◽  
Argon Atmosphere ◽  
Molar Ratio ◽  
Superconducting Quantum Interference Device ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Mean ◽  
First Time

Nanosized perovskite YTiO3 with the mean crystallite size of 18 nm was synthesized for the first time by mechanochemical treatment. The mechanochemical solid state reaction between commercial Y2O3 powder and mechanochemically synthesized TiO powder in molar ratio 0.5:1 was completed for 3 h in a high-energy planetary ball mill in argon atmosphere. The heating in vacuum at 1150 ?C for 12 h transforms nanosized YTiO3 to a well-crystallized single-phase perovskite YTiO3. Both samples were characterized by X-ray diffraction (XRD) and thermogravimetric (TGA/DTA) analyses, as well as superconducting quantum interference device magnetometer (SQUID) measurements.

Structural Change and Magnetic Properties of Mechanically Alloyed Spinel Ferrite CoFe2O4

2020 ◽  
Vol 855 ◽  
pp. 108-116
Author(s):  
Novrita Idayanti ◽  
Dedi ◽  
Azwar Manaf
Keyword(s):  
Magnetic Properties ◽  
Sintering Temperature ◽  
Spinel Ferrite ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
A Value ◽  
Hall Plot ◽  
Crystallite Sizes ◽  
The Mean

Magnetic property studies and the crystallite structures evolution of spinel ferrite CoFe2O4 particles are reported in this paper. The ferrite was prepared through mechanical milling of all alloy precursors and sintered at various temperatures of 800, 900, 1000, and 1100 °C to promote the crystalline structure. X-ray diffraction (XRD) and Williamson-Hall plot were used to calculate the mean crystallite size and microstrain. Changes in the microstructure and crystallite sizes were occurring due to sintering treatments. It is found that the remanence (Mr) and saturation magnetization (Ms) increase with increasing sintering temperature, but a decrease occurred only at the temperature of 1100 °C. The optimum magnetic properties were obtained in a sample sintered at 1000 °C with a value of Mr = 36.00 emu/g and Ms= 74.05 emu/g.

A generalized geometric approach to anisotropic peak broadening due to domain morphology

2015 ◽  
Vol 48 (1) ◽  
pp. 189-194 ◽  
Author(s):  
D. Ectors ◽  
F. Goetz-Neunhoeffer ◽  
J. Neubauer
Keyword(s):  
Powder Diffraction ◽  
Geometric Approach ◽  
Geometric Description ◽  
Reasonable Approximation ◽  
Peak Broadening ◽  
Mean Diameter ◽  
Physically Based ◽  
Crystallite Sizes ◽  
The Mean

This article reports the derivation of a physically based geometric description of the mean diameter of orthogonal shapes and provides an efficient formalism to relate these to reciprocal lattices and corresponding apparent crystallite sizes. The following descriptions provide a reasonable approximation for the simulation and refinement of anisotropic domain morphology in powder diffraction techniques.

A STUDY ON THE SYNTHESIS OF ULTRA-FINE IN SITUNi3Al–Al2O3/TiC COMPOSITE POWDER

2010 ◽  
Vol 17 (02) ◽  
pp. 195-200
Author(s):  
DONG-WOONG KIM ◽  
SUNG-HYUN CHOI ◽  
KYOUNG-ROK DO ◽  
SU-GUN LIM ◽  
IN-SHUP AHN
Keyword(s):  
Annealing Temperature ◽  
Cutting Tool ◽  
High Strength ◽  
Argon Atmosphere ◽  
Low Density ◽  
Composite Powders ◽  
Tool Materials ◽  
Good Corrosion Resistance ◽  
High Temperature Structural Material ◽  
The Mean

Titanium carbide ( TiC ) has a low density, relatively high thermal and electrical conductivity. TiC is also very stable, with a melting temperature of 3100°C and does not undergo phase transformations. These properties have attraction to apply cutting tool extensively. Recently, in order to improve the properties of cermet tool materials, most researches have been carried out on the development of new binder. Ni3Al intermetallic is an interesting material because it has a great advantage of application for some structural materials, especially at the high temperatures. Ni3Al has low density, high strength and good corrosion resistance properties, which recommend them for the application of high temperature structural material. In this study, we had investigated the effects of mechanical alloying time and annealing temperature on the Ni3Al–Al2O3/TiC phase formation. Raw powders to fabricate Ni3Al–Al2O3/TiC composite powders were Ni , Al , TiH2 and activated carbon. These powders were ball-milled in planetary milling jar in argon atmosphere. Ball-milled powders were annealed up to 1200°C in Ar + 4%H2 atmosphere. The mean particle size of 300 nm was obtained after 10 h ball-milling. Ni3Al–Al2O3/TiC composite powders were formed by annealing for 1 h over 1100°C.

The mean crystallite size within a hydrogenated nanocrystalline silicon based photovoltaic solar cell and its role in determining the corresponding crystalline volume fraction

2014 ◽  
Vol 92 (7/8) ◽  
pp. 857-861 ◽  
Author(s):  
K.J. Schmidt ◽  
Y. Lin ◽  
M. Beaudoin ◽  
G. Xia ◽  
S.K. O’Leary ◽  
...  
Keyword(s):  
Crystallite Size ◽  
Volume Fraction ◽  
Nanocrystalline Silicon ◽  
Crystalline Volume Fraction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Photovoltaic Solar Cell ◽  
Crystallite Sizes ◽  
The Mean ◽  
Silicon Based

We examine the dependence of the crystalline volume fraction on the mean crystallite size for hydrogenated nanocrystalline silicon based photovoltaic solar cells; this work builds upon an earlier study by Schmidt et al. (Mater. Res. Soc. Symp. Proc. 1536 (2013)). For each photovoltaic solar cell considered, the X-ray diffraction and Raman spectra are measured. Through the application of Scherrer’s equation, the X-ray diffraction results are used to determine the corresponding mean crystallite sizes. Through peak decomposition, the Raman results are used to estimate the corresponding crystalline volume fraction. Plotting the crystalline volume fraction as a function of the mean crystallite size, it is found that larger mean crystallite sizes tend to favor reduced crystalline volume fractions. The ability to randomly pack smaller crystallites with a greater packing fraction than their larger counterparts was suggested as a possible explanation for this observation.

scholarly journals Extraction of REEs (Ce, Tb, Y, Eu) from Phosphors Waste by a Combined Alkali Roasting–Acid Leaching Process

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 437
Author(s):  
Bing-Xuan He ◽  
Yong Liang ◽  
Lue-Wei Xu ◽  
Long-Bin Shao ◽  
De-Gang Liu ◽  
...  
Keyword(s):  
Rare Earth ◽  
Oxygen Concentration ◽  
Acid Leaching ◽  
Solution Concentration ◽  
Mass Ratio ◽  
Optimum Conditions ◽  
Solid Ratio ◽  
Roasting Temperature ◽  
Leaching Efficiency ◽  
Hcl Solution

Rare Earth (RE) phosphors waste contains valuable rare Earth elements (REEs), such as cerium, terbium, yttrium, and europium. In industry, the process of NaOH roasting followed by acid leaching is usually used to extract the REEs from the waste in China. Using this process, the leaching efficiencies of cerium and terbium are clearly lower than those of other REEs, which results in uneven extraction of REEs in the waste and low total REE leaching efficiency. The key reason is that the trivalent cerium and terbium in the waste are oxidized into RE oxides during NaOH roasting, which are difficult to dissolve in acid solution. To solve this problem, an optimized process of controlling the oxygen concentration during NaOH roasting is proposed in this paper. The influences of the oxygen concentration, roasting temperature, roasting time, mass ratio of waste phosphor to NaOH, HCl solution concentration, acid leaching temperature, acid leaching time, and liquid–solid ratio on the REE leaching efficiency were investigated. Under the optimum conditions, the leaching efficiencies of cerium and terbium increased dramatically and the total REE leaching efficiency is 99.11%.

Hot-Fat Trimming Effects on the Microbiological Quality of Beef Carcasses and Subprimals

1995 ◽  
Vol 58 (9) ◽  
pp. 990-992 ◽  
Author(s):  
R. K. PRASAI ◽  
R. E. CAMPBELL ◽  
L. R. VOGT ◽  
C. L. KASTNER ◽  
D. Y. C. FUNG
Keyword(s):  
Cold Water ◽  
Negative Impact ◽  
Microbiological Quality ◽  
Microbial Reduction ◽  
Microbial Quality ◽  
Beef Carcasses ◽  
Plate Counts ◽  
The Mean ◽  
Reduction Effect

Subcutaneous and kidney-pelvic-heart fat were trimmed from one side of each beef carcass (n = 9) immediately after cold water washing. Both sides were sampled for aerobic plate counts (APCs) before being moved to the chill room (0 h) and after 72 h of cold storage. The mean APCs (log10 colony-forming units (CFU)/cm2) of trimmed (HFT) sides at 0 or 72 h were not different (P > 0.05) from those of the nontrimmed (NFT) sides. All sides at 72 h had reduced microbial counts compared to 0 h. By 72 h, HFT sides had numerically lower counts than NFT sides, indicating that the microbial reduction effect of the chill temperature may have been greater on fat-trimmed carcasses than on nontrimmed carcasses. Subprimals from HFT and NFT sides that were trimmed to 0.64-cm fat thickness were microbiologically analyzed before (0 days) and after (14 days) vacuum storage. APCs of all subprimals were slightly reduced after 14 d; however, no difference (P > 0.05) occurred in treatment effect. The mean APC was higher for HFT-side subprimals than for NFT-side subprimals at both 0 and 14 days. This difference probably was due to the fat trimming required for NFT-side subprimals at day 0 as compared to minimal or no trimming of HFT-side subprimals. Those HFT subprimals which were not subsequently trimmed may have picked up additional microorganisms from contact surfaces during fabrication. Based on our trimming protocol, although HFT did not show any negative impact on the microbial quality of carcasses, the higher APC of HFT-side subprimals indicated that extensive trimming may not be effective in improving the microbial quality of meat.

scholarly journals Effect of Temperature and Texture on Hall–Petch Strengthening by Grain and Annealing Twin Boundaries in the MnFeNi Medium-Entropy Alloy

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 84 ◽  
Author(s):  
Mike Schneider ◽  
Felicitas Werner ◽  
Dennis Langenkämper ◽  
Christian Reinhart ◽  
Guillaume Laplanche
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Dislocation Motion ◽  
Annealing Twin ◽  
Effect Of Temperature ◽  
Compression Tests ◽  
Twin Boundaries ◽  
Grain Sizes ◽  
Crystallite Sizes ◽  
The Mean

Among equiatomic alloys of the Cr-Mn-Fe-Co-Ni system, MnFeNi was shown to exhibit a strong anti-invar behavior but little is known regarding its mechanical properties. The objective of the present study is to investigate Hall–Petch strengthening by grain and annealing twin boundaries in MnFeNi. For this purpose, seven different grain sizes between 17 and 216 µm were produced. Mean grain sizes (excluding annealing twin boundaries) and crystallite sizes (including them) were determined using the linear intercept method. Overall, 25% of the boundaries were found to be annealing twin boundaries regardless of the grain size. In some cases, two twin boundaries can be present in one grain forming an annealing twin, which thickness represents one quarter of the mean grain size. Based on a comparison of the mean twin thickness of different alloys with different stacking fault energy (SFE), we estimated an SFE of 80 ± 20 mJ/m2 for MnFeNi. Compression tests of MnFeNi with different grain sizes were performed between 77 and 873 K and revealed a parallel shift of the Hall–Petch lines with temperature. The interaction between dislocations and boundaries was investigated by scanning transmission electron microscopy (STEM) in a deformed specimen. It was found that a large number of dislocations are piling up against grain boundaries while the pile-ups at annealing twin boundaries contain much fewer dislocations. This indicates that annealing twin boundaries in this alloy are less effective obstacles to dislocation motion than grain boundaries.

scholarly journals Synthesis of θ-Al2O3 Whiskers with Twins

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 895
Author(s):  
Nan Liao ◽  
Xiaojia Su ◽  
Haiwen Zhang ◽  
Qingguo Feng ◽  
Salvatore Grasso ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Specific Surface ◽  
Hydrothermal Method ◽  
Surface Area ◽  
Tetragonal Phase ◽  
Monoclinic Phase ◽  
Argon Atmosphere ◽  
Molar Ratio ◽  
Average Width ◽  
The Mean

In this work, θ-Al2O3 whiskers with twins were successfully fabricated by a hydrothermal method followed by annealing at 1000 °C in argon atmosphere using Al2(SO4)3·18H2O, CO(NH2)2 and PEG2000 as initial materials. It is confirmed that precursor of AlO(OH) whiskers is suitable to be used for preparing alumina whiskers when the molar ratio of Al3+: CO(NH2)2 is selected to be 1:6. The mean length of obtained whiskers is 1.5 μm and the average width is 0.1 μm. Interestingly, it is found that the as-prepared θ-Al2O3 whiskers consist of twins with (100) plane as the twin surface, which is ascribed to the phase transformation from tetragonal phase (δ-Al2O3) to monoclinic phase (θ-Al2O3) during the annealing. Additionally, the specific surface area of θ-Al2O3 whiskers is measured to be 38.2 m2/g.

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