MECHANOCHEMICAL REDUCTION OF MoO3 POWDER BY Al AND Si TO SYNTHESIZE NANOCRYSTALLINE MoSi2

2012 ◽  
Vol 05 ◽  
pp. 119-126 ◽  
Author(s):  
H. RAMEZANALIZADEH ◽  
S. HESHMATI-MANESH
Keyword(s):  
Rotation Speed ◽  
Molybdenum Trioxide ◽  
Mass Ratio ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Milling Operations ◽  
Powder Mass ◽  
Crystallite Sizes ◽  
Xrd Patterns

In this study, mechanical alloying was used to produce MoSi 2 powder directly from molybdenum trioxide. Mixture of MoO 3, Si and Al powders were exposed to high mechanical activation in a planetary ball mill. The ball to powder mass ratio was constant at 33:1 and the rotation speed (cup speed) was 290 rpm during the milling operations. Phase compositions and structural evolutions during milling were investigated by X-ray diffraction analysis. The morphology of the mechanically alloyed powders was evaluated with scanning electron microscope (SEM). From XRD results, it was observed that within 3 hours of milling, MoO 3 was completely reduced and a MoSi 2- Al 2 O 3 composite powder was produced. Further milling resulted in transformation of β- MoSi 2 phase to α- MoSi 2. Mean crystallite sizes in product phases in the sample milled for 30 hours calculated by Scherer method using XRD patterns were found to be less than 100 nm.

Mechanochemical Reduction of MoO3 Powder by Silicone to Synthesize Nanocrystalline MoSi2

2011 ◽  
Vol 264-265 ◽  
pp. 1364-1369 ◽  
Author(s):  
H. Ramezanalizadeh ◽  
Saeed Heshmati-Manesh
Keyword(s):  
Rotation Speed ◽  
Mass Ratio ◽  
Mechanically Alloyed ◽  
Oxide Mixture ◽  
Milling Operations ◽  
Structural Applications ◽  
Powder Mass ◽  
Crystallite Sizes ◽  
The Mean ◽  
Xrd Patterns

Molybdenum disiliside is known as a ceramic material with attractive properties for high temperature structural applications. In this study, mechanical alloying was used to produce MoSi2 powder directly from molybdenum oxide. Mixture of MoO3 and Si powders with commercial purity were exposed to high mechanical activation in a planetary ball mill. The ball to powder mass ratio was selected to be constant at 33:1 and the rotation speed (cup speed) was 600 rpm during the milling operations. Crystallite sizes and structural evolutions during milling were investigated by Xray diffraction analysis. The morphology of the mechanically alloyed powders was evaluated with scanning electron microscope (SEM). From XRD results, it was observed that within 6 hours of milling MoO3 was reduced and fully converted to MoO2. After 17 hours of milling MoO2 also began to reduce and peaks of MoSi2 (both and phases) and Mo were detected. Further milling resulted in a gradual decrease in MoO2 peak intensities because of its continuous reduction. Peaks of MoO2 were also broadened due to refinement of MoO2 crystallite sizes. Scherrer and Williamson-Hall methods using XRD patterns were employed to calculate the mean crystallite size. Calculations indicated that in the sample ball milled for 50 hours, MoSi2 crystallite sizes were less than 100 nm.

scholarly journals Microstructures, Magnetic Properties and Microwave Absorption Characteristics of Ti2+ -Mn4+Substituted Barium Hexaferrite

2016 ◽  
Vol 14 (1) ◽  
pp. 15 ◽  
Author(s):  
Maykel Manawan ◽  
Azwar Manaf ◽  
Bambang Soegijono ◽  
Asep Yudi Hercuadi
Keyword(s):  
Crystallite Size ◽  
Microwave Absorption ◽  
Single Phase ◽  
Barium Hexaferrite ◽  
Grain Morphology ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Xrd Patterns ◽  
Substituted Barium Hexaferrite

The effect of Ti2+-Mn4+substitution on microwave absorption has been studied for BaFe12-2xTixMnxO19 ferrite, where x varies from 0.2, 0.4, 0.6 and 0.8.Ti2+-Mn4+ ions were obtained from TiO and MnO2 precursors which were mechanically alloyed together with BaCO3 and Fe2O3 precursors. X-ray diffraction (XRD) patterns for sintered samples confirmed that the materials are consisted with single phase BHF structure. Unit cell volume and crystallite size was found increase with increasing x. Crystallite size for all samples below 70 nm, but the grain morphology shown that the grains is in range of 200 - 400 nm, which concluded that each grain are polycrystalline. The saturation magnetization is increases up to x = 0.4 and decrease for higher x values, while the coercivity remains decreases monotonically. These results were interpreted in terms of the site preferential occupation of Ti2+ and Mn4+ at low level substitution.These substitution revealed of enhanced reflection loss (RL) up to 25 dB forx=0.6.It suggested that the synthesized can be employed as effective microwave absorbers in various devices.

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.

Synthesis and Magnetic Characterization of La2-xSrxCuO4 Nanoparticles

2020 ◽  
Vol 855 ◽  
pp. 58-63
Author(s):  
Malik Anjelh Baqiya ◽  
Putu Eka Dharma Putra ◽  
Resky Irfanita ◽  
Fitriana ◽  
Darminto ◽  
...  
Keyword(s):  
Quantum Interference ◽  
Single Phase ◽  
Magnetic Behavior ◽  
Superconducting Quantum Interference Device ◽  
X Ray Diffraction ◽  
X Ray ◽  
Post Annealing ◽  
Crystallite Sizes ◽  
Xrd Patterns

Non-doped and strontium-doped lanthanum cuprates (La2CuO4 (LCO) and La1.85Sr0.15CuO4 (LSCO15)) in nano-sized particles were synthesized by the chemically dissolved technique employing HNO3 as the dissolving agent. The structural and magnetic properties were investigated by using an x-ray diffraction (XRD) apparatus and a superconducting quantum interference device (SQUID) magnetometer, respectively. The XRD patterns of LCO and LSCO15 show the formation of the single phase without impurities after the calcinations in air at 1100°C for 15 h and the post-annealing in oxygen at 800 °C for 24 h. The average crystallite sizes of LCO and LSCO15 samples were in a range of around 100 nm confirming nano-sized particles. The LCO and LSCO15 nanoparticles exhibit superconductivity at the superconducting (SC) transition temperature, Tc, of 23 K and 38 K, respectively. The magnetization curve measurements have revealed that both samples show the appearance of ferro- and dia-magnetic behavior at room temperature and the appearance of superconductivity at low temperatures. This result may indicate the coexistence of ferromagnetism and superconductivity below Tc in the nano-sized cuprates.

The influence of X-ray diffraction pattern angular range on Rietveld refinement results used for quantitative analysis, crystallite size calculation and unit-cell parameter refinement

2019 ◽  
Vol 52 (2) ◽  
pp. 252-261 ◽  
Author(s):  
Vladimir Uvarov
Keyword(s):  
Rietveld Refinement ◽  
Unit Cell ◽  
Angular Range ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Crystallite Sizes ◽  
Xrd Patterns ◽  
Artificial Mixtures

This article reports a detailed examination of the effect of the magnitude of the angular range of an X-ray diffraction (XRD) pattern on the Rietveld refinement results used in quantitative phase analysis and quality assurance/quality control applications. XRD patterns from 14 different samples (artificial mixtures, and inorganic and organic materials with nano- and submicrometre crystallite sizes) were recorded in 2θ interval from 5–10 to 120°. All XRD patterns were processed using Rietveld refinement. The magnitude of the workable angular range was gradually increased, and thereby the number of peaks used in Rietveld refinement was also increased, step by step. Three XRD patterns simulated using CIFs were processed in the same way. Analysis of the results obtained indicated that the magnitude of the angular range chosen for Rietveld refinement does not significantly affect the calculated values of unit-cell parameters, crystallite sizes and percentage of phases. The values of unit-cell parameters obtained for different angular ranges diverge by 10−4 Å (rarely by 10−3 Å), that is about 10−2% in relative numbers. The average difference between the calculated and actual phase percentage in artificial mixtures was 1.2%. The maximal difference for the crystallite size did not exceed 0.47, 5.2 and 7.7 nm at crystallite sizes lower than 20, 50 and 120 nm, respectively. It has been established that these differences are statistically insignificant.

Ductile Powders Mechanically Alloyed in an Effective Way

2014 ◽  
Vol 976 ◽  
pp. 119-123
Author(s):  
Jaime Guerrero-Paz
Keyword(s):  
Inductively Coupled Plasma ◽  
Optical Emission Spectroscopy ◽  
Optical Emission ◽  
X Ray Diffraction ◽  
Ball Mills ◽  
Mechanically Alloyed ◽  
Mechanically Alloy ◽  
X Ray ◽  
Inductively Coupled ◽  
Powder Mass

The effect of the powder quantity on the effectiveness of the mechanical alloying process using different ductile powder systems was studied. X-ray diffraction, inductively coupled plasma-optical emission spectroscopy and energy dispersive x-ray spectrometry-scanning electron microscopy were the techniques employed to characterize the mechanically alloyed powders. Results showed that a same volume of powders, which represented different powder mass quantities for each system and composition, was used to mechanically alloy in an effective way in horizontal ball mills.

scholarly journals The X-ray, Raman and TEM Signatures of Cellulose-Derived Carbons Explained

2022 ◽  
Vol 8 (1) ◽  
pp. 4
Author(s):  
Petros Kasaira Mubari ◽  
Théotime Beguerie ◽  
Marc Monthioux ◽  
Elsa Weiss-Hortala ◽  
Ange Nzihou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Raman Spectroscopy ◽  
Structural Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Characterization Techniques ◽  
Transmission Electron ◽  
Crystallite Sizes ◽  
Xrd Patterns ◽  
Average Size

Structural properties of carbonized cellulose were explored to conjugate the outcomes from various characterization techniques, namely X-ray diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy. All these techniques have evidenced the formation of graphene stacks with a size distribution. Cellulose carbonized at 1000 and 1800 °C at a heating rate of 2 °C/min showed meaningful differences in Raman spectroscopy, whereas in XRD, the differences were not well pronounced, which implies that the crystallite sizes calculated by each technique have different significations. In the XRD patterns, the origin of a specific feature at a low scattering angle commonly reported in the literature but poorly explained so far, was identified. The different approaches used in this study were congruous in explaining the observations that were made on the cellulose-derived carbon samples. The remnants of the basic structural unit (BSU) are developed during primary carbonization. Small graphene-based crystallites inherited from the BSUs, which formerly developed during primary carbonization, were found to coexist with larger ones. Even if the three techniques give information on the average size of graphenic domains, they do not see the same characteristics of the domains; hence, they are not identical, nor contradictory but complementary. The arguments developed in the work to explain which characteristics are deduced from the signal obtained by each of the three characterization techniques relate to physics phenomena; hence, they are quite general and, therefore, are valid for all kind of graphenic materials.

Local atomic structure in tetragonal pure ZrO2nanopowders

2010 ◽  
Vol 43 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Leandro M. Acuña ◽  
Diego G. Lamas ◽  
Rodolfo O. Fuentes ◽  
Ismael O. Fábregas ◽  
Márcia C. A. Fantini ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Local Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Crystallite Sizes ◽  
Exafs Study ◽  
The Difference ◽  
X Ray Absorption ◽  
Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

scholarly journals Influence of Li2CO3 addition on electrical and magnetic properties of Ni0.6Mg0.4Fe2O4

2020 ◽  
Vol 10 (03) ◽  
pp. 2050003
Author(s):  
M. R. Hassan ◽  
M. T. Islam ◽  
M. N. I. Khan
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Low Frequency ◽  
Solid State Reaction Method ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrical And Magnetic Properties ◽  
Frequency Regime ◽  
Xrd Patterns

In this research, influence of adding Li2CO3 (at 0%, 2%, 4%, 6%) on electrical and magnetic properties of [Formula: see text][Formula: see text]Fe2O4 (with 60% Ni and 40% Mg) ferrite has been studied. The samples are prepared by solid state reaction method and sintered at 1300∘C for 6[Formula: see text]h. X-ray diffraction (XRD) patterns show the samples belong to single-phase cubic structure without any impurity phase. The magnetic properties (saturation magnetization and coercivity) of the samples have been investigated by VSM and found that the higher concentration of Li2CO3 reduces the hysteresis loss. DC resistivity increases with Li2CO3 contents whereas it decreases initially and then becomes constant at lower value with temperature which indicates that the studied samples are semiconductor. The dielectric dispersion occurs at a low-frequency regime and the loss peaks are formed in a higher frequency regime, which are due to the presence of resonance between applied frequency and hopping frequency of charge carriers. Notably, the loss peaks are shifted to the lower frequency with Li2CO3 additions.

Mechanically Driven Dissolution of Sn in Near-Equiatomic Bcc FeCo

2012 ◽  
Vol 194 ◽  
pp. 187-193 ◽  
Author(s):  
J.M. Loureiro ◽  
Benilde F.O. Costa ◽  
Gerard Le Caër ◽  
Bernard Malaman
Keyword(s):  
Magnetic Field ◽  
Solid Solutions ◽  
Room Temperature ◽  
Hyperfine Magnetic Field ◽  
Ternary Alloys ◽  
119Sn Mössbauer Spectroscopy ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Powder Mixtures ◽  
X Ray

Ternary alloys, (Fe50−x/2Co50−x/2)Snx(x ≤ 33 at.%), are prepared by mechanical alloying from powder mixtures of the three elements. As-milled alloys are studied by X-ray diffraction and 57Fe and 119Sn Mössbauer spectroscopy. The solubility of Sn in near-equiatomic bcc FeCo is increased from ~0.5 at. % at equilibrium to ~20 at.% in the used milling conditions. The average 119Sn hyperfine magnetic field at room temperature is larger, for any x, than the corresponding fields in mechanically alloyed Fe-Sn solid solutions.

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