Structure and Magnetic Property Correlation in Nanocrystalline SmFe9

1999 ◽  
Vol 581 ◽  
Author(s):  
C. Djega-Mariadassou ◽  
L. Bessais
Keyword(s):  
Magnetic Property ◽  
Curie Temperature ◽  
Hyperfine Field ◽  
Interatomic Distance ◽  
Hexagonal Phase ◽  
Rietveld Analysis ◽  
High Energy ◽  
M6ssbauer Spectroscopy ◽  
Energy Ball ◽  
Negative Exchange

ABSTRACTSmxFe100−x samples with x = 7.6, 10.5 and 12.5 were prepared by high energy ball-milling and subsequent annealing at various temperature Ta, 600 < Ta < 1200 °C. Rietveld analysis coupled to Curie temperature measurements and M6ssbauer spectroscopy revealed for 600 < Ta < 900 °C an hexagonal phase P6/mmm derived from TbCu7 with stoichiometry SmFe9. At Ta > 900 °C, the ordered R3m Sm2Fe17 structure is obtained so that SmFe9 appears as the out-of-equilibrium precursor of Sm2Fe17. The Curie temperature and hyperfine field augmentation found for SmFe9 results from an increase of the interatomic distance in the Fe-Fe dumbbell, responsible for a reduction of the negative exchange interaction.

Effect of Ball Milling on Magnetic Properties of Nb Substituted R2Fe16Nb1 (R: Gd and Er) Alloys

2013 ◽  
Vol 1516 ◽  
pp. 227-231
Author(s):  
B. K. Rai ◽  
S. R. Mishra ◽  
S. Khanra ◽  
K. Ghosh
Keyword(s):  
Magnetic Properties ◽  
Curie Temperature ◽  
Saturation Magnetization ◽  
Ball Milling ◽  
Grain Refinement ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Lattice Expansion ◽  
Energy Ball

AbstractIn this work, we report the effect of high energy ball milling (HEBM) on Nb doped R2Fe16Nb1 (R= Gd, Er) compounds. The focus of the work is to bring enhancement in magnetic properties of R2Fe17 (2:17) compounds with the ball milling. Specifically, we find that the ball milling increases saturation magnetization, coercivity, and Curie temperature. The increase in the magnetization and Curie temperature upon ball milling is related to the lattice expansion and microstrains while the increase in coercivity is related to the grain refinement.

Microstructure characterization of nanocrystalline ZrSiO4synthesized by ball-milling and high-temperature annealing

2005 ◽  
Vol 38 (6) ◽  
pp. 951-957 ◽  
Author(s):  
S. K. Pradhan ◽  
M. Sinha
Keyword(s):  
Ball Milling ◽  
Rietveld Analysis ◽  
High Energy ◽  
Microstructure Characterization ◽  
Energy Ball ◽  
Kinetics Of ◽  
Zircon Particles ◽  
Colour Gradient ◽  
Zircon Phase

Microstructure characterization and phase transformation kinetics of a high-energy ball-milled and post-annealed stoichiometric (1:1 mol%)m-ZrO2and amorphous (a-) SiO2powder mixture have been investigated by Rietveld analysis of X-ray powder diffraction data. The experimental results reveal that the ball-milling of stoichiometric powder results in the formation ofc-ZrO2/t-PSZ phases only. The ZrSiO4phase was not found to form even after 30 h of milling. However, an almost stoichiometric ZrSiO4(commercially known as zircon) phase is found to form even when a sample that was ball-milled for 5 min was post-annealed at 1473 K for 1 h. It appears that the intermediatet-PSZ phase plays an important role in zircon phase formation. The content of ZrSiO4phase increases very sharply within 15 min of milling and remains almost unchanged after 30 h of ball-milling. It is also found that nanocrystalline zircon particles are almost free from lattice strain. Contamination by an α-Fe2O3phase from the milling media results in a colour gradient (white to reddish) in the nanocrystalline ZrSiO4phase.

Phase transformation kinetic study and microstructure characterization of ball-milledm-ZrO2–10 mol%a-TiO2by Rietveld method

2003 ◽  
Vol 36 (2) ◽  
pp. 260-268 ◽  
Author(s):  
H. Dutta ◽  
S. K. Manik ◽  
S. K. Pradhan
Keyword(s):  
Particle Size ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Molar Fraction ◽  
Rietveld Analysis ◽  
High Energy ◽  
Transformation Kinetic ◽  
Cubic Phase ◽  
Milled Sample ◽  
Energy Ball

High-energy ball milling of a monoclinic ZrO2–10 mol% anatase TiO2mixture results in the formation of a nanocrystalline cubic ZrO2polymorphic phase with equimolar fraction of the starting materials. The cubic phase is presumed to have formed from them-ZrO2solid solution based on the (001) plane of them-ZrO2phase. In the course of milling, the most dense (111) plane of the cubic lattice became parallel to the most dense (\bar{1}11) plane of the monoclinic lattice due to an orientation effect. Annealing of a 12 h milled sample at 773, 873 and 973 K for 1 h results in almost complete transformation of them-ZrO2to thec-ZrO2phase. At 1273 K annealing temperature (1 h), the nanocrystalline sample decomposed into individual starting phases. This suggests that the cubic phase is a metastable one and its stability depends on particle size as well as the working temperature. Formation of the cubic phase at such a low temperature using anatase TiO2as a phase stabilizer has not been reported previously. The microstructures of the unmilled, all the ball-milled and the annealed samples have been characterized by employing Rietveld's X-ray powder structure refinement methodology. The particle size, root mean square (r.m.s.) lattice strain, lattice parameters, molar fraction,etc., of individual phases have been estimated from Rietveld analysis and are utilized to interpret the results.

TEM study of ball-milled Ni-Ta alloy containing WC inclusions

1989 ◽  
Vol 47 ◽  
pp. 678-679
Author(s):  
N. Merk ◽  
L. E. Tanner
Keyword(s):  
Hexagonal Phase ◽  
High Energy ◽  
Planetary Mill ◽  
Atomic Scale ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
Energy Ball ◽  
Container Material ◽  
State Amorphization ◽  
Milled Powders

High energy ball-milling of metallic powders is used extensively to achieve structural refinement. In recent years it has been found that cold-milling can induce transformations to highly metastable phases.In particular, the elemental mixing at the atomic-scale in certain systems may eventually lead to solid-state amorphization reactions (SSAR) after short periods of time. A problem that often arises in using this technique is contamination of the product from the grinding balls and container material.In this note we describe such a development in the microstructures that evolve during SSAR of a mixture of 75 atm% Ni and 25 atm% Ta high-purity powders processed for 17h in a planetary mill using WC + Co balls and container. The average composition of the ball-milled powders determined by EDS-analysis in a SEM was Ni75Ta25. X-ray diffraction confirmed the formation of an amorphous phase and also revealed the presence of sharp crystalline peaks identified as WC hexagonal phase (a=0.291 nm and c=0.283 nm); no detectable crystalline peaks from the initial Ni or Ta powders were observed. For TEM observations, small quantities of the ball-milled powders were embedded in epoxy and subsequently sectioned with a diamond knife using a Dupont-6000 ultramicrotome.

scholarly journals Transformation of Goethite to Hematite Nanocrystallines by High Energy Ball Milling

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
O. M. Lemine
Keyword(s):  
Ball Milling ◽  
Raw Materials ◽  
Rietveld Analysis ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Mechanochemical Reaction ◽  
Phase Identification ◽  
X Ray Diffraction ◽  
Direct Transformation ◽  
Energy Ball

α-Fe2O3nanocrystallines were prepared by direct transformation via high energy ball milling treatment forα-FeOOH powder. X-ray diffraction, Rietveld analysis, TEM, and vibrating sample magnetometer (VSM) are used to characterize the samples obtained after several milling times. Phase identification using Rietveld analysis showed that the goethite is transformed to hematite nanocrystalline after 40 hours of milling. HRTEM confirm that the obtained phase is mostly a single-crystal structure. This result suggested that the mechanochemical reaction is an efficient way to prepare some iron oxides nanocrystallines from raw materials which are abundant in the nature. The mechanism of the formation of hematite is discussed in text.

Sn-Substituted LaNi5 Alloys For Metal Hydride Electrodes

1995 ◽  
Vol 393 ◽  
Author(s):  
Margot L. Wasz ◽  
Ricardo B. Schwarz ◽  
Supramaniam Srinivasan ◽  
M. P. Sridhar Kumar
Keyword(s):  
Hydrogen Storage ◽  
Mechanical Alloying ◽  
Storage Capacity ◽  
Rietveld Analysis ◽  
Plateau Pressure ◽  
High Energy ◽  
X Ray Diffraction ◽  
Hydrogen Storage Capacity ◽  
Energy Ball ◽  
Tin Content

ABSTRACTOur research examines the efficacy of tin additions to LaNi5 in improving the hydrogen storage capacity of the material during charging/discharging. Alloys were prepared using high energy ball milling (mechanical alloying), a technique superior to arc casting for alloying elements with a wide disparity in melting points. Characterization by x-ray diffraction and Rietveld analysis shows that tin preferentially occupies the Ni(3g) sites in the LaNi5 structure, and the unit cell volume increases linearly with tin content to the maximum tin solubility of 7.33 atomic percent (LaNi4.56Sn0.44). We found that powders prepared by mechanical alloying and not exposed to air require no activation to induce hydrogen absorption. The hydrogen storage capacity in the gas and electrochemical phase was measured as a function of tin content. We found that with increasing tin, the plateau pressure decreases logarithmically, whereas the hydrogen storage capacity decreases linearly.

Ball milling-induced pyrochlore-to-tungsten bronze phase transition in RbNbWO6

2009 ◽  
Vol 24 (6) ◽  
pp. 2035-2041
Author(s):  
Janete E. Zorzi ◽  
Cintia L.G. de Amorim ◽  
Raquel Milani ◽  
Carlos A. Figueroa ◽  
J.A.H. da Jornada ◽  
...  
Keyword(s):  
Ball Milling ◽  
Structural Model ◽  
Hexagonal Phase ◽  
Tungsten Bronze ◽  
Pyrochlore Structure ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Bravais Lattice ◽  
Tungsten Bronze Structure ◽  
Energy Ball

A set of Bragg peaks consistent with a hexagonal Bravais lattice was observed in the x-ray powder diffraction pattern of cubic pyrochlore rubidium tungstoniobate (RbNbWO6) subjected to high-energy ball milling. The calculated lattice parameters for this hexagonal phase are similar to those of compounds with tungsten bronze structure. In fact, the powder pattern of the hexagonal phase could be refined with a structural model based on the tungsten bronze structure. The hexagonal phase produced by high-energy ball milling of RbNbWO6 transforms back to the pyrochlore structure upon heating to 773 K in air. A similar phase was obtained by ball milling the mixture RbNbWO6 + WO3, but, in this case, the stoichiometric hexagonal tungsten bronze compound thus obtained remained stable up to 1273 K.

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