Preparation of Al-Fe-V-Si Nanocrystalline Powders by Double Mechanical Alloying

2000 ◽  
Vol 331-337 ◽  
pp. 1225-1230 ◽  
Author(s):  
L.J. Zheng ◽  
J.X. Lin ◽  
B.S. Li ◽  
B.J. Zhang ◽  
M.K. Tseng
Keyword(s):  
Mechanical Alloying ◽  
Nanocrystalline Powders

Obtaining of the Ir-Al Nanocrystalline Powders by Mechanical Alloying

2011 ◽  
Vol 672 ◽  
pp. 171-174
Author(s):  
Ionel Chicinaş ◽  
P. Cârlan ◽  
Florin Popa ◽  
Virgiliu Călin Prică ◽  
Lidia Adriana Sorcoi
Keyword(s):  
Mechanical Alloying ◽  
Particle Morphology ◽  
High Energy ◽  
Atomic Ratio ◽  
Planetary Mill ◽  
Nanocrystalline Powders ◽  
Alloy Formation ◽  
X Ray Diffraction ◽  
Chemical Homogeneity ◽  
Diffraction Patterns

The Ir-Al powder in the 1:1 atomic ratio was obtained by high energy mechanical alloying in a Pulverisette 4 Fritch planetary mill. The final product was obtained after 28 h of milling in argon atmosphere. Alloy formation was investigated by X-ray diffraction. After 4 h of milling the new structure of IrAl compound is found in the diffraction patterns. The obtained powders are nanocrystalline with a mean crystallite size of 11 nm after 28 h of milling. The particle morphology and the chemical homogeneity were studied using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDX). It was found that the obtained compound present large particles composed by smaller one.

Mechanically Driven Alloying and Magnetic Properties in Immiscible Mn80Bi20 Nanocrystalline Powders

2013 ◽  
Vol 873 ◽  
pp. 217-220
Author(s):  
Min Xu ◽  
Qun Jiao Wang
Keyword(s):  
Magnetic Properties ◽  
Mechanical Alloying ◽  
Saturation Magnetization ◽  
Ball Milling ◽  
Solid Solubility ◽  
Milling Time ◽  
Early Stage ◽  
Nanocrystalline Powders ◽  
X Ray Diffraction ◽  
X Ray

The paper has described the formation of nanocrystalline Mn80Bi20powders by mechanical alloying and studied the changes of structure and magnetic properties of the powders during the process of ball milling by using X-ray diffraction and saturation magnetization σsmeasurements. The solid solubility of bismuth in manganese increases with milling time and tends to a stable value after 80h milling. The σsof Mn80Bi20increases abruptly with milling time at the early stage and begins to decrease after 15h. At the time of 15h, the σsreaches a maximum, which is about 7Am2/kg. The result shows an interesting information that the antiferromagnetic Mn and the diamagnetic Bi produce ferromagnetic Mn80Bi20in process of mechanical alloying.

Nanocomposite Bi(Sb)Te(Se) Materials by Cryogenic Mechanical Alloying and Optimized High Pressure Hot-pressing

2012 ◽  
Vol 1456 ◽  
Author(s):  
Tsung-ta E. Chan ◽  
Rama Venkatasubramanian ◽  
James M. LeBeau ◽  
Peter Thomas ◽  
Judy Stuart ◽  
...  
Keyword(s):  
Mechanical Alloying ◽  
Hot Pressing ◽  
High Energy ◽  
Structural Features ◽  
Milling Process ◽  
Nanocrystalline Powders ◽  
Full Density ◽  
Seebeck Coefficients ◽  
The Matrix ◽  
Cryogenic Process

ABSTRACTNanocomposite Bi2Te3 based alloys are attractive for their potentially high thermoelectric figure-of-merit (ZT) around room temperature. The nano-scale structural features embedded in the matrix provide more scattering of phonons and can thus reduce the lattice thermal conductivity. To further take advantage of such nanocomposite structures, we focus on the development of nanocrystalline Bi(Sb)Te(Se) powders by high energy cryogenic mechanical alloying followed by an optimized hot pressing process. This approach is shown to successfully produce Bi(Sb)Te(Se) alloy powders with grain size averaging about 9 nm for n-type BiTe(Se) and about 16 nm for p-type Bi(Sb)Te respectively. This cryogenic process offers much less milling time and prevents thermally activated contamination or imperfections from being introduced during the milling process. The nanocrystalline powders are then compacted at optimized pressures and temperatures to achieve full density compactions and preserve the grain sizes effectively. The resulting nano-bulk materials have optimal Seebeck coefficients and are expected to have improved ZT. Thermoelectric properties and microstructure studies by X-ray diffraction and transmission electron microscopy will also be presented and discussed.

Different Cr Contents in Nanostructured Fe-Ni-Cr Alloys Prepared by Mechanical Alloying

2012 ◽  
Vol 531-532 ◽  
pp. 437-441 ◽  
Author(s):  
Qi He ◽  
Tao Liu ◽  
Jian Liang Xie
Keyword(s):  
Particle Size ◽  
Mechanical Alloying ◽  
Ball Milling ◽  
Lattice Distortion ◽  
Milling Time ◽  
Nanocrystalline Powders ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ball Milling Time ◽  
Scanning Electron

Fe-Ni-Cr alloy powders with the different components were prepared by Mechanical Alloying (MA). The phase structure, grain size, micro-strain and lattice distortion were determined with X-ray diffraction. The morphology and particle size of the powders were observed and analyzed using a field emission scanning electron microscopy. The results showed that the Fe-Ni-Cr nanocrystalline powders could be obtained by MA. The ball milling time could be reduced with increasing amount of Cr, resulting the formation of Fe-Ni-Cr powders. With the increasing amount of Cr, the speed of Ni diffusion to Fe lattice approaching saturation became more rapid. The particle size got smaller as the ball milling went further; the extent of micro-strain and distortion of lattice intensified; the solid solubility of Ni and Cr in Fe was increased. Finally the super-saturated solid solution of Fe was obtained.

SYNTHESIS OF AN IONIC LIQUID-BASED MAGNETORHEOLOGICAL FLUID DISPERSING Fe84Nb3V4B9 NANOCRYSTALLINE POWDERS

2010 ◽  
Vol 24 (10) ◽  
pp. 1227-1234 ◽  
Author(s):  
LINGFEI CAO ◽  
HYUNSEO PARK ◽  
GJERGJ DODBIBA ◽  
TOYOHISA FUJITA
Keyword(s):  
Ionic Liquid ◽  
Mechanical Alloying ◽  
Nanocrystalline Powders ◽  
Magnetic Flux Density ◽  
Magnetic Clusters ◽  
Mr Fluid ◽  
Structure Morphology ◽  
Average Grain Size ◽  
Digital Microscope ◽  
20 Nm

A new magnetorheological (MR) fluid was synthesized by dispersing Fe 84 Nb 3 V 4 B 9 nanocrystalline powders in a nonvolatile ionic liquid (N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate), which is stable from 282K to 573K. The structure, morphology, and magnetization of Fe 84 Nb 3 V 4 B 9 nanocrystalline powders prepared by mechanical alloying were analyzed by using an X-ray diffractometer (XRD), a vibrating sample magnetometer (VSM), and a scanning electron microscopy (SEM), respectively. The magnetic clusters of the synthesized MR fluid were observed by using a digital microscope, and its MR properties were measured by using a cone-plate type viscometer. The experimental results showed that Fe 84 Nb 3 V 4 B 9 nanocrystalline powders with an average grain size of 10–20 nm can be prepared by mechanical alloying. The MR fluid is magnetic-field-responsive, behaves like non-Newtonian fluids, and its magnetorheological properties are influenced by the applied magnetic flux density and the width of magnetic clusters.

Effect of Hydrogen on Formation of Fe-Al Nanoparticles by Mechanical Milling

2014 ◽  
Vol 29 ◽  
pp. 23-28 ◽  
Author(s):  
František Lukáč ◽  
Jakub Čížek ◽  
Yvonna Jirásková ◽  
Ivan Procházka ◽  
Marian Vlček ◽  
...  
Keyword(s):  
Mechanical Alloying ◽  
High Energy ◽  
Hydrogen Atmosphere ◽  
Nanocrystalline Powders ◽  
Iron Nitride ◽  
Nominal Composition ◽  
Al Nanoparticles ◽  
Air Atmosphere ◽  
Iron Aluminum ◽  
High Concentrations

Nanocrystalline powders of iron aluminum alloy of the Fe82Al18 nominal composition were prepared under air, hydrogen and nitrogen atmospheres from the Fe and Al elemental powders by mechanical alloying and also from the conventionally cast Fe82Al18 alloy by the high-energy ball milling. The intensive plastic deformation during high-energy mechanical treatment has introduced high concentrations of open volume defects and contributed to a rapid decrease in the crystallite size down to a nanoscopic range.The hydrogen atmosphere was found to be the most efficient for the Fe-Al mechanical alloying since it has resulted into the fully alloyed Fe82Al18 after 30 h of milling. On the other hand, the nitrogen and air atmosphere have slightly prevented mechanical alloying and after the same milling time the pure iron particles were still detected in the powder mixtures. This partial suppression of the mechanical alloying process is explained by a formation of thin iron nitride and/or oxide layers on the surface of Fe particles preventing mutual inter-diffusion of Fe and Al atoms.

Enhanced Thermoelectric Figure-of-merit at Room Temperature in Bulk Bi(Sb)Te(Se) With Grain Size of ∼100nm

2013 ◽  
Vol 1543 ◽  
pp. 93-98 ◽  
Author(s):  
Tsung-ta E. Chan ◽  
Rama Venkatasubramanian ◽  
James M. LeBeau ◽  
Peter Thomas ◽  
Judy Stuart ◽  
...  
Keyword(s):  
Grain Size ◽  
Mechanical Alloying ◽  
Grain Boundaries ◽  
Figure Of Merit ◽  
Room Temperature ◽  
High Energy ◽  
High Density ◽  
Nanocrystalline Powders ◽  
Bulk Materials ◽  
P Type

ABSTRACTGrain boundaries are known to be able to impede phonon transport in the material. In the thermoelectric application, this phenomenon could help improve the figure-of-merit (ZT) and enhance the thermal to electrical conversion. Bi2Te3 based alloys are renowned for their high ZT around room temperature but still need improvements, in both n- and p-type materials, for the resulting power generation devices to be more competitive. To implement high density of grain boundaries into the bulk materials, a bottom-up approach is employed in this work: consolidations of nanocrystalline powders into bulk disks. Nanocrystalline powders are developed by high energy cryogenic mechanical alloying that produces Bi(Sb)Te(Se) alloy powders with grain size in the range of 7 to 14 nm, which is about 25% finer compared to room temperature mechanical alloying. High density of grain boundaries are preserved from the powders to the bulk materials through optimized high pressure hot pressing. The consolidated bulk materials have been characterized by X-ray diffraction and transmission electron microscope for their composition and microstructure. They mainly consist of grains in the scale of 100 nm with some distributions of finer grains in both types of materials. Preliminary transport property measurements show that the thermal conductivity is significantly reduced at and around room temperature: about 0.65 W/m-K for the n-type BiTe(Se) and 0.85 W/m-K for the p-type Bi(Sb)Te, which are attributed to increased phonon scattering provided by the nanostructure and therefore enhanced ZT about 1.35 for the n-type and 1.21 for the p-type are observed. Detailed transport properties, such as the electrical resistivity, Seebeck coefficient and power factor as well as the resulting ZT as a function of temperature will be described.

The Magnetic and Photo-Catalytic Properties of Fe Doped TiO2 Nanocrystalline Powder Synthesized by Mechanical Alloying

2007 ◽  
Vol 534-536 ◽  
pp. 229-232 ◽  
Author(s):  
Young Rang Uhm ◽  
S.H. Woo ◽  
Min Ku Lee ◽  
Chang Kyu Rhee
Keyword(s):  
Mechanical Alloying ◽  
Paramagnetic Phase ◽  
Uv Absorption ◽  
Spherical Particles ◽  
Nanocrystalline Powders ◽  
Ferromagnetic Phase ◽  
Nanocrystalline Powder ◽  
Mechanically Alloyed ◽  
Doped Tio2 ◽  
Average Grain Size

Fe-doped TiO2 nanocrystalline powders were prepared by mechanical alloying (MA) by varying Fe contents up to 8.0 wt.%. The TEM analyses were carried out to clarify morphologies and position of Fe within the mechanically alloyed powders. The Fe-doped powder consisted of spherical particles, and the average grain size was less than 10 nm. For the Fe-doped TiO2, the color of the powders changed from white to bright yellow with increasing concentration of Fe. The UVvis absorption showed that the UV absorption for the Fe-doped powder shifted to a longer wavelength (red shift) and the photo-efficiency was enhanced. The absorption threshold depends on the concentration of nano-sized Fe dopant. Mössbauer spectrum for 4 wt.% Fe showed the ferromagnetic phase (sextet) and paramagnetic phase (doublet). However, the only paramagnetic phase (doublet) was seen for 8 wt.% Fe. As the Fe concentration increased up to 4 wt.%, the UV-vis absorption and the magnetization were increased. The beneficial effect of Fe doping for photocatalysis and ferromagnetism was observed at the critical dopant concentration of 4 wt.%. Based on the UV absorption and magnetization, the dopant level was localized to the valence band of TiO2.

High-coercivity Nd-Fe-B Powders Obtained by High-Temperature Milling

2014 ◽  
Vol 59 (1) ◽  
pp. 47-50 ◽  
Author(s):  
W. Kaszuwara ◽  
B. Michalski ◽  
P. Orlowski
Keyword(s):  
High Temperature ◽  
Mechanical Alloying ◽  
Mechanical Milling ◽  
Room Temperature ◽  
The Other ◽  
Nanocrystalline Powders ◽  
High Coercivity ◽  
Milling Temperature ◽  
Constituent Elements ◽  
Hard Magnetic Properties

Abstract The possibility of employing high temperature milling (600°C) for the production of highly coercive Nd-Fe-B powders was examined. The materials were the Nd12Fe82B6, alloy which was subjected to mechanical milling and the powders of the constituent elements of this alloy which were processed by mechanical alloying. The processes were conducted in the two variants: the first variant consisted of mechanical milling performed at a high temperature which was maintained during the entire process, and the other variant included preliminary milling carried out at room temperature and then the milling temperature was increased. All the processes gave nanocrystalline powders with hard magnetic properties. The powders produced by mechanical milling had better properties than those produced by mechanical] alloying as they were more homogeneous and contained smaller amounts of the α-Fe phase.

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