Fabrication and Characterization of Magnetic Nanocomposite Powders in Hematite-Ca System by Mechanical Alloying

2017 ◽  
Vol 753 ◽  
pp. 78-83
Author(s):  
Chung Hyo Lee
Keyword(s):  
Grain Size ◽  
Mechanical Alloying ◽  
Ball Milling ◽  
Milling Time ◽  
Magnetic Nanocomposite ◽  
State Reduction ◽  
Treatment Conditions ◽  
Average Grain Size ◽  
Solid State Reduction ◽  
Nanocomposite Powders

We have applied mechanical alloying technique to produce magnetic nanocomposite material using a mixture of Fe2O3 and Ca powders at room temperature. An optimal ball milling and heat treatment conditions to obtain magnetic α-Fe/CaO composite with fine microstructure were investigated by X-ray diffraction, scanning electron microscope and vibrating sample magnetometer measurements. We have revealed that the magnetic α-Fe /CaO nanocomposite powders can be produced by solid state reduction during ball milling. It is found that α-Fe/CaO nanocomposite powders in which CaO is dispersed in α-Fe matrix with a grain size of 45 nm are obtained by mechanical alloying of Fe2O3 with Ca for 5 hours. The saturation magnetization of ball-milled powders increases with increasing milling time and reaches to a maximum value of 65 emu/g after 7 hours of MA. The average grain size of a-Fe in 5 hours MA powders estimated by diffraction line-width are gradually decreased with increasing milling time, and tend to reach at 45 nm. The magnetic hardening due to the reduction of the α-Fe grain size by MA is also observed.

Nanocomposite Formation in the Fe3O4-M (M=Al, Ti) Systems by Mechanical Alloying

2006 ◽  
Vol 317-318 ◽  
pp. 623-628
Author(s):  
Chung Hyo Lee ◽  
Seong Hee Lee ◽  
Sang Jin Lee ◽  
Yong Ho Choa ◽  
Ji Soon Kim
Keyword(s):  
Mechanical Alloying ◽  
Chemical Reduction ◽  
Magnetic Measurement ◽  
Reduction Process ◽  
Oxide Systems ◽  
State Reduction ◽  
Average Grain Size ◽  
Metal Metal ◽  
Solid State Reduction ◽  
Nanocomposite Powders

Nanocomposite formation of metal-metal oxide systems by mechanical alloying (MA) has been investigated at room temperature. The systems we chose are the Fe3O4-M (M=Al, Ti), where pure metals are used as a reducing agent. It is found that nanocomposite powders in which Al2O3 and TiO2 are dispersed in a α-Fe matrix with nano-sized grains are obtained by MA of Fe3O4 with Al and Ti for 25 and 75 hours, respectively. It is suggested that the shorter MA time for the nanocomposite formation in Fe3O4-Al is due to a large negative heat associated with the chemical reduction of magnetite by aluminum. X-ray diffraction results show that the average grain size of α-Fe in Fe-TiO2 nanocomposite powders is in the range of 30 nm. From magnetic measurement, we can also obtain indirect information about the details of the solid-state reduction process during MA.

scholarly journals Effect of Milling Time on Microstructure, Crystallite Size and Dielectric Properties of Srtio3 Ceramic Synthesized via Mechanical Alloying Method

2011 ◽  
Vol 364 ◽  
pp. 388-392
Author(s):  
Yick Jeng Wong ◽  
Hassan Jumiah ◽  
Mansor Hashim ◽  
Swee Yin Wong ◽  
Leow Chun Yan
Keyword(s):  
Dielectric Constant ◽  
Grain Size ◽  
Dielectric Properties ◽  
Mechanical Alloying ◽  
Crystallite Size ◽  
Single Phase ◽  
Milling Time ◽  
Average Grain Size ◽  
Average Lattice ◽  
Milled Powders

SrTiO3 sample has been successfully prepared by mechanical alloying (MA) method. The effect of milling time on microstructure, crystallite size and dielectric properties of SrTiO3 were studied. The results revealed that the mean crystallite size of milled powders decreased from 84.56 to 12.87 nm with increasing milling time. However, the average lattice strain of milled powders increased from 0.2 to 0.93% with increasing milling time. A single phase SrTiO3 could not be formed with milling alone and required annealing process. A transformation of anatase-TiO2 to rutile-TiO2 was observed at 16 h of milling. After the milled powders were subjected to sintering process at 1200°C, formation of single-phase SrTiO3-type cubic (Pm-3m) perovskite structure was observed. The peak intensities of the sintered SrTiO3 samples decreased as the milling time was increased. For microstructural observations, the average grain size of the sintered SrTiO3 sample milled for 8 h showed the largest. For dielectric measurements, the dielectric constant of the sintered SrTiO3 sample milled for 8 h showed the highest among others. This could be due to the largest grain size obtained for sintered SrTiO3 sample milled for 8 h. The decrease in the grain size with increasing milling time resulted to the decrease in dielectric constant.

Decomposition and Crystallization Induced by High-Energy Ball-Milling

2007 ◽  
Vol 119 ◽  
pp. 1-4 ◽  
Author(s):  
Young Soon Kwon ◽  
Ji Soon Kim ◽  
Cheol Eeh Kim
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Ball Milling ◽  
Milling Time ◽  
High Energy ◽  
Thermally Induced ◽  
Average Grain Size ◽  
Powder Particles ◽  
Energy Ball ◽  
Decomposition Behavior

Phase transformation induced by ball-milling was studied in this work. It was found that amorphous Fe90Zr10 ribbons undergo crystallization into BCC α-Fe(Zr) under milling in an AGO-2 mill. The decomposition degree of the amorphous phase increased with increasing milling time and intensity. Analyses of samples milled at different speeds suggested that the observed crystallization is a deformation-induced process rather than a thermally induced one. In addition, the decomposition behavior of a FeSn intermetallic under ball-milling was carefully studied. Upon milling a large amount of the FeSn intermetallic decomposed into Fe5Sn3 and FeSn2, where the average grain size of the product phases stayed nearly constant with milling-time. It is suggested that the mechanically driven decomposition of FeSn results from local melting of powder particles due to high temperature pulses during ball collisions.

Mechanical Alloying Effect of Hematite and Graphite

2004 ◽  
Vol 449-452 ◽  
pp. 257-260 ◽  
Author(s):  
Chung Hyo Lee ◽  
S.H. Lee ◽  
S.Y. Chun ◽  
Sang J. Lee ◽  
Joo Sun Kim
Keyword(s):  
Solid State ◽  
Mechanical Alloying ◽  
Saturation Magnetization ◽  
Ball Mill ◽  
Room Temperature ◽  
Milling Time ◽  
Mechanochemical Reaction ◽  
Alloying Effect ◽  
State Reduction ◽  
Solid State Reduction

The mechanochemical reaction of hematite with graphite by mechanical alloying (MA) has been investigated at room temperature. The solid state reduction of hematite to Fe3O4 and FeO has been observed after 120 hours of MA by a planetary ball mill. Saturation magnetization is gradually increased with milling time up to 80 h, and then deceased after 120 h of MA, indicating the transformation of Fe3O4 into nonmagnetic FeO through further reduction. Neither the solid state reduction of Fe2O3 by graphite nor a sizable grain refinement is observed in the MA process using a horizontal ball mill.

Nanocrystalline Formation and Magnetic Properties in Fe2O3–C System by Mechanical Alloying

2021 ◽  
Vol 21 (7) ◽  
pp. 3791-3794
Author(s):  
Chung-Hyo Lee
Keyword(s):  
Heat Treatment ◽  
Solid State ◽  
Mechanical Alloying ◽  
Saturation Magnetization ◽  
Two Phase ◽  
Reaction Heat ◽  
State Reduction ◽  
Heat Treated ◽  
Average Grain Size ◽  
Solid State Reduction

The effect of mechanical alloying (MA) on the solid state reaction of hematite and graphite system with a positive reaction heat was investigated using a mixture of elemental Fe2O3–C powders. The solid state reduction of hematite to Fe3O4 has been obviously observed after 3 hours of MA by a vibrating ball mill. A two-phase mixture of Fe3O4 and remaining Fe2O3 is obtained after 5 hours of MA. Saturation magnetization gradually increases with MA time due to the formation of Fe3O4 and then reaches 23 emu/g after 5 hours of MA. In addition, a Fe3O4 single phase is obtained by MA after 3 hours and subsequently heat treated up to 700°C. X-ray diffraction result shows that the average grain size of Fe3O4 prepared by MA for 5 hours and heat treatment to be in the range of 92 nm. The saturation magnetization of Fe3O4 prepared by MA and heat treatment reaches a maximum value of 56 emu/g for 5 hours MA sample. It is also observed that the coercivity of 5 hours MA sample annealed at 700 °C is still high value of 113 Oe, suggesting that the grain growth of magnetite phase during annealing process tends to be suppressed.

Effects of Ball Milling Time on the Microstructure and Mechanical Property of Cu90Al10 Alloy

2013 ◽  
Vol 750-752 ◽  
pp. 663-666
Author(s):  
C.J. Li ◽  
G. Chen ◽  
Q. Yuan ◽  
J. Tan ◽  
L. Teng ◽  
...  
Keyword(s):  
Mechanical Property ◽  
Grain Size ◽  
Yield Strength ◽  
Mechanical Alloying ◽  
Ball Milling ◽  
Milling Time ◽  
Structural Characteristics ◽  
High Energy ◽  
Powder Particle Size ◽  
X Ray Diffraction

Nanostructured Cu90Al10 alloy powders were prepared by high energy ball milling mechanical alloying (MA). Up to 10 at.% Al could be dissolved into copper by mechanical alloying at room temperature. Effects of milling time on phase transformation, structural characteristics, and mechanical property of powders were investigated by using X-ray diffraction (XRD), Optical Microscopy (OM) and microhardness tester. The results show: with increasing the milling time, the powder particle size increased gradually, and then it tended to be homogeneous. The grain size of the alloy decreased gradually, but the yield strength increased with the extension of the ball milling. After 30h milling, the grain size reached the minimum value of 9 nm, and the yield strength obtained the maximum value of 511 MPa.

scholarly journals Synthesis and Characterization of Nanostructured WC-Co/Al Powder Prepared by Mechanical Alloying

2016 ◽  
Vol 2016 ◽  
pp. 1-6
Author(s):  
Ning Ma ◽  
Keke Zhang ◽  
Danqing Yin ◽  
Di Zhao ◽  
Zhiwei Zhu ◽  
...  
Keyword(s):  
Mechanical Alloying ◽  
Ball Milling ◽  
Milling Time ◽  
Hvof Spraying ◽  
Characterization Methods ◽  
Average Grain Size ◽  
Lower Porosity ◽  
Al Powder ◽  
Oxygen Fuel

Nanostructured WC-Co/Al powder was synthesized from WC-12Co powder and pure Al powder by mechanical alloying (MA). The morphology and microstructural evolution of WC-Co/Al powder were investigated by a series of characterization methods. The results showed that theβ-Co phase in the initial WC-12Co powder was replaced by the AlxCo phases (such as Al9Co2and Al13Co4). As the ball milling time increased, the average grain size of WC in the WC-Co/Al powder decreased firstly and then remained at a constant value of around 40 nm. The deposition behavior of powders sprayed by high velocity oxygen fuel (HVOF) spraying was investigated. During spraying, the WC-Co/Al powder had a better flattening than the WC-12Co powder without ball milling, which is beneficial to fabricate compact coatings with lower porosity.

Nanocomposite Formation in the Fe2O3-M (M=Al, Ti, Zn, Cu) Systems by Mechanical Alloying

2004 ◽  
Vol 449-452 ◽  
pp. 253-256 ◽  
Author(s):  
Chung Hyo Lee ◽  
S.H. Lee ◽  
S.Y. Chun ◽  
Sang Jin Lee ◽  
Young Soon Kwon
Keyword(s):  
Solid State ◽  
Mechanical Alloying ◽  
Saturation Magnetization ◽  
Room Temperature ◽  
Oxide Systems ◽  
State Reduction ◽  
Metal Metal ◽  
Pure Metals ◽  
Solid State Reduction ◽  
Nanocomposite Powders

Nanocomposite formation of metal-metal oxide systems by mechanical alloying (MA) has been investigated at room temperature. The systems we chose are the Fe2O3-M(M=Al,Ti,Zn,Cu), where pure metals are used as reducing agent. It is found that nanocomposite powders in which Al2O3and TiO2are dispersed in Fe matrix with nano-sized grains are obtained by mechanical alloying Fe2O3with Al and Ti, respectively. However, the reduction of Fe2O3with Cu by MA is not occurred. And the system of Fe2O3-Zn results in the formation of FeO plus ZnO after 120 h of milling. It is also shown that the magnetic evidence for the solid state reduction by mechanical alloying through changes in saturation magnetization and coercivity.

Fabrication of MoSi2 Nanocrystal by Mechanical Alloying Large Particle-Sized Starting Powders

2010 ◽  
Vol 434-435 ◽  
pp. 768-770
Author(s):  
Jun Ting Luo
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Mechanical Alloying ◽  
Powder Mixture ◽  
Large Particle ◽  
Milling Time ◽  
Average Grain Size

The MoSi2 nanocrystal was prepared by mechanical alloying (MA) large particle-sized starting powders, in which the milling time is much longer than usual MA time. It was found that the Mo-Si powder mixture mixed at stoichiometry proportion forms α-MoSi2 and β-MoSi2 in the MDR mode rather than pure α-MoSi2 in the SHS mode. The grain size of MoSi2, calculated using Scherrer′s formula, is 18nm when milled for 96h, and decreases to 12nm when further milling to 144 h. This is because that the milling balls provide enough energy to refine most of the rough crystal grain. The average grain size increased to 15nm when milled for 192 h, which indicates that further expand time could not refine the crystal grain while cause the growth of a part of the crystal grain. The particle size of MoSi2 is about 0.5μm when milled for 96 h and the agglomerating phenomenon is severe. The particle size of MoSi2 decreases to 0.4μm and releases the agglomerating phenomenon with the milling time for 144 h.

LiNiO2 Thin Films Fabricated by Diffusion of Li on Ni Tapes

2007 ◽  
Vol 336-338 ◽  
pp. 505-508
Author(s):  
Cheol Jin Kim ◽  
In Sup Ahn ◽  
Kwon Koo Cho ◽  
Sung Gap Lee ◽  
Jun Ki Chung
Keyword(s):  
Thin Films ◽  
Heat Treatment ◽  
Grain Size ◽  
Sol Gel ◽  
Surface Oxidation ◽  
Cold Isostatic Pressing ◽  
Tube Furnace ◽  
Treatment Conditions ◽  
Average Grain Size ◽  
Cold Rolling And Annealing

LiNiO2 thin films for the application of cathode of the rechargeable battery were fabricated by Li ion diffusion on the surface oxidized NiO layer. Bi-axially textured Ni-tapes with 50 ~ 80 μm thickness were fabricated using cold rolling and annealing of Ni-rod prepared by cold isostatic pressing of Ni powder. Surface oxidation of Ni-tapes were conducted using tube furnace or line-focused infrared heater at 700 °C for 150 sec in flowing oxygen atmosphere, resulted in NiO layer with thickness of 400 and 800 μm, respectively. After Li was deposited on the NiO layer by thermal evaporation, LiNiO2 was formed by Li diffusion through the NiO layer during subsequent heat treatment using IR heater with various heat treatment conditions. IR-heating resulted in the smoother surface and finer grain size of NiO and LiNiO2 layer compared to the tube-furnace heating. The average grain size of LiNiO2 layer was 0.5~1 μm, which is much smaller than that of sol-gel processed LiNiO2. The reacted LiNiO2 region showed homogeneous composition throughout the thickness and did not show any noticeable defects frequently found in the solid state reacted LiNiO2, but crack and delamination between the reacted LiNiO2 and Ni occurred as the reaction time increased above 4hrs.

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