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.

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 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.

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.

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.

Investigation on the Reduction of Ilmenite at Lower Temperatures

2016 ◽  
Vol 852 ◽  
pp. 573-578
Author(s):  
Min Chen ◽  
Xuan Xiao
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Thermogravimetric Analysis ◽  
Chemical Reaction ◽  
Reduction Rate ◽  
Reduction Process ◽  
State Reduction ◽  
Solid State Reduction ◽  
Main Impurity

The solid state reduction of ilmenite was studied using thermogravimetric analysis by a combination of XRD, SEM& EDS methods. Results showed that MgTiO3 was the main impurity and influenced the reduction process of ilmenite. When the temperature was below 1000°C, reduction was controlled by the chemical reaction and the activation energy was 163 kJ/mol. Pretreatment of milling accelerated the solid reduction rate.

scholarly journals Reduction behavior of iron in the red mud

2021 ◽  
pp. 39-39
Author(s):  
S. Eray ◽  
E. Keskinkilic ◽  
Y.A. Topkaya ◽  
A. Geveci
Keyword(s):  
Solid State ◽  
Red Mud ◽  
Iron Reduction ◽  
Bauxite Residue ◽  
Reduction Process ◽  
Mineralogical Composition ◽  
Project Work ◽  
State Reduction ◽  
Solid State Reduction ◽  
High Degree

Red mud or bauxite residue contains significant quantities of industrial metals such as Fe, Al and Ti, and rare earths such as Sc, Ce, and La. The authors performed a laboratory-scale project work dealing with stepwise recovery of valuable elements from two bauxite residues, namely Iranian red mud (IRM) and Turkish red mud (TRM). In the first stage, it was tried to recover iron which is present in large quantities in red mud. Two different methods have been investigated for this purpose: 1) solid state reduction followed by wet magnetic separation, 2) smelting. In the scope of this paper, some results of pyrometallurgical part of this project are presented. According to solid-state reduction experiments, it was found that more excess coal was needed for IRM (35%) than TRM (15%) to maximize iron reduction. Temperature had significant effect on the reduction process and metallization increased from about 70% to about 95% when the temperature was raised from 1000 to 1200?C. Metallization degree was reported to be slightly higher for IRM (96.2%) than TRM (94.1%). The results demonstrated that a high degree of iron metallization can be achieved regardless of the chemical and mineralogical composition of the bauxite residue sample.

New Developments in NdFeB-Based Permanent Magnets

2012 ◽  
Vol 510-511 ◽  
pp. 1-8 ◽  
Author(s):  
Zhong Wu Liu
Keyword(s):  
Magnetic Particles ◽  
Permanent Magnets ◽  
Chemical Reduction ◽  
Reduction Process ◽  
Nanocrystalline Powders ◽  
Sintered Magnet ◽  
Energy Product ◽  
Plasma Sintering ◽  
Co Precipitation ◽  
Nanocomposite Powders

NdFeB based alloys have been used as permanent magnets for almost thirty years. The recent researches aim at optimizing the composition, microstructure and properties, reducing cost, and developing new processes. The demand for sintered magnet is increasing. Efforts are directed towards improving properties by controlling grain boundary diffusion, minimizing the rare earth (RE) content and also improving production yield. As for bonded magnets, to enhance remanence and energy product, nanocrystalline powders are employed. High thermal stability has been realized by mixing NdFeB with hard ferrite powders. For nanocrystalline and nanocomposite NdFeB based alloys, both compositional modification and microstructural optimization have been carried out. New approaches have also been proposed to prepare NdFeB magnets with idea structure. Surfactant assisted ball milling is a good top-down method to obtain nanosized hard magnetic particles and anisotropic nanoflakes. Synthesis of NdFeB nanoparticles and NdFeB/Fe (Co) nanocomposite powders by bottom-up techniques, such as chemical reduction process and co-precipitation, has been successful very recently. To assemble nanocrystalline NdFeB powders or nanoparticles into bulk magnets, various novel consolidation processes including spark plasma sintering and high velocity press have been employed. Hot deformation can be selected as the process to achieve anisotropy in nanocrystalline magnets.

Flowery Ni Microcrystals Consisting of Star-shaped Nanorods: Facile Synthesis, Formation Mechanism and Magnetic Properties

2011 ◽  
Vol 64 (11) ◽  
pp. 1494 ◽  
Author(s):  
Hao Li ◽  
Jinyun Liao ◽  
Zhen Jin ◽  
Xibin Zhang ◽  
Xiuxian Lu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Formation Mechanism ◽  
Quantum Interference ◽  
Chemical Reduction ◽  
Magnetic Measurement ◽  
Reduction Process ◽  
Cubic Phase ◽  
X Ray ◽  
Scanning Electron

Flowerlike Ni microcrystals composed of star-shaped Ni nanorods with a diameter of ~200 nm were fabricated by a facile chemical reduction process, in which ethylenediamine tetraacetic acid sodium (EDTA) was used as complexant to assist in the formation of the flowery shape of the sample. The products were characterized by X-ray diffractometer, scanning electron microscopy, energy-dispersive X-ray spectroscopy and superconducting quantum interference device magnetometer. Scanning electron microscopy images indicated the typical size of the flowery Ni microcrystals was 2–3 μm and the length of the star-shaped Ni nanorods was in the hundreds of nanometers up to micron scale. The X-ray diffraction pattern showed the Ni microcrystals were present in the face-centred cubic phase and magnetic measurement results demonstrated the greatly enhanced coercivity of the sample (168.5 Oe) at room temperature. Based on the evolution of the structure and the morphology of products with increasing reaction time, a possible formation mechanism was proposed to illustrate the growth of the flower-like Ni architecture.

Quasiperiodic interfaces: HREM observations of grain and phase boundaries

1990 ◽  
Vol 48 (4) ◽  
pp. 332-333
Author(s):  
K. L. Merkle
Keyword(s):  
Atomic Structure ◽  
Direct Determination ◽  
Lattice Parameter ◽  
Atomic Scale ◽  
Misfit Dislocations ◽  
Oxide Systems ◽  
Atomic Structures ◽  
Periodic Arrays ◽  
Parameter Ratio ◽  
Metal Metal

The atomic structures of internal interfaces have recently received considerable attention, not only because of their importance in determining many materials properties, but also because the atomic structure of many interfaces has become accessible to direct atomic-scale observation by modem HREM instruments. In this communication, several interface structures are examined by HREM in terms of their structural periodicities along the interface.It is well known that heterophase boundaries are generally formed by two low-index planes. Often, as is the case in many fcc metal/metal and metal/metal-oxide systems, low energy boundaries form in the cube-on-cube orientation on (111). Since the lattice parameter ratio between the two materials generally is not a rational number, such boundaries are incommensurate. Therefore, even though periodic arrays of misfit dislocations have been observed by TEM techniques for numerous heterophase systems, such interfaces are quasiperiodic on an atomic scale. Interfaces with misfit dislocations are semicoherent, where atomically well-matched regions alternate with regions of misfit. When the misfit is large, misfit localization is often difficult to detect, and direct determination of the atomic structure of the interface from HREM alone, may not be possible.

Sign in / Sign up

Export Citation Format

Share Document