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.

Preparation and Structural Observation of Co2MnSi Heusler Alloys by Mechanical Alloying

2020 ◽  
Vol 20 (9) ◽  
pp. 5502-5505
Author(s):  
Chung-Hyo Lee
Keyword(s):  
Heat Treatment ◽  
Mechanical Alloying ◽  
Saturation Magnetization ◽  
Heusler Alloys ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Maximum Value ◽  
Heat Treated ◽  
Average Grain Size ◽  
Magnetic Dilution

A Co2MnSi Heusler alloy has been prepared by mechanical alloying (MA) method successfully using a mixture of elemental Co50Mn25Si25 powders. A two-phase mixture of amorphous phase and remaining Mn were obtained after 5 hours of MA without any evidence for the formation of Co2MnSi alloys. The saturation magnetization of MA powders decreased with MA time due to the magnetic dilution by alloying with nonmagnetic Mn and Si elements to 48 emu/g after 5 hours of MA. On the other hand, a Co2MnSi single phase was obtained by MA after 3 hours and subsequently heat treated up to 650 °C. X-ray diffraction result showed that the average grain size of Co2MnSi Heusler alloys prepared by MA for 5 hours and heat treatment to be in the range of 85 nm. The saturation magnetization of Co2MnSi Heusler alloys prepared by MA and heat treatment reached a maximum value of 112 emu/g for 5 hours MA sample. It was also observed that the coercivity of 5 hours MA sample annealed at 650 °C was fairly low value of 27 Oe.

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.

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.

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.

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.

Effect of copper incorporation on phase transformation behavior of electroless nickel–phosphorous coating and its effect on the tribological behavior

2020 ◽  
pp. 146442072098160
Author(s):  
Abhijit Biswas ◽  
Suman Kalyan Das ◽  
Prasanta Sahoo
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
Tribological Behavior ◽  
Electroless Nickel ◽  
Two Phase ◽  
Microstructural Changes ◽  
Treatment Conditions ◽  
Heat Treated ◽  
Higher Temperature ◽  
Effect Of Copper

The microstructural changes of electroless Ni–P–Cu coating at various heat-treatment conditions are investigated to understand its implications on the tribological behavior of the coating. Coatings are heat-treated at temperatures ranging between 200°C and 800 °C and for 1–4 h duration. Ni–P–Cu coatings exhibit two-phase transformations in the temperature range of 350–450 °C and the resulting microstructural changes are found to significantly affect their thermal stability and tribological attributes. Hardness of the coating doubles when heat-treated at 452 °C, due to the formation of harder Ni3P phase and crystalline NiCu. Better friction and wear performance are also noted upon heat treatment of the coating at the phase transformation regime, particularly at 400 °C. Wear mechanism is characterized by a mixed adhesive cum abrasive wear phenomena. Heat treatment at higher temperature (600 °C and above) and longer duration (4 h) results in grain coarsening phenomenon, which negatively influences the hardness and tribological characteristics of the coating. Besides, diffusion of iron from the ferrous substrate as well as greater oxide formation are noticed when the coating is heat-treated at higher temperatures and for longer durations (4 h).

Influence of Heat Treatment on Microstrudture and Mechanical Properties of AZ31B Magnesium Alloy Prepared by Solid-State Recycling

2012 ◽  
Vol 271-272 ◽  
pp. 17-20
Author(s):  
Shu Yan Wu ◽  
Ze Sheng Ji ◽  
Chun Ying Tian ◽  
Ming Zhong Wu
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Solid State ◽  
Magnesium Alloy ◽  
Static Recrystallization ◽  
Annealing Treatment ◽  
Az31b Magnesium Alloy ◽  
Heat Treated ◽  
Elongation To Failure ◽  
Strength And Ductility

This work is to study the influence of heat treatment on microstrudture and mechanical properties of AZ31B magnesium alloy prepared by solid -state recycling. AZ31B magnesium alloy chips were recycled by hot extruding. Three different heat treatments were conducted for recycled alloy. Mechanical properties and microstructure of the recycled specimen and heat treated specimen were investigated. 300°C×2h annealing specimen exhibits finer grain due to static recrystallization, and microstructure of 400°C×2h annealing specimen becomes more coarse. 300°C×2h annealing treatment improves obviously strength and ductility of recycled alloy. Ultimate tensile strength of alloy decreases and elongation to failure increases after 400°C×2h annealing. Grain size, dislocation density and bonding of chips have an effect on the elongation of recycled materials. 190°C×8h ageing has no influence on microstructure and mechanical properties of recycled alloy.

scholarly journals Feasibility of nickel extraction from Indian chromite overburden by solid state reduction and smelting route

2020 ◽  
Vol 56 (2) ◽  
pp. 229-235
Author(s):  
P. Ganesh ◽  
Dishwar Kumar ◽  
S. Agrawal ◽  
Mandal Kumar ◽  
N. Sahu ◽  
...  
Keyword(s):  
Solid State ◽  
Horizontal Tube ◽  
Low Grade ◽  
State Reduction ◽  
Nickel Extraction ◽  
Reducing Atmosphere ◽  
Chromite Overburden ◽  
Solid State Reduction ◽  
Horizontal Tube Furnace ◽  
Direct Smelting

The present work demonstrates the extraction of nickel from low-grade chromite overburden by using solid state reduction and direct smelting route. Goethite & Quartz are present as major phases whereas chromite, hematite were identified as minor phases in the mineral. Solid state reduction of pellets were carried out inside a horizontal tube furnace at 1000?C, 1200?C, 1400?C for 30, 60, 90 and 120 minutes respectively with creating reducing atmosphere. Pellets of varying basicity (i.e. 0.5, 0.6, 0.7, 0.8 and 0.9) were used directly in the EAF for smelting studies. Highest percent of nickel (2%) having ~ 91% recovery were obtained in solid state reduction route for pellets which was reduced at 1400?C for 120 minute. Similar recovery (~90%) of nickel was obtained inside the ingot (0.67% Ni ) by using pellets of 0.9 basicity through smelting route. From the present investigation, it could be concluded that the solid state reduction as well as smelting routes are feasible for the recovery of nickel from low grade chromite overburden. The production of nickel pig (low grade ferronickel) could also be feasible by smelting route.

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