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

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.

Preparation and Structural Observation of Co₂MnSi Heusler Alloys by Mechanical Alloying.

A Co₂MnSi Heusler alloy has been prepared by mechanical alloying (MA) method successfully using a mixture of elemental CoMnSi 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.

Synthesis and Magnetic Properties of Fe₂CrSi Heusler Alloys by Mechanical Alloying.

We have applied mechanical alloying (MA) to prepare nanocrystalline Fe₂CrSi Heusler alloy using a mixture of elemental FeCrSi powders. Its structural characterizaion and magnetic properties have been studied by X-ray diffraction, differential scanning calorimeter and vibrating sample magnetometer measurements. -(Fe,Cr,Si) BCC phases coupled with amorphous phase are obtained after 40 hours of MA.

Synthesis and Spark Plasma Sintering of Soft Magnetic Composite in a Fe₂O₃–Al System by Mechanical Alloying.

We have applied mechanical alloying (MA) to produce soft magnetic composite material using a mixture of elemental Fe₂O₃–Al powders. An optimal milling and sintering conditions to obtain soft magnetic α-Fe/Al₂O₃ composite with fine microstructure were investigated by X-ray diffraction, differential scanning calorimeter and vibrating sample magnetometer measurements. It is found that the average grain sizes of α-Fe in α-Fe/Al₂O₃ composite ball-milled for 5 hours is estimated to be in the range of 50 nm.

Fabrication and Magnetic Properties of Co₂MnAl Heusler Alloys by Mechanical Alloying.

We have applied mechanical alloying (MA) to produce nanocrystalline Co2MnAl Heusler alloys using a mixture of elemental Co50Mn25Al25 powders. An optimal milling and heat treatment conditions to obtain a Co2MnAl Heusler phase with fine microstructure were investigated by X-ray diffraction, differential scanning calorimeter and vibrating sample magnetometer measurements. α-(Co, Mn, Al) FCC phases coupled with amorphous phase are obtained after 3 hours of MA without any evidence for the formation of Co2MnAl alloys.

Fabrication and Spark Plasma Sintering of Magnetic alpha-Fe/MgO Nanocomposite by Mechanical Alloying.

Solid-state reduction has occurred during mechanical alloying of a mixture of Fe2O3 and Mg powders at room temperature. It is found that magnetic nanocomposite in which MgO is dispersed in alpha-Fe matrix with nano-sized grains is obtained by mechanical alloying of Fe2O3 with Mg for 30 min. Consolidation of the ball-milled powders was performed in a spark plasma sintering (SPS) machine up to 800-1000 degrees C.

Fabrication and Characterization of Thermoelectric CrSi2 Compound by Mechanical Alloying and Spark Plasma Sintering.

A mixture of elemental Cr-Si powders has been subjected to mechanical alloying (MA) at room temperature to prepare CrSi2 thermoelectric compound.The MA powders were sintered at 800-1000 °C Cunder 60 MPa using spark plasma sintering (SPS) technique. Due to the observed larger loss of Si relative Cr during ball milling, the starting composition was modified to Cr30Si70, Cr31.

Fabrication and Characterization of Thermoelectric Fe2VAl Alloy Powders by Mechanical Alloying.

A mixture of elemental Fe50V25Al25 powders has been subjected to mechanical alloying (MA) at room temperature to prepare the Heusler Fe2VAl thermoelectric alloy. Fe2VAI alloy with a grain size of 90 nm can be obtained by MA of Fe50V25Al25 powders for 60 h and subsequently annealed at 700 degrees C. Consolidation of the MA powders was performed in a spark plasma sintering (SPS) machine using graphite dies up to 900-1000 degrees C under 60 MPa.

Nanocomposite formation in haematite-Mg, Ti system induced by high-energy ball milling.

Reactant materials of haematite and Mg, Ti powders have been milled, where pure metals are used as reducing agent. It is found that nanocomposite powders in which MgO and TiO2 are dispersed in alpha-Fe matrix with nano-sized grains are obtained by MA of Fe2O3 with Mg and Ti for 30 min and 5 hours, respectively. It is suggested that the shorter MA time for the nanocomposite formation in Fe2O3-Mg is due to a larger negative heat associated with the chemical reduction of reactant materials.

Fabrication of MnSi1.73 thermoelectric material by mechanical alloying.

The effect of mechanical alloying (MA) on the formation of MnSi1.73 thermoelectric compound was investigated. Due to the observed larger loss of Si relative to Mn during MA, the starting composition of Mn-Si was modified to MnSi1.

Nanocrystalline formation in immiscible Cu-Mo system subjected to mechanical alloying.

The mechanical alloying process has been studied on the Cu-Mo system, the atomic pair of which is characterized by a positive heat of mixing of +19 kJ/mol. The EXAFS and X-ray diffraction measurements have been employed to analyze the structural changes taking place during milling. Two phases mixture of nanocrystalline fcc-Cu and bcc-Mo with a grain size of 10 nm has been formed by MA of Cu30Mo70 powders for 200 hours.

Annealing characteristics of nanostructured Cu-Fe-P alloy processed by accumulative roll-bonding.

Annealing characteristics of a nanostructured copper alloy processed by accumulative roll-bonding (ARB) were studied. A nano-grained Cu-Fe-P alloy processed by 8 cycles of the ARB was annealed at various temperatures ranging from 100 to 400 degrees C for 0.6 ks.

Annealing characteristics of nano-grained oxygen free copper processed by accumulative roll-bonding process.

Annealing characteristics of nano-grained oxygen free copper processed by accumulative roll-bonding (ARB) were studied. A nano-grained oxygen free copper fabricated by 8 cycles of the ARB was annealed at various temperatures ranging from 100 to 300 degrees C for 0.6 ks.

Fabrication of Mg2Si thermoelectric materials by mechanical alloying and spark-plasma sintering process.

A mixture of pure Mg and Si powders with an atomic ratio 2:1 has been subjected to mechanical alloying (MA) at room temperature to prepare the Mg2Si thermoelectric material. Mg2Si intermetallic compound with a grain size of 50 nm can be obtained by MA of Mg66.7Si33.