Fe_(75)Zr_3Si_(13)B_9 magnetic materials prepared by spark plasma sintering

Fe75Zr3Si13B9 magnetic amorphous powders were fabricated by mechanical alloying. Bulk amorphous and nanocrystalline alloys with 20 mm in diameter and 7 mm in height were fabricated by the spark plasma sintering technology at different sintering temperatures. The phase composition, glass transition temperature （Tg）, onset crystallization temperature （Tx）, peak temperature （Tp） and super-cooled liquid region （ΔTx） of Fe75Zr3Si13B9 amorphous powders were analyzed by X-ray diffraction （XRD） and differential scanning calorimetry （DSC）. The phase transition, microstructure, mechanical properties and magnetic performance of the bulk alloys were discussed with X-ray diffractometer, scanning electron microscope （SEM）, Gleeble 3500 and vibration sample magnetometer （VSM）, respectively. It is found that with the increase in the sintering temperature at the pressure of 500 MPa, the density, compressive strength, micro-hardness and saturation magnetization of the sintering samples improved significantly, the amorphous phase began to crystallize gradually. Finally, the desirable amorphous and nanocrystalline magnetic materials at the sintering temperature of 863.15 K and the pressure of 500 MPa have a density of 6.9325 g/cm3, a compressive strength of 1140.28 MPa and a saturation magnetization of 1.28 T.

Structure and magnetic properties of RFe_7Mn_4Ti compounds with R=Y, Tb, Dy,Ho, and Er

The effect of Mn substitution for partial Fe in RFe 11Ti on structure and magnetic properties of compounds was researched. RFe 7Mn 4Ti samples (R=Y,Tb,Dy,Ho,Er) were prepared by means of vacuum arc-melting and subsequent vacuum annealing. The structure and magnetic properties of RFe 7Mn 4Ti compounds were investigated by X-ray powder diffraction and magnetic measurements. The following conclusions were obtained: all the RFe tMn 4Ti compounds crystallize in the ThMn 12-type structure. The lattice constants and the unit-cell volume changed with the increase of atomic number for R=Y, Tb, Dy, Ho, and Er. The compensation characters appear for the DyFe 7Mn 4Ti and HoFe 7Mn 4Ti compounds, and the compensation temperatures were about 123 K and 90 K, respectively. The Curie temperature, the saturation magnetization, and saturation moment of RFe 7Mn 4Ti compounds were given.

Structure and magnetic properties of RFe7Mn4Ti compounds with R=Y, Tb, Dy,Ho, and Er

The effect of Mn substitution for partial Fe in RFe 11Ti on structure and magnetic properties of compounds was researched. RFe 7Mn 4Ti samples (R=Y,Tb,Dy,Ho,Er) were prepared by means of vacuum arc-melting and subsequent vacuum annealing. The structure and magnetic properties of RFe 7Mn 4Ti compounds were investigated by X-ray powder diffraction and magnetic measurements. The following conclusions were obtained: all the RFe tMn 4Ti compounds crystallize in the ThMn 12-type structure. The lattice constants and the unit-cell volume changed with the increase of atomic number for R=Y, Tb, Dy, Ho, and Er. The compensation characters appear for the DyFe 7Mn 4Ti and HoFe 7Mn 4Ti compounds, and the compensation temperatures were about 123 K and 90 K, respectively. The Curie temperature, the saturation magnetization, and saturation moment of RFe 7Mn 4Ti compounds were given.

Solution combustion synthesis of Fe-Ni-Y_2O_3 nanocomposites for magnetic application

Fe-Ni-Y2O3 nanocomposites with uniform distribution of fine oxide particles in the gamma Fe Ni matrix were successfully fabricated via solution combustion followed by hydrogen reduction. The morphological characteristics and phase transformation of the combusted powder and the Fe-Ni-Y2O3 nanocomposites were characterized by XRD, FESEM and TEM.Porous Fe-Ni-Y2O3 nanocomposites with crystallite size below 100 nm were obtained after reduction. The morphology, phases and magnetic property of Fe-Ni-Y2O3 nanocomposites reduced at different temperatures were investigated. The Fe-Ni-Y2O3 nanocomposite reduced at 900 °C has the maximum saturation magnetization and the minimum coercivity values of 167.41 A/(m2·kg)and 3.11 k A/m, respectively.

Microstructure characteristics and effect of grain orientation on magnetic properties of Fe_(63)Co_(32)Gd_5 alloy ribbons

By using the melt spinning techniques, the Fe63Co32Gd5 alloy ribbons with 15-50 m in thickness and 3-7 mm in width were prepared at the wheel speeds of 15, 20, 25 and 35 m/s. The rapid solidification microstructures were characterized by three layers, the middle layer of which reaches 80% thickness and forms the column grain of(Fe,Co) solid with Gd solution. Grain refinement takes place with the increase of the wheel speed. And after 0.5 h heat treatment at 823 K, the ribbon thickness becomes larger and the middle layer of column grain is very orderly perpendicular to the ribbon plane. The coercivity of quenched and annealed Fe63Co32Gd5 ribbons both have the inflection point at the wheel speed of 20 m/s, and the tendency is declining. The heat treatment processing makes the coercivity become lower by improving the order of(Fe,Co)17Gd2 compound. The saturation magnetization of quenched ribbons increases with the enhancement of wheel speed, whereas that of annealed ones decreases firstly and then increases. The minimum coercivity is 5.30×103 A/m and the maximum saturation magnetization is 163.62 A·m2/kg, which is obtained in the conditions of the wheel speed of 35 m/s and 0.5 h heat treatment at the temperature of 823 K.

The influence of Si substitution on soft magnetic properties and crystallization behavior in Fe_(83)B_(10)C_(6-x)Si_xCu_1 alloy system

In this study, the soft magnetic properties and crystallization behavior of Fes3B10C6-xSixCul （x=0-4） nanocrystalline alloys prepared by annealing the melt-spun amorphous ribbons have been investigated. It is found that in the Fe83B10C6-xSixCU1 alloy system, the coercivity （Hc） decreases slightly with increasing Si addition and exhibits a minimum value with composition of x = 2, while the effective permeability （Ue） shows an opposite variation trend. The saturation magnetic flux density （Bs） shows a slightly decreasing trend owing to the decreasing volume fraction of nanocrystalline phase. The Fe83B10CaSi2Cu1 nanocrystalline alloy exhibits excellent soft magnetic properties with a high Bs of 1.78 T, high ue of 13 600 and low Hc of 4 A/m.

Combined Effect of Magnetic Field and Thermal Dispersion on a Non-Darcy Mixed Convection

This paper is devoted to investigate the influences of thermal dispersion and magnetic field on a hot semi-infinite vertical porous plate embedded in a saturated Darcy-Forchheimer-Brinkman porous medium. The coefficient of thermal diffusivity has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. The effects of transverse magnetic field parameter (Hartmann number Ha), Reynolds number Re (different velocities), Prandtl number Pr (different types of fluids) and dispersion parameter on the wall shear stress and the heat transfer rate are discussed.

Fe-based bulk amorphous alloys with high glass formation ability and high saturation magnetization

It was well known that it was very difficult to prepare high performance Fe-based bulk amorphous alloys with both high Fe content and good glass-forming ability, especially for the Fe content （or total magnetic elements content） higher than 80 at%. In this paper, a series of Fe81-xCoxMO1P7.5C5.5B2Si3 （x = 0, 5, 10, 15, 20） bulk amorphous alloys （BAAs） with high saturation magnetization have been developed by copper mold casting method with fluxed ingot. It has been found that using Co replacing Fe in the Fe-Mo-P-C-B-Si alloy could significantly enhance the glass-forming ability and magnetic property. For the BAA with Co content of 0 at%, 5 at%, 10 at%, 15 at% and 20 at%, its saturation magnetization Js（Js=μoMs） was 1.55, 1.60, 1.62, 1.65 and 1.59 T, respectively. Among these alloys, the Fe66Co15- Mo1P7.5C5.5B2Si3 BAA exhibited a critical size of 2 mm in diameter and a high Js of 1.65 T. It suggested that these alloys with high magnetic element content possessed great potential in application due to their high glass-forming ability and high magnetic property.