Study on preparation technique and properties of magnetostrictive epoxy bonded Tb1-xPrx(Fe0.4Co0.6)1.93 composites

The magnetic and magnetostrictive properties of epoxy bonded Tb1-xPrx(Fe0.4Co0.6)1.93 (0.85≤x≤1.00) composites, prepared with different epoxy proportions using cold compression-molding technique, were investigated. It is found that the optimal conditions were with a compaction pressure of 100 MPa and a mass ratio of resin to powder of 5:100. The Tb0.1Pr0.9(Fe0.4Co0.6)1.93 composite rod had a high magnetostriction of 770 ppm at an applied magnetic field of 960 kA/m, whereas the Pr(Fe0.4Co0.6)1.93 composite reached 500 ppm at 400 kA/m. The good magnetostrictive properties of Pr(Fe0.4Co0.6)1.93 composite at low-field (≤400 kA/m) could be explained by its low anisotropy. These results indicated that the epoxy bonded Tb1-xPrx(Fe0.4Co0.6)1.93 rod samples for high Pr content of x=0.9-1.0 were of practical value.     

Effect of praseodymium and cobalt substitution on magnetic properties and structures in La(Fe_(1–x)Si_x)_(13) compounds

Magnetic properties and structures in La1-zPrz(Fe0.895–xCoxSi0.105)13 (x=0.07, 0.08; z=0, 0.2, 0.4) compounds were investigated. When Pr and Co substituted for La and Fe, the Curie temperature of the compounds was adjusted to around room temperature. The magnetic phase transition was driven from first-order to second-order due to Co substitution. As a second-order phase transition material, the MCE of La0.6Pr0.4(Fe0.825Co0.07Si0.105)13, whose relative cooling power was 175 J/kg under a field change of 2 T, ...     

Effect of Ho-doping on microstructure and magnetostriction of TbDyFe alloys

Tb0.3Dy0.7HoxFe1.95 (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.35, 0.50, 0.65) quaternary alloys were prepared by arc-melting and followed by annealing. The phases present and structure of the alloys were determined using a D8-Advance X-ray diffractometer. The magnetostriction of the alloys was studied by standard strain gauge technique. The dependence of Ho content on the structure, magnetostriction and density of the alloys was investigated in detail. The research results showed that Ho-doping did not change MgCu2-type cubic Laves structure in Tb0.3Dy0.7Fe1.95. When Ho content x≤0.2, rich rare earth phase presented in the alloys increased and magnetostriction of the alloys reduced evidently with increasing x, but for alloys with x>0.2, the content of rich rare earth phase started to reduce and the magnetostriction increased quickly, especially at low magnetic field in the alloy with x=0.65 due to separation of rich rare earth phases on the surface of the alloy.     

Experiment on Nonlinear Properties Coupling Electromagnetism with Mechanics of Giant Rare Earth Magnetostrictive Materials

The electromagnetic and mechanical coupling properties of giant rare earth giant magnetostriction material TbxDy1 -xFe2 -z (0. 27 ≤x ≤ 0.3, 0 ≤ z ≤ 0.1 ) alloys were investigated by means of self-fabricated test apparatus. The effect of coupling mechanical with electromagnetic on magnetostrictive strain coefficient was discussed. The physical model of the coupling system was established. Based on the equivalent circuit of the coupling system, the magnetomechanical coupling coefficient was derived by means of impedance resistance analysis method.     

Technology of melting REM–Fe–Co–B alloys for thermally stable magnets

A technology of making REM–Fe–Co–B (REM = rare-earth metal) alloys for thermally stable magnets is developed. This technology ensures a stable chemical composition (REM content deviation of ±1.0 wt % from the calculated value, Co and B content deviation of ±0.5 wt %) and a low impurity content (Al or Ni ≤ 0.2 wt %, [O] ≤ 0.1 wt %). This technology makes it possible to make Pr–Dy–Fe–Co–B alloys and more complex compositions with additional REM, e.g., gadolinium. Fe–Pr and Fe–Dy master alloys are chosen and melted, and the possibility of using them to make Pr–Dy–Fe–Co–B alloys is studied.     

Research on microstructure and magnetostriction of Fe₈₃Ga₁₇Dy_x alloys

The crystal structure,microstructure and the magnetostriction of Fe83Ga17Dyx(x=0,0.2,0.4,0.6) series alloys were studied.The results showed that the influence of the Dy on the crystal structure of the alloy was very small but the effect on the microstructure was significant when different contents of Dy were added into the Fe83Ga17 alloy,respectively.Meanwhile,the magnetostriction of Fe83Ga17Dy0.2 alloy was greatly enhanced,the magnetostriction λ value reached 300×10-6 at 400(kA/m) magnetic field.     

Co-Al基三元系中B2相的溶解度间隙与稳定性

Information on phase equilibria in the Co-Al based systems which are related to some magnetic and heat resistance materials is important for their microstructural control. Recently, it was proposed with a theoretical calculation on electronic band structure that some Heusler-type alloys Co2 XAl (X: Cr and Mn) should be a new type of spinelectronic materials so-called half-metallic ferromagnet. In the case of the Co2CrAl, however, magnetic properties expected from the theoretical work can not been experimentally obtained and the reason has been still unknown. On the other hand, a tunne- ling magnetoresistance (TMR) effect due to the half-metallic properties was reported in Co2 (Cr0.6 Fe0.4 ) Al alloy, but not the Co2CrAl alloy. In the present paper, it is reported that this discrepancy with the theoretical work in the Co2CrAl alloy is bought about by phase separation between A2 and B2 phases, and that the substitution of Fe for Cr can suppress the precipitation of A2 phase in the B2 phase. Such a phase separation is originally due to the miscibility gap between CoAl and Cr formed in the Co-Al-Cr ternary system as well as that reported by Hao et al. in the Ni-Co-Al-Fe system.     

Research on microstructure and magnetostriction of Fe83Ga17Dyx alloys

The crystal structure, microstructure and the magnetostriction of Fe₈₃Ga₁₇Dy_x (x=0, 0.2, 0.4, 0.6) series alloys were studied. The results showed that the influence of the Dy on the crystal structure of the alloy was very small but the effect on the microstructure was significant when different contents of Dy were added into the Fe₈₃Ga₁₇ alloy, respectively. Meanwhile, the magnetostriction of Fe₈₃Ga₁₇Dy_{0. 2} alloy was greatly enhanced, the magnetostriction λ value reached 300×10^?6 at 400 (kA/m) magnetic field.     

Structure and electrochemical hydrogen storage characteristics of the as-cast and annealed La0.8-xSmxMg0.2Ni3.15Co0.2Al0.1Si0.05 （x=0-0.4） alloys

In order to ameliorate the electrochemical cycle stability of the RE-Mg-Ni based A2B7-type electrode alloys, the Mg content in the alloy was reduced and La in the alloy was partially substituted by Sm. The La0.8-xSmxMg0.2Ni3.15Co0.2Al0.1Si0.05 (x=0, 0.1, 0.2, 0.3, 0.4) elec-trode alloys were fabricated by casting and annealing. The microstructures of the as-cast and annealed alloys were characterized by XRD and SEM. The electrochemical hydrogen storage characteristics of the as-cast and annealed alloys were measured. The results revealed that all of the experimental alloys mainly consisted of two phases: (La,Mg)2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure. As Sm content grew from 0 to 0.4, the discharge capacity and the high rate discharge ability (HRD) first in-creased and then decreased for the as-cast and annealed alloys, whereas the capacity retaining rate (S100) after 100 cycles increased continuously.     

Influence of rapid quenching on cyclic stability of La-Mg-Ni system （AB3-type） electrode alloys

Aiming at the improvement of the cyclic stability of La-Mg-Ni system （PuNi3-type） hydrogen storage alloy, Ni in the alloy was partly substituted by Fe. The electrode alloys of La0.7Mg0.3Co0.45Ni255-xFex （x=0, 0.1, 0.2, 0.3, 0.4） were prepared by casting and rapid quenching. The influence of the quenching on cyclic stability as well as structure of the alloys was investigated in detail. The results of electrochemical measurement indicated that rapid quenching significantly improved cyclic stability. When the quenching rate rose from 0 （As-cast was defined as a quenching rate of 0 m/s） to 30 m/s, the cyclic life of Fe-free alloy （x=-0） increased from 81 to 105 cycles, and for alloy containing Fe（x=0.4）, it grew from 106 to 166 cycles at a current density of 600 mA/g. The results obtained by XRD, TEM and SEM revealed that the as-cast and quenched alloys had multiphase structures, including two major phases （La, Mg）Ni3 and LaNi5 as well as an imptLrity phase LaNi2. Rapid quenching helped the formation of an amorphous-like structure in Fe containing alloys.     

Magnetostriction and hysteresis of <110> oriented TbDyHoFe_1.95 alloy

(Tb0.36Dy0.64)1-xHoxFe1.95 magnetostrictive alloys with <110> orientation were prepared by zone melting directionally solidified method.The magnetostrictive performance and hysteresis of <110> aligned polycrystalline(Tb0.36Dy0 64)1-xHoxFe1.95 were investigated under applied magnetic field H(0相似文献   

LaGd_(0.1)Fe_(11.4-x)Co_xSi_(1.6)(x=0.1,0.3,0.5,0.7,0.9)合金的磁热效应

研究了LaGd0.1Fe11.4-xCoxSi1.6(x=0.1,0.3,0.5,0.7,0.9)系列合金的结构以及磁热效应。室温XRD分析表明该系列合金除微量的α-Fe相外,均具有立方NaZn13型立方单相晶体结构,空间群为Fm-3c。晶格常数没有明显变化,分别为1.1458,1.1454,1.1458,1.1459,1.469nm。磁性测量表明该系列合金的Tc随着Co含量的增加而增加,分别为212,231,253,281,302K。在外磁场变化ΔB=1.5T时,最大的磁熵变随着Co含量的增加而减少,由x=0.1的13.8J降为x=0.9J.kg-.1K-1的1.5J.kg-.1K-1。并且随着Co含量的增加存在由一级相变转为二级相变的趋势。     

Phase structure and magnetocaloric effect of (Tb1-xDyx)Co2 alloys

Phase structure and magnetocaloric effect of (Tb1-xDyx)Co2 alloys with x=0, 0.2, 0.4, 0.6, 0.8, and 1.0 were investigated using X-ray diffraction analysis, differential thermal analysis, and magnetization measurement. The samples were single phase with cubic MgCu2- type structure; with the increase of Dy content, Tc decreased from 240 K (TbCo2) to 130 K (DyCo2), and the maximum magnetic entropy change |ΔSM,max| increased from 3.133 to 8.176 J/kg-K under low magnetic field of 0-2 T. The Arrott plot and the change of |ΔSM,max| showed that magnetic phase transition from second order to first order occurred with the increase of Dy content between x=0.6 and 0.8.     

多元化降钴对贮氢合金性能的影响

为了降低贮氢合金中的钴含量，从而降低镍氢电池的价格，在贮氢合金M1Ni3．55Co0．75Al0．3Mn0．4的基础上，依次添加Cu、Cr、Zn、Fe元素，得到稀土基多元贮氢合金，并对其放电容量和循环稳定性进行了测试和分析。结果表明，适量的Cu、Cr、Zn、Fe替代Co，仍能使贮氢合金具有较高的放电容量和较好的循环稳定性。     

Enhanced magnetostrictive properties of lightly Pr-doped Fe_(83)Ga_(17) alloys

Fe_(83)Ga_(17)Pr_x alloys,where x=0,0.2,0.4,0.6 and 1.0,were prepared by a non-consumable vacuum arc melting technique under an inert argon gas atmosphere.The crystal structure and surface morphologies of the alloys were studied by X-ray diffraction(XRD) and scanning electron microscopy(SEM),respectively.Local compositional variations were measured by energy dispersive X-ray spectroscopy(EDXS).The magnetostriction coefficients of the alloys were measured by means of a differential resistive strain sensor.The magnetism of the sample was measured by a vibrating sample magnetometer(VSM).The results show that the parent Fe_(83)Ga_(17) alloy consists of a single A2 phase of bcc symmetry,whereas the Pr doped Fe_(83)Ga_(17) alloys are composed of the A2 phase of bcc structure and a small volume fraction of PrGa2 as a secondary phase.Most importantly,with increasing x,the magnetostriction coefficient of the Fe_(83)Ga_(17)Pr_x alloys first increases reaching a maximum saturation magnetostriction coefficient of192 ppm for x=0.6 at a magnetic field strength of 486 kA/m,then decreased.This maximum represents a 400% increase over the parent alloy with a mere 0.6 at% Pr doping.     

Effect of niobium on glass-formation ability and soft magnetic properties of Gd-doping glassy alloys

The effect of niobium on glass-formation ability and soft magnetic properties were studied in Fe-Gd-B glassy alloys. The glassy alloys exhibited high glass-formation ability when the element of Nb was added. Bulk glassy rod （Fe0.87Co0.13）68.5Gd3.5Nb3B25 with a diameter up to 3 mm was produced by copper mold casting. The size of the atom might play an important role in increasing glass-formation ability. The coercive force of glassy （Fe0.87Co0.13）71.5.xGd3.sNbxB25 （x=1.2, 1.5, 2, 2.5, 3, 4） alloys decreased after the addition of niobium element and was in the range of 1.5-2.9 A/m. The permeability spectrum of （Fe0.87Co0.13）70.3Gd3.5Nb1.5B25 glassy ribbon showed that the relaxation frequency （f0） was 6.1 MHz.     

Research Advance on Magnetocaloric Effect of La-Fe-M(Al, Si) Compounds

Inviewofenergysavingandenvironmentalpro tection ,magneticrefrigerationnearroomtemperaturehasastrongimpactonconventionalgascompressiontechnology .However ,coolingefficiencyofthesystemformagneticrefrigerationismainlydecidedbythemagnitudeofmagnetocaloriceffectformagneticrefrig eratingmaterialsinthesystemunderacertainmagnet icfieldchange .Therefore ,developmentofnewrefrig eratingmaterialswithgreatmagnetocaloriceffectnearroomtemperatureisespeciallyimportant .Therearetwoparameterswhichareusedtochara…     

Luminescence properties of the co-luminescence groups of Sm-La-pyridyl carboxylic acids

A novel ligand, N,N’-(2,6-pyridinedicarbonyl)bis[N-(carboxymethyl)] (L1) was designed and synthesized starting from pyri-dine-2,6-dicarboxylic acid (1). The ligand (L1) and intermediate product (3) were characterized by 1H nuclear magnetic resonance (NMR), Fourier transform infrared spectrometer (FT-IR) spectra and elemental analysis. Besides, four novel co-luminescence systems of Sm-La-pyridyl carboxylic acids: K4Sm(1-x)Lax(L1)Cl3·y1H2O, K12Sm2(1-x)La2x(L2)3 Cl6·y2H2O, K6Sm2(1-x)La2x(L3)Cl6·y3H2O and K4Sm(1-x)Lax(L4)Cl3·y4H2O (x was the mole fraction of La(III) in the mixed ions, the value was 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, respectively; y1, y2, y3, y4 were plus integer) were studied, and the mechanism of fluorescence enhancement effect was discussed detailedly.     

Magnetostriction, composition and microstructure of Tb0.29（Dy1–xPrx）0.71Fe1.97 alloys with heat treatment

Tb_0.29(Dy_1-xPr_x)_0.71Fe_1.97 (x=0, 0.1, 0.2 and 0.3) alloys prepared by the directional solidification method were treated at 1073, 1123, 1173, 1223 and 1273 K for 4 h for homogenization, respectively. The magnetostriction, micro-morphology and composition distribution were studied by the standard resistance strain gauge technique, optical microscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The results indicated that heat treatment could make the microstructure of alloys homogeneous effectively and improve the magnetostriction significantly. The optimum temperature was 1223 K. Compared to the as-cast ones, the increase amplitudes of magnetostriction of the corresponding samples were 39.5%, 64.9%, 95.3% and 50.8% when x=0, 0.1, 0.2 and 0.3, respectively at the compressive stress of 2 MPa and a magnetic field of 80 kA/m. The compressive stress could also improve the magnetostriction. However, further Pr element addition and over high heat treatment temperature would lead to the excessive decomposition of PrFe₂ and destroy the homogeneity, resulting in the decline of magnetostriction of alloys.     

The effect of mischmetal addition on the structure and mechanical properties of a cast Al-7Si-0.3Mg alloy containing excess iron (up to 0.6 Pct)

The effect of Fe content (0.2 to 0.6 pct) on the microstructure and mechanical properties of a cast Al-7Si-0.3Mg (LM 25/356) alloy has been investigated. Further, 1 pct mischmetal (MM) additions (a mixture of rare-earth (RE) elements) were made to these alloys, and their mechanical properties at room and at elevated temperatures (up to 200 °C) were evaluated. A structure-property correlation on this alloy was attempted using optical microstructure analysis, fractographs, X-ray diffraction, energy-dispersive analysis of X-rays (EDX), and quantitative metallography by image analysis. An increase in Fe content increased the volume percentage of Fe-bearing intermetallic compounds (β and π phases), contributing to the loweryield strength (YS), ultimate tensile strength (UTS), percentage elongation, and higher hardness. An addition of 1 pct MM to the alloys containing 0.2 and 0.6 pct Fe was found to refine the microstructure; modify the eutectic silicon and La, Ce, and Nd present in the MM; form different intermetallic compounds with Al, Si, Fe, and Mg; and improve the mechanical properties of the alloys both at room and elevated temperatures.