Synthesis of Iron-Based Laves Phase Containing Praseodymium Magnetostrictive Materials

The synthesis and magnetostriction of PrxTb1-x.Fe2, PrxTb1-x Fe2BO2 and PrxTb1-x（Fe0.6Co0.4）2 alloys were investigated in this study. The addition of boron or cobalt atom in PrxTb1-xFe2 could effectively prevent the formation of non-cubic phases, and Pr concentration limit was successfully increased from 0.2 to 0.4. X-ray step scanning for the PrxTb1-xFe2BO2 and PrxTb1-x（Fe0.6Co0.4）2 alloys showed that PrFe2 possessed a large spontaneous magnetostriction λ1111.

Structure, Magnetic Properties and Magnetostriction of Pr_xTb_(1-x)(Fe_(0.6)Co_(0.4))_(1.9) Alloys

The structure, magnetic properties and magnetostriction of PrxTb1-x(Fe0.6Co0.4)1.9 alloys were investigated. It was found that PrxTb1-x(Fe0.6Co0.4)1.9 alloys with x<0.4 were composed of single cubic Laves phase, while a mass of PuNi3-type phase appeared when the Pr concentration was higher than 0.4. The magnetization measurement showed that there were two different magnetic phases in Pr0.2Tb0.8(Fe0.6Co0.4)1.9 alloys. The saturation magnetostriction of Pr0.2Tb0.8(Fe0.6Co0.4)1.9 alloys at 900 kA·m-1 is 1765×10-6, which was higher than that of Tb0.27Dy0.73Fe2(1600×10-6). The spontaneous magnetostriction λ111 showed a maximum value at x=0.3.

Magnetic properties and magnetostriction of PrxNd_(1-x)Fe_(1.9)(0≤x≤1.0) alloys at low temperature

The crystal structure,magnetic and magnetostrictive properties of high-pressure synthesized Prx Nd1-xFe1.9（0≤x≤1.0） alloys were studied.The alloys exhibit single cubic Laves phase with MgCu 2-type structure.The initial magnetization curve reveals that Pr0.2Nd0.8Fe1.9 has a minimum magnetocrystalline anisotropy at 5 K.The magnetostriction curve at 5 K shows that Pr0.2Nd0.8Fe1.9 has a very good low-field magnetostrictive property,and the magnetostriction of the PrxNd1-xFe1.9 alloy in high magnetic field is attributable mainly to Pr.The temperature dependence of the magnetostriction（λ ｜｜） at the field of 5 kOe shows that the substitution of Nd reduces the K 1 remarkably,and the values of λ｜｜ of Pr0.2Nd0.8Fe1.9 and Pr0.8Nd0.2Fe1.9 alloys are nearly five times larger than that of the PrFe 1.9 alloy below 50 K;the λ｜｜ of Pr0.8Nd0.2Fe1.9 reaches up to 1082 ppm at 100 K,which makes it a potential candidate for application in this temperature range.

THE SYNTHESIS AND MAGNETOSTRICTION OF P_ (rx) Ce_(1-x) Fe_2 COMPOUNDS

The synthesis and magnetic properties of Pr xCe 1 x Fe 2 have been investigated. The forma tion of Pr xCe 1 x Fe 2 is found to depend strongly on annealing temperature. Pure single phase compound can be synthesized at ambient pressure when x≤0 5. The main phase of the Laves structure can still be observed up to x=0 8. Magnetostriction increases with in creasing x and a largest saturation magnetostriction 200 ppm is observed for x=0.5.

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.

Structure,magnetization, and magnetostriction of Sm-R-Fe (R=Pr,Nd) thin films

The structure, magnetization, and magnetostriction of Sm0.9Pr0.1Fex and Sm1-xNdxFel.9 thin films have been investigated using X-ray diffraction, vibrating sample magnetometer, and optical cantilever method. It is found that the structure of Sm0.9Pr0.1Fex thin films consists of an Sm-Pr-Fe amorphous phase when x≤2.69 and that of Sm1-xNdxFel.9 thin films consists of an Sm-Nd-Fe amorphous phase. The in-plane magnetization of Sm0.91Pr0.1Fex thin films increases with increase in the Fe content, and low values of the in-plane coercivity occur in the range of 1.62≤ x≤ 2.28. The magnetostriction value of Sm0.91Pr0.1Fex thin films increases with increasing the Fe content when x ≤ 1.94 and decreases when x 〉 1.94. The in-plane magnetostriction of Sm1-xNdxFe1.9 thin films under low magnetic fields has been improved by the substitution of Nd for Sm when x = 0.2.

Effect of cerium on microstructure,eutectic carbides and Laves phase in electroslag remelted 15Cr-22Ni-1Nb austenitic heat-resistant steel

The dendrites,eutectic carbides,Laves phase and microsegregation of alloying element in electroslag remelted 15Cr-22Ni-1Nb austenitic heat-resistant steel with varying cerium contents were studied.The liquidus and solidus temperatures of the steel were determined to reveal the effect of cerium on solidification temperature interval and local solidification time of the steel.The secondary dendrite arm spacing decreases from 57.10 to 40.18μm with increasing the cerium content from 0 to 0.0630 wt.%.The eutectic NbC and Laves phase in as-cast ingots exhibit blocky and honeycomb morphology,respectively.The area fractions and sizes of eutectic NbC and Laves phase in as-cast ingots decrease with the increase in cerium content.The atomic percentage of Laves phase-forming element(Ni,Nb,Cr,Mo and Si)decreases with the increase in cerium content of the steel.The microsegregation of Mo,Ni,Si,Cr and Nb decreases with increasing the cerium content,which is favorable to reducing both the amount and sizes of eutectic NbC and Laves phase in as-cast ingots.The solidification temperature interval and local solidification time of the steel decrease as the cerium content is increased from 0 to 0.0630 wt.%,which inhibits the growth of dendrites,eutectic NbC and Laves phase.

Large magnetostriction of Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites in a wide temperature range

We report the magnetostrictive performance of the Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites.Measurement of M?ssbauer spectra and the XRD results indicate that the easy magnetic direction of the Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)compound is along<111>direction with spontaneous magnetostrictionλ111 of1900 ppm.The<111>-oriented Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites with particle volume fractions of20 vol%-55 vol%were prepared.Magnetization measurements demonstrate that the composite is highly anisotropic.The raw material cost of Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)is about 85%of that of the Terfenol-D(Tb_(0.3)Dy_(0.7)Fe_(2))composition.Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites possess comparable magnetostriction with those composites made of Tb_(0.3)Dy_(0.7)Fe_(2)particles.At room temperature,the magnetostrictionλ_Ⅱof the Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composite reaches 420 ppm at a low field of 80 kA/m and about1000 ppm at 239 kA/m.In addition,the composite exhibits a large saturation magnetostrictionλ_Ⅱover1200 ppm from 300 to 100 K,suggesting its potential applications as a low-cost magnetostrictive material in a wide temperature range.Therefore,the current study offers an opportunity to widen the operating temperature range of the magnetostrictive composite.

Laves相稀土-过渡族金属间化合物Tb_(1-x)Dy_(x)Co_(1.95)的磁学性质及相变研究

主要研究了Tb_(1-x)Dy_(x)Co_(1.95)稀土-过渡族金属间化合物体系的磁学性质及相变性质。利用X射线衍射表征物相,利用磁学测量系统对材料的磁学性能及磁性相变的种类和温度进行测定,利用热机械分析仪(TMA)测试得到了材料的热膨胀曲线。结果表明:随着体系中Dy元素含量的增加,材料的晶格常数和居里温度均呈现降低趋势。Tb_(1-x)Dy_(x)Co_(1.95)体系在测试温度范围内发生了一级的铁磁相变,这弥补了相关领域的研究空白。除此之外,Tb1-xDyxCo1.95体系在发生磁性相变时的能量变化补偿了正常热胀冷缩,导致Tb_(1-x)Dy_(x)Co_(1.95)体系在一定温度范围内存在较小的热膨胀效应。

Structure and magnetostriction of high Pr/Ce-content(Tb_(0.2)Pr_(0.8))_(1-x)Ce_(x)Fe_(1.93) Laves compounds

The light rare earth Pr/Ce-contained(Tb_(0.2)Pr_(0.8))_(1–x)Ce_(x)Fe_(1.93)(0≤x≤1.0)intermetallics were arc melted and magnetoelastic properties were investigated.The compounds of x≥0.40 are found to stabilize at ambient pressure in a single Laves phase with MgCu2-type C15 structure,which is attributed to the strong Ce 4f bonding.The mixed-valence behavior,with a support of the deviation from the linear Vegard’s law for both lattice parameter a and saturation magnetization M_(S),is observed at room temperature.The easy magnetization direction(EMD)was determined by the analysis of XRD on both magnetically aligned samples and the(440)splitting,that is,EMD lies toward<111>axis for x≤0.50 rotating to<110>for x=0.60,accompanied with the structural distortion from rhombohedral to orthorhombic.The substitution of Ce for Tb/Pr is conductive to the reduction of magnetocrystalline anisotropy,giving rise to an improvement of the low-field magnetostriction.The excellent magnetoelastic properties can be tailored by the Ce introduction,e.g.,the spontaneous magnetostriction coefficient λ_(111) as large as 1150×10^(−6) for x=0.40,and the low-field induced magnetostriction achieving a high value of λ_(a)=180×10^(−6) at 80 kA/m for x=0.60.The excellent magnetoelastic properties and the combination in high Pr-content with low cost,suggest promising prospects in applications.

First-principles investigation of mechanical and electronic properties of LaAg5 Laves phase under pressure

The effects of applied pressure on the structural, mechanical, and electronic properties of LaAgs compound were investi- gated employing the first-principles method based on the density fimctional theory. The mechanical results demonstrated that bulk modulus, shear modulus and Young＇s modulus presented the linearly increasing dependences on the external pressure; the B/G and Poisson＇s ratio indicated that LaAg5 compound was a ductile material with central forces in interatomic under pressure from 0 to 40 GPa; the universal anisotropic index was performed to investigate the elastic anisotropic of LaAgs. Additionally, the pressure de- pendence of the density of states and Mulliken charge were also discussed. The bonding characterization in LaAg5 was composed of metallic, covalent and ionic. The metallic component was derived from free-electron transferring from Ag-s and Ag-d to Ag-p, and from La-s to La-d. The ionic component was due to the charge movement from La to Ag. The covalent was owing to Ag-p-La-d bonding hybridization and Ag-s-Ag-p in the Ag atomic chains. The covalent and ionic bonds were stronger under pressure but there was no significant change in metallic nature.

稀土元素钇对Laves相NbCr_2合金在1100℃氧化行为的影响

采用机械合金化及热压烧结工艺制备了掺杂0.07%～1.35%(质量分数)稀土元素钇的Laves相NbCr_2合金,研究了钇含量对NbCr_2合金在1 100℃氧化行为的影响,并探讨了其作用机制。结果表明:只有添加适量的钇(0.07%～0.14%)才能降低NbCr_2合金的氧化速率,提高NbCr_2合金的抗氧化性能;NbCr_2合金高温抗氧化性能的提高,主要是由于稀土元素钇增强了氧化膜与基体的结合性能。

白云鄂博氧化矿氢基矿相转化产品工艺矿物学特性研究及选别工艺论证

为了更好地开发利用包钢宝山铁等资源,采用化学成分分析、SEM、MLA、X射线衍射分析等检测方法对白云鄂博预富集精矿氢基矿相转化产品(HMPT)进行工艺矿物学研究,并对该矿石进行了分离回收探索试验。结果表明,HMPT中产品TFe含量为41.10%,FeO含量15.60%,REO品位为5.69%,主要杂质成分为SiO_(2),含量为8.41%,赤褐铁矿在氢基矿相转化过程中基本还原为磁铁矿。HMPT产品中-0.074 mm粒级含量为52.23%,铁分布率为48.22%;-0.038 mmm粒级含量为39.10%,TFe品位为36.26%,铁分布率为35.06%。磁铁矿的总体解离度较差,为63.61%。其中主要与稀土氧化物或石英二相连生,尤其与稀土氧化物嵌布关系更为紧密,部分磁铁矿与白云石、独居石等矿物多相连生。独居石和稀土氧化物在-0.043 mm解离度较高,但总解离度均不足60%;萤石解离度较差,总解离度约为50%;铌矿物解离度最差,不足25%。不同矿物之间的单体解离度较低,嵌布关系较为复杂。因此推荐采用阶段磨矿—阶段磁选—反浮选试验流程,最终磁选精矿经过浮选脱氟后,可获得TFe品位65.26%、铁总回收率80.68%、F含量0.28%的技术指标,实现了铁的高效回收。

稀土-铁Laves相化合物的结构与磁致伸缩

采用光学显微、Ｘ射线衍射、热磁分析和电阻应变仪技术研究了Ｒ（Ｆｅ１－ｘＧａｘ）１．８５合金的结构与磁致伸缩．这些合金的基体具有立方Ｌａｖｅｓ相结构．加入少量的Ｇａ使赝二元Ｌａｖｅｓ相化合物的均匀范围移向化学计量成分．增加Ｇａ的含量，晶格常数线性增大，而居里温度和室温磁致伸缩λｓ迅速降低．低磁场下（Ｈ＜４ｋＯｅ），ｘ＝０．

Magnetic Properties and Phase Transformation of Tb_(1-x)Pr_xFe_(1.96)(x=0 to 0.7) Compounds

The magnetic properties and the phase Transformation of Tb1-xPrx Fe1.96（x = 0 to 0.7） compounds were studied by means of vibrating sample magnetometer（VSM）, X-ray diffraction（XRD） and SEM back-scattered electron （BSE）. The result indicates that the saturation magnetization σs of compounds along an easy axis decreases with the addition of Pr contents, which reduces from 77.24 Am^2·kg^-1（x =0） to 11.84 Am^2·kg^-1（x =0.5） and then returns to 37.14 Am2·kg^-1 （ x = 0.7）. The non-cubic phases appear when x exceeds 0.2, and the matrix of Tb1-xPrxFe1.96 compounds changes from （Tb, Pr）Fe2 phase with x = 0 to （Tb, Pr）Fe3 phase with x = 0.4, and at last to （Tb, Pr）2Fe17 phase in Tb0.3Pr0.7Fe1.96. Moreover, the structure, of the compounds may become more complex with the increase of Pr content.

Phase diagram of R-Fe-Co pseudoternary system with R≤33.3 %(mole fraction, R=Sm_(0.5)Dy_(0.5))

Phase equilibria of the R-Fe-Co pseudoternary system with R≤33.3%(mole fraction, R=Sm 0.5Dy 0.5) were determined in an isothermal section at 1 073 K and a vertical section of RFe 2-RCo 2 by using OM, X-ray diffractometer, EPMA DTA techniques. There are seven intermetallic phases: (Sm, Dy)(Fe, Co) 2, (Sm, Dy)(Fe, Co) 3, (Sm, Dy) 6(Fe, Co) 23, (Sm, Dy) 2(Fe, Co) 7, (Sm, Dy)(Fe, Co) 5, Th 2Ni 17-type and Th 2Zn 17-type (Sm, Dy) 2(Fe, Co) 17. The (Sm, Dy) 6(Fe, Co) 23 phase dissolves 36% Co(mole fraction) at 1 073 K. However, the (Sm, Dy) 2(Fe, Co) 7 phase in R 2(Fe 1-xCo x) 7 alloys dissolves about 19% Fe(mole fraction) at 1 073 K.

PHASE RELATIONSHIPS IN R-Fe PSEUDOBINARY SYSTEM (R=Dy_(0.65)Tb_(0.25)Pr_(0.1))

The phase relationships of R-Fe pseudobinary system(R=Dy0.65Tb0.25Pr0.1) have been determined using optical microscopy,X-ray diffraction,EPMA and DTA techniques.This system contains one eutectic reaction and four peritectic reactions.The four intermetallic compounds are(Dy,Tb,Pr)Fe2,(Dy,Tb,Pr)Fe3,(Dy,Tb,Pr)6Fe23 and(Dy,Tb,Pr) 2Fe17 The homogeneity regions of these compounds shift towards rare earth-rich side of the stoichiometric composition except(Dy, Tb,Pr) 2Fe17.

稳恒磁场下白云鄂博矿形貌变化及热分解分析

研究了稳恒磁场条件下焙烧对矿物分解的影响,在焙烧温度950℃、磁感应强度1.02 T时,对白云鄂博贫铁矿进行非碳热还原条件下的直接焙烧实验,采用TG-DSC、XRD、SEM-EDS等手段,分析矿物失重率、矿相转变、显微形貌变化,揭示了磁场作用下稀土矿物、脉石矿物、铁矿物的矿相演变规律。结果表明,相较于无磁条件,施加稳恒磁场后,氟碳铈矿分解所需时间缩短近20 min,分解率极低的独居石在焙烧60 min后几乎完全分解;磁场可以促进脉石矿物的分解转变,使无磁条件下无法发生分解的钠辉石发生大量分解,同时加快碱金属离子迁移速度、促进与铁橄榄石中Fe2+的置换。

超磁致伸缩加速度传感器(英文)

稀土铁超磁致伸缩材料具有磁致伸缩逆效应，以此为基础的加速度传感器具有过载能力强、测量范围广、能在恶劣环境下工作、寿命长等一系列优异性能，在重工业、化学等工业领域的自动化控制系统中有着广泛的应用前景。为了有效地设计和优化超磁致伸缩加速度传感器，该文根据能量变分原理，建立了超磁致伸缩材料Tb-Dv-Fe制作的加速度传感器的磁-机械强耦合模型，应用该模型采用自编有限元软件，计算了传感器空气隙中的磁感应强度和施加加速度的关系，并测试了施加加速度从20—150m／s^2范围内传感器空气隙中的磁感应强度，发现计算结果与实验结果符合较好，相对误差小于9％，满足工程需要。表明建立的超磁致伸缩加速度传感器的磁-机械强耦合有限元模型是有效的，能够反映超磁致伸缩加速度传感器的输入输出关系。

镧镨铈混合稀土金属在Al-Si合金中的作用

本文研究了一种新型的镧镨铈混合稀土对铝硅合金中共晶硅的变质作用和铁相的作用。研究证明 ,镧镨铈混合稀土对 Al- Si合金中共晶硅有着比富铈混合稀土更强的变质能力 ,其残余量在 0 .17%和 0 .2 4%之间即可使硅含量接近 12 %的铝硅二元合金得到良好变质 ;镧镨铈混合稀土有促进 Al- Si合金中针状铁相析出的作用 ,为保证铝硅合金中不出现针状铁相 ,镧镨铈混合稀土的加入量以不超过 0 .45 %为好。