Thermal expansion anomaly and spontaneous magnetostriction of Dy_2AlFe_(14)Mn_2 compound

1Introduction The materials with negative thermal expansion have many important applications.These materials are known only in several oxide systems[1,2]and a few Invar alloys[3].When the negative thermal expansion occurs,the contraction is usually small …     

Thermal expansion anomaly and spontaneous magnetostriction of Tb2Fe15Cr2 compound

1. Introduction Materials with zero thermal expansion have many important applications as substrates for high-precision optical mirrors, components of high-precision thermal meters, and catalyst supports [1]. Usually materials with negative thermal expan-sion are used as constituents of composite materials designed to achieve a desired overall thermal expan-sion. However, these materials with negative thermal expansion are known only in several oxide systems [1-2] and a few invar alloys [3]. W…     

Thermal expansion anomaly and magnetic properties of Nd2AlFe11Mn5 compound

1 Introduction Materials with negative thermal expansion have many important applications as constituents of composite materials designed to reduce their overall thermal expansion. In 1991, ANDREEV and his co-workers investigated the properties of rare ea…     

Thermal expansion anomaly and spontaneous magnetostriction of Dy2AlFe14Mn2 compound

The structure and magnetic properties of Dy₂AlFe₁₄Mn₂ compound were investigated by X-ray diffractometry and magnetization measurements. Dy₂AlFe₁₄Mn₂ compound has a hexagonal Th₂Ni₁₇-type structure. Zero thermal expansion and negative thermal expansion were found in Dy₂AlFe₁₄Mn₂ compound in the temperature range from 184 to 264 K, and from 264 to 383 K, respectively, by X-ray dilatometry. The spontaneous magnetostrictive deformations from 104 to 400 K were calculated. The results show that the spontaneous volume magnetostrictive deformation increases firstly with increasing temperature, and then decreases with further increasing temperature.     

Thermal expansion in dysprosium tungstate Dy10W2O21

he complex oxide Dy10W2O21 was synthesized by a solid-state reaction and isolated in cubic symmetry by an X-ray diffractometry (XRD) method. Differential scanning calorimetry (DSC) measurements show that the compound is thermodynamically stable. The intrinsic thermal expansion coefficients were determined by extra-power powder X-ray diffractometry from room temperature to 1 000℃: linear coefficient a = 1.07 × 10-5 ℃-1 and bulk coefficient β= 3.20 × 10-5 ℃-1. Dilatometry was used to measure the extrinsic thermal expansion coefficient (9.2×10-6℃-1).     

Thermal expansion of lattice parameter of （powder） silicon up to 1473 K

The XRPD (X-ray powder diffxactometry) patterns of silicon powder with a unit cell structure of diamond were determined from 298 to 1473 K. Lattice parameters of Si linearly increase with temperature. The thermal shifts of the positions of all reflection peaks are linearly correlated with the temperature. The coefficients of the intrinsic linear thermal expansion and volumetric thermal expansion were determined as 3.87×10-6/K and 1.16×10-5/K respectively. It indicates that Si is still a suitable standard in the XRPD method at high temperatures.     

The isothermal section of the phase diagram of the Dy–Mn–Ni ternary system at 803 K

The isothermal section of the phase diagram of the ternary system Dy–Mn–Ni system at 803 K was investigated by powder X-ray diffraction (XRD), differential thermal analysis (DTA), optical microanalysis and electron probe microanalysis techniques. It consists of 13 single-phase regions, 22 two-phase regions and 10 three-phase regions. At 803 K, the maximum solid solubilities of Mn in Ni, Dy₂Ni₁₇, DyNi₅, Dy₂Ni₇, DyNi₃, DyNi, Dy₃Ni₂ and Dy₃Ni are about 31at.% Mn, 6 at.% Mn, 5.5 at.% Mn, 3 at.% Mn, 5 at% Mn, 5 at.% Mn, 3 at.% Mn and 1.5 at.% Mn, respectively. The maximum solid solubilities of Ni in Mn, DyMn₁₂ and Dy₆Mn₂₃ are about 2.6 at.% Ni, 2 at.% Ni and 4 at.% Ni, respectively. DyMn₂ and DyNi₂ form a continous solid solution in this system. The binary compounds DyNi₄ and Dy₄Ni₁₇ were not observed in this work. The existence of any ternary compound was not observed.     

Magnetocrystalline anisotropy and spin reorientation transition of DyMn6Sn6 compound

The spin-reorientation transition of intermetallic compound DyMn6Sn6 was investigated by applying the molecular field theory. The temperature dependence of easy magnetization direction of compound and the magnetic moment directions of Dy and Mn ions were theoretically calculated and they have good agreement with the experimental data. In the framework of single ion model, the temperature dependence of magnetocrystalline anisotropic constants K1R and K2R of Dy ion were also calculated. The results show that the fourth-order crystal field parameter, B 40, and the corresponding second-order magnetocrystalline anisotropic constant, K2R, of Dy ion must be taken into account in order to explain the spin-reorientation transition satisfactorily. The competition between K2R and K1R plays a key role in the spin-reorientation transition of DyMn6Sn6.     

往复挤压ZK60合金的低温准超塑性(英文)

通过2道次往复挤压制备细晶ZK60合金,在443~523K和初始应变速率为3.310-4~3.310-2s-1的范围内测试合金的低温超塑性。结果表明:往复挤压ZK60合金的平均晶粒尺寸约为5.0m,分布于基体内的破碎二次相颗粒和沉淀颗粒尺寸分别为不大于175nm和50nm。该合金具有低温准超塑性,在523K和3.310-4s-1应变速率下伸长率最大,为270%;在443和473K时,应变速率敏感系数m小于0.2;在523K时m为0.42。当温度不高于473K和523K时,超塑性变形激活能分别不高于63.2kJ/mol和110.6kJ/mol。当低于473K时,主要的超塑性流变机制为晶内滑移;在523K时,主要的超塑性变形机制为晶界滑移,由晶界扩散控制的位错蠕变为主要的兼容机制。     

Variation of the lattice parameter and thermal expansion coefficient of (U,Dy)O2 as a function of DyO1.5 content

Thermal expansions of (U,Dy)O₂ solid solutions were investigated between room temperature and 1673 K by using a thermo-mechanical analyzer. The lattice parameter of (U,Dy)O₂ pellets is lower than that of UO₂ and it decreases as Dy content increases. The linear thermal expansion and average thermal expansion coefficients of (U,Dy)O₂ are higher than that of UO₂. For the temperature range from room temperature to 1673 K, the average thermal expansion coefficient values for UO₂ and (U_0.8Dy_0.2)O₂ are 10.97 × 10⁻⁶ and 11.37 × 10⁻⁶ K⁻¹, respectively.     

Fabrication,magnetostriction properties and applications of Tb-Dy-Fe alloys：a review

As an excelent giant-magnetostrictive material, Tb-Dy-Fe aloys (based on Tb0.27-0.30Dy0.73-0.70Fe1.9-2 Laves compound) can be applied in many engineering ifelds, such as sonar transducer systems, sensors, and micro-actuators. However, the cost of the rare earth elements Tb and Dy is too high to be widely applied for the materials. Nowadays, there are two different ways to substitute for these aloying elements. One is to partialy replace Tb or Dy by cheaper rare earth elements, such as Pr, Nd, Sm and Ho; and the other is to use non-rare earth elements, such as Co, Al, Mn, Si, Ce, B, Be and C, to substitute Fe to form single MgCu2-type Laves phase and a certain amount of Re-rich phase, which can reduce the brittleness and improve the corrosion resistance of the aloy. This paper systemicaly introduces the development, the fabrication methods and the corresponding preferred growth directions of Tb-Dy-Fe aloys. In addition, the effects of aloying elements and heat treatment on magnetostrictive and mechanical properties of Tb-Dy-Fe aloys are also reviewed, respectively. Finaly, some possible applications of Tb-Dy-Fe aloys are presented.     

Vapor pressure and thermochemical properties of ZrCl4 for ZrC coating of coated fuel particles

Vapor pressure of zirconium tetrachloride（ZrCl4）under vacuum and an argon pressure of 1 × 105 Pa was measured. The thermochemical changes of ZrCl4 during evaporation were studied by thermogravimetry-differential thermal analysis（TG-DTA）, X-my diffractometry（XRD）, scanning electron microscopy（SEM） and energy-dispersive X-ray（EDX） analysis. At the same temperature, vapor pressures of ZrCl4 under vacuum and an argon pressure of 1× 10^5 Pa are approximately the same. The vapor pressure exceeds 1 × 10^5 Pa at 340 ℃, which is high enough for ZrC coating of coated fuel particles. ZrCl4 sample is hydrolyzed to some extent to give ZrO2 and HCl, which however, has little influence on vapor pressure of ZrCl4 at high temperature. No ZrCl3 and Cl2 are produced by decomposition of ZrCl4 during evaporation, which is confirmed by thermodynamic calculation.     

Fe55Ni2Cr12Mo10Y2B6C13块体非晶合金的热膨胀行为

本文采用铜模吸铸法制备直径为4mm的块体非晶合金Fe55 Ni2 Cr12 M010 Yo12 B6 C13,对非晶合金在298K-1073K温度区间的热膨胀行为进行了分析.非晶合金的膨胀系数在室温至接近玻璃转化温度区间没有发生明显的变化;当温度超过Tg后,由玻璃态进人过冷液相区,粘度急剧增加,膨胀系数增高;在T>Tg...     

Crystal structure, thermal expansion and magnetic properties of new compound Dy1.2Fe4Si9.8

The new ternary compound Dy_1.2Fe₄Si_9.8 have been prepared and studied by means of X-ray powder diffraction technique and vibrating sample magnetometer. The ternary compound Dy_1.2Fe₄Si_9.8 crystallizes in the hexagonal Er_1.2Fe₄Si_9.8-type structure, space group P6₃/mmc (no. 194) with lattice parameters a = 0.39415(1) nm and c = 1.52771(3) nm. The crystal structural refinement of the compound Dy_1.2Fe₄Si_9.8 has been performed by using Rietveld method. Lattice thermal expansion studies on the compound were carried out in the temperature range from 298 to 1013 K. The variation of the unit cell parameters shows that the unit cell parameters increase with the increase in temperature. The coefficients of average lattice thermal expansion along various axes in the temperature range from 298 to 1013 K are , and . The temperature dependence of the magnetization for the compound was also investigated in the range from 90 to 300 K. The experimentally determined magnetic effective paramagnetic moment is μ_eff = 11.3μ_B per formula unit (10.3μ_B per Dy atom).     

Effect of Dy on the properties of Sm-doped ceria electrolyte for IT-SOFCs

Co-doped ceria-based electrolytes of Ce_0.8Sm_0.2−xDy_xO_2−δ (x = 0, 0.02, 0.06, 0.10, 0.14) were sintered from powders obtained by solid state reaction method. The phase identification, thermal expansion, ionic conductivities and microstructures of samples were studied by X-ray diffraction (XRD), dilatometry, AC impedance spectroscopy (IS) and scanning electron microscopy (SEM). The results showed that the addition of Dy led to higher ionic conductivity and lower activation energy in comparison with Sm singly doped ceria Ce_0.8Sm_0.2O_2−δ (SDC) in the temperature range of 300-800 °C. As the addition amount of Dy increased up to 2 mol% (Ce_0.8Sm_0.18Dy_0.02O_2−δ), the sample attained the highest ionic conductivity, about 50% higher than that of SDC at 500 °C. The effect of Dy on the grain boundary conductivity was more apparent than that of the bulk conductivity. XRD measurements indicated that all the samples were single phase. The thermal expansion was linear for all the samples. The addition of Dy did not change the thermal expansion coefficient (TEC) significantly.     

液固分离法制备Al-65vol%Si电子封装材料组织及性能

采用液固分离法制备了Al-65vol%Si电子封装材料,借助扫描电镜、透射电镜等手段分析了合金中Si相的形态分布、界面及断口形貌,测定了合金的热膨胀系数、热导率及抗弯强度。结果表明:Al-65vol%Si合金组织中硅相颗粒分布均匀,形状规则呈近团球状和短杆状,Al/Si两相界面光滑、平直,无缺陷。合金密度2.4 g/cm3,室温下的热导率(TC)为119.5 W/(m.K),热膨胀系数(CTE)从50℃到400℃在6.5×10-6～11.3×10-6/K范围内稳定增加,抗弯强度为132 MPa,Si相的脆性断裂为主要断裂方式。Al-65vol%Si合金性能满足电子封装要求。     

不同应变速率条件下Al67Ti25Mn8金属间化合物的高温拉伸力学行为

研究了Al67Ti25Mn8金属间化合物在高温不同应变速率条件下的拉伸力学行为.结果表明在3．34×10－5-6.68×10－4s－1范围,随着应变速率的降低,材料的屈服强度显著下降,而拉伸塑性明显升高,塑性最高可达到21％;在低应变速率区高拉伸塑性的获得是由于材料在高温变形过程中发生的动态回复和动态再结晶所致;在高温拉伸时Al67Ti25Mn8金属间化合物是以沿晶方式发生断裂在较高应变速率下材料的低塑性沿晶断裂表明Al67Ti25Mn8的晶界结合强度仍较弱     

冷却速率对Cu49Hf42Al9金属玻璃热膨胀的影响

研究冷却速率对Cu49Hf42Al9金属玻璃热膨胀行为的影响.为了得到较大范围的冷却速率,制备了5种不同尺寸的非晶样品(冷却速率范围为102107 K/S).淬火态样品的平均热膨胀系数(αaver)分布于6.14×10-6 K-1至9.20×10-6 K-1之间.在玻璃转变温度(Tg以下时,淬火态样品的平均热膨胀系数(...     

The Effect of Alloying Elements on the Microstructure of Al-5Fe Alloys

The effects of adding Cr, Mn, and Zr on the microstructure of Al-5Fe alloys has been studied by metallographic analysis, scanning electron microscopy, x-ray diffraction analysis, and differential thermal analysis. It has been found that the effects of the different elements on the microstructure of ferro-aluminum intermetallics in Al-5Fe alloys are not alike. Addition of Cr in Al-5Fe alloys dissolves only into AlFe intermetallics, resulting in the morphology of the AlFe phases being changed with increasing Cr content. Cr is a favorable nucleating agent for encouraging metastable Al _x Fe (x = 4.6 to 5.0) phase formation. Adding Mn in Al-5Fe alloys may stabilize the metastable Al₆Fe phase, helping the primary phase field of Al₇Cr diminish or even disappear and forcing Cr to dissolve into AlFe phases. Adding Zr does not refine the primary AlFe intermetallics. Al₃Zr particles in Al-5Fe alloys will occupy the growing spaces of ferro-aluminum phases and indirectly hinder the growth of Fe-bearing phases.     

Effect of F Doping on Fabrication and Superconductivity of SmO1-xFδFeAs Compound

研究了F掺杂对铁基超导体SmO0.7F0.3FeAs的制备和性能的影响。利用二次固相反应在1120℃保温40h制备出超导临界转变温度(Tc)为56.5K的SmO0.7F0.3FeAs超导体样品,其临界电流密度Jc为2.4×105A/cm2(10K,0T)。研究发现,SmO1-xFxFeAs样品的Tc受F含量的强烈影响,晶格参数的变化也是诱导SmO1-xFxFeAs超导体的Tc变化的原因之一。在此基础上详细研究了F元素过掺杂对铁基超导体SmO1-xFδFeAs(δ>x)制备参数和性能的影响。F元素过量时,在不降低SmO1-xFδFeAs超导性能的情况下,F元素过掺杂可以一定程度地降低样品制备时的热处理温度和极大地缩短热处理时间。1100℃时保温20h制备的SmO0.7F0.35FeAs和SmO0.7F0.4FeAs样品的Tc分别为56和55K;其临界电流密度Jc分别为1.9×105和1.7×105A/cm2(10K,0T)。