Ni_(43)Mn_(46-x)T_xSn_(11)(T=Fe,Co,Ni)合金的马氏体相变和磁熵变

通过示差扫描量热仪和振动样品磁强计对Ni43Mn46-xTxSn11(T=Fe,Co,Ni)铁磁形状记忆合金的相变、磁性以及磁熵变进行了研究。结果表明,由于价电子浓度的增加,Fe,Co,Ni替代Mn使马氏体转变温度大幅提高。Fe,Ni掺杂对马氏体居里温度(TCM)影响不大,Co则使TCM略有下降;奥氏体居里温度(TCA)对成分比较敏感,Fe,Ni的加入均使TCA略有提高,而Co则会大大提高TCA。由于马氏体相变伴随着磁化强度的突变,Ni43Mn46-xTxSn11合金在马氏体相变附近具有较大的低场磁熵变,对于Ni43Mn41Co5Sn11在室温1T磁场下磁熵变达到了19J.kg-.1K-1。通过调节成分,磁熵变峰值温度可以在199和294K之间调节,同时保持了较大低场磁熵变。     

哈斯勒合金Ni-Mn-Sn的磁热效应

采用真空电弧熔炼法和高温淬火法制备了四元哈斯勒合金Ni50-xCuxMn36Sn14(x=0,2,4,6)的化合物。用X射线衍射仪和振动样品磁强计研究了合金的物相与磁热效应。结果表明,部分Cu元素对Ni的替代,并没有改变三元哈斯勒合金Ni-Mn-Sn原有的晶体结构,只是晶格常数开始有减小的趋势,晶胞的体积没有发生太大的变化。M-T曲线的结果表明,该系列哈斯勒合金样品在奥氏体相的铁磁交换作用增强,导致居里温度升高,而结构相变温度降低。此外,通过麦克斯韦方程计算了该系列合金的磁熵变(-ΔSm),在磁场变化为1.5 T的情况下,获得了Ni46Cu4Mn36Sn14合金在330 K附近的最大磁熵变(-ΔSmmax)约为2.0 J·(kg·K)-1。     

MnP_(1-x)M_x系列合金的磁热效应

研究了1∶1型MnP基系列合金MnP1-xMx(M=Si,Sb,Ge,Zn,Sn)(x=0,0.1)的结构及其磁热效应。室温X射线衍射表明该系列合金的主相结构均为正交MnP结构,空间群为Pnma。在用Ge,Sb,Zn,Sn作为替代元素的合金中存在少量第二相Mn5.64P3。磁性测量表明该系列合金MnP1-xMx(M=Si,Sb,Ge,Zn,Sn)(x=0,0.1)的存在由铁磁-顺磁的二级相变。其居里温度Tc分别为286,295,294,295,295K。通过磁化曲线计算了MnP1-xMx(M=Si,Sb,Ge,Zn,Sn)(x=0,0.1)合金的最大等温磁熵变-ΔSm,均在0.7～1.3J.kg-.1K-1之间。     

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。     

P元素的替代对LaFe_(11.4)Si_(1.6)的磁热效应影响

通过电弧炉熔炼法制备了LaFe11.4Si1.6-x P x(x=0.05,0.1,0.2,0.3)系列合金,XRD分析表明少量P元素替代,LaFe11.4Si1.6-x P x(x=0.05,0.1,0.2和0.3)合金仍然保持NaZn13型结构,但晶格常数减小。在居里温度T c附近磁化曲线表明,该系列合金经历由磁场引起巡游电子由顺磁态到铁磁态变磁转变的一级相变。随着P含量的增加,LaFe11.4Si1.6-x P x(x=0.05,0.1和0.2)的居里温度T c减小,等温磁熵变也减小。在外加磁场变化为0~1.5 T时,等温磁熵变最大值分别为19.3 J/(kg·K),15.3 J/(kg·K)和10.3 J/(kg·K)。     

热处理工艺对( Mn,Fe)2(P,Si)系列化合物磁性的影响

用机械合金化方法成功制备了Mn1.35Fe0.65 P1-x Six(x=0.56和0.57)化合物,分别采用了两种不同的工艺对化合物进行热处理.用X射线衍射仪、振动样品磁强计和绝热温变测量仪分别对样品的结构、等温磁熵变和绝热温变进行了测量.实验结果表明,经过两种不同热处理工艺处理的化合物都形成了Fe2P型六角结构,空间群为P62m,在经过淬火处理的Mn1..Fe0 eP0..Si0.56化合物中存在少量的(Mn,Fe) 5Si3第二相,空间群为P63/mcm.样品的居里温度都在室温附近,在278 ～296 K之间变化,不同热处理工艺对化合物的居里温度具有一定的影响.经过淬火处理的化合物存在较小的热滞和较大的等温磁熵变,两种化合物的热滞都由自然冷却处理时的5K降低到淬火处理时的3K.当Si的含量分别为0.56和0.57时,与经过自然冷却处理的化合物相比,经过淬火处理的化合物的最大磁熵变分别提升了33％和20％.在经过淬火处理的Mn1.35Fe0.65P0.44Si0.56化合物磁熵变最大,磁熵变的最大值为4.3J·kg-1·K-1.经过自然冷却处理的Mn1.35 Fe0.65P0.44 Si0.56化合物的最大绝热温变为1.2K.低成本的原料、较小的热滞、理想的制冷温区和较大的磁热效应使得Mn1.35 Fe0.65P1-xSix这一系列化合物在室温磁致冷方面有应用前景.     

La0.6Pr0.4Fe11.4Si1.6B0.2合金及其氢化物的磁热效应

研究了La0.6Pr0.4Fe11.4Si1.6B0.2合金及其氢化物La0.6Pr0.4Fe11.4Si1.6B0.2Hy的制备工艺与磁热效应。室温XRD分析与SEM成分分析表明La0.6Pr0.4Fe11.4Si1.6B0.2合金主相为NaZn13型立方结构(空间群为Fm-3c),存在富La相(空间群为P4/nmm)与富Fe相。氢化物La0.6Pr0.4Fe11.4Si1.6B0.2Hy的晶格常数a由合金的1.2295 nm增大到1.2491 nm。DSC测定氢化物的氢含量y约为1.7。磁性测量结果表明:氢化物La0.6Pr0.4Fe11.4Si1.6B0.2Hy的居里温度TC由合金的198 K增至325 K,提高了127 K。在0～1.5 T外磁场下合金与氢化物最大磁熵变-ΔSmMax均为9.1 J.kg-.1K-1。氢化物La0.6Pr0.4Fe11.4Si1.6B0.2Hy在室温下搁置190 d后物相与磁热效应基本保持不变。     

La0.8Ce0.2(Fe1-xCox)10.5Si2.5金属间化合物晶体结构和磁熵变特性研究

通过X射线衍射和磁性测量等手段对金属间化合物La0.8Ce0.2(Fe1-xCox)10.5Si2.5(x=0,0.02,0.04,0.06)系的结构、磁性以及磁熵变进行了研究.实验发现,La0.8Ce0.2(Fe1-xCox)10.5Si2.5系的晶体结构均保持立方NaZn13型结构.随着Co含量x的不断增大,晶格常数将单调减小,居里温度TC呈单调增加.当x=0.02时,该化合物在居里温度TC～239K具有较高的磁熵变︱ΔSM︱,在1 T的磁场下(ΔSM)max为2.87 J·kg-1·K-1.当x=0.04和0.06时,居里温度在室温附近,磁熵变有了一定程度的降低,但仍有可观的磁熵变.最后,对该系列合金作为近室温磁制冷工质的可能性作了适当地探讨.     

热处理工艺对LaFe_(10.85)Co_(0.65)Si_(1.5)C_(0.2)化合物成相的影响

分析了LaFe10.85Co0.65Si1.5C0.2在不同温度下,经过不同时间热处理后的相组成、微观组织特点、相变和磁性能。XRD衍射结果表明,经过温度高于1353 K的3天热处理后,LaFe10.85Co0.65Si1.5C0.2样品均得到了具有NaZn13结构的基体相。但是α-Fe的含量随退火温度增加而逐渐增加。样品的居里温度在300 K左右,在2.0 T外加磁场下最大磁熵变-ΔSM达到4.7 J·kg-1·K-1,是一种很好的室温磁致冷材料。     

LaFe11.2Co0.7Si1.1Bx合金在室温区的大磁热效应

从室温磁制冷目的出发,用工业纯原料制备了具有NaZn13型结构的稀土铁基化合物LaFe11.2Co0.7Si1.1Bx(x=0,0.1,0.2,0.25,0.3,0.4,0.5),并对其磁热效应进行了研究.实验结果表明,LaFe11.2Co0.7Si1.1Bx合金在室温区具有大磁热效应,在x＝0.2时,磁熵变|ΔSm|的峰值位于居里温度TC＝270K处,1.5T外磁场下达到7.3J/kg·K,直接测量绝热温变ΔTad达到2.7K;B元素作为置换原子和间隙原子进入NaZn13相,显著提高了合金的磁熵变和居里温度.     

Superconducting Transition Temperature in YBa2Cu4O8/La2/3 Ca1/3 MnO3 / YBa2 Cu4O8 Heterostructure

YBa2Cu4O8/La2/3 Ca1/3 MnO3/YBa2Cu4O8 （ Y-124/LCMO/Y- 124） heterostructure was prepared by facing-target sputtering technique. The oscillatory superconducting transition temperature was observed when the thickness of LCMO d L is larger than critical thickness d L^CR. The metal-insulator transition temperature can only be detected at d L 〉 d L^CR. The dependence on the spacer layer in LCMO/Y-124 systems suggests strongly the interplay of ferromagnetic and superconducting couplings.     

Visible luminescence of lanthanide ions in Ca3Sc2Si3O12 and Ca3Y2Si3O12

The crystalline materials Ca₃Sc₂Si₃O₁₂ and Ca₃Y₂Si₃O₁₂ were characterized by different crystal structures, as the former is a cubic garnet, while the latter is an orthorhombic compound. We investigated the optical spectroscopy of these materials doped with several trivalent lanthanide ions and compared the results for the two hosts. Polycrystalline samples were prepared by solid state reaction, both undoped and doped with the trivalent lanthanide ions Eu³⁺, Tb³⁺ and Sm³⁺. Emission, excitation and Raman spectra of these materials were measured at temperatures ranging from 300 to 10 K. The optical spectra were assigned and discussed, and the effects of the crystal structure of the host on the spectroscopic behaviour were addressed. The technological potential of these compounds in the field of optical materials and devices was discussed.     

Al2O3La2O3Y2O3/Cu复合材料的电弧侵蚀特性研究

采用喷射沉积和内氧化法制备出Al₂O₃La₂O₃Y₂O₃/Cu复合材料,研究该材料在直流20 V/20 A的工作条件下触点的电弧侵蚀特性,并与Al₂O₃/Cu材料进行了对比分析.利用电子天平、扫描电镜等方法分析电弧侵蚀后触点的质量变化和表面微观结构.结果表明,通过添加Y₂O₃、La₂O₃稀土氧化物颗粒,可有效降低触头材料的材料转移量.Al₂O₃La₂O₃Y₂O₃/Cu材料的抗熔焊性和抗烧损性优于Al₂O₃/Cu材料的性能.在直流阻性负载条件下Al₂O₃La₂O₃Y₂O₃/Cu阳极触头表面形成凹坑,阴极触头表面形成凸起,触点表面显示出浆糊状凝固物和喷发坑等电弧侵蚀形貌特征.      

CaO—SiO2—Na2O—CaF2—Al2O3—MgO保护渣系的Al2O3吸收速率和粘度

采用CaO-SiO2-Na2O-CaF2-Al2O3-MgO渣系,通过测定熔渣的粘度和Al2O3吸收速率,研究连铸保护渣的Al2O3吸收速率与粘度及化学成分之间的关系。在一定条件下,当CaO/SiO2为1.2左右时,粘度达到最小值,Al2O3吸收速率达到最大值,分别为0.10?Pa*s、8.403×10-4?kg*m-2*s-1。随着渣中Na2CO3含量、CaF2含量和MgO含量的增加,粘度减小,Al2O3吸收速率增大。随着渣中Al2O3含量的增加,粘度增大,Al2O3吸收速率减小。粘度为Al2O3吸收速率的主要控制因素。随着熔渣粘度的增加,连铸保护渣的Al2O3吸收速率逐渐减小。     

CaO-La2O3-B2O3-Eu2O3转光玻璃的合成及荧光性质

X射线衍射研究表明CaO-La2O3-B2O3-Eu2O3体系的玻璃化温度在1025℃附近.荧光光谱和ESR谱研究表明,在CaO-La2O3-B2O3-Eu2O3玻璃体系中存在着Eu2+和Eu3+两种价态离子. 316, 360, 379, 394, 413, 462和532nm锐线激发峰和592,616和650红区发射峰分别对应Eu3+的f-f激发跃迁和5D0-7FJ (J=1,2,3)跃迁发射;351nm和427nm宽带激发峰和蓝区发射分别对应Eu2+的5d-4f激发跃迁和发射.     

Fracture Behavior in Cu46.5Zr46.5Al7 and Cu46.5Zr41.5Al7Y5 Bulk Metallic Glasses

The interplay between chemical composition, plastic behavior, and fracture modes of Cu_46.5Zr_46.5Al₇ and Cu_46.5Zr_41.5Al₇Y₅ bulk metallic glasses (BMGs) was investigated by compression tests and fracture surfaces analyses. The aim was to explore the possibility of coupling physical, chemical, and hardness properties, with adequate macroscopic compressive plasticity. Cylindrical test samples, having a height-to-diameter ratio equal to 2, were machined and ground from as-cast bars and were tested in compression between lubricated plates, the displacement being measured by a clip-gage inserted between the plates. Y free BMG engineering stress-strain curves show a plastic behavior consisting of successive sudden stress drops and linear reloading segments. A detailed analysis of these features was performed to yield a correlation between the plastic deformation steps and the released elastic energy associated with each serration.     

CaO--TiO2--Fe2O3三元系中Ca3TiFe2O8的生成机理

钒钛磁铁矿是烧结矿重要的原料之一,Ca₃TiFe₂O₈作为钒钛烧结矿中矿物被发现之后,其生成机理尚不明确.本文采用X射线衍射分析、元素能谱分析和TG-DSC分析相结合的方法,研究了Ca₃TiFe₂O₈的生成机理以及不同温度、CaO与TiO₂含量下Ca₃TiFe₂O₈的生成规律.实验结果表明,Ca₃TiFe₂O₈由Ca₂ Fe₂O₅和CaTiO₃反应生成,即CaO和Fe₂O₃反应生成Ca₂ Fe₂O₅;其后,与CaTiO₃反应生成Ca₃TiFe₂O₈.反应时间越长,Ca₃TiFe₂O₈的生成量越大,但反应温度对Ca₃TiFe₂O₈生成的影响并不明显.另外,还发现CaO含量越高,Ca₃TiFe₂O₈越易于生成,而且等摩尔Fe₂O₃和CaO下只要存在TiO₂,就会有Ca₃TiFe₂O₈生成.      

Effect of Fe2O3 Loading Amount on Catalytic Properties of Monolithic Fe2O3/Ce0.67Zr0.33O2 -Al2O3 Catalyst for Methane Combustion

Ce0.67Zr0.33O2-Al2O3 solid solution was prepared by the co-precipitation method. Fe2O3-based catalysts supported on the solid solution were obtained by the impregnation method. The article revealed that the optimal loading amount of Fe2O3 on Ce0.67Zr0.33 O2-Al2O3 in our experimental condition for catalytic combustion of methane was 8% （ mass fraction）. The prepared catalysts were characterized by BET, TPR, XRD analyses, and their catalytic activity was investigated after being calcined at 873 K and after being aged in water gas at 1273 K. When the loading amount of Fe203 was 8% （ mass fraction）, the catalyst held the highest activity, and the best temperature speciality and thermal stability. The complete-conversion temperature of methane for fresh and aged sample was 788 and 838 K, respectively. The range between the light-off temperature and the complete-conversion temperature was only 15 K. The characterization results of XRD indicated that Fe2O3 was well dispersed on the Ce0.67Zr0.33O2-Al2O3 matrix. The results of BET and TPR were in good harmony with the catalytic activity results.     

Magnetocaloric Effect of Ni56Mn18.8Ga24.5 Gd0.7 Alloy

Inrecent years materials with high magnetocaloriceffect (MCE) have attracted considerable attention ow-ingto its potential application as a magnetic refriger-ant .Many material systemsthat underwentthefirst-or-der magnetic transition have been found to exhibit agiant MCE. Their typical representatives areGd5(SixGe1 -x)4[1 ,2]and La (FexSi1 -x)13[3 ,4]alloys .Ni MnGa is aferromagnetic shaped memory alloy whichundergoes a reversible first-order structural phase tran-sition (SPT) with the …     

Al2O3-V2O5体系的热力学优化

在对Al₂O₃-V₂O₅体系相图、热力学数据以及晶体结构数据进行综述与评估的基础上,采用相图计算方法对Al₂O₃-V₂O₅体系进行热力学优化.液相采用修正的似化学模型进行描述,利用对近似处理液相中存在的短程有序.将液相模型的最大短程有序设置在AlVO₄处,将VO₄3-当作液相中V₂O₅的基本组成单元.体系中AlVO₄相看作线性化合物.计算结果很好的重现了选定的实验数据,获得了一套合理、可靠、自洽的模型参数用来描述体系中各相的热力学性质,为Al₂O₃负载V₂O₅型催化剂催化性能的提高打下坚实的基础.