单晶Ni52Mn24Ga24的磁感生应变和磁增强双向形状记忆效应

铁磁性Heusler合金Ni2MnGa是近年开发的磁控制功能材料,已发现该材料结合马氏体相变可以产生大磁致伸缩（磁感生应变）和磁控制形状记忆效应两种应用功能。用磁悬浮冷坩埚提拉设备沿[001]方向生长了组分为Ni52Mn24Ga24的单晶,室温时沿该单晶样品[001]方向加磁场,在该方向获是了-0.6%的大磁感生应变。当磁场方向垂直于[001]方向时,样品在[001]方向的磁感生应变值为0.5%,同时该单晶样品在室温附近还具有可由磁场增强和控制的双向形状记忆效应。无磁场作用时,降低温度。样品在发生马氏体相变时,在[001]方向产生1.2%的收缩形变,随后升高温度,反马氏体相变时样品以同样的反应量膨胀,恢复到原来的形状,显示了特有的远需外应力协助的自发的双向形状记忆效应。其温度滞后只有10℃,如果在样品[001]方向加一个偏磁场,其形状记忆的应变往往量随磁场的增强而增大,在磁场为1.2T时可达4%,而当磁场转向[001]方向时,形状记忆的应变可以改变符号,本文指出产生大磁感生应变和磁增强双向形状记忆效应的关键是马氏体变体的择优取向。     

Ni_(52)Mn_(24)Ga_(24)金属间化合物的单晶生长和磁性功能

研究了 Ｎｉ５２Ｍｎ２４Ｇａ２４合金单晶在磁场作用下能产生的目前最大的磁致伸缩应变．发现了该材料的双向相变应变效应以及磁场对此的增强现象．在 １．２ Ｔ磁场的作用下,可逆的相变应变达 ４％以上实现这一结果的关键条件是马氏体变体的择优取向报道了获得马氏体变体的择优取向样品的单晶生长特性和后处理方法根据前人报道的理论模型分析了实验结果,指出磁感生应变的物理机制是磁场提供的 Ｚｅｅｍａｎ能驱动变体间孪晶界的移动     

Ni48Mn33Ga19合金的马氏体相变和磁性形状记忆效应

铁磁性Heusler型合金Ni2MnGa是近年来开发的新型磁控制功能材料，但其马氏体相变温度通常远远低于室温，不利于实际应用。本文研究了多晶Ni48Mn33Ga19合金的马氏体相变特征，发现该合金的马氏体相变温度已提高到室温以上。在室温下，分别测量了不同条件下制备的试样的磁场诱发应变，提出了增大材料磁致应变的有效方法。     

单晶Ni_(52)Mn_(24)Ga_(24)的磁感生应变和磁增强双向形状记忆效应

铁磁性Heusler合金Ni2 MnGa是近年开发的磁控制功能材料 ,已发现该材料结合马氏体相变可以产生大磁致伸缩 (磁感生应变 )和磁控制形状记忆效应两种应用功能。用磁悬浮冷坩埚提拉设备沿 [0 0 1]方向生长了组分为Ni52 Mn2 4 Ga2 4 的单晶。室温时沿该单晶样品 [0 0 1]方向加磁场 ,在该方向获得了 - 0 6 %的大磁感生应变。当磁场方向垂直于 [0 0 1]方向时 ,样品在 [0 0 1]方向的磁感生应变值为 0 5 %。同时该单晶样品在室温附近还具有可由磁场增强和控制的双向形状记忆效应。无磁场作用时 ,降低温度 ,样品在发生马氏体相变时 ,在 [0 0 1]方向产生1 2 %的收缩形变。随后升高温度 ,反马氏体相变时样品以同样的应变量膨胀 ,恢复到原来的形状 ,显示了特有的无需外应力协助的自发的双向形状记忆效应。其温度滞后只有 10℃。如果在样品的 [0 0 1]方向加一个偏磁场 ,其形状记忆的应变量随磁场的增强而增大。在磁场为 1 2T时可达 4%。而当磁场转向 [10 0 ]方向时 ,形状记忆的应变可以改变符号。本文指出产生大磁感生应变和磁增强双向形状记忆效应的关键是马氏体变体的择优取向。     

热处理工艺对制备粘结Ni52Mn24.4Ga23.6磁体的影响

采用真空感应熔炼法制备了多晶Ni52Mn24．4Ga23．6合金,用粉末压缩压制的方法制作粘结Ni52Mn24．4Ga23．6磁体;通过显微组织观察和差热分析(DSC)的方法研究了不同的浇铸方式和退火工艺对多晶Ni52Mn24．4Ga23．6合金铸锭组织和性能的影响。结果表明,缓慢冷却的合金液能得到晶粒粗大的合金铸锭;两步退火工艺能使合金铸锭具有确定的马氏体转变点,并促进马氏体变体的形核和长大。     

Ti含量对Ni53Mn23.5Ga23.5-xTix铁磁性形状记忆合金组织和性能的影响

采用光学显微镜、示差扫描热分析、交流磁化率测试和室温压缩试验等方法系统研究Ti含量对Ni53Mn23.5Ga23.5-xTix (x=0, 0.5, 2, 3.5, 8, 15)合金的显微组织、相变行为、力学行为和磁学特性的影响规律。结果表明：Ti元素在合金中的极限固溶度低于15%;随着Ti含量的增加,合金的相变温度和断裂强度及断裂应变先逐渐增加后降低,其断裂方式由沿晶断裂转变为穿晶断裂再到沿晶断裂;而合金的居里温度随Ti含量的增加逐渐降低     

铁磁形状记忆合金Ni50Mn28.5Ga21.5单晶变体强磁场处理及磁致应变

采用光子加热悬浮区熔法制备出直径7 mm、长60 mm的Ni50Mn28.5Ga21.5单晶.分别切割成8.1 mm×4.3mm×4.4 mm和直径7mm,长38.9 mm的两块单晶体,利用10 T强磁场进行变体处理获得近似单变体,并获得了5.2%的大磁致应变.磁致应变压力效应的测试表明,随压应力增大,孪晶再取向的临界磁场强度增大,磁致应变降低.     

Fe81Ga19合金<001>取向单晶生长及磁致伸缩性能

采用悬浮区熔法,加入籽晶控制生长取向,以4 mm/h的生长速度,制备了轴向〈001〉择优取向的Fe81Ga19单晶.极图测试结果发现,采用偏离轴向〈001〉方向约5°的籽晶生长得到的单晶,生长始端和生长末端轴向取向分别偏离〈001〉取向5°和4°,上下取向差仅为1°.另一单晶采用轴向〈001〉取向籽晶生长得到,当施加6...     

快速凝固Ni61Al24Mn15高温形状记忆合金薄带的相变和结构

快速凝固工艺制备的Ni61Al24Mn15合金薄带具有细晶粒组织。明显改善了合金的变形性能,合金薄带在拉伸和弯曲两种状态下形状记忆回复率都达到了 70％以上,且热弹性马氏体相变温度都高于150℃,高温区形状记忆效应的产生与合金薄带中面心立言和密排六方结构志氏体体心立方结构母相之间热弹性马氏体相变有关。     

快速凝固Ni48Mn33Ga19合金的加热相变组织和结构的研究

采用铜模吸铸式快速凝固法制备了非化学计量成分的Ni48Mn33Ga19合金,研究和比较了经常规冷却和吸铸式快速冷却工艺热处理后合金相变点以及组织和结构的变化规律。结果表明,加热相变过程均为两阶段相变过程;快速凝固工艺可使铸后热处理试样的相变温度接近室温;极高的冷却速率提高了组织均匀性;Ni48Mn33Ga19合金组织经热处理后由奥氏体转变成10层马氏体。     

Ni50Mn43Sn7磁性形状记忆合金的机械合金化及其磁性能（英文）

利用机械合金化法制备Ni50Mn43Sn7磁性形状记忆合金粉末。采用X射线衍射(XRD)、扫描电镜(SEM)及振动样品磁强计(VSM)等分析手段研究了机械合金粉末的微观结构和磁性随球磨时间的变化。结果表明:在球磨过程中,依次形成一些Mn1.77Sn,MnSn2,Ni3Sn4,Ni3Sn2和Ni4Sn等中间相,随着球磨时间的增加,MnSn化合物与NiSn化合物逐渐结合而消失,球磨270h后,形成Ni2MnSn,机械合金化完成。在球磨初期,粉末晶粒尺寸急剧减小,球磨90h后晶粒尺寸基本保持稳定,颗粒以絮状团聚结构存在。由于球磨过程中粉末得到细化等原因,饱和磁化强度Ms随球磨时间的增加而减少,矫顽力(Hc)随球磨时间的增加先增大,球磨90h后急剧减小。     

USb2单晶的生长及磁性和输运性质研究

采用Sb自助熔剂法成功生长高质量的USb₂单晶,并研究了磁化率、电阻、磁阻和比热等性质。研究表明,中等关联强度的USb₂中的5f电子具有巡游和局域双重特征。USb₂中的5f电子在260 K附近开始发生相干,203 K由顺磁态转变为反铁磁态,进行费米面的重构。在113 K以下局域的5f电子与传导电子发生第一次杂化使费米面附近电子结构发生变化。在54 K以下通过第二次杂化使得费米面附近形成了杂化能隙。在更低温度下晶体场效应对物理性质也产生了一定的影响。     

Transformation behavior of shock-compressed Ni48Ti52

The transformation behavior on shock-loaded Ni₄₈Ti₅₂ has been studied by employing a differential scanning calorimeter in order to reveal residual effects of shock treatment in the thermoelastic martensitic transformation of Ni₄₈Ti₅₂, exhibiting a shape memory effect between a high temperature phase and a low temperature phase. The shock treatment of Ni₄₈Ti₅₂ was performed by a flyer plate impact method with the flyer velocity of 1.2 km s⁻¹. The height of the exothermic and endothermic peaks due to the transformation of shock-treated Ni₄₈Ti₅₂ become small and their temperature regions are expanded. Although the increase of the number of the thermal cycles induces no intermediate phase on Ni₄₈Ti₅₂ before the shock treatment to result in a one-step transformation, a three-step transformation is observed after annealing at an appropriate temperature on the shock-treated Ni₄₈Ti₅₂, which correspond to the appearance of two intermediate phases. The shock treatment increases non-chemical free energy such as strain energy and interfacial energy of a phase boundary, which is attributable to the microstructure of shock-induced dislocations and an increase of the disorder in the lattice of ordered Ni₄₈Ti₅₂, resulting in the three-step transformation. Therefore, it is thought that the shock treatment can make it possible to achieve a new state on NiTi.     

Magnetic and magnetocaloric properties in melt-spun and annealed Ni42.7Mn40.8Co5.2Sn11.3 ribbons

The Ni_42.7Mn_40.8Co_5.2Sn_11.3 ribbons were prepared by melt spinning. After heat treatment, the martensitic transformation temperature and Curie temperature of austenite of the annealed ribbons increased remarkably. Inverse and direct magnetocaloric properties were investigated in the melt-spun and annealed ribbons. The effective refrigerant capacities for these ribbons were discussed in this paper.     

Co1.2Mn0.8B化合物的磁性能与磁热效应

采用球磨和固相烧结相结合的方法制备了Co_(1.2)Mn_(0.8)B化合物,并对其晶体结构、磁性能和磁热效应进行了研究。结果表明,Co_(1.2)Mn_(0.8)B化合物的物相为Co_2B单相结构,具有CuAl2型体心正方晶体结构,空间群为I14/mcm;在居里温度TC=175 K附近,化合物发生了铁磁(FM)-顺磁(PM)二级磁相转变,热滞为0.7 K;Co_(1.2)Mn_(0.8)B化合物在外磁场0～5 T变化下的最大磁熵变ΔSM为1.17 J·(kg·K)~(-1),其对应的温度不随外场的变化而变化。     

Analysis of the thermal expansion characteristics of Ni53.6Mn27.1Ga19.3 alloy

Dilatation characteristics of Ni_53.6Mn_27.1Ga_19.3 alloy were measured in the temperature range of 20–360 °C. The coefficient of thermal expansion (CTE) decreased with increasing temperature in the temperature range of the existence of martensite. Three variants of martensite transformed gradually into austenite. Analysis of the dilatation characteristics showed that compression deformation of the alloy at room temperature produces two kinds of strain.     

Time effect of martensitic transformation in Ni43Co7Mn41Sn9

Effect of thermal arrest on the L2₁-tetragonal martensitic transformation in a NiCoMnSn shape memory alloy was investigated. The phenomenon was studied by interrupted heating/cooling in differential scanning calorimetry analysis. The experimental evidence indicates that the forward martensitic transformation continued to completion during cooling arrest between M_s and M_f. The same behavior was also observed for the reverse transformation on heating. These observations demonstrate that the L2₁-tetragonal martensitic transformation in the Ni₄₃Co₇Mn₄₁Sn₉ alloy is time dependent at the finite cooling rate.     

Ni48Co1Mn37In14- x Al x 磁性记忆合金马氏体相变、力学性能和耐腐蚀性能

采用电弧熔炼的材料制备方法,研究了微量的主族元素Al掺杂对Ni₄₈Co₁Mn₃₇In_14-xAl_x (0≤x≤2)磁性形状记忆合金显微组织、晶体结构、马氏体相变、力学性能和耐腐蚀性能的影响。结果表明：用Al替代部分In,合金的晶粒尺寸明显减小,掺杂2at%的Al元素,平均晶粒尺寸缩小到10 μm左右,大约为未掺杂样品的三十五分之一;当Al掺杂量在0.25at%~2at%时,金属Al完全固溶到基体中,而且Al在合金中的固溶度随掺杂量的增加有所提升,当Al掺杂量为2at%时,Al在基体中的固溶度接近2at%;随着Al对In的取代,室温下合金由L2₁立方奥氏体与单斜6M马氏体的两相结构转变为单一的6M调制马氏体相结构,晶胞体积逐渐减小,马氏体相变温度呈现上升趋势;合金抗压强度不断增大,Ni₄₈Co₁Mn₃₇In₁₂Al₂的抗压缩断裂强度与Ni₄₈Co₁Mn₃₇In₁₄相比提高了160%,压缩应变也由5.46%增加到6.36%;适量的Al替代In后,合金在人工海水中的耐腐蚀性能总体呈现不断增强的趋势,Ni₄₈Co₁Mn₃₇In₁₂Al₂合金的耐腐蚀性能明显高于Ni₄₈Co₁Mn₃₇In₁₄合金,且其耐腐蚀性接近于304不锈钢。     

Synthesis and electrochemical performance of Li(Ni0.8Co0.15Al0.05)0.8(Ni0.5Mn0.5)0.2O2 with core-shell structure as cathode material for Li-ion batteries

The core-shell structure cathode material Li(Ni_0.8Co_0.15Al_0.05)_0.8(Ni_0.5Mn_0.5)_0.2O₂ (LNCANMO) was synthesized via a co-precipitation method. Its applicability as a cathode material for lithium ion batteries was investigated. The core-shell particle consists of LiNi_0.8Co_0.15Al_0.05O₂ (LNCAO) as the core and a LiNi_0.5Mn_0.5O₂ as the shell. The thickness of the LiNi_0.5Mn_0.5O₂ layer is approximately 1.25 μm, as estimated by field emission scanning electron microscopy (FE-SEM). The cycling behavior between 2.8 and 4.3 V at a current rate of 18 mA g⁻¹ shows a reversible capacity of about 195 mAh g⁻¹ with little capacity loss after 50 cycles. High-rate capability testing shows that even at a rate of 5 C, a stable capacity of approximately 127 mAh g⁻¹ is retained. In contrast, the capacity of LNCAO rapidly decreases in cyclic and high rate tests. The observed higher current rate capability and cycle stability of LNCANMO can be attributed to the lower impedance including charge transfer resistance and surface film resistance. Differential scanning calorimetry (DSC) indicates that LNCANMO had a much improved oxygen evolution onset temperature of approximately 251 °C, and a much lower level of exothermic-heat release compared to LNCAO. The improved thermal stability of the LNCANMO can be ascribed to the thermally stable outer shell of LiNi_0.5Mn_0.5O₂, which suppresses oxygen release from the host lattice and not directly come into contact with the electrolyte solution. In particular, LNCANMO is shown to exhibit improved electrochemical performance and is a safe material for use as an electrode for lithium ion batteries.