共查询到19条相似文献,搜索用时 171 毫秒
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膨胀石墨CuCl2-NiCl2-层间化合物磁性研究 总被引:5,自引:0,他引:5
在膨胀石墨CuCl2-NiCl2-GICs合成和电性研究基础上,采用MODEL155振动磁强计测量了GICs在0~7.958×105A/m磁场强度下的磁化强度、磁化率.发现CuCl2-NiCl2引入石墨层间,形成GICs后磁性升高.与膨胀石墨相比,GICs的磁化率大约提高了2~3个数量级.GICs的磁性不但由石墨的抗磁性转变成为顺磁性,磁化曲线斜率由负变正,而且随着阶结构、 CuCl2和 NiCl2比例变化, GICs磁性发生变化.氯化镍含量在 50%以下,表现为强烈的顺磁性;50%时,磁化曲线出现最大值,表现为铁磁性.>50%,达到60%、80%时,铁磁性更明显.GICs阶数升高,铁磁性降低. 相似文献
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Co-Ni磁控形状记忆合金的相变及显微结构 总被引:4,自引:0,他引:4
Co基合金中存在从fcc到hcp的马氏体相变,其奥氏体-马氏体界面完全共格,层错能较低,马氏体相变的驱动力很小,易通过外磁场诱发a/6〈112〉Shockley不全位错的移动引起相变而产生对外的应变输出,是一种理想的磁控形状记忆候选材料。本文研究了Co-Ni合金的金相组织和透射电子显微结构,测定了一组Co-Ni合金的马氏体相变及其逆转变温度。研究表明:Co-Ni合金的马氏体组织呈有规则的条片状,马氏体相变温度随Ni含量的增加而降低,其母相中存在层错,母相的饱和磁化强度高达124Am2·kg-1,是典型磁控形状记忆材料Ni2MnGa的近两倍。 相似文献
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利用电介质的平均能带模型计算了R型六方铁氧体BaTi2Fe4O11和BaSn2Fe4O11的化学键参数,得到BaTi2Fe4O11的2a、4f、4e、6g各晶位平均共价性分别为0.062、0.354、 0.309、 0.361; BaSn2Fe4O11的相应晶位平均共价性分别为0.062、 0.353、 0.183、0.255.应用化学环境因子计算了57Fe、119Sn在R结构中的穆斯堡尔同质异能位移。确定了57Fe,119Sn的价态和占位情况. 相似文献
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非均相沉淀法制备Al2O3-YAG复相陶瓷 总被引:1,自引:0,他引:1
本文测量了YAG粉体的ξ电位,通过调节pH值获得均匀分散的YAG水悬浮液.采用非均相沉淀方法获得YAG分布均匀的Al2O3-YAG复合粉体.通过热压烧结得到致密烧结体,YAG的加入对烧结温度的影响不大.Al2O3-5vol%YAG复相陶瓷的抗弯强度为485MPa,断裂韧性为4.2MPa·m1/2,均高于单相Al2O3陶瓷,数据的重复性好于球磨混合所制备的样品.通过TEM观察,YAG颗粒均匀分布于整个样品中,表明通过非均相沉淀制粉可以获得YAG颗粒分布均匀的Al2O3-YAG复相陶瓷. 相似文献
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Jian Liu Nils Scheerbaum Sandra Kauffmann‐Weiss Oliver Gutfleisch 《Advanced Engineering Materials》2012,14(8):653-667
As a new class of magnetically driven active materials, magnetic shape memory (MSM) alloys show large strains of up to 10% in Ni2MnGa single crystal with a modulated martensitic structure. The magnetic field induced twin boundary motion can be exploited for actuators, sensors, and as it is an energy dissipating process, also for vibration damping devices. However, single crystals of Ni2MnGa are difficult to prepare and are inherently very brittle. One solution is the use of aligned MSM particles suspended in a stiffness‐matched polymer matrix. In this review, we focus on the preparation and characterization of textured NiMn‐based MSM composite. Essential issues, e.g., the criterion of polymer selection and the interface of MSM particles and polymer are discussed. Second aspect of the paper is to review recent developments in metamagnetic shape memory Ni? Mn‐(In,Sn,Sb) systems which exhibit field‐driven multifunctional properties such as magnetocaloric effect, magnetoresistant change, magnetoelectricity, and thermoelectricity. 相似文献
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Cui Y.T. Liu Z.H. Zhang M. Liu G.D. Li Y.X. Wang W.L. Wu G.H. 《IEEE transactions on magnetics》2005,41(3):1086-1088
The temperature dependence of the magnetic field-induced strain (MFIS) and the field-controlled shape memory effect in Ni/sub 52/Mn/sub 16.4/Fe/sub 8/Ga/sub 23.6/ single crystals were investigated by measuring the MFIS and measuring the magnetic field-enhanced transformation strain with a field bias applied in the [001] and [010] directions of the parent phase, respectively. The results show that such material combined with the martensitic transformation can product large field-enhanced transformation strain and large MFIS. The strain accompanying the martensitic transformation is -1.61% in zero field and can be enhanced to -3.30% by a field of 960 kA/m. A MFIS of 1.04% has been induced along [001] in unstressed crystals with saturated magnetic field of 600 kA/m applied along the same direction at near martensitic transformation temperature. It was found that the MFIS is almost temperature independent; the maximum decrease of the saturated MFIS is less than 10%, from 265 K to 100 K. This well-behaved temperature response makes this alloy particularly valuable for industrial and military smart actuators and transducers. Furthermore, it was found that the direction in which the MFIS has the largest value is always the [001], namely, the growth direction of the crystals. 相似文献
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Based on an existing micromechanical constitutive model for Ni2MnGa ferromagnetic shape memory alloy single crystals, a three-dimensional quasi-static isothermal incremental constitutive model that is suitable for finite element analysis is derived by using Hamilton's variational principle. This equation sets up the coupling relation between the magnetic vector potential and the mechanical displacement. By using the incremental equation and ANSYS software, the mechanical behaviors of martensitic variant reorientation for Ni2MnGa single crystals are analyzed under magneto-mechanical coupling action. And the finite element results agree well with the experimental data. The methods used in the paper can well describe the mechanical behaviors of the material in complex fields. 相似文献
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Anja Backen Srinivasa Reddy Yeduru Anett Diestel Ludwig Schultz Manfred Kohl Sebastian Fähler 《Advanced Engineering Materials》2012,14(8):696-709
Active materials such as piezoelectrics are established in the field of microsystems application despite their low achievable strains which often require the integration of additional gear mechanisms. The ongoing search for new active materials has focused on magnetic shape memory (MSM) alloys such as Ni? Mn? Ga since they combine macroscopic strains of up to 10% with a cycling frequency well above the frequencies of conventional thermal shape memory alloys. The present review focuses on preparation and analysis of Ni? Mn? Ga films that can eventually be integrated in microsystems. Single crystal like films are prepared by epitaxial growth on suitable substrate materials. Since the magnetically induced reorientation of variants is blocked by a rigid substrate, we present different methods for releasing films from the substrates. We show that the sacrificial layer technology is the most promising approach. Further processing of the freestanding film requires a microtechnology which is adjusted to the film laminate structure. The properties of the freestanding films are compared with films on a rigid substrate. Although we observe stress‐induced twin boundary motion, the twinning stress is too high to be overcome by an external magnetic field. Therefore, it is necessary to develop suitable training methods to reduce the twinning stress below 2 MPa to enable the activation of the material by means of an external magnetic field. 相似文献
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采用定量金相、X射线衍射等手段,研究了在恒定磁场下加热到高于Tc或Af温度保温30min后水淬或空冷对多晶Ni2MnGa组织的影响。结果表明,在相同的热处理工艺下,外加磁场均能促进马氏体相的形成。同时,磁场热处理使马氏体孪晶变体的位向分布发生明显改变,产生不同程度的择优排列(磁织构);在经过优化的工艺条件下磁场热处理能使多晶Ni2MnGa的磁驱动形状回复应变得以提高。 相似文献
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磁驱动形状记忆合金是一种新型功能材料,由于兼具大的输出应变和高响应频率等综合特性,成为智能材料领域的研究热点之一.本研究首先总结了Ni-Mn-Ga合金在相变和磁致应变性能方面的特点,然后着重介绍了Co-Ni-Ga和Ni-Fe-Ga两类新型磁驱动记忆合金在结构、相变、形状记忆效应、磁性能等方面的研究进展,并对其中存在的问题进行了讨论. 相似文献
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Tobias Eichhorn Richard Hausmanns Peter Klaer Michael Kallmayer Hans‐Joachim Elmers Gerhard Jakob 《Advanced Engineering Materials》2012,14(8):687-695
We report on the structural and magnetic properties of epitaxial thin films of the ferromagnetic shape memory material Ni–Mn–Ga prepared by DC magnetron sputter deposition. Different substrate materials, i.e., MgO(100) and Al2O3(11?20) allow for a tailored epitaxial growth. Using a sacrificial chromium buffer layer freestanding epitaxial films are obtained. In combination with photolithography partially freestanding structures such as microbridges are fabricated. The complex martensite crystal structure in substrate‐constrained and freestanding films is studied by means of X‐ray diffraction. The identified asymmetric twin variant configuration is associated with a macroscopic surface pattern observed by optical microscopy. The absence of magnetic‐field induced strain in the (100) oriented samples is explained on basis of the detected twin variant configuration using a simplified model. Taking advantage of the thin film geometry spectroscopic methods are applied to the samples. The measurements provide the first experimental test for changes in the electronic structure of the involved 3d metals during a martensitic transition. Exploiting the X‐ray magnetic circular dichroism quantitative information on the element‐specific spin and orbital magnetic moments are accessed. In addition, angular‐dependent experiments allow us to trace the microscopic origin of the magnetic anisotropy in Ni2MnGa improving the fundamental understanding of this material. 相似文献
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《IEEE transactions on magnetics》2009,45(4):1919-1921