高温液相有机溶剂法合成CrTe基无稀土硬磁纳米结构

发布时间：2018-05-29 07:23

本文选题：高温有机液相法 + Cr_2Te_3　；参考：《山西师范大学》2017年硕士论文

【摘要】：硬磁材料(永磁材料)在科学技术高速发展的当今社会有着十分广泛的应用,由于具有高的磁晶各向异性能(Ku)和高磁能积((BH)max),使硬磁材料不仅被广泛应用于清洁能源汽车、风力发电、节能家电和工业电机等民用领域,更作为航空航天、武器装备、电子信息等尖端科学技术领域中的重要基础材料。近几年,稀土硬磁材料由于具有优异的磁学性能而成为研究热潮,但随着国家对稀土资源保护措施的实施,稀土元素的价格猛升,这使得低含量或零含量稀土的硬磁材料成为研究学者探索的新领域。本文通过高温液相反应法制备出CrTe基无稀土硬磁纳米结构,并研究了掺杂对所获得纳米材料的结构和性能的影响,得出以下结论:(1)以Fe(acac)_3为Fe源,采用高温液相反应法合成了Fe Te2球状磁性纳米颗粒,并对纳米颗粒的结构、磁学性能、成分及形貌进行了研究。通过以Cr(acac)_3为Cr源在FeTe_2纳米材料中成功掺杂了3d过渡金属Cr元素,掺杂后的FeTe_2纳米微粒趋向于形成均匀且分散性更好的的球形纳米粒子,相比未掺杂的Fe Te2纳米颗粒来说有更窄的粒径分布。其中,当x=0.15时,达到3d过渡金属Cr元素的最优掺杂值,此时Fe_(0.85)Cr_(0.15)Te_2在室温下的饱和磁化强度可以达到7.34 emu/g,高出纯FeTe_2纳米颗粒的20倍。这是由于Fe-Fe通过晶格畸变由反铁磁转变为铁磁,同时Cr-TeCr之间的超交换耦合也是铁磁性提高的原因之一。(2)由于Cr-Te-Cr之间强的铁磁相互作用,我们以Cr(CO)6为Cr源采用高温液相反应法首次合成出了以六角Cr_2Te_3为硬磁相以单斜m-Cr5Te8为软磁相的软/硬磁交换耦合的磁性纳米材料。并对所得到纳米结构进行了物相结构分析和磁性分析,研究了不同比例下Cr-Te相的磁性变化规律。当前驱体比例为Cr:Te=1:1.8时,得到Cr_2Te_3棒状纳米结构的最优硬磁相,矫顽力可以高达9.63k Oe,饱和磁化强度和剩磁分别是23.04 emu/g和9.85 emu/g。大的磁晶各向异性常数来源于较低的对称性和CrTe相强的自旋-轨道耦合作用,其强铁磁性来源于Cr-Te-Cr的超交换耦合作用。软/硬磁耦合作用的强弱可以通过调整Cr:Te前驱体的初始比例来进行改进。当Cr过量时有利用硬磁Cr_2Te_3相的形成,当Te过量时则有利于软磁m-Cr_5Te_8相的形成。(3)在成功制得Cr_2Te_3硬磁纳米材料的基础上,我们基于3d过渡金属元素掺杂可降低晶格的对称性从而有效优化纳米材料的磁学性能这一原理,对Cr_2Te_3硬磁纳米材料进行了3d过渡金属M(M=Mn、Fe、Co、Ni)元素掺杂,当x=0.2时,不同的3d过渡金属均进入Cr_2Te_3晶格,所有样品的峰型和峰数都与六角Cr_2Te_3相吻合,没有M、Te、Cr及其氧化物等杂峰出现,且Cr_(1.8)Co_(0.2)Te_3硬磁材料的磁学性能达到最佳。此时,我们系统研究了Co掺杂对Cr_2Te_3结构、形貌以及磁学性能的影响。研究表明,当x=0.4时,Hc达到最大值14.01 k Oe,为Cr_2Te_3硬磁材料的1.5倍,此时所制得的纳米材料主相为硬磁相。总之,我们采用高温有机溶剂法首次合成Cr_2Te_3无稀土硬磁纳米相。通过3d过渡金属掺杂的方法制备出磁学性能更加优异的Cr_(2-x)M_xTe_3硬磁纳米材料,该方法为研究Cr基无稀土硬磁纳米材料的制备奠定了重要基础。
[Abstract]:Hard magnetic materials (permanent magnetic materials) are widely used in the modern society with high speed of science and technology. Because of high magnetocrystalline anisotropy (Ku) and high magnetic energy product ((BH) max), hard magnetic materials are not only widely used in clean energy vehicles, wind power, energy saving appliances, industrial motors and other civil fields, but also as aeronautics and Astronautics. In recent years, rare earth hard magnetic materials have become a research upsurge in recent years because of their excellent magnetic properties. However, with the implementation of rare earth resources protection measures, the price of rare earth elements has risen sharply, which makes the hard magnetic materials with low or zero content of rare earth become a hard magnetic material. In this paper, the CrTe based hard magnetic nanoscale nanostructures were prepared by high temperature liquid phase reaction method. The influence of doping on the structure and properties of the nanomaterials obtained was studied. The following conclusion was drawn: (1) Fe Te2 spherical magnetic nanoparticles were synthesized by Fe (ACAC) _3 as the Fe source. The structure, magnetic properties, composition and morphology of rice particles are studied. The 3d transition metal Cr elements are successfully doped by Cr (ACAC) _3 as Cr source in FeTe_2 nanomaterials. The doped FeTe_2 nanoparticles tend to form uniform and better dispersed spherical nanoparticles, which are narrower than those of the undoped Fe Te2 nanoparticles. The optimal doping value of the 3d transition metal Cr element is reached at x=0.15. At this time, the saturation magnetization of Fe_ (0.85) Cr_ (0.15) Te_2 at room temperature can reach 7.34 emu/g and 20 times higher than that of pure FeTe_2 nanoparticles. This is due to the transformation of Fe-Fe through lattice distortion from antiferromagnetic to ferromagnetic, and the superswitching between Cr-TeCr. Coupling is also one of the reasons for the improvement of ferromagnetism. (2) because of the strong ferromagnetic interaction between Cr-Te-Cr, we first synthesized a magnetic nanomaterial with a soft / hard magnetic exchange coupling of a hard magnetic phase with a monoclinic m-Cr5Te8 as a soft magnetic phase by high temperature liquid phase reaction with Cr (CO) 6 as Cr source. The phase structure analysis and magnetic analysis are used to study the magnetic change law of Cr-Te phase under different proportions. When the current displacement ratio is Cr:Te=1:1.8, the optimal hard magnetic phase of the Cr_2Te_3 rod like nanostructure is obtained, the coercive force can be as high as 9.63k Oe, and the saturation magnetization and remanence are 23.04 emu/g and 9.85 emu/g. large magnetocrystalline anisotropy constants, respectively. Due to the lower symmetry and the spin orbit coupling of the CrTe phase, the strong ferromagnetism comes from the super exchange coupling of Cr-Te-Cr. The strength of the soft / hard magnetic coupling can be improved by adjusting the initial proportion of the Cr:Te precursor. When the Cr overdose is excessive, the formation of the hard magnetic Cr_2Te_3 phase is beneficial to the softening of the Te excess. The formation of magnetic m-Cr_5Te_8 phase. (3) on the basis of the successful Cr_2Te_3 hard magnetic nanomaterials, we based on the 3d transition metal element doping can reduce the symmetry of the lattice and effectively optimize the magnetic properties of nanomaterials. The Cr_2Te_3 hard magnetic nanomaterials are doped with 3d transition metal M (M=Mn, Fe, Co, Ni) elements, when x=0.2, The different 3d transition metals all enter the Cr_2Te_3 lattice. The peaks and peaks of all the samples are in accordance with the six angle Cr_2Te_3, and there is no M, Te, Cr and their oxides, and the magnetic properties of Cr_ (1.8) Co_ (0.2) Te_3 hard magnetic materials are best. At this time, we systematically studied the shadow of Co doping on Cr_2Te_3 structure, morphology and magnetic properties. The study shows that when x=0.4, Hc reaches the maximum value of 14.01 K Oe, which is 1.5 times of Cr_2Te_3 hard magnetic material, and the main phase of the nanomaterials is hard magnetic phase. In a word, we first synthesize Cr_2Te_3 no rare earth hard magnetic nanophase by high temperature organic solvent method. The more excellent Cr_ (Cr_) is prepared by the 3d transition metal doping method. 2-x) M_xTe_3 hard magnetic nanomaterials, which laid an important foundation for the preparation of Cr based hard earth magnetic materials without rare-earth elements.
【学位授予单位】：山西师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1

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