A novel germanate, Cu2Fe2Ge4O13, with a four tetrahedra oligomer

The structure of Cu₂Fe₂Ge₄O₁₃, previously thought to be CuFeGe₂O₆, has been determined from single-crystal X-ray diffraction data to be monoclinic, P2₁/m, a=12.1050(6), b=8.5073(4), c=4.8736(2) Å, β=96.145(1)°, Z=2, with R1=0.0231 and wR2=0.0605. The unique structure has an oligomer of four germanate tetrahedra, cross-linked laterally by square-planar copper ions, joined end-to-end by a zigzag chain of edge-sharing iron oxide octahedra. Running along the a-direction the metal oxide chain consists of alternating Cu-Cu and Fe-Fe dimers. A hypothetical series of homologous structures (Cu_n−2Fe₂Ge_nO_3n+1 with n=3,4,…,∞) with different length germanate oligomers is proposed, where as n increases, the infinite chain of the CuGeO₃ is approached. In this context, Cu₂Fe₂Ge₄O₁₃ is viewed as being built from blocks of CuGeO₃ and the Fe oxide chains. This material has significance to the study of low-dimensional mixed-spin systems.     

Field-Induced Slow Magnetic Relaxation in CoII Cyclopropane-1,1-dicarboxylates

New Co^II substituted malonate field-induced molecular magnets {[Rb₆Co₃(cpdc)₆(H₂O)₁₂]∙6H₂O}_n (1) and [Cs₂Co(cpdc)₂(H₂O)₆]_n (2) (where cpdc²⁻ stands for cyclopropane-1,1-dicarboxylic acid dianions) were synthesized. Both compounds contain mononuclear bischelate fragments {Co^II(cpdc)₂(H₂O)₂}²⁻ where the quasi-octahedral cobalt environment (CoO₆) is complemented by water molecules in apical positions. The alkali metal atoms play the role of connectors between the bischelate fragments to form 3D and 2D polymeric structures for 1 and 2, respectively. Analysis of dc magnetic data using the parametric Griffith Hamiltonian for high-spin Co^II supported by ab initio calculations revealed that both compounds have an easy axis of magnetic anisotropy. Compounds 1 and 2 exhibit slow magnetic relaxation under an external magnetic field (H_DC = 1000 and 1500 Oe, respectively).     

基于永磁体间的磁性负刚度的分析与优化

为了有效地降低磁性负刚度结构的非线性程度,从简单三磁体结构出发,引入新型负刚度结构模型——五磁体对称结构,运用MATLAB建立新型负刚度结构的磁力学模型并应用Ansoft Maxwell进行仿真验证.研究永磁体间的相对位置参数对五磁体对称结构的负刚度曲线走势的影响,在微幅振动下对基于磁引力的负刚度曲线拟合后使用谐波平衡...     

超导磁体螺栓结合面低温振动特性研究

振动特性对于超导磁体的各类工程应用具有重要意义,螺栓法兰盘连接是超导磁体系统的一种常见的支撑结构类型,然而螺栓结合面在低温条件下振动特性的相关研究目前尚少见报道.本研究中设计加工了简化的连接结构,在室温和液氮温度对其螺栓结合面进行振动特性的测试分析.接下来,采用集中质量法进行建模,并利用振型、频率与质量矩阵、刚度矩阵的关系求解了不同螺栓预紧力情况下的刚度矩阵,得到了系统总刚度和结合面刚度.使用上述方法对振动测量数据计算发现,该结构的系统总刚度与结合面刚度都随着预紧力增大而增大,同时液氮低温条件可使系统总刚度和结合面刚度进一步增大.     

用于高功率微波器件的永磁体的设计和测试

报道了用于高功率相对论返波管振荡器的永磁体的设计和试制。以Halbach阵列结构为基础, 通过选择高性能的永磁材料, 调整磁钢的充磁方向、排列方式和尺寸, 优化设计了可用于某相对论返波管振荡器的永磁体结构, 其均匀区磁场强度0.98 T。采用粒子模拟方法, 进行了永磁体与返波管振荡器的一体化设计, 设计结果表明：器件输出功率超过1 GW, 设计的永磁体能够满足器件对磁场强度和位形的要求。对永磁体进行了试制和测试, 测试结果为：均匀区磁场0.88 T, 均匀区长110 mm, 磁体重量约306 kg。     

高功率光隔离器永磁系统的理论研究与优化

基于阵列永磁体的特点以及光隔离器对磁场的需求设计了两种适用于高功率隔离器的永磁系统,分析了其磁场分布、磁场非均匀性对隔离度的影响,研究了磁体装配误差对磁场的影响。研究结果表明：通过引入斜向磁化永磁体,选择合适的磁化角度和磁体长度,可以提高永磁体的磁场强度,大幅度减小旋转器所需磁光晶体长度;受磁场非均匀性影响的隔离度与磁光晶体的孔径、长度以及入射激光的光斑半径有关,当晶体长度一定时,减小晶体半径和入射光的半径可以显著提高隔离度。在入射光半径为1.5 mm、磁光晶体半径5 mm时,对应的隔离度分别为105.8 dB和45.4 dB。     

高功率速调管聚焦磁场设计研究

 国产45 MW速调管是在原国产30 MW HK-1型速调管的基础上改进和发展起来的,其聚焦磁场设计也是参照30 MW速调管聚焦磁场设计并在其基础上加工改造完成。为此必须对旧聚焦系统进行改造,设计出符合需要的磁场分布,以满足45 MW速调管工作的需要。首先从理论上找出速调管工作时的理想磁场值,根据该磁场分布设计出相应的线圈结构;其次根据45 MW速调管的结构尺寸,对30 MW速调管的线圈支架进行改造,利用旧线圈和新支架组成新的聚焦系统;最后,根据理论模拟和测试结果,调整和优化各组线圈的电流值,给出速调管工作时的各组聚焦电源运行参考值。叙述了新聚焦线圈的理论设计和测试分析,包括新线圈支架的设计、水冷系统与线圈的结构安排和整体的测试结果,最后根据速调管高功率测试运行状态给出速调管工作时的聚焦线圈电流的参考值。     

Thermo-induced structural transformation with synergistic optical and magnetic changes in ytterbium and erbium complexes

Dinuclear ytterbium and erbium based bifunction complexes Ln₂L₂(depma₂)Cl₂ (1-Ln, Ln = Yb and Er, H₂L = N¹,N³-bis(salicylideneimino)diethylenetriamine, depma₂ = dimerized 9-diethyl-phosphonomethylanthracene) are reported. They undergo thermo-induced consecutive phase transitions, first the dissociation of depma₂ ligand forming LnL(depma)Cl (2-Ln) and then the release of chloroethane forming LnL(epma) (3-Ln, epma = 9-ethylphosphonomethylanthrancene). The structural transformations are accompanied with synergetic switch of the luminescence in visible and NIR regions and also magnetic dynamics.     

Heterometallic Coii-Lii carboxylate complexes with N-heterocyclic carbene,triphenylphosphine and pyridine: a comparative study of magnetic properties

Heterometallic Coii-Lii compounds with N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), tri phenylphosphine (Ph3P) and pyridine (py), [Co2Li2(Piv)6(IMes)2] (Piv is the anion of pivalic acid), [Co2Li2(Piv)6(Ph3P)2] and [Co2Li2(Fur)6(py)2] (Fur is the anion of 2-furoic acid), respectively, have been prepared and structurally characterized by X-ray crystallography. Easy-plane magnetic anisotropy in Coii complexes with pseudo-tetrahedral cores CoO3X (X = C, P and N) was revealed by measuring the magnetic properties together with quantum-chemical calculations using the SA-CASSCF/NEVPT2 approach. The field-induced slow magnetic relaxation of the complexes was mainly attributed to the Raman and direct processes.     

烧结NdFeB断裂方式及其断面的微观结构

经熔炼、制粉、成型、烧结和回火等工序制备了成分为Nd33Fe65.95B1.05（质量分数）的烧结NdFeB磁体,将铸锭样品和烧结磁体样品折断,并采用扫描电子显微镜和金相显微镜对二者的断裂方式和断面的微观结构进行了对比分析。结果表明：烧结NdFeB铸锭的断裂方式为沿晶断裂,断面处有较多的层状富钕相,多边形的主相较为完整;烧结NdFeB磁体既有沿晶断裂也有穿晶断裂,但是以沿晶断裂为主。分析造成烧结NdFeB磁体断裂的原因为：（1）其微观结构中有大量的孔洞等缺陷,这是外部原因;（2）微观结构中占主要成分的主相的维氏硬度为6 235.94 N·mm-2,富钕相的维氏硬度为5 947.42 N·mm-2,二者有较大的差距,这是本征因素。针对磁体中孔洞和夹杂等缺陷存在而造成的断裂提出了相应的解决措施。