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排序方式: 共有143条查询结果,搜索用时 15 毫秒
71.
Yajing ZhangGirija S. Chaubey Chuanbing RongYong Ding Narayan PoudyalPo-ching Tsai Qiming ZhangJ. Ping Liu 《Journal of magnetism and magnetic materials》2011,323(11):1495-1500
We report our recent results in synthesis and characterization of cobalt carbide (Co3C and Co2C) nanoparticles and nanowires. The synthesis methods were based on a simple one-pot tetraethylene glycol reduction process. By changing the synthesis parameters, the nanocrystal morphology can be adjusted from nanoparticles with different size to nanowires. The magnetic properties of the nanostructure and their correlation to the crystalline structures and the nanoscale morphology have been investigated theoretically and experimentally. It is revealed that the properties are related to both the crystal structures and the morphology. 相似文献
72.
73.
改进了JA-SW混合模型, 使之能处理具有两种单轴各向异性的磁体. 数值研究了面内应力对铁磁薄膜磁滞损耗和矫顽力的影响. 结果表明, 磁滞损耗和矫顽力与应力强度和应力施加方向以及外场取向有关. 磁滞损耗或矫顽力随应力强度变化的关系曲线并不完全是单调增加的, 比如当外场与易轴方向平行时会出现弯曲. 另外, 应力会造成矫顽力随外场取向角关系曲线的峰值偏移. 结果与文献资料进行了广泛对比并对其差异进行了解释.
关键词:
JA-SW混合模型
磁滞损耗
矫顽力
应力 相似文献
74.
研究了纳米Nd2Fe14B/α-Fe复合永磁材料中晶粒交换耦合相互作用对有效各向异性的影响和变化规律.结果表明:晶粒之间的交换耦合作用使材料的有效各向异性Keff随晶粒尺寸的减小而下降、随软磁性相成分的增加而降低. 当晶粒尺寸 减小到4nm时,Keff值减小为其各自通常各向异性常数值的1/3—1/4.有效各向异性的变化特点与矫顽力的变化规律基本相同.纳米复合永磁材料矫顽力的降低主要由于有效各向异性的减小而引起.
关键词:
纳米复合永磁材料
交换耦合相互作用
有效各向异性
矫顽力 相似文献
75.
本文采用统计平均方法研究了软、硬磁性晶粒尺寸及相分布对Nd2Fe14B/α-Fe纳米复合永磁材料矫顽力的影响。计算结果表明:对于单相纳米硬磁材料,磁体矫顽力随着硬磁性晶粒尺寸的减小而降低;对于软、硬两磁性相组成的Nd2Fe14B/a-Fe纳米复合永磁材料,两相的随机分布将导致磁体矫顽力随硬磁性晶粒尺寸的减小呈现极大值。本文的计算结果还表明当硬磁性晶粒尺寸大于软磁性晶粒的最佳尺寸时(15nm),具有多层膜结构的Nd2Fe14B/a-Fe纳米复合永磁材料将比两相随机分布时具有更大的矫顽力。 相似文献
76.
《Optimization》2012,61(2):199-222
Using Karlin’s [4] weak game values, a ‘weakly determined’ game is introduced. Conditions for weak determinateness of games and for strict determinateness of weakly determined games are presented. Finally, generalizations of some well-known minimax theorems are derived from these results. 相似文献
77.
以有机碱四甲基氢氧化铵(TMAH)为沉淀剂合成了纳米Fe3O4和Co2+掺杂的纳米Fe3O4粒子。分别讨论了碱用量,铁盐溶液浓度,反应温度,有机碱及PEG-4000的分散性等因素对纳米Fe3O4的形貌影响。结果表明,所合成的纳米Fe3O4为30nm左右的反尖晶石型面心立方结构,有机碱除了起沉淀剂作用,还能够提高纳米Fe3O4的分散性。本文还讨论了不同Co2+掺入量的纳米Fe3O4粒子的磁性质,结果表明Co2+掺杂的纳米Fe3O4粒子的矫顽力在不同掺入量的下有较大的改变。当Co2+掺入量为10.0%时,纳米Fe3O4的矫顽力达到最大值,为1628Oe。 相似文献
78.
Structural analysis of nickel doped cobalt ferrite nanoparticles prepared by coprecipitation route 总被引:1,自引:0,他引:1
K. Maaz S. Karim A. Mashiatullah J. Liu M.D. Hou Y.M. Sun J.L. Duan H.J. Yao D. Mo Y.F. Chen 《Physica B: Condensed Matter》2009,404(21):3947-3951
Magnetic nanoparticles of nickel substituted cobalt ferrite (NixCo1−xFe2O4:0≤x≤1) have been synthesized by co-precipitation route. Particles size as estimated by the full width half maximum (FWHM) of the strongest X-ray diffraction (XRD) peak and transmission electron microscopy (TEM) techniques was found in the range 18–28±4 nm. Energy dispersive X-ray (EDX) analysis confirms the presence of Co, Ni, Fe and oxygen as well as the desired phases in the prepared nanoparticles. The selective area electron diffraction (SAED) analysis confirms the crystalline nature of the prepared nanoparticles. Data collected from the magnetization hysteresis loops of the samples show that the prepared nanoparticles are highly magnetic at room temperature. Both coercivity and saturation magnetization of the samples were found to decrease linearly with increasing Ni-concentration in cobalt ferrite. Superparamagnetic blocking temperature as determined from the zero field cooled (ZFC) magnetization curve shows a decreasing trend with increasing Ni-concentration in cobalt ferrite nanoparticles. 相似文献
79.
Existence of solutions for a vector variational inequality: An extension of the Hartmann-Stampacchia theorem 总被引:3,自引:0,他引:3
G. Y. Chen 《Journal of Optimization Theory and Applications》1992,74(3):445-456
A vector variational inequality is studied. The paper deals with existence theorems for solutions under convexity assumptions and without convexity assumptions.This research was partially supported by the Italian Research Council (CNR), Group for Functional Analysis and Applications (GNAFA), and was carried out while the author was Visiting Professor at the Department of Mathematics, University of Pisa, September–November, 1989. 相似文献
80.
The magnetic behavior of nanocrystalline Fe73.5Nb4.5Cr5B16Cu1 alloys is investigated in a series of specimens with different volume fractions of crystalline phase. It is shown that the Curie temperature of amorphous phase firstly decreases after structural relaxation in amorphous state and then rapidly increases during the first stages of crystallization. The strikingly different behavior of coercivity at elevated temperatures is observed for the samples with low and high volume fractions of nanocrystalline particles. 相似文献