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包钴型γ-Fe2O3磁粉的矫顽力可比原γ-Fe2O3磁粉提高8000—32000A/m。木文研究探讨了两种包钴型γ-Fe2O3磁粉(包钴γ-Fe2O3和包钴包亚铁γ-Fe2O3)的单轴各向异性的起源和矫顽力增大的机制。包钴γ-Fe2O3磁粉矫顽力
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包钴型γ-Fe_2O_3磁粉分为包钴γ-Fe_2O_3(简记为Co-γ-Fe_2O_3)和包钴包亚铁γ-Fe_2O_3(简记为 CoFe-γ-Fe_2O_3)两种,它们的矫顽力可比γ-Fe_2O_3磁粉的提高100至400Oe左右,本工作对这两种磁粉矫顽力增大的原因作了探讨,认为它们矫顽力增大的机制不同:CO-γ-Fe_2O_3矫顽力增大是由于表面包覆一层Co(OH)_2使表面各向异性增大,而CoFe-γ-Fe_2O_3则是由于表面包覆的是钴铁氧体,γ-Fe_2O_3与钴铁氧体之间发生耦合作用,使矫顽力增大。 相似文献
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包钴铁氧体型,γ-Fe2O3磁粉(简记为CoFe-γ-Fe2O3)是针状γ-Fe2O3磁粉与Co++和Fe++溶液起反应,在每个针状颗粒上包覆了一层钴铁氧体固溶体。经此种方法处理后的γ-Fe2O3磁粉的矫顽力及其它磁特性有较大的提高。如矫顽力由原来415Oe增加到715Oe;剩磁和矫顽力随时间及温度变化小等。我们利用穆斯堡尔效应并配合其它研究手段进行了研究,认为:CoFe-γ-Fe2O3磁粉矫顽力的提高,主要是由于γ-Fe2O3磁粉表面包覆了一层钴铁氧体固溶体,γ-Fe2O3与钴铁氧体固溶体之间发生磁耦合作用之故。
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本文采用液相沉积法制备出了纳米SiO2/γ-Fe2O3复合粒子,在其表面负载ZnO, 从而得到了易于磁性固液分离的磁载光催化剂ZnO/SiO2/γ-Fe2O3, 并通过XRD和TEM等测试技术对样品进行了表征。以可溶性染料亚甲基兰等为降解对象, 研究了磁载光催化剂ZnO/SiO2/γ-Fe2O3在紫外光下的光催化活性。结果表明, 在γ-Fe2O3和ZnO之间包覆一层无定形SiO2可使催化剂降佳率由20.76%提高到95.63%,并且该磁载光催化剂对染料有较好的降解效果, 在三次循环使用后仍能保持较好的光催化性能. 相似文献
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Yosun HwangS. Angappane Jongnam ParkKwangjin An T. HyeonJe-Geun Park 《Current Applied Physics》2012,12(3):808-811
We have carried out systematic studies on well-characterized monodisperse Fe3O4/γ-Fe2O3 core/shell nanoparticles of 2-30 nm having a very narrow size distribution and possessing a uniquely mono-layer of surface γ-Fe2O3. This unique core-shell structure, probably having a disordered magnetic surface state, leads us to three key observations of unusual magnetic properties: i) a very large magnetic exchange anisotropy reaching over 7 × 106 erg/cm3 for the smaller particles, ii) exchange bias behavior in the magnetization data of the core/shell Fe3O4/γ-Fe2O3 nanoparticles, and iii) the temperature dependence of the coercive field following an unusual exponential behavior. 相似文献
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Hongyang Zhu Yanzhang Ma Haibin Yang Dongbin Hou 《Journal of Physics and Chemistry of Solids》2010,71(8):1183-9232
Phase transition and bulk moduli of bulk and nanocrystalline γ-Fe2O3 were studied using synchrotron X-ray diffraction under high pressure. Contrary to most other nanomaterials, nanocrystalline γ-Fe2O3 begins to transform into α-Fe2O3 at the same pressure as bulk γ-Fe2O3, which is caused by a special structure of γ-Fe2O3, in which there exist vacancies of crystal. It is believed that phase transition starts from a certain site of vacancy because of the stress concentration at vacancy sites. Compared to bulk material, nanocrystalline γ-Fe2O3 has a larger bulk modulus, which is ascribed to the large ratio of surface to volume. 相似文献
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Zhongzhu Wang Hong Bi Jian Liu Tao Sun Xianliang Wu 《Journal of magnetism and magnetic materials》2008
The conducting protonated polyaniline (ES)/γ-Fe2O3 nanocomposite with the different γ-Fe2O3 content were synthesized by in-situ polymerization. Its morphology, microstructure, DC conductivity and magnetic properties of samples were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), four-wire-technique, and vibrating sample magnetometer (VSM), respectively. The microwave absorbing properties of the nanocomposite powders dispersing in wax coating with the coating thickness of 2 mm were investigated using a vector network analyzers in the frequency range of 7–18 GHz. The pure ES has shown the absorption band with a maximum absorption at approximately 16 GHz and a width (defined as frequency difference between points where the absorption is more than 8 dB) of 3.24 GHz, when 10% γ-Fe2O3 by weight is incorporated , the width is broadened to 4.13 GHz and some other absorption bands appear in the range of 7–13 GHz. The parameter dielectric loss tan δe (=ε″/ε′) in the 7–18 GHz is found to decrease with increasing γ-Fe2O3 contents with 10%, 20%, 30%, respectively, but magnetic loss tan δm (=μ″/μ′) increases with increasing γ-Fe2O3 contents. The results show that moderate content of γ-Fe2O3 nanoparticles embedded in protonated polyaniline matrix may create advanced microwave absorption properties due to simultaneous adjusting of dielectric loss and magnetic loss. 相似文献
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采用solgel方法制备M型六角锶铁氧体.利用X射线衍射,透射电子显微镜和VSM对纳米晶样品进行了研究.当焙烧温度小于或等于800℃,样品存在复相.在同样条件下,压成薄片的样品呈现了硬磁与软磁SrFe12O19γFe2O3的纳米复合相的磁性交换耦合作用.800℃焙烧的薄片样品的比饱和磁化强度σS为75.6A·m2kg,内禀矫顽力HcJ为478.9kAm,最大磁能积(BH)max为14.9kJm3,而粉末样品相应的分别为75.9A·m2kg,509.6kAm和12.1kJm3.当焙烧温度大于850℃时,只有
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六角锶铁氧体
纳米复合
交换耦合
磁性 相似文献
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Qian Gao Fenghua Chen Jilin Zhang Jiazuan Ni 《Journal of magnetism and magnetic materials》2009,321(8):1052-1057
The surface structure of the iron oxide nanoparticles obtained by the co-precipitation method has been investigated, and a thin layer of α-FeOOH absorbed on surface of the nanoparticle is confirmed by analyses of Fourier transform infrared (FTIR), X-ray photoelectron spectra (XPS) and surface photovoltage spectroscopy (SPS). After annealed at 400 °C, the α-FeOOH can be converted to γ-Fe2O3. The simple-annealed procedure resulted in the formation of Fe3O4@γ-Fe2O3 core/shell structure with improved stability and a higher magnetic saturation value, and also the simple method can be used to obtain core/shell structure in other similar system. 相似文献
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S. Masoud Hosseini E. Ghasemi H. Ahmadi Moghaddam 《Journal of magnetism and magnetic materials》2010,322(23):3792-3796
A stable γ-Fe2O3 paraffin-based ferrofluid was prepared via high energy milling. The magnetic particles were characterized using X-ray diffraction, dynamic light scattering and vibrating sample magnetometer techniques. The rheological properties of the ferrofluid were studied using a standard rotating rheometer. The magnetoviscous effect and thixotropy in the ferrofluid were studied. The formation and destruction of magnetically induced structures and the interactions of nanoparticles and aggregates are discussed. 相似文献
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γ-Fe2O3 has a spinel structure with cation vacancy and is expected to perform as a favorable electrode material for secondary lithium-ion battery. When lithium is inserted electrochemically into γ-Fe2O3, prolonged potential change is observed after the insertion. In this study, we inserted various amount of Li into γ-Fe2O3 (x = 0.66, 1.1, 1.5 in terms of LiXFe2O3), then made the circuit open, measured X-ray diffraction (XRD) patterns at various elapsed time, and analyzed the crystal structure change of γ-Fe2O3 with time by the Rietveld method. The X-ray Rietveld analysis revealed that the iron occupancy of 8a site decreased and that of 16c site increased with lithium insertion process and after lithium insertion, the iron occupancy of 8a site increased and that of 16c site decreased gradually with relaxation time. It is indicated that lithium prefer 8a site to occupy kinetically, on the other hand, prefer 16c site thermodynamically. 相似文献