Papers by Keyword: Ni-Zn Ferrite

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Authors: Hiroki Kusunoki, Takatoshi Kondo, Kiyohiro Hiraki, Kazushi Takada, Shinzo Yoshikado
223
Authors: Qiao Ling Li, Yun Ye, Yong Fei Wang, Hong Xia Jing, Ya Kun Wang
Abstract: Ni-Zn ferrite is a kind of important magnetically soft material that has been used widely in medical signal deal and medical apparatus. So, many people are interested in both the prepare process of Zn ferrite (especially the prepare process of nanometer ferrite) and the study of its structure and properties. In this paper the condition in which Ni-Zn ferrite powders was prepared by sol-gel methods was studied. The pH value, calcined temperature, calcined time were investigated. With the designing experiment, the best condition was confirmed. The microstructures and particles size were characterized by means of TEM、IR、XRD and so on.
993
Authors: Y. Choi
Abstract: NixZn1-xFe2O4 ferrites with initial unit molar ratio of NiO/ZnO were prepared by self-propagating high temperature synthesis (SHS) at the oxygen partial pressures of 0.25 MPa. Neutron diffraction analysis shows that final product is Ni0.38Zn0.62Fe2O4 (χ2=1.68). The combustion temperature and propagating rate were about 1180 K and 4.2 mm/sec, respectively. The ferrite particle size was less than about 350 nm. The coercive force, maximum magnetization, residual magnetization, susceptibility and curie temperature of Ni0.38Zn0.62Fe2O4 powders prepared by SHS are 2878 A/m, 6.805 Wb/m2Kg, 1.27 Wb/m2Kg , 0.042 m3/kg and 42.20 °C, respectively.
371
Authors: Zhi Jian Peng, Hui Lin Ge, Dan Li, Zhi Qiang Fu, Cheng Biao Wang
Abstract: The magnetic hysteresis parameters like coercivity (Hc) and saturation magnetization (Ms), and dielectric parameters like dielectric constant (ε΄) and dielectric loss (ε΄΄/ε΄) of Ni0.5Zn0.5Fe2O4 prepared by “one-step synthesis” and conventional two-step synthesis methods, respectively, were comparatively investigated. It was observed that the saturation magnetization, dielectric constant and dielectric loss for samples prepared by “one-step synthesis” method are lower than those of ferrite samples prepared by conventional synthesis method. However, the coercivity of the former is higher due to its smaller grain size. The low dielectric loss makes these samples especially attractive for use at high frequencies.
350
Authors: Ana Cristina Figueiredo de Melo Costa, A.P.A. Diniz, Lucianna Gama, M.R. Morelli, Ruth Herta Goldsmith Aliaga Kiminami
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Authors: Kenji Sakai, Yang Guan, Yuuki Sato, Shinzo Yoshikado
Abstract: In order to design a ferrite absorber that can be used at frequencies of several GHz, the frequency dependences of the relative complex permeability μr*, the relative complex permittivity εr*, and return loss were investigated for a composite made of Ni-Zn ferrite and SiO2. When ferrite particles were dispersed and isolated in an SiO2 medium, the frequency dependence of μr* was different from that for a composite made of SiO2 particles dispersed and isolated in the ferrite medium. Moreover, when ferrite particles were isolated and a suitable mixture ratio of ferrite and SiO2 was selected, the return loss was less than −20 dB at frequencies of several GHz. The dispersion states of ferrite and SiO2 particles are thus important factors to design an absorber, and improvement in the absorption characteristics of the ferrite tile which is used as a practical absorber could be achieved using a composite made of Ni-Zn ferrite particles dispersed and isolated in an SiO2 medium.
229
Authors: Yan Min Wu, Peng Li Zhu, Rong Sun
Abstract: Magnetic composites, especially ferrite composites, are of great interest for embedded inductor applications. In this paper, the Ni-Zn ferrite particles (Ni1-xZnxFe2O4, x=0.2~0.8) with different zinc contents were synthesized via chemical coprecipitation method followed by modification with γ-glycidoxypropyl trimethoxysilane (KH-560). The particles were investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The results show that the prepared Ni1-xZnxFe2O4(x=0.2~0.7) have good spinel structures, higher saturation magnetization (35.18~77.69 emu/g) and smaller hysteresis hoops, while Ni0.2Zn0.8Fe2O4 grains exhibit some paramagnetic behaviors, such as almost zero hysteresis and non-saturated magnetization. Next Ni1-xZnxFe2O4 magnetic/epoxy composites with different volume fraction of ferrite were prepared and their magnetic performances at high frequencies were characterized by an Agilent E4991A impedance analyzer (USA). It is found that with zinc content in Ni1-xZnxFe2O4 increasing from 0.2 to 0.7, the real part of the complex permeability (μ′) of these composites increase first and then decrease with the frequency increasing gradually from 10 MHz to 1 GHz. Of all, the epoxy composites with filler of Ni0.6Zn0.4Fe2O4 or Ni0.5Zn0.5Fe2O4 ferrite show good frequency stability, and the composites including Ni0.4Zn0.6Fe2O4 ferrite have the highest permeability, and the maximal value at the frequency of 100 MHz is 5.55 when the volume faction is 42.75%. The imaginary part of the complex permeability (μ′′) of all magnetic composites is low For the Ni0.2Zn0.8Fe2O4/epoxy composites, they have very low real permeability (μ′~1) and imaginary permeability (μ″≤0.2).
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Authors: Takatoshi Kondo, Shinzo Yoshikado
141
Authors: Kenji Sakai, Kiyohiro Hiraki, Hiroki Kusunoki, Takatoshi Kondo, Shinzo Yoshikado
Abstract: It is found through simulation that composite electromagnetic wave absorbers made of Ni-Zn ferrite and SiO2 particles, which are isolated in the continuous medium of Ni-Zn ferrite, show good absorption. In particular, absorbers show absorption in the frequency regions both below and above 1 GHz for the mixing ratio of SiO2 of 80 mol%. To simulate the complex permeability of the composite materials, we considered some arrangements of SiO2 in the Ni-Zn ferrite medium. Measured values of complex permeability are close to simulated ones above 1 GHz.
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