Fabrication and magnetic property of BaSm(x)Fe(12-x)O19 (x < or = 0.4) nanofibers

BaSm(x)Fe(12-x)O19 (x < or = 0.4) ferrite nanofibers were prepared by sol-gel method from starting reagents of metal salts and citric acid. These nanofibers were characterized by TG-DTA, FTIR, SEM, XRD and VSM. These results show that the BaSm(x)Fe(12-x)O19 (x < or = 0.4) ferrite nanofibers were obtained subsequently from calcination at 750 degrees C for 1 h. The BaSm(x)Fe(12-x)O19 (x < or = 0.4) microstructure and magnetic property are mainly influenced by chemical composition and heat-treatment temperature. The grain sizes of BaSm0.3Fe11.7O19 ferrite nanofibers are in a nanoscale from 40 nm to 62 nm corresponding to the calcination temperature from 750 degrees C to 1050 derees C. The saturation magnetization of BaSm(x)Fe(12-x)O19 ferrite nanofiber calcined at 950 degrees C for 1 h initially decreases with the Sm content from 0 to 0.3 and then increases with a further Sm content, while the coercivity exhibits a continuous increase from 348 kA x m(-1) (x = 0) to 427 kA x m(-1) (x = 0.4). The differences of magnetic properties are attributed to lattice distortion and enhancement for the anisotropy energy.     

Tb0.4Dy0.6(Fe1-xMnx)1.91(x=0,0.05,0.1 0,0.15)合金的磁致伸缩性能

研究了Mn替代Fe对多晶Tb0.4Dy0.6Fe1.91合金棒材性能的影响.分析了Tb0.4Dy0.6(Fe1-xMnx)1.91(x=0,0.05,0.10,0.15)多晶棒材的结构、晶格常数、居里温度和磁致伸缩性能,发现Mn替代Fe后,样品仍然为MgCu2型Laves相结构.随着Mn含量从0增加到0.15,样品的晶格常数从7.335A增加到7.347A,居里温度从668K降低到526K.Mn原子的替代通过改变材料的交换相互作用、总磁矩和易磁化方向影响材料的磁致伸缩性能.实验结果显示,Tb0.4Dy0.6(Fe1-xMnx)1.91样品在石=0.10时综合性能最好.     

掺杂Mg对纳米CoFe2O4/SiO2复合薄膜结构和磁性的影响

采用溶胶-凝胶旋涂法制备了纳米Co_1-xMg _xFe₂O₄/SiO₂(x = 0, 0.2, 0.4, 0.6, 0.8) 复合薄膜。利用XRD、SEM、原子力显微镜、振动样品磁强计对薄膜的结构、形貌和磁性进行了分析, 研究了Mg²⁺含量对样品结构和磁性的影响。结果表明, 样品中Co_1-xMg _xFe₂O₄具有尖晶石结构, 晶粒尺寸在38~46 nm之间。随着Mg²⁺含量的增加, Co_1-xMg _xFe₂O₄的晶格常数减小, 样品的饱和磁化强度减小, 矫顽力先增大后减小。样品Co_0.4Mg_0.6Fe₂O₄/SiO₂垂直和平行膜面的矫顽力分别为350.7 kA·m^-1和279.4 kA·m^-1, 剩磁比分别为67.2%和53.9%, Co_1-xMg _xFe₂O₄/SiO₂复合薄膜具有较明显的垂直磁各向异性。     

Effect of the current annealing (without and with tensile stress) on the soft magnetic behaviour of Fe73.5-x(Co0.5Ni0.5)xSi13.5B9Nb3Cu1 alloy ribbons (x = 2.5, 5 and 10)

Experimental data on microstructural (crystalline volume fraction, grain size) and magnetic (coercive field) properties in amorphous and nanocrystalline Fe73.5-x(Co0.5Ni0.5)xSi13.5B9Nb3Cu1 alloy ribbons (x = 2.5, 5 and 10) are presented. Nanocrystalline structure was developed by annealing the precursor amorphous ribbons by current annealing (CA) and stress-current-annealing (SA). Microstructural analysis of the treated ribbons using X-ray Diffraction showed a high content of amorphous phase in the bulk. In addition, substantial changes in the crystalline state such as grain size of the samples annealed at different conditions were observed. The alloy composition also affects greatly the grain size,: increasing the (Co,Ni) content leads to higher values of the average grain size. The evolutions of the coercive field with the two kinds of thermal treatment were analysed, allowing us to conclude that the addition of (Co,Ni) tends to reduce the magnetic softness character of the original material, while the treated SA samples show higher coercivities higher than those treated without by CA.     

少量钴掺杂对Mn-Zn铁氧体结构和磁性质的影响(英文)

采用溶胶凝胶自燃烧法制备了钴掺杂的Mn-Zn铁氧体,研究了少量钴掺杂对其结构和磁性质的影响。利用X射线衍射仪对制备的粉末测试发现,Mn0.4Zn0.6-xCoxFe2O4系列铁氧体都具有纯净的尖晶石结构。晶格常数和饱和磁化强度都随着钴替代量的增加而增加。μi-T线具有两个磁导率最大的峰值并且磁导率的第二峰值随着钴的增加向低温移动。磁导率的第二峰值的温度可以通过改变钴含量来调节。基于铁氧体中磁晶各向异性补偿模型,阐明了少量钴掺杂对铁氧体磁性质影响的作用机理。     

Phase Transformation and Magnetostriction of (R-Pr)(Fe-T)_2 (R=Dy Tb; T=Co, Ni)

1. IntroductionMuch attention has been focused onmagnetostrictive materials RFe2, particularly,Tbo.zv~o.sDyo.vs~o.vFez (Terfenol-D), due to theirexcellellt magnetoelastic properties for the transducer deviceslll. Clark et al. firstly suggestedthat the pseudobinary compounds combined byTb, Dy and Fe could be constructed in an effortto reduce the anisotropy while maintaining largemagnetostrictionlZ]. Clark et al. also found in thecompensated system Tbl--.Pr.FeZ that (Tb, Pr)Fe3phase appea…     

微波多元醇法制备单分散Ni1-xZnxFe2O4/MWCNTs与磁性能

以多壁碳纳米管(MWCNTs)为模板,三乙二醇(TREG)为溶剂,采用微波多元醇法制备MWC-NTs负载组成可控的Ni1-xZnxFe2O4(x=0.4、0.5、0.6)纳米复合材料Ni1-xZnxFe2O4/MWCNTs。其结构和形貌通过XRD、SEM、TEM和EDX进行表征,用VSM测试样品的磁性,并探讨了微波功率、微波时间对镍锌铁氧体负载的影响。结果表明立方系尖晶石结构的单分散Ni1-xZnxFe2O4磁性纳米粒子均匀负载在碳纳米管表面,平均粒径约为6nm;其磁性能与镍锌铁氧体的组成有关,随着Zn含量的增加,饱和磁化强度(Ms)先增大后减小,当x=0.5时Ms达到最大值。矫顽力(Hc)都比较小,在室温下表现为超顺磁性。     

FeCoZrNbB合金的晶化过程及磁性能

采用单辊快淬法制备Fe_81-xCo_xZr₇Nb₂B₁₀(x = 2, 4, 6) 系非晶合金,并对该系非晶合金进行热处理。利用X射线衍射和振动样品磁强计研究FeCoZrNbB 合金系的晶化过程和磁性能。结果表明,Fe_81-xCo_xZr₇Nb₂B₁₀(x = 2, 4, 6) 系合金在快淬速率为30 m/s时完全形成非晶。Fe₇₉Co₂Zr₇Nb₂B₁₀合金的晶化过程为非晶→非晶+α-Fe→α-Fe + Fe₃Zr + Fe₂Nb_0.4Zr_0.6;Fe₇₇Co₄Zr₇Nb₂B₁₀与Fe₇₅Co₆Zr₇Nb₂B₁₀合金的晶化过程相同为非晶→非晶+α-Fe→ α-Fe + Fe₃Zr →α-Fe + Fe₃Zr + Fe₂Nb_0.4Zr_0.6。Co 含量的增加抑制了退火后α-Fe晶相的形核,并促使Fe 3Zr化合物更易析出。Fe_81-xCo_xZr₇Nb₂B₁₀(x = 2, 4, 6) 合金的比饱和磁化强度( M_s) 和矫顽力 ( H_c) 随退火温度的变化趋势相同。530℃ 之前退火,随退火温度的升高M s增加并不明显 ; 530℃之后退火,M_s迅速上升。530℃ 退火,H_c达到最小值;高于530℃ 退火,H_c随退火温度的升高而增加。      

Structural & Magnetic Characterizations of NiLiZn Nanoferrites Synthesized by Co-precipitation Method

Synthesis of Ni0.5LixZn(0.5-x)Fe2O4 nanoparticles with x=0, 0.1, 0.2, 0.3, 0.4 and 0.5 were realized via co-precipitation method. X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) measurements were performed on the samples to determine the characteristics of the crystal structures and the magnetic properties of the samples, respectively. The spinel phase structures of the samples were confirmed by XRD analysis. Patterns of decreased lattice parameter and increased crystallite size values were observed by increasing the Li concentration at longer synthesis reaction periods. Similarly, for the magnetic properties, both the saturation magnetization (Ms) and coercivity (Hc) were found to vary with increasing patterns at higher Li doping levels and longer synthesis reaction periods. The results and mechanisms concerned were discussed.     

Co替代对纳米晶Ni0.4CoxZn0.6-xFe2O4结构和电磁性能的影响

采用聚丙烯酰胺凝胶法制备了尖晶石型纳米晶Ni0.4CoxZn0.6-xFe2O4(x=0、0.2、0.4),同时考察了铁氧体的电磁性能.由X射线衍射(XRD)可知,随着x的增大,Ni0.4CoxZn0.6-xFe2O4的晶格常数从0.838 4 nm减小到0.835 7 nm.透射电镜(TEM)结果表明,Ni0.4Zn0.6Fe2O4铁氧体粒子的平均直径约为20 nm.Ni0.4CoxZn0.6-xFe2O4在8.2～12.4 GHz的测试频率范围内具有介电损耗和磁损耗.在频率为9.0 GHz时,Ni0.4CoxZn0.6-xFe2O4(x=0.4)复介电常数虚部的最大值达到19.6.随着X值的增加,复数磁导率虚部的共振吸收峰向高频移动.制备的复合物可以被广泛地用于抑制电磁辐射和吸收雷达波等领域.     

Characterization of ThMn_(12)-structure Stability

A series of YTi(Fe_(1-x)_(11)alloy withx=0.00,0.01,0.03,0.04,0.05,0.07 and 0.10 hasbeen investigated by measurement of the structuralproperties and ~(57)Fe Mssbauer experiments.Thepure ThMn_(12)-structure phase exists at x≤0.03 andis absent at x>0.03.The reasons for lower satura-tion magnetization and lower energy product of theThMn_(12)-structure compounds were given.Thecrystal structure relations     

Gas sensing property of perovskite SrTi(1-x)Fe(x)O3_delta fabricated by thick film planar technology

Planar sensor of SrTi(1-x)Fe(x)O3-delta, x = 0.4 and 0.6, with perovskite structure was fabricated on alumina substrate using thick film technology. Electrical resistance was measured as a function of thermal treatment conditions, atmosphere, time and temperature. Sensing property was also measured as a function of temperature and the gases of O2, CH4, CO, CO2, NO and NO2. The resistance of SrTi(1-x)Fe(x)O3-delta is lower than those of SrTiO3 or SrFeO3. TCR (temperature coefficient of resistance) of zero over 550 degrees C was measured for the composition of SrTi(1-x)Fe(x)O3-delta after thermal treatment at 1100 degrees C in air atmosphere only. The perovskite SrTi(1-x)Fe(x)O3-delta didn't show any response to CH4, CO, CO2, NO and NO2, but an excellent response and recovery characteristics with oxygen concentration.     

The dielectric properties of Ba(0.6)Sr(0.4)Cr(x)Ti(1-x)O(3) thin films prepared by pulsed laser deposition.

Ba(0.6)Sr(0.4)Cr(x)Ti(1-x)O(3) (BSCT) films were prepared by pulsed laser deposition with the value of x varying from 0 mol% to 2.0 mol%. X-ray diffraction analysis detected an increase in the lattice parameters, which could be due to the characteristics of the growth process. Dielectric properties and tunability of the BSCT films were measured. The dissipation factors of the films decreased with increasing Cr-concentration. The highest figure of merit (FOM) value of 33.3 was obtained in 1.0 mol%-doped BSCT film. As a result, the effect of Cr doping is positive.     

Synthesis of ferrites obtained from heavy metal solutions using wet method

Wet method was employed to the treatment of heavy metal-contaminated wastewater, and Zn(x)Fe(3-x)O(4), Ni(x)Fe(3-x)O(4) and Cr(x)Fe(3-x)O(4) (0Cr(3+) and the influence of the three ions on sample thermostability is Zn(2+)>Ni(2+)>Cr(3+).     

Synthesis,characterization and electrochemical performance of $$\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}$$ cathode materials for lithium ion batteries

\(\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}\) (\(x = 0\), 0.2, 0.4, 0.6, 0.8 and 1) samples were prepared by a sol–gel process. The crystal structure of prepared samples of \(\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}\) was characterized using an X-ray diffractometer. Different crystallographic parameters such as crystallite size and lattice cell parameters have been calculated. Scanning electron microscopy and Fourier transform infrared spectroscopy investigations were carried out, which reveal the morphology and function groups of the synthesized samples. Furthermore, electrochemical impedance spectra measurements are performed. The obtained results indicated that the highest conductivity is achieved for the \(\hbox {Li}_{2}\hbox {Ni}_{0.4}\hbox {Fe}_{0.6}\hbox {SiO}_{4}\) electrode compound. It was observed that Li–\(\hbox {Li}_{2}\hbox {Ni}_{0.4}\hbox {Fe}_{0.6}\hbox {SiO}_{4}\) battery has initial discharge capacity of 164 mAh \(\hbox {g}^{-1}\) at 0.1C rate. The cycle life performance of all \(\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}\) batteries ranged between 100 and 156 mAh \(\hbox {g}^{-1}\) with coulombic efficiency range between 70.9 and 93.9%.     

Spin polarization measurement of homogeneously doped Fe(1-x)Co(x)Si nanowires by Andreev reflection spectroscopy

We report a general method for determining the spin polarization from nanowire materials using Andreev reflection spectroscopy implemented with a Nb superconducting contact and common electron-beam lithography device fabrication techniques. This method was applied to magnetic semiconducting Fe(1-x)Co(x)Si alloy nanowires with x? = 0.23, and the average spin polarization extracted from 6 nanowire devices is 28 ± 7% with a highest observed value of 35%. Local-electrode atom probe tomography (APT) confirms the homogeneous distribution of Co atoms in the FeSi host lattice, and X-ray magnetic circular dichroism (XMCD) establishes that the elemental origin of magnetism in this strongly correlated electron system is due to Co atoms.     

Synthesis and self-assembly of ultrathin Ni(x)Fe(1-x)(OH)2 nanodiscs via a wet-chemistry method

Self-assembled ultrathin Ni(x)Fe(1-x)(OH)2 nanodiscs have been synthesized by using a wet-chemistry method. The uniformity and the assembly of Ni(x)Fe(1-x)(OH)2 nanostructures are sensitive to the iron ion concentration in the precursor. An optimum iron concentration of 10% results in the formation of uniform ultrathin Ni(x)Fe(1-x)(OH)2 nanodiscs with a typical side length of 50 nm and a thickness of 10 nm. They are also self-assembled by connecting their (001) facets with in-plane orientation and form a chain-like microstructure. Lattice relaxation is present within several atomic layers at the interfaces between two adjacent nanodiscs, which introduces about 6 degrees misalignment of these nanocrystals. Analytical electron microscopy analysis reveals that the iron additive atoms distribute uniformly in the nanodiscs and they are substitution atoms of Ni atoms. It has been found that the iron species is critical to the formation and assembly of the hexagonal nanodiscs.     

Structural and Magnetic Properties of Sm$_3$(Fe$_1-rm x$Co$_rm x$)$_27.7$Ti$_1.3$

The structure and magnetic properties of Sm₃(Fe_1-x Co_x)_27.7Ti_1.3 compounds, with x ranging from 0 to 0.4, have been investigated by means of X-ray powder diffraction and magnetic measurements. The main phase formed was that of Nd₃(Fe, Ti)₂₉-type structure (3:29) with a relatively small amount of the ThMn₁₂-type structure (1:12) as a secondary phase (7-13 wt.%). The lattice parameters and the unit-cell volume decrease with increasing Co content x. It is found that substitution of Co for Fe leads to a significant increase in the Curie temperature from 488 K for x=0 to 941 K for x=0.4. Saturation magnetization gradually increases with increasing Co. All compounds show easy cone-type anisotropy     

Influence of Zn^2＋ or Cu^2＋ on Reduction and Recalcination Behavior of Fe2TiO5

Fe2O3, TiO2, CuO and ZnO powders were mixed according to the formula of （1-x）TiO2 xCuO-Fe2O3 or （1-x）TiO2 xZnO-Fe2O3 （x=0, 0.2 0.4, 0.6, 0.8, 1）, and well ball-milled with H2O for 3 h to ensure homogeneity of the powdered solids, then fired at 1200℃ for 4 h. The fired samples were reduced at 500℃ with hydrogen gas. The reduced samples were subjected to recalcination at 500℃ in CO2 atmosphere. Both of fired, reduced and calcined samples were characterized by X-ray diffraction, vibrating sample magnetometry, reflected light microscopy and scanning electron microscopy. Different phases were formed after firing of Cu^＋2 or Zn^2＋ substituted Fe2TiO5. Magnetization （Bs） of the formed phases after firing are very low corresponding to diluted magnetic semiconductors （DMS） and increases with increasing the substituted cations （Cu^＋2 or Zn^2＋）. The reduction of the fired samples enhanced the Bs values whereas the reducibility increases with increasing the Cu^＋2 or Zn^2＋ content. Samples show different tendency toward CO2 decomposition which is very important for environmental minimization for CO2.     

Terahertz dielectric response of ferroelectric Ba(x)Sr(1-x)TiO3 thin films

Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.