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81.
《Arabian Journal of Chemistry》2020,13(11):8100-8118
The synthesis of the Ni0.5-xZn0.5-xCu2xFe2O4 (x = 0; 0.10 and 0.15) ferrite with the differential of pilot-scale production by the combustion reaction method was investigated for RAM application purposes. Combustion temperatures ranging from 682 °C to 738 °C were observed. All ferrites were sintered at 1200 °C for 1 h. A comprehensive study of the influence of substitution with Cu2+ in a partial and proportional way to the Ni2+ and Zn2+ ions, doping mode little reported in the literature, and also of the sintering process over the structural, textural, morphological, magnetic and electromagnetic properties of NiZnCu ferrites was performed. The XRD patterns of the ferrites as synthesized revealed the formation of the cubic structure of the inverse spinel as majoritary phase, and traces of hematite and zinc oxide as segregated phases. After sintering, it was proven the single-phase formation of cubic spinel ferrite structure. The introduction of Cu led to a reduction in the lattice parameter, whose values ranged from 8.337 to 8.385 Å. The EDX results confirm the composition of oxides. The textural and morphological analyses confirmed the densest characteristic, with increase of particle size and reducing of surface area and pore volume after Cu-doping. All ferrites showed characteristics of soft ferrimagnetic material, where the increase in Cu content contributed to a slight reduction in saturation magnetization, whose values were of ~22–29 emu/g for the as synthesized ferrites and ~71–85 emu/g for the sintered ones. The best result of electromagnetic absorption in X-band was presented by the sintered ferrite with 0.3 mol of Cu, reaching an attenuation of 99.8% at 11.5 GHz frequency, thus confirming the efficiency of the pilot-scale combustion synthesis in obtaining a ferrite with great potential for RAM application. 相似文献
82.
83.
G. N. Pirogova N. M. Panich R. L. Korosteleva Yu. V. Voronin G. E. Kalinina 《Russian Chemical Bulletin》1996,45(1):42-44
Catalytic activities of ferrites MFe2O4 (M = Cu, Co, Ni, Mg, and Zn) and M1
0.5M2
0 .5Fe2O4 (M1 = CU; M2 = Co, Zn, and Mg) in oxidation of CO and ethylbenzene were investigated, and their dependences on the cation nature were established. Higher activities were observed for catalysts containing ions with variable valence (Cu, Co, and Ni). A correlation between catalytic and adsorption properties of ferrites was found.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 49–52, January, 1996. 相似文献
84.
85.
Aligned and random fibres of strontium hexaferrite (SrM, SrFe12O19) and barium hexaferrite (BaM, BaFe12O19) were manufactured by blow spinning from an aqueous inorganic sol–gel precursor, which was then fired to give the hexagonal ferrite fibre. Their magnetic properties were studied by VSM, investigating the evolution of these properties with firing and measurement temperature, and in particular the effects of fibre alignment. It has been predicted that aligned ferrite fibres will demonstrate an enhanced magnetisation along the axis of alignment with respect to perpendicular to the axis, and this has been demonstrated here for the first time. The optimum firing temperature was 1000 °C, at which point they still had submicron grains. In BaM random fibres Ms=63.8 emu g−1 and Hc=428.1 kA m−1, and in SrM random fibres Ms=63.3 emu g−1 and Hc=452.8 kA m−1, high values for polycrystalline materials. Fibres aligned parallel to the applied field had saturation magnetisation (Ms) values equal to those of the random fibres, whilst fibres aligned perpendicular to the field had Ms values 62% and 75% lower, for BaM and SrM, respectively. There was no change in coercivity (Hc) between random or aligned fibres of any orientation, and fibres aligned 45° and parallel to H appeared identical. Therefore, properties along the axis of alignment were superior when compared to measurements perpendicular to the axis of alignment, giving a directionality to the magnetisation in an otherwise randomly oriented ferrite material. 相似文献
86.
Manuel Angst 《固体物理学:研究快报》2013,7(6):383-400
The possibility of multiferroicity arising from charge ordering in LuFe2O4 and structurally related rare earth ferrites is reviewed. Recent experimental work on macroscopic indications of ferroelectricity and microscopic determination of coupled spin and charge order indicates that this scenario does not hold. Understanding the origin of the experimentally observed charge and spin order will require further theoretical work. Other aspects of recent research in these materials, such as geometrical frustration effects, possible electric‐field‐induced transitions, or orbital order are also briefly treated.
87.
The hyperfine magnetic field at 111Cd impurities substituting iron in the mixed spinels Cd
x
Fe3−x
O4 and Zn
x
Fe3−x
O4 has been determined by means of the Perturbed Angular Correlation technique. Compounds with different concentrations x were investigated as a function of temperature. The possibility of determining the lattice location of probes at octahedral
or tetrahedral sites through the magnitude of the electric field gradient is analyzed. The measured hyperfine magnetic field
at impurities in tetrahedral sites is discussed in terms of the populations of magnetic ions in the nearest neighbor sites.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
88.
A series of Mn1−xCuxFe2O4, with x=0, 0.25, 0.50, 0.75 and 1.0, spinel ferrites were prepared by standard ceramic method, to study the effect of compositional variation on magnetic susceptibility, saturation magnetization (Ms), Curie temperature (Tc) and magnetic moments (μB). The Curie temperatures have been evaluated by measuring the ac susceptibility using the mutual inductance technique. On increasing Cu contents from 0.0 to 0.50, the saturation magnetization increases while the Curie temperature decreases. On further increase in Cu contents, x>0.50 a decreasing trend in Ms is exhibited while Tc continues to decrease. This effect can be partially related to the low magnetic moments of Cu+2 ions. The dominant interaction in all ferrite samples is A-B interaction which is due to the negative values of the characteristic temperature θ(K) showing that the magnetic ordering is antiferromagnetic. The Y-K angle increases gradually with increasing copper contents and extrapolates to 90° for CuFe2O4. From the computation of Y-K angles for Mn1−xCuxFe2O4, it can be concluded that the mixed copper ferrites exhibit a non-collinearity of the Y-K type while MnFe2O4 shows a Neel type of ordering. 相似文献
89.
研究了电感耦合等离子体质谱(ICP-MS)法测定锰锌铁氧体中硅和磷元素的分析方法。样品用硝酸+盐酸经微波溶解,用超纯水稀释后直接进入ICP-MS法进行测定。通过向八极杆碰撞/反应池(ORS)中引入氦气,消除高盐基体带来的多原子离子质谱干扰,采用Y为内标元素校正基体效应所产生的影响,优化了仪器的最佳工作参数。采用NIST SRM 362和NIST SRM 364验证了方法的准确性,测定结果与标准物质所提供的参考值一致。硅和磷元素的检出限分别为0.91和0.27μg·L-1。 相似文献
90.