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101.
As the heterogeneous Fenton-like catalyst, a series of spinel ferrites magnetic nanoparticles NiFe2O4 and NiFe2O4@SiO2 catalysts were synthesized and were applied into the oxidation of rhodamine B, which exhibited the good catalytic performance and strong magnetic separation after reaction. 相似文献
102.
Polycrystalline Mg1−xZnxFe2O4 (x=0.0–0.6) ferrites have been prepared using solid-state reaction technique. The X-ray diffraction analysis revealed that the samples crystallize in a single-phase cubic spinel structure. The lattice parameter increases linearly with increase in zinc content obeying Vegard's law. The continuous decrease in Curie temperature (Tc) with an increase in Zn content is attributed to the weakening of A–B exchange interaction. Saturation magnetization (Ms) and magnetic moment are observed to increase up to x=0.4, and thereafter decrease due to the spin canting in B-sites. The initial permeability is found to increase with the addition of Zn2+ ions but the resonance frequency shifts towards the lower frequency. 相似文献
103.
Jumiah Hassan Farm Mooi Yen Mansor Hashim Zulkifly Abbas Zaidan Abdul Wahab W. Mohd. Daud W. Yusoff Azmi Zakaria 《Ionics》2007,13(4):219-222
NiFe2O4 prepared via the sol–gel technique were pre-sintered at 900 °C and synthesized at different sintering temperatures from 1,000 °C
to 1,200 °C at 100 °C intervals. The samples were characterized for microwave dielectric properties. These samples were measured
using Agilent Impedance/Material Analyzer at frequencies 1 MHz to 1.8 GHz. Results showed a decrease in the dielectric constant
and loss factor with frequency except at the turning point, around 150 MHz, where the loss factor showed a gradual increase.
However, both the dielectric constant and loss factor increase with increasing sintering temperature. The grain size and density
also increased with increasing sintering temperature, but the porosity and grain boundary density showed a decrease.
This paper was presented at the International Conference on Solid State Science and Technology 2006, Kuala Terengganu, Malaysia,
Sept. 4–6, 2006. 相似文献
104.
采用溶胶 凝胶自燃烧法制备了纳米尺度的锌钴铁氧体Zn06CoxFe24- xO4(x=0—030)粉体,分别在不同温度下进行了热处理,利用x射线衍射仪(XRD) 和振动样品磁强计(VSM)对其物 相结构和磁性进行了测量和分析.实验结果表明,锌钴铁氧体Zn06Co015Fe 225O4在550—800℃温度区间出现α Fe2O3过渡相,在高于800℃温度时生 成 单一尖晶石相锌钴铁氧体;随钴含量的增加,Zn06CoxFe2
关键词:
锌钴铁氧体
磁性
结构
相变
溶胶 凝胶 相似文献
105.
《Current Applied Physics》2020,20(9):1019-1025
(Li1+, Al3+) co-doped Ni0.5Zn0.5Fe2O4 ferrites, Ni0.5-xZn0.5-xLixAlxFe2O4 (x = 0.000, 0.025, 0.050 and 0.100), were synthesized by the sol-gel auto-combustion method. X-ray diffraction (XRD), field emission scanning electronic microscope (FESEM), vibrating sample magnetometer (VSM) and LCR meter were used to investigate the structural, magnetic and dielectric properties. Results of XRD and SEM indicate that both doping amount and calcination temperature play significant roles in crystal structure and grain growth. Also, it can be observed that the saturation magnetization and the coercivity change in a noticeable manner. The Ni0.475Zn0.475Li0.025Al0.025Fe2O4 ferrite sintered at 1200 °C has a relatively low coercivity value (62.93 Oe) and the largest saturation magnetization (110.95 emu/g). Besides, dielectric behavior is also improved by Li1+ and Al3+ co-doping. 相似文献
106.
Subhash Chander Sudhish Kumar Anjali Krishnamurthy Bipin K. Srivastava V. K. Aswal 《Pramana》2003,61(3):617-624
DC magnetization measurements are reported in the temperature range 20–100 K on a poly-disperse nano-particle sample of the spinel ferrite Fe2.9Zn0.1O4 with a log-normal size distribution of median diameter 43.6 Å and standard deviation 0.58. Outside a core of ordered spins, moments in surface layer are disordered. Results also show some similarities with conventional spin glasses. Blocking temperature exhibits a near linear variation with two-third power of the applied magnetic field and magnetizationM evolves nearly linearly with logarithm of timet. Magnetic anisotropy has been estimated by analysing theM-logt curve. Anisotropy values show a large increase over that of bulk particle samples. Major contribution to this enhancement comes from the disordered surface spins. 相似文献
107.
Hong-guo ZhangYu-Jie Zhang Weng-Hong Wang Guang-Heng Wu 《Journal of magnetism and magnetic materials》2011,323(15):1980-1984
A series of Co ferrites (CoxFe3−xO4 (x=0−1)) were prepared using solid-state method in this work. The aging effect of their structures and constrictions of hysteresis loops under low magnetic field were investigated. It was found that during the aging process, the migration of trivalent (bivalent) ions between tetrahedral (A-site) and octahedral (B-site) coordination induced a shrinking of the lattice, which would expand again due to the precipitation of Fe3+ after a much longer aging time. The first process caused a pronounced constriction of the loops, due to the uniaxial anisotropy led by this migration. The depression of constriction could attribute to both the expansion of lattice and the change of ionic ratios as a result of the second-phase-precipitation. The impacts of Co content, aging time and temperature upon the constriction were also discussed. 相似文献
108.
CuFe2O4 particles were successfully engineered by a facile sol-gel method. The synthesized products were characterized physically by X-ray diffraction (XRD), scanning electron microscopy (SEM). Besides, the effects of the sintering temperature and the molar ration of citric acid/the total metal cations (CA/MC) on their infrared radiant properties were investigated at the wavelength of 3–5 μm. The highest infrared emission value ca. 0.911 was obtained when the test temperature was conducted at 800 °C, indicating its potential application in infrared heating, infrared coating and drying fields. 相似文献
109.
M. Elzain H. Widatallah A. Gismelseed K. Bouziane A. Yousif A. Al Rawas I. Al-Omari A. Sellai 《Hyperfine Interactions》2006,168(1-3):1151-1157
The ferrites Mg0.9Mn0.1Cr x Fe2?x O4 ( The ferrites Mg0.9Mn0.1Cr
x
Fe2−x
O4 () were prepared using the conventional double sintering method. The XRD showed that the samples maintain a single spinel cubic
phase. The M?ssbauer measurements were carried out at room and liquid nitrogen temperatures. From the area ratios of the A
and B sites, it was found that the Fe cation population of the A and B sites decreases in proportion to Cr concentration.
The contact hyperfine fields at the A and B sites were found to decrease with increasing Cr contents. This was found to be
in approximate agreement with the results of magnetization measurement. The distributions of Mg and Mn cations versus Cr concentration
were also determined using the M?ssbauer and magnetization results. The Curie temperatures were determined and found to agree
with the reported values. As the Cr contents increases the relative magnetization, was found to increase at low temperatures
and decreases at higher temperatures. 相似文献
110.
The Raman spectra of Li0.5Co0.1Fe2.4O4 nanoparticles have been recorded in the spectral range, 400-800 cm−1 at four different particle sizes. X-ray and TEM measurements were done to determine crystal structure and size of the nanoparticles. X-ray diffraction (XRD) shows that the Li0.5Co0.1Fe2.4O4 nanoparticles have an order phase spinel structure without any impurity. The size of the nanocrystal was calculated through XRD patterns and TEM micrographs and it turns out to be 34-42 nm. The Raman spectra of each size nanoparticles show five Raman bands. The most intense Raman band shows a noticeable asymmetrical feature towards lower wavenumber side. A line shape analysis was performed to get the exact spectral parameters of the Raman bands. The intensity of asymmetrical feature keeps on increasing with decreasing the particle size from 42 nm to 34 nm and finally evolved as a new Raman band. The appearance of new band and its intensity response relative to the intensity of the main Raman band as a function of particle size has been explained in terms of electron-phonon coupling. It was observed that the strength of electron-phonon coupling goes on increasing with reducing the particle size. The red shifting of the Raman bands upon reducing the crystalline size is explained in terms of the lattice expansion, which is well supported by the XRD data. 相似文献