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1.
Complex permittivity, complex permeability and microwave absorption properties of ferrite-paraffin polymer composites 总被引:1,自引:0,他引:1
Harun Bayrakdar 《Journal of magnetism and magnetic materials》2011,323(14):1882-1885
We have investigated the electromagnetic (EM) characteristics of CoxMn1−xFe2O4 spinel ferrite (where x=0.0, 0.5 and 1.0) nanoparticles (NPs)/paraffin nanocomposite material at 8-20 GHz. CoxMn1−xFe2O4 NPs have been synthesized by cetyltrimethylammonium assisted hydrothermal route using NaOH. A variation in complex dielectric permittivity and magnetic permeability at room temperature with frequency in the range 8-20 GHz has been studied. Particles showed phase purity and crystallinity in powder X-ray diffraction (XRD) analysis. At the same time, CoxMn1−xFe2O4 NPs demonstrated a spinel cubic structure from XRD results. A reflection loss of −46.60 dB was found at 10.5 GHz for an absorber thickness of 2 mm. CoxMn1−xFe2O4 may be attractive candidates for EM wave absorption materials. 相似文献
2.
E. Veena Gopalan K.A. Malini D. Sakthi Kumar M.R. Anantharaman 《Journal of magnetism and magnetic materials》2009,321(8):1092-1099
Mn1−xZnxFe2O4 nanoparticles (x=0-1) were synthesized by wet chemical co-precipitation techniques. X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy were effectively utilized to investigate the different structural parameters. The elemental analysis was conducted using energy-dispersive spectrum and inductively coupled plasma analysis. The magnetic properties such as magnetization and coercivity were measured using vibrating sample magnetometer. The observed magnetization values of the nanoparticles were found to be lower compared to the bulk counterpart. The magnetization showed a gradual decrease with zinc substitution except for a small increase from x=0.2 to 0.3. The Curie temperature was found to be enhanced in the case of ferrites in the nanoregime. The variation in lattice constant, reduced magnetization values, variation of magnetization with zinc substitution, the presence of a net magnetic moment for the zinc ferrite and the enhancement in Curie temperature in Mn1−xZnxFe2O4 all provide evidence to the existence of a metastable cation distribution together with possible surface effects at the nanoregime. 相似文献
3.
S.F. Mansour 《Journal of magnetism and magnetic materials》2011,323(13):1735-1740
Manganese-magnesium ferrite nanoparticles Mn1−xMgxFe2O4; 0≤x≤0.25 were prepared by the co-precipitation route. The samples were characterized by X-ray diffraction (XRD), which confirms the single phase spinel structure. Crystallite size, calculated from the (3 1 1) peak using the Scherrer formula, was found to increase with increasing Mg2+ concentrations and was found to be within the range 3-6 nm. TEM was also used to characterize the microstructure of nanosized Mn1−xMgxFe2O4. Nominal composition of the samples was determined by Atomic Absorption analysis (AA). Hysteresis loops of manganese-magnesium ferrite were obtained at room temperature and revealed lower saturation magnetization values associated with nanocrystalline Mn1−xMgxFe2O4 particles. This behavior was attributed to structural distortion of surface spins compared to that of the bulk one. 相似文献
4.
Gh.R. Amiri M.H. YousefiS. Manouchehri M.H. KeshavarzS. Fatahian 《Journal of magnetism and magnetic materials》2011,323(6):730-734
In this work, Mn0.7Zn0.3Fe2O4 and Ni0.7Zn0.3Fe2O4 nanoparticles with super-paramagnetic properties and size distribution from 10 to 52 nm were investigated. These particles were produced by a low-temperature solid-state reaction method without the ball-milling process. The size and morphology of the nanocrystallites were determined by X-ray diffraction, transmission electron microscopy and scanning tunneling microscopy methods. Magnetic measurements such as alternating gradient field magnetometers were used to justify the super-paramagnetic properties of these nanoparticles. Their microwave absorption in the range of 8-18 GHz was studied by a vector network analyzer. Responses of the device under tests were studied. Also, the percentage of the resin, the size and thickness of the mount were determined. The band width of 2.3 GHz was obtained with reflection-loss/written-loss of −16 dB around 10.4 GHz. 相似文献
5.
Li0.5Fe2.5−xMnxO4 (0≦x≦1.0) powders with small and uniformly sized particles were successfully synthesized by microwave-induced combustion, using lithium nitrate, ferric nitrate, manganese nitrate and carbohydrazide as the starting materials. The process takes only a few minutes to obtain as-received Mn-substituted lithium ferrite powders. The resultant powders annealed at 650 °C for 2 h and were investigated by thermogravimeter/differential thermal analyzer (TG/DTA), X-ray diffractometer (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and thermomagnetic analysis (TMA). The results revealed that the Mn content were strongly influenced the magnetic properties and Curie temperature of Mn-substituted lithium ferrite powder. As for sintered Li0.5Fe2.5−xMnxO4 specimens, substituting an appropriate amount of Mn for Fe in the Li0.5Fe2.5−xMnxO4 specimens markedly improved the complex permeability and loss tangent. 相似文献
6.
Alka V. Deshmukh S.M. Yusuf N.P. Lalla 《Journal of magnetism and magnetic materials》2010,322(5):536-1217
Present study reports the detailed structural and magnetic, as well as chemical analysis of polycrystalline Zn1−xMnxO (where x=0, 0.005, 0.01, 0.03, 0.05 and 0.1) samples synthesized by the high-temperature solid state reaction route. X-ray diffraction studies reveal the presence of secondary phase for higher Mn-doping concentrations (x≥0.03). Secondary phase formation having spinel structure is confirmed and reported as an evidence for the first time using transmission electron microscopy study. Chemical investigations using X-ray photoelectron spectroscopy showed the presence of Mn in two valence states. From the observed results we are of the opinion that Zn2+ ions, mainly present at or near grain boundaries, diffuse into manganese oxide to form a stable spinel phase ZnxMn3−xO4 at or near the grain boundaries of ZnO/Zn1−xMnxO. Magnetization measurements did not show any magnetic transition down to 5 K. 相似文献
7.
The effects of annealing temperature and manganese substitution on the formation, microstructure and magnetic properties of MnxZn1−xFe2O4 (with x varying from 0.3 to 0.9) through a solid-state method have been investigated. The correlation of the microstructure and the grain size with the magnetic properties of Mn–Zn ferrite powders was also reported. X-ray diffraction (XRD), a scanning electron microscope (SEM) and a vibrating sample magnetometer (VSM) were utilized in order to study the effect of variation of manganese substitution and its impact on crystal structure, crystalline size, microstructure and magnetic properties of the ferrite powders formed. The XRD analysis showed that pure single phases of Mn–Zn ferrites were obtained by increasing the annealing temperature to 1200–1300 °C. Increasing the annealing temperature to ?1300 °C led to abnormal grain growth with inter-granular pores and this led to a decrease in the saturation magnetization. Moreover, an increase in the Mn2+ ion substitution up to x=0.8 increased the lattice parameter of the formed powders due to the high ionic radii of the Mn2+ ion. Mn–Zn ferrites phases were formed and the positions of peaks were shifted by substituting manganese. The average crystalline size was increased by increasing the annealing temperature and decreased by increasing the substitution by manganese up to 0.8. The average crystalline size was in the range 95–137.3 nm. The saturation magnetization of the Mn–Zn-substituted ferrite powders increased continuously with an increase in the Mn concentration up to 0.8 at annealing temperatures of 1200–1300 °C. Further increase of Mn substitution up to 0.9 led to a decrease of saturation magnetization. The saturation magnetization increased from 17.3 emu/g for the Mn0.3Zn0.7Fe2O4 phase particles produced to 59.08 emu/g for Mn0.8Mn0.2Fe2O4 particles. 相似文献
8.
Nanocrystalline Zn0.5Mn0.5Fe2O4 was synthesized through the pyrolysis of polyacrylate salt precursors prepared via in situ polymerization of the metal salts and acrylic acid. The pyrolysis behavior of the polymeric precursors was studied by use of thermal analysis. The as-obtained product was characterized by powder X-ray diffraction (XRD), transmission electron microscope (TEM), electron diffraction (ED) pattern, scanning electron microscopy (SEM) and electron dispersive X-ray (EDX) analysis. The results revealed that the particle size is in the range of 15–25 nm for Zn-Mn ferrites with good crystallinity. Magnetic properties of the sample at 300 K were measured using a vibrating sample magnetometer, which showed that the sample exhibited characteristics of superparamagnetism. 相似文献
9.
J. López L.F. González-BahamónJ. Prado J.C. CaicedoG. Zambrano M.E. GómezJ. Esteve P. Prieto 《Journal of magnetism and magnetic materials》2012,324(4):394-402
Ferrofluids are colloidal systems composed of a single domain of magnetic nanoparticles with a mean diameter around 30 nm, dispersed in a liquid carrier. Magnetic Co(1−x)ZnxFe2O4 (x=0.25, 0.50, 0.75) ferrite nanoparticles were prepared via co-precipitation method from aqueous salt solutions in an alkaline medium. The composition and structure of the samples were characterized through Energy Dispersive X-ray Spectroscopy and X-ray diffraction, respectively. Transmission Electron Microscopy (TEM) studies permitted determining nanoparticle size; grain size of nanoparticle conglomerates was established via Atomic Force Microscopy. The magnetic behavior of ferrofluids was characterized by Vibrating Sample Magnetometer (VSM); and finally, a magnetic force microscope was used to visualize the magnetic domains of Co(1−x)ZnxFe2O4 nanoparticles. X-ray diffraction patterns of Co(1−x)ZnxFe2O4 show the presence of the most intense peak corresponding to the (311) crystallographic orientation of the spinel phase of CoFe2O4. Fourier Transform Infrared Spectroscopy confirmed the presence of the bonds associated to the spinel structures; particularly for ferrites. The mean size of the crystallite of nanoparticles determined from the full-width at half maximum of the strongest reflection of the (311) peak by using the Scherrer approximation diminished from (9.5±0.3) nm to (5.4±0.2) nm when the Zn concentration increases from 0.21 to 0.75. The size of the Co-Zn ferrite nanoparticles obtained by TEM is in good agreement with the crystallite size calculated from X-ray diffraction patterns, using Scherer's formula. The magnetic properties investigated with the aid of a VSM at room temperature presented super-paramagnetic behavior, determined by the shape of the hysteresis loop. In this study, we established that the coercive field of Co(1−x)ZnxFe2O4 magnetic nanoparticles, the crystal and nanoparticle sizes determined by X-ray Diffraction and TEM, respectively, decrease with the increase of the Zn at%. Finally, our magnetic nanoparticles are not very hard magnetic materials given that the hysteresis loop is small and for this reason Co(1−x)ZnxFe2O4 nanoparticles are considered as soft magnetic material. 相似文献
10.
C.S. ZhangL. Yang 《Journal of magnetism and magnetic materials》2012,324(8):1469-1472
Core-shell Co(1−x)NixFe2O4/polyaniline nanoparticles, where the core was Co(1−x)NixFe2O4 and the shell was polyaniline, were prepared by the combination of sol-gel process and in-situ polymerization methods. Nanoparticles were investigated by Fourier transform spectrometer, X-ray diffraction diffractometer, Scanning electron microscope, Differential thermal analysis and Superconductor quantum interference device. The results showed that the saturation magnetization of pure Co(1−x)NixFe2O4 nanoparticles were 57.57 emu/g, but Co(1−x)NixFe2O4/polyaniline composites were 37.36 emu/g. It was attributed to the lower content (15 wt%), smaller size and their uneven distribution of Co(1−x)NixFe2O4 nanoparticles in the final microsphere composites. Both Co(1−x)NixFe2O4 and PANI/Co(1−x)NixFe2O4 showed superparamagnetism. 相似文献
11.
Zn1−xNixFe2O4 ferrite nanoparticles were prepared by sol–gel auto-combustion and then annealed at 700 °C for 4 h. The results of differential thermal analysis indicate that the thermal decomposition temperature is about 210 °C and Ni–Zn ferrite nanoparticles could be synthesized in the self-propagating combustion process. The microstructure and magnetic properties were investigated by means of X-ray diffraction, scanning electron microscope, and Vibrating sample magnetometer. It is observed that all the spherical nanoparticles with an average grain size of about 35 nm are of pure spinel cubic structure. The crystal lattice constant declines gradually with increasing x from 0.8435 nm (x=0.20) to 0.8352 nm (x=1.00). Different from the composition of Zn0.5Ni0.5Fe2O4 for the bulk, the maximum Ms is found in the composition of Zn0.3Ni0.7Fe2O4 for nanoparticles. The Hc of samples is much larger than the bulk ferrites and increases with the enlarging x. The results of Zn0.3Ni0.7Fe2O4 annealed at different temperatures indicate that the maximum Ms (83.2 emu/g) appears in the sample annealed at 900 °C. The Hc of Zn0.3Ni0.7Fe2O4 firstly increases slightly as the grain size increases, and presents a maximum value of 115 Oe when the grains grow up to about 30 nm, and then declines rapidly with the grains further growing. The critical diameter (under the critical diameter, the grain is of single domain) of Zn0.3Ni0.7Fe2O4 nanoparticles is found to be about 30 nm. 相似文献
12.
R. Thirunakaran A. Sivashanmugam Charles W. Dunnill 《Journal of Physics and Chemistry of Solids》2008,69(8):2082-2090
Pristine spinel LiMn2O4 and LiAlxMn2−xO4 (x=Al: 0.00-0.40) with sub-micron sized particles have been synthesized using fumaric acid as chelating agent by sol-gel method. The synthesized samples were subjected to thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV) and galvanostatic cycling studies. The TGA curve of the gel shows several weight-loss regions stepwise amounting to 55% till 800 °C attributed to the decomposition of the precursors. Calcination to higher temperatures (800 °C) yields pure-phase spinel (LiAlxMn2−xO4), as it is evident from the high-intensity XRD reflections matching to the standard pattern. SEM and TEM studies confirm that the synthesized grains are of uniform regular surface morphology. FT-IR studies show stretching and bending vibration bands of Li-O, Li-Al-Mn-O. LiAl0.1Mn1.90O4 spinel was found to deliver discharge capacity of 139 mA h/g during the first cycle with columbic efficiency of 97%. LiAl0.1Mn1.90O4 spinel exhibits the high cathodic peak current indicating better electrochemical performance. Low doping (x=0.1) of Al is found to be beneficial in stabilizing the spinel structure. 相似文献
13.
Y. Kimishima M. Uehara K. Irie S. Ishihara T. Yamaguchi M. Saitoh K. Kimoto Y. Matsui 《Journal of magnetism and magnetic materials》2008
We tried to prepare the bulk dilute ferromagnetic semiconductor (DMS) by mechanical milling (MM). Experimental results were as following: (1) The observation of X-ray diffraction and transmitting electron microscopy showed that the particle diameter of host ZnO powder were reduced to about 10 nm by MM. (2) The MM for the mixtures of V2O5/ZnO or γ-Fe2O3/ZnO realizes the V- or Fe-doped ZnO nano-powders. (3) The values of magnetization under the field of 5 kOe were nearly saturated to 0.8×10−3 to 3×10−3 μB/V-ion for VxZn1−xO (x=0.05, 0.1 and 0.2), and 0.2–0.3 μB/Fe-ion for FexZn1−xO (x=0.05 and 0.1) at room temperature. The above results show that the ferromagnetic DMS powder of VxZn1−xO and FexZn1−xO were successfully prepared by MM method. 相似文献
14.
Mohammad Javad Nasr Isfahani Maxym Myndyk Armin Feldhoff Vladimir Šepelák 《Journal of magnetism and magnetic materials》2009,321(3):152-156
Mn0.5Zn0.5Fe2O4 nanoparticles (10-30 nm) have been prepared via mechanochemical processing, using a mixture of two single-phase ferrites, MnFe2O4 and ZnFe2O4. SQUID measurements (field-cooled magnetization curves and hysteresis loops) were performed to follow the mechanically induced evolution of the MnFe2O4/ZnFe2O4 mixture submitted to the high-energy milling process. The resulting single MnZn nanoferrite phase was characterized by SQUID (M-H curve), Faraday balance (M-T curve) and transmission electron microscopy. The magnetic characteristics of the mechanosynthesized material were compared with those of bulk Mn0.5Zn0.5Fe2O4. It was found that the saturation magnetization of nanostructured Mn0.5Zn0.5Fe2O4 (87.2 emu/g) is lower than that of the bulk Mn0.5Zn0.5Fe2O4, but, the Néel temperature of the sample (583 K) is higher than that of the bulk Mn0.5Zn0.5Fe2O4. 相似文献
15.
A series of samples ZnxFe3−xO4 have been prepared by the chemical coprecipitation technique and characterized by X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS). XRD demonstrates all the samples of ZnxFe3−xO4 have a spinel structure same as Fe3O4. The magnetic hysteresis loops of ZnxFe3−xO4 obtained from VSM indicate that the saturation magnetization has a maximum when x is ∼1/3. The chemical states of Fe atoms and Zn atoms in zinc ferrites have been measured using XPS and Auger electron spectroscopy (AES). The Fe 2p core-level XPS spectra and Zn L3M45M45 Auger peaks have been analyzed and the results have been discussed in correlation with the samples’ magnetic properties. These results suggest most of Zn atoms occupy the tetrahedral sites and a small amount of them occupy the octahedral sites. 相似文献
16.
Changzhen Liu Dawei Meng Haixia Pang Xiuling Wu Jing Xie Xiaohong Yu Long Chen Xiaoyang Liu 《Journal of magnetism and magnetic materials》2012
Zn1–xFexO (x=0–0.05) nanoparticles were synthesized without a catalyst by a two-step method. Fe was doped into ZnO by a source of metallic Fe sheets in a solid–liquid system at 80 °C, and the Zn1−xFexO nanoparticles were obtained by annealing at 300 °C. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy were used to characterize the structural properties of the as-grown Zn1−xFexO. The optical properties were determined by Infrared and Ultraviolet–visible spectroscopy. The results confirm that the crystallinity of the ZnO is deteriorated due to Fe-doping. XPS results show that there is a mixture of Fe0+ and the Fe3+ in the representative Zn0.95Fe0.05O sample. The optical band gap of Zn1−xFexO is enhanced with increasing of Fe-doping. Room temperature ferromagnetism was observed in all the Fe-doped ZnO samples. 相似文献
17.
Synthesis and characterization of Ni-Zn ferrite nanoparticles 总被引:1,自引:0,他引:1
G.S. Shahane Ashok Kumar R.P. Pant 《Journal of magnetism and magnetic materials》2010,322(8):1015-168
Nickel zinc ferrite nanoparticles NixZn1−xFe2O4 (x=0.1, 0.3, 0.5) have been synthesized by a chemical co-precipitation method. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, electron paramagnetic resonance, dc magnetization and ac susceptibility measurements. The X-ray diffraction patterns confirm the synthesis of single crystalline NixZn1−xFe2O4 nanoparticles. The lattice parameter decreases with increase in Ni content resulting in a reduction in lattice strain. Similarly crystallite size increases with the concentration of Ni. The magnetic measurements show the superparamagnetic nature of the samples for x=0.1 and 0.3 whereas for x=0.5 the material is ferromagnetic. The saturation magnetization is 23.95 emu/g and increases with increase in Ni content. The superparamagnetic nature of the samples is supported by the EPR and ac susceptibility measurement studies. The blocking temperature increases with Ni concentration. The increase in blocking temperature is explained by the redistribution of the cations on tetrahedral (A) and octahedral (B) sites. 相似文献
18.
M.H.R. KhanA.K.M. Akther Hossain 《Journal of magnetism and magnetic materials》2012,324(4):550-558
A series of polycrystalline ferrites having nominal chemical composition Co0.50−xMnxZn0.5Fe2O4 (0<x<0.4) have been synthesized by the solid-state reaction technique. The XRD analysis confirms single phase cubic spinel structure for all compositions. Lattice constant increases from 0.84195 to 0.84429 nm with the increasing Mn content and obeys Vegard's law. The average grain size increases by increasing both Mn content and sintering temperatures. Room temperature saturation magnetization increases for x=0.1 and decreases for increasing Mn content. The coercivity decreases with increasing Mn content due to the decrease of anisotropy constant. A reentrant spin glass behavior of these samples is observed from the zero field cooled magnetization measurements. The real part of the initial permeability increases by increasing both Mn content and sintering temperatures. This is due to the homogeneous grain growth and densification of the ferrites. The highest initial permeability 137 is observed for x=0.4 sintered at 1573 K on the other hand, the highest relative quality factor (2522) is obtained for the sample Co0.2Mn0.3Zn0.5Fe2O4 sintered at 1523 K. The Mn substituted Co0.50−xMnxZn0.5Fe2O4 ferrites showed improved magnetic properties. 相似文献
19.
J. Das D.K. MishraD.R. Sahu S.K. PradhanB.K. Roul 《Journal of magnetism and magnetic materials》2011,323(5):641-645
Mn-doped ZnO samples having composition Zn1−xMnxO (x=0.02, 0.04 and 0.05) were synthesized by solid state reaction technique with varying concentration of Mn from 0.02 to 0.05. Evidence of room temperature ferromagnetism was observed only in the composition Zn0.98Mn0.02O sintered at 500 °C. Our XRD pattern confirms the presence of Mn3O4 impurity phase in all the Zn1−xMnxO samples with the exception of Zn0.98Mn0.02O. We emphasize that the appearance of Mn3O4 phase in the system forbids the exchange type of interaction between the Mn ions and suppresses the ferromagnetism in all the Mn over-doped Zn1−xMnxO (x>0.02) system. SEM microstructure study also supports the interruption of exchange type of interaction inside the system with the increase in Mn concentration in the sample. Interestingly, for this particular composition, Zn0.98Mn0.02O sintered at 500 °C, glassy ferromagnetism type of transition is observed at low temperature. This type of transition is attributed to the formation of the oxides of Mn clusters at low temperature. 相似文献
20.
In this paper, the structural, thermal and magnetic properties of Ni1−xMnxFe2O4 are presented. It is observed that high concentration of Mn2+ ions into NiFe2O4 tends to reduce the particle size. Calcination at 500 °C has resulted in the growth of Ni1−xMnxFe2O4 nanoparticles, but the calcination at 900 °C has led to the evaporation of the majorities of the polyvinyl alcohol. After calcination at 900 °C, crystallographically oriented NiMnFe2O4 nanoparticles are formed. These Ni1−xMnxFe2O4 nanoparticles show hysteresis behaviour upon magnetization. On the other hand, saturation magnetization (Ms) values decreases with increasing Mn content in ferrite due to the influence of Mn2+ ion in the sub lattice. 相似文献