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1.
Effect of annealing treatments on the microwave electromagnetic properties of amorphous FeCuNbSiB microwires 下载免费PDF全文
The amorphous FeCuNbSiB microwires are fabricated by using the
melt extraction method and annealed separately at temperatures
T = 573, 673, 723 and 773K for 1h. The effect of annealing
treatment on the microwave electromagnetic properties of
FeCuNbSiB wires/wax composites has been investigated for the
first time. It is found that in a frequency range of
0.5--4.0GHz, the complex permittivity, permeability, magnetic
and electric loss tangents of FeCuNbSiB wires/wax composites are
strongly dependent on the annealing temperature and frequency.
For T = 573, 723 and 773K, two resonance peaks are found at
frequency f = 1.2 and 3.3GHz. However, for T = 673K,
only one resonance peak occurs at f = 3.3GHz. The resonance
peak at f = 1.2GHz is believed to be due to the
stress-induced anisotropy, while the resonance peak at f =
3.3GHz is attributed to the random anisotropy. 相似文献
2.
Amorphous Ni-P nanotubes are fabricated through electroless chemical deposition inside an anodic aluminum oxide template. The hysteresis loops of Ni-P nanotube arrays are each found to exhibit an unusual isotropic behaviour, which is believed to be due to the competition results between the shape anisotropy and the magnetostatic interaction among nanotubes. The dynamic dependence of permittivity on the frequency spectrum is fitted to the Lorentzian-type dispersion law. The permeability dispersion behaviours have been fitted based on the Kittel equation. Electromagnetic wave absorption properties of Ni-P nanotubes/paraffin composites with different values of thickness (t) are clearly shown by a three-dimensional graph. Furthermore, the bandwidths of composites with different "t" values can be well presented by a two-dimensional contour graph, which is a novel presentation form. The results show that the composites each have a good microwave absorption performance with t larger than 5.5 mm and with the frequency around 8 gigahertz. 相似文献
3.
Flake-shaped and sphere-shaped Fe3Al powder-paraffine composites have been studied in the microwave frequency range. Mössbauer results show that the flake-shaped Fe3Al particles have easy magnetization plane, which indicates that it is planar-anisotropy. Enhanced permeability is achieved in flake-shaped Fe3Al compared with the sphere-shaped Fe3Al. The permeability is further enhanced by using a rotational orientation method. The complex permeability can be characterized by the superposition of two types of magnetic resonance. The resonance peak at high frequency is attributed to the natural resonance, while the peak at low frequency is attributed to the domain-wall resonance. By employing the shape effect and the rotational orientation, the peak frequency of reflection loss for the oriented sample was adjusted to L-band. The planar-anisotropy Fe3Al powder-paraffine composite can be attractive candidates for thinner microwave absorbers in L-band (1-2 GHz). 相似文献
4.
5.
Soft magnetic properties of Co-based amorphous alloy of the composition Co67Fe4Ni2Si15B12 have been investigated by isothermal heat treatment up to the conventional crystallization temperature. In the as-cast condition the Curie temperature of the sample is 272 °C and saturation magnetization is 74 emu/g. Magnetic properties undergo variation depending on the heat treatment temperature. For the heat treatment temperatures of around 420 and 490 °C, superior soft magnetic properties are obtained. For both the temperatures initial permeability, μ′ reaches value up to ten times the value of permeability in the as-received samples. Annealing effect on giant magneto-impedance has been observed for the current-driving frequencies of 4.5 and 6 MHz. Field dependence of magneto-impedance shows hysteresis at low field, which is related to the changes in the magnetization process of the sample. 相似文献
6.
7.
Amorphous-crystalline dual-layer structures resulting from metastable liquid phase separation in (Fe50Co25B15Si10)80Cu20 melt-spun ribbons 下载免费PDF全文
(Fe50Co25B15Si10)80Cu20 ribbons are prepared by using the single-roller melt-spinning method. A dual-layer structure consisting of a (Fe, Co)-rich amorphous phase and a Cu-rich crystalline phase forms due to metastable liquid phase separation before solidification. The magnetic hysteresis loops of the as-quenched and annealed samples are measured at room temperature. It is indicated that the coercivity of the ribbon is almost zero in the as-quenched state. The crystallization leads to the increase of coercivity and decrease of saturation magnetization. 相似文献
8.
9.
A. Grabias M. Kopcewicz J. Latuch M. P?ka?a 《Journal of magnetism and magnetic materials》2010,322(20):3137-3141
Structural and magnetic properties of two rapidly solidified and post-annealed Fe60Pt15B25 and Fe60Pt25B15 alloys are compared. The as-quenched Fe60Pt15B25 ribbon was fully amorphous whereas in the Fe60Pt25B15 alloy the amorphous phase coexists with an fcc FePt disordered solid solution. Differential scanning calorimetry curves of both alloys reveal a single exothermal peak with onset temperatures of 873 and 847 K for Fe60Pt15B25 and Fe60Pt25B15, respectively. Magnetically hard, tetragonal ordered L10 FePt and magnetically soft Fe2B nanocrystalline phases were formed due to the annealing of the alloys, as indicated by X-ray diffraction and Mössbauer spectroscopy measurements. Two-phase behavior was detected in the temperature dependence of magnetization of the annealed samples. A magnetic hardening was observed for all annealed ribbons. Magnetic properties of the annealed alloys, studied by hysteresis loop measurements, were related to the differences in the relative fractions of the hard and soft magnetic phases calculated from Mössbauer spectra. The alloy with 25 at% Pt exhibits better hard magnetic properties (Hc=437 kA/m, Mr/Ms=0.74) than the alloy with smaller Pt content (Hc=270 kA/m, Mr/Ms=0.73) mainly due to the larger abundance of the ordered tetragonal FePt phase. 相似文献
10.
N.D. Tho N. Chau S.C. Yu H.B. Lee N.D. The L.A. Tuan 《Journal of magnetism and magnetic materials》2006
Effect of annealing on the soft magnetic properties of Fe73.5Si13.5B9Nb3Au1 amorphous ribbon has been investigated by means of structure examination, magnetoimpedance ratio (MIR) and incremental permeability ratio (PR) spectra measured in the frequency range of 1–10 MHz at a fixed current of 10 mA X-ray diffraction analysis showed that the as-cast sample was amorphous and it became nanocrystalline under a proper heat treatment. When annealing amorphous alloy at 530 °C for 30, 60, 90 min, soft magnetic properties have been improved drastically. Among the samples investigated, the sample annealed at 530 °C for 90 min showed the softest magnetic behavior. The MIR and PR curves revealed the desirable changes in anisotropy field depending upon annealing. 相似文献
11.
Zhihao ZhangBeiyu Li Weilong CuiJianxin Xie 《Journal of magnetism and magnetic materials》2011,323(12):1712-1716
Influences of the size factors (glass coating thickness and metallic core diameter) of microwires on GMI effects of the glass-coated Co68Fe4.5Si13.5B14 amorphous microwires were investigated. The results indicated that the GMI effect of the microwires with the same glass coating thickness or the same metallic core diameter was initially increased to a peak and then decreased with an increase in the diameter or the thickness. The glass coating thickness and the metallic core diameter corresponding to the maximum GMI varied with metallic core diameter and glass thickness, respectively. The GMI effect of the microwires with the same geometric size varied remarkably under different cooling rates. Such effect was ascribed to the microstructural changes of the metallic core wire under different cooling rates. The influence of the glass coating thickness on the GMI effect of the microwire was attributed to the synthetical actions of crystallization enthalpy (degree of disorder) and the internal stress. 相似文献
12.
The reflection properties of planar anisotropy Fe50Ni50 powder/paraffin composites have been studied in the microwave frequency range. The permeability of Fe50Ni50 powder/paraffin composites is greatly enhanced by introducing the planar anisotropy, and can be further enhanced by using a rotational orientation method. The complex permeability can be considered as the superposition of two types of magnetic resonance. The resonance peak at high frequency is attributed to the natural resonance, while the peak at low frequency is attributed to the domain-wall resonance. The simulated results of the microwave reflectivity show that the matching thickness, peak frequency, permeability, and permittivity are closely related to the quarter wavelength matching condition. The Fe50Ni50 powder/paraffin composites can be attractive candidates for thinner microwave absorbers in the L-band (1-2 GHz). 相似文献
13.
K. Lal S. K. Chattopadhyay A. K. Meikap S. K. Chatterjee M. Ghosh 《Czechoslovak Journal of Physics》2001,51(9):897-908
A detailed study on the weak localization phenomenon vis-a-vis electron-electron interaction effects in magnetic metallic
glasses has been carried out. We measured the electrical conductivity and magnetoconductivity within the temperature range
1.8≤T≤300K. A maximum on the conductivity versus temperature curve exists atT=T
m. The conductivity was observed to follow aT
1/2 law forT<T
m andT
2 law forT>T
m. Magnetoconductivity data of these alloys indicate the prominence of electron-electron interaction at low temperatures. The
authors have determined the inelastic scattering field and spin-orbit scattering field from the magnetoconductivity data.
The inelastic scattering field obeys aT
p law (p=2) at low temperatures. 相似文献
14.
E. Colavita M. De Crescenzi L. Papagno L.S. Caputi G. Chiarello R. Scarmozzino R. Rosei 《Solid State Communications》1982,41(7):545-548
The electronic properties of the amorphous and sintered Fe80B20 alloys have been studied by electron energy loss spectroscopy. A correlation among energy loss data and X-ray absorption near edge structures has been attempted.Structure-related effects in the electronic properties of Fe80B20 alloy have been found and discussed. 相似文献
15.
H.-Q. Guo B.-G. Shen D.-M. Lin S.-T. Pan 《Journal of magnetism and magnetic materials》1981,23(2):156-164
Magnetic annealing and crystallization kinetics of amorphous ribbons of Fe5Co70Si15B10 were studied. For a toroid stress-relieved at 365°C for 2 h, the anistropy energy Ku obtained by cooling in a magnetic field from 300°C was ≈1.1 × 103erg/cm3 at room temperature. The reorientation of induced anisotropy of this toroid followed the equation for first-order kinetics closely, yielding an activation energy ΔE = 1.9 eV and a pre-exponential frequency factor v0 = 3.2 × 1013s-1. Anisotropy reorientation in a toroid partially stress-relieved at 220°C, although was clearly reversible during 8 cycles of isothermal annealing in tranverse and in longitudinal field, exhibited significant deviations from the equation for first order kinetics. Treating the data in terms of the equation for first order kinetics, a narrow spectrum of activation energy from 1.2 to 1.8 eV, with corresponding frequency factors from 1.8 × 108 s-1 to 5.6 × 1012 s-1, was obtained. The difference in behavior between the two samples is discussed in the light of concepts in structural relaxation recently proposed by T. Egami. Crystallization kinetics was studied on a DSC apparatus, using Kissinger's method. At 10 K/min heating rate, the temperature of incipient crystallization was found to be 770 K. The activation energies found were in the range 4.8–4.2 eV. 相似文献
16.
The complex permittivity (ε′–jε″), complex permeability (μ′–jμ″) and microwave absorption properties of ferrite–polymer composites prepared with different ferrite ratios of 50%, 60%, 70% and 80% in polyurethane (PU) matrix have been investigated in X-band (8.2–12.4 GHz) frequency range. The M-type hexaferrite composition BaCo+20.9Fe+20.05Si+40.95Fe+310.1O19 was prepared by solid-state reaction technique, whereas commercial PU was used to prepare the composites. At higher GHz frequencies, ferrite's permeabilities are drastically reduced, however, the forced conversion of Fe+3 to Fe+2 ions that involves electron hopping, could have increased the dielectric losses in the chosen composition. We have measured complex permittivity and permeability using a vector network analyzer (HP/Agilent model PNA E8364B) and software module 85071. All the parameters ε′, ε″, μ′ and μ″ are found to increase with increased ferrite contents. Measured values of these parameters were used to determine the reflection loss at various sample thicknesses, based on a model of a single-layered plane wave absorber backed by a perfect conductor. The composite with 80% ferrite content has shown a minimum reflection loss of −24.5 dB (>99% power absorption) at 12 GHz with the −20 dB bandwidth over the extended frequency range of 11–13 GHz for an absorber thickness of 1.6 mm. The prepared composites can fruitfully be utilized for suppression of electromagnetic interference (EMI) and reduction of radar signatures (stealth technology). 相似文献
17.
The first-order phase transition in Gd5Si2Ge2 is sensitive to both magnetic field and pressure. It may indicate that the influences of the magnetic field and the pressure on the phase transition are virtually equivalent. Moreover, theoretical analyses reveal that the total entropy change is almost definite at a certain Curie temperature no matter whether the applied external field is a magnetic field or a pressure. The entropy change curve can be broadened dramatically under pressure, and the refrigerant capacity is improved from 284.7 J/kg to 447.0 J/kg. 相似文献
18.
Hydrogenation, structure and magnetic properties of La(Fe0.91Si0.09)13 hydrides and deuterides 下载免费PDF全文
Hydrogenation, crystal structure and magnetic properties of La(Fe0.91Si0.09)13H(D)y have been studied by pressure-composition isotherms (PCI), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and magnetization measurements. The maximum absorption capacity is found to be 1.9 H(D) atoms per formula unit as a solid solution. All hydrides and deuterides crystallize in the NaZn13-type cubic structure with the lattice parameter increasing linearly with H(D) concentration. The H(D) absorption enhances the Curie temperature significantly. The magnetic entropy change of the highly H-absorbed compound La(Fe0.91Si0.09)13H1.81 reaches ~26 J/kg·K under a magnetic field change of 5 T near the Curie temperature TC = 350 K. No observable isotope effect seems to imply that only the magnetovolume effect is responsible for the strong interplay between magnetism and lattice. 相似文献
19.
在CO2激光功率为50—300W、扫描速度为20mm/s、激光散光斑为20mm照射条件下 ,诱导非 晶Fe735Cu1Nb3Si135B9带中发生结构重组,产生定量纳米α-F e(Si)晶相形成双相组织结构材料. 利用穆斯堡尔谱研究了非晶Fe735C u1Nb3Si135B9合金激光纳米化的 超精细结构. 实验结果表明,激光诱导非晶 Fe735Cu1Nb3Si135B 9纳米化后,其超精细磁场的分布随 着激光功率变 化由单峰向双峰变化,在高功率辐照时, 出现了双峰分布,并且峰位向高场移动. 高激光 功率辐照非晶Fe735Cu1Nb3Si135 sub>B9合金纳米晶化相有四种超精细结 构,即2个超精细磁场较小的初晶相和2个超精细磁场较大的纳米晶化相. 其中超精细磁场较 大(17—25MA/m)的α-Fe(Si)相为DO3结构.
关键词:
激光
纳米晶α-Fe(Si)
735Cu1Nb< sub>3Si135B9')" href="#">非晶Fe735Cu1Nb< sub>3Si135B9
超精细结构
超精细磁场 相似文献