The Influence of Magnetic Permeability on the Configuration of Magnetic Field in Helimak Device

The Helimak of USA is a plasma physics experimental device designed and built by CASIPP. Its configuration of magnetic field is of very importance during the operation of this device. In this paper, the influence of magnetic permeability on configuration of magnetic field will be discussed due to the effect of weld metal in the vacuum vessel of Helimak, and some conclusion is useful for some engineering designs of the fusion experimental device.

Hard magnetization direction and its relation with magnetic permeability of highly grain-oriented electrical steel

The magnetic properties of highly grain-oriented electrical steel vary along different directions. In order to investigate these properties, standard Epstein samples were cut at different angles to the rolling direction. The hard magnetization direction was found at an angle of 60° to the rolling direction. To compare the measured and fitting curves, when the magnetic field intensity is higher than 7000 A/m, it is appropriate to simulate the relation of magnetic permeability and magnetization angle using the conventional elliptical model. When the magnetic field intensity is less than 3000 A/m, parabolic fitting models should be used; but when the magnetic field intensity is between 3000 and 7000 A/m, hybrid models with high accuracy, as proposed in this paper, should be applied. Piecewise relation models of magnetic permeability and magnetization angle are significant for improving the accuracy of electromagnetic engineering calculations of electrical steel, and these new models could be applied in further industrial applications.

Tappet Chill Depth Measuring by Magnetic Permeability and Inductance Displacement Meter

It is possible to measure different position along the axle direction of tappet.According to the maximum output of signal,the boundary of white iron structure and mottled iron structure can be deduced,and at the same time,it is possible to use inductance displacement meter to show the chill depth which is the distance from the boundary to the end.

Annealing effects on the microwave permittivity and permeability properties of Fe_(79)Si_(16)B_5 microwires and their microwave absorption performances

This paper reports that amorphous magnetic microwires （Fe79Si16Bs） have been fabricated by a melt-extraction technique and have been annealed at 600℃ and 750℃ respectively. Differential scanning calorimeter measurements show that nanocrystalline magnetic phase （α-Fe） has been formed in the amorphous matrix when it was annealed at 600℃. Hard magnetic phase （Fe2B） was formed in the microwires annealed at 750℃, which increases the magnetic coercivity. Microwave permittivity and permeability are found to be dependent on the microstruetures. The permittivity fitting results show that multi Lorentzian dispersion processes exist. For microwires annealed at 750℃, their resonance peaks due to the domain wall movements and natural resonance are found higher than those of microwires annealed at 600℃. The microwave absorption performance of microwires annealed at 600℃ is found better than microwires annealed at 750℃.

Mssbauer studies on the shape effect of Fe_(84.94)Si_(9.68)Al_(5.38) particles on their microwave permeability

Ball milling for long time （such as 10, 20, and 30 h） can transform Fe84.94Si9,68A15.38 alloy powders with irregular shapes into flakes. X-ray diffraction （XRD） and M6ssbauer measurements have proven that the unmilled particles and the flakes obtained by milling for 10 h have the same D03-type superlattice structure. The flakes obtained by milling for 20 h and 30 h have the same disorder a-Fe（Si, A1） structure. There are more than 6 absorption peaks in the transmis- sion MSssbauer spectra （TMSs） for the particles with D03-type superlattice structure, which can be fitted with 5 sextets representing 5 different Fe-site environments. However, only 6 TMS absorption peaks have been found for particles with a disorder a-Fe（Si, A1） structure, which can be fitted with the distributions of M6ssbauer parameters （Bhf, isomer shift）. The TMS results show that the flaky particles have a stronger tendency to possess the planar magnetic anisotropy. As the result, the flakes have larger microwave permeability values than particles with irregular shapes. The conversion electron M6ssbauer spectra （CEMSs） also show the significantly different Fe-sites environments between the alloy surface and the inside.

Microstructural,magnetic and dielectric performance of rare earth ion(Sm^(3+))-doped MgCd ferrites

The combined effects of Sm^(3+)substitution together with the addition of 3 wt%Bi_(2)O_(3)endow Mg Cd ferrites with excellent magnetic permeability and dielectric permittivity.Various concentrations of Sm^(3+)(x=0,0.03,0.06,0.09,0.12and 0.15)were employed to modify the permeability(μ)and permittivity(ε)of the Mg Cd ferrites.X-ray diffraction,scanning electron microscopy(SEM),vibrating sample magnetometry and vector network analysis techniques were used to characterize the samples.The measurement results reveal that the ferrites processed a saturation magnetization of up to 36.8 emu/g and coercivity of up to 29.2 Oe via the conventional solid-state reaction method.The surface morphology SEM confirms that with increasing Sm^(3+)concentration,the grain shape changes from a polygon to a circle.Moreover,the dielectric permittivity can reach a value of 23.The excellent properties obtained in Sm^(3+)-substituted Mg ferrites suggest that they could be promising candidates for modern high-frequency antenna substrates or multilayer devices.

Fabrication and electromagnetic wave absorption properties of amorphous Ni-P nanotubes

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.

Electromagnetic wave absorbing properties and hyperfine interactions of Fe–Cu–Nb–Si–B nanocomposites

The Fe-Cu-Nb-Si-B alloy nanocomposite containing two ferromagnetic phases （amorphous phase and nanophase phase） is obtained by properly annealing the as-prepared alloys. High resolution transmission electron microscopy （HR- TEM） images show the coexistence of these two phases. It is found that Fe-Si nanograins are surrounded by the retained amorphous ferromagnetic phase. Mossbauer spectroscopy measurements show that the nanophase is the D03-type Fe- Si phase, which is employed to find the atomic fractions of resonant 57Fe atoms in these two phases. The microwave permittivity and permeability spectra of Fe-Cu-Nb-Si-B nanocomposite are measured in the frequency range of 0.5 GHz- 10 GHz. Large relative microwave permeability values are obtained. The results show that the absorber containing the nanocomposite flakes with a volume fraction of 28.59% exhibits good microwave absorption properties. The reflection loss of the absorber is less than -10 dB in a frequency band of 1.93 GHz-3.20 GHz.

The Essence and Origin of the Magnetic Constant

In this study, the essence and origin of the magnetic constant are discussed and a mechanism that allows real estimations of the magnetic constant based upon the vacuum density description is proposed. By considering the vacuum as a liquid with a measurable density and the electron as a vortex, hydrodynamic laws are applied to measure the diminished momentum of a rotating electron in a vacuum, thus obtaining a value similar to the experimentally derived value of the magnetic constant. A consequence of this description is that the magnetic constant can be expressed as the shear stress per unit time of the vacuum;this means that it is an observable vacuum parameter and not a fundamental constant.

Enhanced Microwave Absorption for High Filler Content Composite Molded from Polymer Coated Flaky Carbonyl Irons Modified by Silane Coupling Agents

A microwave absorbing sheet with a high complex permeability and a relatively low complex permittivity is obtained by molding of the densely coated flaky carbonyl iron particles(FCIPs)by styrenebutadiene-styrene block copolymer(SBS)in the assistance of coupling agent modification.Direct molding of the core-shell FCIPs without adding extra binder results in a large permeability due to the high filling ratio(55vol%)of absorbents.Importantly,the permittivity is well suppressed by the dense insulate polymer shell on the FCIPs,avoiding the severe impedance mismatch problem of the high filler content microwave absorbing materials.Investigations show that modifying the surface of FCIPs by proper amount of silane coupling agent is critical for the coating quality of the SBS shell,which is verified by resistivity and corrosion current density measurements,and can be interpreted by improved interfacial compatibility between the modified FCIPs and SBS.The obtained microwave absorbing sheet shows a minimum reflection loss of-38.74 dB at 1.57 GHz and has an effective absorption bandwidth from 1.1 to 2.3 GHz at a relatively small thickness of 2 mm.

Dynamic parameters of Tb-Dy-Fe giant magnetostrictive alloy

Tb0.3Dy0.7Fe1.90 <110> oriented rods were prepared by zone melting with unidirectional solidification.The magnetomechanical coupling factor(k33) was measured by magnetomechanical resonance under different DC bias fields up to 77.4 mT.An effective method was provided to calculate sonic velocity,elastic modulus and compliance constant through measuring resonate frequency(fr),and calculate dynamic magnetostriction(d33) via measuring magnetic permeability,magnetomechanical coupling factor(k33) and complia...

M2C Precipitate in Isothermal Tempering of High Co-Ni Alloy Steel

It is possible to measure different position along the axle direction of tappet. According to the maximum output of signal, the boundary of white iron structure and mottled iron structure can be deduced, and at the same time, it is possible to use inductance displacement meter to show the chill depth which is the distance from the boundary to the end.

调控磁导率以优化高熵合金的自旋电子排列实现高效析氧反应

磁场触发的催化剂轨道电子自旋排列已成为促进析氧反应的一种有趣而可行的策略.然而,具有强d-d库仑相互作用的高熵合金(HEAs)催化剂中的磁场增强机制尚未得到充分挖掘.在此,我们设计了具有优异软磁性的高熵合金金属片,在微小磁场下表现出显著的磁场增强催化作用,其磁导率可作为评估磁场增强的描述因子.具体地,仅施加50 mT的磁场,(FeCoNi)_(82.5)Cr_(17.5)HEAs的过电位下降就超过了36mV@10 mA cm^(-2).此外,过电位的降低与HEA的磁导率呈线性关系.原位拉曼光谱与理论计算结果表明,施加磁场可显著提高自旋密度,改善催化剂的3d电子与*O自由基的2p轨道之间的自旋相互作用,从而有效降低速率决定步骤(*O→*OOH)的能量障碍,进而促进O-O的形成.

Rapid determination of iron oxide content in magnetically modified particulate materials

Magnetically responsive composite materials have been used in interesting applications in various areas of bioscience, biotechnology, and environmental technology. In this work, a simple method to determine the amount of magnetic iron oxide nano- and microparticles attached to magnetically-modified partic- ulate diamagnetic materials has been developed using a commercially available magnetic permeability meter, The procedure is fast and enables dry particulate magnetically modified materials to be analysed without any modification or pretreatment. We show that the magnetic permeability can be measured for materials containing up to 20% magnetic iron oxide, The magnetic permeability measurements are highly reproducible.