Mössbauer Effect Study of Corroded Amorphous Alloy Fe78B13Si9

Mössbauer effect and Scanning Electron Microscopy were used to investigate the effect of immersing the amorphous alloy Fe₇₈B₁₃Si₉ in 3% NaCl solution over different periods and different pH. The results indicated that the average angle of orientation of the magnetic moments had increased with increasing time of immersion and decrease in pH value. The corrosion product was found to be lepidocrocite (γ-FeOOH).     

Fe78B13Si9、(Fe0.99Mo0.01)78B13Si9非晶合金的激波晶化实验研究

 研究了Fe₇₈B₁₃Si₉、(Fe_0.99Mo_0.01)₇₈B₁₃Si₉非晶合金的激波晶化行为。激波是由氢-氧爆炸产生的。实验结果表明：激波能使非晶合金在微秒时间内晶化,晶化主相为α-Fe基固溶体,次晶化相为Fe₃Si,且观察到α-Fe基因溶体晶格常数变小。用DTA分析进一步证实：激波晶化是比较完全的,晶化相相当稳定。     

Vickers Microhardness and Hyperfine Magnetic Field Variations of Heat Treated Amorphous Fe78Si9B13 Alloy Ribbons

Amorphous Fe₇₈Si₉B₁₃ alloy ribbons were heat treated between 296 and 763 K, using heating rates between 1 and 4.5 K/min. Whereas one ribbon partially crystallized at T _x = 722 K, the other one partially crystallized at T _x = 763 K. The partially crystallized ribbon at 722 K, heat treated using a triangular form for the heating and cooling rates, was substantially less fragile than the partially crystallized at 763 K where a tooth saw form for the heating and cooling rates was used. Vickers microhardness and hyperfine magnetic field values behaved almost concomitantly between 296 and 673 K. The Mössbauer spectral line widths of the heat-treated ribbons decreased continuously from 296 to 500 K, suggesting stress relief in this temperature range where the Vickers microhardness did not increase. At 523 K the line width decreased further but the microhardness increased substantially. After 523 K the line width behave in an oscillating form as well as the microhardness, indicating other structural changes in addition to the stress relief. Finally, positron lifetime data showed that both inner part and surface of Fe₇₈Si₉B₁₃ alloy ribbons were affected distinctly. Variations on the surface may be the cause of some of the high Vickers microhardness values measured in the amorphous state.     

Resistivity and magnetoresistance of Fe80B20 and Fe78B13Si9 amorphous glasses

Summary The electrical resistivity of Fe₈₀B₂₀ and Fe₇₈B₁₃Si₉ amorphous glasses as a function of temperature from 293 K down to 15 K was measured, and it was found to fit quite well with the model given by Cote and Meisel. Comparison between our resistivity measurements of Fe₈₀B₂₀ and others was made, where some differences were found. These resistivity differences are evidence for a variety of amorphous atomic arrangements of the samples. The longitudinal magnetoresistance of Fe₈₀B₂₀ and Fe₇₈B₁₃Si₉ at 293K and 77K was measured in a low magnetic field. The observed magnetoresistance shows a typical field dependence known for ferromagnetic materials.     

Uniform radio frequency fields in loop-gap resonators for EPR spectroscopy

At high frequencies, e.g., Q- and W-bands, it is advantageous to make the axial length of loop-gap resonators (LGRs) at least as long as a free-space wavelength. The opposite scaling of capacitance and inductance with LGR length suggests that the length of an LGR can be increased without limit, with the axial radio frequency (rf) field profiles and resonance frequency independent of length. This scaling is accurate for resonator dimensions much less than one free-space wavelength. When the resonator length approaches one-tenth of a free-space wavelength, the rf field uniformity degrades. From one-tenth to one free-space wavelength, computer simulations and experimental measurements show that the axial magnetic field energy density profile is peaked in the center of the LGR, gradually decreases from 25 to 50% at a distance one radius from the end, and rapidly there-after. The nonuniformity is of two types. One type, in the vicinity of one radius of the end, is caused by the flaring of the field as it curves from the central loop to the end region, into the larger return loop(s). The other type, in the central part of the resonator, is caused by impedance mismatch at the ends of the LGR. The LGR may be viewed as a strongly reentrant (ridge) waveguide nearly open at both ends and supporting a standing wave. A transmission line model relates the central nonuniformity to the fringing capacitance and inductance at the ends of the resonator. This nonuniformity can be eliminated in several ways including modifying the ends of the LGR by adding a small metal bridge or a dielectric ring. These uniformity trimming elements increase the fringing capacitance and/or decrease the fringing inductance. With trimmed ends, LGRs can be made many free-space wavelengths long. The maximum resonator length is determined by the proximity in frequency of the fundamental LGR mode to the next highest frequency mode as well as the quality factor. Results of this theory are compared and conformed with finite-element simulations. This theory connects the uniform LGR with the uniform field cavity resonators previously introduced by this laboratory.     

Investigation of X-ray diffraction and positron life times in Fe78Si9B13 alloys of amorphous and crystalline structures before and after hydriding

Measurements of mean positron life-times and X-ray diffraction were carried out in unhydrided alloys Fe₇₈Si₉B₁₃ of amorphous and crystalline structures, and after hydriding them. The process of hydriding was carried out at a pressure of 55.773 × 10⁵ N/m². during 168 h. The crystalline samples were obtained after annealing the amorphous alloy Fe₇₈Si₉B₁₃ at 673, 773 and 873 K, respectively. The results obtained after the hydriding process suggest thatan additional electron energy band is formed due to introducing hydrogen inside the samples. The annealing process shows that there exists a nonmonotonic relation between the concentration of free electrons and the degree of order to the structure.     

Annealing embrittlement of Fe78Si9B13 (METGLAS-2605S2)

The ductile to brittle transition that occurs in amorphous Fe₇₈Si₉B₁₃ (METGLAS-2605S2) has been investigated using mechanical measurements over the temperature range 250–370 °C. The fracture toughness values, K _Ic , have been determined for a range of annealing times (5–30 min) and cooling rates of 15–45 °C/min. A pronounced ductile to brittle transition is observed around 310(10) °C although no obvious structural changes are evident as indicated by x-ray diffraction. Comparison of transmission and back-scattered conversion electron ⁵⁷Fe Mössbauer spectra for the bulk as-received ribbon in the ductile state ( $K_{Ic}=52~{\rm MPa} \cdot \sqrt{m}$ ) and the ribbon annealed to the brittle state ( $K_{Ic}\sim10~{\rm MPa} \cdot \sqrt{m}$ ) indicates magnetic texture effects in both the bulk and on the surface of these amorphous ribbons, related to the magnetostriction resulting from the quenched-in stress during the ribbon production process, and the ensuing stress-relief upon annealing.     

The collapse effect of Mössbauer spectra in radio frequency fields

The Collapse effect of amorphous alloys Fe38Ni38Mo4B20 and Fe48Ni31Si10B11 in the rf field was investigated by means of the measurement of the temperature of the samples in rf field and the observations of aftereffect of the strong rf field. The collapse observed is caused by rf induced magnetic fluctuation rather than thermal effects. The results agree well with the model based on a magnetic cluster picture.     

与Al发生扩散反应的非晶(Fe0.99Mo0.01)78Si9B13晶化

高压下与Ａｌ发生扩散反应的非晶（Ｆｅ０．９９Ｍｏ０．０１）７８Ｓｉ９Ｂ１３（ＦＭＳＢ）的不同。与Ａｌ反应的ＦＭＳＢ非晶在３．０￣５．０ＧＰａ,７８０￣９００Ｋ热处理时,晶化为α－Ｆｅ（Ａｌ）和次亚稳非晶合金;在这一压力范围以外,７２０￣９００Ｋ热处理时,晶化为α－Ｆｅ（Ｓｉ）,Ｆｅ３Ｂ或Ｆｅ２Ｂ。与Ａｌ发生反应的ＦＭＳＢ非晶可能通过与Ａｌ的扩散反应在Ａｌ／ＦＭＳＢ界面开始晶化。压力和温度对晶化过程     

连续超短电脉冲对非晶Fe_(78)Si_9B_(13)合金软磁性能的影响

对非晶Fe78Si9B13合金进行了连续超短脉冲电流处理,测量了处理后试样的综合软磁性能.实验证明,当基体金属相αFe(Si)析出量为3%左右,αFe(Si)颗粒大小约为33nm时,可以获得较好的软磁性能.如最大磁导率提高、矫顽力明显降低.利用随机各向异性模型讨论了连续超短脉冲电流处理改善非晶Fe78Si9B13合金软磁性能的机理     

Ionization by drift and ambipolar electric fields in electronegative capacitive radio frequency plasmas

Unlike α- and γ-mode operation, electrons accelerated by strong drift and ambipolar electric fields in the plasma bulk and at the sheath edges are found to dominate the ionization in strongly electronegative discharges. These fields are caused by a low bulk conductivity and local maxima of the electron density at the sheath edges, respectively. This drift-ambipolar mode is investigated by kinetic particle simulations, experimental phase-resolved optical emission spectroscopy, and an analytical model in CF(4). Mode transitions induced by voltage and pressure variations are studied.     

Nanocrystallization process and ferromagnetic properties of amorphous (Fe0.99Mo0.01)78Si9B13 ribbons

The nanocrystallization process of soft ferromagnetic (Fe_0.99Mo_0.01)₇₈Si₉B₁₃ ribbons has been studied in detail. Microstructural and ferromagnetic properties are examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy (MS), differential scanning calorimetry (DSC) and magnetization measurements. The Curie and crystallization temperatures are determined to be T_C=665 K and T_x=750 K, respectively. The T_x value is in well agreement with DSC measurement results. XRD patterns had shown two metastable phases (Fe₂₃B₆, Fe₃B) which were formed under in situ nanocrystallization process. These metastable phases embedded in the amorphous matrix have a significant effect on magnetic ordering. The ultimate nanocrystalline (NC) phases of α-Fe(Mo, Si) and Fe₂B at optimum annealing temperature had been observed respectively. It is notable that the magnetization of the amorphous phase decreases more rapidly with increasing temperature than those of NC ferromagnetism, which suggest the presence of the distribution of exchange interaction in the amorphous phase or high metalloid contents.     

Graded image segmentation of brain tissue in the presence of inhomogeneous radio frequency fields

Image segmentation is used increasingly to interpret MR spectroscopic data of the brain, using image contrast to identify gray matter (GM), white matter (WM), and cerebral spinal fluid (CSF). T(1)- or T(2)-weighted images are typically used, but poor shimming, susceptibility effects, and small variations in B(1) and receptivity cause difficulties in tissue identification. Quantitative imaging of T(1) can reduce many of these difficulties but is still subject to complications when B(1) has large variations like those observed with the surface coils often used for spectroscopy. In this study, B(1) imaging was implemented to support quantitative imaging of T(1) with either a surface coil or a volume coil. The T(1) observed by this method is a continuous function across mixtures of WM/GM and GM/CSF, and this function was measured and used to convert the images of T(1) to maps of percent GM, WM, and CSF.     

Electro-optic fiber sensor for amplitude and phase detection of radio frequency electromagnetic fields

We present a miniature fiber-optic electromagnetic field (EMF) sensor that is capable of simultaneously detecting the amplitude and phase of an EMF in the range of 0.1-6 GHz. We focus on magnetic field measurements, since the H-field is more significant in our target applications due its direct relation to the current. The sensor is based on an open optical platform to which various antennas can be attached and contains a radio-frequency amplifier for signal conditioning and a vertical-cavity surface-emitting laser as an electro-optic converter. The millimeter size and the full electrical isolation of the sensor allow EMF detection with minimal disturbance. We have characterized the sensor in the near field of a lambda/2 dipole, a rectangular waveguide, and a microstrip line, and we explain the experimental results with a simple theoretical model confirming the mapped near-field distribution of the investigated field source.     

Mathematical modelling of the ion motion in the isochronous magnetic and radio frequency electric fields

The results of mathematical modelling of the ion motion show the possibility of the phase focusation of the ions with utilization of the radial force. This force is realized with a radial component of electric field. The beam monochromatization is analyzed simultaneously.     

Amorphous phase formation rules in high-entropy alloys

There have been many interesting studies on high-entropy alloys(HEAs), also known as multi-component(MC) alloys(MCAs), in recent years. MC metallic-glasses(MGs) have shown the potential to express the advantages of MCAs and MGs in tandem. Amorphous phase formation rules are a crucial issue in the HEA and MCA field. For equal or near-equal atomic ratio alloys, mixed-entropy among the elements has a significant effect on the phase formation. This paper focuses on HEA amorphous phase formation rules. In the first two sections, the recent progress in amorphous phase formation in HEAs and MCAs is reviewed, including the effective factors and correlative parameters related to amorphous phase formation. In the third section, novel MCMGs including high-entropy(HE) bulk-metallic-glass(HE-BMG) and MCMG films developed in recent decades are summarized, and the giant-magnetic-impedance(GMI) effect of MC amorphous fibers is discussed.     

Spontaneous magnetization of Fe - Mn - B Amorphous alloys under high pressures

Abstract

We have investigated the influence of high pressure (up to 2 GPa) on the spontaneous magnetization of six Fe_80-x Mn_x B₂₀ alloys (x = 6, 10, 15, and three alloys with x close to 20). In all cases a decrease of spontaneous magnetization with pressure was noticed, in some considerable.     

Fe78−xNIxSi8B14 amorphous alloys characterized by Mössbauer spectroscopy

Using Mössbauer spectroscopy we have investigated a set of Fe_78?xNi_xSi₈B₁₄ amorphous alloys produced by melt spinning. The samples are all ferromagnetic at room temperature even for an iron concentration as low as 20 at. %. The most interesting observation is the evident asymmetry characterizing the Mossbauer fingerprints for x≦38. We suggest that this asymmetry mirros a change of the short range order.