Preparation and properties of ferromagnetic glass ceramics and glass fibers based on the composition of SiO2-B2O3-Fe2O3-SrO

The ferromagnetic glass ceramics in the system SiO₂-B₂O₃-Fe₂O₃-SrO were prepared via four different fabrication methods, i.e., fiber-drawing, melt-quenching, natural-cooling, and annealing, without performing any nucleation and crystallization heat treatments. The influences of chemical composition and fabrication method on the spontaneous crystallization of magnetite were investigated by X-ray diffraction, scanning and transmission electron microscopy. The X-ray diffraction patterns show the presence of nanometric magnetite crystals in the glass matrix, and the increasing boron oxide can promote the spontaneous crystallization of magnetite. The estimated size of crystallized magnetite varies between 12 and 50 nm. The magnetic properties of the glass ceramics derived from the four fabrication methods were analyzed using a Vibrating sample magnetometer (VSM), Agilent HP8722ES vector network analyzer and Mössbauer spectra. We find that both the saturation magnetization (M_S) and coercivity (H_jc) depend on the chemical composition and fabrication method. The calorimetric measurements were carried out using Orton Standard Dilatometers.     

Ultraviolet Laser Action in Ferromagnetic Zn1?xFexO Nanoneedles

Fe-doped ZnO nanoneedles (NDs) were fabricated by an Ar⁺ ion sputtering technique operated at room temperature. The as-grown samples show both ferromagnetic and lasing properties. The saturated magnetization moment was measured from 0.307 to 0.659 emu cm⁻³ at the field of 10 kOe with various Fe concentrations. Intense ultraviolet random lasing emission was observed from Zn_1 − x Fe _x O NDs at room temperature. The X-ray photoelectron spectroscopy result reveals that the doped Fe atoms occupy the Zn sites and lead to a decrease in oxygen deficiency.     

铁磁材料电磁超声无损检测数值模拟

电磁超声无损检测由于具有无需耦合剂、检测速度快、效率高等优点而被应用于众多工程领域。文章研究了碳素钢电磁超声无损检测数值模拟中的重点问题——磁性材料内部磁场分布的数值模拟方法。以麦克斯韦方程组为理论基础,基于等效磁极化法开发了铁磁材料内部的磁化强度计算方法和程序。数值模拟中采用有限元-边界元混合方法,并采用等效电流模型计算永磁体磁场分布,以实现铁磁性材料内部三维静态磁场数值模拟。通过对数值模拟结果的分析及与ANSYS计算结果进行比对,验证了方法的有效性。     

Electrodeposition of CoMoP thin film as diffusion barrier layer for ULSI applications

CoMoP thin films were fabricated by electrodeposition technique from citrate based bath onto Cu sheets for the application as diffusion barriers and metal capping layers in the copper interconnect technology. The study focused on the effect of (NH₄)₆Mo₇O₂₄·4H₂O concentrations in the plating solution on the plating rate and chemical composition of the deposited layer. It was found that the Mo wt.% in the deposited layer increased from 13 to 22 wt.% with increasing (NH₄)₆Mo₇O₂₄·4H₂O concentration. The influence of deposition current density, solution pH and deposition temperature at certain (NH₄)₆Mo₇O₂₄·4H₂O concentration in the plating bath on the plating rate and chemical composition was studied. Polarization behavior of induced co-deposition of CoMoP at various electrolyte pH values was studied using cyclic voltammetry and chronoamperometry to estimate the current efficiency (CE%) of the plating solutions and the optimum pH for the plating process. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques have been applied to characterize the morphology and chemical composition of the deposited layer. CoMoP alloys of high P wt.% as-deposited films showed irregular microcracks amorphous structure and of low P wt.% showed amorphous/nanocrystalline structure while, after annealing at 400 °C for 1 h, the films deposited with low and high P wt.% converted into polycrystalline structure. The results of oxidation property showed that, the Co-13.2 wt.% Mo-10.3 wt.% P alloy has highest stability against oxidation and lowest electrical resistance values (100-150 µΩ). The ferromagnetism nature of coated materials has been studied by hysteresis loop measurements. The electrochemical corrosion results were calculated from polarization studies for as-plated and annealed CoMoP coatings in 3.5% NaCl solution.     

Pulsed eddy current testing of ferromagnetic specimen based on variable pulse width excitation

Pulsed eddy current testing (PECT) is a rapidly developing technology which has wide potential applications. For the PECT system which uses detection coils, a no-reference-needed and more efficient method, for quantifying the wall thickness of the ferromagnetic specimen, should be found. In this paper, a kind of variable pulse width excitation is proposed. Based on the excitation, the slope that the relative increment of magnetic flux linear decays with the increase of pulse width in the semi-logarithmic domain is found to be an effective and no-reference-needed feature. First, the analytical expression for the relative increment of magnetic flux is presented, and the validity of the feature is verified by experiments. Then the potential factors affecting the feature are investigated in detail. Results show that when the electromagnetic properties of the specimen are invariant, the feature is independent of pulse width parameters, analysis interval and coatings thickness. At last, a quantitative method is demonstrated. More time could be saved for the narrow pulse comparing it with the existing excitations, and the feature could widely meet engineering applications.     

钢轨纵向应力和巴克豪森效应的关系

铁磁材料在磁化场作用下磁畴的不可逆运动产生巴克豪森效应，此效应依赖于材料的显微组织和应力状态，可做为无损检测铁磁材料内应力的一种新方法，本文从实用性出发探讨了钢轨材料的巴克豪森特征及钢轨纵向应力和巴克豪森效应的关系，做为检测钢轨温度纵向应力的实验基础。     

Microstructure and soft-magnetic properties of FeCoPCCu nanocrystalline alloys

Fe_83.2-xCo_xP₁₀C₆Cu_0.8 (x = 0, 4, 6, 8 and 10) alloys with a high amorphous-forming ability and good soft-magnetic properties were successfully synthesized. Saturation magnetic flux density (B_s) is effectively enhanced from 1.53 T to 1.61 T for as-quenched alloy by minor Co addition, which is consistent well with the result of the linear relationship between average magnetic moment and magnetic valence. For Co-contained alloys, the value of corecivity (H_c) is mainly determined by magneto-crystalline anisotropy, while effective permeability (μ_e) is dominated by grain size and average saturation polarization. After proper heat treatment, the Fe_79.2Co₄P₁₀C₆Cu_0.8 nanocrystalline alloy exhibited excellent soft-magnetic properties including a high B_s of 1.8 T, a low H_c of 6.6 A/m and a high μ_e of 15,510, which is closely related to the high volume fraction of α-(Fe, Co) grains and refined uniform nanocrystalline microstructure.     

受扭轴类零件磁记忆信号的初步研究

金属磁记忆检测技术是通过测试构件在外载荷作用过程中形成的表面微弱磁场的变化来监测其损伤状态的。利用该技术，研究了受扭磁性轴类构件的磁记忆检测信号特征，并探讨了磁场环境对构件在扭矩作用下磁记忆信号的影响。结果表明，磁记忆检测信号与构件的损伤状态之间具有明显的相关性，磁场环境对改善金属磁记忆检测效果具有较好的作用。     

在应用JSZBF型抗铁磁谐振电压互感器中需注意的问题

对抗铁磁谐振电压互感器接线原理和使用中容易出现的问题进行了介绍和分析,并针对其安装和验收投运提出了需注意的要点和测试方法.     

一起电压互感器爆炸事故的原因及其防范措施

本文就一起10KV电压互感器爆炸事故,从理论上分析了事故原因--谐振过电压,并结合农村35KV变电所实际提出几条防范措施.