The influence of FeNi nanoparticles on the microstructures and soft magnetic properties of FeSi soft magnetic composites

In this work, a new type of FeSi/FeNi soft magnetic powder core (SMPC) was successfully fabricated by coating FeNi nanoparticles on the surface of FeSi micrometer powder. The effects of different contents of FeNi nanoparticles on the micromorphology, internal structures, and soft magnetic properties of SMPCs were studied. The results show that FeNi nanoparticles adhere to the surface of FeSi powder, which can effectively fill the air gap between FeSi powder and is beneficial to the compaction of the powder cores during the pressing process. Thus, the density of the SMPCs is increased. Compared to FeSi SMPCs, the comprehensive soft magnetic properties of FeSi/FeNi SMPCs have been greatly improved. When adding 15 wt% FeNi nanoparticles, the SMPCs exhibit excellent magnetic properties with high effective permeability (increased by 43.8 %) and low core loss (decreased by 22.1 %). The high performance FeSi/FeNi SMPCs prepared in this work are expected to be widely used in power choke coils, uninterruptible power supplies, and boosts and inverter inductors.     

铜粉粒径对机械镀Cu-Zn镀层性能的影响

为获得更好的防护+装饰双重效果,采用不同粒径(200,400,800,1 000,1 200目)的铜金粉,利用机械镀技术在钢铁基体表面制备了铜-锌复合镀层。采用称重法分析了镀层的致密度,采用贴滤纸法检验了镀层孔隙率,采用划线划格法分析了镀层的结合强度,采用全浸腐蚀法及电化学极化法分析了镀层的耐腐蚀性能。结果表明:不同粒径铜金粉制备的镀层均覆盖完整,随铜粉粒径减小,复合镀层孔隙分布减少;随着铜粉粒径的减小,镀层的致密度逐渐增加,当铜粉粒径为1 000目时,Cu-Zn镀层的致密度已大于金属锌的密度;随着铜粉粒径的减小,镀层的结合强度增加,当铜粉粒径为200目时镀层的结合强度较差,而铜粉粒径小于400目时镀层的结合强度明显提高;随着铜粉粒径的减小,镀层的全浸腐蚀速率逐渐减小,耐腐蚀性增强。     

Magnetic properties and loss separation mechanism of FeSi soft magnetic composites with in situ NiZn-ferrite coating

Journal of Materials Science: Materials in Electronics - The soft magnetic performances including frequency-dependent permeability, core loss, and DC-bias properties of the Fe-6.5 wt.%Si (FeSi)...     

Effect of magnetic properties in FeSi soft magnetic composites by low melting glass powder as adhesive and insulating agent

Journal of Materials Science: Materials in Electronics - FeSi/1wt% glass soft magnetic composites are prepared by mechanically mixing, compacting, and annealing, their morphology is examined by...     

Tribological behavior of sintered electrolytic iron-zinc stearate added compacts

Powder metallurgy is an effective method to give near net shape to powder particles. In this paper, the influence of powder particle size, lubricant and compaction load on hardness and wear loss has been investigated as it influences the compact. Electrolytic iron powder (250 mesh to 300 mesh and 300 mesh to 350 mesh) with zinc stearate (0 weight % to 2 weight %) was used for preparing the samples. Green samples were prepared by cold compaction process at different loads (400 kN, 450 kN and 500 kN). Pre-sintering was done at 550 °C. Taguchi′s (L₁₈) mixed level model was used to develop the regression equation for hardness and wear loss. The maximum hardness of 79 HRB was achieved with 300 mesh to 350 mesh particle size and 500 kN compaction load. Minimum wear volume loss was observed with samples having composition of 250 mesh to 300 mesh size electrolytic iron powder at 500 kN compaction load and 1 weight % lubricant content.     

Laser-induced reaction of Si powder with a steel substrate

We have determined the phase composition and microhardness of coatings produced by the laser melting of silicon powder on the surface of steel substrates. Laser exposure leads to the formation of iron silicides on the substrate surface. The iron content of the silicides depends on the effective laser power and increases from that of FeSi₂ to Fe_0.9Si_0.1. The coatings have the highest microhardness at an effective power of ≏ 400 W s/m, which corresponds to the highest FeSi content.     

球磨时间对FeSi合金吸波性能的影响

采用湿法球磨对FeSi合金粉末进行片状化改性,利用扫描电子显微镜(SEM)、激光粒度分析仪、矢量网络分析仪对改性前后的FeSi粉末进行测试分析,研究不同球磨时间对FeSi粉末的形貌、粒径、电磁参数、吸波性能的影响。结果表明,随着球磨时间的延长,FeSi粉末的粒径逐渐减小,且扁平化程度增加。模拟反射率结果表明,当球磨时间为8h时,材料在测试频段内吸收值低于-15dB的频宽为2.8GHz,且在10.5GHz处达到最低吸收峰值-28.3dB。     

Characteristics and Microstructure of a Hypereutectic Al-Si Alloy Powder by Ultrasonic Gas Atomization Process

［1］J.L.Estrada and J.Duszczyk: J. Mater. Sci., 1990, 25,886. ［2］Daoyun DING, Zhangming SUN and Zhenhua CHEN: J. Central South Uni. of Technol., 1995, 26, 92. (in Chinese)     

Plasma deposition and Auger studies of carbon impurities in zinc oxide

Journal of Materials Science - A low pressure radio-frequency discharge in methane or a methane-oxygen mixture is used to deposit carbon species on the surface of compacted ZnO powder at 400°...     

Experimental Investigation on Selective Laser Melting of Bulk Net-Shape Pure Magnesium

In this study, bulk net-shape pure magnesium was fabricated by selective laser melting (SLM). Effects of Mg particle size and processing parameters on the properties of SLM specimens were investigated. The scan speed and laser power were optimized based on macro-observation of the forming process and resulted specimens. Through the comparison analysis of topology, density, and micro-hardness, it was found that the bulk magnesium specimen made of ?250 mesh powder showed better results than that made of ?400 mesh powder. The relative densities of both SLM specimens were over 95%, and their micro-hardness values were higher than that of as-cast magnesium. It was also revealed that the scanning time interval (STI), as a relatively new processing parameter, had an obvious effect on the properties of SLM bulk magnesium in terms of surface morphology, roughness, and micro-hardness.     

Fe/Fe_(73.5)Cu_1Nb_3Si_(13.5)B_9纳米晶磁粉芯研究

采用Fe粉复合FeCuNbSiB纳米晶粉体制备了磁粉芯,并讨论了退火温度、Fe粉复合量、纳米晶粉体粒度以及绝缘剂等对磁粉芯磁性能的影响.结果表明,在200～350℃和350～400℃内退火,随着温度的升高,μ_e均呈先增大后减小,375℃时达到最佳;当复合Fe粉后,发现其软磁性能得到了明显改善, Fe粉量为40%时,μ_e达到最大,且在100kHz～1MHz内,频率稳定性良好,其中心频率在500kHz附近,并随Fe粉量的增加而向低频发生偏移.纳米晶粉体的粒度越大,磁粉芯的磁性能越好;粉体粒度为100～200目时,其μ_e达到最大.当375℃退火,由有机绝缘剂、40%(质量分数)Fe粉、100～200目纳米晶粉制备的磁粉芯,其μ_e达52.72、损耗Pu为0.01317J/m~3、Bs为3.92×10~(-3)T、Br=6.48×10~(-5)T、H_c为1.28A/m.     

A comprehensive study of soft magnetic materials based on FeSi spheres and polymeric resin modified by silica nanorods

A novel soft magnetic composite (SMC) based on spherical FeSi particles precisely covered by hybrid phenolic resin was designed. The hybrid resin including silica nano-rods chemically incorporated into the phenolic polymer matrix was prepared by the modified sol–gel method. A chemical bridge connecting silica nano-rods with the base polymeric net was verified by FTIR, ¹³C and ²⁹Si NMR spectroscopy, whereas the shape and size of silica nano-rods were determined by TEM. It is shown that the modification of polymeric resin by silica nano-rods generally leads to the improved thermal and mechanical properties of the final samples. The hybrid resin serves as a perfect insulating coating deposited on FeSi particles and the core–shell particles can be further compacted by standard powder metallurgy methods in order to prepare final samples for mechanical, electric and magnetic testing. SEM images evidence negligible porosity, uniform distribution of the hybrid resin around FeSi particles, as well as, dimensional shape stability of the final samples after thermal treatment. The hardness, flexural strength and density of the final samples are comparable to the sintered SMCs, but they simultaneously exhibit much higher specific resistivity along with only slightly lower coercivity and permeability.     

Alloy selection for in mould inoculation to control chill width in ductile iron

Abstract

The relative performance of six FeSi based inoculants was tested for of ductile iron chill width control using in the mould inoculation after FeSiCaMgRE treatment. In the prevailing solidification conditions (W₃ chill wedge, ASTM A367-85, resin sand mould), Sr–FeSi alloys did not perform well, but had a 15–30% benefit from preconditioning with Al,Zr,Ca–FeSi. Ba,Ca–FeSi alloy had the lowest efficiency, without any benefit from preconditioning. The best inoculant performance is achieved using a complex inoculant chemistry (Ca,RE,S,O–FeSi), while the Ca,Zr–FeSi alloy was the second rated inoculant, with important benefits from preconditioning in both cases. Al,Zr,Ca–FeSi preconditioning of the base iron before Ca–FeSi inoculation showed better performance than an inoculation only treatment using the same active elements (Ca,Zr,Al–FeSi alloy).     

Beneficiation and upgrading of coarse sized low-grade bauxite using a dry-based fluidized bed separator

Beneficiation and upgrading of low-grade bauxite is important to the subsequent extraction of Aluminum metal using Bayer process. The mineralogical characterization of diaspore bauxite sample used in this work was performed using various analysis approaches. The results indicated that the major components of raw sample were diaspore and kaolinite. The bauxite samples had high Al₂O₃ contents with low Al/Si ratios. A dry-based fluidized bed separator with FeSi powder as dense medium was used to beneficiate coarse sized bauxite. The basic fluidization tests suggested that −0.18 + 0.125 mm FeSi powder was appropriate for the fluidization stability, thus utilized as the dense medium for separation. The beneficiation experiments of various sized bauxite samples were investigated under various operational factors of separating time, static bed heights, and operational gas velocities. The upgrading performance of coarse sized bauxite indicated that the satisfied grade of concentrate could be obtained with a reasonable recovery of concentrate. Al/Si ratios were improved to 3.19, 4.53, and 3.66 for the bauxite samples with size fractions of −13 + 6 mm, −18 + 13 mm, and −25 + 18 mm, respectively. This work provided an alternative efficient method for the pretreatment of low-grade bauxite via discharging coarse waste gangue.     

三七超微粉体与细粉、不同目数范围粉体的粒度分布和显微形貌特征的比较

通过比较三七超微粉体、细粉(三七常规饮片)以及不同目数范围粉体(三七细粉经多次筛分得到的粉体)在粒度分布、显微形貌特征方面的差异,探讨了超微粉碎技术应用于中药三七加工的优势。应用激光粒度分析仪对三七超微粉体与细粉、不同目数范围粉体的粒度及其分布进行表征,观察其显微形貌特征。粒度分布测试和显微形貌观察的结果表明,超微粉粒度分布在0.30～24μm,大部分粉体达到了10μm以下,呈对称的单峰分布,引起团聚的作用力为各种表面力,说明超微粉体均匀度高质量易控。三七细粉及不同目数范围的粉体粒度分布范围在2～190μm,分布不对称,引起团聚的作用力为重力的等质量力,说明其均匀度差,质量难以控制。     

粉末挤出成型法制备FeSiAl/FeCuNbSiB磁粉芯

采用粉末挤出成型法制备了FeSiAl/Fe-CuNbSiB纳米晶磁粉芯,并讨论了FeSiAl粉复合量、粉胶质量比对磁粉芯磁性能的影响。结果表明粘结剂配方为硬脂酸1%、聚丙烯20%、石蜡79%,挤出成型粉胶质量比10∶1的FeSiAl/FeCuNbSiB纳米晶磁粉芯,磁粉芯密度达到4.69g/cm3。200目FeSiAl粉与300目FeCuNbSiB纳米晶粉复合,当磁粉芯磁粉质量配比为"200目FeSiAl粉30%+300目FeCuNbSiB纳米晶粉70%"、粉胶质量比为10∶1、44℃×0.5h石油醚脱脂、热处理温度160℃×1h时,磁粉芯取得最佳的软磁性能,磁粉芯中心频率f为600kHz,有效磁导率μe达到16.48,品质因数Q值为57.5;频率及温度的变化对磁粉芯的有效磁导率的影响小。     

锌粉特性对机械镀锌层性能的影响

通过OLYMPUS-GX51型光学显微镜进行机械镀层金相组织检测和厚度测量、划线和划格试验及按GB/T 3091-2001 要求的硫酸铜溶液腐蚀试验,研究了锌粉粒度及形状对机械镀锌层性能的影响.试验表明:在相同机械镀锌工艺规范下,320目颗粒状锌粉镀层颗粒粗大且不均匀,厚度范围33～55 mm,500目颗粒状锌粉镀层不及500目片状锌粉镀层致密,厚度范围45～58 mm,500目片状锌粉镀层最致密颗粒分布也最均匀,厚度范围33～41 mm; 320目颗粒状锌粉、500目颗粒状锌粉、500目片状锌粉机械镀锌层与钢铁基体之间附着强度均达到有关国家标准;均匀性均达到GB/T 3091-2001要求;锌粉粒度越小对应其镀层耐蚀性及均匀性也越好;在相同粒度尺寸下(500目锌粉),片状锌粉比粒状锌粉的镀层具有更好的耐腐性.     

聚氯乙烯/杨木粉模压发泡材料的制备及性能研究

目的制备聚氯乙烯杨木粉发泡材料并研究其性能。方法采用模压法制备发泡材料,利用压缩试验表征其性能。结果随着杨木粉填充量的增加,聚氯乙烯杨木粉发泡材料的密度呈上升趋势。添加木粉后,压缩强度呈先升高后下降的趋势,当木粉填量为10份时,压缩强度达到最大。随着木粉粒度的增加,聚氯乙烯木粉发泡材料压缩强度也呈先上升后下降的趋势,在木粉粒度为100目时压缩强度达到最大。结论可采用模压法制备聚氯乙烯杨木粉发泡材料,发泡剂用量、木粉填量和粒度对发泡材料性能有一定影响。     

Synthesis and properties of single-crystal FeSi nanowires

We report for the first time the chemical synthesis of free-standing single-crystal nanowires (NWs) of FeSi, the only transition-metal Kondo insulator and the host structure for ferromagnetic semiconductor Fe(x)Co(1-x)Si. Straight and smooth FeSi nanowires are produced on silicon substrates covered with a thin layer of silicon oxide through the decomposition of the single-source organometallic precursor trans-Fe(SiCl3)2(CO)4 in a simple chemical vapor deposition process. Unlike typical vapor-liquid-solid (VLS) NW growth, FeSi NWs form without the addition of metal catalysts, have no catalyst tips, and depend strongly on the surface employed. X-ray spectroscopy verifies the identity and the room-temperature metallic nature of FeSi NWs. Room-temperature electrical transport measurements using NW devices show an average resistivity of 210 micro Omega cm, similar to the value for bulk FeSi. Investigations into the low-temperature physical properties of the first one-dimensional Kondo insulator and the possible new NW growth mechanism are underway. This unique synthetic approach to FeSi NWs will be generally applicable to many other transition-metal silicides.     

Effect of Ni and TiO2 particle addition on the wettability and interfacial reaction of Sn20Bi lead-free solder

Journal of Materials Science: Materials in Electronics - In this paper, the powder samples are mechanically ball-milled by powder metallurgy, cold pressed and shaped, then melted, and finally, the...