NbTi超导体的新进展：（Ⅰ）常规NbTi超导体

ＮｂＴｉ超导体由于具有良好的机械、加工性能和超导性能，因此已得到了广泛应用。临界电流密度Ｊｃ是超导体应用过程中最主要的技术指标之一，因此提高ＮｂＴｉ超导体的临界电流密度Ｊｃ一直是ＮｂＴｉ超导体研究的热点。理论研究表明 ［１］，ＮｂＴｉ超导体的去偶电流密度极限约为１０~９Ａ／ｃｍ~２（５Ｔ，４．２Ｋ），然而目前实用ＮｂＴｉ超导线的Ｊｃ仅为３×１０~５Ａ／ｃｍ~２（５Ｔ，４．２Ｋ）。通过将ＮｂＴｉ超导体制成带材及多层薄膜导体，其Ｊｃ可达到这一理论极限的 ５％～ ２０％［２，３］。因此 ＮｂＴｉ超导体的研究主…     

高温超导体研究新发现—MgB2

今年一月,日本科学家Ｎａｇａｗａｔｓｕ等人发现了二硼化镁超导体,引起国内外的普遍关注。这是一种新的简单二元金属间化合物超导体（每个晶胞只有三个原子）,超导转变温度Ｔｃ高达３９Ｋ,几乎是Ｎｂ２Ｇｅ（Ａ１５型金属间化合物超导体中Ｔｃ最高, ２３．２Ｋ）和ＹＰｄ２Ｂ２Ｃ（金属间硼碳化合物）的两倍。ＭｇＢ２超导体具有大的同位素效应,其超导机制基本满足ＢＣＳ理论。 最近几个小组报道了ＭｇＢ２的临界电流和磁性质,结果显示,ＭｇＢ２是各向同性的第二类超导体,其京茨堡一朗道参数ｋ＝２６～３８,相干长度ξ＝ ４．９…     

Bi—2223超导带的拉伸特性和芯丝断裂可能性

带状Ｂｉ－２２２３超导体有众多的用途,但条件是必须兼具高的临界电流密度和足够的强度．为此,日本东京大学和国立金属所等单位的研究者,采用类似弓形样品某装置,研究了Ｂｉ－２２２３超导带的机械性能． 实验是在粉末套管法制备的６１芯包银带上进行的,最终成形带子尺寸宽为３．４ｍｍ、厚０、２４ｍｍ,处理后带子的临界温度为１０８Ｋ．自场７７Ｋ下传输Ｊｃ为１８．５ｋＡ／ｃｍ２,应变试验样品长度７ｃｍ,在大口径磁体和不同温度（４．２Ｋ． ２０Ｋ和７７Ｋ）下试验．先用一般锡焊将Ｂｉ－２２２３超导带固定在Ｕ形黄铜弹簧架…     

AK4－2Ч耐热铝合金板材（1．0～2．5mm厚）的组织和性能

ＡＫ４—２Ч耐热铝合金是ＡＫ４—１Ч合金的改型．与后者相比，在成分上，ＡＫ４—２Ч的Ｆｅ、Ｎｉ含量有变化，并用Ｚｒ附加合金化；在性能上，ＡＫ４－２Ч的板材、型材和锻件有更高的抗断裂性．文献中关于ＡＫ４—２Ч板材性能的报道不多．对广泛用做构件的薄板进行断裂韧性和耐热性的评定是十分重要的，故对ＡＫ４—２Ч板材这方面的性能进行了测试．     

有无个磁场下铁在H2SO4＋K2Cr2O7溶液中的电化学状态和阴极化行为

在［Ｈ２ＳＯ４］为０．１－２ｍｏｌ／Ｌ、［Ｋ２Ｃｒ２Ｏ７］为０．０１＝０．４ｍｏｌ／Ｌ的范围内，研究了Ｆｅ／Ｈ２ＳＯ４＋Ｋ２Ｃｒ２Ｏ７系统的电化学状态和阴极极化行为，讨论了［Ｈ２ＳＯ４］、［Ｋ２Ｃｒ２Ｏ７］和［Ｈ２ＳＯ４］／［Ｋ２Ｃｒ２Ｏ７］比值与Ｆｅ的电化学状态的关系。分析了所出现的五种类型阴极极化曲线和外磁场对阴极过程的影响。     

盐类反应制备TiB2／Al—4.5Cu复合材料的研究

采用Ｋ２ＴｉＦ６和ＫＢＦ４混合盐反应法制备ＴｉＢ２／Ａｌ－４．５Ｃｕ复合材料，通过ＳＥＭ，ＸＲＤ及ＭＴＳ等仪器研究了复合材料的凝固组织和力学性能。增强相ＴｉＢ２颗粒细小（＜２μｍ），呈近球形，均匀分布于基体之中，起强化和细化基体作用，ＴｉＢ２颗粒与基体结合好。当Ｋ２ＴｉＦ６和ＫＢＦ４混合物加入质量为基体的２０％时，复合材料的综合性能最好。ＵＴＳ达３５２ＭＰａ，ＥＬ达４．４％，ＨＢ达１４６。     

C90油管钢的氢损伤

对比研究了三种油管钢（宝钢的Ｃ９０和日本的ＳＭ９０及ＳＭ９５）的氢致开裂性能．ＳＭ９０，ＳＭ９５和Ｃ９０产生氢损伤的临界扩散氢质量分数（×１０~（－６））分别为１．７６，４．３和８．３８；临界全氢质量分数（×１０~（－６））分别为４．２４，６．３５和１０．２２三种钢在Ｈ_２Ｓ中的门槛应力σ_（ｔｈ）／σ_ｓ分别为０．６４，０．８０和０．８５．三种油管钢抗氢损伤能力和抗氢致滞后断裂的能力是一致的，以Ｃ９０为最好，它和氢的扩散系数无关．Ｃ９０钢缺口试样氢致滞后断裂门槛值Ｋ_（ＩＨ）与可扩散的氢质量分数ｗ_０有关，实验获得Ｋ_（ＩＨ）＝４６－１２．５１ｌｎ_（ｗ０）．理论分析和实验结果完全一致．对Ｃ９０钢，当ｗ_０≤４．８×１０－６时，在任何Ｋ_Ｉ／Ｋ_Ｃ下均将获得韧窝断口；ｗ_０≥７．６×１０~（－６），Ｋ_Ｉ／Ｋ_Ｃ≥０．５时，则氢致韧断；Ｋ_Ｉ／Ｋ_Ｃ≤０．４时，则氢致脆断．     

用含KBH4碱液处理改善M1Ni3.7Co0.6Mn0.4Al0.3贮氢合金电极的动力学 …

研究了用６ｍｏｌ／Ｌ ＫＯＨ＋ｙ ｍｏｌ／Ｌ ＫＢＨ４（ｙ＝０．０,０．００５,０．０１,０．０２,０．０３）表面改性处理对Ｍ１Ｎｉ３．７ｃＯ０．６Ｍｎ０．４Ａｌ０．３贮氢合金电极动力学性能的影响。结果表明：用含ＫＢＨ４碱液处理合金粉末可有效地提高氢化物电极的高倍率放电能力ＨＲＤ,交换电流密度Ｉ０,极限电流密度ＩＬ和α相中氢的扩散系数Ｄα等各项动力学性能,而且ＫＢＨ４的浓度越高（≤０．０３ｍｏｌ／     

AK4—2Ч耐热铝合金板材（1.0—2.5mm厚）的组织和性能

ＡＫ４－２Ч耐热铝合金是ＡＫ４－１Ч合金的改型，与后者相比，在成分上，ＡＫ４－２Ч的Ｆｅ，Ｎｉ含量有变化，并用Ｚｒ附加合金化，在性能上，ＡＫ４－２Ч的板材，型材和锻件有更高的抗断裂性，文献中关于ＡＫ４－２Ч板材性能的报道不多，对广泛用做构件的薄板进行断裂韧性和耐热性的评定是十分重要的。故对ＡＫ４－２Ч板材这方面的性能进行了测试。     

新型热电材料β-Zn_4Sb_3的电学性能

采用真空熔炼和烧结的方法制备了新型热电材料尽β－Ｚｎ４Ｓｂ３。Ｘ射线衍射分析表明样品为单相。２种样品从室温到７２３Ｋ温度范围内的电学性能测量表明,β－Ｚｎ４Ｓｂ３在５００Ｋ～６５０Ｋ时具有较高的功率因子,真空熔炼样品的性能要优于烧结样品,其功率因子在 ６２３Ｋ时达到最大值 ３．９μＷ．ｃｍ－１．Ｋ－２。结果表明,β－Ｚｎ４Ｓｂ３在热电转换领域有潜在的应用前景。     

Effects of oxygen and carbon on the magnetic properties and microstructure of Sm2Co17 permanent magnets

The research on the sintered Sm2Co17 permanent magnets prepared by metal injection molding is still at the exploratory stage. Carbon and oxygen are two key factors that influence the magnetic properties. In this article, the effects of oxygen and carbon on the properties and microstructure of the magnets have been studied. The results indicate that oxygen consumes the effective Sm content of the magnets and forms Sm2O3-the non-magnetism phase, which result in the deterioration of the magnetic properties. Besides, the magnetic properties decrease in evidence with increasing carbon content. The main factor that affects the magnetic properties is the deterioration of the microstructure of the magnets. The Sm（Co, Cu）5 phase decreases, whereas the cell size increases with the increase of the carbon content. When the carbon content is above 0.43 wt.%, the Sm（Co, Cu）5 phase is not enough to form a uniform cellular microstructure. Thus the magnetic properties disappear. ZrC is detected in the magnets by XRD when the carbon content is above 0.21 wt.%. ZrC also reduces the properties of the magnets.     

Copper Corrosion Under Non-uniform Magnetic Field in 0.5 M Hydrochloric Acid

The influence of a magnetic field on the electrochemical reactions taking place at the surface of a copper electrode immersed in a 0.5 M HCl solution at room temperature has been studied. The symmetry axis of the magnetic field was lined up in the same direction of the ion flow to minimize the Lorentz forces. Measurements of potentiodynamic polarization curves, electrochemical impedance spectroscopy and electrochemical noise allow concluding that the magnetic field significantly affects the cathodic reactions, with corrosion rates increasing under the presence of oxygen in acid media and decreasing when oxygen is eliminated.     

氧气球罐缺陷的声发射和磁记忆在线综合检测

采用声发射、磁记忆检测技术与常规无损检测技术相结合的方法对400m^3氧气球罐进行在线检验,得到了400m^3氧气球罐典型案例的检测方案和检测数据。结果表明,采用声发射、磁记忆检测、联合超声和磁粉检测可以实现氧气罐的在线检测,磁记忆榆测技术可以检测到内部非超标缺陷影响形成的应力集中,声发射技术评价缺陷的活性,常规超声检测可能存在表面缺陷漏检的情况,声发射、磁记忆检测弥补了常规无损检测方法的不足。容器加压声发射检测中不活动缺陷和活动缺陷的磁记忆信号有明显差异。     

Numerical simulation of effects of cusp magnetic field on oxygen concentration of 300 mm CZ-Si

In magnetic Czochralski (MCZ) silicon growth,the distance and diameter of the electrified coils may affect the magnetic field intensity and melt flow.By changing the above parameters,the optimum geometric configuration of the coils was attempted.Through analyses of the oxygen concentration distribution o f the crystal/melt interface,axial and radial velocity distribution of melt and the magnetic field intensity in the melt,it is found that smaller diameter of coils contributes to reducing the needed current intensity and production costs.For a given current intensity,there is a best distance of coils when the oxygen concentration at crystal/melt interface reaches the lowest.     

Extraction and purification of magnetic nanoparticles from strain of Leptospirillum ferriphilum

1Introduction From1975,there is much interest in finding magne-totactic bacteria[1],because bacterial magnetosome particles,unlike those produced chemically,have a consistent shape,a unique crystallography,a narrow size distribution within the single magn…     

Extraction and purification of magnetic nanoparticles from strain of Leptospirillum ferriphilum

The magnetic nanoparticles were extracted from Leptospirillum ferriphilum, strain YSK, isolated from acid mine drainages by treatment with sodium dodecyl sulfate(SDS) and centrifugation through a sucrose density gradient. Transmission electron microscopy(TEM) indicates that the nanoparticles are approximately spherical with a mean diameter of 44 nm, and magnetite crystals in this size range are single magnetic domains. Energy-dispersive X-ray analysis shows that the nanoparticles primarily contain two kinds of elements, iron and oxygen. Thus it can be concluded that the magnetic particles are magnetosomes. Generally, it is thought that cellular magnetotaxis is a direct consequence of the cell possessing magnetosomes. The discovery of magnetosomes in strain YSK can provide the theoretical basis for screening efficient bioleaching bacteria which are specific to different magnetic minerals under an outer magnetic field.     

High-angle annular dark-field scanning transmission electron microscopy and electron energy-loss spectroscopy of nano-granular Co–Al–O alloys

Atomic structures of cobalt–aluminum–oxygen nano-granular films prepared by reactive rf-sputtering from CoAl alloys in oxygen gas were investigated by high-angle annular dark-field scanning transmission electron microscopy and electron energy-loss spectroscopy to clarify the atomic structures of the films and the interfacial layers in relation with their magnetic properties and tunnel magneto-resistance.     

旋转磁场净化钢液的实验研究

对旋转磁场净化钢液技术进行的实验研究表明，钢液在磁场下旋转速度的增加能加速夹杂物的向心迁移和聚合，但过高的转速将导致液面的卷流，降低分离效果。在同样的磁场强度下，不锈钢液由于粘度大，因而其转速比碳钢液的转速约低20％～30％。旋转磁场的施加使钢液中全氧含量迅速降低，在80～120r／min的转速下，碳钢可以获得约70％、不锈钢可以获得38％以上的全氧含量去除效率。     

海绵钛中铁的来源及降低途径

研究了烧结ＮｄＦｅＢ永磁材料的断裂行为及晶粒晶面和晶界界面的相成分。研究表明：ＮｄＦｅＢ磁体的断裂行为主要为沿晶断裂。晶界界面上富Ｏ和Ｎｄ元素，作者认为，晶界上存在的薄片状含氧富钕相是引起磁体沿晶断裂的主要原因，同时提出了几种提高ＮｄＦｅＢ永磁材料强韧性的途径。     

Investigation of nickel deposition onto section and central longitudinal surfaces of AA1370 aluminum electrical wire with and without a weak permanent magnetic field

In this work a special regard is given to the morphology of the nickel deposited layers, onto AA1370 aluminum section and central longitudinal surfaces, with and without a weak magnetic field oriented in parallel and perpendicular to the coated surface in modified Watt bath. The obtained results show the formation of honeycomb structure nickel deposits for samples treated with weak parallel oriented field under approximately 0.3 A/cm₂, and partial dendritic structure nickel deposit for samples treated with weak perpendicular oriented magnetic field, the perimeter deposits with and without magnetic field is different to the deposits in the remain surface. We attributed the defect of nickel deposits on the surfaces with and without magnetic field to the distribution of the intermetallics particles and we attributed the honeycomb structure to the escapement of hydrogen and oxygen.