高质量2英寸双面YBCO/MgO薄膜的批量化制备

开展了2英寸(5.08cm)MgO单晶基片上YBa2Cu3O7-δ(YBCO)薄膜的制备及工艺稳定性研究。通过对基片表面状态的研究,提出了高温退火处理基片的方法,改善了基片的表平整度,大幅度提高了薄膜的取向性以及结晶质量,制备得到的YBCO薄膜具有优越的超导电性,薄膜临界电流密度J(c77K,0T)≈2.5MA/cm2,微波表面电阻R(s10GHz,77K)≈0.16mΩ,能够满足超导滤波器的设计要求。另外,还就工艺的稳定性和可重复性进行了研究,表明电子科技大学已具有小批量化提供大面积双面YBCO样品的能力。     

不同厚度Tl-2212薄膜的表面形貌及超导特性研究

采用直流磁控溅射法和后退火技术在蓝宝石基片上制备了Tl-2212超导薄膜,考察了Tl-2212薄膜的厚度对其形貌和超导特性的影响。实验结果表明,随着超导薄膜厚度增加,其表面形貌由致密平整的结构演化为片状晶体结构,临界转变温度Tc和临界电流密度Jc先增大后减小,微波表面电阻Rs先减小后增大。在退火的CeO2缓冲层上所制备的无裂纹薄膜的最大厚度达到600nm,并仍然具有良好的超导性能。     

超导材料及其在舰船上的应用

<正> 从1986年起高温超导研究取得重大突破,美、中、日及前苏联的科学家相继发现一系列的氧化物高温超导体,最高的转变温度达到90～100K。另一方面,超导材料的加工制作技术也取得显著的进展,超导线材和用超导薄膜制作的器件已开始商品化。超导     

超导目前已经进入产业化阶段

超导目前已经进入产业化阶段。高温超导材料和低温超导材料应用领域并不一致,我们预计高温超导中超导限流器、超导滤波、超导储能将有可能最先获得应用。低温超导主要用于核磁共振(MRI)和可控核聚变磁场线圈(ITER),技术成熟,市场较小。     

美国能源部公布小企业创新研究项目

美国能源部公布了 2 0 0 2财政年度第 2阶段小企业创新研究项目和基金。●高温超导体制造工艺X 射线诊断项目 ,ARACOR公司 ,金额为 75万美元。如果缺乏合适的诊断工具 ,不能在生产过程中快速测量最终产品的电性能 ,势必使高温超导体的实际制造工艺开发进展缓慢。这项课题将开发快速在线检测薄膜成分和晶体织构的X 射线诊断方法。在第 1阶段 ,已成功论证了可快速测量超导薄膜织构参数的衍射方法。此外 ,根据对样品进行的X 射线荧光研究 ,提出另外 2种可以高灵敏测量元素成分的方法。在第 2阶段中 ,原型衍射荧光仪将在产业化生产高温超导…     

高温超导限流器对材料的要求

随电网能力的增加,发展故障限流器是紧迫的任务。超导故障限流器(SFCL)的设计可以根据不同概念,但设计和应用具体需解决一系列的材料问题。用在母线耦合馈线位置、直接的电阻型限流器,可用简单、实际的方法,就用目前水平的高温超导线材来做。高温超导故障限流器(HTSFCL)既...     

钇钡铜氧超导厚膜的研究进展

YBa2Cu3O7-x(YBCO)涂层导体(也称第二代高温超导带材)在77 K下具有较高的不可逆场和本征载流能力,在强电领域有着广泛的应用。第2代高温超导带材是基于薄膜外延技术发展起来的实用超导材料,为使其尽快商业化,科学家们一直在不断探索研究YBCO的基础物性和成材机理。如何制备具有高临界电流密度的厚膜就成为当前YBCO高温超导涂层应用过程中亟待解决的关键问题。介绍了厚膜与临界电流之间的关系并综述了国际主流研究机构对YBCO厚膜的最新研究进展情况。     

不断前进中的西北有色金属研究院超导材料研究所

超导技术被认为是21世纪具有战略意义的高新技术，在能源、信息、交通、科学仪器、国防、重大科学工程等方面将具有重要应用。目前，实用超导材料主要有NbTi，Nb3Sn低温超导材料和Bi系、Y系高温超导材料。第2代Y系高温超导涂层导体和2001年发现的MgB2超导材料近年来展现了更为诱人的潜在应用价值。     

实用高温超导体进展

自从高温超导体出现以来，已发现好几族超导化合物（化合物总数超过100个）．在这些化合物当中，YBa2Cu3o7，（Y－123）和Bi2Sr2Ca2Cu3O10体材的应用仍是最有希望的．自从这些化合物发现之后，几种具有真正工业应用前景的体材和薄膜的应用已开始显山露水．例如，以沙波器形式应用于微波通讯的薄膜超导体已经商业化，而体村应用则由于面临许多的技术挑战尚未达到市场化阶段．此外，还出现了几个成功的高温超导传输电缆承范模型．目前，高质量的铋基高温超导线可从若干个卖主那里买到．然而，Y－123线材的进展已开始减缓，但其发展稳定，…     

在蓝宝石基片上制备高质量的Tl-2212超导薄膜

在蓝宝石衬底上生长高质量Tl-2212薄膜的制备方法。在最佳退火条件下,对蓝宝石(1102)基片和CeO2缓冲层进行高温热处理,所生长500nm厚的Tl-2212薄膜具有优良的面内和面外取向,薄膜的超导电性得到大幅度提高,其临界转变温度(Tc)达到107.5K,在液氮温度下,临界电流密度为(Jc)3.6MA/cm2,微波表面电阻Rs(77K,10GHz)约为263μΩ。     

高温微波冶金反应器的研究现状及发展趋势

在简述微波加热基本原理的基础上,评述高温微波冶金反应器近年来的国内外研究现状,分析目前高温微波冶金反应器存在的主要问题,指出由于高温条件下微波系统的连续稳定性、适用于微波场的大尺寸高温反应内腔及高效的反应工程设计等难题,除小规模微波设备外,能够满足高温、高效、大功率的微波冶金反应器仍是空白,解决高温微波冶金反应器工业化应用在微波高温陶瓷材料、大功率微波发生器和物料温度测试等方面存在的主要问题,提高微波能的转换效率,研制、设计连续、稳定的大功率高温微波冶金反应器是微波工业化实践的关键。     

In situ SR-CT Experimental Study on the Directional Sintering of High-Temperature Superconductor YBCO Materials in the Microwave Fields

YBa₂Cu₃O_7-x (YBCO) is a kind of high-temperature superconducting material that has important application in information, energy, medical treatment, etc., and the superconducting properties of YBCO are closely related to its internal microstructure. In this study, the microwave heating method was adopted to prepare the YBCO materials. The internal 3D online evolution observation based on the synchrotron radiation computed tomography technology shows that there was directional grain growth phenomenon of YBCO during microwave sintering process. In local regions with special microstructure, these particles grew to the same point. Here, the theoretical models of single and multiple particles in the microwave electromagnetic fields were established. Based on these theoretical models and finite element analysis, it shows that the YBCO particles can modulate the distribution of electromagnetic fields, resulting in the significantly higher electric field intensity at the particle junctions than other regions. Moreover, there were very high electric field intensity and temperature gradients in the directions of particle growth. These factors were crucial in directional sintering. These results will provide theoretical basis and technical guidance for the controllable preparation and performance optimization of the internal microstructure of superconducting materials in the preparation process.     

Magnetic and microwave properties of glass-coated amorphous ferromagnetic microwires

Glass-coated amorphous FeCuNbSiB microwires were prepared by Taylor-Ulitovsky technique. X-ray diffractometry and scanning electron microscopy were used to investigate the microstructure and morphology of the glass-coated microwires respectively. The vibrating sample magnetometer and vector network analyzer were used to study the magnetostatic and microwave properties of glass-coated microwires. The experimental results show that the effective anisotropy of an array of 150 microwires of 10 mm in length is large than that of one microwire of 10 mm in diameter and an array of 150 microwires of 1 mm in diameter. The natural ferromagnetic resonance takes place as the microwave magnetic component is perpendicular to the microwires axis, and the electric dipole resonance takes place as the microwire is long or the short microwire concentration is moderate. The natural ferromagnetic resonance shifts to higher frequency with the larger microwire concentration. The electric dipole resonance is governed by the microwires length and concentration. The glass-coated FeCuNbSiB microwires can be used to design EMI filters and microwave absorbing materials.     

Mechanical properties of plasma-deposited silicon-based inhomogeneous optical coatings

Amorphous hydrogenated silicon nitride, oxide and oxynitride films are deposited by plasma-enhanced chemical vapour deposition (PECVD) using a dual-mode microwave/radio-frequency (MW/RF) plasma system. Optical filters are prepared by varying the film composition either abruptly (discrete, homogeneous multilayer structure) or continuously (graded-index, inhomogeneous structure). The coatings are characterised both optically, by spectrophotometry and spectroscopic ellipsometry, and mechanically, with depth-sensing indentation and low-load microscratch testing. A comparison is made between the properties of the homogeneous multilayer and the inhomogeneous multilayer structure with the corresponding optical performance. This multiple technique approach for characterisation was proved to be efficient for analysis of the optical and mechanical behaviour of coatings, and it provides a possibility for optimising the deposition process. It is demonstrated that the graded system exhibits a higher mechanical strength and a better toughness than the discrete structure.     

无缝钢管和电焊钢管的使用领域

详细介绍了无缝钢管和电焊钢管在机械、汽车、建筑、锅炉、石油天然气输送管线及石油钻采等方面的使用情况。     

Effect of heating mode on sintering of ferrous compacts through powder metallurgy route

Abstract

Microwave heating is recognised for its various advantages, such as time and energy saving, very rapid heating rates, considerably reduced processing cycle time and temperature, fine microstructures and improved properties. The present paper focuses on preliminary work carried out with the use of microwave radiation applied to sintering of ferrous compacts. The ferrous alloy compacts were sintered in a multimode microwave furnace of 2·45 GHz and 6 kW nominal power at 1120°C for 60 min in forming gas. Results of densification, mechanical properties and microstructural evaluation of the microwave sintered samples are reported and compared with conventionally sintered ones. In general, it is observed that the microwave radiation generally enhances the properties of the sintered material when compared with conventionally sintered material.     

Optimized microwave excitation probe for general application in NDT of wall thinning in metal pipes of arbitrary diameter

Generalized approaches to developing a microwave NDT for flaws inside an arbitrary diameter pipe through optimizing a microwave-exciting probe were investigated. A microwave probe obtained from a parameter-optimizing scheme based on transmission characteristics is proposed. Three-dimensional finite element simulation of five microwave probes indicates that a larger optimization parameter enables reduced microwave reflection, as well as improved single-mode propagation inside the pipe as compared with conventional probes. Experimental verification, using straight brass pipes of various diameters confirmed that the optimized microwave probe exhibits a larger signal-to-noise ratio for internal flaws when compared with conventional probes, thereby validating the new optimization parameter.     

Experimental and theoretical investigation on microwave melting of metals

Experiments were conducted for microwave heating and melting of lead, tin, aluminium and copper with the aid of susceptors and the detailed results were presented for various microwave power levels and sample loading. Aluminium and copper samples were heated in presence of inert gas to minimize oxidation. Compared to conventional melting, microwave melting was twice as fast and more energy efficient. Lumped parameter model of the heating process showed that the conversion of microwave to thermal energy was enhanced at higher temperatures, justifying this a favourable process for metal melting applications.     

A review of helical carbon materials structure,synthesis and applications

The helical structures possess unique physical and chemical properties,such as superelasticity,high specific strength,chirality,and electromagnetic cross-polarization characteristics.With the development of nanoscience and nanotechnology,helical structures with various scales have been discovered or synthesized artificially.Among them,the helical carbon materials receive much attention around the world.Herein,we present a brief review of the development of helical carbon materials in terms of structures,synthesis techniques and mechanisms,and applications.The controllable designing of catalysts,carbon sources and reaction parameters plays a key role to optimize the properties of the helical carbon materials.At the same time,the applications in microwave absorption devices,sensors,catalysts,energy conversions and storage devices,and solar cell are also presented.For the good chemical and physical properties,helical carbon materials have a good application prospect in many fields.The potential issues and future opportunities of the helical carbon materials are also proposed.     

准一维铁镍合金材料的制备研究进展及应用展望

综述准一维铁镍合金材料(纳米棒、纳米线、纳米管、纳米纤维、纳米须)的各种制备方法和应用现状,主要介绍模板法、磁场引导羰基热分解法、还原法、微波等离子体法、溶胶-凝胶-热分解还原法、配位共沉淀-热分解法等,比较了各种制备方法的优缺点,介绍了其在相关领域的应用现状,最后展望其制备和应用的发展趋势。