Novel nano-composite bulk superconductors for high field engineering applications

用于高场工程应用的新型纳米复合体超导体

• 批准号: EP/H049657/1
• 负责人: David Cardwell
• 金额: $ 57.32万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FH049657%2F1
• 关键词: Novel; nano; composite; bulk; superconductors

Multi-specimen combinations of large, melt processed YBCO single grains of 25 mm diameter have been shown to trap stable magnetic fields as high as 17 T at 29 K in research-grade samples, which are simply not achievable in conventional iron-based permanent magnets (limited practically to less than ~ 1.5 T). Unfortunately, achieving and maintaining a bulk, superconducting device operating temperature of less than 65 K is difficult from a practical point of view and not particularly cost-effective. It is necessary, therefore, to develop materials with improved flux pinning (and hence field trapping) properties that can be fabricated economically for deployment in industrial applications based either on cryo-cooler technology, or on systems that use liquid nitrogen as a cryogen (boiling point, 77 K). Large single grains can be incorporated directly into existing sustainable engineering applications such as flywheels, magnetic bearings, permanent magnets for MRI/NMR, non-contact magnetic stirrers for high purity biological solutions and magnetic separators provided they can trap at least 2.0 T at 77 K. The closer the operating temperature to the transition temperature of the large single grain (typically ~ 90 K), however, the greater the requirement for effective artificial flux pinning centres in the large grain microstructure that prevent the motion of magnetic flux within the sample. The optimum size of such pinning centres is typically around a few nano-metres at 77 K. The most common method of introducing pinning centres into large YBCO grains involves engineering the size of Y2BaCuO5 (Y-211) phase inclusions in the bulk microstructure, which are produced as part of the Y-123 peritectic decomposition process during melt processing. The technique is limited fundamentally, however, by the tendency of Y-211 particles to ripen at elevated temperature, which conflicts directly with attempts to refine their size to the nano-scale. This results inevitably in a significant reduction in control of the melt process, and hence to limitations in sample performance. The PI has been involved in two important recent developments of the processing of large grain (RE)BCO superconductors. These are the development of a suitable non-211 phase that forms effective nano-scale artificial flux pinning centres, and in the development of an entirely new type of seed crystal that enables every member of the (RE)BCO class of materials to be grown in the form of large single grains by a practical techniques for the first time. The primary objective of this highly challenging project, therefore, is to fabricate mechanically stable, large, state of the art samples of single grain YBCO and other (RE)BCO melt processed superconductors than has been possible previously that contain novel (i.e. non Y-211-based), effective nano-scale artificial flux pinning centres by a practical processing technique. This will enable for the first time the cost-effective application of bulk superconductors in sustainable engineering devices that operate at, or around, 77 K. Additional objectives of this challenging proposal are to fabricate complex-shaped, new nano-phase composites for be-spoke applications for the first time using a novel multi-seeding technique, also underdevelopment at Cambridge by the PI, and to establish for the first time an effective recycling process for multi-grain samples. The project will involve extensive collaboration with four Cambridge science departments (Engineering, Materials Science, Physics and Chemistry) and with three international institutions (ATI Vienna, ICMAB Barcelona and the Boeing Company Seattle).

已经证明，直径为25 mm的大型熔融加工YBCO单颗粒的多试样组合在研究级样品中在29 K下捕获高达17 T的稳定磁场，这在传统的铁基永磁体中根本无法实现（实际上限于小于~ 1.5 T）。不幸的是，从实际的观点来看，实现和保持小于65 K的大体积超导装置操作温度是困难的，并且不是特别具有成本效益。因此，有必要开发具有改进的通量钉扎（和因此的场俘获）特性的材料，其可以经济地制造以用于基于低温冷却器技术或基于使用液氮作为致冷剂（沸点，77 K）的系统的工业应用中。大的单个颗粒可以直接结合到现有的可持续工程应用中，例如飞轮、磁性轴承、用于MRI/NMR的永磁体、用于高纯度生物溶液的非接触式磁性搅拌器和磁性分离器，只要它们可以在77 K下捕获至少2.0 T。然而，操作温度越接近大的单个晶粒的转变温度（通常为~ 90 K），对大晶粒微观结构中的有效人工磁通钉扎中心的要求就越高，所述有效人工磁通钉扎中心防止磁通量在样品内的运动。这种钉扎中心的最佳尺寸通常在77 K时约为几纳米。将钉扎中心引入到大的YBCO晶粒中的最常见的方法涉及在本体微观结构中设计Y2 BaCuO 5（Y-211）相夹杂物的尺寸，其作为熔融加工期间Y-123包埋物分解过程的一部分而产生。然而，该技术从根本上受到Y-211颗粒在高温下成熟的趋势的限制，这与将其尺寸细化到纳米级的尝试直接冲突。这不可避免地导致熔体过程控制的显著降低，并因此导致样品性能的限制。PI参与了大晶粒（RE）BCO超导体加工的两个重要的最新进展。这些是一种合适的非211相的发展，形成有效的纳米级人工磁通钉扎中心，并在一个全新类型的籽晶的发展，使每一个成员的（RE）BCO类的材料，以大的单一晶粒的形式生长的第一次通过实用技术。因此，这个极具挑战性的项目的主要目标是制造机械稳定的、大的、最先进的单晶粒YBCO和其他（RE）BCO熔融加工超导体的样品，而不是以前可能的样品，这些样品含有新颖的（即非Y-211基的）、有效的纳米级人工磁通钉扎中心，通过实用的加工技术。这将首次实现大块超导体在可持续工程设备中的成本效益应用，这些设备在77 K或77 K左右运行。这个具有挑战性的建议的其他目标是制造复杂的形状，新的纳米相复合材料的应用，第一次使用一种新的多晶种技术，也在剑桥的PI开发，并建立了第一次有效的回收过程中的多颗粒样品。该项目将涉及与四个剑桥科学系（工程、材料科学、物理和化学）和三个国际机构（ATI维也纳、ICMAB巴塞罗那和波音公司西雅图）的广泛合作。

项目成果

A trapped field of > 3T in bulk MgB_ fabricated by uniaxial hot pressing

单轴热压制备块状 MgB_ 中 > 3T 的俘获场

• 期刊: Superconductor Science and Technology
• 影响因子: 3.6
• 作者: David Cardwell (Author)

YBCO single grains seeded by 45° - 45° bridge-seeds of different length.

YBCO单粒种子采用45° - 45°不同长度的桥粒播种。

• 期刊: Superconductor Science and Technology
• 影响因子: 3.6
• 作者: David Cardwell (Author)

Properties of grain boundaries in bulk, melt processed YB2Cu3O7-_ fabricated using bridge-shaped seeds

使用桥形晶种制造的块状、熔融加工 YB2Cu3O7-_ 的晶界特性

• 期刊: Superconductor Science and Technology
• 影响因子: 3.6
• 作者: David Cardwell (Author)