Energy and the Physical Sciences: Novel multi-seeded bulk superconductors for sustainable engineering applications

Lead Research Organisation: University of Cambridge
Department Name: Engineering

Abstract

The ability to generate strong and stable magnetic fields is a critical enabling technology for a broad range of sustainable engineering applications. Almost invariably, more compact field sources and higher magnetic field densities lead directly to more efficient and cost effective devices. One example of this can be found in the widespread applications of small, high power DC electric motors, which have proliferated since the development of the cheap high energy density family of NdFeB materials in the 1980s. Wire-wound superconducting magnets, on the other hand, may offer the potential to generate large magnetic fields, but they are extremely expensive and are difficult to manufacture. A cheaper, simpler and more robust option is the use of magnetised bulk superconductors. The (RE)BCO (where RE = rare earth element such as Y, Nd, Sm, Gd, etc.) family of bulk, melt processed high temperature superconductors (HTS), in particular, is the subject of extensive world-wide developmental research. Bulk HTS materials offer considerable potential to both improve the performance of existing devices that incorporate permanent magnets and to develop new, high field and sustainable energy storage applications, in particular. Indeed, these materials represent a direct link between the physical sciences and the development of sustainable applications in the energy needs sector that will be fundamental to growth of the UK economy in the short to medium term.

A number of important scientific and technical challenges to the incorporation of (RE)BCO bulk superconducting materials into practical engineering applications remain. These include improving process efficiency, sample properties, yield, reducing the cost of raw materials, recycling, processing larger samples with conformal geometries, development of a practical magnetisation process and the development of bespoke cryogenic systems for specific applications.

The main objective of this proposal is to address and overcome the critical aspects of these challenges to gain a fundamental understanding of the single grain growth process. This will enable the cost-effective processing of (RE)BCO materials with conformal geometries that will be fundamental to their application in a range of sustainable engineering devices within the energy sector and healthcare industry. Specific emphasis of the project will be placed on the development of an effective recycling process to enable a new secondary bulk sample source for low to medium field applications, the development of a novel multi-seeding technique for fabricating large samples of conformal geometry and the development of a novel fabrication process based on a graded composition to produce bulk samples with homogeneous superconducting properties throughout the bulk microstructure.

Planned Impact

The impact of this project will be particularly significant for the Cambridge Group and the collaborators, building on an outstanding research and collaboration track record. The project will also benefit both industry and academia worldwide: 1. Engineering industries involved in the manufacture of magnetic bearings, flywheel energy storage systems, high field permanent magnet devices and magnetic separators; 2. Companies manufacturing permanent magnet MRI/NMR systems; 3. High efficiency, compact motors and generators. Researchers working on magnetic and transport properties, solidification and phase kinetics of (RE)BCO materials will also benefit directly from the results of the project. Samples will be supplied to the relevant UK academic institutions and schools free of charge, as required.

The main mechanism for impact and exploitation is via the established collaboration with Boeing Company, which has a number of large, active (propriety) projects with potential users of bulk material in energy storage flywheel systems and other applications such as non-destructive testing. This is a ready-made market, and offers a unique opportunity for the UK to make a major impact on HTS technology on an international scale. Unfortunately the details of these projects are proprietary, although they represent a combined potential market of tens of millions of dollars in the medium to long term. State of the art bulk material developed as part of this project would be retro-fitted into these existing devices (approximately 50 samples in each energy storage flywheel device) to yield a direct route to commercial exploitation. Other emerging applications relevant to developing sustainable engineering technologies include high efficiency, light and compact motors and generators, testing applications requiring a large magnetic field, stable magnetic bearings, fault current limiters and magnetic separators. Boeing has potential interest in these devices, and is well-placed to supply the global market. Cambridge and Boeing have an existing, formal IPR agreement in place, including joint patent interests, and the partnership is well-positioned to fully exploit emerging bulk superconductor technology. The outputs with potential technical and commercial impact will be identified by comparing the properties, manufacturability and cost of state of the art bulk samples with the requirements of global industry, as defined mainly by the Boeing Company. This will provide bench-mark data by which to evaluate the output of the project and enable comparison with competing technology (where it exists). Key properties are the magnitude of trapped field at 77 and 50 K, mechanical strength and production cost, which will be monitored by Boeing as part of the project. In-situ performance of bulk samples in the Boeing energy storage flywheel will provide further technical output to quantify the capability of the bulk materials in an applications-specific environment.

The SRA appointed to the project will undertake the impact activities in close collaboration with the PI. Prof. Cardwell has extensive experience of the generation and protection of IPR, and is well placed to oversee and manage this project. Cambridge Enterprise (a University body established to advise and support the commercial exploitation of emerging technology) will be involved closely with the transfer of manufacturing technology outside the University. Cambridge Enterprise employs specialists in IPR, market research and contract law at no direct cost to the project, and will play a key role in the exploitation of the commercial potential of the material developed during this research.

Publications

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Rush J (2016) Transport in Bulk Superconductors: A Practical Approach? in IEEE Transactions on Applied Superconductivity

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Goodfellow A (2016) Microstructural evolution in multiseeded YBCO bulk samples grown by the TSMG process in Superconductor Science and Technology

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Shi Y (2015) A Reliable Method for Recycling ( RE )-Ba-Cu-O ( RE : Sm, Gd, Y) Bulk Superconductors in Journal of the American Ceramic Society

 
Description Significant progress has been made in the areas related to all work packages. The discoveries and developments are: 1: Growth Grain boundaries that carry transport current (a) Bridge seeding has been developed to ensure the alignment of the two seeds (2 or more) in the multi-seeding processes so that multi-seeded single grains with desired orientation can grow well and the properties of grain boundaries of multi-seeded single grains can studied without confusion of misalignments. Large, single SmBCO grains up to 20 mm in diameter fabricated by a conventional top seeded melt growth (TSMG) process have been selected and cut into bridge-shaped geometries. The two legs of the bridge are used as two seeds with desired orientation. These so-called 0°-0° and 45°-45° bridge-seeds are labelled according to their relative orientation in the parent grain. These bridges have been successfully prepared in different lengths from 2 to 10 mm for fabricating YBCO single grains. (b) Buffering technique has been developed to improve the reliability of the seeding process. Silver (Ag) is an established additive for improving the mechanical properties of single grain, (RE)BCO bulk superconductors (where RE = Sm, Gd and Y). The presence of Ag in the (RE)BCO bulk composition, however, typically reduces the melting temperature of the single crystal seed in the top seeded melt growth (TSMG) process, which complicates significantly the controlled nucleation and subsequent epitaxial growth of a single grain, which is essential for high field engineering applications. The new process involves placing a small, 0.3 g and 5 mm in diameter SmBCO (75wt%Sm123 25wt%Sm211) pellet between the generic seed and the growing SmBCO-Ag pellet as a buffer to prevent Ag diffusion from the pellet to the seed to inhibit melting of the seed. This has improved the seeding success rate almost to 100%. 2: Achieving Larger grains from a single seed Large YBCO and GdBCO-Ag single grains up to 41 mm in diameter can now be fabricated reliably. SmBCO-Ag single grains up to 32 mm in diameter can now also be fabricated reliably for the first time in 20 years due to the buffering technique. Moreover, YBCO single grains containing graded concentrations of Y-211 CeO2 in U-shaped layers within a cylindrical sample up to 32 mm diameter have been developed and studied in detail, and shown to exhibit improved superconducting properties. 3: Improving the TSMG process (a) Optimisation of the parameters in the crystal growth process has been carried out. We have studied the importance in controlling the liquid loss during the crystal growth, the effects of precursor particle size on growth, the effects of amount of Y-211 on growth rate and differences and similarities between the Top Seeded Melt-Growth and Infiltration Growth processing techniques. A new analysis technique based on EDX has been developed to examine the chemical composition of solid single grains so that changes in chemical composition during the crystal growth process can be detected. This technique greatly helps the understanding of the relation between growth heating profile and chemical composition (RE-211 concentration) at different positions within the growing sample. A paper on the growth rate of YBCO system has been published and another on the effect of the presence of Y-211 on the crystal growth process has been submitted to the Journal of Crystal Growth. (b) A generic method for recycling failed (RE)BCO(Ag) bulk material into single grains has developed based on an infiltration growth technique by replenishing liquid phase lost during growth due to the effects of gravity. The success rate of this method on batch recycling is close to 100%. The superconducting properties of the recycled samples have been measured and to establish their potential for use in applications. (c) A shrink-fitting process has been developed to withstand the high interface pressure associated with the high magnetic field generated in single grain bulk material. As a result, the trapped field of GdBCO-Ag single grains can be measured without the samples failing mechanically when high field is applied at low temperature. This technique has led to a world record of trapped field in superconducting bulk materials of 17.6 T. A paper has been published in Superconductor Science and Technology. Work Package 4: Large, shaped bulk superconductors Larger, multi-seeded single grains up to 32 mm diameter and bar-shaped multi-seeded samples up to 60 mm in length have been fabricated. Further research on these multi-seeded samples is being performed.
Exploitation Route Bridge-seeding will be used by the Cambridge group and others to develop a deeper understanding the grain boundary properties in multi-seeded samples. Samples made using this technique have attracted attention in Japan by researchers trying to understand how magnetic flux moves into the facet lines and grain boundaries by use of multi-seeded single grain samples. Multi-seeded samples will be used to generate the levitation and attraction forces when large samples are required. One company in Hong Kong is interested in the strong attracting force generated by large single grains. Multi-seeded samples will be developed to produce such force. Bar-shaped, multi-seeded samples have attracted attention in Saudi Arabia (one of our collaborators) for use in tracks for magnetic levitation. The buffering technique will be used in other groups worldwide for improving the reliability of the seeding process. Large, single grains and their superconducting properties have attracted attention within the modeling community. YBCO and GdBCO-Ag single grain samples have been provided to other groups free of charge to enable them to perform modeling and related experiments. One paper has been published, and further collaboration is under way. Large, single grains and their superconducting properties have also attracted attention from the applied community, and for application in linear synchronous motors, in particular. Single grain, bulk GdBCO-Ag superconductors of diameter 20 mm, 30 mm and 40 mm have been used in such a device for the first time. One paper has been published based on the results of this study.
Sectors Energy,Healthcare

 
Description Bridge-seeding will be used by the Cambridge group and others to develop a deeper understanding the grain boundary properties in multi-seeded samples. Samples made using this technique have attracted attention in Japan by researchers trying to understand how magnetic flux moves into the facet lines and grain boundaries by use of multi-seeded single grain samples. Multi-seeded samples will be used to generate the levitation and attraction forces when large samples are required. One company in Hong Kong is interested in the strong attracting force generated by large single grains. Multi-seeded samples will be developed to produce such force. Bar-shaped, multi-seeded samples have attracted attention in Saudi Arabia (one of our collaborators) for use in tracks for magnetic levitation. The buffering technique will be used in other groups worldwide for improving the reliability of the seeding process. Large, single grains and their superconducting properties have attracted attention within the modeling community. YBCO and GdBCO-Ag single grain samples have been provided to other groups free of charge to enable them to perform modeling and related experiments. One paper has been published, and further collaboration is under way. Large, single grains and their superconducting properties have also attracted attention from the applied community, and for application in linear synchronous motors, in particular. Single grain, bulk GdBCO-Ag superconductors of diameter 20 mm, 30 mm and 40 mm have been used in such a device for the first time. One paper has been published based on the results of this study.
First Year Of Impact 2015
Sector Energy,Healthcare,Transport
Impact Types Societal

 
Description Composite bulk superconducting magnets for high field applications
Amount £649,885 (GBP)
Funding ID EP/P00962X/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 11/2016 
End 10/2019
 
Description Atominstitut der Oester Universitaet 
Organisation Vienna University of Technology
Department Institute of Atomic and Subatomic Physics (Atominstitut)
Country Austria 
Sector Academic/University 
Start Year 2004
 
Description Boeing-Cambridge collaboration 
Organisation Boeing
Country United States 
Sector Private 
PI Contribution The contribution was part of an on-going collaboration on the development of bulk superconductors for applications. We have transferred processing technology to Boeing and have provided bulk superconductors for incorporating in a flywheel energy storage device by Boeing.
Collaborator Contribution Boeing developed the flywheel system that incorporates our samples.
Impact The further development pf the Boeing energy storage flywheel.
 
Description IFW Desden 
Organisation Leibniz Association
Department Leibniz Institute for Solid State and Materials Research
Country Germany 
Sector Academic/University 
Start Year 2004
 
Description University of Liege 
Organisation University of Liege
Country Belgium 
Sector Academic/University 
Start Year 2004