Enhancement of phase formation and critical current density in bismuth-based superconductor by nanoparticles doping
Project Status: 3 Approved without Funding
Duration in months: 24 months
Objective
High-temperature superconductivity is one of the most important new technologies in the 21st century, a century where mankind focuses its efforts on energy, resources, and the environment. Superconducting property causes certain materials, at low temperatures, to lose all resistance to the flow of electricity. This state of “losslessness” enables a range of innovative technology applications for more efficient electrical power plants, higher capacity power cables, environmentally friendly oil-free transformers, more powerful motors and compact generators, and superconducting magnetic-energy storage systems. The foundation of these applications is a superconducting wire, capable of carrying vastly higher currents than conventional copper wires of the same dimension.
Among a superconducting materials, the bismuth-based (Bi,Pb)2Sr2Ca2Cu3Oy compound, called Bi(Pb)-2223, is the one of the most interesting for its great potential for large-scale applications in the no-loss electric power industry. The fabrication of superconducting wire by the Powder in Tube (PIT) method involves the packing of a precursor (wire material) into a silver tube. Then, precursor within the silver matrix undergoes conversion to the desired Bi(Pb)-2223 superconducting material, during the mechanical deformation and heat-treatment steps. As a result of the introduction of the CT-OP (Controlled Over Pressure) sintering process in 2004, Sumitomo Electric Industries, LTD. succeeded in improving various characteristics such as critical current, Jc, (largest current value that can be passed in the superconducting state) and mechanical properties of Bi(Pb)-2223 wire. By optimizing all manufacturing conditions including powder preparation, deformation and sintering processes, the critical current in long-length (up to 1.5 km) wire with a cross section of 1 mm2 has reached 200 A at 77 K and in self-field, which is the world record. These remarkably innovated wires are now manufactured commercially under the trademark “DI-BSCCO” (Dynamically innovative BSCCO) wires. The high cost of fabrication is still the main impediment preventing the silver-sheathed Bi(Pb)-2223/Ag wires from competing with conventional materials in the market. In order to put superconductors into practical use, enhancement of current carrying capacity, Jc, of superconducting wire is the primary requirement. Moreover, the rate of Bi(Pb)-2223 formation is extremely low and requires usually hundreds of hours to produce a nearly single-phase Bi(Pb)-2223. Quality of precursor is of vital importance to the final properties of superconducting wire and is governed by the phase assemblage and particle size. After the discovery of Bi(Pb)-2223 superconductor a tremendous efforts have been undertaken to accelerate the formation of (Bi,Pb)2Sr2Ca2Cu3Oy materials and improve their current carrying capacity, but after more than two decades, the formation of pure Bi(Pb)-2223 superconducting material having enhanced current carrying capacity is still an open subject in the field of applied superconductivity. Thus, large-scale applications of superconducting wires now depend significantly on cost-effective resolution of materials and fabrication issues.
Highly promising results in this direction were obtained by the Project participants. We have very recently found that slight doping with boron-containing additives enhances drastically the reactivity of precursor powder (Fig.1), and therefore also formation kinetics of (Bi,Pb)-2223 material. Based on these results, the project participants from the Georgian Technical University (Leading organization) as intellectual property owners have recently received four patents from the National Intellectual Property Center of Georgia (“Sakpatenti”). Moreover, current carrying capacity of doped samples has been enhanced nearly 3 times compared to the reference (undoped) one. Our preliminary results also indicate that the Jc value of Bi(Pb)-2223 materials is further improved by the using of ball-milled ultra-fine precursor powders.
Presented project is a continuation of these physical&technological studies. Motivated by own findings, Project team will apply combined process of appropriate doping and high-energy planetary ball-milling (down to nano-scale) of precursor materialfor superconducting wire.
The first-priority objective of the Project is to create the technology which controls the fabrication of bismuth-based precursor materialfor superconducting wire with higher current-carrying capacity and higher rate of formation compared to the conventional technology.
The proposed investigations will be focused on two main aspects:
1. Selection/optimization of the doping level and particle size distribution for the precursor;
2. Fabrication and testing of Ag-sheated Bi(Pb)-2223 superconducting wires (tapes), using the optimized precursor.
Optimization of precursor via a novel, accelerated and energy efficient processing route will provide significant enhancement of both current-carrying capability and formation rate of Bi(Pb)-2223 superconducting material over conventional technology. Project results are expected to offer technical performance improvement and will markedly reduce the cost/performance metric of Ag-sheated Bi(Pb)-2223 superconducting wires, facilitating widespread commercial application of superconducting components for power generation, power transmission, and power end-user electric motor markets.
The project is presented by a joint group of scientists of the Georgian Technical University (Georgia) and International Scientific-Educational Center of NAS RA (Republic of Armenia). Project team includes high skilled physicists, materials scientists and engineers with large experience in applied superconductivity.
Solid state reaction method, Powder in Tube (PIT) technology, X-ray diffraction analysis (XRD), Scanning Electron Microscopy (SEM), and high energy ball-milling in combination with resistivity and critical current density measurements at various applied magnetic fields will be basic tools for fabricating and characterizing bulk materials and wires.
This project corresponds completely to the goals of ISTC. In case the project is practically implemented the scientists who in the past were occupied in military fields will have the opportunity to change the direction of their research to a peaceful orientation. Active teamwork with collaborators, publication of results in open press, and participation in international conferences will promote integration of participants of the proposed project into an international scientific community. The ISTC support of the studies within this project will stimulate the implementation of advanced technologies in Georgia and Republic of Armenia, including nanotechnology.
Participating Institutions
LEADING
Georgian Technical University (GTU)
PARTICIPATING
International Scientific-Educational Center (ISEC NAS RA)
COLLABORATOR
University of Bristol / School of Chemistry
COLLABORATOR
University of California (UCSD)
COLLABORATOR
Institute of High Pressure Physics of the Polish Academy of Sciences
