Resistive transition measurements are reported for MgB 2 strands with SiC dopants. The starting Mg powders were 325 mesh 99.9% pure, and the B powders were amorphous, 99.9% pure, and at a typical size of 1-2 µm. The SiC was added as 10 mol% of SiC to 90 mol% of binary MgB 2 [(MgB2)0.9(SiC)0.1]. Three different SiC powders were used; the average particle sizes were 200 nm, 30 nm, and 15 nm. The strands were heat treated for times ranging from 5 to 30 minutes at temperatures from 675°C to 1000°C. Strands with 200 nm size SiC additions had µ 0 H irr and B c2 which maximized at 25.4 T and 29.7 T after heating at 800°C for 30 minutes. The highest values were seen for a strand with 15 nm SiC heated at 725°C for 30 minutes which had a µ 0 H irr of 29 T and a B c2 higher than 33 T.
Recent advances in MgB 2 conductors are leading to a new level of performance.Based on the use of proper powders, proper chemistry, and an architecture which incorporates internal Mg diffusion (IMD), a dense MgB 2 structure with not only a high critical current density J c , but also a high engineering critical current density, J e , can be obtained. In this paper, a series of these advanced (or second-generation, "2G") conductors has been prepared. Scanning electron microscopy and associated energy dispersive X-ray spectroscopy were applied to characterize the microstructures and compositions of the wires, and a dense MgB 2 layer structure was observed. The best layer J c for our sample is 1.07x10 5 A/cm 2 at 10 T, 4.2 K, and our best J e is seen to be 1.67x10 4 A/cm 2 at 10 T, 4.2 K.Optimization of the transport properties of these advanced wires is discussed in terms of Bpowder choice, area fraction, and the MgB 2 layer growth mechanism.
PACS: 74.70.Ad; 74.25.Sv; 74.25.Qt; 74.62.Dh Keywords: MgB 2 , layer critical current density J c , engineering critical current density J e , internal magnesium diffusion (IMD)
Since 2001, when magnesium diboride (MgB2) was first reported to have a transition temperature of 39 K, conductor development has progressed to where MgB2 superconductor wire in kilometer‐long piece‐lengths has been demonstrated in coil form. Now that the wire is available commercially, work has started on demonstrating a MgB2 wire in superconducting devices. This article discusses the progress on MgB2 conductor and coil development, and the potential for MgB2 superconductors in a variety of commercial applications: magnetic resonance imaging, fault current limiters, transformers, motors, generators, adiabatic demagnetization refrigerators, magnetic separation, magnetic levitation, superconducting magnetic energy storage, and high‐energy physics applications.
An advanced internal Mg infiltration method (AIMI) in this paper has been shown to be effective in producing superconducting wires containing dense MgB 2 layers with high critical current densities. In this study, the in-field critical current densities of a series of AIMI-fabricated MgB 2 strands were investigated in terms of C doping levels, heat treatment (HT) time and filament numbers. The highest layer J c for our monofilamentary AIMI strands is 1.5 × 10 5 A/cm 2 at 10 T, 4.2 K, when the C concentration was 3 mol% and the strand was heat-treated at 675 °C for 4 hours. Transport critical currents were also measured at 4.2 K on short samples and one-meter segments of eighteen-filament Cdoped AIMI strands. The layer J c s reached 4.3 × 10 5 A/cm 2 at 5 T and 7.1 × 10 4 A/cm 2 at 10 T, twice as high as those of the best PIT strands. The analysis of these results indicates that the AIMI strands, possessing both high layer J c s and engineering J e s after further optimization, have strong potential for commercial applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.