Effects of B 4 C doping on critical current properties of MgB 2 superconductor

Journal of Applied Physics

Yeoh

Qin

et al. 2006

We evaluated the doping effect of two types of multiwall carbon nanotubes ͑CNTs͒ with different aspect ratios on MgB 2 / Fe monofilament wires. Relationships between microstructure, magnetic critical current density ͑J c ͒, critical temperature ͑T c ͒, upper critical field ͑H c2 ͒, and irreversibility field ͑H irr ͒ for pure and CNT doped wires were systematically studied for sintering temperature from 650 to 1000°C. As the sintering temperature increased, T c for short CNT doped sample slightly decreased, while T c for long CNT doped sample increased. This indicates better reactivity between MgB 2 and short CNT due to its small aspect ratio, and substitution of carbon ͑C͒ from short CNT for boron ͑B͒ occurs. In addition, short CNT doped samples sintered at high temperatures of 900 and 1000°C exhibited excellent J c , and this value was approximately 10 4 A/cm 2 in fields up to 8 T at 5 K. This suggests that short CNT is a promising carbon source for MgB 2 superconductor with excellent J c . In particular, inclusion of nanosized MgO particles and substitution of C into the MgB 2 lattice could result in strong flux pinning centers.

Section: Introductionmentioning

confidence: 99%

The doping effect of multiwall carbon nanotube on MgB2∕Fe superconductor wire

Journal of Applied Physics

Yeoh

Qin

et al. 2006

“…A significant enhancement in the J c of MgB 2 has been achieved through chemical doping with carbon (C) containing compounds, such SiC, C, B 4 C, and CNT. However, doping effects have been limited by the agglomeration of nanosized dopants and poor reactivity between boron (B) and C [2][3][4][5][6][7]. Moreover, the self-field and low-field J c were depressed due to the decrease in the superconducting volume.…”

Section: Introductionmentioning

confidence: 99%

ImprovedJ_cof MgB₂superconductor by ball milling using different media

Supercond. Sci. Technol.

Yeoh

et al. 2006

In this paper, the effects of ball milling B powders using different media, such as acetone, ethanol, and toluene on the superconducting properties of MgB 2 have been studied. It was observed that toluene medium was the most effective of them all for enhancing J c . J c was estimated to be 5 x 10 3 A/cm 2 at 8 T and 5 K. This value is much higher than that of pure MgB 2 that was not ball milled, by a factor of 20. It was considered that ball-milled B using toluene leads to smaller MgB 2 grains, resulting in enhanced J c at low operating temperature and high field.

“…1͒ and the high critical current density ͑J c ͒ of Ͼ10 5 cm −2 in moderate fields, magnesium diboride ͑MgB 2 ͒ superconductors could offer the promise of important largescale applications to be operated at 20 K. A significant enhancement in the electromagnetic properties of MgB 2 has been achieved through doping with various forms of carbon ͑C͒. [2][3][4][5][6] To take advantage of its T c of 39 K, enhancements of both the upper critical field ͑H c2 ͒ and J c are essential. Attempts to accomplish this have invoked the introduction of numerous techniques including chemical doping, [2][3][4][5][6] irradiation, 7 and various thermomechanical processing techniques.…”

mentioning

confidence: 99%

“…[2][3][4][5][6] To take advantage of its T c of 39 K, enhancements of both the upper critical field ͑H c2 ͒ and J c are essential. Attempts to accomplish this have invoked the introduction of numerous techniques including chemical doping, [2][3][4][5][6] irradiation, 7 and various thermomechanical processing techniques. 8,9 Chemical doping is a simple and readily scalable technique.…”

mentioning

confidence: 99%

Carbohydrate doping to enhance electromagnetic properties of MgB2 superconductors

Applied Physics Letters

Zhou

Hossain

et al. 2006

232

178

The effect of carbohydrate doping on lattice parameters, microstructure, Tc, Jc, Hirr, and Hc2 of MgB2 has been studied. In this work the authors used malic acid as an example of carbohydrates as an additive to MgB2. The advantages of carbohydrate doping include homogeneous mixing of precursor powders, avoidance of expansive nanoadditives, production of highly reactive C, and significant enhancement in Jc, Hirr, and Hc2 of MgB2, compared to undoped samples. The Jc for MgB2+30wt% C4H6O5 sample was increased by a factor of 21 at 5K and 8T without degradation of self-field Jc.