Effect of grain refinement on enhancing critical current density and upper critical field in undoped MgB2 <i>ex situ</i> tapes

Malagoli, Andrea; Braccini, V.; Tropeano, M.; Vignolo, M.; Bernini, C.; Fanciulli, Carlo; Romano, G.; Putti, M.; Ferdeghini, C.; Mossang, E.; Polyanskii, Anatolii; Larbalestier, D. C.

doi:10.1063/1.3021468

Cited by 56 publications

(39 citation statements)

References 36 publications

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“…Third, the grain refinement in thin filaments can enhance grain boundary pinning but at the same time suppress intergrain currents. For MgB 2 superconductors, in which grain boundaries are transparent for current flow, the grain refinement has an overall positive effect to J c performance [39,40]. However, for iron pnictide superconductors, whose transport J c can be suppressed by high-angle grain boundaries, we may try to further improve the grain connectivity by optimizing heat treatment.…”

Section: Resultsmentioning

confidence: 99%

Critical current density and microstructure of iron sheathed multifilamentary Sr1−xKxFe2As2/Ag composite conductors

Yao

Lin

Zhang

et al. 2015

Journal of Applied Physics

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Iron-based superconductors have been considered to be very promising in high-field applications, for which multifilamentary wire and tape conductors with high mechanical strength are essential. In this work, 7-， 19-and 114-filament Sr 0.6 K 0.4 Fe 2 As 2 (Sr-122) superconducting wires and tapes with silver as matrix and iron as outer reinforcing sheath were produced by the ex situ powder-in-tube method.The mass densities of Sr-122 phase in 7-and 19-filament conductors were investigated by microhardness characterization, which revealed a positive correlation Author to whom any correspondence should be addressed.

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Section: Resultsmentioning

confidence: 99%

Critical current density and microstructure of iron sheathed multifilamentary Sr1−xKxFe2As2/Ag composite conductors

Yao

Lin

Zhang

et al. 2015

Journal of Applied Physics

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“…The grain size of LB and 12LB was estimated to be about 60 nm (BET analysis). The average grain size of milled powders is 400 nm [18,22], very close to the grain size of the powders studied in this work. Its well-known that finer precursor powders are always an added advantage on final performance of superconductors, regardless of the process used in-situ or ex-situ.…”

Section: Discussionmentioning

confidence: 50%

“…Samples NM and M [22] are bulks produced removing the Ni sheath from the tapes. The boron precursor is the same of CB (H.C. Starck, Grade I), and MgB powder were used to fill directly the nickel tube (NM), while for M sample was previously milled.…”

Section: Characterization Of Mgb 2 Bulk Samplesmentioning

confidence: 99%

Section: Mgb 2 Bulk Powder and Wire Preparation And Their Characterimentioning

confidence: 99%

“…Quantum Design Physical Properties Measurement System (PPMS) up to 9 T was employed to evaluate H c2 in bulk samples, using a current of 1 mA with the magnetic field applied perpendicular to the samples surface. H c2 values were taken at 90% of the resistive transition and H at 10% [22]. The remaining part of boron powder was used to synthesize Laboratory (GHMFL) and at the Physics Department of Genoa University (DiFi), respectively on 9 cm long sample up to 13 T and on 20 cm long sample up to 7 T. The criteria adopted to determine I c was 1 μV/cm and I c data were converted into J c values by SEM image.…”

Section: Mgb 2 Bulk Powder and Wire Preparation And Their Characterimentioning

confidence: 99%

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High temperature heat treatment on boron precursor and PIT process optimization to improve theJ_cperformance of MgB₂-based conductors

Vignolo

Bovone

Bernini

et al. 2013

Supercond. Sci. Technol.

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Abstract:Promising results reported in our previous works led us to think that boron's production process plays a crucial role in MgBB 2 synthesis. A new method for boron preparation has been developed in our laboratory. This particular process is based on magnesiothermic reaction (Moissan's process) with the addition of an initial step that gives boron powder with nano-metric grain size. In this paper we report our efforts regarding optimization of PIT method for these nanometric powders and the resolution of problems previously highlighted such as the difficulty in powder packaging and the high friction phenomena occurring during cold working. This increases cracking during the tape and wire manufacturing leading to its failure. Packaging problems are related to the amorphous nature of boron synthesized in our laboratory, so a crystallization treatment was applied to improve boron's crystallinity. To prevent excessive friction phenomena we synthesized non-stoichiometric MgB 2 and using magnesium as lubricant. Our goal is the J c improvement, but a global physical-chemical characterization was also made to analyze the improvement given by our treatments: this characterization includes X-ray diffraction, ρ(T) measurement, SEM image, besides magnetic and transport J c measurements. IntroductionAfter 12 years since the discovery of superconductivity in MgB 2, many efforts have been done in order to improve its performances and make it competitive with traditional superconductors. This is possible due to its relatively high critical temperature (T c ) that permits to use MgB 2 -based conductors at 20 K by using a cryocooler. Also compared to other superconducting materials MgB 2 tapes are easy to manufacture and of low cost. Despite the good results have been achieve so far, huge efforts are necessary especially on J c improvement, which is the main parameter from application point of view. This could be achieved by obtaining a complex balance between connectivity, upper critical field (H c2 ) and pinning force induced by grain boundaries, precipitates Experimental Boron powder preparation and characterization.Details of boron synthesis and purification have been given in [9]. Once boron is purified at the end of the process two amounts of powder were taken from the same batch to effect the heat treatment of crystallization. The first one (12LB) has been set in an iron boat and placed in a tubular furnace at 1200 °C for 120 minutes, under Ar flow. The second sample (17LB) was put in tantalum crucible, sealed in a quartz ampoule, and heat treated at 1700 °C through an inductive furnace, for 30 minutes. X-ray analysis was made on these powders at the end of the treatment, on pristine powder (LB), and on commercial boron (CB), to verify the improvement of crystal quality led by heat treatment. XRD measurements were performed using a PHILIPS (PW 1170/90 Cu Kα) diffractometer at 40 KV and 30 mA. MgB 2 bulk, powder and wire preparation and their characterization.After thermal treatment the powders are used to synthesize...

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Magnesium Diboride

Nardelli

Pallecchi

Tropeano

2015

Digital Encyclopedia of Applied Physics

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The article contains sections titled: Introduction Intrinsic and Extrinsic Properties of MgB 2 Sample Preparation Applications of MgB 2 Summary and Outlook

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Effect of grain refinement on enhancing critical current density and upper critical field in undoped MgB2 ex situ tapes

Abstract: Articles you may be interested inMicrostructure-critical current density model for MgB 2 wires and tapes

Cited by 56 publications

References 36 publications

Critical current density and microstructure of iron sheathed multifilamentary Sr1−xKxFe2As2/Ag composite conductors

Critical current density and microstructure of iron sheathed multifilamentary Sr1−xKxFe2As2/Ag composite conductors

High temperature heat treatment on boron precursor and PIT process optimization to improve theJ_cperformance of MgB₂-based conductors

Magnesium Diboride

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Effect of grain refinement on enhancing critical current density and upper critical field in undoped MgB2 ex situ tapes

Abstract: Articles you may be interested inMicrostructure-critical current density model for MgB 2 wires and tapes

Cited by 56 publications

References 36 publications

Critical current density and microstructure of iron sheathed multifilamentary Sr1−xKxFe2As2/Ag composite conductors

Critical current density and microstructure of iron sheathed multifilamentary Sr1−xKxFe2As2/Ag composite conductors

High temperature heat treatment on boron precursor and PIT process optimization to improve theJcperformance of MgB2-based conductors

Magnesium Diboride

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Product

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High temperature heat treatment on boron precursor and PIT process optimization to improve theJ_cperformance of MgB₂-based conductors