Optimization of Critical Currents in&amp;lt;tex&amp;gt;$rm MgB_2$&amp;lt;/tex&amp;gt;Wires and Coils

Serquis, A.; Civale, L.; Hammon, D. L.; Serrano, G.; Nesterenko, V. F.

doi:10.1109/tasc.2005.848787

Cited by 24 publications

(16 citation statements)

References 14 publications

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“…An impressing amount of works has been published about the effect of additives on the critical parameters of MgB 2 wires and tapes. The most efficient additive found so far is SiC [2][3][4][5][6], for which a J c (4.2K) value of 1x10 4 A/cm 2 has been reported [2] for fields slightly above 12 T at 4.2 K. Other known additives are C (as nanotubes or diamond powder) [7,8], WB [9], WSi 2 , ZrSi 2 [3,10], Ti [11], Si 3 N 4 [12,13], Na 2 CO 3 [14], aromatic hydrocarbons [15], hydrides [5] and B 4 C [16,17,20]. Most of these very different additives lead to an enhancement of J c , suggesting that more than one mechanism must affect the critical parameters of MgB 2 wires.…”

Section: The Additives To Mgbmentioning

confidence: 99%

Simultaneous Addition of B$_{4}$C$+$SiC to MgB$_{2}$ Wires and Consequences for ${\rm J}_{\rm c}$ and ${\rm B}_{\rm irr}$

Flükiger¹,

Lezza

Cesaretti

et al. 2007

IEEE Trans. Appl. Supercond.

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The simultaneous addition of various Carbon based additives (in the present case B 4 C + SiC) to Mg and B powders has been introduced as a new concept in view of enhancing the superconducting parameters B c2 , B irr and J c values of in situ Fe/MgB 2 wires. A series of Fe sheathed monofilamentary wires of 1.1 mm diameter with a MgB 2 core of 600 µm diameter was prepared with various B 4 C:SiC ratios, the relation being 2.5:7.5, 5:5, 7.5:2.5 and 7.5:7.5 (values in wt. %). After reaction of 1 hour at 760°C, the wire containing 7.5 wt.% B 4 C and 2.5 wt.% SiC powders exhibited a J c value of 1x10 4 A/cm 2 at 11.3 T and 4.2 K. Although only 2.5 wt.% SiC were added, these values are considerably above those of ternary wires with B 4 C additions, where the same J c value is obtained at 10T. The slope J c vs. B for the B 4 C + SiC wires is steeper than for SiC additives, the J c values at 4.2 K being superior at fields below 9 T. The lattice parameters a of the B 4 C + SiC added wires exhibit lower values than ternary wires with the same nominal C content, suggesting a higher C content in the MgB 2 phase. The "disorder" in the MgB 2 structure has been characterized as a partial substitution of B by Carbon. A reduction of the domain sizes in the c direction as well as in-plane to 250 Å and 124 Å has been determined from the FWHM and the breath values of the (110) and (002) peaks. With the simultaneous introduction of B 4 C + SiC, a strong improvement of J c and B irr has been obtained with respect to B 4 C additions.A further enhancement of J c is expected when using different combinations of additives with and without Carbon, aiming for a further raise of J c in wires with multiple additives, as a result of the combination of different mechanisms.

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Section: The Additives To Mgbmentioning

confidence: 99%

Simultaneous Addition of B$_{4}$C$+$SiC to MgB$_{2}$ Wires and Consequences for ${\rm J}_{\rm c}$ and ${\rm B}_{\rm irr}$

Flükiger¹,

Lezza

Cesaretti

et al. 2007

IEEE Trans. Appl. Supercond.

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“…Significant improvement in critical current carrying capacities of in-situ MgB 2 by various additives and nanoparticles [5][6][7][8][9][10][11][12][13][14] was observed, as the substitution reaction can easily occur via this route. For the application purpose, due to fewer fabrication parameters, ex situ method is more attractive and has been utilized by many researchers for making wires 15,16 and tapes. [17][18][19][20] Considerable effort is being made to better the J c values of exsitu MgB 2 via excess Mg and various nanoparticles as additives, spark plasma sintering, ball milling, etc.…”

Section: Introductionmentioning

confidence: 99%

“…[17][18][19][20] Considerable effort is being made to better the J c values of exsitu MgB 2 via excess Mg and various nanoparticles as additives, spark plasma sintering, ball milling, etc. 4,[15][16][17][18][19][20][21][22][23][24][25][26] The improvement in J c has been chiefly attributed to improved connectivity of superconducting grains, 27 pinning and upper critical field, 2,28 and/or change in anisotropy. 29 In our previous work, 23 the superconducting properties of ex-situ MgB 2 samples were found to vary as a function of excess Mg as well as the sintering temperature and the highest J c was observed in samples sintered at 900 C with 5% excess Mg.…”

Section: Introductionmentioning

confidence: 99%

Effect of excess Mg and nano-additives on the superconducting properties of weakly connected bulk MgB2

Bhadauria

Gupta

Kishan

et al. 2013

Journal of Applied Physics

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Articles you may be interested inConnectivity and critical current density of in-situ processed MgB2 superconductors: Effect of excess Mg and non-carbon based additives A new scaling relation for n-AlN doped superconducting MgB2SiC and carbon nanotube distinctive effects on the superconducting properties of bulk Mg B 2Series of ex-situ polycrystalline MgB 2 bulk samples, by adding different additives like more of excess Mg (5 wt. %), nanoparticles of Ag (3 wt. %), and SiC (10 wt. %) to a previously optimized composition MgB 2 þ Mg (5 wt. %), were prepared by solid state synthesis route. Detailed investigations were carried out by XRD, SEM, and thermoelectric power S(T), resistivity q(T), and magnetization M(B) at temperatures T ¼ 4.2-300 K and applied fields B ¼ 0-8 T. All the samples typically show low connectivity (i.e., normal state current carrying cross section $0.9%-3%). The effect of different additives was different on the critical current density (J c ) of the samples. The J c , for instance at T ¼ 4.2 K and B ¼ 1 T, varied between 4.8 Â 10 7 and 2.8 Â 10 8 A/m 2 for various samples. In comparison to the previously optimized values, the J c was enhanced by further addition of 5 wt. % Mg and degraded both by nano-SiC and nano-Ag addition. However, many of the other properties of the samples were not much affected. For instance, the samples did not show any change in the superconducting onsets, S(T) and the parallel upper critical field (B jj c2 (T) $ 11-13 T at 20 K and 20-21 T at 4.2 K). The J c (B) dependence also shows similar behavior in all the samples, where the J c is found to scale as B À1 up to a sample independent crossover field B cr $ 2 T and 1.3 T at T ¼ 4.2 and 20 K, respectively. At higher fields B > B cr , the J c (B) curves branch out and decrease rapidly towards zero at a sample dependent characteristic field. We try to understand these results quantitatively in terms of changes in connectivity, pinning, and anisotropy driven percolation. However, all our results and analysis point out that the intra-particle regions stay unaffected and mainly the inter-particle regions get affected by the additives leading to the J c variation in the weakly connected samples.

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“…However, the influence of SiC on the response is not observed. In the ex situ process it is necessary for higher HT temperatures (900 or above) to promote the possible reaction between some C-additives and MgB 2 to create effective pinning centers [10,11]. In particular, it was reported that flux pinning was enhanced by the carbon substitution for B with increasing sintering temperature [12] which justify that we could not see any effect of SiC addition at the chosen HT low temperatures.…”

Section: Resultsmentioning

confidence: 87%

Core Microstructure and Strain State Analysis in MgB₂Wires with Different Metal Sheaths

Sobrero

Malachevsky

Serquis

2015

Advances in Condensed Matter Physics

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We present a detailed analysis of the effect of the sheath materials on the microstructure and superconducting properties of MgB2wires produced by the powder-in-tube method (PIT). We reduced commercial MgB2powder by attrition milling in nitrogen atmosphere using tungsten carbide balls and obtained powders with grain sizes lower than 150 nm and different strain states through this process. Several Ti, stainless steel, and copper monofilamentary wires were prepared using these powders by the PIT method. We investigated different thermal treatments and mechanical paths during the processing of the wires for the enhancement of the critical currents. The superconducting properties were determined by magnetization measurements in a SQUID magnetometer. The correlation between the thermal treatments, structure, and superconducting properties is discussed.

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Optimization of Critical Currents in<tex>$rm MgB_2$</tex>Wires and Coils

Cited by 24 publications

References 14 publications

Simultaneous Addition of B$_{4}$C$+$SiC to MgB$_{2}$ Wires and Consequences for ${\rm J}_{\rm c}$ and ${\rm B}_{\rm irr}$

Simultaneous Addition of B$_{4}$C$+$SiC to MgB$_{2}$ Wires and Consequences for ${\rm J}_{\rm c}$ and ${\rm B}_{\rm irr}$

Effect of excess Mg and nano-additives on the superconducting properties of weakly connected bulk MgB2

Core Microstructure and Strain State Analysis in MgB₂Wires with Different Metal Sheaths

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Optimization of Critical Currents in&lt;tex&gt;$rm MgB_2$&lt;/tex&gt;Wires and Coils

Cited by 24 publications

References 14 publications

Simultaneous Addition of B$_{4}$C$+$SiC to MgB$_{2}$ Wires and Consequences for ${\rm J}_{\rm c}$ and ${\rm B}_{\rm irr}$

Simultaneous Addition of B$_{4}$C$+$SiC to MgB$_{2}$ Wires and Consequences for ${\rm J}_{\rm c}$ and ${\rm B}_{\rm irr}$

Effect of excess Mg and nano-additives on the superconducting properties of weakly connected bulk MgB2

Core Microstructure and Strain State Analysis in MgB2Wires with Different Metal Sheaths

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Product

Resources

About

Optimization of Critical Currents in<tex>$rm MgB_2$</tex>Wires and Coils

Core Microstructure and Strain State Analysis in MgB₂Wires with Different Metal Sheaths