Influence of the lamella structure and high isostatic pressure on the critical current density in in situ MgB2 wires without a barrier

Mroczek, Z.; Morawski, A.; Czujko, Tomasz; Karaboğa, Fırat; Akdoğan, Mustafa; Zaleski, A.; Małecka, Małgorzata A.; Cetner, T.; Yetiş, H.; Gajda, D.; Belenli, I.

doi:10.1016/j.jallcom.2018.10.269

Cited by 13 publications

(13 citation statements)

References 23 publications

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“…This also leads to the formation of a lamellar structure in MgB 2 wires. Studies have shown that the lamellar structure significantly increases J c and B irr and improves the connections between grains [ 39 ]. Our results showed that thinner and longer Mg grains obtain a lamellar structure with thinner layers and improve the longitudinal connection between grains.…”

Section: Results—structurementioning

confidence: 99%

“…The results showed that annealing under high isostatic pressure (HIP) significantly improved the structure of the MgB 2 material in wires made by using the powder in tube (PIT) method (e.g., small grains, small size, fewer voids, increased connection between grains, increased MgB 2 density, enhanced homogeneity of MgB 2 material, and increased density of structural defects) [ 34 , 35 , 36 , 37 , 38 , 39 ]. Additionally, the HIP process increases the density of pinning centers [ 35 ] and mainly increases the density of high-field pinning centers [ 36 ], leading to a significant increase in J c under a high magnetic field and B irr and a decrease in T c [ 35 ].…”

Section: Introductionmentioning

confidence: 99%

“…This is very important because it permits heat treatment at higher temperatures for pure Mg in the solid state. Thermal treatments in the solid state will increase the density of MgB 2 material [ 35 , 36 , 37 , 38 , 39 ].…”

Section: Introductionmentioning

confidence: 99%

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Effect of Heat Treatments under High Isostatic Pressure on the Transport Critical Current Density at 4.2 K and 20 K in Doped and Undoped MgB2 Wires

et al. 2021

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Annealing undoped MgB2 wires under high isostatic pressure (HIP) increases transport critical current density (Jtc) by 10% at 4.2 K in range magnetic fields from 4 T to 12 T and significantly increases Jtc by 25% in range magnetic fields from 2 T to 4 T and does not increase Jtc above 4 T at 20 K. Further research shows that a large amount of 10% SiC admixture and thermal treatment under a high isostatic pressure of 1 GPa significantly increases the Jtc by 40% at 4.2 K in magnetic fields above 6 T and reduces Jtc by one order at 20 K in MgB2 wires. Additionally, our research showed that heat treatment under high isostatic pressure is more evident in wires with smaller diameters, as it greatly increases the density of MgB2 material and the number of connections between grains compared to MgB2 wires with larger diameters, but only during the Mg solid-state reaction. In addition, our study indicates that smaller wire diameters and high isostatic pressure do not lead to a higher density of MgB2 material and more connections between grains during the liquid-state Mg reaction.

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Section: Results—structurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Heat Treatments under High Isostatic Pressure on the Transport Critical Current Density at 4.2 K and 20 K in Doped and Undoped MgB2 Wires

et al. 2021

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“…Measurements of B irr , T c , B c2 , and R n were made using a physical property measurement system (Physical Property Measurement System (PPMS), Model 7100, 15 Hz and AC current, I AC = 100 mA, Quantum Design, San Diego, CA, USA). The critical parameters B irr , T c , and B c2 were identified for the criteria of 10%, 50%, and 90% resistance in the normal state [18]. The resistance in the normal state (R n ) for B = 0 T was determined at 40 K. However, magnetoresistance was determined in the range of the magnetic field from 0 T to 14 T. Transport critical current measurements were made using a measurement system with a bitter magnet up to 14 T at a temperature of 4.2 K. The critical current (I c ) was determined based on the 1 µm/cm criterion [29].…”

Section: Methodsmentioning

confidence: 99%

“…Figure 1a,c,e shows that the layered structure is clustered in all samples (white arrow), creating dense superconducting regions with a highly heterogeneous distribution. The homogeneous layered structure was shown to significantly improve the connections between grains, leading to an increase in critical current density [18]. However, the heterogeneous distribution of dense regions reduces the connection between grains and leads to a reduction in J c and J ce .…”

Section: Analysis Of the Structure Of Mgb 2 Materialsmentioning

confidence: 99%

Influence of Amorphous Boron Grain Size, High Isostatic Pressure, Annealing Temperature, and Filling Density of Unreacted Material on Structure, Critical Parameters, n-Value, and Engineering Critical Current Density in MgB2 Wires

et al. 2021

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Our results show that a lower density of unreacted Mg + B material during an Mg solid-state synthesis reaction leads to a significant reduction in the quantity of the superconducting phase and lowers the homogeneity of the superconducting material. It also significantly reduces the irreversible magnetic field (Birr), critical temperature (Tc), upper magnetic field (Bc2), engineered critical current density (Jec), and n-value, despite high isostatic pressure (HIP) treatment and the use of nanoboron in the sample. Our measurements show that samples with large boron grains with an 8% higher density of unreacted Mg + B material allow better critical parameters to be achieved. Studies have shown that the density of unreacted material has little effect on Birr, Tc, Bc2, Jec, and the n-value for an Mg liquid-state synthesis reaction. The results show that the critical parameters during an Mg liquid-state synthesis reaction depend mainly on grain size. Nanoboron grains allow for the highest Birr, Tc, Bc2, Jec, and n-values. Scanning electron microscopy (SEM) images taken from the longitudinal sections of the wires show that the samples annealed under low isostatic pressure have a highly heterogeneous structure. High isostatic pressure heat treatment greatly improves the homogeneity of MgB2.

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The Optimization of Jc, Birr, n value, Wires Diameter, and Research of the Dominant Pinning Mechanism for Applications of Undoped MgB2 in Superconducting Multi-section Coils

Gajda

Zaleski

Morawski

et al. 2020

J Supercond Nov Magn

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This article discusses the influence of MgB2 wire diameter on critical parameters, dominant pinning mechanism, and n value. Studies were conducted on multifilament MgB2 wires of the 0.84 mm and 0.64 mm diameter. The wires were annealed under 1 GPa isostatic pressure, between 650 and 730 °C. Studies show that the best results (Jc, Birr, n value, and point pinning mechanism) for a 0.64-mm wire were obtained with annealing temperature of 650 °C. However, the best results for wires with a 0.84-mm diameter were obtained with annealing temperature of 730 °C. This research was conducted for exploring the use of MgB2 wires in multi-section superconducting coils, e.g., main coils generating magnetic fields and compensation coils—increasing the homogeneity of the magnetic field. Our research indicates that the main coil made with larger diameter wires should be heated at higher temperature (730 °C). In contrast, compensating coils with smaller diameter wires should be heated at a lower temperature (650 °C).

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Influence of the lamella structure and high isostatic pressure on the critical current density in in situ MgB2 wires without a barrier

Cited by 13 publications

References 23 publications

Effect of Heat Treatments under High Isostatic Pressure on the Transport Critical Current Density at 4.2 K and 20 K in Doped and Undoped MgB2 Wires

Effect of Heat Treatments under High Isostatic Pressure on the Transport Critical Current Density at 4.2 K and 20 K in Doped and Undoped MgB2 Wires

Influence of Amorphous Boron Grain Size, High Isostatic Pressure, Annealing Temperature, and Filling Density of Unreacted Material on Structure, Critical Parameters, n-Value, and Engineering Critical Current Density in MgB2 Wires

The Optimization of Jc, Birr, n value, Wires Diameter, and Research of the Dominant Pinning Mechanism for Applications of Undoped MgB2 in Superconducting Multi-section Coils

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