Improvement of critical properties of undoped, multifilamentary MgB<sub>2</sub>wires in Nb/Cu after annealing under high gas pressure

Cetner, T.; Morawski, A.; Adamczyk, Krzysztof; Rindfleisch, M.; Tomsic, M.; Zaleski, A.; Gajda, D.; Presz, A.

doi:10.1080/08957959.2012.722211

Cited by 19 publications

(12 citation statements)

References 8 publications

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“…The wires were made to a diameter of 0.83 mm, with a fill factor of 15%. All MgB 2 wires were annealed in isostatic pressure at the Institute of High Pressure Research in Warsaw [78][79][80]. The HIP was conducted in a 5 N argon atmosphere in a gas pressure chamber (Table 2).…”

Section: Fabrication Of Nbti Wires Mgb 2 Wires and Methods Of J C Mementioning

confidence: 99%

Analysis Method of High-Field Pinning Centers in NbTi Wires and MgB2 Wires

Gajda

2018

J Low Temp Phys

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The main purpose of this article is to show an easier and more accurate method for analyzing high-field pinning centers. Previous methods did not allow for precise analysis and research on high-field pinning centers, they studied only the dominant pinning mechanism, and they required a maximum of pinning force (F pmax) to analyze pinning centers. The main advantage of this method can be used in samples without the maximum pinning force required by other methods to analyze the pinning mechanism. In addition, this method allows us to observe even small changes in the density of individual pinning centers. This method is based on analysis of critical current density values in different ranges of reduced magnetic field. The method of analysis of highfield pinning centers allows primarily to develop methods and directions for creation of high-field pinning centers. The surface pinning centers are strong pinning centers in low magnetic fields and very weak pinning centers in middle and high magnetic fields. Additionally, the analysis of pinning centers shows that dislocations, strains, substitutions in the crystal lattice, and precipitation inside the grains create strong pinning centers in high magnetic fields and very weak pinning centers in low and middle magnetic fields. Research indicates that strains, substitutions in the crystal lattice, and precipitates inside grains form pinning centers that operate in the high magnetic field range.

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Section: Fabrication Of Nbti Wires Mgb 2 Wires and Methods Of J C Mementioning

confidence: 99%

Analysis Method of High-Field Pinning Centers in NbTi Wires and MgB2 Wires

Gajda

2018

J Low Temp Phys

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“…The wires were fabricated to a diameter of 0.63 mm, achieving a fill factor of 15%. All wires were annealed in isostatic pressure at the Institute of High Pressure Research in Warsaw [16]. The HIP was a two-step process: isostatic pressure is first applied and then the wire sample is ramped to the set annealing temperature.…”

Section: Preparation Of Samplesmentioning

confidence: 99%

Evidence of Point Pinning Centers in Un-Doped Mgb2 Wires at 20 K after HIP Process

Gajda¹,

Morawski²,

Zaleski³

et al. 2016

J Material Sci Eng

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In this paper we present results of transport critical current density (J c ) at 20 K and 4.2 K, irreversible magnetic field (B irr ), upper critical field (B c2 ), critical temperature (T c ), pinning force (F p ), scanning pinning force scaling results (F p /F pmax and B/B irr ) and electron microscope (SEM) images of un-doped MgB 2 wires of 0.63 mm diameter. All wires were annealed at pressures ranging from 0.1 MPa to 1 GPa for 15 min between 680°C to 740°C. SEM images show that 1 GPa pressure yields small grains, higher MgB 2 material density, and small voids. The results obtained by a physical properties measurement system (PPMS) show that high pressure (1 GPa) and 700°C annealing slightly decreases T c above 27 K and increases T c and B irr below 25 K. Un-doped MgB 2 wire annealed in 1 GPa for 15 min at 680°C at has a 20 K, 4.5 T J c of 100 A/mm 2 in and a B irr of 7 T. At 4.2 K, this wire has J c of 100 A/mm 2 at 10.5 T. Scaling results show that the dominant pinning mechanism is point pinning for undoped MgB 2 wires under 1 GPa pressure and annealed at 680°C (at 20 K).

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“…The longitudinal section allows for the best analysis of factors that significantly influence the engineering critical current density and n-value, e.g., connections between grains and homogeneity of the structure. The results indicate that the synthesis reaction in the sample from A to C is in the liquid state of Mg [9,10]. 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.…”

Section: Analysis Of the Structure Of Mgb 2 Materialsmentioning

confidence: 89%

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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Improvement of critical properties of undoped, multifilamentary MgB₂wires in Nb/Cu after annealing under high gas pressure

Cited by 19 publications

References 8 publications

Analysis Method of High-Field Pinning Centers in NbTi Wires and MgB2 Wires

Analysis Method of High-Field Pinning Centers in NbTi Wires and MgB2 Wires

Evidence of Point Pinning Centers in Un-Doped Mgb2 Wires at 20 K after HIP Process

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

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Improvement of critical properties of undoped, multifilamentary MgB2wires in Nb/Cu after annealing under high gas pressure

Cited by 19 publications

References 8 publications

Analysis Method of High-Field Pinning Centers in NbTi Wires and MgB2 Wires

Analysis Method of High-Field Pinning Centers in NbTi Wires and MgB2 Wires

Evidence of Point Pinning Centers in Un-Doped Mgb2 Wires at 20 K after HIP Process

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

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Improvement of critical properties of undoped, multifilamentary MgB₂wires in Nb/Cu after annealing under high gas pressure