The critical parameters in <i>in-situ</i> MgB2 wires and tapes with <i>ex-situ</i> MgB2 barrier after hot isostatic pressure, cold drawing, cold rolling and doping

Gajda, D.; Morawski, A.; Zaleski, A.; Häßler, Wolfgang; Nenkov, K.; Rindfleisch, M.; Żuchowska, E.; Gajda, Grzegorz; Czujko, Tomasz; Cetner, T.; Hossain, Md. Shahriar A.

doi:10.1063/1.4919364

Cited by 23 publications

(11 citation statements)

References 36 publications

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“…The shrinking of MgB 2 creates voids and strains. These big voids create low-field pinning centers (surface pinning centers) in the MgB 2 material [25]. In contrast, strains create defects inside the grains.…”

Section: At 20 Kmentioning

confidence: 99%

“…Gajda et al [18] showed for the first time that dislocations effectively increase J c in magnetic fields from 6 to 8 T in NbTi. There are several methods that allow us to obtain high-field pinning centers and more connections between the grains in superconducting wires, tapes, bulks, and thin layers, e.g., cold drawing (CD) [20,[24][25][26], equal-channel multi-angle pressing (ECMAP) [27,28], cold rolling (CR) [25,29], cold pressure (CP) [30], hot isostatic pressure (HIP) [25,31,32], and C doping [33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

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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: At 20 Kmentioning

confidence: 99%

Section: Introductionmentioning

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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“…Livingston indicates that point pinning centers can create dislocations and voids of thickness similar to the coherence length [5]. Our previous research for doped MgB 2 wires shows that the disadvantages of un-doped MgB 2 can be eliminated by annealing a wire under isostatic pressure (HIP) [10][11][12]. HIP creates dislocations, eliminates voids, produces small grains and small normal area, increases connections between grains, and increases the density and homogeneity of the MgB 2 material [13,14].…”

Section: Introductionmentioning

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 samples were annealed at 700°C in argon gas under isostatic pressure for 15 min at the Institute of High Pressure Physics laboratory (Table 1) [17]. Transport (15 Hz and AC current, I AC ¼260 mA) and magnetic (50 mT) measurements were performed using a physical properties measurement system (PPMS Model 7100, Quantum Design,) in the International Laboratory of High Magnetic Fields and Low Temperature [18]. The samples for transport measurements had a length of 12 mm.…”

Section: Introductionmentioning

confidence: 99%