In this study, conditions for obtaining high-quality superconducting joint to a Gd-Ba-Cu-O bulk superconductor to investigate for the first time the effect of pulse field magnetization (PFM) properties of the joined bulk and to study an effective pulse magnetization method. We fabricated a good superconducting joint using the local melting method with sintered Er-Ba-Cu-O and applied the PFM method to the joined bulk. As a result, a high magnetic field of 1.2 T was trapped in the joined part when the magnetic field strength more than 5 T was applied at 50 K. From the evaluation results of the J _c - B characteristics of each region cut from the joined sample confirmed that the joined sample was efficiently magnetized due to the preferential field penetration path and the dispersion of heat generation from the joined part. This is a finding that could lead to the future use of PFM in the bulk using superconducting joint with minimal reduction of the trapped magnetic field, and could simplify the magnetization method, which has been a drawback of PFM.

The important factors in obtaining a high-quality superconducting joint were investigated for the superconducting joint of a GdBa₂Cu₃O_x (GdBCO) bulk superconductor with sintered ErBa₂Cu₃O_x (ErBCO) using the local melt-growth method. REBCO (RE: rare earth) bulk superconductors can be used as strong magnets by magnetizing them, but they require large bulk sizes for their application. Although the superconducting joint presents a viable solution, many possibilities for property improvement remain, such as property degradation, depending on the joining direction. By varying the joining thermal conditions and confirming the elemental distribution, magnetization properties near the joined part and the effects of these on the joining properties are clarified, and a method for fabricating high-performance joined samples is obtained. Microstructure segregation was rarely observed at the center of the joined part regardless of the joining direction, and the superconducting properties were negligible and small. The J_c-B results are almost identical to those of the GdBCO matrix at a low field, confirming that the joined part minimally interferes with the superconducting current. Furthermore, by lowering the maximum temperature, shortening the holding time at the maximum temperature, and increasing the cooling rate, the region of mutual solid solution was reduced, and the J_c-B under the self-magnetic field was enhanced. These results contribute to the development of the superconducting joining method, a critical aspect of larger bulk superconductors.

The electromagnetic and thermal behavior of pulsed field magnetization (PFM) of a superconducting joined bulk was confirmed in detail by FEM simulations. It was shown that when the joined bulk is magnetized by PFM, the joined part may become the preferential field penetration path due to the difference in superconducting properties between the matrix and the joined part. However, the actual experimental system only observes the behavior of the magnetic field outside the bulk, and the details are largely based on predictions. In the actual experiments, GdBCO was selected as the matrix and ErBCO was selected as the joined part for the superconducting joint. The joined sample was cooled to 50 K and subjected to an applied magnetic field of 5 T in the PFM. FEM simulations were performed to simulate the experiments in this study. By using J _c values derived from actual measurements in the simulations, the magnetic field and thermal behavior were simulated, and it was confirmed that the joined part was the preferential field penetration path as in the experiment. In addition, the magnetic field distribution with and without joining confirms that the local melting method has no effect on the property degradation in increasing the size of the joined bulk. In addition, this system made it possible to confirm the magnetic and thermal behavior even when different REBCO materials are introduced.

The degrading of trapped fields B _T in bulk MgB ₂ superconductor due to the occurrences of flux jumps was investigated. This work presents the method for characterizing the propagation of the magnetic flux in an artificially drilled MgB ₂ bulk superconductor fabricated via spark plasma sintering (SPS). The pulsed field magnetization (PFM) was utilized by studying the effect of applied fields B _A on the bulk MgB ₂ embedded with low melting alloy of Bi-In-Sn alloy and aluminum rods within the holes which improved the thermal property, thereby suppressing the flux jumps caused by the generated heat within the bulk sample. The bulk MgB ₂ sample was redesigned to enhance both the thermal properties and to suppress flux jumps during pulse applications. We discuss the magnetic flux dissipation, the flux motion, and performance by evaluation of the capture field ratio B _T / B _P . We analyzed the field trapping performance of the improvised bulk at high applied fields and compared our findings to the data obtained for the as-received bulk sample for the penetration ratio B _P / B _A and penetrated field B _p . This study helps to solve the flux jump problem in the bulk superconductor resulting from poor heat dissipation. This is an experimental breakthrough that supports existing simulation studies and reports giving way for more prospects for high field applications in the development of bulk MgB ₂ superconductors.

HRTEM study has been carried out on BN nanotubes produced by laser heating of hBN in a diamond anvil cell under high nitrogen pressure of 8.3 GPa. Special attention has been paid to their tip-end capping features and the epitaxial relationship with the mother phase during their growth. The observed tip-end cone angles ranged from 22° to 45 °. The tip-end structural models have been proposed that are relied on the existence of 4 and 8 member BN rings in the nanotube caps instead of 5 and 7 member rings which are typical for carbon nanotubes. The base material in the bottom of the nanotubes mostly revealed cubic BN structure, though, occasionally, hexagonal BN was found as the nanotube mother phase. In the former case, cBN in the bottom of the nanotube and the nanotube //BN sheets exhibit orientation relationship as follows: (110)_cubic//(0002)_hex and [ 1¯11 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003063056/c87f8d57-bd6e-40f8-a651-90760b6f3961/content/ieq0345.tif"/>11]_cubic//[10 101¯0 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003063056/c87f8d57-bd6e-40f8-a651-90760b6f3961/content/ieq0346.tif"/>0]_hex·

Conditions for obtaining high-quality joined bulk superconductors using the local melt-growth method with sintered Er-Ba-Cu-O as the joining material for Gd-Ba-Cu-O melt-grown bulk superconductors and the effect of applying pulse field magnetization （PFM） to the joined superconductor were investigated. The effects of important melting conditions of the local melt-growth method on microstructure and superconducting properties were clarified, and it was confirmed that a lower maximum temperature, shorter holding time at maximum temperature, and faster cooling rate can obtain a good quality microstructure and improve superconducting properties. Next, measurements of magnetic field behaviors when PFM was applied revealed that the joined part of the joined bulk superconductor is the preferential field penetration path. A single peak with a maximum trapped field of 0.52 T was obtained at above 4 mm from the sample magnetized at an applied field of 5.0 T at 50 K by PFM. Finally, the PFM was simulated by FEM analysis to confirm the details of the thermal and magnetic field behavior, which confirmed that the joined part is the preferential field penetration path as in the actual experiment. This could contribute to the development of superconducting joining technology, which is an important key to the technology in the larger bulk superconductors, and could make pulse magnetization an efficient method of magnetization.