Fabrication of binary FeSe superconducting wires by novel diffusion process

We report successful fabrication of multi- and mono-core FeSe wires with high transport critical current density Jc using a simple in-situ Fe-diffusion process based on the powder-in-tube (Fe-diffusion PIT) method. The seven-core wire showed transport Jc of as high as 1027 A/cm2 at 4.2 K. The superconducting transition temperature Tczero was observed at 10.5 K in the wire-samples, which is about 2 K higher than that of bulk FeSe. The Fe-diffusion PIT method is suitable for fabricating multi-core wires of the binary FeSe superconductors with superior properties.Comment: 14 pages, 5 figure

Superconductivity in oxygen-annealed FeTe1-xSx single crystal

We investigated the S-doping-driven phase transition from antiferromagnetic to superconducting in FeTe1-xSx single crystals. The partial substitution of Te by S suppresses antiferromagnetism in Fe-square lattice. Superconductivity is induced by oxygen annealing for only FeTe1-xSx in which the long-range magnetic ordering is suppressed. To realize superconductivity in FeTe1-xSx, both S concentration enough to suppress antiferromagnetism and oxygen annealing are required. Anisotropy of superconductivity in oxygen-annealed FeTe0.886S0.114 was estimated to be 1.17.Comment: 14 pages, 7 figure

Enhancement of superconducting properties in FeSe wires using a quenching technique

Enhancements of superconducting properties were observed in FeSe wires using a quenching technique. Zero resistivity was achieved at about 10 K in quenched wires, which is about 2 K higher than that of polycrystalline FeSe bulk. Furthermore, transport Jc of quenched wires showed three times higher than that of furnace-cooled wires. In contrast, the quenched polycrystalline FeSe bulks did not show the enhancement of Tc. The quenching technique is a greatly promising for fabricating FeSe wires with high Tc and high Jc, and quenched FeSe wires have high potential for superconducting wire applications

Transport properties and microstructure of mono- and seven-core wires of FeSe1-xTex superconductor by Fe-diffusion powder-in-tube method

We report the successful fabrication of mono- and seven-core superconducting wires of FeSe1-xTex using an in-situ Fe-diffusion process based on the powder-in-tube (Fe-diffusion PIT) method. The reacted layer in these wires were found to have composite structure with composition nearly FeSe and FeTe for the inner and outer layers, although a single layer of composition FeSe0.5Te0.5 was supposed to be formed. The self-field transport Jc values at 4.2 K were found to be 226.2 A/cm2 and 100.3 A/cm2 respectively for mono- and seven-core wires. The Jc's of mono- and seven-core wires dropped rapidly at low fields and then showed a gradual decrease with increasing magnetic fields. In addition, the seven-core wire showed higher Jc than the mono-core wire under higher magnetic fields, indicating that the seven-core wire of FeSe1-xTex superconductor using Fe-diffusion PIT method is advantageous for the superconducting-wire application under high magnetic fields.Comment: 19 pages, 6 figure

One-step synthesis of KxFe2-ySe2 single crystals for high critical current density

We have established a simple process that allows for the one-step synthesis of KxFe2-ySe2 single crystals, which exhibit high critical current density Jc. The post annealing and quenching technique has improved the homogeneity of as-grown crystals, resulting in full shielding of the external magnetic field. The quenched crystals show a superconducting transition at Tconset = 32.9 K and Tczero = 32.1 K. The upper critical fields \mu_{0}Hc2(0) for H//ab and H//c are estimated to be ~206 and ~50 T, respectively. The critical current densities Jc for H//ab and H//c reach as high as 1.0\times10^{5} and 3.4\times10^{4} A/cm2 at 5 K. Furthermore, Jc exhibits a high field performance and a significantly weak temperature dependence up to 5 T, suggesting strong pinning. These results demonstrate that KxFe2-ySe2 would be a promising candidate material for practical applications.Comment: 10 pages, 5 figure

Pancreas-preserving partial duodenectomy for non-ampullary duodenal neoplasms: three case reports

Abstract Background There are multiple surgical procedures for resecting non-ampullary duodenal neoplasms (NADNs), and the appropriate method is selected depending on the tumor location and diagnosis. We herein report 3 cases of NADNs that were resected using pancreas-preserving partial duodenectomy (PPD). Case reports The first patient, a 73-year-old woman with a circumferential duodenal adenoma in the supra-ampullary duodenum, underwent surgery. After laparotomy, the duodenum proximal to the tumor was confirmed using intraoperative endoscopy and dissected. The duodenum distal to the tumor was dissected under direct visualization, and the specimen was removed. The distal stump of the duodenum was closed, and duodenojejunostomy was performed as described by Billroth II. The tumor was diagnosed as an adenoma 75 mm in size. She was discharged 12 days after surgery without any complications. The second patient, a 48-year-old man, was diagnosed with a neuroendocrine neoplasm (NEN) with a diameter of 14 mm in the supra-ampullary duodenum. Laparoscopic PPD was performed. He was diagnosed with NEN G1 and discharged the 11th day after surgery. The third patient, a 71-year-old man with a 0–Is + IIa lesion in the horizontal duodenum, underwent surgery. After laparotomy, the horizontal duodenum and proximal jejunum were resected, and duodenojejunostomy was performed. The patient was diagnosed with stage I adenocarcinoma and discharged on the 15th day after surgery. Conclusion PPD is useful for avoiding the morbidity of pancreatoduodenectomy in the management of NADNs without invasion to the ampulla of Vater or pancreas