The high-entropy alloy(HEA)superconductor,Ta_(1/6)Nb_(2/6)Hf_(1/6)Zr_(1/6)Ti_(1/6)(Ta-Nb-Hf-Zr-Ti),is systematically studied to examine changes in superconducting critical properties,critical temperature(T_(c)),critic...The high-entropy alloy(HEA)superconductor,Ta_(1/6)Nb_(2/6)Hf_(1/6)Zr_(1/6)Ti_(1/6)(Ta-Nb-Hf-Zr-Ti),is systematically studied to examine changes in superconducting critical properties,critical temperature(T_(c)),critical cur-rent density(J_(c)),and upper critical field(H_(c2)),concerning thermal treatment conditions.Annealing condi-tion affects Jc more significantly than T_(c)and H_(c2),with a large improvement of flux pinning force density(F_(p)).The Jc of bare sample is reduced to 10 A cm^(-2)at an applied magnetic field of approximately 1.5 T,whereas the sample annealed at 550℃for 12 h exhibits J_(c)>100 kA cm^(-2)up to around 4 T.Furthermore,the Vickers hardness(HVIT)of the Ta-Nb-Hf-Zr-Ti HEA superconductor notably increases from∼384 to 528 HVIT following a 24-h annealing at 500℃.These results demonstrate that thermal annealing is a powerful process to optimize both the superconducting and mechanical properties of high-entropy alloy superconductors.展开更多
We investigate the effect of ion irradiation on MgB_(2) thin films with small grains of approximately 122 nm and 140 nm.The flux pinning by grain boundaries is insignificant in the pristine MgB_(2) films due to good i...We investigate the effect of ion irradiation on MgB_(2) thin films with small grains of approximately 122 nm and 140 nm.The flux pinning by grain boundaries is insignificant in the pristine MgB_(2) films due to good inter-grain connectivity,but is significantly improved after 120-keV Mn-ion irradiation.The scaling behavior of the flux pinning force density for the ion-irradiated MgB_(2) thin films with nanoscale grains demonstrates the predominance of pinning by grain boundaries,in contrast to the single-crystalline MgB_(2) films where normal point pinning was dominant after low-energy ion irradiation.These results suggest that irradiation-induced defects can accumulate near the grain boundaries in metallic MgB_(2) superconductors.展开更多
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MIST)(Nos.2021R1A2C2010925,RS-2023-00240326,and RS-2023-00220471)Basic Science Research Program through the NRF of Korea funded by the Ministry of Education(Nos.NRF-2019R1F1A1055284 and NRF-2021R1I1A1A01043885).
文摘The high-entropy alloy(HEA)superconductor,Ta_(1/6)Nb_(2/6)Hf_(1/6)Zr_(1/6)Ti_(1/6)(Ta-Nb-Hf-Zr-Ti),is systematically studied to examine changes in superconducting critical properties,critical temperature(T_(c)),critical cur-rent density(J_(c)),and upper critical field(H_(c2)),concerning thermal treatment conditions.Annealing condi-tion affects Jc more significantly than T_(c)and H_(c2),with a large improvement of flux pinning force density(F_(p)).The Jc of bare sample is reduced to 10 A cm^(-2)at an applied magnetic field of approximately 1.5 T,whereas the sample annealed at 550℃for 12 h exhibits J_(c)>100 kA cm^(-2)up to around 4 T.Furthermore,the Vickers hardness(HVIT)of the Ta-Nb-Hf-Zr-Ti HEA superconductor notably increases from∼384 to 528 HVIT following a 24-h annealing at 500℃.These results demonstrate that thermal annealing is a powerful process to optimize both the superconducting and mechanical properties of high-entropy alloy superconductors.
基金the support of the accelerator group and operators of KOMAC (KAERI (C.K.,J.S.))Project supported by the National Research Foundation (NRF)of Korea through a grant funded by the Korean Ministry of Science and ICT (Grant No.2021R1A2C2010925 (T.P.,Y.H.,J.S.))+2 种基金the Basic Science Research Program through the NRF of Korea funded by the Ministry of Education (Grant Nos.NRF-2019R1F1A1055284 (J.M.L.,W.N.K.)and NRF2021R1I1A1A01043885 (S.G.J.,Y.H.))the National Natural Science Foundation of China (Grant Nos.12035019 (J.L.))the Chinese Scholarship Council (CSC)for fellowship support。
文摘We investigate the effect of ion irradiation on MgB_(2) thin films with small grains of approximately 122 nm and 140 nm.The flux pinning by grain boundaries is insignificant in the pristine MgB_(2) films due to good inter-grain connectivity,but is significantly improved after 120-keV Mn-ion irradiation.The scaling behavior of the flux pinning force density for the ion-irradiated MgB_(2) thin films with nanoscale grains demonstrates the predominance of pinning by grain boundaries,in contrast to the single-crystalline MgB_(2) films where normal point pinning was dominant after low-energy ion irradiation.These results suggest that irradiation-induced defects can accumulate near the grain boundaries in metallic MgB_(2) superconductors.
