We report experimental discovery of tantalum polyhydride superconductor.It was synthesized under highpressure and high-temperature conditions using diamond anvil cell combined with in situ high-pressure laser heating ...We report experimental discovery of tantalum polyhydride superconductor.It was synthesized under highpressure and high-temperature conditions using diamond anvil cell combined with in situ high-pressure laser heating techniques.The superconductivity was investigated via resistance measurements at pressures.The highest superconducting transition temperature T_(c)was found to be~30 K at 197 GPa in the sample that was synthesized at the same pressure with~2000 K heating.The transitions are shifted to low temperature upon applying magnetic fields that support the superconductivity nature.The upper critical field at zero temperatureμ_0H_(c2)(0)of the superconducting phase is estimated to be~20 T that corresponds to Ginzburg-Landau coherent length~40 A.Our results suggest that the superconductivity may arise from 143d phase of TaH_(3).It is,for the first time to our best knowledge,experimental realization of superconducting hydrides for the VB group of transition metals.展开更多
In this work,a novel friction stir diffusion bonding(FSDB)method was proposed to eliminate hook when joining thin sheets.Three tools,with several convex-vortex pins were innovatively designed to improve the diffusion ...In this work,a novel friction stir diffusion bonding(FSDB)method was proposed to eliminate hook when joining thin sheets.Three tools,with several convex-vortex pins were innovatively designed to improve the diffusion bonding effect of the lap interface.Results showed that sound joints,excellently bonded at the lap interface and without hook,were obtained.The lap interfaces on the joints welded using the T-tool and F-tool almost remained intact,thereby indicating that they were formed by diffusion bonding.The material flow behavior was also simulated by FLUENT software and the results showed that the material flow along thickness was significantly enhanced by increasing the pin number.The joint welded by the T-tool showed shear fracture mode.Sound bonding was formed at the lap interface when using the F-tool and thus the joint showed tensile fracture.展开更多
Dielectric properties offerrite ceramics have been less reported than their magnetic properties.Ourrecent study indicated that ferrite ceramics with very low dielectric loss tangent can be developed byusing appropriat...Dielectric properties offerrite ceramics have been less reported than their magnetic properties.Ourrecent study indicated that ferrite ceramics with very low dielectric loss tangent can be developed byusing appropriate sintering aids,together with the optimization of other sintering parameters suchas sintering temperature and time duration.Among various candidates of sintering aids,Bi_(2)O_(3)isthe most promising one.It is important to find that the optimized concentration of sintering aid forfull densification is not sufficient to achieve lowest dielectric loss tangent.This short review was aimed to summarize the understanding in microstructural evolution,grain growth,densificationand dielectric properties offerrite ceramics as a function of sintering aid concentration and sinteringparameters,which could be used as a guidance to develop ferrite ceramics with low dielectric losstangents for various applications.展开更多
基金the National Natural Science Foundation of China(Grant No.11921004)the National Key R&D Program of China(Grant Nos.2021YFA1401800 and 2022YFA1402301)+2 种基金Chinese Academy of Sciences(Grant No.XDB33010200)supported by the National Science Foundation Earth Sciences(EAR 1634415)used resources of the Advanced Photon Source,a U.S.Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory(Grant No.DEAC02-06CH11357)。
文摘We report experimental discovery of tantalum polyhydride superconductor.It was synthesized under highpressure and high-temperature conditions using diamond anvil cell combined with in situ high-pressure laser heating techniques.The superconductivity was investigated via resistance measurements at pressures.The highest superconducting transition temperature T_(c)was found to be~30 K at 197 GPa in the sample that was synthesized at the same pressure with~2000 K heating.The transitions are shifted to low temperature upon applying magnetic fields that support the superconductivity nature.The upper critical field at zero temperatureμ_0H_(c2)(0)of the superconducting phase is estimated to be~20 T that corresponds to Ginzburg-Landau coherent length~40 A.Our results suggest that the superconductivity may arise from 143d phase of TaH_(3).It is,for the first time to our best knowledge,experimental realization of superconducting hydrides for the VB group of transition metals.
基金supported by the National Natural Science Foundation of China(No.51874201)。
文摘In this work,a novel friction stir diffusion bonding(FSDB)method was proposed to eliminate hook when joining thin sheets.Three tools,with several convex-vortex pins were innovatively designed to improve the diffusion bonding effect of the lap interface.Results showed that sound joints,excellently bonded at the lap interface and without hook,were obtained.The lap interfaces on the joints welded using the T-tool and F-tool almost remained intact,thereby indicating that they were formed by diffusion bonding.The material flow behavior was also simulated by FLUENT software and the results showed that the material flow along thickness was significantly enhanced by increasing the pin number.The joint welded by the T-tool showed shear fracture mode.Sound bonding was formed at the lap interface when using the F-tool and thus the joint showed tensile fracture.
文摘Dielectric properties offerrite ceramics have been less reported than their magnetic properties.Ourrecent study indicated that ferrite ceramics with very low dielectric loss tangent can be developed byusing appropriate sintering aids,together with the optimization of other sintering parameters suchas sintering temperature and time duration.Among various candidates of sintering aids,Bi_(2)O_(3)isthe most promising one.It is important to find that the optimized concentration of sintering aid forfull densification is not sufficient to achieve lowest dielectric loss tangent.This short review was aimed to summarize the understanding in microstructural evolution,grain growth,densificationand dielectric properties offerrite ceramics as a function of sintering aid concentration and sinteringparameters,which could be used as a guidance to develop ferrite ceramics with low dielectric losstangents for various applications.
