The microstructures of melt-spun Nd_135- Fe_81.74B4.76 ribbons have been investigated by means of X-ray diffraction,Mossbauer spectroscopy and HREM.Experimental results show that optimal magnetic properties of the bon...The microstructures of melt-spun Nd_135- Fe_81.74B4.76 ribbons have been investigated by means of X-ray diffraction,Mossbauer spectroscopy and HREM.Experimental results show that optimal magnetic properties of the bond- ed magnet can be obtained by melt-spun alloys at wheel velocity of 24m/s,the microstructure of which was single phase Nd_2Fe_(14)B crystallites,and no other phases,such as Nd-rich,B-rich or x-Fe phase,were present.It is considered that the high intrinsic coercivity ~iH_c can be attributed to the sin- gle-domain behaviour of Nd_2Fe_(14)B crystallite phase.展开更多
The microstructure and defects in melt-textured growth (MTG) YBa2Cu3O7-x (YBCO) bulk material have been studied systematically using high resolution transmission electron microscopy (HREM), and the relationship betwee...The microstructure and defects in melt-textured growth (MTG) YBa2Cu3O7-x (YBCO) bulk material have been studied systematically using high resolution transmission electron microscopy (HREM), and the relationship between the anisotropic critical current density Jc and the microstructure has been explored. The results indicate that there are numerous dense and nonunifonnly-distributed intergrowth-type layered defects orienting parallel to the ab plane in MTG-YBCO. These defects may serve as effective flux pinning centres for H//ab. The layered defects parallel to the ab plane together with the {110} twin boundaries are probably responsible for the anisotiopic behaviour of Jc depending upon the orientation of the external magnetic field.展开更多
Since the discovery of high T_c oxide superconductor, scientists and engineers aredeeply concerned with the possibility of its application to the electric machine withstrong operating current at high magnetic fields. ...Since the discovery of high T_c oxide superconductor, scientists and engineers aredeeply concerned with the possibility of its application to the electric machine withstrong operating current at high magnetic fields. Because of the serious problem ofweak link in the sintered bulk materials processed by regular ceramic powder technolo-gy, the critical current density at 77.3 K is low and it gets much lower with theincreasing magnetic field. Scientists look forward to heighening J_c of the high T_c ma-展开更多
文摘The microstructures of melt-spun Nd_135- Fe_81.74B4.76 ribbons have been investigated by means of X-ray diffraction,Mossbauer spectroscopy and HREM.Experimental results show that optimal magnetic properties of the bond- ed magnet can be obtained by melt-spun alloys at wheel velocity of 24m/s,the microstructure of which was single phase Nd_2Fe_(14)B crystallites,and no other phases,such as Nd-rich,B-rich or x-Fe phase,were present.It is considered that the high intrinsic coercivity ~iH_c can be attributed to the sin- gle-domain behaviour of Nd_2Fe_(14)B crystallite phase.
基金Project supported by the National Center for R & D on Superconductivity of China and the Chinese Academy of Sciences.
文摘The microstructure and defects in melt-textured growth (MTG) YBa2Cu3O7-x (YBCO) bulk material have been studied systematically using high resolution transmission electron microscopy (HREM), and the relationship between the anisotropic critical current density Jc and the microstructure has been explored. The results indicate that there are numerous dense and nonunifonnly-distributed intergrowth-type layered defects orienting parallel to the ab plane in MTG-YBCO. These defects may serve as effective flux pinning centres for H//ab. The layered defects parallel to the ab plane together with the {110} twin boundaries are probably responsible for the anisotiopic behaviour of Jc depending upon the orientation of the external magnetic field.
基金Project supported by the National Center for R & D on Superconductivity of China.
文摘Since the discovery of high T_c oxide superconductor, scientists and engineers aredeeply concerned with the possibility of its application to the electric machine withstrong operating current at high magnetic fields. Because of the serious problem ofweak link in the sintered bulk materials processed by regular ceramic powder technolo-gy, the critical current density at 77.3 K is low and it gets much lower with theincreasing magnetic field. Scientists look forward to heighening J_c of the high T_c ma-
