In this paper, a dc Josephson junction between borocarbide superconductors has been studied theoretically. The s＋g-wave pairing symmetry which is observed in rare earth complex of borocarbides has a huge anisotropy a...In this paper, a dc Josephson junction between borocarbide superconductors has been studied theoretically. The s＋g-wave pairing symmetry which is observed in rare earth complex of borocarbides has a huge anisotropy and is an interesting form of unconventional superconductivity. We calculate the Josephson current in a superconductorinsulator-superconductor （SIS） Josephson junction with s＋g-wave superconducting pairing symmetry. In our planar junction c-axis is parallel to an interface with finite transparency but ab-planes of two tetragonal superconductors are misorientated by angle α. We obtain that the Josephson current is strongly dependent on mis-orientation between the left and the right ab-planes. An insulator sandwiched between two superconductors which acts as a potential barrier is demonstrated by a transparency coefficient. The effects of the potential barrier and the mis-orientation on the current are studied analytically and numerically. Occurrence of 0-θ transition in this s＋g-wave junction is investigated in this paper. A comparison between d-wave Josephson junction and s＋g-wave one is also made in the present paper.展开更多
Here we review recent small-angle scattering studies of the vortex lattice in a range of type-II superconductors carried out by our group. Emphasis is placed on providing examples of the kind of information which can ...Here we review recent small-angle scattering studies of the vortex lattice in a range of type-II superconductors carried out by our group. Emphasis is placed on providing examples of the kind of information which can be obtained by such measurements, focusing in particular on studies of the vortex lattice structure and form factor in LuNi2B2C, TmNi2B2C, CeCoIn5 and Ba（Fe0.93Co0.07）2As2.展开更多
Critical temperature of Mg1-xAlxB2, MgB2-xCx are calculated using two-band Eliashberg theory in intermediate e-ph coupling. Analytical calculations are conducted for different values of doping parameters x in this com...Critical temperature of Mg1-xAlxB2, MgB2-xCx are calculated using two-band Eliashberg theory in intermediate e-ph coupling. Analytical calculations are conducted for different values of doping parameters x in this compounds. Pressure effects on critical temperature in MgB2 and nonmagnetic borocarbide YNi2B2C are also investigated. Results is compared with available experimental data and good agreement is achieved.展开更多
In order to improve the toughness and wear resistance of high-boron medium-carbon alloy （HBMCA）, a novel wear-resistant HBMCA comprising granular borocarbide was obtained by titanium, magnesium, and rare earth modif...In order to improve the toughness and wear resistance of high-boron medium-carbon alloy （HBMCA）, a novel wear-resistant HBMCA comprising granular borocarbide was obtained by titanium, magnesium, and rare earth modifications. These modifications gave rise to greatly refined as-cast eutectic borocarbide structures and a less interconnected continuous borocarbide network. Heat treatment mostly produced broken and spheriodized borocarbides that tended to exist as isolated particles in modified HBMCA. The heat treated modified HBMCA exhibited enhanced hardness than pristine and impact toughness was improved significantly to 12.5 J/cm^2. In addition, it displayed 2.39 and 1.7 times greater wear resistance than high-speed steel （HSS） and high nickel-chromium alloy steel （Cr25） at high temperature （500℃）, respectively. Here, the modification mechanisms involving Re2O3, TiN, and MgO/ MgS heterogeneous nuclei were discussed.展开更多
The Fe-B alloy containing chromium and nickel was prepared, and the microstructure and erosioncorrosion behavior of the alloy were investigated by means of scanning electron microscopy, energy dispersive X-ray spectro...The Fe-B alloy containing chromium and nickel was prepared, and the microstructure and erosioncorrosion behavior of the alloy were investigated by means of scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction analysis, Leica digital image analysis, a hardness tester and an erosioncorrosion tester. Cr28 white cast iron was used for comparison. Results show that the microstructures of both as-cast and heat-treated Fe-B alloys consist of austenite and borocarbide. The nickel and chromium elements are mainly distributed over the matrix and borocarbide, respectively. The hardness of the austenite matrix and the Rockwell hardness of heat-treated Fe-B alloy are higher than those of as-cast Fe-B alloy. In the erosioncorrosion test of the slurry, the erosion-corrosion weight loss of Fe-B alloy is lower than that of Cr28 white cast iron, indicating the Fe-B alloy displays higher erosion-corrosion resistance.展开更多
A vanadium carbide coating on steel’s substrates was prepared through B 4C reducing V 2O 5 in molten salt bath. The thickness of VC-coating reached 14-18μm at 920℃ for 6 h, and the hardness of VC-coating reached HV...A vanadium carbide coating on steel’s substrates was prepared through B 4C reducing V 2O 5 in molten salt bath. The thickness of VC-coating reached 14-18μm at 920℃ for 6 h, and the hardness of VC-coating reached HV2200-HV2400. The sliding wear resistance of the VC-coating is not only 3350 times of that of SCN-coating, but also more excellent than that of other VC-coatings, prepared through aluminum reducing V 2O 5 or through TD processing. The experimental results indicate that the different VC-coating resistances to wear and corrosion increase with a raise of the free carbon contents in VC-coatings. The continuous service life of a tongue grooves of the high speed cigarette machines, with this VC-coating, reached good results of 140-150 days.展开更多
文摘In this paper, a dc Josephson junction between borocarbide superconductors has been studied theoretically. The s＋g-wave pairing symmetry which is observed in rare earth complex of borocarbides has a huge anisotropy and is an interesting form of unconventional superconductivity. We calculate the Josephson current in a superconductorinsulator-superconductor （SIS） Josephson junction with s＋g-wave superconducting pairing symmetry. In our planar junction c-axis is parallel to an interface with finite transparency but ab-planes of two tetragonal superconductors are misorientated by angle α. We obtain that the Josephson current is strongly dependent on mis-orientation between the left and the right ab-planes. An insulator sandwiched between two superconductors which acts as a potential barrier is demonstrated by a transparency coefficient. The effects of the potential barrier and the mis-orientation on the current are studied analytically and numerically. Occurrence of 0-θ transition in this s＋g-wave junction is investigated in this paper. A comparison between d-wave Josephson junction and s＋g-wave one is also made in the present paper.
基金Acknowledgements M.R. Eskildsen was supported by the U. S. National Science Foundation through grant DMR-0804887. Collaboration and stimulating discussions are acknowledged with： A. B. Abrahamsen, T. M. Artemova, E. D. Bauer, A. D. Bianchi, T. D. Blasius, S. L. Bud＇ko, P. C. Canfield, P. Das, L. DeBeer-Schmitt, J. M. Densmore, C. D. Dewhurst, Z. Fisk, E. M. Forgan, J. L. Gavilano, S. Gerber, A. I. Coldman, M. Ichioka, R. Ikeda, N. Jenkins, M. Kenzelmann, V. G. Kogan, J. Kohlbrecher, A. Kreyssig, M. Laver, K. Machida, J. Mesot, R. Movshovich, N. Ni, T. O＇Brien, C. Petrovic, R. Prozorov, K. Rovira, J. L. Sarrao, I. S. Veshchunov, L. Ya. Vinnikov. J. S. White and M. Zolliker.
文摘Here we review recent small-angle scattering studies of the vortex lattice in a range of type-II superconductors carried out by our group. Emphasis is placed on providing examples of the kind of information which can be obtained by such measurements, focusing in particular on studies of the vortex lattice structure and form factor in LuNi2B2C, TmNi2B2C, CeCoIn5 and Ba（Fe0.93Co0.07）2As2.
文摘Critical temperature of Mg1-xAlxB2, MgB2-xCx are calculated using two-band Eliashberg theory in intermediate e-ph coupling. Analytical calculations are conducted for different values of doping parameters x in this compounds. Pressure effects on critical temperature in MgB2 and nonmagnetic borocarbide YNi2B2C are also investigated. Results is compared with available experimental data and good agreement is achieved.
基金Item Sponsored by National Natural Science Foundation of China(51261013)
文摘In order to improve the toughness and wear resistance of high-boron medium-carbon alloy （HBMCA）, a novel wear-resistant HBMCA comprising granular borocarbide was obtained by titanium, magnesium, and rare earth modifications. These modifications gave rise to greatly refined as-cast eutectic borocarbide structures and a less interconnected continuous borocarbide network. Heat treatment mostly produced broken and spheriodized borocarbides that tended to exist as isolated particles in modified HBMCA. The heat treated modified HBMCA exhibited enhanced hardness than pristine and impact toughness was improved significantly to 12.5 J/cm^2. In addition, it displayed 2.39 and 1.7 times greater wear resistance than high-speed steel （HSS） and high nickel-chromium alloy steel （Cr25） at high temperature （500℃）, respectively. Here, the modification mechanisms involving Re2O3, TiN, and MgO/ MgS heterogeneous nuclei were discussed.
基金financially supported by the National Natural Science Foundation of China under Grant No.51705414the Huozhou Coal Electricity Group Co.,Ltd.of China under Grant No.HZMDJSHT20007
文摘The Fe-B alloy containing chromium and nickel was prepared, and the microstructure and erosioncorrosion behavior of the alloy were investigated by means of scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction analysis, Leica digital image analysis, a hardness tester and an erosioncorrosion tester. Cr28 white cast iron was used for comparison. Results show that the microstructures of both as-cast and heat-treated Fe-B alloys consist of austenite and borocarbide. The nickel and chromium elements are mainly distributed over the matrix and borocarbide, respectively. The hardness of the austenite matrix and the Rockwell hardness of heat-treated Fe-B alloy are higher than those of as-cast Fe-B alloy. In the erosioncorrosion test of the slurry, the erosion-corrosion weight loss of Fe-B alloy is lower than that of Cr28 white cast iron, indicating the Fe-B alloy displays higher erosion-corrosion resistance.
文摘A vanadium carbide coating on steel’s substrates was prepared through B 4C reducing V 2O 5 in molten salt bath. The thickness of VC-coating reached 14-18μm at 920℃ for 6 h, and the hardness of VC-coating reached HV2200-HV2400. The sliding wear resistance of the VC-coating is not only 3350 times of that of SCN-coating, but also more excellent than that of other VC-coatings, prepared through aluminum reducing V 2O 5 or through TD processing. The experimental results indicate that the different VC-coating resistances to wear and corrosion increase with a raise of the free carbon contents in VC-coatings. The continuous service life of a tongue grooves of the high speed cigarette machines, with this VC-coating, reached good results of 140-150 days.
