R. Tournier - Academia.edu (original) (raw)
Papers by R. Tournier
Physica C: Superconductivity, 2004
Scanning Hall probe round robin measurements of the trapped field of two CFRF-clad, epoxy resin-r... more Scanning Hall probe round robin measurements of the trapped field of two CFRF-clad, epoxy resin-reinforced large grain samples of SmBaCuO fabricated at ISTEC-SRL by top seeded melt growth (TSMG) have been performed by five European laboratories over a two year ...
Physica C: Superconductivity, 1994
Critical current densities Jc(0,H) of magnetically melt-textured YBCO single domains have been me... more Critical current densities Jc(0,H) of magnetically melt-textured YBCO single domains have been measured at T = 77 K for various magnetic field amplitudes and 0 angles of the field H with the ab plane. For 0 < 0c ab, Jc scales better with the 2d model than with other models. In high maanetic fields, for o .... s/lab s//fib . . 0c ab < 0 < 72 , Jc =s ent=rely determined by the scahng parameter H/Hc3 , where H~3 (0) Ls the thtrd critical field of an anisotropic superconductor for intrinsic surfaces parallel to the ab planes. In the 72 ° < 0 < 90 ° angular range, Jc is determined by twin planes which play the role of surfaces for nucleation of superconductivity.
Physica C: Superconductivity, 2006
The phase evolution during melting and recrystallization of ceramic core in Ag-sheathed (Bi,Pb)-2... more The phase evolution during melting and recrystallization of ceramic core in Ag-sheathed (Bi,Pb)-2223 monofilamentary tape has been studied. The tape was fabricated by PIT process with powders containing nearly pure (Bi,Pb)-2223 phase. Short samples were melted at 805ºC, 808ºC, 812ºC, 816ºC and 831ºC, slowly cooled down at 1.5ºC/hr. and quenched in air at room temperature. X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) were applied for the phase identification. XRD patterns of samples show that (Bi,Pb)-2223 core is partially melted at 805ºC, 808ºC, 812ºC, and well reformed directly from the melt during the slow cooling. More (Bi,Pb)-2223 phase is decomposed at temperatures higher than 816ºC and can not recrystallize, indicating that a partial melting at some temperatures around a given temperature range is essential for (Bi,Pb)-2223 phase reformation. The results of EDS analysis show that the melt composition moves from that between "2223" and "2212" stoichiometries towards 2212-like stoichiometry with increasing temperature, and Bi-containing 2:1 phase is the main secondary phase. This seems to lead to the conclusion that (Bi,Pb)-2223 phase decomposes incongruently into a 2212-like liquid and (Ca,Sr)-cuprates. 2:1 phase plays the most important role in (Bi,Pb)-2223 meltrecrystallization process. Our results also reveal that plate-like shape (Bi,Pb)-2223 grains can be obtained via melting and recrystallization if the optimum processing conditions are used.
Physica C: Superconductivity, 2004
Scanning Hall probe round robin measurements of the trapped field of two CFRF-clad, epoxy resin-r... more Scanning Hall probe round robin measurements of the trapped field of two CFRF-clad, epoxy resin-reinforced large grain samples of SmBaCuO fabricated at ISTEC-SRL by top seeded melt growth (TSMG) have been performed by five European laboratories over a two year ...
Physica C: Superconductivity, 1994
ABSTRACT
Physica C: Superconductivity, 1994
Autostable passive magnetic beatings using permanent magnets and superconducting oxides is one of... more Autostable passive magnetic beatings using permanent magnets and superconducting oxides is one of the most promising high Tc superconducting short term applications. The characterization of superconducting samples is essential to design properly these bearings. This paper reports experimental results about vertical forces and stiffness, trapped field and magnetization for magnetically textured YBaCuO pellets.
Materials Science and Engineering: B, 1998
The growth of large top seeded YBaCuO single-domain has been studied by means of in situ video re... more The growth of large top seeded YBaCuO single-domain has been studied by means of in situ video recording during the process. The growth for samples (a <4 cm), textured under a thermal gradient, follows a model based on yttrium diffusion through the melt. The growth appears to be limited (3 x 3 cm2) for an isothermal texturation whereas single-domains up to 7 cm are grown using whether a radial thermal gradient or a overheating process. 0 1998 Elsevier Science S.A. All rights reserved.
Journal of Magnetism and Magnetic Materials, 2001
Journal of Magnetism and Magnetic Materials, 1997
The solidification of molten alloys in a static magnetic field is proposed as a new way of orient... more The solidification of molten alloys in a static magnetic field is proposed as a new way of orienting polycrystalline materials. A high degree of orientation is obtained with samarium-cobalt compounds solidified in a static magnetic field. Whatever the cooling condition used from the liquid state, a magnetic field of several tesla induces crystallographic orientation in the solid. The easy magnetization
Journal of Low Temperature Physics, 1987
We present new results obtained by simultaneous magnetization and resistance measurements on a Ho... more We present new results obtained by simultaneous magnetization and resistance measurements on a HoMo6S 8 single crystal, in the whole temperature range 30 mK ~< T ~< 4.2 K and for several orientations of the easy magnetization axis with respect to the applied field. Field-induced superconductive transitions are observed in the ferromagnetic state of that re-entrant superconductor. They are described as the first experimental realization of an electromagnetic effect earlier suggested by Ginzburg, which requires a negligible effect of the exchange field. Our results concerning the anisotropy of H¢2 are consistent with that requirement. We also notice the possible existence of Ising wall superconductivity in HoMorSs.
IEEE Transactions on Appiled Superconductivity, 1993
ABSTRACT
The European Physical Journal Applied Physics, 1998
We study the limitation possibilities of bulk Bi high T_c materials. For this we test these mater... more We study the limitation possibilities of bulk Bi high T_c materials. For this we test these materials with a.c. or d.c. currents above their critical currents. We study particularly the evolution of the voltage with time or with current. The material, the value of the current and the time duration play important parts. For sintered Bi samples the voltage depends
Susceptibility measurements on MoFe spin-glasses show the validity of the scaling laws down to 0.... more Susceptibility measurements on MoFe spin-glasses show the validity of the scaling laws down to 0.05 K. The specific heat and the electrical resistivity are furthermore quantitatively strongly modified by a magnetic field. However, the general behaviour is not altered (i.e. the C/ T maxima remain unchanged). No effect of “field cooling” treatments on the specific heat has been detected.
Physica C: Superconductivity, 2004
Scanning Hall probe round robin measurements of the trapped field of two CFRF-clad, epoxy resin-r... more Scanning Hall probe round robin measurements of the trapped field of two CFRF-clad, epoxy resin-reinforced large grain samples of SmBaCuO fabricated at ISTEC-SRL by top seeded melt growth (TSMG) have been performed by five European laboratories over a two year ...
Physica C: Superconductivity, 1994
Critical current densities Jc(0,H) of magnetically melt-textured YBCO single domains have been me... more Critical current densities Jc(0,H) of magnetically melt-textured YBCO single domains have been measured at T = 77 K for various magnetic field amplitudes and 0 angles of the field H with the ab plane. For 0 < 0c ab, Jc scales better with the 2d model than with other models. In high maanetic fields, for o .... s/lab s//fib . . 0c ab < 0 < 72 , Jc =s ent=rely determined by the scahng parameter H/Hc3 , where H~3 (0) Ls the thtrd critical field of an anisotropic superconductor for intrinsic surfaces parallel to the ab planes. In the 72 ° < 0 < 90 ° angular range, Jc is determined by twin planes which play the role of surfaces for nucleation of superconductivity.
Physica C: Superconductivity, 2006
The phase evolution during melting and recrystallization of ceramic core in Ag-sheathed (Bi,Pb)-2... more The phase evolution during melting and recrystallization of ceramic core in Ag-sheathed (Bi,Pb)-2223 monofilamentary tape has been studied. The tape was fabricated by PIT process with powders containing nearly pure (Bi,Pb)-2223 phase. Short samples were melted at 805ºC, 808ºC, 812ºC, 816ºC and 831ºC, slowly cooled down at 1.5ºC/hr. and quenched in air at room temperature. X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) were applied for the phase identification. XRD patterns of samples show that (Bi,Pb)-2223 core is partially melted at 805ºC, 808ºC, 812ºC, and well reformed directly from the melt during the slow cooling. More (Bi,Pb)-2223 phase is decomposed at temperatures higher than 816ºC and can not recrystallize, indicating that a partial melting at some temperatures around a given temperature range is essential for (Bi,Pb)-2223 phase reformation. The results of EDS analysis show that the melt composition moves from that between "2223" and "2212" stoichiometries towards 2212-like stoichiometry with increasing temperature, and Bi-containing 2:1 phase is the main secondary phase. This seems to lead to the conclusion that (Bi,Pb)-2223 phase decomposes incongruently into a 2212-like liquid and (Ca,Sr)-cuprates. 2:1 phase plays the most important role in (Bi,Pb)-2223 meltrecrystallization process. Our results also reveal that plate-like shape (Bi,Pb)-2223 grains can be obtained via melting and recrystallization if the optimum processing conditions are used.
Physica C: Superconductivity, 2004
Scanning Hall probe round robin measurements of the trapped field of two CFRF-clad, epoxy resin-r... more Scanning Hall probe round robin measurements of the trapped field of two CFRF-clad, epoxy resin-reinforced large grain samples of SmBaCuO fabricated at ISTEC-SRL by top seeded melt growth (TSMG) have been performed by five European laboratories over a two year ...
Physica C: Superconductivity, 1994
ABSTRACT
Physica C: Superconductivity, 1994
Autostable passive magnetic beatings using permanent magnets and superconducting oxides is one of... more Autostable passive magnetic beatings using permanent magnets and superconducting oxides is one of the most promising high Tc superconducting short term applications. The characterization of superconducting samples is essential to design properly these bearings. This paper reports experimental results about vertical forces and stiffness, trapped field and magnetization for magnetically textured YBaCuO pellets.
Materials Science and Engineering: B, 1998
The growth of large top seeded YBaCuO single-domain has been studied by means of in situ video re... more The growth of large top seeded YBaCuO single-domain has been studied by means of in situ video recording during the process. The growth for samples (a <4 cm), textured under a thermal gradient, follows a model based on yttrium diffusion through the melt. The growth appears to be limited (3 x 3 cm2) for an isothermal texturation whereas single-domains up to 7 cm are grown using whether a radial thermal gradient or a overheating process. 0 1998 Elsevier Science S.A. All rights reserved.
Journal of Magnetism and Magnetic Materials, 2001
Journal of Magnetism and Magnetic Materials, 1997
The solidification of molten alloys in a static magnetic field is proposed as a new way of orient... more The solidification of molten alloys in a static magnetic field is proposed as a new way of orienting polycrystalline materials. A high degree of orientation is obtained with samarium-cobalt compounds solidified in a static magnetic field. Whatever the cooling condition used from the liquid state, a magnetic field of several tesla induces crystallographic orientation in the solid. The easy magnetization
Journal of Low Temperature Physics, 1987
We present new results obtained by simultaneous magnetization and resistance measurements on a Ho... more We present new results obtained by simultaneous magnetization and resistance measurements on a HoMo6S 8 single crystal, in the whole temperature range 30 mK ~< T ~< 4.2 K and for several orientations of the easy magnetization axis with respect to the applied field. Field-induced superconductive transitions are observed in the ferromagnetic state of that re-entrant superconductor. They are described as the first experimental realization of an electromagnetic effect earlier suggested by Ginzburg, which requires a negligible effect of the exchange field. Our results concerning the anisotropy of H¢2 are consistent with that requirement. We also notice the possible existence of Ising wall superconductivity in HoMorSs.
IEEE Transactions on Appiled Superconductivity, 1993
ABSTRACT
The European Physical Journal Applied Physics, 1998
We study the limitation possibilities of bulk Bi high T_c materials. For this we test these mater... more We study the limitation possibilities of bulk Bi high T_c materials. For this we test these materials with a.c. or d.c. currents above their critical currents. We study particularly the evolution of the voltage with time or with current. The material, the value of the current and the time duration play important parts. For sintered Bi samples the voltage depends
Susceptibility measurements on MoFe spin-glasses show the validity of the scaling laws down to 0.... more Susceptibility measurements on MoFe spin-glasses show the validity of the scaling laws down to 0.05 K. The specific heat and the electrical resistivity are furthermore quantitatively strongly modified by a magnetic field. However, the general behaviour is not altered (i.e. the C/ T maxima remain unchanged). No effect of “field cooling” treatments on the specific heat has been detected.