Publications (9)11.54 Total impact
-
Article: Effects of the Size of the Doped SiC Nanoparticles on the Critical Current Density of the Ti-Sheathed MgB Superconducting Wires
[show abstract] [hide abstract]
ABSTRACT: The effects of the grain size of the doped SiC nanoparticles on the critical current density ( J <sub>c</sub>) of the Ti-sheathed MgB<sub>2</sub> superconducting wires were studied. The concentration of the SiC dopant was 10% and the sizes of the SiC particles were 20 nm, 45 nm, and 123 nm. Contrary to the J <sub>c</sub> results reported on the SiC-doped Fe-sheathed MgB<sub>2</sub> wires, we found that the J <sub>c</sub> for the Ti-sheathed MgB<sub>2</sub> wires decreased with the size of the SiC particles. We also found that the J <sub>c</sub> is greater than that of the undoped MgB<sub>2</sub> wires only for the wires with 123 nm SiC size. This unusual dependence of J <sub>c</sub> on the size of the SiC dopant is discussed in association with the results from the magnetization, electrical resistivity, x-ray diffraction, and transmission electron microscopy measurements.IEEE Transactions on Appiled Superconductivity 07/2011; · 1.04 Impact Factor -
Article: In-Field Enhancement on Ti-Sheathed Wires Doped With TiC Nanoparticles
[show abstract] [hide abstract]
ABSTRACT: Ti-sheathed MgB<sub>2</sub> wires doped with different amount of TiC nanoparticles were investigated. X-ray diffraction pattern suggested the existence of TiC<sub>0.59</sub> phase and carbon incorporation into MgB<sub>2</sub> lattice to form Mg(B<sub>1-x</sub>C<sub>x</sub>)<sub>2</sub>. Strong enhancement of in-field current carrying capability was observed on 2.5% TiC doped sample. The temperature effect was also studied. It was found that 850<sup>deg</sup>C was the optimized annealing temperature.IEEE Transactions on Appiled Superconductivity 07/2009; · 1.04 Impact Factor -
Article: Effects of Thermal Neutron Irradiation and Oxygen on Ti-Sheathed Wires
[show abstract] [hide abstract]
ABSTRACT: The effects of thermal neutron irradiation and excess oxygen on the properties of Ti-sheathed MgB<sub>2</sub> wires were investigated separately in this paper. No significant influence was observed when thermal neutron irradiation with fluence levels of 1.23 times 10<sup>14</sup> and 5.75 times 10<sup>14</sup> cm<sup>-2</sup> were applied on the sample, while fluence level of 3.16 times 10<sup>15</sup> cm<sup>-2</sup> provided a strong suppression of in-field critical current density. Excess oxygen in sample preparation process had negative effect on the properties of the MgB<sub>2</sub> wires. The samples prepared in air possessed lower critical temperature and in-field current carrying capability in comparison with the sample prepared in glove box.IEEE Transactions on Appiled Superconductivity 07/2009; · 1.04 Impact Factor -
Article: Behavior of a 14 cm Bore Solenoid With Multifilament Tape
[show abstract] [hide abstract]
ABSTRACT: The properties of MgB<sub>2</sub> have the potential to make this material a viable solution for applications in which temperature, costs or weight are considered relevant constraints. In order to realize large scale applications, it is important to investigate the material, but also the winding process for MgB<sub>2</sub> wires and tapes. In the literature small coils have already demonstrated central magnetic flux density above 2 Tesla, overcoming common winding problems related to MgB<sub>2</sub> wires. In this current research, efforts are being made in order to improve the performance of solenoid coils, which are of particular interest for many applications, e.g. for space propulsion systems such as the VASIMR engine. A number of coils with MgB<sub>2</sub> tapes are being built. In this paper we present results of the test of a 14 cm bore solenoid wound with 400 meters of multifilament, copper stabilized tape. The magnet was tested in a cryocooled vacuum chamber and it reached 175 A at 16 K with a central B<sub>0</sub> of 1 Tesla.IEEE Transactions on Appiled Superconductivity 07/2007; · 1.04 Impact Factor -
Article: Negative effects of crystalline-SiC doping on the critical current density in Ti-sheathed MgB2(SiC)y superconducting wires
[show abstract] [hide abstract]
ABSTRACT: Ti-sheathed MgB2 wires doped with nanosize crystalline-SiC up to a concentration of 15 wt% SiC have been fabricated, and the effects of the SiC doping on the critical current density (Jc) and other superconducting properties studied. In contrast with the previously reported results that nano-SiC doping with a doping range below 16 wt% usually enhances Jc, particularly at higher fields, our measurements show that SiC doping decreases Jc over almost the whole field range from 0 to 7.3 T at all temperatures. Furthermore, it is found that the degradation of Jc becomes stronger at higher SiC doping levels, which is also in sharp contrast with the reported results that Jc is usually optimized at doping levels near 10 wt% SiC. Our results indicate that these negative effects on Jc could be attributed to the absence of significant effective pinning centres (mainly Mg2Si) due to the high chemical stability of the crystalline-SiC particles.Superconductor Science and Technology 06/2007; 20(7):697. · 2.66 Impact Factor -
Article: Development of Ti-sheathed MgB2 wires with high critical current density
[show abstract] [hide abstract]
ABSTRACT: Working towards developing lightweight superconducting magnets for future space and other applications, we have successfully fabricated mono-core Ti-sheathed MgB2 wires by the powder-in-tube method. The wires were characterized by magnetization, electrical resistivity, x-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry measurements. The results indicate that the Ti sheath does not react with the magnesium and boron, and the present wire rolling process can produce MgB2 wires with a superconducting volume fraction of at least 64% in the core. Using the Bean model, it was found that at 5 K, the magnetic critical current densities, Jc, measured in magnetic fields of 0, 5, and 8 T are about 4.2 × 105, 3.6 × 104, and 1.4 × 104 A cm−2, respectively. At 20 K and 0 T, the magnetic Jc is about 2.4 × 105 A cm−2. These results show that at zero and low fields, the values of the magnetic Jc for Ti-sheathed MgB2 wires are comparable with the best results available for the Fe-sheathed MgB2 wires. At high fields, however, the Jc for Ti-sheathed MgB2 wires appears higher than that for the Fe-sheathed MgB2 wires.Superconductor Science and Technology 10/2006; 19(11):1146. · 2.66 Impact Factor -
Article: High critical current of Cu-sheathed MgB2 wire at 20 K
[show abstract] [hide abstract]
ABSTRACT: For large-scale electric power applications of MgB<sub>2</sub> wire, especially at AC environments, development of nonmagnetic sheath material is essential. In this study, Cu-sheathed MgB<sub>2</sub> wire was fabricated using the powder-in-tube method and ultra-fine Mg and B precursor prepared by high-energy ball milling. Lowering the annealing temperature and shortening the annealing time effectively limit the reaction between Mg and Cu. Critical current density of the wire annealed at 700°C for 5 minutes is 4.3×10<sup>4</sup> A/cm<sup>2</sup> at 20 K and self-field. Adding excess Mg in precursor further enhances critical current to 250 A at 20 K and self-field. These results demonstrate the potential of Cu-sheathed MgB<sub>2</sub> wires for large-scale applications.IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor -
Article: Effects of MgO impurities and micro-cracks on the critical current density of Ti-sheathed MgB2 wires
[show abstract] [hide abstract]
ABSTRACT: Ti-sheathed monocore MgB2 wires with improved magnetic critical current density (Jc) have been fabricated by in situ powder-in-tube (PIT) method and characterized by magnetization, X-ray diffraction, scanning electron microscopy and electrical resistivity measurements. For the best wire, the magnetic Jc values at 5 K and fields of 2 T, 5 T, and 8 T are 4.1 × 105 A/cm2, 7.8 × 104 A/cm2, and 1.4 × 104 A/cm2, respectively. At 20 K and fields of 0.5 T and 3 T, the Jc values are about 3.6 × 105 A/cm2 and 3.1 × 104 A/cm2, respectively, which are much higher than those of the Fe-sheathed mono-core MgB2 wires fabricated with the same in situ PIT process and under the same fabricating conditions. It appears that the overall Jc for the average Ti-sheathed wires is comparable to that of the Fe-sheathed wires. Our X-ray diffraction and scanning electron microscopy analysis indicates that Jc in the Ti-sheathed MgB2 wires can be strongly suppressed by MgO impurities and micro-cracks.Physica C: Superconductivity. -
Article: Phase formation in Cu-sheathed MgB2 wires
[show abstract] [hide abstract]
ABSTRACT: The phases in Cu sheathed MgB2 wires fabricated using very short annealing time are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and critical current (Ic) measurements. By comparison with the XRD pattern of our synthesized MgCu2, the XRD line located at 2θ ≈ 36.1° for all Cu-sheathed MgB2 wire samples is unambiguously identified to be due to the MgCu2 phase. This line was previously unidentifiable due to its absence in the standard pattern of MgCu2 recorded in the current powder diffraction file (PDF) database. We found that the XRD lines previously attributed to Cu atoms by other groups, are actually due to the CuMgδ (with δ ≈ 6%) phase, indicating that copper does not exist in the form of un-reacted atoms in the core materials of these Cu-sheath MgB2 wires. For samples heat treated at 700 °C or below, the phases are basically the superconducting MgB2 and impurity MgCu2 phases. Quantitative analysis indicates that the molar percent of the MgB2 phase in these samples is over 90%. For samples heat treated at 725 °C or above, two additional phases, CuMgδ and MgB4 phases, are also present. The content of CuMgδ phase increases rapidly with the increase of the heat treatment temperature from 725 °C and 750 °C. This increase in CuMgδ content is one of the factors responsible for the dramatic decrease of Ic. These phase identification results are consistent with our SEM result and the published Cu–Mg phase diagram. It is also found that the variation of the MgB2 fraction with the heat treatment temperature peaks at 700 °C, well correlated to the variation trend of Ic with heat treatment temperature.Physica C Superconductivity 442(2):113-123. · 1.01 Impact Factor
Top co-authors
Top Journals
Institutions
-
2006–2011
-
Sam Houston State University
- Department of Physics
Huntsville, TX, USA
-
-
2005–2007
-
University of Houston
- Department of Mechanical Engineering
Houston, TX, USA
-
