Open Access. Powered by Scholars. Published by Universities.®
- Discipline
Articles 1 - 10 of 10
Full-Text Articles in Engineering
Nanocoating Of Particles For Optimal Doping And Universal Enhancement Of Current-Carrying Ability In "Organic" Mgb2-Xcx Superconductors, Olga V. Shcherbakova, Alexey V. Pan, S X. Dou, Rashmi Nigam, David Wexler
Nanocoating Of Particles For Optimal Doping And Universal Enhancement Of Current-Carrying Ability In "Organic" Mgb2-Xcx Superconductors, Olga V. Shcherbakova, Alexey V. Pan, S X. Dou, Rashmi Nigam, David Wexler
Shi Xue Dou
The universal approach of liquid mixing has been found to produce “organic” MgB2−xCx superconductors with structural and supercurrent-carrying properties unattainable by other techniques. We show by transmission electron microscopy combined with energy dispersive spectroscopy that these unique properties are enabled through coating of boron particles with a nanolayer of carbon. The subsequent reaction between carbon-encapsulated boron and magnesium results in enhanced carbon content x in the crystal lattice, as determined by x-ray diffraction pattern analysis. Among various carbon-containing compounds investigated, polycarbosilane has been found to be the optimal dopant for MgB2 superconductor, producing the largest critical current density due to …
Identification Of Factors Limiting The Critical Current Density In Mgb2 _Xcx Superconductors At Low Magnetic Fields, Olga V. Shcherbakova, Alexey V. Pan, Jianli Wang, Andrey Shcherbakov, S. X. Dou, David Wexler
Identification Of Factors Limiting The Critical Current Density In Mgb2 _Xcx Superconductors At Low Magnetic Fields, Olga V. Shcherbakova, Alexey V. Pan, Jianli Wang, Andrey Shcherbakov, S. X. Dou, David Wexler
Shi Xue Dou
Structural analysis and electromagnetic measurements have been performed on a range of samples prepared by the liquid mixing approach to doping MgB2 are sugar, malic acid, and polycarbosilane. The results obtained have allowed us to clarify the contributions of the factors limiting critical current at low magnetic fields in doped MgB2.
Comparison Of Small-Field Behaviour In Mgb2, Low And High Temperature Superconductors, Alexey V. Pan, S X. Dou
Comparison Of Small-Field Behaviour In Mgb2, Low And High Temperature Superconductors, Alexey V. Pan, S X. Dou
Shi Xue Dou
Different types of superconductors have been investigated at small magnetic fields (Ba) over wide temperature (T) ranges at different Ba orientations. It has been shown that the temperature dependence of the characteristic field (B*), separating the Ba-independent critical current density (Jc) plateau (single vortex pinning regime) and the region with Jc(Ba) (collective pinning), can be attributed either to the temperature dependence of the magnetic penetration depth for Nb-film and MgB2bulk superconductors, or to thermally activated processes for Bi-based superconductors and YBa2Cu3O7−δ superconducting films. In both cases the vortex pinning influence appears to have a secondary role, affecting the effective vortex …
Peak Effect In The Critical Current Of Type Ii Superconductors With Strong Magnetic Vortex Pinning, X B. Xu, H Fangohr, X N. Xu, M Gu, Z H Wang, S M. Ji, Shichao Ding, Dongqi Shi, S. X. Dou
Peak Effect In The Critical Current Of Type Ii Superconductors With Strong Magnetic Vortex Pinning, X B. Xu, H Fangohr, X N. Xu, M Gu, Z H Wang, S M. Ji, Shichao Ding, Dongqi Shi, S. X. Dou
Shi Xue Dou
We perform 2D Langevin simulations studying the peak effect (PE) of the critical current taking into account the temperature dependence of the competing forces. We observe and report that the PE results from the competition of vortex-vortex interactions and vortex-pin interactions which have different temperature dependencies. The simulations reveal that the PE can take place only for certain pinning strengths, densities of pinning centres, and driving forces, which is in good agreement with experiments. No apparent vortex order-disorder transition is observed across the PE regime. In addition, the PE is a dynamical phenomenon, and thermal fluctuations can speed up the …
Benzoic Acid Doping To Enhance Electromagnetic Properties Of Mgb2 Superconductors, W. X. Li, Y. Li, M. Y. Zhu, R. H. Chen, X. Xu, W. K. Yeoh, J. H. Kim, S. X. Dou
Benzoic Acid Doping To Enhance Electromagnetic Properties Of Mgb2 Superconductors, W. X. Li, Y. Li, M. Y. Zhu, R. H. Chen, X. Xu, W. K. Yeoh, J. H. Kim, S. X. Dou
Shi Xue Dou
The effect of benzoic acid doping on lattice parameters, microstructure, critical temperature (T-c), critical current density (J(c)) and flux pinning force of MgB2 has been studied. In this work we used benzoic acid as an example of aromatic acids as an additive to MgB2. For different sintering process, actual carbon (C) substitution for boron (B) was estimated to be from 3.5 at% to 5.0 at% of B while T-c dropped about 2-4 K. The advantages of aromatic acid doping include homogeneous mixing of precursor powders, avoidance of expansive nano-additives, production of highly reactive C and significant enhancement in J(c) of …
Flux Dynamics In (Y, Nd)1ba2cu3o7 Superconductors, A S Mahmoud, Josip Horvat, S X. Dou
Flux Dynamics In (Y, Nd)1ba2cu3o7 Superconductors, A S Mahmoud, Josip Horvat, S X. Dou
Shi Xue Dou
The vortex dynamics of (Y, Nd)Ba2Cu3O7−δ ((Y, Nd)123) superconductors have been studied using magnetic relaxation measurements obtained at different sweep rates. The temperature dependence of the dynamic relaxation rate (Q) is found to be not vanishing at T = 0 K, and also showed well developed maxima becoming broader and tending to move to higher temperatures with decreasing magnetic field. At temperatures close to the critical temperature (T c ), Q(T) showed well-developed minima becoming deeper and tending to move to lower temperatures with increasing field. These minima appeared to occur approximately at the same reduced temperature position [ T/T …
Vortex Dynamics For Low- Type-Ii Superconductors, X B Xu, H Fangohr, Z H Wang, M Gu, S.L. Liu, Dongqi Shi, S. X. Dou
Vortex Dynamics For Low- Type-Ii Superconductors, X B Xu, H Fangohr, Z H Wang, M Gu, S.L. Liu, Dongqi Shi, S. X. Dou
Shi Xue Dou
Based on a model appropriate for “marginally type-II” superconducting system, we study the dynamics of vortices with competing interactions by Langevin dynamics simulation. In addition to pinned states and plastic flow, we find that the moving vortex system forms ordered bubble configurations and stripe structures, depending on pinning strength and driving force. The vortex system exhibits a marked hysteresis in its velocity-force characteristic, which results from a dynamical stripe reordering due to intervortex attraction.
Magnetic Field Processing To Enhance Critical Current Densities Of Mgb2 Superconductors, S X. Dou, Wai Kong Yeoh, Olga V. Shcherbakova, Josip Horvat, Jung Ho Kim, Alexey V. Pan, David Wexler, Yongqing Li, W X. Li, Z M. Ren, Paul G. Munroe, J Z. Cui
Magnetic Field Processing To Enhance Critical Current Densities Of Mgb2 Superconductors, S X. Dou, Wai Kong Yeoh, Olga V. Shcherbakova, Josip Horvat, Jung Ho Kim, Alexey V. Pan, David Wexler, Yongqing Li, W X. Li, Z M. Ren, Paul G. Munroe, J Z. Cui
Shi Xue Dou
A magnetic field of up to 12T was applied during the sintering process of pure MgB2 and carbon nanotube(CNT)dopedMgB2wires. The authors have demonstrated that magnetic field processing results in grain refinement, homogeneity, and enhancement in Jc(H) and Hirr. The extent of improvement in Jc increases with increasing field. The Jc for a 10T field processed CNTdoped sample increases by a factor of 3 at 10K and 8T and at 20K and 5T, respectively. Hirr for the 10T field processed CNTdoped sample reached 9T at 20K, which exceeded the best value of SiC dopedMgB2 at 20K. Magnetic field processing reduces the …
Carbohydrate Doping To Enhance Electromagnetic Properties Of Mgb2 Superconductors, Jung Ho Kim, Sihai Zhou, Md S. Hossain, Alexey V. Pan, S X. Dou
Carbohydrate Doping To Enhance Electromagnetic Properties Of Mgb2 Superconductors, Jung Ho Kim, Sihai Zhou, Md S. Hossain, Alexey V. Pan, S X. Dou
Shi Xue Dou
The effect of carbohydrate doping on lattice parameters, microstructure, Tc, Jc, Hirr, and Hc2 of MgB2 has been studied. In this work the authors used malic acid as an example of carbohydrates as an additive to MgB2. The advantages of carbohydrate doping include homogeneous mixing of precursor powders, avoidance of expansive nanoadditives, production of highly reactive C, and significant enhancement in Jc, Hirr, and Hc2 of MgB2, compared to undoped samples. The Jc for MgB2+30 wt% C4H6O5 sample was increased by a factor of 21 at 5 K and 8 T without degradation of self-field Jc.
Fluctuation Of Mean Free Path And Transition Temperature Induced Vortex Pinning In (Ba,K)Fe2as2 Superconductors, S R. Ghorbani, Xiaolin Wang, Mahboobeh Shahbazi, S. X. Dou, C T. Lin
Fluctuation Of Mean Free Path And Transition Temperature Induced Vortex Pinning In (Ba,K)Fe2as2 Superconductors, S R. Ghorbani, Xiaolin Wang, Mahboobeh Shahbazi, S. X. Dou, C T. Lin
Shi Xue Dou
The vortex pinning mechanisms of Ba0.72K0.28Fe2As2 single crystal have been studied systematically as a function of temperature and magnetic field. The temperature dependence of the critical current density, Jc(T), was analysed within the collective pinning model at different magnetic fields. It was found that both the dl pinning mechanism, i.e., pinning associated with charge-carrier mean free path fluctuation, and the dTc pinning mechanism, which is associated with spatial fluctuations of the transition temperature, coexist in the Ba0.72K0.28Fe2As2 single crystal in fields smaller than 4 T. Their contributions are strongly temperature and magnetic field dependent. At lower temperature and B