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Articles 1 - 30 of 47
Full-Text Articles in Engineering
Drastic Improvement Of Surface Structure And Current-Carrying Ability In Yba2cu3o7 Films By Introducing Multilayered Structure, Alexey Pan, Serhiy V. Pysarenko, S X. Dou
Drastic Improvement Of Surface Structure And Current-Carrying Ability In Yba2cu3o7 Films By Introducing Multilayered Structure, Alexey Pan, Serhiy V. Pysarenko, S X. Dou
Shi Xue Dou
Much smoother surfaces and significantly improved superconducting properties of relatively thick YBa2Cu3O7 (YBCO) films have been achieved by introducing a multilayered structure with alternating main YBCO and additional NdBCO layers. The surface of thick (1 µm) multilayers has almost no holes compared to YBCO films. Critical current density (Jc) has been drastically increased up to a factor >3 in 1 µm multilayered structures compared to YBCO films over entire temperature and applied magnetic field range. Moreover, Jc values measured in thick multilayers are even larger than in much thinner YBCO films. The Jc and surface improvement have been analyzed and …
Effect Of Carbon Nanotube Doping On Critical Current Density Of Mgb2 Superconductor, S X. Dou, W. K. Yeoh, J. Horvat, M. Ionescu
Effect Of Carbon Nanotube Doping On Critical Current Density Of Mgb2 Superconductor, S X. Dou, W. K. Yeoh, J. Horvat, M. Ionescu
Shi Xue Dou
The effect of doping MgB2 with carbon nanotubes on transition temperature, lattice parameters, critical current density and flux pinning was studied for MgB2–xCx with x = 0, 0.05, 0.1, 0.2, and 0.3. The carbon substitution for B was found to enhance Jc in magnetic fields but depress Tc. The depression of Tc, which is caused by the carbon substitution for B, increases with an increasing doping level, sintering temperature, and duration. By controlling the extent of the substitution and addition of carbon nanotubes we can achieve the optimal improvement on critical current density and flux pinning in magnetic fields while …
Study Of Oxygen Incorporation In Pld Mgb2 Films By Rutherford Backscattering Spectroscopy, Y. Zhao, M. Ionescu, S X. Dou, Hua-Kun Liu
Study Of Oxygen Incorporation In Pld Mgb2 Films By Rutherford Backscattering Spectroscopy, Y. Zhao, M. Ionescu, S X. Dou, Hua-Kun Liu
Shi Xue Dou
The Rutherford backscattering (RBS) method has been employed to study the incorporation of oxygen into MgB2 films during their fabrication by pulsed-laser deposition (PLD). A series of MgB2 thin film samples were analyzed, including two films produced in situ on Al2O3-c substrates (with higher Tc and lower Tc) with an on-axis geometry, one film produced in situ with an off-axis geometry, and one film produced ex situ, with a bulk-like Tc. The amount of oxygen detected by RBS, which is stable in the form of MgO, appears to be correlated with the Tc of the films, the higher the Tc …
Effects Of Nanosized Adsorbing Material On Electrochemical Properties Of Sulfur Cathodes For Li/S Secondary Batteries, M. S. Song, S. C. Han, H. S. Kim, J. H. Kim, K. T. Kim, Y. M. Kang, H. J. Ahn, S. X. Dou, J. Y. Lee
Effects Of Nanosized Adsorbing Material On Electrochemical Properties Of Sulfur Cathodes For Li/S Secondary Batteries, M. S. Song, S. C. Han, H. S. Kim, J. H. Kim, K. T. Kim, Y. M. Kang, H. J. Ahn, S. X. Dou, J. Y. Lee
Shi Xue Dou
In order to prevent polysulfide dissolution into liquid electrolytes and to promote the Li/S redox reaction (16Li 1 S8 $ Li2Sn $ Li2S), nanosized Mg0.6Ni0.4O, which has the catalytic effect of chemical bond dissociating and is expected to have an adsorbing effect due to the effect of retaining liquid electrolyte of MgO in a Li/iron sulfide secondary battery,16 was prepared by the sol-gel method as an electrochemically inactive additive for an elemental sulfur cathode for Li/S rechargeable batteries. The Li/S battery using an elemental sulfur cathode with a nanosized Mg0.6Ni0.4O added showed the improvement of not only the discharge capacity …
Effect Of Carbon Nanotube Size On Superconductivity Properties Of Mgb/Sub 2/, W. K. Yeoh, J. Horvat, S X. Dou, P. Munroe
Effect Of Carbon Nanotube Size On Superconductivity Properties Of Mgb/Sub 2/, W. K. Yeoh, J. Horvat, S X. Dou, P. Munroe
Shi Xue Dou
Experimental results are presented for the incorporation of carbon nanotube in polycrystalline MgB/sub 2/ superconductor based on X-ray diffraction and transmission electron microscopy measurements. Electron microscopy studies show that nanotubes are embedded into the MgB/sub 2/ matrix with a fraction of nanotubes found to be unreacted and entangled. In contrast, magnetization measurements indicate a change in the critical current density with the length of nanotubes and not with their outside diameter. This implies that longer nanotubes tend to entangle, preventing their homogenous mixing with MgB/sub 2/ and dispersion. Overall, carbon nanotube doping of MgB/sub 2/ enhanced the critical density and …
Large Upper Critical Field And Irreversibility Field In Mgb2 Wires With Sic Additions, M. D. Sumption, M. Bhatia, M. Rindfleisch, M. Tomsic, Saeid Soltanian, S. X. Dou, E. W. Collings
Large Upper Critical Field And Irreversibility Field In Mgb2 Wires With Sic Additions, M. D. Sumption, M. Bhatia, M. Rindfleisch, M. Tomsic, Saeid Soltanian, S. X. Dou, E. W. Collings
Shi Xue Dou
Resistive transition measurements are reported for MgB2 strands with SiC dopants. The starting Mg powders were 325 mesh 99.9% pure, and the B powders were amorphous, 99.9% pure, and at a typical size of 1–2 µm. The SiC was added as 10 mol % of SiC to 90 mol % of binary MgB2 fsMgB2d0.9sSiCd0.1g. Three different SiC powders were used; the average particle sizes were 200 nm, 30 nm, and 15 nm. The strands were heat treated for times ranging from 5 to 30 min at temperatures from 675 °C to 900 °C. Strands with 200 nm size SiC additions …
Effect Of Heating Rates On Superconducting Properties Of Pure Mgb2, Carbon Nanotube- And Nano-Sic-Doped In Situ Mgb2/Fe Wires, S. K. Chen, K. S. Tan, B. A. Glowacki, W. K. Yeoh, Saeid Soltanian, J. Horvat, S. X. Dou
Effect Of Heating Rates On Superconducting Properties Of Pure Mgb2, Carbon Nanotube- And Nano-Sic-Doped In Situ Mgb2/Fe Wires, S. K. Chen, K. S. Tan, B. A. Glowacki, W. K. Yeoh, Saeid Soltanian, J. Horvat, S. X. Dou
Shi Xue Dou
The influence of heating rates and annealing temperatures on the transition temperatures (Tc) and critical current densities (Jc) of pure MgB2, carbon nanotube- and nano-SiC-doped in situ monofilamentary MgB2/Fe wires was investigated. It was found that higher Jc was obtained for pure MgB2 samples when heat treated with slower heating rates. SiC-doped samples also have higher Jc with slower heating rates, but the Jc is less sensitive to annealing temperatures. However, the Jc of the carbon nanotube-doped wire was found to be insensitive to heating rates. The variation in Tc and Jc with heating rate, and the different behaviors of …
Anomalous Magnetization Peak Effect In Spiral-Grown Bi2sr2cacu2oy Crystals, Xiaolin Wang, J. Horvat, Hua-Kun Liu, J. N. Li, S. X. Dou
Anomalous Magnetization Peak Effect In Spiral-Grown Bi2sr2cacu2oy Crystals, Xiaolin Wang, J. Horvat, Hua-Kun Liu, J. N. Li, S. X. Dou
Shi Xue Dou
Magnetic hysteresis loops were measured on spiral-grown Bi2Sr2CaCu2Oy (Bi-2212) crystals. An anomalous peak effect at a magnetic field of 1000–2000 Oe was observed both in high-Tc (86 K) and oxygen underdoped (Tc=76 K) spiral-grown crystals between 20 and 40 K. The peak effect was observed to be stronger than that induced by oxygen vacancies, defect dislocation networks reported in Bi-2212 crystals. Further, the anomalous peak almost completely disappeared after removing growth spiral patterns from the crystal surface. Edge barriers associated with the growth spirals are suggested to be responsible for the strong peak effect for the spiral-grown Bi-2212 crystals and …
Observation Of Vortex Distribution In Samples Of Bi-2223 Ag-Sheathed Tapes With And Without Uranium Doping By Means Of The High-Resolution Bitter Method, S. Ohshima, K. Ujiie, T. Kawai, K. Moriai, H. Yamada, D. G. Marinaro, S. X. Dou
Observation Of Vortex Distribution In Samples Of Bi-2223 Ag-Sheathed Tapes With And Without Uranium Doping By Means Of The High-Resolution Bitter Method, S. Ohshima, K. Ujiie, T. Kawai, K. Moriai, H. Yamada, D. G. Marinaro, S. X. Dou
Shi Xue Dou
We examined the distribution of vortices in both Bi-2223 Ag-sheathed tape and U-doped Bi-2223 Ag-sheathed tape applying the high-resolution Bitter method. In the low temperature region (T/spl Lt/T/sub c/), we found that the vortices in the undoped Bi-2223 Ag-sheathed tape developed into either a triangular arrangement or a heterogeneous arrangement along the grain boundaries of the Ag sheath, which form weak pinning centers. The vortex distribution for U-doped Bi-2223 samples was slightly different from the distribution for the undoped material. We observed some movement of the vortices in both the U-doped and the undoped Bi-2223 Ag-sheathed tapes at 50 K. …
Effect Of Sample Size On The Magnetic Critical Current Density In Nano-Sic Doped Mgb2 Superconductors, Saeid Soltanian, M. J. Qin, S. Keshavarzi, Xiaolin Wang, S. X. Dou
Effect Of Sample Size On The Magnetic Critical Current Density In Nano-Sic Doped Mgb2 Superconductors, Saeid Soltanian, M. J. Qin, S. Keshavarzi, Xiaolin Wang, S. X. Dou
Shi Xue Dou
The effect of sample size on the critical current density and the flux pinning of pure and SiC doped MgB2 bulk samples has been investigated. At high fields a systematic degradation of magnetic Jc and Hirr was observed as the sample size decreased. However, Jc remarkably increased on decreasing the sample volume at low magnetic fields below 1 T. The SiC doped samples show less sample size effect than the pure samples, indicating a larger n factor and therefore a stronger pinning effect due to SiC doping. Hirr was observed to decrease as a logarithmic function of the sample volume, …
Thermally Assisted Flux Flow And Individual Vortex Pinning In Bi2sr2ca2cu3o10 Single Crystals Grown By The Traveling Solvent Floating Zone Technique, Xiaolin Wang, Aihua Li, S. Yu, S. Ooi, K. Hirata, C. T. Lin, E. W. Collings, M. D. Sumption, M. Bhatia, Shichao Ding, S. X. Dou
Thermally Assisted Flux Flow And Individual Vortex Pinning In Bi2sr2ca2cu3o10 Single Crystals Grown By The Traveling Solvent Floating Zone Technique, Xiaolin Wang, Aihua Li, S. Yu, S. Ooi, K. Hirata, C. T. Lin, E. W. Collings, M. D. Sumption, M. Bhatia, Shichao Ding, S. X. Dou
Shi Xue Dou
Magnetoresisitivity and critical current density Jc as a function of temperature and field are studied for Bi2Sr2Ca2Cu3O10 single crystals grown using the traveling solvent floating zone technique. Below a characteristic field B*, Jc as a function of field exhibits a field-independent plateau associated with thermally activated pinning of individual vortices. Analysis of resistive transition broadening revealed that thermally activated flux flow is found to be responsible for the resistivity contribution in the vicinity of Tc. The activation energy U0 is 800 K in low field, scales as B–1/6 for BB–1/2 for B>2 T.
Enhancement Of The Critical Current Density And Flux Pinning Of Mgb2 Superconductor By Nanoparticle Sic Doping, S X. Dou, Saeid Soltanian, J. Horvat, Xiaolin Wang, S. H. Zhou, M. Ionescu, Hua-Kun Liu, P. Munroe, M. Tomsic
Enhancement Of The Critical Current Density And Flux Pinning Of Mgb2 Superconductor By Nanoparticle Sic Doping, S X. Dou, Saeid Soltanian, J. Horvat, Xiaolin Wang, S. H. Zhou, M. Ionescu, Hua-Kun Liu, P. Munroe, M. Tomsic
Shi Xue Dou
Doping of MgB2 by nano-SiC and its potential for the improvement of flux pinning were studied for MgB2–x(SiC)x/2 with x = 0, 0.2, and 0.3 and for 10 wt % nano-SiC-doped MgB2 samples. Cosubstitution of B by Si and C counterbalanced the effects of single-element doping, decreasing Tc by only 1.5 K, introducing intragrain pinning centers effective at high fields and temperatures, and significantly enhancing Jc and Hirr. Compared to the undoped sample, Jc for the 10 wt % doped sample increased by a factor of 32 at 5 K and 8 T, 42 at 20 K and 5 T, …
The Electrode Properties Of Mg1.9al0.1ni0.8co0.1mn0.1 Alloy By Mechanical Grinding With Ni Powders, L. Sun, Hua-Kun Liu, D. H. Bradhurst, S. X. Dou
The Electrode Properties Of Mg1.9al0.1ni0.8co0.1mn0.1 Alloy By Mechanical Grinding With Ni Powders, L. Sun, Hua-Kun Liu, D. H. Bradhurst, S. X. Dou
Shi Xue Dou
A modified magnesium alloy of composition Mg1.9Al0.1Ni0.8Co0.1Mn0.1 was prepared by mechanical grinding with Ni powder for periods up to 120 h. The resulting structures of the Mg1.9Al0.1Ni0.8Co0.1Mn0.1 alloys were found to be amorphous. The electrodes of the modified Mg1.9Al0.1Ni0.8Co0.1Mn0.1 alloys had large discharge capacities. At a discharge current rate of 50 mA/g, the capacity was 630 mAh/g after 50 h of mechanical grinding and 510 mAh/g after 120 h of mechanical grinding.
Uranium Doping And Thermal Neutron Irradiation Flux Pinning Effects In Mgb2, Tania M. Silver, J. Horvat, M. Reinhard, P. Yao, S. Keshavarzi, P. Munroe, S. X. Dou
Uranium Doping And Thermal Neutron Irradiation Flux Pinning Effects In Mgb2, Tania M. Silver, J. Horvat, M. Reinhard, P. Yao, S. Keshavarzi, P. Munroe, S. X. Dou
Shi Xue Dou
The U/n method is a well-established means of improving flux pinning and critical current performance in cuprate superconductors. The method involves the doping of the superconductor with 235U followed by irradiation with thermal neutrons to promote fission. The resultant columnar damage tracks produced by the energetic fission products pin flux vortices and improve critical current performance in magnetic fields. No such improvement could be observed when the U/n method was applied to the MgB2 superconductor. No fission tracks could be observed in TEM, even for samples that were irradiated at the highest fluence. Gamma-ray spectroscopy indicated that fission had occurred …
Overcritical State In Superconducting Round Wires Sheathed By Iron, Alexey Pan, S X. Dou
Overcritical State In Superconducting Round Wires Sheathed By Iron, Alexey Pan, S X. Dou
Shi Xue Dou
Magnetic measurements carried out on MgB2 superconducting round wires have shown that the critical current density Jc(Ba) in wires sheathed by iron can be significantly higher than that in the same bare (unsheathed) wires over a wide applied magnetic field Ba range. The magnetic behavior is, however, strongly dependent on the magnetic history of the sheathed wires, as well as on the wire orientation with respect to the direction of the applied field. The behavior observed can be explained by magnetic interaction between the soft magnetic sheath and superconducting core, which can result in a redistribution of supercurrents in the …
Improved In-Field Behaviour Of Uranium Doped Biscco Tapes By Enhanced Flux Pinning, S. Tonies, H. W. Weber, Y. C. Guo, S. X. Dou, R. Sawh, R. Weinstein
Improved In-Field Behaviour Of Uranium Doped Biscco Tapes By Enhanced Flux Pinning, S. Tonies, H. W. Weber, Y. C. Guo, S. X. Dou, R. Sawh, R. Weinstein
Shi Xue Dou
Uranium doped BiSCCO 2223 tapes were irradiated by thermal neutrons. The resulting fission-induced defects improve flux pinning and shift the irreversibility line to higher fields. Significant enhancements of the transport critical current density as well as a reduction of the Jc-anisotropy are found for the irradiated samples. Furthermore, inter- and intragranular critical current densities were determined from the remanent magnetic moments by SQUID magnetometry.
Comparison Of Small-Field Behavior In Mgb2, Low- And High-Temperature Superconductors, Alexey Pan, S X. Dou
Comparison Of Small-Field Behavior In Mgb2, Low- And High-Temperature Superconductors, Alexey 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 MgB2 bulk superconductors, or to thermally activated processes for Bi-based superconductors and YBa2Cu3O7−8 superconducting films. In both cases the vortex pinning influence appears to have a secondary role, affecting the effective …
High Temperature Ferromagnetism In Ni-Doped In2o3 And Indium-Tin Oxide, Germanas Peleckis, Xiaolin Wang, S X. Dou
High Temperature Ferromagnetism In Ni-Doped In2o3 And Indium-Tin Oxide, Germanas Peleckis, Xiaolin Wang, S X. Dou
Shi Xue Dou
Observation of high temperature ferromagnetism in Ni-doped In2O3 and indium-tin-oxide (ITO) samples prepared by a solid state synthesis route is reported. Both Ni-doped compounds showed a clear ferromagnetism above 300 K with the magnetic moments of 0.03–0.06µB/Ni and 0.1µB/Ni at 300 and 10 K, respectively. Ni-doped In2O3 samples showed a typical semiconducting behavior with a room temperature resistivity of ρ ~ 2 Ω cm, while Ni-doped ITO samples were metallic with ρ ~2×10–2 Ω cm. Analysis of different conduction mechanisms suggested that variable range hopping model explains our ρ -T data for the Ni-doped In2O3 sample the best.
Evidence For Vortex Pinning Induced By Fluctuations In The Transition Temperature Of Mgb2 Superconductors, M. J. Qin, Xiaolin Wang, Hua-Kun Liu, S. X. Dou
Evidence For Vortex Pinning Induced By Fluctuations In The Transition Temperature Of Mgb2 Superconductors, M. J. Qin, Xiaolin Wang, Hua-Kun Liu, S. X. Dou
Shi Xue Dou
The field-dependent critical current density jc(B) of a MgB2 bulk sample has been obtained using magnetic measurements. The jc(B) curves at different temperatures demonstrate a crossover from single vortex pinning to small-bundle vortex pinning, when the field is larger than the crossover field Bsb. The temperature dependence of Bsb(T) is in agreement with a model of randomly distributed weak pinning centers via the spatial fluctuations of the transition temperature (δTc pinning), while pinning due to the mean-free-path fluctuations (δl pinning) is not observed.
Nanoscale-Sic Doping For Enhancing Jc And Hc2 In Superconducting Mgb2, S X. Dou, V. Braccini, Saeid Soltanian, R. Klie, Y. Zhu, S. Li, Xiaolin Wang, D. Larbalestier
Nanoscale-Sic Doping For Enhancing Jc And Hc2 In Superconducting Mgb2, S X. Dou, V. Braccini, Saeid Soltanian, R. Klie, Y. Zhu, S. Li, Xiaolin Wang, D. Larbalestier
Shi Xue Dou
The effect of nanoscale-SiC doping of MgB2 was investigated in comparison with undoped, clean-limit, and Mg-vapor-exposed samples using transport and magnetic measurements. It was found that there are two distinguishable but related mechanisms that control the critical current-density-field JcsHd behavior: increase of upper critical field Hc2 and improvement of flux pinning. There is a clear correlation between the critical temperature Tc, the resistivity r, the residual resistivity ratio RRR=Rs300 Kd /Rs40 Kd, the irreversibility field H*, and the alloying state in the samples. The Hc2 is about the same within the measured field range for both the Mg-vapor-treated and the …
Intrinsic Nanostructural Domains: Possible Origin Of Weaklinkless Superconductivity In The Quenched Reaction Product Of Mg And Amorphous B, S. Li, O. Prabhakar, T. T. Tan, C. Q. Sun, Xiaolin Wang, Saeid Soltanian, J. Horvat, S. X. Dou
Intrinsic Nanostructural Domains: Possible Origin Of Weaklinkless Superconductivity In The Quenched Reaction Product Of Mg And Amorphous B, S. Li, O. Prabhakar, T. T. Tan, C. Q. Sun, Xiaolin Wang, Saeid Soltanian, J. Horvat, S. X. Dou
Shi Xue Dou
Smooth modulation structure of Mg–B alloy in the quenched reaction product of Mg and amorphous B was studied. It indicates that the MgB2 formed possibly in spinodal decomposition, thus resulting in MgB2 nanodomains. It was found that the nanodomains with small angle boundaries of atomic-scale width were distributed within the subgrains that constitute the clusters in MgB2 grains. This nanostructural characteristic may be intrinsic in the quenched reaction product of Mg and amorphous B. It makes the nanodomain boundaries not act as barriers to the current percolation path, thus exhibiting no weak-link problem in the MgB2.
Order-Disorder Transition In Bi2.1sr1.9cacu2o8 + Delta Single Crystals Doped With Fe And Pb, K. K. Uprety, J. Horvat, Xiaolin Wang, M. Ionescu, Hua-Kun Liu, S. X. Dou, E. H. Brandt
Order-Disorder Transition In Bi2.1sr1.9cacu2o8 + Delta Single Crystals Doped With Fe And Pb, K. K. Uprety, J. Horvat, Xiaolin Wang, M. Ionescu, Hua-Kun Liu, S. X. Dou, E. H. Brandt
Shi Xue Dou
The magnetic field Hdis(T) where an order-disorder transition of the vortex lattice in high-Tc superconductors occurs, is investigated by measurements of the magnetization M(H) in Bi2.1Sr1.9CaCu2O8 + delta (Bi2212) single crystals doped with iron and lead. Comparative studies are made of the temperature dependences of the field Hpeak(T), where the second peak occurs in |M(H)|, and the fields Hmin(T), and Hinfl(T) where a minimum and an inflection point occur at the low-field side of this peak. It is proposed that Hdis(T) lies close to Hinfl. In Bi2.1Sr1.9Ca1.0(Cu1–yFey)2O8 + delta single crystals with Fe concentration y = 0, 0.005, 0.016, and …
Origin Of Paramagnetic Magnetization In Field-Cooled Yba2cu3o7–Delta Films, D. A. Luzhbin, A. V. Pan, V. A. Komashko, V. S. Flis, V. M. Pan, S. X. Dou, P. Esquinazi
Origin Of Paramagnetic Magnetization In Field-Cooled Yba2cu3o7–Delta Films, D. A. Luzhbin, A. V. Pan, V. A. Komashko, V. S. Flis, V. M. Pan, S. X. Dou, P. Esquinazi
Shi Xue Dou
Temperature dependences of the magnetic moment have been measured in YBa2Cu3O72d thin films over a wide magnetic-field range (5
Synthesis Of Nonstoichiometric Amorphous Mg-Based Alloy Electrodes By Mechanical Milling, L. Sun, Hua-Kun Liu, D. H. Bradhurst, S. X. Dou
Synthesis Of Nonstoichiometric Amorphous Mg-Based Alloy Electrodes By Mechanical Milling, L. Sun, Hua-Kun Liu, D. H. Bradhurst, S. X. Dou
Shi Xue Dou
Nonstoichiometric amorphous Mg-Ni and Mg-Ni-V alloys were synthesized by mechanical milling the crystalline Mg2Ni alloy with Ni and/or V powders. All the nonstoichiometric amorphous Mg-based alloys result in Mg-based alloy electrodes with very high discharge capacities by comparison with crystalline Mg2Ni alloys. The results indicate that nonstoichiometric amorphous Mg-based alloys can be obtained either by increasing the Ni content, adding a range of other elements, or both, using a mechanical milling method. The nonstoichiometric Mg-based alloy electrodes studied have shown improved initial discharge capacities compared with the stoichiometric amorphous MgNi alloy. These results describe a method of achieving better Mg-based …
Microstructures And Enhancement Of Critical Current Density In Yba/Sub 2/Cu/Sub 3/O/Sub 7/ Thin Films Grown By Pulsed Laser Deposition On Various Single Crystal Substrates Modified By Ag Nano-Dots, Aihua Li, M. Ionescu, Hua-Kun Liu, Tania M. Silver, Xiaolin Wang, S. X. Dou
Microstructures And Enhancement Of Critical Current Density In Yba/Sub 2/Cu/Sub 3/O/Sub 7/ Thin Films Grown By Pulsed Laser Deposition On Various Single Crystal Substrates Modified By Ag Nano-Dots, Aihua Li, M. Ionescu, Hua-Kun Liu, Tania M. Silver, Xiaolin Wang, S. X. Dou
Shi Xue Dou
YBa2Cu3O7 (Y123) thin films were grown by pulsed laser deposition (PLD) on YSZ (100), SrTiO3 (100), and LaAlO3 (100) single crystal substrates. Prior to the film deposition, a discontinuous layer of Ag nano-dots was deposited on the substrates. The Y123 films grown on such surfaces modified with Ag nano-dots were characterized by Atomic Force Microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM), AC susceptibility and DC magnetization. The effects of the density of Ag nano-dots, which was controlled by the numbers of PLD shots, on the microstructures and resultant critical current density Jc have been studied systematically. Results showed …
New Method For The Fabrication Of Al-Stabilized Fe/Mgb2 Wires, A. Shcherbakov, A. V. Pan, S X. Dou, E. W. Collings
New Method For The Fabrication Of Al-Stabilized Fe/Mgb2 Wires, A. Shcherbakov, A. V. Pan, S X. Dou, E. W. Collings
Shi Xue Dou
To employ Al stabilizer on Fe sheathed MgB2 wire the hot aluminizing technique was used. The present technique allows us to form MgB2 superconductor by an in-situ reaction technique and apply Al stabilizer simultaneously, because the processing temperature of MgB2 is similar to the melting temperature of Al. Two types of Fe sheathed MgB2 wires—“reacted” and “green” (unreacted)— were immersed in an Al bath to produce a layer of Al stabilizer on the surface of the superconductor. The magnetic and transport ( ) curves for both “reacted” and “green” Al/Fesheathed wires have been measured at 10 and 20 K and …
Thermal Activation And Ac-Field-Induced Discontinuous Domain Jumps In Perovskite La0.7ca0.3mno3, Xiaolin Wang, J. Horvat, Hua-Kun Liu, S. X. Dou
Thermal Activation And Ac-Field-Induced Discontinuous Domain Jumps In Perovskite La0.7ca0.3mno3, Xiaolin Wang, J. Horvat, Hua-Kun Liu, S. X. Dou
Shi Xue Dou
Low-field ac susceptibility was measured on bulk La0.7Ca0.3MnO3 prepared by a partial melting technique. Discontinuous jumps with heights of (1 - 2)105 emu at temperature intervals of 3-5 K were observed in the ac susceptibility. 28 jumps were observed in the temperature range between 4.2 K and the Curie temperature of 250 K, with an ac field amplitude of 1 Oe, a frequency of 117 Hz, and a dc bias field of 5 and 20 Oe. Upon increasing the frequency up to 5000 Hz, the jumps shifted to lower temperature. For a dc bias field of 50 Oe and an …
Growth, Microstructures, And Superconductivity Of Bi2–Xpbxsr2ca1–Ygdycu2o8 + Z Single Crystals, Xiaolin Wang, E. Takayama-Muromachi, Aihua Li, Z. Cheng, S. Keshavarzi, M. J. Qin, S. X. Dou
Growth, Microstructures, And Superconductivity Of Bi2–Xpbxsr2ca1–Ygdycu2o8 + Z Single Crystals, Xiaolin Wang, E. Takayama-Muromachi, Aihua Li, Z. Cheng, S. Keshavarzi, M. J. Qin, S. X. Dou
Shi Xue Dou
Bi2–xPbxSr2Ca1–yGdyCu2O8 + delta (x = 0.34 and y = 0.18, 0.34) crystals were grown by the self-flux method. The crystals have a cleavage thickness of only half unit cell up to two unit cells with Tc only dropping 20 K as y is increased from 0.18 to 0.34 for as-grown crystals. However, Tc increased to almost the same value of about 80 K after annealing in air regardless of the Gd doping levels. The co-doping produced enhanced flux pinning compared to the sole Gd doping. A secondary peak effect presented in crystals with x = 0.34 and y = 0.34 …
Observation Of Heat Flow At Transition Temperature In La1–Xcaxmno3 + Delta Oxides, Y. B. Zhang, S. Li, C. Q. Sun, W. Gao, S. X. Dou, P. Hing
Observation Of Heat Flow At Transition Temperature In La1–Xcaxmno3 + Delta Oxides, Y. B. Zhang, S. Li, C. Q. Sun, W. Gao, S. X. Dou, P. Hing
Shi Xue Dou
Heat-flow changes of La1–xCaxMnO3 + delta (x=0.25, 0.33, and 0.375) magnetoresistive oxides at their Curie temperatures have been detected using differential scanning calorimetry in the temperature range from 173 to 293 K. However, the transition does not occur in the samples of x=0.125 and 0.5. It was found that the heat flow reflected the transition behavior and the enthalpy change of the transition decreased as the transition temperature increased. These results indicate that the La1–xCaxMnO3 + delta oxides (x=0.25, 0.33, and 0.375) undergo an endothermic phase transition from a low-temperature ferromagnetic metal to a high-temperature paramagnetic insulator. It is assumed …
Nickel Hydroxide As An Active Material For The Positive Electrode In Rechargeable Alkaline Batteries, J Chen, D. H. Bradhurst, S X. Dou, Hua-Kun Liu
Nickel Hydroxide As An Active Material For The Positive Electrode In Rechargeable Alkaline Batteries, J Chen, D. H. Bradhurst, S X. Dou, Hua-Kun Liu
Shi Xue Dou
Spherical nickel hydroxide powders coprecipitated with the additives Ca(OH)2, Co(OH)2, and Zn(OH)2 were prepared through a spraying technique. These powders, which have a higher tapping density and a much smaller pore volume and crystalline size than conventional powders, were used as the active materials of nickel hydroxide electrodes. The effects of the Ca(OH)2, Co(OH)2, and Zn(OH)2 additions on electrode properties such as charge-discharge, reversibility of the electrode reaction, and cycle life, were studied. The relationship between the electrode swelling and the formation of g-NiOOH was also investigated. The results show that nickel hydroxide powders having a smaller crystallite size show …