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Articles 1 - 30 of 35
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Collective Librations Of Water Molecules In The Crystal Lattice Of Rubidium Bromide: Experiment And Simulation, L M. Lepodise, J Horvat, Roger A. Lewis
Collective Librations Of Water Molecules In The Crystal Lattice Of Rubidium Bromide: Experiment And Simulation, L M. Lepodise, J Horvat, Roger A. Lewis
Josip Horvat
Terahertz spectroscopy of RbBr reveals four prominent absorption lines at room temperature and a further 15 lines at 10 K. Via density-functional-theory (DFT) numerical modelling using the PBE0 hybrid GGA functional, all the absorptions are identified as correlated librations of water molecules in the RbBr lattice. Each libration mode is a combination of rocking, wagging and twisting motions of the water molecules. The number of libration lines and numerical modelling show that the C2v symmetry of water in RbBr is broken. Our modelling shows that the distribution of libration amplitudes and phases for different water molecules in the RbBr unit …
Enhancing Superconducting Properties Of Mgb2 Pellets By Addition Of Amorphous Magnetic Ni-Co-B Nanoparticles, Mislav Mustapic, Josip Horvat, Md Shahriar Hossain, Zeljko Skoko, S X. Dou
Enhancing Superconducting Properties Of Mgb2 Pellets By Addition Of Amorphous Magnetic Ni-Co-B Nanoparticles, Mislav Mustapic, Josip Horvat, Md Shahriar Hossain, Zeljko Skoko, S X. Dou
Josip Horvat
Amorphous magnetic Ni-Co-B nanoparticles with an average size of 5 nm were added to precursor powders of MgB2 superconductor. The preparation procedure for MgB2 pellets was optimized for obtaining the best critical current density (Jc) at elevated magnetic fields. Addition of Ni-Co-B decreases the Jc for heat treatment of precursor powders at 650 ° C. Heat treatments at 770 ° C and higher improve Jc at 20 and 5 K. This improvement occurs at both temperatures through the increase of the effective connectivity between MgB2 crystals. Vortex pinning was enhanced at 5 K, but not at 20 K. Ni-Co-B nanoparticles …
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
Josip Horvat
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 …
Hydrothermal Synthesis And Optical, Magnetic And Supercapacitance Properties Of Nanoporous Cobalt Oxide Nanorodes, Guoxiu Wang, Xiaoping Shen, Josip Horvat, Bei Wang, Hao Liu, David Wexler, Jane Yao
Hydrothermal Synthesis And Optical, Magnetic And Supercapacitance Properties Of Nanoporous Cobalt Oxide Nanorodes, Guoxiu Wang, Xiaoping Shen, Josip Horvat, Bei Wang, Hao Liu, David Wexler, Jane Yao
Josip Horvat
Nanoporous cobalt oxide nanorods were synthesized by a hydrothermal method. Transmission electron microscopy analysis showed that the individual Co3O4 nanorods have a nanoporous structure, consisting of the textured aggregations of nanocrystals. Optical properties of Co3O4 nanorods were characterized by Raman and UV−vis spectroscopy. Magnetic property measurement shows that Co3O4 nanorods have a low Néel transition temperature of 35 K. We observed quite significant exchange bias for nanoporous Co3O4 nanorods, indicating the existence of magnetic coupling between the nanocrystals in Co3O4 nanorods. When applied as electrode materials in supercapacitors, Co3O4 demonstrated a high capacitance of 280 F/g.
Improvement Of Jc And Hc2 In Mgb2 Superconductor With Citric Acid Addition, Rong Zeng, Lin Lu, Jianli Wang, Wenxian Li, Dongqi Shi, Josip Horvat, S. X. Dou
Improvement Of Jc And Hc2 In Mgb2 Superconductor With Citric Acid Addition, Rong Zeng, Lin Lu, Jianli Wang, Wenxian Li, Dongqi Shi, Josip Horvat, S. X. Dou
Josip Horvat
This paper reports on the fabrication and characterization of citric acid (CA)-C6H8O7 added MgB2 superconductor. The relationships between microstructures, critical current density (Jc), critical temperature (Tc), upper critical field (Hc2), irreversibility field (Hirr), and normal state resistivity for 10 wt% C6H8O7 added MgB2 samples sintered at temperatures from 650C to 950C were systematically studied. A reduction in Tc and in lattice parameter a due to the C substitution and possible oxygen (O) effects occurs wtih C6H8O7 addition. Jc, Hc2, and Hirr are significantly enhanced, however, with the addition of C6H8O7. All the samples exhibit Jc above 104 A/cm2 at 5 …
Stress/Strain Induced Flux Pinning In Highly Dense Mgb2 Bulks, Rong Zeng, S X. Dou, Lin Lu, Wenxian Li, Chung-Kiak Poh, Jung Ho Kim, Josip Horvat, Dongqi Shi, Jianli Wang, Paul G. Munroe, X. F. Wang, Rongkun Zheng, S. P. Ringer, M Rindfleisch, Mike Tomsic
Stress/Strain Induced Flux Pinning In Highly Dense Mgb2 Bulks, Rong Zeng, S X. Dou, Lin Lu, Wenxian Li, Chung-Kiak Poh, Jung Ho Kim, Josip Horvat, Dongqi Shi, Jianli Wang, Paul G. Munroe, X. F. Wang, Rongkun Zheng, S. P. Ringer, M Rindfleisch, Mike Tomsic
Josip Horvat
We have systematically studied the flux pinning behavior of MgB2 bulks synthesized by direct diffusion of Mg into pressed pellets of high purity crystalline B powder, with and without mixing with C and SiC nanoparticles, at a reaction temperature of 850degC for 10 hrs. All of the samples showed very high purity and high density, but their microstructure and flux pinning behavior showed significant differences. It was found that the pure MgB2 agrees with the deltaTc pinning model, nano-C doped MgB2 agrees with the deltal pinning model, while the SiC+MgB2 composite agrees with the deltaepsiv pinning model (stress/strain field pinning), …
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
Josip Horvat
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 …
Complementary Techniques For Probing Terahertz Magnetic Excitations In Cu3bi(Seo3)2o2cl, K H. Miller, E Constable, H Berger, D B. Tanner, J Horvat, R A. Lewis
Complementary Techniques For Probing Terahertz Magnetic Excitations In Cu3bi(Seo3)2o2cl, K H. Miller, E Constable, H Berger, D B. Tanner, J Horvat, R A. Lewis
Josip Horvat
A low frequency magnetic excitation in Cu3Bi(SeO 3)2O2Cl has been studied through complementary spectroscopic techniques which utilised terahertz radiation from a synchrotron, a mercury arc lamp, and a two-colour photomixing system. The excitation has been studied at temperatures down to 5K and in magnetic fields up to 10T. © 2012 IEEE.
Magnetic And Superconducting Properties Of Spin-Fluctuation-Limited Superconducting Nanoscale Vnx, R Zeng, J Liu, G Du, W. X. Li, J Wang, J Horvat, S X. Dou
Magnetic And Superconducting Properties Of Spin-Fluctuation-Limited Superconducting Nanoscale Vnx, R Zeng, J Liu, G Du, W. X. Li, J Wang, J Horvat, S X. Dou
Josip Horvat
"VNx nanoparticles and nanowires have been prepared by nitrifying V2O5 nanoparticles (NP) and nanowires (NW). The V2O5 NP and NW were synthesized by a facile hydrothermal method. Magnetic susceptibility (chi) and magnetization measurements showed long range superconducting ordering (LRSO) at the temperature of 5.8 K for NW, but there was no observation of LRSO (at least down to 2 K) for the NP sample, which is a much lower temperature than for the corresponding bulk, while both NP and NW showed the absence of long range magnetic ordering, at least down to 2 K. However, the chi data showed that …
Temperature Effect On Microstructure And Electromagnetic Performance Of Polycarbosilane And Sugar-Doped Mgb2 Wires, Andrey V. Shcherbakov, Josip Horvat, Olga V. Shcherbakova, Nikolina Novosel, Emil Babic, S. X. Dou
Temperature Effect On Microstructure And Electromagnetic Performance Of Polycarbosilane And Sugar-Doped Mgb2 Wires, Andrey V. Shcherbakov, Josip Horvat, Olga V. Shcherbakova, Nikolina Novosel, Emil Babic, S. X. Dou
Josip Horvat
The effect of processing temperature on structural and superconducting properties of 10 wt.% sugar- and 10 wt.% PCS-doped MgB2 wires is systematically investigated. It is demonstrated that these dopants significantly enhance the electromagnetic performance of Fe-clad MgB2 superconductor and increase its potential for practical application. The enhancement of in-field critical current density (Jc(Ba)) and upper critical field (Bc2) is due to formation of a large amount of lattice defects caused by impurities and C substitution into the MgB2 crystal lattice. High temperature sintering of sugar-doped sample results in as high Bc2 value as 37 T (at 5 K), which correlates …
Peeling Adhesive Tape Emits Electromagnetic Radiation At Terahertz Frequencies, J. Horvat, R. A. Lewis
Peeling Adhesive Tape Emits Electromagnetic Radiation At Terahertz Frequencies, J. Horvat, R. A. Lewis
Josip Horvat
An unusual concept for a simple and inexpensive terahertz source is presented: unpeeling adhesive tape. The observed spectrum of this terahertz radiation exhibits a peak at 2 THz and a broader peak at 18 THz. The radiation is not polarized. The mechanism of terahertz radiation is tribocharging of the adhesive tape and subsequent discharge, possibly bremsstrahlung with absorption or energy density focusing during the dielectric breakdown of a gas. The accompanying optical emission is also a consequence of tribocharging.
Mechanisms Of X-Ray Emission From Peeling Adhesive Tape, Evan Constable, Josip Horvat, R. A. Lewis
Mechanisms Of X-Ray Emission From Peeling Adhesive Tape, Evan Constable, Josip Horvat, R. A. Lewis
Josip Horvat
It has previously been reported that x-rays are emitted when adhesive tape is peeled in a vacuum but no account of the dependence of the x-ray emission on the pressure of the environment has been given to date. In this paper we present detailed experimental data on the number and angular distribution of x-ray photons as a function of pressure. We find that x-rays are emitted for pressures between p0 = 10−3 and p1 = 10−2 mBar, with ∼ 106 counts/(cm2 s) recorded by a 256×256 pixel2 silicon array sensor placed 35 mm from the tape. The main role of …
Detection Of Biochar Components For Soil Fertility Using Thz-Tds, E M. Pogson, J Horvat, Roger A. Lewis, S D. Joseph
Detection Of Biochar Components For Soil Fertility Using Thz-Tds, E M. Pogson, J Horvat, Roger A. Lewis, S D. Joseph
Josip Horvat
Different forms of biochar can have greatly different properties as fertilisers, yet there is no effective screening method to distinguish them. Terahertz Time Domain Spectroscopy has been used to distinguish various biochars, including Sawdust char, BMC5 with lime char and Saligna char.
Effect Of Processing Temperature On High Field Critical Current Density And Upper Critical Field Of Nanocarbon Doped Mgb2, W. K. Yeoh, J. Horvat, J. H. Kim, X. Xu, S. X. Dou
Effect Of Processing Temperature On High Field Critical Current Density And Upper Critical Field Of Nanocarbon Doped Mgb2, W. K. Yeoh, J. Horvat, J. H. Kim, X. Xu, S. X. Dou
Josip Horvat
Correlation of upper critical field (Hc2) and critical current density (Jc) with processing temperature of nano-C doped MgB2 has been studied in comparison to SiC and pure MgB2. SiC and C doped MgB2 exhibit opposite trends in the dependence of Jc and Hc2 on sintering temperature. This is explained by different reactivities of carbon available upon creation of MgB2 for the two types of doping. Nanocarbon doped MgB2 requires sintering temperatures in excess of 900 °C to obtain high boron substitution for carbon, enhancing the vortex pinning and …
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
Josip Horvat
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
Josip Horvat
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 …
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
Josip Horvat
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 …
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Josip Horvat
High-quality bulk MgB2 exhibits a structure of voids and agglomeration of crystals on different length scales. Because of this, the superconducting currents percolate between the voids in the ensuing structure. Magnetic measurements reveal that the superconducting currents circulate on at least three different length scales, of ∼1 μm, ∼10 μm, and whole of the sample (∼millimeter). Each of these screenings contributes to the measured irreversible magnetic moment (Δm). The analysis of the field dependence of Δm for samples of subsequently decreasing size showed that the critical current obtained using the simple critical state model is erroneous. This leads to the …
Effect Of Uranium Doping And Thermal Neutron Irradiation On The Flux-Pinning Of Silver-Clad Bi-Sr-Ca-Cu-O Tapes, D. Marinaro, S X. Dou, J. Horvat, J. Boldeman, R. Weinstein, R. Sawh
Effect Of Uranium Doping And Thermal Neutron Irradiation On The Flux-Pinning Of Silver-Clad Bi-Sr-Ca-Cu-O Tapes, D. Marinaro, S X. Dou, J. Horvat, J. Boldeman, R. Weinstein, R. Sawh
Josip Horvat
Ag/Bi-2223 tapes doped with small quantities of 235UO 4 powder were prepared by the powder-in-tube process and irradiated in a thermal neutron environment. Substantial improvements in critical current density (Jc)-applied field (H) performance and anisotropy have been previously reported. However, the radioactivity of the silver sheath is a limiting factor for commercial and industrial applications of this technique. Here we report the performance of the technique using various doping levels (from 0.15 to 2 percent by weight (wt.%) UO4) and thermal neutron fluences (Φn), in order to further reduce the silver radioactivity. Optimum fluence levels are identified and an optimum …
Effect Of Grain Size And Doping Level Of Sic On The Superconductivity And Critical Current Density In Mgb/Sub 2/ Superconductor, Saeid Soltanian, Xiaolin Wang, J. Horvat, M. J. Qin, Hua-Kun Liu, P. R. Munroe, S. X. Dou
Effect Of Grain Size And Doping Level Of Sic On The Superconductivity And Critical Current Density In Mgb/Sub 2/ Superconductor, Saeid Soltanian, Xiaolin Wang, J. Horvat, M. J. Qin, Hua-Kun Liu, P. R. Munroe, S. X. Dou
Josip Horvat
SiC doped MgB/sub 2/ polycrystalline samples were fabricated by in-situ reaction using different grain sizes (20 nm, 100 nm, and 37 /spl mu/m) of SiC and different doping levels (0, 8, 10, 12, 15 wt%). Phases, microstructures, superconductivity, critical current density and flux pinning have been systematically investigated using XRD, SEM, TEM, and magnetic measurements. Results show that grain sizes of the starting precursors of SiC have a strong effect on the critical current density and its field dependence. The smaller the SiC grains are, the better the J/sub c/ field performance is. Significant enhancement of J/sub c/ and the …
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
Josip Horvat
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 …
An Alternative Method For Determination Of The Lock-In Angle In Twinned Superconductors, S. Keshavarzi, J. Horvat, Alexey Pan, M. J. Qin, S. X. Dou, X. Yao, P. Munroe
An Alternative Method For Determination Of The Lock-In Angle In Twinned Superconductors, S. Keshavarzi, J. Horvat, Alexey Pan, M. J. Qin, S. X. Dou, X. Yao, P. Munroe
Josip Horvat
An alternative method for determining the lock-in angle phiL for pinning of the vortices on extended defects has been developed. This method does not require any preassumed criterion for defining phiL. Highly twinned Sm1+xBa2–xCu3O6+y single crystal was used for demonstrating the method. Appropriate scaling of the hysteresis loops measured for different angles between the field and twin planes in highly twinned SmBaCuO single crystal led to a clear discrimination between two vortex dynamics regimes. From this scaling, the lock-in angle was determined to be 6°±0.1° for the single crystal investigated. This method significantly reduces the uncertainty in determining the lock-in …
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
Josip Horvat
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 …
The Relevance Of The Self-Field For The 'Peak Effect' In The Transport Jc(H) Of Iron-Sheathed Mgb2 Wires, J. Horvat, Saeid Soltanian, W. K. Yeoh
The Relevance Of The Self-Field For The 'Peak Effect' In The Transport Jc(H) Of Iron-Sheathed Mgb2 Wires, J. Horvat, Saeid Soltanian, W. K. Yeoh
Josip Horvat
Ferromagnetic sheath around a superconducting wire results in an unusual transport Jc(H). For the field perpendicular to the current, there is a plateau in Jc(H) at high temperatures and intermediate fields. This plateau develops into a peak at lower temperatures, resembling a “peak effect”. A model based on cancellation of the self-field of the current and external field within the iron sheath was proposed for the explanation of the plateau in Jc(H). We test this model in three key experiments. Firstly, we show that the form of Jc(H) for round MgB2/Fe wires is strongly temperature dependent. This is in contradiction …
Transport Critical Current Density In Fe-Sheathed Nano-Sic Doped Mgb/Sub 2/ Wires, S X. Dou, J. Horvat, Saeid Soltanian, Xiaolin Wang, M. J. Qin, S. H. Zhou, Hua-Kun Liu, P. G. Munroe
Transport Critical Current Density In Fe-Sheathed Nano-Sic Doped Mgb/Sub 2/ Wires, S X. Dou, J. Horvat, Saeid Soltanian, Xiaolin Wang, M. J. Qin, S. H. Zhou, Hua-Kun Liu, P. G. Munroe
Josip Horvat
The nano-SiC doped MgB/sub 2//Fe wires were fabricated using a powder-in-tube method and an in-situ reaction process. The depression of T/sub c/ with increasing SiC doping level remained rather small due to the counterbalanced effect of Si and C co-doping. The high level SiC co-doping allowed creation of the intra-grain defects and nano-inclusions, which act as effective pinning centers, resulting in a substantial enhancement in the J/sub c/(H) performance. The transport J/sub c/ for all the wires is comparable to the magnetic J/sub c/ at higher fields despite the low density of the samples and percolative nature of current. The …
Superconductivity And Flux Pinning In Y And Heavily Pb Codoped Bi-2212 Single Crystals, Xiaolin Wang, Hua-Kun Liu, S X. Dou, J. Horvat, D. Millikon, G. Heine, W. Lang, H. M. Luo, Shichao Ding
Superconductivity And Flux Pinning In Y And Heavily Pb Codoped Bi-2212 Single Crystals, Xiaolin Wang, Hua-Kun Liu, S X. Dou, J. Horvat, D. Millikon, G. Heine, W. Lang, H. M. Luo, Shichao Ding
Josip Horvat
Studies of superconductivity and flux pinning were carried out on (Bi1.64Pb0.36)Sr2Ca1–xYxCu2O8 + y (x = 0, 0.05, 0.11, 0.33) single crystals grown by the self-flux method. X-ray diffraction, transport, and magnetic measurements were performed for purposes of characterization. X-ray analysis revealed that the c lattice parameter systemically decreases as the Y doping level increases. The superconducting transition temperature Tc decreases from 80 to 30 K as x increases. A strong annealing effect on Tc and superconducting volume has been observed. Resistance measurements show that x = 0.33 samples are semiconductive over a wide temperature range between 4.2 and 300 K …
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
Josip Horvat
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 …
Intense Vortex Pinning Enhanced By Semicrystalline Defect Traps In Self-Aligned Nanostructured Mgb2, S. Li, T. White, K. Laursen, T. T. Tan, C. Q. Sun, Z. L. Dong, Y. Li, S. H. Zho, J. Horvat, S. X. Dou
Intense Vortex Pinning Enhanced By Semicrystalline Defect Traps In Self-Aligned Nanostructured Mgb2, S. Li, T. White, K. Laursen, T. T. Tan, C. Q. Sun, Z. L. Dong, Y. Li, S. H. Zho, J. Horvat, S. X. Dou
Josip Horvat
In this work, we report the discovery of a vortex pinning source: semicrystalline defect wells in self-aligned nanostructured MgB2. It is demonstrated that these aperiodic regions trap numerous crystal defects migrating along nanodomain boundaries during self-alignment and act as intense vortex pinning centers that significantly enhance the high-field performance of MgB2. This suggests that the density of trapped defects in the wells is much greater than that found in other vortex pinning sources.
Superconductivity, Critical Current Density, And Flux Pinning In Mgb2–X(Sic)X/2 Superconductor After Sic Nanoparticle Doping, S X. Dou, A. V. Pan, S. Zhou, M. Ionescu, Xiaolin Wang, J. Horvat, Hua-Kun Liu, P. R. Munroe
Superconductivity, Critical Current Density, And Flux Pinning In Mgb2–X(Sic)X/2 Superconductor After Sic Nanoparticle Doping, S X. Dou, A. V. Pan, S. Zhou, M. Ionescu, Xiaolin Wang, J. Horvat, Hua-Kun Liu, P. R. Munroe
Josip Horvat
We investigated the effect of SiC nanoparticle doping on the crystal lattice structure, critical temperature Tc, critical current density Jc, and flux pinning in MgB2 superconductor. A series of MgB2–x(SiC)x/2 samples with x = 0–1.0 were fabricated using an in situ reaction process. The contraction of the lattice and depression of Tc with increasing SiC doping level remained rather small most likely due to the counterbalancing effect of Si and C co-doping. The high level Si and C co-doping allowed the creation of intragrain defects and highly dispersed nanoinclusions within the grains which can act as effective pinning centers for …
Effect Of Carbon Substitution On The Superconducting Properties Of Mgb2 Doped With Multi-Walled Carbon Nanotubes And Nano Carbon, W. K. Yeoh, J. Horvat, J. H. Kim, X. Xu, S. X. Dou
Effect Of Carbon Substitution On The Superconducting Properties Of Mgb2 Doped With Multi-Walled Carbon Nanotubes And Nano Carbon, W. K. Yeoh, J. Horvat, J. H. Kim, X. Xu, S. X. Dou
Josip Horvat
We have fabricated the multiwalled carbon nanotube (MWCNT) and nano-C doped MgB2 bulk and wire to investigate the effect of carbon substitution in theMgB2. Carbon substitution into boron site was confirmed by the shrinkage of the lattice parameter with the increasing of the doping level. It was found that the lattice distortion and optimum doping level are different in the CNT and nano-C samples. This can be explained by carbon substitution, which is a more direct substitution process with the nano-C precursor. With CNT doping, carbon substitution only occurred after break out of carbon atoms from CNT. Both dopants showed …