173 research outputs found
Low-temperature synthesis of SmFeAsO0.7F0.3 wires with high transport critical current density
Ag-sheathed SmFeAsO0.7F0.3 (Sm-1111) superconducting wires were prepared by a
one-step solid state reaction at temperatures as low as 850~900C, instead of
commonly used temperatures of 1150~1250C. The X-ray diffraction pattern of the
as-sintered samples is well indexed on the basis of tetragonal ZrCuSiAs-type
structure. We characterized transport critical current density Jc of the
SmFeAsO0.7F0.3 wires in increasing and subsequently decreasing fields, by a
resistive four-probe method. A transport Jc as high as ~1300 A/cm^2 at 4.2 K
and self field has been observed for the first time in Sm-1111 type
polycrystalline superconductors. The Jc also shows a rapid depression in small
applied fields as well as a magnetic-history dependence, indicating weak-linked
grain boundaries. The low-temperature synthesis method can be very beneficial
to fabricating the RE-1111 iron oxynictides in a convenient and safe way.Comment: 12 pages, 3 figure
Evidence for topological semimetallicity in a chain-compound TaSe3
Among one-dimensional transition-metal trichalcogenides, TaSe3 is unconventional in many respects. One is its strong topological semimetallicity as predicted by first-principles calculations. We report the experimental investigations of the electronic properties of one-dimensional-like TaSe3 single crystals. While the b-axis electrical resistivity shows good metallicity with a high residual resistivity ratio greater than 100, an extremely large magnetoresistance is observed reaching ≈7 × 103% at 1.9 K for 14 T. Interestingly, the magnetoresistance follows the Kohler’s rule with nearly quadratic magnetic field dependence, consistent with the electron–hole compensation scenario as confirmed by our Hall conductivity data. Both the longitudinal and Hall conductivities show Shubnikov-de Haas oscillations with two frequencies: Fα ≈ 97 T and Fβ ≈ 186 T. Quantitative analysis indicates that Fα results from the two-dimensional-like electron band with the non-trivial Berry phase [1.1π], and Fβ from the hole band with the trivial Berry phase [0(3D) − 0.16π(2D)]. Our experimental findings are consistent with the predictions based on first-principles calculations
Hollow carbon spheres as an efficient dopant for enhancing critical current density of MgB2 based tapes
A significant enhancement of Jc and Hirr in MgB2 tapes has been achieved by
the in situ powder-in-tube method utilizing hollow carbon spheres (HCS) as
dopants. At 4.2 K, the transport Jc for the 850C sintered samples reached
3.1x10^4, and 1.4x10^4 A/cm^2 at 10 and 12 T, respectively, and were better
than those of optimal nano-SiC doped tapes. Furthermore, the Hirr for doped
sample was raised up to 16.8 T at 10 K due to the carbon substitution effect.
The results demonstrate that HCS is one of the most promising dopants besides
nano-carbon and SiC for the enhancement of current capacity for MgB2 in high
fields.Comment: 14 pages, 5 figure
Superconductivity induced by doping Rh in CaFe2-xRhxAs2
In this paper we report the synthesis of iron-based superconductors
CaFe2-xRhxAs2 using one-step solid state reaction method, which crystallizes in
the ThCr2Si2-type structure with a space group I4/mmm. The systematic evolution
of the lattice constants demonstrates that the Fe ions are successfully
replaced by the Rh. By increasing the doping content of Rh, the
spin-density-wave (SDW) transition in the parent compound is suppressed and
superconductivity emerges. The maximum superconducting transition temperature
is found at 18.5 K with the doping level of x = 0.15. The temperature
dependence of DC magnetization confirms superconducting transitions at around
15 K. The general phase diagram was obtained and found to be similar to the
case of Rh-doping Sr122 system. Our results explicitly demonstrate the
feasibility of inducing superconductivity in Ca122 compounds by higher
d-orbital electrons doping, however, different Rh-doping effect between FeAs122
compounds and FeAs1111 systems still remains an open question.Comment: 15 pages, 6 figure
Redox flow desalination based on the temperature difference as a driving force
How to effectively reduce the consumption of electrical energy is a key topic in many studies of electrochemical desalination. In this work, we use the temperature difference to drive a continuous process of dialysis desalination. The system consists of a thermoelectric unit and a desalination unit connected in series. The thermoelectric unit includes a thermoelectric generator (TEG), a heater as heat source and an air-cooled heat sink to generate electricity and for the desalination unit. The desalination unit contains two platinum-coated hydrophobic carbon cloths as current collectors, a mixture of [Fe(CN)6]3-/4- as anolyte and catholyte, concentrated and diluted salt streams with two cationic and one anionic exchange membranes separated configuration (CEM|AEM|CEM). During the charging process driven by temperature difference, chloride and sodium ions in the diluted salt stream move to the concentrated salt stream and cathodic reservoir, respectively. The results show that the concentration of brine drops significantly from 5,000 ppm to 344.3 ppm as the current decreases to 0.06 mA from the initial 1.30 mA when the temperature difference is maintained at 65 K. Concurrently, the average salt removal rate is up to 8.8 μg cm-2 min-1 and average heat consumption is 284.3 MJ mole-1. Moreover, the influences from the temperature difference, salt feeds content and electrolyte concentration are also investigated in detail. This research has the potential application for the freshwater obtainment via the utilization of waste heat, and will be significant in places with the shortage of the electrical energy such as ships, islands and oceans with the temperature differences
Superconductivity in Co-doped SmFeAsO
Here we report the synthesis and basic characterization of SmFe1-xCoxAsO
(x=0.10, 0.15). The parent compound SmFeAsO itself is not superconducting but
shows an antiferromagnetic order near 150 K, which must be suppressed by doping
before superconductivity emerges. With Co-doping in the FeAs planes,
antiferromagnetic order is destroyed and superconductivity occurs at 15 K.
Similar to LaFe1-xCoxAsO, the SmFe1-xCoxAsO system appears to tolerate
considerable disorder in the FeAs planes. This result is important, which
indicates difference between cuprare superconductors and the iron-based
arsenide ones.Comment: 11 pages, 3 figure
Structural and critical current properties in polycrystalline SmO1-xFxFeAs
A series of polycrystalline SmO1-xFxFeAs bulks (x=0.15, 0.2, 0.3 and 0.4)
were prepared by the conventional solid state reaction. Resistivity,
susceptibility, magnetic hysteresis, critical current density and
microstructure of these samples have been investigated. It is found that
critical transition temperature Tc increases steadily with increasing fluorine
content, with the highest onset Tc=53 K at x=0.4. On the other hand, the
superconductivity seems correlated with lattice constants; that is, Tc rises
with the shrinkage of a-axis while resistivity increases with the enlargement
of c-axis. A global critical current density of 1.1x10^4 A/cm^2 at 5 K in self
field was achieved in the purest sample. A method of characterization of
inter-grain current density is proposed. This method gives an inter-grain Jc of
3.6x10^3 A/cm^2 at 5 K in self field, in contrast to the intra-grain Jc of 10^6
A/cm^2. The effect of composition gradients on the inter-grain Jc in
SmO1-xFxFeAs is also discussed.Comment: 18 pages, 7 figure
Ultrasound-assisted aqueous enzymatic extraction of oil from perilla seeds and determination of its physicochemical properties, fatty acid composition and antioxidant activity
Variants in the ITPA Gene Protect Against Ribavirin-Induced Hemolytic Anemia and Decrease the Need for Ribavirin Dose Reduction
In a genome-wide association study of patients being treated for chronic hepatitis C, 2 functional variants in ITPA that cause inosine triphosphatase (ITPase) deficiency were shown to protect against ribavirin (RBV)-induced hemolytic anemia during early stages of treatment. We aimed to replicate this finding in an independent cohort from the Study of Viral Resistance to Antiviral Therapy of Chronic Hepatitis C and to investigate the effects of these variants beyond week 4
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