Fully Band Resolved Scattering Rate in MgB2 Revealed by Nonlinear Hall Effect and Magnetoresistance Measurements

We have measured the normal state temperature dependence of the Hall effect and magnetoresistance in epitaxial MgB2 thin films with variable disorders characterized by the residual resistance ratio RRR ranging from 4.0 to 33.3. A strong nonlinearity of the Hall effect and magnetoresistance have been found in clean samples, and they decrease gradually with the increase of disorders or temperature. By fitting the data to the theoretical model based on the Boltzmann equation and ab initio calculations for a four-band system, for the first time, we derived the scattering rates of these four bands at different temperatures and magnitude of disorders. Our method provides a unique way to derive these important parameters in multiband systems.Comment: 4 pages, 4 figure

Effect of electrolytes on electrochemical properties of MmNi(5)-based hydrogen storage alloy

This Project is financially supported by the National Natural Foundations of China (51261003), the Natural Foundations of Guangxi Province (2012GXNSFGA060002; 2011GXNSFD018004; 201201ZD009) Guangxi Experiment center of information science (20130113) and National students’ Innovative Project (101059530) and National students’ Innovative Project (101059530).The effect of electrolytes on the electrochemical properties of MmNi(3.68)Co(0.72)Mn(0.43)Al(0.17) hydrogen storage alloy electrodes has been investigated at 303 K and 273 K. Three electrolytes (EL1, EL2, EL3) were obtained by adding 2 wt%, 4 wt% and 6 wt% LiOH into the original electrolyte EO (6 M/ L KOH), respectively. The results indicate that the addition of LiOH improves the discharge capacity and cycle life at 303 K and 273 K. The highest maximum capacity and capacity retention (after 50th cycles) have been observed in electrolyte EL2. However, the high-rate dischargeability (HRD) decreases gradually from EO to EL3 at the two temperatures because of the addition of LiOH. The corrosion current I-corr from Tafel Polarization curves (TP) and the resistance of the oxide layer R-ol from electrochemical impedance spectroscopy (EIS) indicates that the alloy electrode worked in EL1 has a better anti-corrosion ability. The real surface area of the electrodes estimated with EIS analysis, decrease from 51.95 cm(2) in EO to 15.6 cm(2) in EL2, but increase to 31.59 cm(2) in EL3 after being fully activated. The additional LiOH improves the anti-pulverization ability of alloy powders, delay the loss of active elements within the alloy electrode, resulting in an inproved capacity retention of alloy electrode. Meanwhile, the electrochemical kinetics analysis suggests that the charge-transfer reaction at the interface of electrode surface and electrolyte is the rate-determining step when tested at 303 K and 273 K.Publisher PDFPeer reviewe

Detection of Hepatitis C virus RNA using a novel hybridization chain reaction method that competitively dampens cascade amplification.

The hybridization chain reaction (HCR) is widely used for biosensing. However, HCR does not provide the required sensitivity. In this study, we reported a method to improve the sensitivity of HCR by dampening the cascade amplification. First, we designed a biosensor based on HCR, and an initiator DNA was used to trigger the cascade amplification. Optimization of the reaction was then performed, and the results showed that the limit of detection (LOD) for the initiator DNA was about 2.5 nM. Second, we designed a series of inhibitory DNAs to dampen the HCR cascade amplification, and DNA dampeners (50 nM) were applied in the presence of the DNA initiator (50 nM). One of the DNA dampeners (D5) showed the best inhibitory efficiency of greater than 80%. This was further applied at concentrations ranging from 0 nM to 10 nM to prohibit the HCR amplification caused by a 2.5 nM initiator DNA (the limit of detection for this initiator DNA). The results showed that 0.156 nM of D5 could significantly inhibit the signal amplification (p<0.05). Additionally, the limit of detection for the dampener D5 was 16 times lower than that for the initiator DNA. Based on this detection method, we achieved a detection limit as low as 0.625 nM for HCV-RNAs. In summary, we developed a novel method with improved sensitivity to detect the target designed to prohibit the HCR cascade. Overall, this method could be used to qualitatively detect the presence of single-stranded DNA/RNA

Phase Formation, Microstructure, and Magnetic Properties of Nd14.5Fe79.3B6.2 Melt-Spun Ribbons with Different Ce and Y Substitutions

Phase formation and microstructure of (Nd1-2xCexYx)14.5Fe79.3B6.2 (x = 0.05, 0.10, 0.15, 0.20, 0.25) alloys were studied experimentally. The results reveal that (Nd1-2xCexYx)14.5Fe79.3B6.2 annealed alloys show (NdCeY)2Fe14B phase with the tetragonal Nd2Fe14B-typed structure (space group P42/mnm) and rich-RE (α-Nd) phase, while (Nd1-2xCexYx)14.5Fe79.3B6.2 ribbons prepared by melt-spun technology are composed of (NdCeY)2Fe14B phase, α-Nd phase and α-Fe phase, except for the ribbon with x = 0.25, which consists of additional CeFe2 phase. On the other hand, magnetic properties of (Nd1-2xCexYx)14.5Fe79.3B6.2 melt-spun ribbons were measured by a vibrating sample magnetometer (VSM). The measured results show that the remanence (Br) and the coercivity (Hcj) of the melt-spun ribbons decrease with the increase of Ce and Y substitutions, while the maximum magnetic energy product ((BH)max) of the ribbons decreases and then increases. The tendency of magnetic properties of the ribbons could result from the co-substitution of Ce and Y for Nd in Nd2Fe14B phase and different phase constitutions. It was found that the Hcj of the ribbon with x = 0.20 is relatively high to be 9.01 kOe, while the (BH)max of the ribbon with x = 0.25 still reaches to be 9.06 MGOe. It suggests that magnetic properties of Nd-Fe-B ribbons with Ce and Y co-substitution could be tunable through alloy composition and phase formation to fabricate novel Nd-Fe-B magnets with low costs and high performance

Effect of Cu Substitution and Heat Treatment on Phase Formation and Magnetic Properties of Sm₁₂Co_88−xCu_x Melt-Spun Ribbons

The phase structure and microstructure of Sm12Co88−xCux (x = 0, 2, 4, 6, 8, 10; at.%) as-cast alloys and melt-spun ribbons prepared via the arc-melting method and melt-spun technology were studied experimentally by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). The results reveal that the Sm12Co88−xCux (x = 0) as-cast alloy contains Sm2Co17 and Sm5Co19 phases, while the Sm12Co88−xCux (x = 2) as-cast alloy is composed of Sm2Co17, Sm2Co7 and Sm(Co, Cu)5 phases. Sm2Co17 and Sm(Co, Cu)5 phases are detected in Sm12Co88−xCux (x = 4, 6, 8, 10) as-cast alloys. Meanwhile, Sm12Co88−xCux ribbons show a single SmCo7 phase, which is still formed in the ribbons annealed at 1023 K for one hour. After annealed at 1123 K for two hours, cooled slowly down to 673 K at 0.5 K/min and then kept for four hours, the ribbons are composed of Sm2Co17 and Sm(Co, Cu)5 phases. The magnetic measurements of Sm12Co88−xCux ribbons were performed by vibrating sample magnetometer (VSM). The results exhibit that the maximum magnetic energy product ((BH)max), the coercivity (Hcj) and the remanence (Br) of the Sm12Co88−xCux ribbons increase generally with the increase in Cu substitution. In particular, the magnetic properties of the ribbons annealed at 1123 K and 673 K increase significantly with the increase in Cu substitution, resulting from the increase in the volume fraction of the formed Sm(Co, Cu)5 phase after heat treatment

The Improvement of Dehydriding the Kinetics of NaMgH3 Hydride via Doping with Carbon Nanomaterials

NaMgH3 perovskite hydride and NaMgH3–carbon nanomaterials (NH-CM) composites were prepared via the reactive ball-milling method. To investigate the catalytic effect of CM on the dehydriding kinetic properties of NaMgH3 hydride, multiwall carbon nanotubes (MWCNTs) and graphene oxide (GO) were used as catalytic additives. It was found that dehydriding temperatures and activation energies (ΔE1 and ΔE2) for two dehydrogenation steps of NaMgH3 hydride can be greatly reduced with a 5 wt. % CM addition. The NH–2.5M–2.5G composite presents better dehydriding kinetics, a lower dehydriding temperature, and a higher hydrogen-desorbed amount (3.64 wt. %, 638 K). ΔE1 and ΔE2 can be reduced by about 67 kJ/mol and 30 kJ/mol, respectively. The results suggest that the combination of MWCNTs and GO is a better catalyst as compared to MWCNTs or GO alone

Amorphous Sb2S3 Nanospheres In-Situ Grown on Carbon Nanotubes: Anodes for NIBs and KIBs

Antimony sulfide (Sb2S3) with a high theoretical capacity is considered as a promising candidate for Na-ion batteries (NIBs) and K-ion batteries (KIBs). However, its poor electrochemical activity and structural stability are the main issues to be solved. Herein, amorphous Sb2S3 nanospheres/carbon nanotube (Sb2S3/CNT) nanocomposites are successfully synthesized via one step self-assembly method. In-situ growth of amorphous Sb2S3 nanospheres on the CNTs is confirmed by X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. The amorphous Sb2S3/CNT nanocomposites as an anode for NIBs exhibit excellent electrochemical performance, delivering a high charge capacity of 870 mA h g&minus;1 at 100 mA g&minus;1, with an initial coulomb efficiency of 77.8%. Even at 3000 mA g&minus;1, a charge capacity of 474 mA h g&minus;1 can be achieved. As an anode for KIBs, the amorphous Sb2S3/CNT nanocomposites also demonstrate a high charge capacity of 451 mA h g&minus;1 at 25 mA g&minus;1. The remarkable performance of the amorphous Sb2S3/CNT nanocomposites is attributed to the synergic effects of the amorphous Sb2S3 nanospheres and 3D porous conductive network constructed by the CNTs

Phase formation and magnetic properties of (Nd1−xYx)14Fe80B6 melt-spun ribbons

Phase formation and magnetic properties of (Nd _1−x Y _x ) _14 Fe _80 B _6 (x = 0.1–0.8) alloys were investigated experimentally by x-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The phase structure analysis reveals that the as-cast (Nd _1−x Y _x ) _14 Fe _80 B _6 alloys were made of 2:14:1 phase with tetragonal Nd _2 Fe _14 B-tpyed structure, REFe _2 and α -Fe phases, while the melt-spun ribbons are composed of 2:14:1 phase and α -Fe Phase. Based on the magnetic measurements, the remanence (B _r ), the coercivity (H _cj ), the maximum magnetic energy product ((BH) _max ) and the Curie temperatures (T _c ) of (Nd _1−x Y _x ) _14 Fe _80 B _6 ribbons reduces gradually with increasing Y substitution. The relatively high coercivity (6.75 kOe) of (Nd _0.4 Y _0.6 ) _14 Fe _80 B _6 ribbon with high Y substitution was achieved, which indicates that good magnetic properties of Nd–Y–Fe–B ribbons would be obtained through the design of alloy composition and phase formation