Pei Yao

Facile Synthesis of MoS2/Reduced Graphene Oxide@Polyaniline for High-Performance Supercapacitors.

The molybdenum disulfide/reduced graphene oxide@polyaniline (MoS2/RGO@PANI) was facilely and effectively prepared through a two-stage synthetic method including hydrothermal and polymerized reactions. The rational combination of two components allowed polyaniline (PANI) to uniformly cover the outer face of molybdenum disulfide/reduced graphene oxide (MoS2/RGO). The interaction between the two initial electrode materials produced a synergistic effect and resulted in outstanding energy storage performance in terms of greatest capacitive property (1224 F g(-1) at 1 A g(-1)), good rate (721 F g(-1) at 20 A g(-1)), and cyclic performance (82.5% remaining content after 3000 loops). The symmetric cell with MoS2/RGO@PANI had a good capacitive property (160 F g(-1) at 1 A g(-1)) and energy and power density (22.3 W h kg (-1) and 5.08 kW kg(-1)).

Rapid and effective sample clean-up based on magnetic multiwalled carbon nanotubes for the determination of pesticide residues in tea by gas chromatography–mass spectrometry

In this work, amine-functionalised magnetic nanoparticles and multiwalled carbon nanotubes (MNPs/MWCNTs) composites were synthesised by a simple method and applied as an adsorbent for rapid clean-up of acetonitrile extracts of tea samples prior to analysing eight pesticide residues by gas chromatography-mass spectrometry. Several parameters affecting the sampling and treatment efficiency were investigated, including extraction solvent, sonication time, weight ratio of MWCNTs to MNPs in the composites, amount of adsorbent, clean-up time and washing solution. Under the optimised conditions, the recoveries obtained for each pesticide ranged from 72.5% to 109.1% with relative standard deviations lower than 12.6%. Limit of quantification ranged from 0.02 to 0.08 mg kg⁻¹. The established method was successfully applied to the analysis of pesticide residues in real tea samples. The results indicated that the use of MNPs/MWCNTs composites allowed the simple and expeditious clean-up of complex tea samples for subsequent determination of pesticide residues.

Surface modification of Mg2Ni alloy in an acid solution of copper sulfate and sulfuric acid

Abstract A simple method of electroless copper plating for the surface modification of Mg 2 Ni alloy has been described in this paper. The plating solution contains only copper sulfate and sulfuric acid which are less toxic to the environment than the chemical reagents used in conventional copper plating solutions. Moreover, the coating process was very easy and fast to operate needing no special treatment for air-exposed samples before plating. The phase composition and microstructure of the modified and unmodified Mg 2 Ni alloy were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical characteristics and performance of the electrodes were examined using galvanostatic charge/discharge and cyclic voltammetry techniques. A discharge capacity of 210 mA·h·g −1 Mg 2 Ni has been obtained from the modified Mg 2 Ni alloy. The results show that the surface modification of the Mg 2 Ni alloy electrode can significantly improve its electrochemical characteristics and performance. It is suggested that this copper plating method is very promising for surface modification of the Mg 2 Ni alloy in hydride batteries.

Mg2Ni-based hydrogen storage alloys for metal hydride electrodes

Abstract Mg 2− X M X Ni (M=Ti, Ce; X =0, 0.1, 0.2) and MgNi 1− y N y (N=Mn, Co; y =0, 0.1, 0.2) were prepared by a powder metallurgical sintering technique. The effects of the element substitutions and the ball-milling of the alloy, with or without nickel powder, on the alloy properties were investigated by X-ray diffraction, transmission electron microscopy and the Malvern particle size analyser. Three types of alloys, un-ball-milled, ball-milled without nickel powders and ball-milled with the addition of nickel powders, were used as the active material of metal hydride electrodes. Electrochemical measurements show that ball-milling the alloy with or without nickel powders is an effective method for increasing the discharge capacity and cycle life of the alloy electrode because of the changed phase structure and surface behaviour.

Transmission electron microscopy evidence for phase transformation from Bi2Sr2CuO6 to Bi2Sr2Ca2Cu3O10

The growth mechanism of the Bi-2223 phase was studied using multifilamentary Ag/Bi-2223 tapes manufactured by the powder-in-tube method. X-ray powder diffraction was performed to analyze the developments of Bi-2201, Bi-2212, and Bi-2223 phases during sintering periods at high temperatures. Transmission electron microscopy (TEM) was used to investigate the growth mechanism of the 2223 phase. TEM images indicated that 2201 and Ca2CuO3 crystals come together to form platelets of 2223. The structural phase transformation established a structural frame of the 2223 crystal. There were some vacant defects retaining in the established 2223 crystal cells at copper and oxygen sites after the phase transformation, and the Cu/O compound at high temperatures would diffuse into 2223 cells and occupy the corresponding vacancies to complete the 2223 crystal structure. The present work provides an evidence for growing the 2223 phase from the 2201 phase and Ca2CuO3 in the samples studied.

Structure characteristics and lithium ionic conductivity of La(0.57−2x/3)SrxLi0.3TiO3 perovskites

La(0.57−2x/3)SrxLi0.3TiO3 perovskites were synthesised using a conventional solid-state reaction. Large Sr2+ ions partially substituting for La3+ ions were found to disturb the cubic perovskite structure and cause the superstructure lines to gradually decrease in the x-ray diffraction patterns and almost disappear when x = 0.12. On the contrast, there still exist superstructure diffraction spots in the electron diffraction pattern on microdomain when x = 0.12. The lithium ion conductivities of the compounds were improved in the range of 0 ≤ x ≤ 0.08, which does not obey the principle of the carrier concentration. An expansion of the unit cell and the disordering of La3+ (Sr2+), Li+ ions and vacancies in A sites could be a mechanism for the enhancement of the conductivity with Sr2+ doping.

Note: Axially pull-up electrochemical etching method for fabricating tungsten nanoprobes with controllable aspect ratio.

A mathematical model representing the relation between pulling up speed, time and aspect ratio is reported, accordingly the axially pull-up electrochemical etching method for fabricating nanoprobes is proposed. The tungsten probes with predetermined shape and aspect ratio according to the model were successfully produced with this method. Then the probes were installed inside a micromanipulation system to manipulate the carbon nanotubes and measure their current-voltage (I-V) characteristics. The probe fabrication and application experiments demonstrated the reasonability and reliability of the model and method developed in this note.

Enhancement of Thermal Stability and Cycling Performance of Lithium-Ion Battery at High Temperature by Nano-ppy/OMMT-Coated Separator

Nanopolypyrrole/organic montmorillonite- (nano-ppy/OMMT-) coated separator is prepared by coating nano-ppy/OMMT on the surface of polyethylene (PE). Nano-ppy/OMMT-coated separator with three-dimensional and multilayered network structure is beneficial to absorb more organic electrolyte, enhancing the ionic conductivity (reach 4.31źmS·cm-1). Meanwhile, the composite separator exhibits excellent thermal stability and mechanical properties. The strong covalent bonds (Si-F) are formed by the nucleophilic substitution reaction between Fź from the thermal decomposition and hydrolysis of LiPF6 and the covalent bonds (Si-O) of nano-ppy/OMMT. The Si-F can effectively prevent the formation of HF, POF3, and LiF, resulting in the inhibition of the disproportionation of Mn3+ in LiNi1/3Co1/3Mn1/3O2 material as well as reducing the internal resistance of the cell. Therefore, the nano-ppy/OMMT-coated separator exhibits outstanding capacity retention and cycling performance at 80°C.

Preparation and Characterization of Fe3O4@nSiO2@mSiO2–NH2 Core–Shell Microspheres for Extracting Allura Red from Aqueous Solution

Allura red (AR) is a water-soluble synthetic colorant often used as an additive in the food industry, but excess AR can be harmful to human health. In this work, we report the development of a new removal method for AR by using amino-functionalized microspheres with Fe3O4 cores and twolayer shells composed of SiO2 particles and perpendicularly aligned mesoporous SiO2 (designated Fe3O4@nSiO2@mSiO2–NH2). The material exhibits good dispersibility in aqueous solutions and a high saturation magnetization of 45.68emug−1, and can be magnetically separated efficiently with an external magnet. Importantly, the material has great adsorption capacity of 29.6mgg−1 for AR and the capacity for reuse with a simple treatment. The adsorption process is very fast and the kinetics data are consistent with a pseudo-second order model. Based on these, a rapid and efficient method for extraction and analysis of AR in water and soft drinks has been established.

High electrical performance Ag-sheathed Bi-2223 multifilamentary tapes prepared by an optimised PIT processing route

An optimised PIT processing route is introduced and discussed, using results from experiments investigating the effect of processing on microstructure, and subsequently on J/sub c/ in PIT tapes. At 77 K and self-field, the highest J/sub c/ performance of 51000A/cm/sup 2/ has been obtained for 69-filament tapes. High critical current samples with I/sub c/=108A and J/sub c/=36000A/cm/sup 2/ have been measured at 77 K and self-field for 361-filament tapes. Our results indicated that J/sub c/ is influenced by the Pb distribution of Pb-2212, phase composition for the precursor powder, the deformation reduction rate, and the core thickness. Intermediate processing (cooling, deformation and heating) between thermal-mechanical cycles and finally cooling procedures also play an important role on Bi-2223 phase purity and achievement of such high electrical performance in the tapes.