Solid electrolyte composite Li_4P_2O_7-Li_3PO_4 for lithium ion battery

The researches on solid electrolyte have been significantly increasing due to the safety problem in lithium ion battery.The lithium phosphates are chosen due to environmentally friendly.In the present study Li_4 P_2 O_7 was synthesized by solid state reaction using NH_4 H_2 PO_4 and Li_2 CO_3 with the ratio 1:2 at various temperatures of600 ℃,800 ℃ and 900℃.The products were characterized by x-ray diffraction,scanning electron microscopy and impedance spectroscopy.The x-ray diffraction showed that all samples consisted of two phases.It was found that the products consisted of 52.44% Li_4 P_2 O_7 and 47.56% LiPO_3;93.56% Li_4 P_2 O_7 and 6.44% Li_3 PO_4;and46.27% Li_4 P_2 O_7 and 53.67% Li_3 PO_4 under the synthesizing temperature of 600 ℃,800℃ and 900 ℃,respectively.The highest ionic conductivity of 3.85 ×10~(-5) S/m was achieved for composite Li_4 P_2 O_7-Li_3 PO_4 with the highest content of 93.56% Li_4 P_2 O_7.This conductivity is higher compared with single phase of LiPO_3,Li_3 PO_4 and Li_4 P_2 O_7.The increase in ionic conductivity may be due to the mixed anion effects related to the phosphate networks,and it also corresponds to the existence of anorthic phase Li_4 P_2 O_7 with the space group P-1(2).The crystal lattice analysis showed that the reactant Li_4 P_2 O_7 consisted of diphosphate groups P_2 O_7.The lithium tetrahedral LiO_4 were linked to P_2 O_7 groups formed a continuous framework containing large voids,available for Li~+ ion transport,and thus it exhibited high conductivity.A composite Li_4 P_2 O_7-Li_3 PO_4 is a promising solid electrolyte for solid state battery.     

Scalable synthesis and electrochemical performance of mesoporous graphene from calcium carbonate by magnesiothermic reaction

A novel scalable synthetic method of mesoporous graphene has been developed using the compressed mixture of Mg and excess CaCO₃ in a closed container. The generated solid oxide and unreacted CaCO₃ could act as mesopore-forming agents, and the closed container could prevent the carbon dioxide from CaCO₃ flow away. As a result, the graphenes with a large number of 2–30 ?nm mesopores and high utilization ratio of Mg achieved. The graphenes had high specific surface area and excellent electrochemical performance. In particular, the Mg utilization ratio was up to 53.3% in the preparation of graphene using 2:1 CaCO₃/Mg at 700 ?°C, which is superior to previous researches. The obtained mesoporous graphene exhibited high specific surface area of 743.7 ?m² ?g^-1, large specific capacitance of 140 ?F ?g^-1, and high capacitance retention rate of 64.3%.     

Self-rolled TiO_2 microscroll/graphene composite for electrochemical dopamine sensing

Dopamine is an important neurotransmitter,and nonenzyme electrochemical sensor of dopamine detection based on highly active material is urgently demanded.In this work,an electrochemical sensor with high sensitivity and selectivity based on self-rolled TiO_2microscroll/graphene composite was developed and validated for dopamine sensing.The device exhibited a superior performance for dopamine detection with a detection limit of 4.25×10~(-9)mol L~(-1),and in the dopamine concentration range of 0.06–90μmol L~(-1),the oxidation currents increased linearly with the concentration.The remarkable performance enhancement was mainly ascribed to the increased surface area due to the porous surface of the TiO_2nanomembrane and highly conductive graphene therein.In addition,we have demonstrated that the sensor could be effectively used on detecting dopamine concentrations in urine samples.Our work demonstrates that the current microscroll-based device is promising in the field of real-time health monitoring for future human community.     

Fabrication of anode-supported zirconia thin film electrolyte based core–shell particle structure for intermediate temperature solid oxide fuel cells

With a view to produce intermediate temperature SOFCs,yttria and scandia doped zirconia with a core-shell structure was prepared,then an anode supported fuel cell was fabricated by a spray method.The influences of the scandia content in the electrolyte and atmosphere conditions used in the testing experiments on phase composition,microstructure and fuel cell performance were investigated.The electrolyte was composed of cubic and tetragonal phases and SEM pictures revealed very fine grain sizes and a smooth surface of the electrolyte film,though some defects were observed in samples with high Scandia content.Coating scandia on partially stabilized zirconium particles improves both ionic conductivity of the electrolyte and power density of the fuel cell distinctly below 750 1C.Anodes were pre-sintered at 1200 1C before co-sintering with the electrolyte film to ensure that the shrinkage percentage was close to that of the electrolyte during co-sintering,avoiding warping of cell.     

Mangosteen peel-derived activated carbon for supercapacitors

This work reports the effects of activation temperatures on the porous development and electrochemical performance of activated carbons. Herein, activated carbons were prepared from the biowaste of mangosteen peel by using KOH activation at temperatures of 400, 600, and 800 ?°C. The results demonstrate that the specific surface area increases with increasing the activation temperatures in which the well-developed porous structure after KOH activation at 800 ?°C provides the highest specific surface area of 1039 ?m² ?g^?1. At 600 ?°C, the activated carbon delivers the highest specific capacitance value of 182 ?F ?g^?1 ?at a current density of 0.5 ?A ?g^?1 in 3 ?M KOH aqueous electrolyte. This is correlated well with its high micropore fractions (99%). Moreover, it was found that the activation temperature changes the major contribution of oxygen-containing functional group on surface of activated carbon, which is beneficial for the enhancement of the specific capacitance value of activated carbon at the temperature of 600 ?°C. This work suggests that the activation temperature is a key to optimizing the electrochemical performance of activated carbons. Overall, our activated carbons can be considered as a strong candidate for use as electrode materials in supercapacitors.     

Hot deformation behavior andfl ow stress modeling of annealed AZ61 Mg alloys

In this study, the hyperbolic-sine type constitutive equation was used to model the flow stress of annealed AZ61 magnesium(Mg) alloys. Hot compression tests were conducted at the temperatures ranging from 250 1C to 450 1C and at the strain rates ranging from 1 10–3s 1to 1 s 1on a Gleeble-3500 thermo-simulation machine. Constitutive equations as a function of strain were established through a simple extension of the hyperbolic sine constitutive relation. The effects of annealing heat treatments on the variations in constitutive parameters with strain were discussed. The hot compressive flow curves exhibited typical features of dynamic recrystallization. Multiple peak flow curves were observed in the annealed specimens upon testing at a strain rate of 1 10 1s–1and at various temperatures. Variations in constitutive parameters with strain were related to flow behavior and dependent on the initial conditions of the test specimens. The flow stresses of annealed AZ61 Mg alloys were predicted well by the strain-dependent constitutive equations of the hyperbolic sine function under the deformation conditions employed in this study.     

Microstructure and growth kinetics of Ce and Y jointly modified silicide coatings for Nb–Ti–Si based ultrahigh temperature alloy

In order to protect Nb-Ti-Si based ultrahigh temperature alloy from oxidation, pack cementation processes were utilized to prepare Ce and Y jointly modified silicide coatings. The Ce and Y jointly modified silicide coating has a double-layer structure: a relatively thick (Nb, X)Si2 (X represents Ti, Cr and Hf elements) outer layer and a thin (Ti, Nb)5Si4 transitional layer. The pack cementation experiments at 1150 ℃ for 8 h proved that the addition of certain amounts of CeO2 and Y2O3 powders in the packs distinctly influenced the coating thickness, the contents of Si, Ce and Y in the (Nb, X)Si2 outer layers, and the density of cavities in the coatings. In order to study the effects of Ce and Y joint modification in the silicide coatings, both only Ce and only Y modified silicide coatings were also prepared for comparison. The mechanisms of the beneficial effects of Ce and Y are discussed. A pack mixture containing 1.5CeO2-0.75Y2O3 (wt%) powders was employed to investigate the growth kinetics of the Ce and Y jointly modified silicide coating at 1050, 1150 and 1250 ℃. It has been found that the growth kinetics obeyed parabolic laws and the parabolic rate constants were 109.20 mm2/h at 1050 ℃, 366.75 mm2/h at 1150 ℃ and 569.78 mm2/h at 1250 ℃, and the activation energy for the growth of the Ce and Y jointly modified silicide coating was 197.53 kJ/mol.     

Properties of garnet-type Li6La3ZrTaO12 solid electrolyte films fabricated by aerosol deposition method

The garnet-type Li_6La_3ZrTaO_(12)(LLZT) solid electrolyte films were fabricated by aerosol deposition(AD)method.Ball-milled LLZT powder with a cubic garnet structure and a particle size of 1-2 urn was used as raw material and deposited directly on a SUS316L or a glass substrate via impact consolidation.As-deposited LLZT film has a cubic garnet structure but contains Li_2CO_3 and La_2Zr_2O_7 phases.SEM observation revealed that the film consists of LLZT particles fractured into submicron size.The impurity phase formation during AD process was caused by the local heating by the collision between LLZT particles and deposition surface and reaction with CO_2.The Li~+ ion conductivity of LLZT film was estimated to be 0.24 × 10~(-5)S cm~(-1) at room temperature.Electronic conductivity of LLZT film was confirmed to be around 10~(-12) S cm~(-1),indicating the dominant Li~+ ion conduction of LLZT film.     

Microstructure, mechanical and thermo-physical properties of hot-pressed Al2O3-GdAlO3-ZrO2 ceramics with eutectic composition

A low cost chemical co-precipitation method was employed to fabricate nanoscale Al_2O_3-GdAlO_3-ZrO_2 powder with eutectic composition. A careful control of reaction conditions was required during the preparation. The synthesized nanopowders exhibited a particle size of 20-200 nm, and were highly dispersive and uniform. The results showed that calcination temperature had an important influence on the phase constituents of the nanopowders. With increasing the calcination temperature, a phase transformation from θ-Al_2O_3 to α-Al_2O_3 and a thermal decomposition from Gd_3 Al_5O_(12)(GdAG) to GdAlO_3 and α-Al_2O_3 occurred in sequence. A calcination temperature of 1300 ℃ was needed for the crystallization of α-Al_2 O_3. These nanosized powders were consolidated via hot pressing to produce a fully densified ceramic composite with eutectic composition. The Al_2O_3-GdAlO_3-ZrO_2 ceramic hot-pressed at 1500 ℃ exhibited a relative density of 99.4%, a flexural strength of 485 MPa and a fracture toughness of 6.5 MPa m~(1/2). The ceramic had a thermal conductivity of 1.9 W m K~(-1) at 1200 ℃ and a thermal expansion coefficient of 9.49 ×10~(-6) K~(-1) at 1100 ℃.     

Grain size-dependent electrical resistivity of bulk nanocrystalline Gd metals

The electrical resistivity of the as-consolidated and coarse-grained bulk gadolinium(Gd) metals was studied in the temperature range of 3-315K.The experimental results showed that with decrease in the grain size of Gd grains from micrometer to nanometer range,the room temperature electrical resistivity increased from 209.7 to 333.0 μΩcm,while the electrical resistivity at the low temperature of 3K was found to increase surprisingly from 16.5 to 126.3 μΩcm.The room temperature coefficient resistivity(TCR) values were obtained as 39.2×10-3,5.51×10-3 and 33.7×10-3K-1.The ratios of room temperature to residual resistivity [RRR=ρ(300K)/ρ(3K)] are 2.64,11.0,respectively,for the as-consolidated samples at 280℃ and 700℃ with respect to that of the coarse-grained sample.All results indicate the remarkable influence of the nanostructure on the electrical resistivity of Gd due to the finite size effect and large fraction of grain boundaries.     

Electroch emical properties and interfacial reactions of LiNi0.5Mn1.5O4-δ nanorods

LiNi0.5Mn1.5O4-δ which possesses a high voltage of 4.7 V vs.Li+/Li and stable structure has been considered as a promising cathode material for high energy Li-ion batteries.In this study,well-crystalli...     

Effect of CuO addition on the sintering temperature and microwave dielectric properties of CaSiO3– Al2O3 ceramics

CuO-doped CaSiO3–1 wt% Al2O3 ceramics were synthesized via a traditional solid-state reaction method, and their sintering behavior,microstructure and microwave dielectric properties were investigated. The results showed that appropriate CuO addition could accelerate the sintering process and assist the densification of CaSiO3–1 wt% Al2O3 ceramics, which could effectively lower the densification temperature from1250 1C to 1050 1C. However, the addition of CuO undermined the microwave dielectric properties. The optimal amount of CuO addition was found to be 0.8 wt%, and the derived CaSiO3–Al2O3ceramic sintered at 1100 1C presented good microwave dielectric properties of εr?7.27,Q f?16,850 GHz and τf? 39.53 ppm/1C, which is much better than those of pure CaSiO3 ceramic sintered at 1340oC(Q f?13,109 GHz).The chemical compatibility of the above ceramic with 30 Pd/70 Ag during the cofiring process has also been investigated, and the result showed that there was no chemical reaction between palladium–silver alloys and ceramics.& 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.     

Electrochemistry study on PEO-LiClO<Subscript>4</Subscript>-ZSM5 composite polymer electrolyte

Allsolid-statelithiumpolymerbatteriesmaybeoneofthebestchoicesforelectrochemicalpowersourceofthefuturecharacterizedbyitshighenergydensities,goodcyclability,reliabilityandsafety[1,2].PEO-LiXbasedpoly-merelectrolyteshadreceivedextensiveattention[4,5],foritspotentialcapabilitytobeusedascandidatematerialforthetraditionalliquidelectrolytes,sinceWrightetal.foundthatthecomplexofPEOandalkalinesaltshadtheabilityofionicconductivityin1973[3].ThegeneralconceptofthetransportofLi+inthepolymerelectrolytewa…     

Zr-pillared montmoril lonite supported cobalt nanoparticles for Fischer – Tropsch synthesis

In this article Fischer–Tropsch(FT) synthesis was studied over cobalt nanoparticles supported on modifed Montmorillonite(Zr-PILC).Co-loaded/Zr-PILC catalysts were synthesized by hydrothermal methods and were characterized by XRD,XRF,BET,H2-TPR,TGA and SEM techniques.FT reactions were carried out in fxed bed microreactor(T 225 1C,260 1C and 275 1C,P 1,5 and 10 bars).The FT-products obtained over Co-loaded/Zr-PILC catalysts showed increased selectivity of C2–C12hydrocarbons and decreased selectivity towards CH4and higher molecular weight hydrocarbons(C21) at a TOS of 2–30 h as compared to the Co-loaded/NaMMT catalysts.With increase in reaction temperature from225 1C to 275 1C,CO-conversion and CH4selectivity increases while that of C5+hydrocarbons decreases.Decrease in CH4selectivity while increase in C5+hydrocarbons and CO-conversion were observed on increasing the pressure of reaction.     

In-situ secondary growth of nanocube-based Prussian-blue film as an ultrasensitive biosensor

A regular nanostructure has been widely confirmed to result ina marked improvement in material performance in biosensing applications.In the present study,a regular nanostructured Prussian blue(PB) film with two heterogeneous crystal layers was synthesized in-situ using a secondary growth method.A PB seed layer was first controlled to form uniform cube-like crystal nuclei through an ultrasonic reaction with a single reactant.Then,well-defined 100 nm PB nanocubes were further crystallized on this seed layer using a self-assembly approach.In order to accelerate the electron transfer rate during the enzyme reaction for glucose detection,the graphene was used as the main cross-linker to immobilize glucose oxidase on the PB film.The as-prepared biosensor exhibited high electrocatalysis and electron conductivity for the detection of trace glucose with a sensitivity of141.5 μA mM~(-1) cm~(-2),as well as excellent anti-interference ability in the presence of ascorbic acid and uric acid under a low operation potential of-0.05 V.     

Activated carbon derived from rice husk by NaOH activation and its application in supercapacitor

Four activated carbon(AC) samples prepared from rice husk under different activation temperatures have been characterized by N2adsorption–desorption isotherms, thermogravimetric analysis(TGA–DTA), Fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM). The specific surface area of AC sample reached 2681 m2 g 1under activation temperature of 800 1C. The AC samples were then tested as electrode material; the specific capacitance of the as-prepared activated carbon electrode was found to be 172.3 F g 1using cyclic voltammetry at a scan rate of 5 mV s 1and 198.4 F g 1at current density 1000 mA g 1in the charge/discharge mode.& 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.     

Building well-defined hierarchical nanostructures for sulfur and silicon electrodes

Huge volume expansion of electrode materials (e.g. 80% for sulfur and 310% for silicon) in the electrochemical lithiation reaction is seen as a root-cause of fast capacity fading of rechargeable lithium batteries. In this work, an effective solution is demonstrated by fabricating thin film sulfur and silicon electrodes with hierarchical structure of sulfur (or silicon) particles sandwiched between adjacent reduced graphene oxide (rGO) layers. The hierarchical films are constructed via vacuum filtration assisted layer-by-layer assembly of rGO and the respective precursor particles, i.e. zinc sulfide or silica shelled by super-sticky polydopamine. Polydopamine serves as a glue of rGO layers to furnish good mechanical integrity to the structure, and the precursor of nitrogen-doped carbon upon high-temperature calcination to ensure the electrical contacts between rGO layers. Zinc sulfide is oxidized to the electrochemically active sulfur by soaking in ferric aqueous solution, while silica is reduced to nanosized silicon in magnesium vapor at high temperature. The electrochemical studies reveal that the binder-free hierarchical electrodes can tolerate the volume change upon lithiation/delithiation, giving high initial Coulombic efficiency and good capacity retention. The rGO layers in the sulfur electrode is also found to effectively mitigate the diffusion of polysulfides into electrolyte.     

石墨烯/聚苯胺复合膜修饰玻碳电极测定多巴胺

采用原位聚合法制备石墨烯/聚苯胺复合物,利用X射线衍射技术和红外光谱进行表征,通过滴涂法制备修饰电极,对多巴胺进行电化学测定。分别对支持电解质、pH值和扫描速率等实验条件进行了优化,建立了测定多巴胺的新方法。实验结果表明,经石墨烯/聚苯胺修饰后的玻碳电极对多巴胺具有很好的催化氧化作用。在0.1mol/L磷酸盐缓冲溶液中(pH值为4.0),多巴胺的线性响应范围为8.0×10-7~5.0×10-3 mol/L,相关系数为0.994,检出限为9.8×10-8 mol/L。该法用于实际样品中多巴胺的测定,回收率为97.1%~103.4%。     

Effects of homogenization on the dissolution and precipitation behaviors of intermetallic phase for a Zr and Er containing Al-Zn-Mg-Cu alloy

The effects of homogenization on dissolution and precipitation behaviors of intermetallic phase in a novel Zr and Er containing Al-Zn-Mg-Cu alloy were investigated.In this work,single-stage(SS:475℃/24 h) and doublestage(DS:400℃/12 h+475℃/24 h) homogenization treatments were carried out for the ingots with the heating rates of 300℃/h,50℃/h and 25℃/h,respectively.It was found that Er tended to segregate at the grain boundary in the form of Al_8Cu_4Er,and the formation mechanism was determined to be the eutectic reaction in the front of the solid/liquid interface during solidification.Also,Al_8Cu_4Er phase was detected to possess high melting point(～573.8℃),which fully remained after the homogenization.Meanwhile,a significant impact of heating rate on the dissolution of intermetallic phases for the studied alloy under the DS homogenization was determined,but little impact was observed under the SS homogenization.Morever,the size and distribution of the dispersoids after homogenization were fully analyzed.It was found that slow heating rates was helpful to refine the particles size,and increase the density as well as volume fraction of the precipitation under both SS and DS homogenization.However a higher density and volume fraction of the precipitated particles,and a relatively larger average particle size were gained with DS homogenization.     

First scanning Fabry–Perot interferometer developed in China

A scanning Fabry–Perot interferometer (SFPI) was first developed and deployed at the Langfang near Space Environment Field Scientific Observation Station (39.38°N, 116.65°E) of the National Space Science Center, CAS. The instrument is designed to measure the mesospheric and thermospheric wind velocities using the atomic oxygen 557.7-nm and 630.0-nm emissions. Data from February 28 to March 3 and February 28 to March 15 in 2011 were chosen for case study and mean value study, respectively. The errors of the meridional and zonal winds are 6.5 and 7.5 m/s at 557.7-nm and at 630.0-nm, they are 7.1 and 6.6 m/s, respectively. During the whole experiment, the instrument has performed in good condition and provided high-quality data. The mean neutral wind data were consistent with that predicted by HWM07. Good agreement has been found in between the SFPI and a neighbor Meridian Project Fabry–Perot interferometer (MP FPI), with a corresponding coefficient (r ²) larger than 80 %. In general, the scanning FPI meets the design goal, and it is a useful ground-based instrument for measuring mesospheric and thermospheric winds at middle latitudes and is able to provide high-quality data for future scientific studies.