The effect of different concentrations of Na2SnO3 on the electrochemical behaviors of the Mg-8Li electrode

In this research, the effect of the different concentrations of NaSnO₃ as the electrolyte additive in 0.7 mol L^?1 NaCl solution on the electrochemical performances of the magnesium-8lithium (Mg-8Li) electrode are investigated by methods of potentiodynamic polarization, potentiostatic current-time, electrochemical impedance technique, and scanning electron microscopy (SEM). The corrosion resistance of the Mg-8Li electrode is improved when Na₂SnO₃ is added into the electrolyte solution. The potentiostatic current-time curves show that the electrochemical behaviors of the Mg-8Li electrode in the electrolyte solution containing 0.20 mmol L^?1 Na₂SnO₃ is the best. The electrochemical impedance spectroscopy results indicate that the polarization resistance of the Mg-8Li electrode decreases in the following order with the concentrations of Na₂SnO₃: 0.05 mmol L^?1?>?0.00 mmol L^?1?>?0.30 mmol L^?1?>?0.10 mmol L^?1?>?0.20 mmol L^?1. The scanning electron microscopy studies indicate that the electrolyte additive prevents the formation of the dense oxide film on the alloy surface and facilitates the peeling off of the oxidation products.     

Molybdate and molybdate/permanganate conversion coatings on Mg-8.5Li alloy

A novel environment-friendly conversion coating for Mg-8.5Li alloy was obtained by immersing in a solution of molybdate. The concentration of ammonium molybdate and the addition of potassium permanganate were discussed in this experiment. The surface morphology of the conversion coatings was observed by scanning electron microscopy (SEM), and the chemical composition was investigated by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The corrosion resistance of Mg-8.5Li alloy and conversion coatings were investigated by means of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurement. The results showed that the coatings with cracked morphology were homogeneous and uniform. The conversion coatings were mainly composed of metal-oxide as detected by XPS. The results of electrochemical measurement and weight loss measurement revealed that the molybdate conversion coating had better corrosion resistance than bare alloy and chromate conversion coating, and the molybdate/permanganate conversion coating had lower corrosion current density and higher coating resistance than the molybdate conversion coating.     

The effect of multiple pulse treatment on the recrystallization behavior of Mg-3Al-1Zn alloy strip

The present study first reports the application of multiple pulse treatment (MPT) for recrystallizaion of Mg-3Al-1Zn (AZ31) alloy strip. It is surprising and exciting that the completed recrystallization state of sample subjected to the electropulsing can be obtained rapidly in ∼10 s at relatively lower temperatures compared with conventional heat treatment. MPT also features excellent mechanical property and typical ductile failure thanks to ultrafine grained microstructure. The favoring mechanism of recrystallization of MPT can be attributed to the coupled actions of the thermal and athermal effects, thereinto, the latter one activates dislocations climb effectively. PACS 81.40.Ef; 84.30.Sk; 62.20 Mk; 61.72.Cc; 66.30.Qa     

Laser surface alloying of an electroless Ni–P coating with Al-356 substrate

Laser surface alloying of an electroless plating Ni–P coatings on an Al-356 aluminium alloy was carried out using a 1-kW pulsed Nd:YAG laser. The microstructure, chemical composition and phase identification of the alloyed layer were determined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffractometry (XRD), respectively. It was shown that laser surface treatment produced a relatively smooth, crack-free and hard surface layer. The hardness of the surface significantly increased due to the formation of the uniformly distributed fine Ni–Al intermetallic phases. The corrosion behaviour of the surface alloyed specimens in 3.5% NaCl solution at 23 °C was also determined by electrochemical techniques. The laser-alloyed surface showed an improved corrosion and pitting potential compared to the substrate as well as the plated Ni–P coating.     

Li_2O-Al_2O_3-SiO_2-P_2O_5系统微晶玻璃受控析晶分析

应用DTA,XRD,SEM等手段研究了Li2O_Al2O3_SiO2_P2O5系统微晶玻璃的析晶过程和相组成。采用模拟计算方法考察了不同的析晶条件。引入适量的Al2O3等难熔物组分来改变析晶条件及残留玻璃相的组成和粘度。通过抑制主晶相(Li2O.2SiO2)晶粒的生长,最终获得了晶粒尺寸为0.1~0.3μm的透明微晶玻璃。     

真空热处理碳纳米管的储氢性能研究

研究了真空热处理对多壁碳纳米管(MWNTs)电化学储氢性能的影响.采用化学气相沉积法(CVD)制备碳纳米管，碳纳米管与LaNi₅储氢合金按质量比1∶10混合，制作成CNTs-LaNi₅电极.电解池采用三电极体系，6mol/L KOH为电解液，Ni(OH)₂为正极，Hg/HgO为参比电极.实验结果表明，在相同的充放电条件下，850℃时CNTs-LaNi₅电极的储氢性能最好，克容量最大为503.6mAh/g，相应的平台电压高达1.18V.从500—850℃随着温度升高，放电量有较大幅度的增加，但到950℃时放电量反而下降.由此可见，碳纳米管的热处理温度对碳纳米管的电化学储氢性能有着较大的影响. 关键词： 碳纳米管(CNTs) 储氢性能 5合金')" href="#">LaNi₅合金 化学气相沉积法(CVD法)     

Electrical discharge machining of titanium alloy (Ti-6Al-4V)

In this study, the electrical discharge machining (EDM) of titanium alloy (Ti-6Al-4V) with different electrode materials namely, graphite, electrolytic copper and aluminium and process parameters such as, pulse current and pulse duration were performed to explore the influence of EDM parameters on various aspects of the surface integrity of Ti6Al4V. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrograph (EDS) and hardness analysis were performed. The experimental results reveal that the value of material removal rate, surface roughness, electrode wear and average white layer thickness are tendency of increase with increasing current density and pulse duration. However, extremely long-pulse durations such as 200 μs led to decrease MRR and surface roughness. Furthermore, the surface hardness is increasing due to the Ti₂₄C₁₅ carbides formed on the surface and obvious cracks are always evident in re-solidified layer when machining copper electrode. The surface crack densities and critical crack lines were determined for the tested material. The graphite electrode is beneficial on material removal rate, electrode wear and surface crack density but relatively poorer surface finish.     

LED用红色发光材料 Li3Ba2Ln3-xEux(MoO4)8的制备及性能

采用溶胶-凝胶法合成了发光二极管(LED)用的系列红色荧光粉Li₃Ba₂Ln_3-xEu_x(MoO₄)₈ (Ln=La, Gd, Y)。利用差热-热重(TG-DTA)分析和粉末X 射线衍射(XRD)测定了其最佳合成温度和不同温度下所得样品的结构,发现所有样品均具有单斜结构;采用荧光光谱对所得荧光粉发光性能进行了表征,发现在相同条件下所得样品的发光强度顺序为:Li₃Ba₂Y_2.8Eu_0.2(MoO₄)₈＞Li₃Ba₂Gd_2.8Eu_0.2(MoO₄)₈＞Li₃Ba₂La_2.8Eu_0.2-(MoO₄)₈。它们在395 nm和465 nm的激发光源激发时均有强的吸收,与LED芯片发射波长相匹配。同时分析了柠檬酸及分散剂聚乙二醇(PEG-10000)的用量、Eu³⁺离子的浓度以及焙烧温度等因素对荧光粉发光性能的影响。     

Crystalline Sb–Cu alloy films as anode materials for Li-ion rechargeable batteries

A crystalline Sb–Cu alloy is investigated for use in Li-ion rechargeable batteries, and its structural, electrochemical and thermal properties are characterized. A pulse electrodeposition method is used to prepare Sb–Cu alloy film on Cu foil as a negative electrode. The structure of the alloy film electrode is characterized using XRD, FE-SEM and EDX. The electrochemical behavior of the Sb–Cu alloy film is investigated at the current rate of 0.1C to the cut-off potential range of 1.8 and 0.01 V vs. Li/Li⁺. Our experimental results demonstrate that the initial discharge capacity is 850 mAh g^?1 and that the discharge capacity increases to 1034 mAh g^?1 at the end of the 30th cycle with a stable cycle life. The Coulombic efficiency is approximately 83.5% with good cyclability. Moreover, the crystalline Sb–Cu alloy film has relatively low exothermic properties, and it may be an interesting candidate for use in the negative electrodes of Li-ion batteries.     

An electrochemical and structural investigation of porous composite anode materials for LIB

A porous composite anode for lithium ion battery (LIB) was investigated. The composite anode was prepared by electrodepositing Sn?CSb alloy on a template-like electrode and then annealing it in the atmosphere of N₂, whereas the porous template-like electrode was obtained by forming a sponge-like porous membrane on a copper foil via a mixed phase inversion process, followed by pre-plating Cu through membrane pores in it. SEM and XRD results showed that composite structure of the anode consisted of electrodeposited Sn?CSb alloy dispersed in a PAN-pyrolyzed conjugated conducting polymer gridding, which was tightly connected with the Cu foil through transition alloy layer formed by heat treatment. Due to its relatively reasonable microcosmic structure, the composite anode presented better cycling performance and specific capacity retention during charging and discharging at diverse rates. When cycled between 0 and 2.0?V (vs Li/Li⁺) at 0.5?C rate, the reversible charge/discharge capacity of the composite material remained 415 and 414.8?mAh?g^?1, respectively, after 30 cycles, corresponding to 82.9% of the capacity retention. When charging and discharging at 2?C rate, the composite material electrode showed 71.7% capacity retention at the 30th cycle.     

Electrochemical performance of La2O3-coated layered LiNiO2 cathode materials for rechargeable lithium-ion batteries

Uncoated and La₂O₃-coated LiNiO₂ cathode materials were synthesized by polymeric sol gel process using metal nitrate precursors at 600 °C for 10 h. The structure and electrochemical properties of the surface-coated LiNiO₂ materials were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry, charge/discharge and electrochemical impedance spectroscopy techniques. X-ray powder diffraction and SEM result show that no significant bulk structural differences were observed between the lanthanum oxide coated and pristine LiMn₂O₄. The galvanostatic charge/discharge studies on the uncoated and lanthanum oxide-coated LiNiO₂-positive material at 0.5-C rate in the potential range between 3 and 4.5 V revealed that lanthanum oxide-coated positive electrode material has enhanced charge/discharge capacities; 2.0 wt.% of lanthanum oxide-coated LiNiO₂-positive material has satisfied the structural stability, high reversible capacity and high electrochemical performances.     

Pt-Ni alloy nanoparticles supported on CNF as catalyst for direct ethanol fuel cells

Carbon nanofiber (CNF) network supported Pt and Pt-Ni alloy nano particle catalysts were prepared by electrochemical deposition at different deposition cycles. Structure, composition and surface morphology of the Pt/CNF and Pt-Ni/CNF were analyzed using X-ray diffraction, Energy dispersive X-ray spectroscopy and field emission scanning electron microscopy. Structural analysis by XRD revealed a face centered cubic crystal structure for Pt and its alloy. SEM images have shown that the Pt-Ni nanoparticles distributed evenly on the CNF network. The electrocatalytic activity of the Pt/CNF and Pt-Ni/CNF electrodes was verified using an electrochemical linear voltammetrty (ELV), cyclic voltammetry (ECV) and electrochemical impedance spectroscopy (EIS) in an alkaline solution containing 1 M C₂H₅OH + 1 M KOH. The results show increased catalytic activity with enhancement of the Pt-Ni alloy formation.     

La1-xNaxMnO3/YSZ膜的化学溶液法制备及输运性能研究

本文采用化学溶液法在钇稳定的二氧化锆(Y-stabilized ZrO2,YSZ)单晶基板上制备了La1-xNaxMnO3(LNMO)膜并对其输运性能进行了研究.X-射线衍射(XRD)结果表明,所获得的LNMO膜为高度(h00)取向;输运结果表明,所制备的LNMO膜表现为外延膜的性能,且La0.7Na0.3MnO3薄膜在300K、0.5T磁场下可获得～5%磁阻值.     

Plasma electrolytic oxidation coating on AZ91 magnesium alloy modified by neodymium and its corrosion resistance

Ceramic coatings on the surfaces of Mg-9Al-1Zn (AZ91) magnesium alloy and Mg-9Al-1Zn-1Nd magnesium alloy (AZ91 magnesium alloy modified by neodymium, named as AZ91Nd in this paper) are synthesized in aluminate electrolyte by plasma electrolytic oxidation (PEO) process, respectively. X-ray diffraction and X-ray photoelectron spectroscopy analyses show the PEO coating on the Mg-9Al-1Zn-1Nd alloy comprises not only MgO and Al₂O₃, which are found in the coating on the AZ91 alloy, but also a trace amount of Nd₂O₃. Microstructure observations indicate the addition of Nd can decrease the sizes of β phases and form Al₂Nd intermetallics in the AZ91 alloy. The fine β phases can effectively restrain the formation of unclosed-holes and greatly decrease the sizes of pores in the coating during the PEO process. In addition, the Al₂Nd intermetallics can be completely covered due to the lateral growth of the PEO coatings formed on the α and β phases. As a result, the coating on the AZ91Nd alloy possesses a dense microstructure compared with that on the AZ91 alloy. The following corrosion tests indicate the corrosion resistance of the PEO coating on the AZ91Nd alloy is evidently higher than that of the PEO coating on the AZ91 alloy.     

La4/3Ca5/3Mn2O7的结构、电输运及磁性质研究

采用溶胶-凝胶法,在不同温度烧结制备了名义组分为La4/3Ca5/3Mn2O7的多晶样品.X射线结构分析以及电、磁输运性质的测量表明:La4/3Ca5/3Mn2O7形成的是La2/3Ca1/3MnO3和CaO的混合物.     

Structural and electrochemical study on Li(Li1/3Ti5/3)O4 anode material for lithium ion batteries

Chemical and electrochemical studies have shown that various titanium oxides can incorporate lithium in different ratios. Other compounds with a spinel-type structure and corresponding to the spinel oxides LiTi₂O₄ and Li₄Ti₅O₁₂ have been evaluated in rechargeable lithium cells with promising features. The spinel Li[Li_1/3Ti_5/3]O₄ [1–5] compound is a very appealing electrode material for lithium ion batteries. The lithium insertion-deinsertion process occurs with a minimal variation of the cubic unit cell and this assures high stability which may reflect into long cyclability. In addition, the diffusion coefficient of lithium is of the order of 10⁻⁸ cm²s⁻¹ [5] and this suggests fast kinetics which may reflect in high power capabilities. In this work we report a study on the kinetics and the structural properties of the Li[Li_1/3Ti_5/3]O₄ intercalation electrode carried out by: cyclic voltammetry, galvanostatic cycling and in-situ X-ray diffraction. The electrochemical characterization shows that the Li[Li_1/3Ti_5/3]O₄ electrode cycles around 1.56 V vs. Li with a capacity of the order of 130 mAhg⁻¹ which approaches the maximum value of 175 mAhg⁻¹ corresponding to the insertion of 1 equivalent per formula unit. The delivered capacity remains constant for hundred cycles confirming the stability of the host structure upon the repeated Li insertion-deinsertion process. This high structural stability has been confirmed by in situ Energy Dispersion X-ray analysis. Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.     

Electrochemical and microstructural investigations on an as-cast and solution-annealed Al–Mg–Sn–Ga alloy as anode material in sodium chloride solution

In this research, the electrochemical properties of a stir cast Al-0.65Mg-0.15Sn-0.05Ga (wt.%) alloy as an anode material in 3 wt.% NaCl solution was examined by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion behavior of the material was also evaluated using self-corrosion rate, hydrogen evolution, open circuit and closed circuit potentials, and anode efficiency measurements. In addition, the microstructure of the material was studied using scanning electron microscopy (SEM) and the intermetallic particles were analyzed by energy dispersive spectrometer (EDS). The results showed that tin inclusions were formed within the grains and along the grain boundaries and the dissolution of aluminum substrate was occurred preferentially around these particles leading to form round pits. The dissolution of alloy was accompanied by hydrogen gas evolution from cathodic tin particles. Polarization measurements showed active behavior with considerably negative corrosion potential value without any passive region. The obtained impedance results showed an increase in the impedance values due to the coverage of anode surface by reaction products during immersion. A sample of the alloy which was subjected to homogenizing annealing at 570 °C showed more active behavior by providing more negative open and closed circuit potential values and improved anode efficiencies at higher impressed currents, but evolved higher amounts of hydrogen compared to the as-cast anode.

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Graphical abstract This paper aims at evaluating the electrochemical and microstructural characteristics of an as-cast and solution-annealed Al-0.65Mg-0.15Sn-0.05Ga alloy anode which was fabricated by stir casting. The polarization and EIS results indicate negative corrosion potential and OCP values without passive region. The activity and anodic efficiency of the solution-annealed anode was higher in high impressed current densities but evolves more hydrogen

     

XPS, XRD and SEM characterization of a thin ceria layer deposited onto graphite electrode for application in lithium-ion batteries

Thin ceria layer deposited by electro-precipitation onto graphite was synthesised and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electro-precipitated ceria has a cubic structure with nanocrystallites of about 6 nm. The SEM analyses shows that the ceria layer reflects the morphology of the graphite electrode, exhibits small cracks usually found on the electro-precipitated films but covers almost completely the surface of the graphite. The ceria layer is composed of 75% Ce(IV) and 25% Ce(III) oxides as indicated by the XPS analyses. Cyclic voltammetry and galvanostatic charge-discharge tests in ethylene carbonate/dimethyl carbonate (1/1) (wt/wt) in the presence of 1 M LiPF₆ show that reversible lithium insertion and deinsertion occurs in the graphite/ceria electrode and that the ceria layer on the graphite electrode prevents from the loss of capacity during the first four cycles. The reduction of the electrolyte occurs at about 0.7 V vs Li/Li⁺ on both electrodes but XPS and SEM analyses show that the SEI layer is thin and not as homogenous on the graphite as on the graphite/ceria electrode. The composition of the SEI layer on the graphite/ceria electrode, mainly composed of Li₂CO₃, ROCO₂Li, R-CH₂OLi and LiF, is different than those obtained on the graphite.     

固态电解质锂镧锆氧(Li_7La_3Zr_2O_(12))制备及第一性原理研究

固态电解质(SSE)是锂离子电池(LIB)的关键材料.Li_7La_3Zr_2O_(12)(LLZO)固体电解质是全固态锂离子电池开发中的关键部分.采用高温固相法制备了不同烧结温度后的四方Li_7La_3Zr_2O_(12)(t-LLZO)和立方Li_7La_3Zr_2O_(12)(c-LLZO),分析了两种样品的结构性能.800℃下烧结12小时的t-LLZO呈四方相,晶格尺寸为a=b=13.13064?,c=12.66024?,离子电导率为3.42×10~(-8)S·cm~(-1);1000℃下烧结12小时的c-LLZO呈立方相,晶格尺寸为a=b=c=13.03544?,离子电导率为8.48×10~(-5)S·cm~(-1).另基于密度泛函理论(DFT)的第一性原理计算了四方相和立方相的LLZO固体电解质材料的能带结构、晶格参数、态密度和键布居.通过理论计算解释了四方相LLZO离子电导率低于立方相LLZO的原因.     

Surface modification of Al-12.6Si alloy by high current pulsed electron beam

The paper investigates the microstructure and property modifications of Al-12.6Si alloy induced by high current pulsed electron beam (HCPEB) treatment. The scanning electron microscope (SEM) results show a fine and equiaxed grain structure of several micrometers is obtained on the top surface of the melted layer. Underneath the top surface, a remelted layer with about 10 μm thickness is obtained and a supersaturated solid solution of Al is formed in the remelted layer. XRD analysis shows that the relative strength of diffraction peaks of Al (1 1 1) and Si (1 1 1) crystal planes is increased after HCPEB treatment. As a result, relative wear resistance of HCPEB-treated sample is significantly improved by a factor of 2.5 due to fine grain strengthening and solid solution strengthening. Therefore, the HCPEB treatment has a good application future in treating Al-Si alloys.