Electrode-induced nonuniformities in the sweeping of alpha quartz

Infrared absorption and scanning electron microscopic techniques show that color-center and/or electrode-metal introduction into quartz is influenced by the porosity of evaporated metal electrodes. Thermal-stress relief of electrode-metal films, during sweeping, normally causes porosity. If the porosity is extensive, H introduction predominates and color-center and electrode-metal introduction mechanisms are suppressed. Samples swept with evaporated Au/Cr electrodes relying on thermal stress-induced porosity sometimes displayed these sweeping nonuniformities. Nonuniformities were not found when samples were swept using evaporated Au-Cr electrodes containing periodic stripe openings. Uniform sweeping was also obtained using magnetron-sputtered amorphous Y-Ba-Cu-O films.     

Electrolytic recovery of chromium salts from tannery wastewater

Tannery wastewater collected from a local leather industry in Peshawar, Pakistan was subjected to DC electrolysis in a simple cell having two static sheet electrodes and stirring assembly after proper dilution and adjustment to desired conditions. One percent HNO(3) and 1% NaHCO(3) were used as electrolytes and pH adjusters. The latter salt also worked as sodium source for anodic deposition of Na(2)Cr(2)O(7). Various combinations of electrodes were tested and conditions optimized for best electrode couple with increased recovery and removal of chromium in the form of Cr(OH)(3) and/or Na(2)Cr(2)O(7) at cathode and anode, respectively. The recovery of 99% chromium was achieved after 2h electrolysis at a cell potential of 1.0 V, pH 5.0 and stirring rate of 500 rpm using Pb sheet as anode and Cu sheet as cathode. The most interesting and novel finding of this work was the recovery of the mentioned salt(s) alone at Cu cathode or Pb anode or collectively at both electrodes by proper control of pH. Such treatment not only minimizes the environmental water pollution, but results in the formation of useful products employed for recycling purpose in tannery or other related industry to make the process economical.     

Effect of cerium addition to Ni–Cr anode electrode for molten carbonate fuel cells: Surface fractal dimensions,wettability and cell performance

The geometrical and chemical effects of cerium (Ce) addition to Ni–Cr anode electrode in molten carbonate fuel cells (MCFCs) were investigated by measuring the fractal dimensions and wettability of four types of anode electrode with Ce added up to 5 wt.%. In addition, their cell performances were investigated through a single cell operation test and their results were explained based on the wettability of the anode electrodes. The addition of Ce to the anode electrode increased the fractal dimensions and wettabilities of the electrodes. Despite the even larger electrical resistivity of Ce compared to that of Ni and Cr, the electrical resistances of the Ce-added anode electrodes were slightly increased with increasing level of Ce addition. This might be ascribed to the greater wettability of the Ce-added anode electrode that enhanced the cell performance. Therefore, the greater wettability of the Ce-added anode electrode might compensate for its relatively larger electrical resistance. Considering these results, more stable cell operation with a longer potential lifespan was achieved with the Ce (3 wt.%)-added, Ni (90 wt.%)–Cr (7 wt.%) anode electrode, compared to those of the Ce-free Ni–Cr anode electrode.     

Morphology of ultra fine iron particles

Variation in morphology of the silica thin film coated ultra fine goethite particles(length:140 nm, aspect ratio:11/1, surface area:95 m²/g, SiO2/Fe:3.4 wt%) in the process of decomposition and subsequent reduction was examined by means of gas adsorption and electron microscopy. Microporous hematite particles, prepared by decomposition of the silica-coated ultra fine goethite particles at 250°C in vacuo, were subjected to heat-treatment at 700°C in air to form the nonporous hematite particles without degradation of the acicular shape. The highly acicular and nonporous ultra fine iron particles(length:110 nm, aspect ratio:10/1, surface area: 80 m²/g) were obtained as a result of shrinkage of the particles in the reduction process of the nonporous hematite particles at 400°C in hydrogen gas. Coercivity of the ultra fine iron particles was 1660 Oe.     

Decolorization of dye solution containing Acid Red 14 by electrocoagulation with a comparative investigation of different electrode connections

This study was performed to investigate the variables that influence the efficiency of decolorization of a solution containing an azo dye (Acid Red 14) by electrocoagulation (EC) in order to compare the efficiency of different electrode connections for color removal. Current density, time of electrolysis, interelectrode distance, and pH of the solution were the variables that most influenced color removal. Initially, a simple electrochemical cell was prepared with an anode and a cathode. Then the effect of each variable was studied separately using synthetic wastewater in a batch mode. The efficiency of the method tested was determined by measurement of color removal and reduction of Chemical Oxygen Demand (COD). For dye solutions with COD of approximately 30 ppm and dye concentrations less than 150 ppm, high color removal (93%) was obtained when the pH ranged from 6 to 9, time of electrolysis was approximately 4 min, current density was approximately 80 A/m2, the temperature was approximately 300 K, and interelectrode distance was 1 cm. During the EC process under these conditions, the COD decreased by more than 85%. In the second series of experiment, the efficiency of EC cells with monopolar electrodes in series and parallel connections and an EC cell with bipolar electrodes were compared with results using a simple electrochemical cell. The experimental results showed that an EC cell with several electrodes was more effective than a simple electrochemical cell in color removal. The results also showed that an EC cell with monopolar electrodes had a higher color removal efficiency than an EC cell with bipolar electrodes. Furthermore, within an EC cell, the series connection of the monopolar electrodes was more effective for the treatment process than the parallel connection in color removal.     

Synthesis and electrochemical performances of LiNiCuZn oxides as anode and cathode catalyst for low temperature solid oxide fuel cell

Low temperature solid oxide fuel cell (LTSOFC, 300-600 degrees C) is developed with advantages compared to conventional SOFC (800-1000 degrees C). The electrodes with good catalytic activity, high electronic and ionic conductivity are required to achieve high power output. In this work, a LiNiCuZn oxides as anode and cathode catalyst is prepared by slurry method. The structure and morphology of the prepared LiNiCuZn oxides are characterized by X-ray diffraction and field emission scanning electron microscopy. The LiNiCuZn oxides prepared by slurry method are nano Li0.28Ni0.72O, ZnO and CuO compound. The nano-crystallites are congregated to form ball-shape particles with diameter of 800-1000 nm. The LiNiCuZn oxides electrodes exhibits high ion conductivity and low polarization resistance to hydrogen oxidation reaction and oxygen reduction reaction at low temperature. The LTSOFC using the LiNiCuZn oxides electrodes demonstrates good cell performance of 1000 mW cm(-2) when it operates at 470 degrees C. It is considered that nano-composite would be an effective way to develop catalyst for LTSOFC.     

大电流真空电弧阳极熔蚀过程的热力学仿真研究

真空介质开关电弧的主要成分源于故障电流开断过程中触头电极在极间产生的金属蒸气,且真空电弧的微观动力学行为直接影响开关的开断能力。文章通过建立真空介质电弧双温磁流体动力学模型,研究配用不同配比CuCr合金触头电极材料的真空介质开关在故障电流开断下阳极热过程的变化情况,得到阳极触头表面温度和熔池范围沿径向和轴向的分布。仿真结果表明,开断故障电流的增大及电极合金材料中Cu含量的增大均会导致输入阳极的能流密度增大。在200 A电弧电流作用下,阳极表面温度未达到CuCr合金的熔点,未发生熔化;而在6 kA电弧电流作用下,阳极温度先后达到Cu和Cr的熔点,电极熔化程度随合金中Cr含量的增大而减弱。

     

Improvement in the Adhesion Between Electrode of a SOFC and Ag Paste as a Current Collector by Au Deposition

This paper reports the use of Au films to improve the performance of the stacked solid oxide fuel cell(SOFC) based on the characterization of the interface and the adhesion between the electrodes of the SOFCs and the Ag paste. The specimens were manufactured to perform the experiment as follows. A Si O2 wafer with a 300 mm notch was attached to the electrodes of a SOFC by a Ag paste and Au film, which were deposited on the electrodes by sputtering for 1 min or 5 min deposition time and annealed at300 C for 1 h. The four-point bending test was performed, which resulted in the formation of an extended crack at the tip on the wafer notch, and the crack propagation was observed using a stereo microscope equipped with a charge-coupled device(CCD). Consequently, the interfacial adhesion energy and the effect of the Au film between the each electrode and the Ag paste can be evaluated. On the cathode, the interfacial adhesion energy without Au film was 2.59 J/m2(upper value) and the adhesion energy increased to 11.59 J/m2(upper value) and 15.89 J/m2(lower value) with the Au film. On the anode,the interfacial adhesion energy without Au film was 1.74 J/m2(upper value), which increased to 11.07 J/m2(upper value) and 14.74 J/m2(lower value) with the Au film. In addition, the interface areas were analyzed by scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS) to estimate the interface delamination.     

Yolk–Shell Fe/Fe4N@Pd/C Magnetic Nanocomposite as an Efficient Recyclable ORR Electrocatalyst and SERS Substrate

A yolk–shell Fe/Fe₄N@Pd/C (FFPC) nanocomposite is synthesized successfully by two facile steps: interfacial polymerization and annealing treatment. The concentration of Pd²⁺ is the key factor for the density of Pd nanoparticles (Pd NPs) embedded in the carbon shells, which plays a role in the oxygen reduction reaction (ORR) and surface‐enhanced Raman scattering (SERS) properties. The ORR and SERS performances of FFPC nanocomposites under different concentrations of PdCl₂ are investigated. The optimal ORR performance exhibits that onset potential and tafel slope can reach 0.937 V (vs reversible hydrogen electrode (RHE)) and 74 mV dec^?1, respectively, which is attributed to the synergistic effects of good electrical conductivity, large electrochemically active areas, and strong interfacial charge polarization. Off‐axis electron holography reveals that interfacial charge polarization could facilitate the ORR of Pd NPs and defective carbon simultaneously and the shell with low density of Pd NPs is easier to form strong interfacial charge polarization. Moreover, FFPC‐3 with maximum EF of 2.3 × 10⁵ results from more hot‐spots, local positive charge centers to attract rhodamine 6G molecules, and magnetic cores. This work not only offers a recyclable multifunctional nanocomposite with excellent performance, but also has instructional implications for interfacial engineering for electrocatalysts design.     

Electrochemical removal of chromium from aqueous solutions using electrodes of stainless steel nets coated with single wall carbon nanotubes

An electrochemical technique was adopted to investigate the removal of Cr(VI) species and total chromium (TCr) from aqueous solution at a laboratory scale. The electrodes of stainless steel nets (SSNE) coated with single wall carbon nanotubes (SWCNTs@SSNE) were used as both anode and cathode. Three parameters, including solution pH, voltage and electrolyte concentration, were studied to explore the optimal condition of chromium removal. The optimal parameters were found to be pH 4, voltage 2.5 V and electrolyte concentration 10 mg/L. Under these conditions, the Cr(VI) and TCr removal had a high correlation with the amount of SWCNTs coated on the electrodes, with coefficients of the regression equations 0.953 and 0.928, respectively. The mechanism of Cr(VI) removal was also investigated. X-ray photoelectron spectroscopy (XPS) study and scanning electron microscope (SEM) picture showed that the process of chromium removal involved the reduction of Cr(VI) to Cr(III) on the cathode, and then the adsorption of Cr(III) by SWCNTs on the cathode. The study results indicated that the proposed method provided an interesting means to remove chromium species from aqueous solution, especially Cr(VI) in acidic condition.     

Thin Film Composite Membranes as a New Category of Alkaline Water Electrolysis Membranes

Alkaline water electrolysis (AWE) is considered a promising technology for green hydrogen (H₂) production. Conventional diaphragm-type porous membranes have a high risk of explosion owing to their high gas crossover, while nonporous anion exchange membranes lack mechanical and thermochemical stability, limiting their practical application. Herein, a thin film composite (TFC) membrane is proposed as a new category of AWE membranes. The TFC membrane consists of an ultrathin quaternary ammonium (QA) selective layer formed via Menshutkin reaction-based interfacial polymerization on a porous polyethylene (PE) support. The dense, alkaline-stable, and highly anion-conductive QA layer prevents gas crossover while promoting anion transport. The PE support reinforces the mechanical and thermochemical properties, while its highly porous and thin structure reduces mass transport resistance across the TFC membrane. Consequently, the TFC membrane exhibits unprecedentedly high AWE performance (1.16 A cm⁻² at 1.8 V) using nonprecious group metal electrodes with a potassium hydroxide (25 wt%) aqueous solution at 80 °C, significantly outperforming commercial and other lab-made AWE membranes. Moreover, the TFC membrane demonstrates remarkably low gas crossover, long-term stability, and stack cell operability, thereby ensuring its commercial viability for green H₂ production. This strategy provides an advanced material platform for energy and environmental applications.     

Interfacial properties and structure stability of Ni/Y2 O3-ZrO2-TiO2 cermet anodes for solid oxide fuel cells

Ceramics of the ternary system Y₂O₃-ZrO₂-TiO₂ (YZT) and Ni/YZT cermets are evaluated in terms of application as anode electrodes in a Solid Oxide Fuel Cell. Wetting experiments in liquid Ni/YZT systems show that the increase of TiO₂ content in the ceramic phase improves the bond strength at the metal ceramic interface, due to the reduction of the interfacial energy. Ni(40 vol%)/YZT cermets are exposed at 1000°C for up to 1000 h in reducing atmosphere and exhibit an improved long term stability regarding to the electrical conductivity and the microstructure compared to the “state of the art” Ni/8YSZ (yttria(8 mol%)-stabilized zirconia) cermet. This is explained by the enhanced adherence at the Ni/ceramic interface, which suppresses the agglomeration rate of the Ni particles. The improvement of the interfacial properties diminishes the TEC values of the Ni/YZT cermets constraining the thermal expansion mismatch between the cermet anode and the 8YSZ electrolyte in the SOFCs.     

Fluorinated Interface Engineering toward Controllable Zinc Deposition and Rapid Cation Migration of Aqueous Zn-Ion Batteries

Metallic zinc (Zn) is a highly promising anode material for aqueous energy storage systems due to its low redox potential, high theoretical capacity, and low cost. However, rampant dendrites/by-products and torpid Zn²⁺ transfer kinetics at electrode/electrolyte interface severely threaten the cycling stability, which deteriorate the electrochemical performance of Zn-ion batteries. Herein, an interfacial engineering strategy to construct alkaline earth fluoride modified metal Zn electrodes with long lifespan and high capacity retention is reported. The compact fluoride layer is revealed to guide uniform Zn stripping/plating and accelerate the transfer/diffusion of Zn²⁺ via Maxwell-Wagner polarization. A series of in situ and ex situ spectroscopic studies verified that the fluoride layer can guide uniform Zn stripping/plating. Electrochemical kinetics analyses reveal that positive effect on the removal of Zn²⁺ solvation sheath provided by fluoride layer. Meanwhile, this fluoride coating layer can act as a barrier between the Zn electrode and electrolyte, providing a high electrode overpotential toward hydrogen evolution reaction to hold back H₂ evolution. Consequently, the fluoride-modified Zn anode exhibited a capacity retention of 88.2% after 4000 cycles under10 A g⁻¹. This work opens up a new path to interface engineering for propelling the exploration of advanced rechargeable aqueous Zn-ion batteries.     

合金化与Ti基储氢合金容量及活化性能关联

针对Ti-Zr基多元多相储氢电极合金,实验研究了Ni、Cr、V替代Mn对Ti基AB2型储氢合金容量和活化性能的影响.研究表明:在合金中增加Ni含量能够提高放电容量,但Ti-Ni相的过剩会降低合金容量;Ni的高活性和导电性加速氢扩散和电荷转移,改善合金活化性能;随Cr含量增加,合金容量先增后减,而活化性能先恶化后改善;V取代Mn提高合金容量,但当V超过一定计量后,将导致合金容量降低;V的高导电性改善合金电极的活化性能.     

Interfacial scattering at electrochemically fabricated atom-scale junctions between thin gold film electrodes in a microfluidic channel

Atom-scale junctions were formed between two Au thin-film electrodes by a combination of lithography, microfluidics, and electrochemistry. Two Au thin-film electrodes with a small (0.25-25 microm) gap between them were lithographically defined such that the gap fell in the center of a 100-microm-wide microfluidic channel in poly(dimethylsiloxane). Directional electrodeposition between the Au thin-film electrodes, accomplished by applying a potential between the thin-film electrodes, caused Au to etch from the anode and deposit on the cathode, thereby closing the gap. Current through the gap was monitored continuously, and the directional electrodeposition was terminated when a current near that corresponding to the conductance quantum, G(0) = 2e(2)/h, was reached. To regenerate the device, the atom-scale junction was broken with a potential sweep, the microfluidic channel was rinsed, and the junction was re-formed with a subsequent comparator-terminated directional electrodeposition. Alternating current impedance was measured while hexadecanethiol (HDT) was chemisorbed onto the atom-scale junction. The interfacial scattering from chemisorption of the Lewis base HDT on the atom-scale junction caused a normalized impedance change of 71 +/- 1%, the noise level being equivalent to a population fluctuation of five HDT molecules.     

Overcoming the Interfacial Limitations Imposed by the Solid–Solid Interface in Solid‐State Batteries Using Ionic Liquid‐Based Interlayers

Li‐garnets are promising inorganic ceramic solid electrolytes for lithium metal batteries, showing good electrochemical stability with Li anode. However, their brittle and stiff nature restricts their intimate contact with both the electrodes, hence presenting high interfacial resistance to the ionic mobility. To address this issue, a strategy employing ionic liquid electrolyte (ILE) thin interlayers at the electrodes/electrolyte interfaces is adopted, which helps overcome the barrier for ion transport. The chemically stable ILE improves the electrodes‐solid electrolyte contact, significantly reducing the interfacial resistance at both the positive and negative electrodes interfaces. This results in the more homogeneous deposition of metallic lithium at the negative electrode, suppressing the dendrite growth across the solid electrolyte even at high current densities of 0.3 mA cm^?2. Further, the improved interface Li/electrolyte interface results in decreasing the overpotential of symmetric Li/Li cells from 1.35 to 0.35 V. The ILE modified Li/LLZO/LFP cells stacked either in monopolar or bipolar configurations show excellent electrochemical performance. In particular, the bipolar cell operates at a high voltage (≈8 V) and delivers specific capacity as high as 145 mAh g^?1 with a coulombic efficiency greater than 99%.     

Tuning the Anode–Electrolyte Interface Chemistry for Garnet-Based Solid-State Li Metal Batteries

Lithium (Li) metal is a promising candidate as the anode for high-energy-density solid-state batteries. However, interface issues, including large interfacial resistance and the generation of Li dendrites, have always frustrated the attempt to commercialize solid-state Li metal batteries (SSLBs). Here, it is reported that infusing garnet-type solid electrolytes (GSEs) with the air-stable electrolyte Li₃PO₄ (LPO) dramatically reduces the interfacial resistance to ≈1 Ω cm² and achieves a high critical current density of 2.2 mA cm⁻² under ambient conditions due to the enhanced interfacial stability to the Li metal anode. The coated and infused LPO electrolytes not only improve the mechanical strength and Li-ion conductivity of the grain boundaries, but also form a stable Li-ion conductive but electron-insulating LPO-derived solid-electrolyte interphase between the Li metal and the GSE. Consequently, the growth of Li dendrites is eliminated and the direct reduction of the GSE by Li metal over a long cycle life is prevented. This interface engineering approach together with grain-boundary modification on GSEs represents a promising strategy to revolutionize the anode–electrolyte interface chemistry for SSLBs and provides a new design strategy for other types of solid-state batteries.     

Monolithic Graphene Trees as Anode Material for Lithium Ion Batteries with High C‐Rates

Monolithically structured reduced graphene oxide (rGO), prepared from a highly concentrated and conductive rGO paste, is introduced as an anode material for lithium ion batteries with high rate capacities. This is achieved by a mixture of rGO paste and the water‐soluble polymer sodium carboxymethylcellulose (SCMC) with freeze drying. Unlike previous 3D graphene porous structures, the monolithic graphene resembles densely branched pine trees and has high mechanical stability with strong adhesion to the metal electrodes. The structures contain numerous large surface area open pores that facilitate lithium ion diffusion, while the strong hydrogen bonding between the graphene layers and SCMC provides high conductivity and reduces the volume changes that occur during cycling. Ultrafast charge/discharge rates are obtained with outstanding cycling stability and the capacities are higher than those reported for other anode materials. The fabrication process is simple and straightforward to adjust and is therefore suitable for mass production of anode electrodes for commercial applications.     

Assessment of electrokinetic removal of heavy metals from soils by sequential extraction analysis

Electrokinetic remediation of metal-contaminated soils is strongly affected by soil-type and chemical species of contaminants. This paper investigates the speciation and extent of migration of heavy metals in soils during electrokinetic remediation. Laboratory electrokinetic experiments were conducted using two diverse soils, kaolin and glacial till, contaminated with chromium as either Cr(III) or Cr(VI). Initial total chromium concentrations were maintained at 1000mg/kg. In addition, Ni(II) and Cd(II) were used in concentrations of 500 and 250mg/kg, respectively. The contaminated soils were subjected to a voltage gradient of 1 VDC/cm for over 200h. The extent of migration of contaminants after the electric potential application was determined. Sequential extractions were performed on the contaminated soils before and after electrokinetic treatment to provide an understanding of the distribution of the contaminants in the soils. The initial speciation of contaminants was found to depend on the soil composition as well as the type and amounts of different contaminants present. When the initial form of chromium was Cr(III), exchangeable and soluble fractions of Cr, Ni, and Cd ranged from 10 to 65% in kaolin; however, these fractions ranged from 0 to 4% in glacial till. When the initial form of chromium was Cr(VI), the exchangeable and soluble fractions of Cr, Ni and Cd ranged from 66 to 80% in kaolin. In glacial till, however, the exchangeable and soluble fraction for Cr was 38% and Ni and Cd fractions were 2 and 10%, respectively. The remainder of the contaminants existed as the complex and precipitate fractions. During electrokinetic remediation, Cr(VI) migrated towards the anode, whereas Cr(III), Ni(II) and Cd(II) migrated towards the cathode. The speciation of contaminants after electrokinetic treatment showed that significant change in exchangeable and soluble fractions occurred. In kaolin, exchangeable and soluble Cr(III), Ni(II), and Cd(II) decreased near the anode and increased near the cathode, whereas exchangeable and soluble Cr(VI) decreased near the cathode and increased near the anode. In glacial till, exchangeable and soluble Cr(III), Ni(II), and Cd(II) were low even before electrokinetic treatment and no significant changes were observed after the electrokinetic treatment. However, significant exchangeable and soluble Cr(VI) that was present in glacial till prior to electrokinetic treatment decreased to non-detectable levels near the cathode and increased significantly near the anode. In both kaolin and glacial till, low migration rates occurred as a result of contaminants existing as immobile complexes and precipitates. The overall contaminant removal efficiency was very low (less than 20%) in all tests.     

Interfacial evolution in Sn–58Bi solder joints during liquid electromigration

For Sn–58Bi low temperature solder alloy, local molten induced from electromigration Joule heating might change the atomic diffusion and interfacial behavior. In this paper, the diffusion behavior and interfacial evolution of Cu/Sn–58Bi/Cu joints were studied under liquid–solid (L–S) electromigration in molten solder and were compared with the interfacial behaviors in solid–solid (S–S) electromigration in solid solder. L–S or S–S electromigration was realized by applying a current density of 1.0?×?10⁴ A/cm² to molten solder at 150 °C or solid solder at 25 °C, respectively. During S–S electromigration, Bi atoms were driven towards anode side under electromigration induced flux and then accumulated to form Bi-rich layer near anode interface with current stressing time increasing. During L–S electromigration, Bi atoms were reversely migrated from anode to cathode to produce Bi segregation at cathode interface, while Cu atoms were rapidly dissolved into molten solder from cathode and migrated to form large amounts of Cu₆Sn₅ rod-like phases near anode interface. The reversal in the direction of Bi atoms may be attributed to the reversal in the direction of electromigration induced flux and correspondingly the change on effective charge number of Bi atoms from negative to positive.