Cathode Substrate Research Articles

Titanium Production from Oxycarbide Anodes

The aim of this work is to investigate the new possibilities for electrochemical titanium production as a way of reducing the production costs of the primary metal. The oxycarbide process is a process which involves electrodeposition of Ti at a cathode substrate, and using anodes of a TiC-TiO solid solution made from TiO2 and C. It looks promising, with cheap raw materials, and with a simpler production route than today's process.

Granular nanocrystalline zirconia electrolyte layers deposited on porous SOFC cathode substrates

Thin granular yttria-stabilized zirconia (YSZ) electrolyte layers were prepared by chemical vapor synthesis and deposition (CVD/CVS) on a porous substoichiometric lanthanum–strontium–manganite (ULSM) solid oxide fuel cell cathode substrate. The substrate porosity was optimized with a screen printed fine porous buffer layer. Structural analysis by scanning electron microscopy showed a homogeneous, granular nanocrystalline layer with a microstructure that was controlled via reactor settings. The CVD/CVS gas-phase process enabled the deposition of crack-free granular YSZ films on porous ULSM substrates. The electrolyte layers characterized with impedance spectroscopy exhibited enhanced grain boundary conductivity.

Surface Modification of SiC Powder for Use in Electrophoretic Deposition

The surface modification of SiC powder with an alumina precursor was achieved by a sol-gel method to apply the electrophoretic deposition (EPD) technique to the shaping of the SiC powder. The isoelectric point of the surface-modified SiC powder with sol-gel-derived alumina precursor was shifted to around pH 9, which is close to that of alumina. The alumina-coated SiC deposited on a cathodic substrate by EPD. The green compact of surface-modified SiC powder was sintered by hot pressing in an argon atmosphere at 2000oC.

THE MANUFACTURE OF PERCHLORATE BY DIRECT METHOD USING GRAPHITE SUBSTRATE LEAD DIOXIDE (GSLD) ANODE

Sodium perchlorate has been prepared electrochemically from sodium chloride solutions in one step by passing a direct current through the solution , in the presence of certain addition agents (like sodium fluoride). A laboratory electrolytic cell has been designed to obtain experimental results for the preparation of sodium perchlorate. A solution of sodium chloride (290 g/l ) and sodium fluoride (2 g/l ) is electrolyzed in a batch wise. A stainless steel cathode and Graphite substrate lead dioxide (GSLD) anode are satisfactory . The influence of anodic current density , temperature ,and pH of electrolyte on current efficiency of sodium perchlorate formation were studied. The current efficiency of about 68% was obtained by using (GSLD) anode

Effect of natural and magnetic convections on the structure of electrodeposited zinc–nickel alloy

The effects of a magnetic field applied in a direction parallel or perpendicular to the cathode substrate plane, during electrodeposition process of Zn–Ni alloy have been investigated by means of chronoamperometric measurements, X-ray diffraction and EDX analysis. The modification of crystal orientation of the alloy by the superimposition of a high magnetic field is discussed for alloys with a content of nickel range 6–13 at%. Whatever the phase composition obtained without magnetic field, either γ-Ni 5Zn 21 or a mixture of the γ and zinc phases, which depends on the concentration of Ni 2+ in the electrolyte bath, the preferential orientation (1 0 1) of the zinc phase is always favoured with perpendicular and parallel magnetic field. There is no saturation of this effect with amplitude of B up to 8 T. A study of different geometric configurations of the cathode, which induce more or less natural convection, consolidates these results. The structural modifications of Zn–Ni alloy electrodeposits are thus probably due to a magnetohydrodynamic effect. An additional phenomenon is observed in presence of a perpendicular applied magnetic field since the (3 3 0) preferential orientation of the γ-Ni 5Zn 21 disappears with high values of B.

Mesoporous Hydrous Manganese Dioxide Nanowall Arrays with Large Lithium Ion Energy Storage Capacities

AbstractNovel nanowall arrays of hydrous manganese dioxide MnO2 · 0.5H2O are deposited onto cathodic substrates by the potentiostatic method from a mixed aqueous solution of manganese acetate and sodium sulfate. The deposition is induced by a change of local pH resulting from electrolysis of H2O, and hierarchical mesoporous nanowall arrays are formed as a result of simultaneous precipitation of manganese hydroxide and release of hydrogen gas bubbles from the cathode. The morphology and lithium ion intercalation properties are found to change appreciably with the concentration of the precursor electrolyte, with a significant reduction in specific surface area with an increased precursor concentration. For example, mesoporous nanowall arrays deposited from 0.1 M solution possess a surface area of ∼96 m2 g−1 and exhibit a stable high intercalation capacity of 256 mA hg−1 with a film of 0.5 µm in thickness, far exceeding the theoretical limit of 150 mA hg−1 for manganese dioxide bulk film. Such mesoporous nanowall arrays offer much greater energy storage capacity (e.g., ∼230 mA hg−1 for films of ∼2.5 µm) than that of anodic deposited films of the same thickness (∼80 mA hg−1). Such high lithium ion intercalation capacity and excellent cyclic stability of the mesoporous nanowall arrays, especially for thicker films, are ascribed to the hierarchically structured macro‐ and mesoporosity of the MnO2 · 0.5H2O nanowall arrays, which offer large surface to volume ratio favoring interface Faradaic reactions, short solid‐state diffusion paths, and freedom to permit volume change during lithium ion intercalation and de‐intercalation.

Cathode-supported micro-tubular SOFCs based on Nd 1.95NiO 4 + δ: Fabrication and characterisation of dip-coated electrolyte layers

Fabrication conditions to obtain dense electrolyte double layers on a porous micro-tubular cathode substrate were investigated. Porous tubes of a nickelate material, Nd 1.95NiO 4 + δ , were fabricated by cold-isostatic pressing (CIP) and sintering. Thin films of electrolyte powders Ce 0.9Gd 0.1O 1.95 (GDC) and Zr 0.89Sc 0.1Ce 0.01O 1.95 (SSZ) were applied by dip-coating in aqueous suspensions. Electrolyte powders had been attrition-milled to decrease their particle size and densification temperature. The quantity of polyacrylic acid (PAA) as dispersant was optimised by ζ-potential measurements. The densification behaviour was studied by dilatometry and SEM-imaging. A sintering temperature of 1250 °C was found to densify GDC whereas SSZ-layers remained slightly porous.

Electromigration Test on Void Formation and Failure Mechanism of FCBGA Lead-Free Solder Joints

The effect of electromigration (EM) on void formation and the failure mechanism of flip chip ball grid array (FCBGA) packages under a current density of 1 -10 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and an environmental temperature of 150degC was investigated. Eight solder/substrate combinations of four lead-free solder systems with two substrates were examined to verify the failure modes. A conservative failure criterion was adopted to define and predict the failure of the package, scanning electron microscope (SEM) was employed to observe in situ microstructural changes, intermetallic compound (IMC) growth, and failure modes. All samples exhibited a similar failure, attributed mainly to void occupation along under bump metallization (UBM)/solder interfaces at the cathode chip side of the bumps with downward electron flow. Voids were initiated at the corner due to current crowding. Two specific void locations were identified at the IMC/solder and UBM/IMC interfaces, and they coexisted in the same specimen but in different bumps. No void coupling mode was found. Since the atom diffusion rate in the solder differs from that in the IMC layer, the voids can be formed between them. A current density of 1-104 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> was sufficiently high to form a void pattern at the IMC/solder interface. However, the formation of voids at the UBM/IMC interface is generally induced by the consumption of UBM, since the high temperature of 150degC crucially dominates the void morphology at the UBM/IMC interface. The difference among solder systems did not affect the failure modes nor dominate mechanisms. With respect to the differences of substrate surface finishes, more voids appeared at the cathode substrate side of the solders combined with Cu/Ni/Au pad than those combined with copper-organic solderable preservative (Cu-OSP) after long-term upward electron stressing. It suggested another possible failure at the substrate side when failure did not occur at the chip side in an EM test.

Fabrication of a large area cathode-supported thin electrolyte film for solid oxide fuel cells via tape casting and co-sintering techniques

A large area cathode-supported electrolyte film, comprising porous (La 0.8Sr 0.2) 0.95MnO 3 (LSM95) cathode substrate, LSM95/Zr 0.89Sc 0.1Ce 0.01O 2− x (SSZ) cathode active layer, and SSZ electrolyte, has been successfully fabricated by tape casting and co-sintering techniques. The interface reaction between cathode and electrolyte was inhibited by using A-site deficient LSM. A dense enough SSZ thin film with a thickness of ∼26 μm was obtained at 1250 °C. By using Pt as anode, the obtained single cell reached the maximum power density of 0.54 W cm −2 at 800 °C in O 2/humidified H 2, with open circuit voltage (OCV) value of 1.08 V.

Pyrococcus furiosus-immobilized anodized tubular titania cathode in a hydrogen production system

Anodized tubular titania (TiO 2) electrodes (ATTEs) are prepared and used as both the photoanode and the cathode substrate in a photoelectrochemical system designed to split water into hydrogen with the assistance of an enzyme and an external bias of 1.5 V. In particular, the ATTE used as the cathode substrate for the immobilization of the enzyme is prepared by two methods—adsorption and crosslinking. Results show that the optimized amount of enzyme is 10.98 units for the slurried enzyme, 3.66 units for the adsorbed one and 7.32 units for the crosslinked one, and the corresponding hydrogen evolution rates are 33.04, 148.58 and 234.88 μmol h −1, respectively. The immobilized enzyme, specifically the chemically crosslinked one, seems to be much superior to the slurried enzyme, due to the enhanced charge-transfer process that is caused by the lower electrical resistance between the enzyme and the ATTE. This results in a greater number of accepted electrons and a larger amount of enzymes able to deal with the electrons.

Electrowinning of Iron in Aqueous Alkaline Solution Using a Rotating Cathode

Electrowinning of iron by electrodecomposition of iron oxide ore in aqueous alkaline electrolytes is an alternative method to reduce emissions in steelmaking. Laboratory experiments were carried out in a suspension of hematite in concentrated NaOH at . particles were reduced to metallic iron upon contact with the rotating cathode, while oxygen gas was evolved on the nickel mesh anode. Iron deposits generally adhered well to the carbon cathode substrate. The current efficiency for iron was consistently above 90%, hydrogen evolution on the cathode being the main reason for the inefficiency. The influence of cathode rotation rate, cathodic current density, content of particles, and concentration of NaOH on the current efficiency and the morphology of the deposit was studied.

A DOE nano-tribological study of thin amorphous carbon-based films

A design of experiment (DOE) matrix of 150 nm non-hydrogenated amorphous C and Cr doped amorphous C films was produced to investigate the effect of four key coating process parameters (use of an adhesion layer, Cr magnetron current, cathodic substrate bias voltage and Ar flow to the chamber) using a new rapid method of nano-scale wear test under conditions relevant to MEMS and similar devices. The condition of nano-wear was produced by controlled oscillation of the sample mounting within a nanoindentation system under ultra-low normal load. Specific wear rates were low, typically in the range 6–24×10 −17 m 3 N −1 m −1. The results were processed using an analysis of variance (ANOVA) procedure which showed that: hardness was reduced in the Cr containing films whilst specific wear rate and data scatter increased, increasing the cathodic substrate bias voltage reduced the specific wear rate due to increased coating hardness, the use of a Cr adhesion layer reduced the specific wear rate and scatter of results with Cr doped films but had no effect on pure a-C films, and Ar flow rate had no significant effect on specific wear rate but strongly interacted with the effect of the cathodic bias voltage.

Field emission from strained carbon nanotubes on cathode substrate

Experimental studies on the collective field emission from carbon nanotubes (CNTs) on metallic cathode substrate show wide variability. In this paper, we investigate several related effects, such as the relationship between the electron–phonon transport and the mechanical deformation in the CNTs. A systematically coupled model of randomly oriented CNTs in a thin film is developed. Numerical simulations are reported, which are able to reproduce several experimentally observed phenomena, such as a fluctuating field emission current, deflected CNT tips and the heating process. Examples are shown, where the electrodynamic stretching of the initially deflected CNTs can produce transients in the collective field emission current as large as 1 0 3 times the usual field emission current. Correspondingly, the tip temperature rises from 303 to 520 K within a time interval of 40 s. A 10 K variability in the maximum temperature is observed over the 0.0144–0.0202 V/nm range of the DC bias electric field. The maximum tensile stress is found to be 1.2 GPa, which is much smaller than the fracture stress.

Hydrous Manganese Dioxide Nanowall Arrays Growth and Their Li+ Ions Intercalation Electrochemical Properties

Nanowall arrays of hydrous manganese dioxide MnO2·0.5H2O were deposited on cathodic substrates by the potentiostatic method from a mixed aqueous solution of manganese acetate and sodium sulfate, an...

Formation processes, structure, and properties of spark coatings of armco iron obtained with the use of nanostructured and microstructured WC-Co electrodes

Nanostructured and microstructured electrode materials of the composition 92%WC-8%Co were used for deposition of spark coatings on Armco iron upon variation in the energy of pulsed discharges in the range from 0.01 to 1.2 J. Physicochemical processes on contact surfaces are considered during operation by both types of electrode pairs, namely, in the forming coating of the cathode substrate and in the secondary structure of the anode electrode. It is found that the main phases in coatings are the amorphous phase and tungsten semicarbide W2C. In the case of a nanostructured electrode, an increase in the energy mode above a certain threshold value leads to an increase in the fraction of crystalline phases and to the formation of a structure consisting of submicron W2C/WC grains surrounded by an amorphous binder. With the use of a microstructured electrode, the fraction of the amorphous phase in coatings prevails in all energy modes. The use of nanostructured electrodes in the technology of spark treatment of substrates made from Armco iron is expedient only at a pulse energy of <0.23 J.

Near cathode optical emission spectroscopy in N 2–H 2 glow discharge plasma

Optical emission spectroscopy (OES) is a non-intrusive diagnostic technique, widely used to study different kinds of plasmas. In the present work, a locally resolved OES technique was used to obtain near cathode (substrate) emission spectra for N 2–H 2 glow discharges. It was observed that, along with N 2 + and N 2 lines, the characteristic atomic nitrogen lines at 742.3 nm (3p 4S 0 3/2 → 3s 4P 1/2), 744.2 nm (3p 4S 0 3/2 → 3s 4P 3/2), 746.8 nm (3p 4S 0 3/2 → 3s 4P 5/2) and H α (656.3 nm) were the main emissions coming from the sheath region that shrouded the cathode. A qualitative analysis of the spectral lines near the cathode has been done in order to understand the mechanism of plasma nitriding and the role played by the hydrogen in the nitriding process. The decrease in local intensity of these atomic lines with hydrogen composition suggests that the effect of hydrogen is to enhance the sticking/adsorption of N on the cathode surface.

Electrolytic trichloroethene degradation using mixed metal oxide coated titanium mesh electrodes

Electrochemical systems provide a low cost, versatile, and controllable platform to potentially treat contaminants in water, including chlorinated solvents. Relative to bare metal or noble metal amended materials, dimensionally stable electrode materials such as mixed metal oxide coated titanium (Ti/MMO) have advantages in terms of stability and cost, important factors for sustainable remediation solutions. Here, we report the use of Ti/MMO as an effective cathode substrate for treatment of trichloroethene (TCE). TCE degradation in a batch reactor was measured as the decrease of TCE concentration over time and the corresponding evolution of chloride; notably, this occurred without the formation of commonly encountered chlorinated intermediates. The reaction was initiated when Ti/MMO cathode potentials were less than -0.8 V vs. the standard hydrogen electrode, and the rate of TCE degradation increased linearly with progressively more negative potentials. The maximum pseudo-first-order heterogeneous rate constant was approximately 0.05 cm min(-1), which is comparable to more commonly used cathode materials such as nickel. In laboratory-scale flow-though column reactors designed to simulate permeable reactive barriers (PRBs), TCE concentrations were reduced by 80-90%. The extent of TCE flux reduction increased with the applied potential difference across the electrodes and was largely insensitive to the spacing distance between the electrodes. This is the first report of the electrochemical reduction of a chlorinated organic contaminant at a Ti/MMO cathode, and these results support the use of this material in PRBs as a possible approach to manage TCE plume migration.

Fabrication of enamel-mimicking mineralization composite coating induced by electrolytic deposition (ELD) system

AbstractMature tooth enamel does not remodel nor self-repairs after damage. Therefore, in vitro formation of a uniquely ordered composite similar to enamel is of particular interest. In this study we applied a newly developed electrolytic deposition (ELD) system to promote the amelogenin nano-chain self-assembly and simultaneous calcium phosphate crystallization. Composite coatings of amelogenin-calcium phosphate were prepared on a cathode substrate (Si wafer), from an initial pH of 4-5, and calcium and phosphorus containing solution at room temperature. The effects of a recombinant full-length amelogenin (rP172) and truncated protein without the C-terminal (rP148) on the growth and morphology of the calcium phosphate nano-composite were investigated. A potentiostat was used to control the electrochemical parameters.Following the application of electric current, the local pH around the cathode was increased and resulted in the self-assembly of amelogenin that occurred simultaneously with calcium phosphate mineralization. Transmission and scanning electron micrographs of assembled rp172 amelogenin collected from the 25mM sodium phosphate solution during electrodeposition showed uniform nanospheres and nano-chains structures, while the rP148 formed irregular aggregates. SEM observation of the surface of the nano-composite after electrodeposition, revealed organized nano-rod structures in the presence of rP172, while only nano-sized spherical aggregates were seen in the presence of rP148. ATR-IR confirmed that the mineral phases were mainly octacalcium phosphate, but apatite and amorphous calcium phosphate were also present. Nanoindentation was tested on rP172 and rP148 composite coating. The rP172 composite coating exhibited higher elastic modulus and hardness than rP148 composite. The fracture toughness of rP172 composite was comparable to mature enamel. We therefore conclude that the 24 amino acid hydrophilic C-terminal of amelogenin is essential for the self-assembly, and therefore, for calcium phosphate crystal organization. The new electro-deposition system is effective for fabrication of amelogenin/apatite composites with defined organized structures.

Feasibility of the electrochemical way in molten fluorides for separating thorium and lanthanides and extracting lanthanides from the solvent

An alternative way of reprocessing nuclear fuel by hydrometallurgy could be using treatment with molten salts, particularly fluoride melts. Moreover, one of the six concepts chosen for GEN IV nuclear reactors (Technology Roadmap – http://gif.inel.gov/roadmap/) is the molten salt reactor (MSR). The originality of the concept is the use of molten salts as liquid fuel and coolant. During the running of the reactor, fission products, particularly lanthanides, accumulate in the melt and have to be eliminated to optimise reactor operation. This study concerns the feasibility of the separation actinides–lanthanides–solvent by selectively electrodepositing the elements to be separated on an inert (Mo,Ta) or a reactive (Ni) cathodic substrate in molten fluoride media. The main results of this work lead to the conclusions that:•The solvents to be used for efficient separation must be fluoride media containing lithium as cation.•Inert substrates are suitable for actinide/lanthanide separation; nickel substrate is more suitable for the extraction of lanthanides from the solvent, owing to the depolarisation occurring in the cathodic process through alloy formation.

Electrochemical hydrodechlorination of 4-chlorobiphenyl in aqueous solution with the optimization of palladium-loaded cathode materials

The electrochemical hydrodechlorination of 4-chlorobiphenyl (4-MCB) in aqueous solution containing methanol (MeOH), sodium acetate, acetic acid and bromide of hexadecyltrimethylammonium (CTAB) was investigated under constant current electrolysis at ambient temperature by using a membrane-separated flow-through cell operated in batch-recycle modes. The effects of catalyst type, cathode substrate, cathode recycle, and catalyst loading on the conversion of 1 mM 4-MCB were evaluated. Convention hydrogenation catalysts including Pd, Pt, and Ni and several types of cathode substrates such as metallic mesh/foam and activated carbon material, were tested. It was found that the palladium-loaded nickel foam was most suitable to be used as cathode for the treatment of 4-MCB due to its high performance and stability, which could rapidly dechlorinate 4-MCB to biphenyl with 94.3% conversion and 91.5% yield under constant current of 15 mA after 3 h electrolysis. During the electrolysis, the current efficiencies and energy consumptions were in range of 5.5–20% and 2.1–7.9 kWh kg −1, respectively.