Bronze Electrode Research Articles

Bronze degradation processes in simulating archaeological soil media

The purpose of this study is to establish reliable procedure reproducing the degradation processes that occurred on the archaeological artefacts before their excavation. Two simulating soil media are chosen, the first one (FJ) is made from archaeological soil filtrate and the second is a chloride- and/or sulphate-containing solution (CSJ) taken at the same soil amounts of aggressive ions. According to stationary studies, corrosion mechanism in CSJ medium is catalysed by the presence of chloride at the surface of tin bronze electrode, but sulphate products tend to stabilise the surface of bronze sample immersed in soil filtrate. In FJ, the trend of impedance spectra remains unchanged during the immersion period. Adjusted impedance parameters prove that passivation and depassivation can occur simultaneously on bronze surface with different expansion. In CSJ, impedance data evolve according to the immersion time. The evolution of adjusted parameters according to the immersion time describes well the surface state of the bronze sample. The corrosion process is more difficult while the metallic surface is covered with a bronze corrosion layer “patina” which explain the capacitance decreasing and the resistance increasing (after 50 days). Scanning electron microscopy observations coupled with energy-dispersive X-ray spectrometry analysis approve our electrochemical results.

Electrochemical stability of bis(trifluoromethanesulfonyl)imide-based ionic liquids at elevated temperature as a solvent for a titanium oxide bronze electrode

Four different electrolytes are prepared by dissolving a Li salt in three different room-temperature ionic liquids (RTILs) and also in a conventional organic solvent. The cathodic (electrochemical reduction) stability of these electrolytes is compared at both ambient and elevated temperature by potential cycling on a TiO 2 -B electrode. At room temperature, the stability of pyrrolidinium- and piperidinium-based RTILs is comparable with that of the carbonate-based organic solvent, which is in contrast to the severely decomposed imidazolium-based RTIL. At elevated temperature (120 °C), the imidazolium-based RTIL undergoes even more significant cathodic decomposition that results in the deposition of a resistive surface film and leads to eventual cell degradation. By contrast, the cathodic decomposition and concomitant film deposition are not serious with pyrrolidinium- and piperidinium-based RTILs even at this high-temperature, so that the TiO 2 -B/Li cell operates with reasonably good cycle performance. The latter two RTILs appear to be promising solvents for lithium-ion batteries that are durable against occasional exposure to high-temperature.

Two-joint robot finger design based on multi-degree-of-freedom ultrasonic motors

Ultrasonic motor is one of the most promising candidates for arranging the joints of robot arms or fingers. In this paper, we design and fabricate a robot finger involving two joints with four degree-of-freedom (DOF) based on two hybrid multi-DOF piezoelectric ultrasonic motors. The motor’s stator consists of a multi-layered piezoelectric longitudinal vibrator and a sandwich bending vibrator. The multi-layered vibrator can produce large longitudinal vibration velocity in the z direction at low driving voltage. The sandwich vibrator is composed of two PZT rings and four-divided bronze electrodes, and is driven by phased voltages to excite the bending vibrations in two orthogonal directions. The synthesis of an elliptical motion with the longitudinal and bending vibrations can make a ball rotor rotate in three directions. Two multi-DOF motors are designed and installed in the prototype two-joint-finger. The frequency of the upper motor is 33 kHz and that for the lower motor is 22.8 kHz. In our model, a stainless steel layer is adhered on the stator’s surface to improve the rotation torque, and the maximum torque of 23.5 mNm was obtained for the lower motor. Holding mechanism using a bearing-Teflon disk is introduced to hold the ball rotor without preventing the multi-DOF motions of the robot finger joint. The motions of the finger are demonstrated and evaluated experimentally.

NASICON devices attached with Li2CO3-BaCO3 auxiliary phase for CO2 sensing under ambient conditions

NASICON (Na3Zr2Si2PO12)—based electrochemical devices, constructed in a gas-separation type or planar type, were attached with a Li2CO3-BaCO3 (1:2 in molar ratio) auxiliary phase to investigate their CO2 sensing properties under ambient conditions. The devices were found to be far more resistant to the disturbance by a change in relative humidity (RH) than those using Na2CO3 or NaHCO3 auxiliary phase. The EMF was correlated linearly with the logarithm of CO2 concentration in the range of 0.03–50% CO2 at 30°C, and the linear correlation shifted up or down only slightly with a change in RH between 30 and 90%. For a change in operating temperature, the CO2 sensing capability was kept almost the same at 45°C, while it was deteriorated significantly at 60 and 75°C, especially in the lower RH range. Applicability of a cobalt oxide bronze (Na0.6CoO2) as a solid reference electrode for the planar type device was also investigated. The devices using the bronze reference electrode exhibited the CO2 sensing capability as good as those using the Au reference electrode did. In addition, the bronze electrode was found to much improve the reproducibility of the EMF to a fixed concentration of CO2 among devices.

Electrochemical simulation of friction interactionson the basis of anti-wear behaviour of metallo-dibutyldithiophosphate complexes[(DTP) z M A z+ ] innon-aqueous media

The aim of the present study was to propose a new electrochemicalmodel of anti-wear behaviour of dibutyldithiophosphate complexes[(DTP)zMAz+](where MAz+=Au+,Ag+ or Zn2+) in a non-aqueous model solventon the basis of electrochemical experiments compared withclassical four-ball machine tests on standard 100Cr6 steel. Theelectrochemical behaviour of [(DTP)zMAz+] wasobserved on bronze, copper and 100Cr6 steel electrodes innon-aqueous acetonitrile solutions containing 0.05 M NaClO4 as a supporting electrolyte. Potential peaks(1Ep,c) of the underpotentialdeposition (UPD) of MA metals were observed, and thesequence of 1Ep,c: Au>Ag>Zn valueswas identified. A similar sequence of effectiveness of the[(DTP)zMAz+]anti-wear agents was obtained in the four-ball machine tests.

Electrochemical behaviour of vanadium bronze Li 6V 5O 5 cathode in a secondary lithium battery

A new vanadium oxide that is rich in lithium (Li 6V 5O 15 has been prepared from Li 2CO 3 and V 2O 5 at 680°C for 24 h. The discharge behaviour of the bronze electrode is investigated in an Li/LiAsF 6-PC/bronze battery at various current densities. The new material has good reversibility for lithium insertion; a high specific capacity (more than 340 Ah kg −1) is obtained at 0.2 mA cm −2 and a 1.0 V cutoff voltage. Given the good structural stability of the bronze with Li + insertion, 160 cycles are achieved with the tentative battery. A.c. impedance data for the Li Li 6 V 5 O 15 cell reveal that the cathodic process is controlled mainly by Li + diffusion in the bronze. The new bronze could be used for a low-voltage, rechargeable lithium battery.

Tribological behaviour of an electrodischarge machined surface with a powder metallurgy bronze electrode

Metal transfer from the tool electrode to the machined surface is appreciable in electrodischarge machining when a powder compact tool electrode is used under reverse polarity conditions. A powder metallurgy bronze electrode was employed in the present work and investigation of the frictional behaviour of the resultant surface showed considerable reduction in the friction coefficient. Reduction in wear was also confirmed by a new method using cutting tests, establishing that the surfaces can be used in applications involving extreme pressure and velocity.

The sodium responsive tungsten bronze electrode: An electrode for sodium ion analysis of DNA solutions

The preparation and construction of tungsten bronze electrodes, responsive to sodium ions, are reported. The electrodes were made from tungsten bronze powder (Na 0.4WO 3), compressed into pellets with a resin binder and sealed in epoxy resin. The electrodes were found to respond almost instantenously to changes in sodium ion concentration and to be relatively stable with time. The pH dependence decreases as the sodium ion concentration increases, indicating suitability for solutions of sea water concentration. Unfortunately the electrodes show a response to potassium ions of apparently equal magnitude to the sodium response between 0.001 mol kg −1 and 0.1 mol kg −1. Preliminary tests indicate that they also respond to lithium, calcium, aluminium, cupric and tetramethylammonium ions at concentrations of 0.1 mol kg −1. At high sodium ion concentrations (⩾ 1 mol kg −1) the effect of cross sensitivity is negligible for these ions. No attempts are made in this short paper to evaluate selectivity coefficients. Some data demonstrating the low but linear response to sodium ion are given. Tests carried out in DNA—saline-bearing solutions suggest that the possible suitability for marine or biological applications.

Statistical time lag of gas discharge in electrostatic recording

AbstractElectrostatic recording is applied widely to facsimiles and printers because of its high speed and high resolution. the time lag in gas discharge formation causes dots to be missed, which must be improved for high‐speed, high resolution recording. We tested the latent image formation by using an aluminum drum coated with a dielectric film uniformly charged to positive potential and a pin electrode. the effects of the pin electrode material, the recording pulse repetition period, and the recording voltage on the statistical time lag on initiating discharges have been investigated. the following results were obtained: (1) A phosphor bronze electrode causes the smallest time lag, followed by nickel and tungsten. (2) the logarithm of the mean statistical time lag is proportional to that of the repetition period. (3) the logarithm of the mean statistical time lag is inversely proportional to the air gap electric field. (4) When the recording pulsewidth is larger than 15 μs for a gap field of 55 MV/m and a recording pulse period of 10 s, the dots missing probability becomes less than 1%.

Electronic structure of the hypothetical electrode material PtWO 3

We have calculated the energy bands and the density of electronic states of the hypothetical solid PtWO 3. The results confirm that the electronic structure of this material is very similar to that of Pt metal, and this may be the reason for the high electrocatalytic activity of certain Pt contaminated sodium tungsten bronze electrodes.

ChemInform Abstract: ELECTROCATALYTIC ACTIVITY OF CUBIC SODIUM TUNGSTEN BRONZE. II. EFFECTS OF INTENTIONAL PLATINIZATION

AbstractEinige der mit Platin dotierten NaxWO3‐Elektroden besitzen bessere Aktivitäten und Stabilitäten als massive Platinelektroden.

Electrocatalytic Activity of Cubic Sodium Tungsten Bronze: I. Effects of Platinum Doping, Anodization, and Platinum Pre‐Electrolysis of the Electrolyte

The electrocatalytic activity of cubic sodium, tungsten bronzes, including high purity and platinum‐doped crystals, has been measured for oxygen reduction before and after anodization in both fresh and platinum pre‐electrolyzed acid solutions. The effects of platinum doping, anodization, and platinum pre‐electrolysis have been separately studied for current densities between 10−8 and 10−3 A/cm2. A previously unreported break in the Tafel curve at was observed for all clean undoped bronze samples. Below this break the Tafel slope was −110 mV/decade while above it the Tafel slope was −200 mV/decade. Anodization of a pure bronze electrode failed to produce any change in the Tafel curve. Platinum pre‐electrolysis of an anodized, undoped bronze produced a general increase in activity for all current densities. The break in the Tafel curve increased to while the Tafel slopes above and below this current density were unchanged. Platinum doping to 130 ppm increased the electrode activity at current densities below, even when measured in platinum‐free solutions before anodization of the electrode. The increased activity of an unanodized electrode in fresh solutions could be accounted for by the surface platinum concentration expected from the bulk platinum doping. Anodization of a doped bronze electrode increased the limiting current from even in fresh solutions while subsequent platinum pre‐electrolysis increased the limiting current to . Auger analysis of the anodized, platinum‐doped electrode exposed to the platinum pre‐electrolyzed solution revealed platinum on the surface of the bronze electrode at a coverage sufficient to account for the increased electrode activity below . A small but reproducible increase in activity was found at high current densities near 10−3 A/cm2 after either a pure or platinum‐doped bronze electrode was exposed to a platinum pre‐electrolyzed solution that lead to the research reported in the following paper (II).

Electrocatalytic Activity of Cubic Sodium Tungsten Bronze: II . Effects of Intentional Platinization

This paper is an extension of the work reported in the preceding paper (I) and concerns the effects of intentional platinization of sodium tungsten bronze electrodes on their electrocatalytic activity for oxygen reduction in an acid electrolyte. Some of these electrodes had activities and stabilities at 10−3A/cm2 better than those for bulk platinum electrodes measured in the same solutions. The samples were prepared by three separate techniques and were characterized by SEM, cyclic voltammetry, x‐ray dispersive analysis, Auger surface measurements, depth profiles, and microprobe analysis. Two types of platinum morphology were produced. The first type consisted of 1000–3000Å platinum particles attached to a platinum‐free bronze surface. For platinum coverages less than a few percent the activity of the electrodes was proportional to . The apparent activity per platinum atom was higher than that of bulk platinum although surface roughening effects made it difficult to quantify the specific activity of these electrodes. For approaching 10% there was a large unexplained increase in activity. The second type of platinum morphology is best viewed as layer of on top of the bronze surface. These electrodes failed to exhibit any reduction peak even though the Auger results indicated platinum atoms were present. In some cases, it was found that the activity per atom was as good as that of bulk platinum and that these electrodes had better long‐term stability than bulk platinum. In all cases the bronze provided: (i) a corrosion resistance support, (ii) a good lattice matrix for either the growth of platinum particles or the incorporation of layers, and (iii) an electronic environment comparable to bulk platinum with its large density of states near the Fermi level. Techniques used in this study could provide the basis for construction of an economical fuel cell cathode.

Oxygen Reduction on Sodium Tungsten Bronze Electrodes and the Effects of Adsorbed Platinum

The Tafel slopes for oxygen reduction on sodium tungsten bronze electrodes are changed from -4RT/F to -2RT/F by adsorption of platinum from solution. Adsorbed platinum reduces the time to attain steady-state conditions but does not catalyse the reaction. Photo-excitation experiments show that the flat band potential is a function of CH+. Results are interpreted in terms of a thin surface layer of low donor density which is non-degenerate in the potential range of oxygen reduction. It is shown that, without adsorbed platinum, changes in the equilibrium potential difference across the surface layer equal those across the Helmholtz layer due to the presence of hydrogen donors in the lattice and results in -4RT/F Tafel slopes. It is proposed that adsorbed platinum forms surface states pinning the Fermi level at the surface and causing changes in the potential difference to occur entirely across the Helmholtz layer; this results in -2RT/F slopes.

Studies of the electropolishing of beryllium bronze specimens Part 2. A cylindrical electrode moving forwards

Electropolishing of a beryllium bronze electrode moving through 14.6 M orthophosphoric acid has been investigated. The results of a previous investigation were used. An explanation is given for the difference in current versus potential curves compared with those for polishing a motionless electrode. The influence of variations in the electrode pass velocity and in flow velocity on the current value has been determined. The thickness of the layer that must be dissolved to obtain the required surface smoothness has been estimated. The investigations give a basis for the development of the technology of preparation of thin cylindrical magnetic films.

Behavior of Pure and Platinum‐Doped Sodium Tungsten Bronze Electrodes in Oxygen‐Saturated Phosphoric Acid

Platinum‐doped tungsten bronze electrodes of composition have been examined for the reduction of oxygen in and , together with orthophosphoric acid at various concentrations up to 14.5N (85 weight per cent). Whereas good activities of aged electrodes were shown in and , those in were poor. This is attributed to the formation of phosphotungstate. It is concluded that such compounds are unsuitable for use as catalysts in phosphoric acid fuel cells.

Simple redox processes at tungsten bronze electrodes

The kinetics of the couples Fe(CN)64−/Fe(CN)63− and Fe(Ox)44−/Fe(Ox)43− at five tungsten bronze electrodes, NaxWO3, in aqueous solution have been investigated by cyclic voltammetry. The tungsten bronzes have also been shown to be suitable electrode materials for work in aprotic solvents and the reduction and oxidation of aromatic hydrocarbons at these electrodes is reported; there are substantial similarities between cyclic voltammograms recorded at tungsten bronzes and at mercury and platinum respectively.

Short-time sintering of aluminum bronze electrode strip

1. A study was made of the strength properties of facing electrode strip in aluminum-iron bronze to which aluminum had been added by three different methods. 2. It is shown that the highest values of strength are attained by subjecting strip alloyed with pure aluminum of less than 50-μ particle size to short-time sintering (for not more than 45 sec).

Simple redox processes at tungsten bronze electrodes

The kinetics of the couples Fe(CN) 6 4− /Fe(CN) 6 3− and Fe(Ox) 4 4− /Fe(Ox) 4 3− at five tungsten bronze electrodes, Na x WO 3 , in aqueous solution have been investigated by cyclic voltammetry. The tungsten bronzes have also been shown to be suitable electrode materials for work in aprotic solvents and the reduction and oxidation of aromatic hydrocarbons at these electrodes is reported; there are substantial similarities between cyclic voltammograms recorded at tungsten bronzes and at mercury and platinum respectively.

The Electroreduction of Oxygen and Hydrogen Peroxide on Sodium‐Tungsten Bronzes

Sodium‐tungsten bronzes of the general formula , with high and low platinum contents, were investigated regarding their electrocatalytic activity towards the reduction of oxygen and hydrogen peroxide in sulfuric acid solutions. Contrary to the findings of some other workers are found to be poor catalysts for the cathodic reduction of oxygen. The presence of platinum in the bronze at concentrations in the 1000 ppm range does not increase significantly the catalytic properties of the bronze electrode. Sodium tungsten bronzes are relatively good catalysts for the cathodic reduction of hydrogen peroxide in acid solutions. The reaction is first‐order with respect to the concentration and zero‐order with respect to the H+ concentration. The steady‐state current‐potential curve exhibits a slope of and, at more cathodic potentials, a characteristic inhibition inflection. In contrast to other electrodes the cathodic reduction of on occurs at potentials less cathodic than those required for the reduction of oxygen.