Effect Of Different Electrode Materials Research Articles

Effect of electrode thermal conductivity in cardiac radiofrequency catheter ablation: A computational modeling study

Purpose: Radiofrequency (RF ablation) is the treatment of choice for certain types of cardiac arrhythmias. Recent studies have suggested that using gold instead of platinum as the electrode material for cardiac catheter ablation leads to larger thermal lesions due to its higher thermal conductivity. In this study we created computer models to compare the effects of different electrode materials on lesion dimensions using different catheters, insertion depths, and flow rates.Materials and methods: Finite element method (FEM) models of two cardiac ablation electrodes (7Fr, length 4 mm and 8Fr, length 10 mm) made of platinum, gold, and copper were created with tissue insertion depths of 0.75, 1.25, and 2.5 mm. Convective cooling was applied to the electrode and tissue based on measurements from previous studies at different flow rates. RF ablations were simulated with both temperature control and constant power control algorithms to determine temperature profiles after 60 s.Results: With the constant power algorithm there was no difference in lesion dimensions between the electrode materials over the range of parameters. With the temperature control algorithm, lesion width and depth were only marginally larger (∼0.1–0.7 mm) with the gold and copper electrodes compared to the platinum electrode for all parameter combinations.Conclusion: Our computer modelling results show only minor increases in thermal lesion dimensions with electrode materials of higher thermal conductivity. These observed differences likely do not provide a significant advantage during clinical procedures.

An experimental investigation on the surface characteristics of tungsten carbide for the fine-finish die-sinking and scanning micro-EDM

In this paper, a comprehensive study on the surface characteristics of tungsten carbide (WC) obtained in die-sinking and scanning micro-EDM is presented based on the crater characteristics, surface topography, average surface roughness (Ra) and peak-to-valley roughness (Rmax). The investigation shows that fine-finish micro-EDM requires minimisation of the pulse energy supplied into the gap which was found difficult to apply in die-sinking due to frequent arcing, short circuiting and unstable machining conditions. Consequently, the machined surface becomes defective due to the presence of microcracks, voids and deposition of debrises in die-sinking micro-EDM. However, the surface generated in scanning micro-EDM is less susceptible to surface defects along with lower Ra and Rmax. Investigation has also been carried out on the effect of different electrode materials on surface characteristics of WC. It was found that silver tungsten electrode provides better surface characteristics compared to tungsten and copper tungsten for the fine-finish micro-EDM of WC.

Effect of Different Electrode Materials on the Performance of Smart Composite Actuators Based on Dielectric Elastomers

Dielectric elastomers are a class of electro-active polymers (EAPs) which have great potentials to be used in smart composites. These materials with compliant electrodes are converters of electrical energy to mechanical energy in order to produce external load and strain with good efficiency. Electrode materials should typically have good compliancy so that undergo large strain alongside the film, without producing any additional stress and constraint for the actuator. In the present study, the effect of 4 different electrode materials (graphite filled silicone oil, silver filled grease, graphite powder and electrically conductive silicone rubber) on the performance of dielectric elastomer actuators has been studied. The principle of operation, the method of fabrication and test method of planar actuators are discussed. We have also studied the effects of different driving voltages and different prestrain values on the actuator response. Experimental results showed that electrical conductivity, material compliancy, and compatibility with substrate in the electrode materials are some of the important parameters affecting the actuator performance.

Effect of different electrode materials on electrophoretic depositional behavior of yttria-stabilized zirconia powder

The electrophoretic depositional (EPD) behavior of yttria-stabilized zirconia (YSZ) powder with 8 mol% Y2O3, which is a common material for oxygen sensors as a solid electrolyte, was investigated on stainless steel and carbon based substrates. Ethanol + HNO3 based suspensions were used for the EPD experiments, and three different YSZ powders, one commercially available powder and two own-made coprecipitated powders, were deposited. The latter powders were calcined at 900 and 1200 °C, respectively. The concentration of the suspension was 3 g/300 cm3 and a small amount of HNO3 solution was added as a dispersant. A DC electric field of 100–200 V/15 mm was applied between parallel electrodes. On stainless steel electrodes it was found that the own-made coprecipitated powder calcined at 1200 °C, showing the best deposition properties, whereas the commercial YSZ powder showed the best depositional properties on carbon electrodes. These characteristic depositional behaviors are discussed with regard to the adhesive force between the particles and the different electrodes, and some powder properties, e.g., particle size distribution and packing behavior. A thick, continuous, free-standing YSZ film with a thickness of around 10 μm was successfully obtained after firing the deposit on the carbon electrode in flowing air.

Equilibrium and non-equilibrium conductance response of sintered SnO 2 samples to CO

Conductance responses of some sintered samples of SnO 2 prepared in the form of thick films have been studied in the CO concentration range from one ppm upwards in dry synthetic air and also in ambients containing different amounts of humidity. The experiments have been carried out both at equilibrium conditions, by allowing the samples to stabilize at different constant temperatures, and at non-equilibrium conditions, by continuously cycling the sensors between two temperatures. The effects of different electrode materials and of some additives like antimony in SnO 2 on the conductance response to CO under equilibrium and non-equilibrium conditions have been studied. In this paper the emphasis is to describe some measurements concerning a peculiar effect of electrode materials (between Au and Pt) and Sb doping on the conductance response to CO in the temperature-pulsed mode of sensor operation. A drastic difference in the non-equilibrium conductance response to CO in ambients containing humidity is found between Sb-doped SnO 2 sensors with Au and Pt as electrode materials.

A dielectric study of poly(ethylene‐co‐vinyl acetate)‐poly(vinyl chloride) blends. III. Direct current conductivity and electrode polarization

AbstractThe large direct current (d.c.) conductance observed at low frequencies and high temperatures in conjunction with a simple electrical circuit model was used to calculate specific conductivities in PVC and mixtures of PVC with a poly(ethylene‐vinyl acetate) copolymer. Activation energies for d.c. conduction and dipole relaxation in PVC and the blends were found to be in reasonable correspondence. The effects of different electrode materials on the d.c. conductance as well as on electrode polarization are discussed.

PTC Behaviour of Semiconducting BaTiO3Ceramics

The effects of dopants, e.g. oxides of La, Sb, Nd, Gd, Y, Nb etc have been studied on the PTC behaviour of polycrystalline BaTiO3. Sb-doped material showed the best characteristics under our experimental conditions. A systematic study on the effects of different electrode materials like Ag, In, In-Ga and Ni has also been carried out. The contact resistance was exceptionally high for Ag and In, but negligible in case of either In-Ga or Ni. Impedance measurement at different frequencies has been used to distinguish between the intra-grain, inter-grain and electrode-contact resistances. Power-limiting capability of the prepared specimens has been tested by measuring I-V characteristics.

The low current carbon arc and the properties of graphite near the sublimation temperature

Old and new data on the crater radiation from the low current carbon arc have been examined on the basis of two different hypothetical interpretations: 1. (a) the radiation originates from the crater surface 2. (b) the radiation originates from the crater surface and from particles in the arc stream. 1. (a) The available data from the low current carbon arc provide strong evidence that the radiation from the crater can be characterized by a surface temperature near 3800K; the measured values of spectral radiance are in complete agreement with those expected from the Planck radiation formula and the measured values of spectral reflectance (and emittance) over a range of wavelengths from below 0.3 μm to above 1.7 μm. A critical analysis has resolved the differences in spectral reflectance reported by different workers. The cooling of the crater surface after arc extinction has been measured and analyzed to obtain a value of thermal conductivity of the electrode material at temperatures near 3800K that is 25 to 50 times smaller than the values for the bulk electrode materials. Irradiation-produced changes of the temperature of the crater surface are those expected from this low value of thermal conductivity. The microstructure of the crater surface of the electrode is examined for correlation with the decrease of the reflectance and of the thermal conductivity observed near the crater temperature 2. (b) The contrary interpretation of the radiation from the crater assumes that particles emitted from the crater seriously distort the observations of crater radiance. Our model, consisting of a cloud of graphite particles of radius 0.08 μm and the crater surface at temperatures, respectively, above and below the value 3800K, gives a promising explanation of the observed radiance of the graphite-based electrode but not the lampblack-based one. It may also explain the changes in radiance of the graphite-based electrode caused by irradiation of the crater and those occurring after extinction of the arc, without requiring anomalous reduction of the spectral reflectance and the thermal conductivity near 3800K temperature. However, the irradiation-produced increase of crater radiance is wrongly predicted to be greater for the graphite-based electrode than for the lampblack-based one. The failure of the “surface-plus-particles” model to account for the effect of different electrode materials as contrasted with the near-total success of the “surface” model tips the balance of evidence strongly toward the validity of the latter model.

Transfer of Electric Charges through Rutile Single Crystals

Electron transfer and onset of field emission has been investigated in Ti${\mathrm{O}}_{2}$ single crystals with dc currenttime characteristics parallel and perpendicular to the optic axis as function of voltage, temperature, electrode material, and light absorption. The currents are much larger and field emission sets in at lower voltage when the field is parallel to the optic axis. Higher temperature favors the current transfer by increasing the carrier mobility. The effect of different electrode materials proved minor, except in the case of Ti, which as cathode raised the current by about one order of magnitude. Photoelectric measurements showed that, in the critical voltage region of incipient field emission, light absorption can apparently force the current reversibly into the field-emitting stage.