Electrodes heated wire

The Ru single crystal was oriented by Laue x<-ray back-scattering to within 1° of the Ru(001) plane, cut by a diamond saw and mechanically polished. After being etched in hot aqua regia for about 15 min, the crystal was spot welded to two tantalum heating wires which were connected to two stainless steel electrodes on a sample manipulator. The temperature was monitored by a Pt/Pt-10% Rh thermocouple which was spot welded to the back of the crystal. 

To try to separate the oxidation of adsorbate from that of bulk methanol, a droplet cell, shown in Fig. 3-2, was used. A working electrode, platiniun wire, is dipped into an electrolyte droplet on a capillary, which is then connected to the electrolyte reservoir. The top portion of the capillary was covered with Teflon FEP held by Teflon heat shrinking tube. The counter electrode, platinum wire, is in the capillary and its tip reaches just below the droplet. The reference electrode, R. H. E., is constructed between the reservoir and the droplet. 

The hot-wire anemometer, principally used in gas flow measurement, consists of an electrically heated, fine platinum wire which is immersed into the flow. As the fluid velocity increases, the rate of heat flow from the heated wire to the flow stream increases. Thus, a cooling effect on the wire electrode occurs, causing its electrical resistance to change. In a constant-current anemometer, the fluid velocity is determined from a measurement of the resulting change in wire resistance. In a constant-resistance anemometer, fluid velocity is determined from the current needed to maintain a constant wire temperature and, thus, the resistance constant. 

The CVD reactor consists of a vitreous silica tube of about 20 cm in diameter (8") and a height of 30.5 cm (1 ft). The filament was made from tantalum wire with 0.5 mm diameter and attached to water-cooled copper electrodes. Heat treatment in a methane atmosphere produces a thin layer of tantalum carbide that protects the sample from contamination with metallic tantalum. A gas-leaking unit allows the introduction of various gases and their mixtures into the reaction chamber under controlled pressure. Before introducing or changing the gas the unit s internal pressure was reduced by a mechanical pump to about 0.1 Pa. 

Fig. 7.22 The electrode assembly (plug B in Fig. 7.20) (P) a reference electrode (this is a 2.0 mm diameter Ag rod for an Ag/Ag electrode, or an Ag rod with an AgCI coating over the lowest 2 cm for an Ag/AgCI electrode, (Q) heat-shrunk Teflon tubing, (R) aqueous AgNOa (0.01 mol L for an Ag/Ag electrode) or KCI (4.0 mol L for an Ag/AgCI electrode), (S) a Vycor porous disc, (T) the working electrode (platinum wire), (U) the counter electrode (Platinum wire), and (V) neoprene O-rings.

The reciprocal of the run length (q.v.), i.e. the length of MMA electrode required to deposit unit length of weld bead and which is proportional to the heat input, divided by the square of the electrode core wire diameter. 

Figure 2 Cross-sectional view of an electrophoretic apparatus. A, Furnace B, electrophoresis chamber C, capillary D, tube supporting the capillary E, screw to adjust the height of the tube F, electrophoretic support medium G, heat-resistant glass plate H and H graphite electrodes I and I, reservoirs L, thermal couple M, heating wire, and N, insulating jacket. (Reproduced with permission from Alberti G, Allulli A, and Modugno G (1964) Journal of Chromatography 5 420-429.)...

Fig. 5.4 Schematic diagram of the CE-ECL detection system equipped with an electrically heating CPE. WE working electrode RE reference electrode CE counter electrode a the grounding of high-voltage power b, d connect to the function generator c connect to the potentiostat e the Ag/AgCl electrode /platinum wire. Reprinted with permission from Ref. [20].

There are several different devices for determination of dust explosion characteristics. All devices include a vessel which may be op>en or closed, an ignition source which may be an electrical spark or electrically heated wire coil and a supply of air for dispersion of the dust. The simplest apparatus is known as the vertical tube apparatus and is shown schematically in Figure 15.4. The sample dust is placed in the dispersion cup. Delivery of dispersion air to the cup is via a solenoid valve. Ignition may be either by electrical spark across electrodes or by heated coil. The vertical tube apparatus is used for the classification test and for determination of minimum dust concentration for explosion, minimum energy for ignition and in a modified form for minimum oxygen for combustion. 

Analytical solution of the differential equations given above is not useful or even impossible. The problems of heat transport as well as of particle diffusion can be solved much better by digital simulation. This way, the temperature profiles d77dx as well as the concentration profiles dc/dr have been calculated for the convectimi-free period existing at a heated wire electrode of 25 pm in diameter. For this purpose, the solutimi surrounding the wire is separated in cylindric shells, so as if it would cOTisist of nested valves (Fig. 5.3). The dimensions of individual shells should be small enough to allow utilisation of linear equation forms of heat conduction and of diffusion, respectively. Linear transport of heat or matter into every ring as well as away from it is calculated for consecutive short time intervals At by means of oidy two equations ... 

As stated above, the layer containing the temperature profile seems to possess a complex substructure. If, at a permanently heated wire electrode, a voltammetric experiment is performed, then, as mentioned above, a constant limiting current is found. It seems that inside the region with T Tq exists a stagnant layer, although just at places nearest to the electrode surface should act the strongest forces to cause... 

Fig. 6.2 Working electrode design with 25 jun metallic wires. Top schematic representation (a) Printed board carrier, (b) heated wire, (c) copper leads,...

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