Electrodes sintered-positive

A device for foam dispersity determination by measuring the local foam expansion ratio and the pressure in Plateau borders is illustrated in Fig. 4.4. It consists of a glass container equipped with platinum electrodes and a micromanometer. The container bottom is a porous plate (a sintered glass filter). The pressure Ap is measured with a capillary micromanometer and the expansion ratio is determined by the electrical conductivity of the foam. The manometer and the electrodes are positioned so that to ensure a distance of 1.0-1.5 cm between them and the porous plate. When the distance is small the liquid in the porous... 

The sintered positive electrode consists of a sintered porous nickel plaque that is impregnated with nickel hydroxide active material. The porous sintered plaque serves to retain the active nickel hydroxide material within its pores and to conduct the electric current to and from the active material. Essential features of the sintered plaque are high porosity, large surface area, and electrical conductivity in combination with good mechanical strength. ... 

Rectangular cells with sintered electrodes, SD series (Varta CD type), are suitable for applications in which a high rate of discharge, or operations at extremes of temperature, or permanent trickle is required. The cells are constructed from cut sintered positive and negative plates, separated by a highly porous separator which absorbs all the free electrolyte within the cell. A safety vent is incorporated within each cell to enable gas which may build up under fault conditions to be released. All cells in this range have the cases connected to the positive electrode. All cases are not insulated but intercell separators and nickel-plated connective links are available. The CD series is available made up in metal boxes. 

Energy densities currently being achieved are 20-30 Wh/kg (tubular plate electrodes) and 40-60Wh/kg (sintered plate electrodes). The positive plate comprises thick sintered nickel plates on a nickel plated substrate. The negative plate comprises a mixture of powdered iron and Fe30a. The electrolyte contains 1.2 to 1.3g/cm potassium hydrioxide containing 1-2% lithium hydroxide. The cells are vented. Synthetic fibres are used for separators. 

Eor the negative electrolyte, cadmium nitrate solution (density 1.8 g/mL) is used in the procedure described above. Because a small (3 —4 g/L) amount of free nitric acid is desirable in the impregnation solution, the addition of a corrosion inhibitor prevents excessive contamination of the solution with nickel from the sintered mass (see Corrosion and corrosion inhibitorsCorrosion and corrosion control). In most appHcations for sintered nickel electrodes the optimum positive electrode performance is achieved when one-third to one-half of the pore volume is filled with active material. The negative electrode optimum has one-half of its pore volume filled with active material. 

The H-type cell devised by Lingane and Laitinen and shown in Fig. 16.9 will be found satisfactory for many purposes a particular feature is the built-in reference electrode. Usually a saturated calomel electrode is employed, but if the presence of chloride ion is harmful a mercury(I) sulphate electrode (Hg/Hg2 S04 in potassium sulphate solution potential ca + 0.40 volts vs S.C.E.) may be used. It is usually designed to contain 10-50 mL of the sample solution in the left-hand compartment, but it can be constructed to accommodate a smaller volume down to 1 -2 mL. To avoid polarisation of the reference electrode the latter should be made of tubing at least 20 mm in diameter, but the dimensions of the solution compartment can be varied over wide limits. The compartments are separated by a cross-member filled with a 4 per cent agar-saturated potassium chloride gel, which is held in position by a medium-porosity sintered Pyrex glass disc (diameter at least 10 mm) placed as near the solution compartment as possible in order to facilitate de-aeration of the test solution. By clamping the cell so that the cross-member is vertical, the molten... 

For many years, sintered-nickel electrodes have been used as the positive electrodes for sealed-type nickel-cadmium batteries. With an increase in the demand for high energy density, this type of elec-... 

Fig. 16. Small-scalo laboratory cell for preparative electrolysis. A, Pt gauze working electrode. B, Pt sheet secondary electrode. C, Reference electrode. D, Luggin capillary on a syringe barrel so that the position of the tip of the Luggin probe relative to the working electrode is readily adjustable. E, Glass sinter to separate anode and cathode compartments. F, Gas inlet to allow stirring with inert gas or the continuous introduction of reactant. G, Three-way tap where a boundary between the reference electrode and the working solutions may be formed.

In principle, the auxiliary electrode can be of any material since its electrochemical reactivity does not affect the behaviour of the working electrode, which is our prime concern. To ensure that this is the case, the auxiliary electrode must be positioned in such a way that its activity does not generate electroactive substances that can reach the working electrode and interfere with the process under study. For this reason, in some techniques the auxiliary electrode is placed in a separate compartment, by means of sintered glass separators, from the working electrode. 

The auxiliary electrode, which is normally a mercury pool, must be positioned in a compartment separate from the working electrode. Such a separation compromises the desired symmetric disposition of the electrodes. Normally, the compartments of a macroelectrolysis cell are separated by sintered glass frits, such that the catholyte and the anolyte are not mixed. In fact, if the working electrode is involved, for example, in a cathodic process, the auxiliary electrode will act as an anode. This implies that the auxiliary electrode will produce oxidized material (by anodic decomposition of the solvent itself, of the supporting electrolyte, of mercury-contaminated products or of electroactive residues diffused at the auxiliary electrode) that may subsequently be reduced at the working electrode, contaminating and falsifying the primary process. 

The positive electrodes are usually fabricated by sintering of silver powders and... 

Cell construction is mainly confined to two types, using either pocket plate electrodes (vented cells) or sintered , bonded or fibre plate electrodes (vented and sealed cells). In the former, the active materials are retained within pockets of finely perforated nickel-plated sheet steel which are interlocked to form a plate. Positive and negative plates are then interleaved with insulating spacers placed between them. In sintered plate electrodes, a porous sintered nickel mass is formed and the active materials are distributed within the pores. In sintered plate vented cells, cellulose or other membrane materials are used in combination with a woven nylon separator. In sealed or recombining cells, special nylon separators are used which permit rapid oxygen diffusion through the electrolyte layer. 

While there are a number of methods used for manufacturing the positive electrodes, the two most important processes are the sintering of silver powders and slurry pasting. The former procedure produces electrodes with superior mechanical properties. The silver mass which is formed by... 

As shown in Fig. 8.14 the cell is formed in principle by two liquid electrodes, the sodium negative and the sulphur positive, separated by a tube of sintered polycrystalline /3-alumina. Since sulphur is an insulator, the compartment containing the sulphur electrode is fitted with a carbon felt current collector. The cell, which may be written as... 

Another technique, used by Figaro Engineering Inc. and others, is to coat an alumina tube with tin oxide in an organic matrix, such as stearic acid, and sinter at 400-700 °C. A porous film results. Electrodes at either end of the tube are printed on or embedded in the sintered oxide and a platinum heater coil is positioned inside the tube. 

As has already been described in the Introduction, the first electrochemical ESR experiment was performed by Ingram and co-workers [2] who demonstrated the formation of aromatic radical ions in electroreductions. However, the real potential of the joint electrochemical ESR technique was demonstrated first by the work of Maki et al. [3, 4,12-14], They obtained the first solution spectra of electrochemically generated radicals and by doing so performed the first in-situ electrochemical ESR experiment. This was performed in a two-electrode electrolysis cell, the anode being a platinum wire within a 3 mm o.d. capillary tube, the lip of which was positioned centrally, along the axis of a cylindrical cavity. The cathode was separated from the anode by sinters and was outside the ESR cavity. The system... 

Figure 26-S presents a construction which is fairly insensitive to thermal shock [22]. A zirconia membrane is tightly sintered to a Pt tube which forms the electrode shaft. The lifetime also of this arrangement is limited by corrosion of the membrane, which, in addition, is subject to so-called bubble boring, especially in a horizontal position [4].

---