Electrodes flame sprayed

Finally, the protective coating over the outer electrode must resist abrasion by particulates in the exhaust gas, must be porous to allow access of the exhaust to the outer electrode, must adhere to the outer electrode, must have expansion characteristics compatible with the electrolyte, and must be stable under oxidizing and reducing conditions at temperatures up to 1000 C. A flame sprayed spinel (MgAl20 ) coating as shown in Figure 9 meets these requirements. 

The top of the reaction chamber is hinged to permit access to the lower electrode (platen) that holds the wafers. This arrangement is illustrated in Figure 20. The platen is anodized, while the upper electrode is bare aluminum. The upper electrode housing is flame spray coated with aluminum oxide to eliminate electrical discharges above the upper electrode. The platen has pockets to accept wafers and maintain them in fixed positions as it rotates. 

Metal electrodes are usually applied by flame-spraying, and the unit is then subjected to a series of high current pulses (about lOMAm-2 for 10 /is) with alternating polarity - a treatment that stabilizes the properties. Units are usually... 

This may be either a continuous process, used when the sample size is relatively large (1 ml or more), or a discrete process, used with samples of less than 20 /il. Continuous-flow systems are simpler to use and more precise, but they are less sensitive. They employ a nebulizer in association with a flame or gas plasma, and either a rotating electrode (Rotrode) or drip-feed to the electrode with the arc or spark. The pneumatic nebulizer has an efficiency of 5-10% and generates an inhomogeneous aerosol. Efiiciency can be improved by proper design of the nebulizer and spray chamber (N4), by use of heated nebulizer gas (R6) or ultrasonic devices (S23). The maximum improvement is a 5- to 10-fold increase in sensitivity. There is also an increase in the complexity and cost of the instrument which usually offsets these benefits. The effect... 

E vs. I (corrected for iR drop) 0.8 mg/cm screen printed electrode O MS29 CCVC prepared catalyst Dry carbon CCVC preparation of catalyst V HISPEC 4000 flame-based dry spray prepared layer... 

The cathode of the lamp which is filled with Ar or Ne at low pressure, sputters when a H.V. is applied to the electrodes. Collision of the noble gas and metal atoms excite the latter then they emit radiation in the visible/u.v. region of the spectrum. The metal compound in the sample to be analysed, dissolved in a suitable solvent, has to be transformed to a mist of gaseous atoms. This is generally achieved by aspirating the solution into a nebuliser where a mist is sprayed in a flame of a flammable gas widi an oxidising gas. The gas mixture may pass through the nebuliser first or it may burn directly. Alternatively, furnace atomisers are used, when smaller volumes of test solutions can be handled. The solution is placed in a horizontal graphite tube or a carbon rod which are heated in an electric furnace. 

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