Positive plate reactions during formation

Chemical and Electrochemical Reactions during Formation of Lead—Acid Battery Positive Plates... 

The electrochemical reactions that proceed during the formation of positive plates can be represented by the following equations. Eh represents the equilibrium potential for the reaction at 298.15 K. 

The reactions that proceed during positive-plate formation have been identified by the accompanying changes in phase and chemical composition of die plates, as well as by the changes in bofli open-circuit and charge potentials of the plates. The phase composition is determined by X-ray diffraction analysis (XRD) and the chemical composition through conventional analytical methods the potentials are measured vs. a Hg Hg2S04 reference electrode. 

It has been established that thermopassivation of the positive plates is a result of ehanges in composition of the lead oxide corrosion layer [1]. This is a very thin film formed during the formation process and is composed mostly of PbOi- When the plates are heated to above 80 °C, Pb of the grid reacts with Pb02 via a solid-state reaction yielding non-stoichiometric PbOn. When the stoichiometric coefficient decreases below a critical value (n < 1.5), the resistance of the corrosion layer increases significantly, which causes thermopassivation of the plates. 

Therefore, such lithographic plates can be considered as dual operating materials because both photonie (electron transfer between Sens and A) and thermal events determine the desired sensitivity. Certain fluorescence would be necessary to obtain circumstances where the electron transfer may compete with the faster internal conversion. The latter releases heat that additionally accelerates chemical reactions during cross-linking. Thus, NIR-photopolymers benefit from both photonic events and thermal processes. Heat release can also contribute to a faster electron transfer and therefore more efficient formation of initiating species particular in case when AGei becomes slightly positive (equation [7.7]). 

The reaction between the ions of the solution and the initial solid porous phases proceeds in a reaction layer, which is located between the zone of the initial phases and the zone occupied by the reaction products. The reaction layer shifts in space and penetrates the volume of the initial phase zone. Thus, the volume of the zone occupied by the reaction products grows at the expense of the initial phase zone. The direction in which the reaction product zone grows depends on the transport hindrances experienced by the ions on their way from the solution volume to the reaction layer and/or on the transport difficulties met by the ions formed in the reaction layer on their way to the solution volume. On soaking and formation of the positive and negative plates, some zonal processes occur. During soaking, only chemical reactions proceed in the reaction layer (i.e., chemical zonal processes). 

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