Lead grain structure

Fig. 4. Grain structure of lead—2 wt % antimony alloy battery grid at a magnification of 50x (a) no nucleants (b) containing 0.025 wt % selenium as a grain...

The anodes are generally not of pure metals but of alloys. Certain alloying elements serve to give a fine-grained structure, leading to a relatively uniform metal loss from the surface. Others serve to reduce the self-corrosion and raise the current yield. Finally, alloying elements can prevent or reduce the tendency to surface film formation or passivation. Such activating additions are necessary with aluminum. 

A number of effects lead to loss of profile depth resolution. The effect of crystallite orientation on sputtering rate is shown in Fig. 4.20, in which 10 keV Kr+ ions at 50° incidence were used to sputter poly crystalline iron [76]. This ion etching may be useful to bring out grain structure but leads to loss of depth resolution... 

After the induction period (initial solution of hemihydrate t>r anhydrite), nuclcation of dihydrale occurs. Further crystal growth leads to a close-grained structure of dihydratc crystals which accounts for the rigidity of plaster Excess water is rcmove<.l by drying... 

The controlled grain structure allows forming an adherent protective oxide coating within days when placed in an electrowinning cell without the necessity of being preconditioned [13]. In sulfuric acid electrolytes, the introduction of cobalt ions into the solution reduces the anode overvoltage and the corrosion rate of lead. 

The first part of this paper will deal with the problem of fragmentation , i.e., with the mechanisms leading to the fine-grained structure. The second part will deal with the efficiency of different SPD-techniques to produce such structures. 

At low tin contents, the calcium initially precipitates rapidly as PbsCa in the same manner as in binary lead-calcium alloys. These alloys have a fine grain structure and quickly reach high hardness as discontinuous precipitation predominates. At higher tin contents, the mode of precipitation changes to a mixed discontinuous precipitation of PbsCa followed by a continuous precipitation reaction of Pb cSn Ca. These reactions lead to overageing of the precipitates and a decrease in mechanical properties. 

After annealing at 600°C for 1 hour in air, the formation of the LaCr04 phase with a small amount (up to 5wt%) of La2Cr06 secondary phase was confirmed by XRD [13]. Fine grain structure of LaCr04 phase can be seen in Fig. 1. Annealing of the films, at 800°C for 1 hour in air, then lead to the subsequent formation of the orthorhombic LaCr03 perovskite. The porosity of the LaCrOs film was a result of the two phase transitions from... 

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