UBC Theses and Dissertations
Strain potentials of copper wire in potasium nitrate solutions Hoskins, Alfred Donald
The effect of uni-directional stress on the electrode potential of copper in aerated potassium nitrate solutions was studied. The influence of the variables time, temperature, concentration, magnitude of stress, mechanical condition of the metal, and pH was considered. The potential difference between two size #22 B & S copper wires was continuously recorded on a type G Speedomax automatic recorder. A balance pan was attached to one of the wires to which weights were added and the change in the potential difference between the two wires from the pre-stress potential difference was taken as the strain potential. At least four runs, using fresh pairs of wires for each run, were carried out to illustrate each specific point and to show the results have statistical significance and are reproducible. The following results were obtained: (A) Electronegative strain potentials have been obtained for copper metal in aerated potassium nitrate solution; these changes achieve a maximum at the instant of stressing and then decay with a negative acceleration with time. After an initial period of time, the strain potential decayed logarithmically with time. The magnitude of the electronegative strain potential for a given stress increased exponentially with the reciprocal of the absolute temperature and remained essentially unchanged for concentration changes ranging from 0.005N to 0.500N. (B) Experimental evidence was obtained to support the postulate that strain potentials of copper metal in aerated potassium nitrate solution and their time dependence parallel film rupture; the effect of the change in internal energy due to plastic deformation cannot be ignored.
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