Materials Engineering Department
BS in Materials Engineering
Jean L. Lee
The process of aquarefining is an environmentally-friendly method for producing pure lead products that exhibit particularly low density. To observe the microstructures of these low-density forms of lead, scanning electron microscopy (SEM) was employed to examine aquarefined lead samples produced under three batches of processing conditions. Due to aquarefined lead's tendency to collapse under its own weight, careful measures were taken during transport and handling to avoid damaging the samples. Three types of microstructures were observed and correlated to changes in processing conditions: octahedron crystallites, microscales, and dendrites. Energy-dispersive x-ray spectrometry (EDS) was used to quantify the amount of oxygen in each of these microstructures, as the type of lead microstructure appears to vary with the amount of oxygen present. For each batch of processing conditions, the density of the samples produced under those conditions was measured using the Archimedes method. The density of the samples ranged from 1.30 to 3.62 g/cm3, which is significantly less than that of conventional lead (11.30 g/cm3). The decrease in density appears to be due to the formation of thinner dendrites and of hydrogen-filled pores during the aquarefining process. From our results, lead and free acid concentrations were determined as the most critical factors in determining the microstructure of the aquarefined lead, with applied current and temperature of secondary importance.
Available for download on Wednesday, June 15, 2022