ACID-ZINC REACTION PREDICTABLY AFFECTS PARTICLE MORPHOLOGY

The results in this investigation indicate that change of particle morphology as a chemical reaction progresses can be separated into two stages and that each can be predictably described by particle morphological analysis. The first stage involves the smoothing out of peaks and corners of the particle. The overall tendency of this stage is to attain a more regular geometry. In the second stage, new points of attack at the smoothed particle surface begin to develop and continue to develop as the reaction progresses. Both of these two stages of development can be reflected in a simple parameter which is the sum of the Fourier coefficients describing the particle shape. At the first stage this sum decreases, whereas at the second stage it increases again. Those more vulnerable points that are attacked could depend on the surface fine structure, positions of crystal defects and impurities within, rather than the shape of the particle. Although the first stage begins developing at the moment the chemical reaction is started, the second stage might occur at a much later time or be completely missing, depending on particle surface characteristics. In some cases the two stages may overlap to a certain extent but they are still separated far enough to make practical predictions meaningful. The above conclusions are drawn from studies of particles reacting in a homogeneous surrounding medium. For particles reacting in non-homogeneous surrounding, further investigations are necessary. © 1979.