DRAGGING OF SMALL OXIDE PARTICLES BY MIGRATING GRAIN BOUNDARIES IN COPPER

Grain boundaries, introduced into a copper single crystal by indenting and annealing the crystal, are shown to drag certain small (4000 Å diameter) oxide particles with them when they migrate. GeO2 and B2O3 particles are dragged rapidly (with speeds up to 1 μ/min) at temperatures between 650 and 1050°C SiO2 particles are rather less mobile, and Al2O3 particles are, within the accuracy of our experiments, immobile. Measurements of the distance through which particles are dragged as a function of time and temperature yield activation energies for the dragging process, and mobilities for each sort of particle. Fluid particles, like B2O3, behave roughly like bubbles. But more solid particles, like SiO2, are much less mobile, and their mobility is controlled by transport, or self-diffusion, within the particles. © 1968.