the powder has a large surface area in comparison with a similar olume of bulk solid. We can say that a small particle which is assumed to be a sphere, has surface properties that are different from those of a bulk solid because it has a large surface-to-volume ratio and because its surface has a small radius of curvature In sintering, we see the effect of this cur first when grains(viewed as spheres) join together. This is the curvature of the initial particle surfa Then the GBs will move: this is the same effect but for internal surfaces nd leads to grain growth during sintering