Abstract
Conventional models for initial stage sintering consider sintering to occur between two single crystal spheres, although most powder particles are polycrystalline in reality. The conventional Coble model is modified to take into account multiple grain boundaries intersecting a neck in sintering between polycrystalline particles. The exponents N and M in the rate equation (x/R)^N α (t/ R^M), for polycrystals were found to be 4 and 2, respectively, in contrast to 6 and 4 in single crystals; here x, R and t are the neck radius, particle radius and time, respectively. In addition there is a 1/d^2 dependence, where d is the grain size. Analysis reveals that initial stage sintering will be enhanced in polycrystalline particles when the neck is large and there are a large number of grains within a particle. Accompanying experiments on close packed irregular 2D arrays of polycrystalline zirconia spheres showed that the neck growth rate was higher for the particles containing a large number of grains, compared to those with only a few grains.
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