Insight of Iron Whisker Sticking Mechanism from Iron Atom Diffusion and Calculation of Solid Bridge Radius

The sticking temperatures of three kinds of iron particles with different morphologies were examined at an inert atmosphere in a fluidized bed, indicating that the sticking temperature of a fresh reduction iron particle was lower than that of reagent iron particles, and that the sticking temperature of an iron particle with a whisker was lower than that of an iron particle without a whisker. Cavity defects on the surface of an iron particle with different morphologies were examined by positron annihilation spectroscopy. The results indicated that cavity defects on the surface of an iron particle with an iron whisker were higher than with others, which resulted in an easier surface diffusion of Fe atoms. From the calculation of a critical solid bridge radius, the critical solid bridge radius lowered with the decreasing of gas velocity and particle size. And when an instantaneous solid bridge radius was bigger than a critical solid bridge radius, sticking of the iron particle happened. The iron whisker made the surface diffusion rate of Fe atoms occur more quickly, which resulted in a faster growth rate of the instantaneous solid bridge radius. Therefore, the iron whisker supported the sticking.