When the dissolution rate of A is considerably higher than that of B, and the product layer forms on the surface of particle B (Fig. 7(b)), then another mechanism operates. The product layer prevents the dissolution of B. A large amount of A dissolves in the molten salt before the dissolution of B, diffuses through the molten salt, reaches the surface of particle B, and reacts with B. The reaction proceeds by the diffusion of A from the interface of the molten salt/product layer to the interface of product layer/particle B and/or by the diffusion of B in the reverse direction, resulting in an increase in the thickness of the product layer. Finally, reactants A and B are completely consumed and the product particle with almost the same shape as that of particle B are obtained (solution-diffusion process: mechanism 2). Sometimes, this mechanism is called templating (Yang et al. 2001).