Sintering of a bilayer. The bottom layer is a mixture of large (1micron) and small (0.5 micron) particles and sinters faster than the top layer.
publication:
X Liu, C L Martin, G Delette, J Laurencin, D Bouvard, T Delahaye. Microstructure of porous composite electrodes generated by the discrete element method. J. Power Sources 196, 2046 - 2054 (2011).