Insofar as platelets are 500 nm thi

Insofar as platelets are 500 nm thick, emerging spheres are larger than for needles where the diameter is only 200 nm. According to the model we proposed, the second step would consist in the rearrangement of large spheres into a compact assembly which avoid macroporosity. During the third step, densification occurs and is higher than for small spheres because the densification rate is an inverse function of the initial grain size. Finally, grain growth occurs.What appears is that neither the density of 93% nor the grain size of 3um are large. This result may be simply explained by our model which shows that we have a four-step sintering process: time is needed to make spheres, which is already an additional step compared to the second case related to grooved needles, and time must be again provided to have a dense assembly of spheres. Compared to the first case on nanospheres, these two last steps require additional time to occur. On top of all this, densification is slower because of the large sphere size. That is why there is not enough time to achieve complete sinteringand the relative density remains small as well as the grain size.