my naometer sized zirconia with tetragonal phase (t), readily transformed to monoclinic phase (m) upon grinding in a mortar. After coating with foreign oxide, I found it did not undergo t-m phase transformation. Since it belongs to martensitic phase transformation, I think I need to know something about martensitic nucleation for a meaningful discussion on my experimental results. Unfortunately, most work on this topic was based on micrometersized samples that will be very different from nano-materials.

I wonder, for nanomaterials that experience martensitic phase transformation, where nucleation of a martensite starts, at surface or inside a grain? And Why?

Anyone could answer me or provide some suggestions? i would appreciate it very much.