Structural and mechanical properties of magnesium aluminate nanoceramics under high pressure.

Nanoceramics may have different structural and physical properties compared to their coarse-grained counterparts. Here, we report the high-pressure study of micro- and nano-crystalline MgAl₂O₄ in order to examine the effect of particle size on the structural stability. A reversible pressure-induced phase transition (cubic to tetragonal) is observed in MgAl₂O₄ nanocrystals under non-hydrostatic pressure at room temperature, in contrast to the previously reported structural transition of MgAl₂O₄ at high pressure and high temperature. It is also found that the compressed MgAl₂O₄ microcrystals do not fracture further below 60 nm, suggesting a plastic deformation mechanism transition. MgAl₂O₄ with a grain size above ∼60 nm exhibits normal cracking behaviors, but shows metal-like plastic deformation behaviors below this critical size. It is implied that combined ductility and strength can be achieved in nanoceramic MgAl₂O₄. [ABSTRACT FROM AUTHOR]