Electrodeposited Al mesocrystal with high thermal stability and high hardness

Mesocrystal, composed of same-oriented nanocrystals separated by organics, is a promising structure for superior chemical and mechanical properties, in which the high density of nanocrystal-organic interfaces plays a crucial role. The stability of the interfaces determines the service temperature and strength of the material. Here, we synthesized aluminum mesocrystal using electrodeposition in ionic liquids with methyl nicotinate additive and investigated its thermal and mechanical stability. In contrast to the low stability of nanograined metals and nanoporous metals with comparable grain sizes, the Al mesocrystal is found to be stable up to 320°C (0.63 Tm, Tm: the melting point) and has a recorded high hardness of 2.27 GPa. The high stability originates from the suppression of migration and free diffusion of the interfaces.