Morphological control of vertically self-aligned nanosheets formed on magnesium alloy by surfactant-free hydrothermal synthesis

Crystalline nanosheets were successfully formed on magnesium alloy AZ31 by a facile surfactant-free hydrothermal treatment using aqueous solution. The crystal structures and shapes of the nanosheets changed with the treatment temperature. On treatment at 120 degrees C, rosette-like structures made from curved nanosheets of crystalline Mg1-xAlx(OH)(2)(NO3)(x)center dot nH(2)O were formed. At 150 degrees C, plate-like nanosheets of crystalline Mg1-xAlx(OH)(2)(NO3)(x)center dot nH(2)O and Mg(OH)(2) were formed. Further increase in the treatment temperature to 180 degrees C yielded larger crystals with sharp edges. The crystallites were crystalline Mg(OH)(2) with a distinct plate-like shape with the edges preferentially directed out of the magnesium alloy. The formation mechanism of this morphology is also discussed.