Self-growth of micro- and nano-structured Mg(OH)2 on electrochemically anodised Mg–Li alloy surface

Abstract

Formation of Mg(OH)2 nanowires and their assemblies with sphere-shaped, echinus-shaped and nest-like micro-structures on a Mg-Li alloy surface was successfully demonstrated. Mg(OH)2 nanowires were formed on the alloy surface via a self-growth process, after the alloy was electrooxidised in NaCl solution and the oxidation products were removed. The nanowires were characterised by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Infrared spectroscopy. The nanowires have hexagonal rod-like or brush-like morphology and are poorly crystallised. Pre-anodisation and the presence of Li in the alloy are key factors for the nanowire growth, which likely proceeds via a dissolution–precipitation mechanism. The roles of Li can be attributed to the prohibition of the formation of passivation film on the alloy surface and the acceleration of the formation of OH− anions through hydrogen-evolution reaction.