Chemical characterization of Mg0.25Mn0.75-H(D) nanocomposites by Atom Probe Tomography (APT)

Abstract

Hydrogen (H)- and deuterium (D)-loaded Mg0.25Mn0.75 nanocomposites were prepared by a ball-milling process and Atom Probe Tomography (APT) analyses were carried out in order to investigate the resultant nanostructure. Due to the immiscibility of the Mg−Mn system, non-uniform and interconnected Mg-rich domains with a thickness of several to 10 nm formed in both of the H- and D-loaded composites. Such complex morphology could be attributed to the severe cold-rolling effects induced by ball-milling. The inhomogeneous distribution of D observed by the APT analysis is likely the result of severe lattice distortion and multiple defects, which are cold-rolling effects. While the detection of D in the D-loaded composite was hampered significantly by the desorption of D during specimen preparation, D remained around the boundary of the Mg-rich domains/Mn-rich matrix. This suggests that the modulated intermixing of immiscible Mg and Mn atoms together with the ball-milling effect results in a disordered atomic arrangement around the boundary. This is assumed to be one of the contributing factors in the destabilization of Mg hydride observed in our previous works.