Shape-Controlled Growth of MgH₂/Mg Nano/Microstructures Via Hydriding Chemical Vapor Deposition

In this paper, we report the shape-controlled growth of MgH 2 /Mg nano/microstructures via hydriding chemical vapor deposition (HCVD), wherein magnesium vapor was deposited on a substrate at different temperatures ranging from 225 to 600 °C and H 2 pressures ranging from 1 to 4 MPa. The products obtained after heating for 7, 13, and 20 h were identified by X-ray diffraction and observed by scanning electron microscopy. The shape, size, and purity of the products strongly depended on the experimental conditions, which were classified according to the pressure−temperature equilibrium diagram for MgH 2 . The diagram showed six distinct areas for the products MgH 2 and/or Mg having the following structures: fine and coarse powder, dendrite, root-like structure, straight and curved fibers, irregular bulk structure, and hexagonal and spherical structures. The diagram can be used quite effectively for controlling the shape of MgH 2 and/or Mg, and this may lay the foundation for the mass production of nano/microsized MgH 2 /Mg for use in hydrogen storage or batteries.