Templated one-step catalytic fabrication of uniform diameter MgxBy nanostructures

Abstract

Direct fabrication of MgxBy nanostructures is achieved by employing Ni–Mg incorporated MCM-41 in the Hybrid Physical–Chemical Vapor Deposition (HPCVD) reaction. Different reaction conditions are tested to optimize the fabrication process. TEM analysis shows the fabrication of MgxBy nanostructures starting at a reaction temperature of 600 °C, and the yield of the nanostructures increases with the reaction temperature. The as-synthesized MgxBy nanostructures have the diameters in the range of 3–5 nm, which do not increase with the reaction temperature. EELS analysis of the template removed nanostructures confirms the existence of B and Mg with minimal contamination of Si and O. NEXAFS and Raman spectroscopy analyses suggested a concentric layered structure for our as-synthesized MgxBy nanotube/nanowire, which is in good agreement with the theoretical calculations. Ni K-edge XAS indicates that the formation of MgNi alloy particles is important for the Vapor–Liquid–Solid (VLS) growth of MgxBy nanostructures with fine diameters, and the presence of Mg vapor not just Mg in the catalyst is crucial for the formation of Ni–Mg clusters. Physical templating by MCM-41 might also help to confine the diameter of the nanostructures. DC magnetization measurements indicate possible superconductive behaviors in the as-synthesized sample.