Controllable preparation of tungsten/tungsten carbide nanowires or nanodots in nanostructured carbon with hollow macroporous core/mesoporous shell

摘要

Large scale tungsten nanowires and tungsten nanodots are prepared in a controllable way.The preparation is based on mechanisms of chemical vapor transportation and phase transformation during the reduction of ammonium metatungstate (AMT) in H2.The AMT is first encapsulated into the hollow core of nanostructured carbon with hollow macroporous core/mesoporous shell (NC-HMC/MS) and forms nanorods,which are the precursors of both tungsten nanowires and tungsten nanodots.Just by controlling H2 flow rate and heating rate in the reduction process,the AMT nanorods could turn into nanowires (under low rate condition) or nanodots (under high rate condition).Besides,via heat treatment at 1200 ℃,the as-obtained nano-sized tungsten could convert into W2C nanorods or WC nanodots respectively.Furthermore,the diameter of the as-obtained tungsten or tungsten carbide is confined within 50 nm by the NC-HMC/MS,and no agglomeration appears in the obtained nanomaterials.