Two types of ZnO-tubular nanostructures fabricated by stepped gas-phase reaction

Two types of zinc oxide (ZnO)-tubular nanostructures have been fabricated by stepped gas-phase reaction of a mixture of Zn–ZnO powders. Tubular structures of Type I vaporized from the top of ZnO nanorods with several hundreds nanometer in diameter. Tubular structures of Type II-coalesced ZnO nanowires with 2–4 μm in diameter. The formation of these two types of ZnO-tubular nanostructures is governed by different reaction conditions such as temperature, atmosphere, pressure, etc., and their growth mechanisms are discussed in detail.