Large-scale synthesis of tungsten single-crystal microtubes via vapor-deposition process

Tungsten microtube arrays were fabricated with a large quantity by using the volatile tungsten oxide hydrate, WO2(OH)2, as tungsten vapor source in the chemical vapor-deposition process. The synthesized tungsten microtubes have a pencil-like shape, with a pyramid root and a hexagonal trunk of a uniform size along the axial direction. The size and the length of the microtubes exhibited to be linearly related to the growth duration, however, the thickness of the tube wall appeared to be not affected by the growth duration. The investigation revealed that the hexagonal microtube was transformed from a hexagonal microrod by stretching out the hexagonal edges of the solid growth end during the vapor growth process.