Growth of micron-sized tubes of tungsten oxide

Micron-sized tubes of tungsten oxide have been grown in a catalyst-free reaction by heating tungsten wires in a humid argon flow. They were systematically characterized with different kinds of surface analysis means. The tubes were 1–5 μm in diameter and ∼10 μm in length. Depending on the fabrication conditions, they were composed of either monoclinic W18O49 or hexagonal tungsten trioxide (h-WO3). These tungsten oxide tubes are considered to have resulted from the lateral coalescence of tungsten oxide nanorods.