The effect of processing parameters on the synthesis of tungsten oxide nanomaterials by a modified plasma arc gas condensation technique.

In the present study, tungsten oxide nanomaterials were synthesized by a modified plasma arc gas condensation technique. The effects of processing parameters (plasma current ranged from 70-90 A and chamber pressure ranged from 200-600 torr) on the preparation of tungsten oxide nanomaterials were investigated. X-ray diffraction results showed that all of the nanomaterials synthesized in the present study exhibited W5O14 phase. Field emission scanning electron microscopy and transmission electron microscopy examinations revealed that the tungsten oxide nanomaterials were equiaxed when prepared at a relatively low plasma current of 70 A, and turned into rod-like nanoparticles with increasing plasma current (80 or 90 A). Generally, the relative amount, diameter, and length of tungsten oxide nanorods increased with increasing plasma currents or chamber pressures. The aspect ratio of the as-prepared tungsten oxide nanorods reached a maximum of 12.7 when a plasma current of 90 A and a chamber pressure of 400 torr were used. A growth mechanism for tungsten oxide nanorods was proposed.