Ultrasonic-assisted preparation of metastable hexagonal MoO3 nanorods and their transformation to microbelts

Metastable hexagonal h-MoO3 nanorods were synthesized by a simple sonochemical method, and then were transformed into thermodynamically stable a-MoO3 microbelts by calcination. The obtained samples were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). It was found that the as-prepared h-MoO3 nanorods were of 0.2–1.2 μm in width and 1-6 μm in length. A possible formation and growth mechanism of hexagonal MoO3 nanorods is proposed, in which ultrasound plays a crucial role and cannot be ignored. Moreover, the effect of temperature on the transformation process by calcination is investigated and a possible growth process of microbelts is also discussed.