Comparison of the morphology and structure of WO₃ nanomaterials synthesized by a sol-gel method followed by calcination or hydrothermal treatment

Abstract

Tungsten (VI) oxide (WO₃) nanomaterials were synthesized by a sol-gel method using WCl₆ and C₂H₅OH as precursors followed by calcination or hydrothermal treatment. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) equipped with energy dispersive X-ray spectroscopy (EDX) were used to characterize the structure and morphology of the materials. There were significant differences between the WO₃ materials that were calcinated and those that were subjected to a hydrothermal process. The XRD results revealed that calcination temperatures of 300°C and 400°C gave hexagonal structures and temperatures of 500°C and 600°C gave monoclinic structures. The SEM images showed that an increase in calcination temperature led to a decrease in the WO₃ powder particle size. The TEM analysis showed that several nanoparticles agglomerated to form bigger clusters. The hydrothermal process produced hexagonal structures for holding times of 12, 16, and 20 h and monoclinic structures for a holding time of 24 h. The SEM results showed transparent rectangular particles which according to the TEM results originated from the aggregation of several nanotubes.

Keywords

WO₃ nanomaterial / sol-gel method / calcination / hydrothermal

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Acknowledgments

The authors gratefully acknowledge the financial and facility support from the Ministry of Research and Technology, Republic of Indonesia through Applied Research Incentive 2011(No. RT-2011-3832) and Sepuluh Nopember Institute of Technology (ITS)-Surabaya Indonesia through International Collaboration Research Grant 2011(No. 0750.042/I2.7/PM/2011).

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