American Chemical Society
ic2005858_si_001.pdf (1.58 MB)

Morphological Evolution of (NH4)0.5V2O5·mH2O Fibers into Belts, Triangles, and Rings

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journal contribution
posted on 2011-08-15, 00:00 authored by Gujjarahalli Thimmanna Chandrappa, Pallellappa Chithaiah, Siddaramanna Ashoka, Jacques Livage
In this contribution, single-crystalline (NH4)0.5V2O5·mH2O xerogels made of belts, rings, triangles, and ovals have been synthesized using a surfactant-free hydrothermal method. The analytical techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED) have been used to characterize the morphology, composition, and structure of the as-prepared products. On the basis of SEM and TEM observations, we suggested that the as-prepared (NH4)0.5V2O5·mH2O rings, triangles, and ovals have been formed by connecting two ends of the vanadium oxide sheet made of edge and corner sharing VO5 square pyramids. The as-prepared (NH4)0.5V2O5·mH2O nanobelts are up to several hundreds of micrometers long, 402–551 nm wide, and 235–305 nm thick. The thickness and width of the rings are respectively ∼454 nm and ∼1 μm. Triangles with three unequal sides having a thickness of ∼143 nm and a width of ∼1 μm were also formed. The crystalline orthorhombic phase of shcherbianite V2O5 was obtained on calcination of (NH4)0.5V2O5·mH2O at 350 °C for 2 h. The SEM image of this V2O5 product retains the parent morphology of the preheated compound. A possible reaction mechanism and the growth process involved in the formation of belts/rings/triangles and ovallike microstructures are discussed.