Multiple-diffusion flame synthesis of pure anatase and carbon-coated titanium dioxide nanoparticles

摘要

A multi-element diffusion flame burner (MEDB) is useful in the study of flame synthesis of nanomaterials. Here, the growth of pure anatase and carbon-coated titanium dioxide (TiO_2) using an MEDB is demonstrated. Hydrogen (H_2), oxygen (O_2), and argon (Ar) are utilized to establish the flame, whereas titanium tetraisopropoxide is used as the precursor for TiO_2. The nanoparticles are characterized using high-resolution transmission electron microscopy, with elemental mapping (of C, O, and Ti), X-ray diffraction, Raman spectroscopy, and thermogravimetric analysis. The growth of pure anatase TiO_2 nanoparticles occurs when Ar and H_2 are used as the precursor carrier gas, while the growth of carbon-coated nanoparticles ensues when Ar and ethylene (C_2H_4) are used as the precursor carrier gas. A uniform coating of 3-5 nm of carbon is observed around TiO_2 particles. The growth of highly crystalline TiO_2 nanoparticles is dependent on the gas flow rate of the precursor carrier and amorphous particles are observed at high flow rates. Carbon coating occurs only on crystalline nanoparticles, suggesting a possible growth mechanism of carbon-coated TiO_2 nanoparticles.