In Situ Fourier Transform Infrared Characterization of the Effect of Electrical Fields on the Flame Synthesis of TiO₂Particles

Abstract

Electric fields facilitate flame synthesis of powders with precisely controlled size and composition. Fourier transform infrared (FTIR) spectroscopy is used for the first time to measure the effect of electric fields on the process temperature and composition during synthesis of titania powders by TiCl4 oxidation in a premixed methane−oxygen flame; flat electrodes apply a dc electric field to the flame. Emission and transmission FTIR spectra are taken at various flame heights. At each height, the FTIR measurements reveal that the particles and the gas have the same temperature. Electric fields modestly increase the flame temperature. The FTIR measured mole fractions of HCl are in good agreement with a mass balance indicating that all TiCl4 is converted to TiO2 by either direct hydrolysis or oxidation followed by hydrolysis of Cl2. The absorption spectrum of the TiO2 indicates that the particles scatter like a collection of ellipsoids. In the absence of electric fields, the particle mass concentration decreases by 20% from 0.3 to 1.3 cm above the burner by gas dilution. In the presence of electric fields, however, that concentration decreases by 70% over the same distance. Thus, FTIR spectroscopy is a powerful diagnostic tool that can provide in situ information of the temperature, composition, and particle characteristics in the adverse environment of electrically modified flames.

Independent Control of Metal Cluster and Ceramic Particle Characteristics During One-step Synthesis of Pt/TiO2

“…emission/transmission spectroscopy. 19 The spectrometer (Bomem Inc., Quebec, Canada Model MB157) operated over a spectral range of 6500 to 500 cm −1 with a resolution of 2 cm −1 and 4 mm infrared (IR) beam. 20 Transmission and emission (radiance) spectra were collected with a mercury-cadmium-tell (MCT) detector.…”

“…20 Average flame temperatures were estimated using the emission/transmission and the normalized radiance procedures for hot CO 2 . 19 The temperatures shown here were averages from both procedures representing the average flame temperature in the line of sight through the center of the flame. 20 For validation of the spray flame temperatures, measurements at some heights were carried out three times.…”

Flame-coating of titania particles with silica

“…2). Accordingly, the intensity of the peaks arising from bond vibrations 32 Figure 4 shows TEM images of silica/titania particles made with the unquenched flame: (a) pure SiO 2 , (b) 20 wt%, (c) 40 wt%, (d) 60 wt%, (e) 80 wt%, and (f) 100 wt% TiO 2 . For all compositions, the particles are mostly spherical with a low degree of agglomeration.…”

Nanofabrication of Metal Oxide Nanostructures in Aqueous Solutions

“…Additionally, the surface of TiO 2 should be covered with nano/microrelief structures to adsorb large amounts of dye, molecules and DNA for biomolecular sensors and dye-sensitized solar cells. TiO 2 nanoparticles have been prepared by flame synthesis 91,92 , ultrasonic irradiation 93,94 , chemical vapor synthesis 95 , sol-gel methods 79,[96][97][98][99][100] , sonochemical method 101 and liquid phase deposition of amorphous TiO 2 102-105 . High temperature in the treatment processes, however, causes aggregation of nanoparticles and decreased surface area.…”