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In-Situ Laser Diagnostics for the Characterization of Nanoparticles Synthesized with the Reactive Spray Deposition Technology (RSDT)
EVANGELOS K. STEFANIDIS, Thomas A Ebaugh, Stoyan Bliznakov, Leonard Bonville, Francesco Carbone, Radenka Maric, University of Connecticut
Abstract Number: 98
Working Group: Nanoparticles and Materials Synthesis
Abstract
The Reactive Spray Deposition Technology (RSDT) is a single-step flame-based process used to manufacture highly active catalyst nanoparticles in a flow reactor and deposit them on a target substrate. The optimization of the RSDT methods can be performed by adjusting some operative parameters, such as the spray flowrate, to tailor the properties of the synthesized nanoparticles. The characterization of the nanoparticle products can be performed ex-situ at the end of the deposition process. However, the optimization of the process parameters and the ability to time stage the deposition process can benefit significantly from in-situ laser-based diagnostic capabilities. In this study, we use the second harmonic of a pulsed Nd:YAG laser with a wavelength of 532nm to illuminate a millimeter-sized measuring volume and collect the stimulated emission of light at an angle of approximately 45° from the incident beam through a series of optical elements into a spectrograph equipped with a fast gated and intensified CCD camera. Measurements were performed while synthesizing iridium oxide nanoparticles and two classes of platinum nanoparticles of different sizes, which have been already used to manufacture fuel cells. We obtained repeatable results independent of the laser illumination fluence in terms of both calibrated static Rayleigh scattering cross-section and particle Laser-Induced Incandescence (LII) signal. Data analysis allowed us to estimate the nanoparticle sizes and number concentrations at different positions in the reactor for the three considered deposition processes. The results are consistent with those of extra situ microscopy analyses. Additionally, we acquired inelastic Raman spectra to get information about the evolution of the chemical nature of the synthesized iridium oxide nanoparticles in the reactor.