High-Resolution Differential Mobility Analysis (HR-DMA) of sub-10nm Nanoparticles Synthesized by the Reactive Spray Deposition Technology
FARNAZ KHOSRAVI, Evangelos K. Stefanidis, Zhiqiao Zeng, Stoyan Bliznakov, Leonard J. Bonville, Radenka Maric, Francesco Carbone,
University of Connecticut Abstract Number: 238
Working Group: Nanoparticles and Materials Synthesis
AbstractThe Reactive Spray Deposition Technology (RSDT) is a technique that enables the deposition of flame-synthesized nanoparticles with sizes smaller than 10nm on proton conductive membranes to fabricate Membrane Electrode Assemblies (MEAs). The Size Distribution Function (SDF) of the synthesized nanoparticles can affect the performance of the manufactured electrodes. Therefore, in this study, we apply High-Resolution Differential Mobility Analysis (HR-DMA) to measure the SDFs of the platinum (Pt) nanoparticles synthesized by two RSDT turbulent jet non-premixed flames. A thin-walled tubular probe equipped with a micron-sized orifice is used to sample and quickly dilute the RSDT flame products at different distances from the fuel nozzle, L. The samples are diluted in pure nitrogen flowing in the tube and transferred to a Half-Mini HR-DMA to implement their size classification before counting by a Faraday Cup Electrometer. The measurements are repeated using a sampling orifice diameter of both 0.25mm and 0.15mm to assess the effect of dilution on the coagulation and charge redistribution dynamics occurring in the sampling system. Measurements performed in equivalent flames deprived of the platinum precursor enable the distinction between platinum nanoparticles and small hydrocarbon chem-ions. Results are consistent with recent literature data reporting the nanoparticle SDFs at L=150mm as obtained by deposition and microscopy analysis and the average nanoparticle diameter across the flame length as measured by in-situ laser diagnostics. The HR-DMA results demonstrate that the platinum nanoparticles have bimodal SDF, with the first mode located at around 1nm, and the second mode exhibiting a lognormal distribution with a constant relative width. The center of the second mode shifts from 4.6nm to 6.4nm at increasing distances from the fuel nozzle (L), from 150mm to 300mm, as the nanoparticles coagulate and age within the flame.
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