High-Resolution Differential Mobility Analysis (HR-DMA) of Nickel Oxide Nanoparticles Synthesized in Flat Premixed Droplet Seeded Flame (FPDSF)
Farnaz Khosravi, Owen Fuhr, Dylan Errico, Mahmoud Ashour, Christian Bjork, FRANCESCO CARBONE,
University of Connecticut Abstract Number: 236
Working Group: Nanoparticles and Materials Synthesis
AbstractA Flat Premixed Droplet Seeded Flame (FPDSF) facility is used to synthesize Nickel Oxide (NiO) nanoparticles smaller than 10 nm from a monodisperse aerosol of a nickel (II) nitrate water solution. The FPDSF facility is composed of a Berglund-Liu-type Vibrating Orifice Aerosol Generator (VOAG) which produces monodisperse micron-scale droplets of the nanoparticle precursor solution. The aerosol is mixed with the gaseous combustion reactants within a 3D-printed burner coupling device which conveys the aerosol to the burner nozzle where a honeycomb stabilizes the desired FPDSF. NiO nanoparticles are synthesized as a result of the fast oxidative pyrolysis of the nickel nitrate. This work presents the Size Distribution Functions (SDFs) of the naturally charged fraction of the synthesized NiO nanoparticles as measured by High-Resolution Differential Mobility Analysis (HR-DMA) at several Heights Above the Burner (HAB), from 15 mm to 40 mm. The flame products are sampled continuously through a micron-sized orifice (whose diameter is either 0.25mm or 0.36mm) drilled in the middle of a thin-walled (0.127mm) tubular probe. They are diluted rapidly in 30slpm of pure nitrogen crossing the probe, before being conveyed to the inlet slit of a Half-Mini HR-DMA. A Faraday Cup Electrometer counts the size-classified charged materials that exit the HR-DMA and whose mobility diameter is selected by stepping the HR-DMA control voltage. The results show that the synthesized nanoparticles emerge from the blue flame front with a bimodal SDF at HAB lower than 15mm. Interestingly, the second mode of SDF disappears progressively at increasing HABs, resulting in an approximately lognormal SDF centered near 3.5nm. The SDF center shifts to only slightly larger mobility diameters as nanoparticles age and grow in the flame. Additional measurements are being performed using a diffusion charging approach to quantify the nanoparticles that are neutral within the flame.