Agglomerates and Aggregates: Number and Size of Primary Particles from in-situ Mass-Mobility Measurements

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Gas-borne nanoparticles generated at high temperatures undergo coagulation forming agglomerates (physically-bound particles) and aggregates (chemically- or sinter-bound particles). The structure of such particles influences their transport, light scattering, effective surface area and density. Real-time characterization of nanoparticles is necessary for continuous monitoring of aerosol manufacturing and airborne pollutant particle concentrations, but is still challenging [1]. Mostly ex-situ methods have been used to characterize such structures. Measuring only one particle property is not sufficient to characterize those structures. Here, zirconia nanoparticles are generated by a flame spray process and are characterized in almost real-time with their mass and mobility diameter. The mobility diameter is measured by a differential mobility analyser (DMA) and the mass by an aerosol particle mass analyser (APM) to determine the mass-mobility exponent (Dfm). Additionally, a new relation [5] between average primary particle diameter, aggregate/agglomerate mass and mobility diameter is used to extract the primary particle diameter or SSA from these data. The effect of oxygen flow (Figure 2) and precursor feed rate as well as precursor concentration on agglomerate/aggregate structure and primary particle diameter are investigated. Good agreement between ex-situ nitrogen adsorption (BET), transmission electron microscopy (TEM) and on-line DMA-APM is found for all investigated process conditions.

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Journal: TechConnect Briefs
Volume: 1, Nanotechnology 2012: Advanced Materials, CNTs, Particles, Films and Composites (Volume 1)
Published: June 18, 2012
Pages: 1 - 4
Industry sector: Advanced Materials & Manufacturing
Topic: Materials Characterization & Imaging
ISBN: 978-1-4665-6274-5