(737b) Adjustment and Online Determination of Primary Particle Size in Transferred Arc Synthesis
AIChE Annual Meeting
Thursday, November 7, 2013 - 3:50pm to 4:15pm
Metallic nanomaterials are used in a large number of applications. Their production however still challenges scientists and engineers all over the world, since most processes are not capable of scaling-up the production rate of metal nanoparticles. Some are inefficient in terms of energy or material consumption or too expensive to scale-up, others produce micron sized particles instead of nanoparticles, when the production rate is increased. A transferred arc process has been found suitable for scaling-up the production rate of metal nanoparticles (Stein et al. 2013). However, this process as well tends to fluctuate in terms of particle size, due to changing process parameters (e.g. electrode gap), when the production rate is increased. Traditional characterization devices for particle size (XRD, BET) are not capable to determine those fluctuations as they present a mean particle size of the collected powder. Therefore a novel characterization system is set up to determine the production rate, specific electricity consumption, mobility size and an estimated primary particle size directly online at the process.
A transferred arc process is optimized to increase the production rate (> 2 g/h) and thereby minimize the specific energy consumption (< 500 kWh/kg) of copper nanoparticles. The optimization has been done by an adjustment of the experimental setup to reduce particle losses and give a better size control of particle size. A carrier gas composition of argon and nitrogen is thereby found to be the most relevant parameter for particle size control. Copper particles between 15 – 90 nm can be adjusted. An online measurement system containing a Tapered Element Oscillating Microbalance (TEOM), an Electrical Low Pressure Impactor (ELPI) and a Scanning Mobility Particle Sizer (SMPS) is used to characterize the synthesized particles. The parallel measurement of ELPI and SMPS allows determining the effective density and fractal dimension of the formed agglomerates (Virtanen et al. 2004), giving the opportunity to calculate the primary particle size in the agglomerates online. The effective density is thereby the fitting parameter between the number size distributions based on mobility (SMPS) and aerodynamic diameter (ELPI). An equation is formed, with the knowledge of the BET diameter, which allows calculating the fractal dimension directly from the fitted effective density. Since the effective density and fractal dimension is needed to calculate the primary particle size from the mobility diameter (Sorensen 2011), it is possible to calculate the primary particle size online.
The research leading to these results has received funding from the European Union's Seventh Framework Program under grant agreement N° 280765 (BUONAPART-E).
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Stein M, Kiesler D, Kruis F E (2013) Effect of carrier gas composition on transferred arc metal nanoparticle synthesis. J Nanopart Res 15:1400
Virtanen A, Ristimäki J, Keskinen J (2004) Method for measuring effective density and fractal dimension of aerosol agglomerates. Aerosol Sci. Technol 38:437–446