Dannehl, M.

Fissan, H.

Goertz, V.

Mertler, M.

Nirschl, H.

Pui, D.

Sachweh, B.

Stenger, F.

Wang, J.

KITopen

Online Characterisation of Nanoparticle Morphology tailored by Gas-dynamically Induced Particle Synthesis  M. Dannehl1, F. Stenger1, M. Mertler2, B. Sachweh2, V. Goertz3, H. Nirschl3, J. Wang4, D. Pui4 and H. Fissan5   1Evonik Degussa GmbH, Rodenbacher Chaussee 4, 63457 Hanau-Wolfgang, Germany 2BASF SE, Fine Particle Technology and Particle Characterization, 67056 Ludwigshafen, Germany 3Karlsruher Institut für Technologie (KIT),Institut f. Mechanische Verfahrenstechnik u. Mechanik, Universität Karlsruhe (TH), 76131 Karlsruhe, Germany 4Particle Technology Laboratory, Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, 55455 5Institute of Energy and Environmental Technology (IUTA), Bhersheimer Straße 60, 47229 Duisburg, Germany   Keywords: Nano-Particles, UNPA, Particle Morphology Characterisation, SiO2, Shock-wave Flow Reactor   The variety of processes for gas-phase nano-particle synthesis can be reduced down to just a small number, if high mass throughputs are desired (flame reactors, hot wall, reactors plasma reactors).  An innovative concept of high throughput gas phase particle reactor has been proposed (Dannehl et al., 2007). Both, initiation of chemical reaction, and quenching of high-temperature gas flow are realized by gas-dynamic shocks in a reactor with two supersonic nozzles. (Fig. 1). The quenching of the high-temperature particle loaded gas flow is achieved by accelerating the flow from subsonic to supersonic speed which decreases the static temperature blow the sinter temperature of the particles. Because of a homogeneous flow field, an adjustable residence time and high heating and quenching rates tunable size distribution and aggregation is achieved (Grzona et. al., 2009, Goertz et al. 2010). Therefore this method is a potent alternative when nano-scaled mono-dispersed material manufacturing is demanded.   injectorfirst nozzleshockreaction volume second nozzlequenchingprecursor supplywatersupplyparticle formation & growthhot gassupply  Fig. 1. Gas-dynamically Induced Particle Synthesis   For process control of such a reactor fast and online measurement for nanoparticles, agglomerates, e.g. particle morphology is required. Most of the current aerosol instruments are designed for spherical particles. Therefore, there is a need for instruments capable of fast and online measurement of gas-borne nanoparticle agglomerates.  Recently, a new measurement device for online characterization of gas-borne nanoparticle agglomerates has been developed (Pui et al. 2009). UNPA (Universal Nanoparticle Analyzer) utilizes Differential Mobility Analyzer (DMA), Condensation Particle Counter (CPC) and Nanoparticle Surface Area Monitor (NSAM) to characterize airborne nanoparticle morphology and measure the number, surface area and volume distributions of airborne nanoparticles. The key parameter measured is the UNPA sensitivity, which is defined as the current (fA) measured by the NSAM divided by the number concentration measured (#/cm3) S = I/N (fA cm3). Former experimental data have shown that the UNPA sensitivity S depends on the particle morphology. S is larger for loose agglomerates than for spheres at a fixed mobility diameter.  Experimental UNPA sensitivity measurements in the particles/gas flow behind the quenching show suitable results for the online characterisation of the particle morphology (Fig. 2) under different process conditions.   Fig 1. UNPA sensitivity for process parameters A  This work is supported by the German Research Foundation under grant PAK 75/2 “Gasdynamically initiated particles production”.  Dannehl, M. et al. Nanoparticle Synthesis by Gas-dynamically Induced Heating and Quenching. EAC 2007, Salzburg, Abstract T09A039 Grzona, A. et. al. (2007). Proceedings 26th International Symposium on Shock Waves (ISSW26), 15.-20. Juli 2007, Göttingen.  Goertz, V. et al. Experimental Study of Gasdynamically Induced Nanoparticle Synthesis by Use of Adapted Sampling Probes. submitted in Chemical Engineering Science, 2010. Shin, W-G, Wang, J., Mertler, M., Sachweh, B., Fissan, H., Pui, D.Y.H. (2009), J. Nanoparticle Research. 11, 163 – 173.   

Online Characterisation of Nanoparticle Morphology tailored by Gas-dynamically Induced Particle Synthesis

https://publikationen.bibliothek.kit.edu/1000023010/1711119

Online Characterisation of Nanoparticle Morphology tailored by Gas-dynamically Induced Particle Synthesis

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