Gas-phase methods, such as flame reactors (depicted below), are used routinely for commercial synthesis of nanostructured particles (e.g. fumed silica, pigmentary titania, carbon black, Ni) as well as for advanced materials (e.g. photocatalysts, nanofluids and biomaterials). We are examing the evolution of size and structure of such flame-made particles that determine their optical and mechanical properties are characterized online by differential mobility and aerosol particle mass analyzers combined with condensation particle counters. Uniquely, we have developed a data inversion to determine two-dimensional size distribution functions for these aggregates, which better describe morphological distributions than traditional one-dimensional measurements.
In addition to the current differential mobility analysis-aerosol particle mass analysis approach we are utilizing, in the past we have developed a Brownian Dynamics (Mean First Passage Time) calculation approach as well as classical trajectory calculations to determine collision rate coefficients/collision kernels for particles of arbitrary shape, at any temperature and pressure, non-spherical particles with ions, and additionally developed and tested equations for the drag coefficient of non-spherical, aggregated particles at arbitrary Knudsen numbers. Activities in our laboratory from 2010-2015 were heavily devoted to these efforts, and such studies are still on-going in our group. Please see our publications page where a number of references describing this work are noted, including those listed below.
Yang H. & Hogan C. J. (2017) Collision Rate Coefficient for Charged Dust Grains in the Presence of Linear Shear. Physical Review E. 96: 032911. 10.1103/PhysRevE.00.002900
Gopalakrishnan R., McMurry P. H., & Hogan C. J. (2015) The Bipolar Diffusion Charging of Nanoparticles: A Review and Development of Approaches for Non-spherical Particles. Aerosol Sci. Technol. 49:1181–1194. 10.1080/02786826.2015.1109053
Gopalakrishnan R., McMurry P. H., & Hogan C. J. (2015). The Electrical Mobilities and Scalar Friction Factors of Modest-to-High Aspect Ratio Particles in the Transition Regime. J. Aerosol Sci. 82:24-39. 10.1016/j.jaerosci.2015.01.001
Thajudeen T., Deshmukh, S., & Hogan C. J. (2015) Langevin Simulation of Aggregate Formation in the Transition Regime. Aerosol Science & Technology. 49:115–125. 10.1080/02786826.2015.1008971
Thajudeen T., Jeon S., & Hogan C. J. (2015). The Mobility of Flame Synthesized Aggregates/Agglomerates in the Transition Regime. J. Aerosol Sci. 80: 45-57. 10.1016/j.jaerosci.2014.11.003
Gopalakrishnan R., Thajudeen T., Ouyang H., & Hogan C. J. (2013). The Unipolar Diffusion Charging of Arbitrary Shaped Particles. J. Aerosol Sci. 64:60-80. 10.1016/j.jaerosci.2013.06.002
Gopalakrishnan R., Meredith M. R., Larriba-Andaluz C., & Hogan C. J. (2013). Brownian Dynamics Determination of the Bipolar Steady State Charge Distribution on Spheres and Non-spheres in the Transition Regime. J. Aerosol Sci. 63:126-145. 10.1016/j.jaerosci.2013.04.007
Ouyang H., Gopalakrishnan R., & Hogan C. J. (2012). Nanoparticle Collisions in the Gas Phase in the Presence of Singular Contact Potentials. The Journal of Chemical Physics. 137:064316. 10.1063/1.4742064
Thajudeen T., Gopalakrishnan R., & Hogan C. J. (2012). The Collision Rate of Non-spherical Particles and Aggregates for all Diffusive Knudsen Numbers. Aerosol Sci. Technol. 46:1174-1186. 10.1080/02786826.2012.701353
Zhang C., Thajudeen T., Larriba C., Schwartzentruber T. E., & Hogan C. J. (2012). Determination of the Scalar Friction Factor for Non-Spherical Particles and Aggregates Across the Entire Knudsen Number Range by Direct Simulation Monte Carlo (DSMC). Aerosol Sci. Technol. 46:1065-1078. 10.1080/02786826.2012.690543
Gopalakrishnan R. & Hogan C. J. (2012). Coulomb-Influenced Collisions in Aerosols and Dusty Plasmas. Phys. Rev. E. 85: 026410. 10.1103/PhysRevE.85.026410
Gopalakrishnan R., Thajudeen T., & Hogan C. J. (2011). Collision Limited Reaction Rates for Arbitrarily Shaped Particles Across the Entire Diffusive Knudsen Number Range. The Journal of Chemical Physics. 135:054302. 10.1063/1.3617251
Gopalakrishnan R. & Hogan C. J. (2011). Determination of the Transition Regime Collision Kernel from Mean First Passage Times. Aerosol Science and Technology. 45:1499-1509. 10.1080/02786826.2011.601775