Kinetics of sub-2 nm TiO2 particle formation in an aerosol reactor during thermal decomposition of titanium tetraisopropoxide
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Particle size distribution measurements from differential mobility analyzers (DMAs) can be utilized to study particle formation mechanisms. However, knowledge on the initial stages of particle formation is incomplete, since in conventional DMAs, the Brownian broadening effect limits their ability to measure sub-2 nm-sized particles. Previous studies have demonstrated the capability of high-flow DMAs, such as the Half Mini DMAs, to measure sub-2 nm particles with significantly higher resolutions than conventional DMAs. A Half Mini DMA was applied to study the kinetics of sub-2 nm TiO2 nanoparticle formation in a furnace aerosol reactor, through the thermal decomposition of titanium tetraisopropoxide (TTIP). The influence of parameters such as reaction temperature, residence time, precursor concentration, and the introduction of bipolar charges on sub-2 nm particle size distributions were studied. A first order reaction rate derived from the dependence of size distributions on reaction temperature matched well with existing literature data. The change in precursor residence time and precursor concentration altered the size distributions correspondingly, indicating the occurrence of TTIP thermal decomposition. The introduction of bipolar charges in aerosol reactors enhanced the consumption of reactants, possibly due to ion-induced nucleation and induced dipole effects.
KeywordsSub-2 nm particles Differential mobility analyzer (DMA) Size distribution Furnace aerosol reactor Titanium tetraisopropoxide (TTIP) Particle formation and growth
The authors thank Professor Michel Attoui from University Paris Est Creteil for his ideas and kind help on building the Half Mini DMA setup. Y.W. thanks Dr. Chongai Kuang from Brookhaven National Laboratory for the opportunity to discuss experimental results. This work was supported by the Solar Energy Research Institute for India and the United States (SERIIUS), funded jointly by the U.S. Department of Energy (Office of Science, Office of Basic Energy Sciences, and Energy Efficiency and Renewable Energy, Solar Energy Technology Program, under Subcontract DE-AC36-08GO28308 to the National Renewable Energy Laboratory, Golden, Colorado) and the Government of India, through the Department of Science and Technology under Subcontract IUSSTF/JCERDC-SERIIUS/2012.
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