The Initial Stages of Multicomponent Particle Formation during the Gas Phase Combustion Synthesis of Mixed SiO₂/TiO₂


The ability to properly scale the synthesis of advanced materials through combustion synthesis routes is limited by our lack of knowledge regarding the initial stages of particle formation. In flame aerosol reactors, the high temperatures, fast reaction rates, and flame chemistry can all play a critical role in determining the properties of the resulting nanomaterials. In particular, multicomponent systems pose a unique challenge as most studies rely on empirical approaches toward designing advanced composite materials. The lack of predictive capabilities can be attributed to a lack of data on particle inception and growth below 2 nm. Measurements for the initial stages of particle formation during the combustion synthesis of SiO2 and composite SiO2/TiO2 using an atmospheric pressure inlet time-of-flight mass spectrometer are presented. Both positively and negatively charged clusters can be measured and results show the presence of silicic acid species which grow through dehydration, hydrogen abstraction, and interactions with hydroxyl radicals. In the case of composite SiO2/TiO2 particle formation, new molecular species containing Ti atoms emerge. Tandem differential mobility analysis-mass spectrometry (DMA-MS) provided further insight into the size-resolved chemistry of particle formation to reveal that at each cluster size, further hydroxyl-driven reactions take place. From this we can conclude that previous assumptions on collisional growth from simple monomer species of SiO2 and TiO2 do not sufficiently describe the collisional growth mechanisms for particle growth below 2 nm.


Civil, Architectural and Environmental Engineering


This work is 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. The work was also supported by Academy of Finland via Center of Excellence project in Atmospheric Sciences (272041) and European Commission via ACTRIS2 (654109).

Keywords and Phrases

Aerosols; Atmospheric pressure; Chemical analysis; Mass spectrometers; Mass spectrometry; Particle size analysis; Reaction rates; Silica; Silicon compounds; Titanium compounds; Titanium dioxide; Advanced composite materials; Flame aerosol reactor; Hydrogen abstraction; Multi-component systems; Predictive capabilities; Size-resolved chemistry; Tandem differential mobility analysis; Time-of-flight mass spectrometers; Combustion synthesis; Hydrogen; Hydroxyl group; Hydroxyl radical; Silicic acid; Silicon dioxide; Titanium dioxide; Article; Atom; Chemical interaction; Chemical reaction; Combustion; Gas; Molecule; Particle size; Priority journal; Synthesis; Time of flight mass spectrometry

International Standard Serial Number (ISSN)

0278-6826; 1521-7388

Document Type

Article - Journal

Document Version


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