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Flame-made Nanostructured Materials: Aerosol Dynamics at High Particle Concentration

Applicant Pratsinis Sotiris E.
Number 119946
Funding scheme Project funding (Div. I-III)
Research institution Institut für Verfahrenstechnik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Chemical Engineering
Start/End 01.04.2008 - 31.03.2011
Approved amount 280'500.00
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Keywords (5)

Coagulation; High Particle Concentration; Langevin Dynamics; Nanostructured Materials; Flame Aerosol Reactor

Lay Summary (English)

Lead
Lay summary
Today the high potential of nanostructured materials and their applications are well understood. Their widespread use, however, depends to a large extent on the development of economic manufacturing routes. Though such materials can be made by wet or dry processes, the latter offer a proven scalable route for production of several micro- or nano-structured commodities such as carbon blacks, pigmentary titania, zinc oxide, filamentary nickel, optical fibers, fumed silica and alumina esp. by the flame route that accounts for 90% by volume or value of all aerosol-made materials. As major strides in fundamental understanding of aerosol reactors have been made recently, an array of sophisticated materials (well beyond the above simple ones) have been synthesized (mostly in academic laboratories) that are ready to be used for manufacture of catalysts, sensors, biomaterials and even nutritional supplements.Very recently it was shown that synthesis of these nanostructured materials at the high concentrations that brought them economically to the market will involve particle dynamics beyond the ones engineers are accustomed to. Simply put, agglomerates of the typical fractal-like nanostructured materials influence far more volume than the one corresponding to their solid mass. As a result, the fundamentals of coagulation of such particles need to be re-evaluated as, for example, the classic Smoluchowski equation no longer holds. Here this is accomplished by Langevin dynamic simulations that aim to understand the onset of gelation, effectively meaning the onset of agglomerate restructuring and even fragmentation in particle-laden process streams over the complete size spectrum: from the free molecule to the continuum regime. The employed stochastic algorithms will be rigorously validated against analytical and asymptotic (self-preserving) solutions of the particle size distribution at low particle concentrations with detailed, highly accurate, sectional population balance models. As this quantitative understanding is developed, other fundamental phenomena that affect the characteristics of aerosol-made nanostructured materials such as surface growth, sintering and shear-induced coagulation will be introduced. Simplified expressions would be deduced facilitating the use of such results by practitioners. Emphasis would be on the attainment of self-preserving size distributions as they greatly facilitate coagulation-sintering calculations coupled to fluid mechanics in industrial aerosol processes. Parallel to this, a systematic experimental study would be carried out capitalizing on our reactor units capable of producing up to 1 kg/h of nanostructured particles and in-situ (FTIR and PDA) and ex-situ (gas adsorption, XRD, TGA, Raman, UV-Vis etc.) diagnostics for synthesis of silica, titania, zirconia or alumina particles where an extensive data base and precursor knowledge is available here. Conditions would be identified that are prone to synthesis of fractal-like particles of vastly differing states of agglomeration (aggregates vs. agglomerates) and even gelation. Product particles will be characterized focusing on their primary particle size as well as on aggregate-agglomerate size and structure by state-of-the-art instrumentation in our labs. This project will assist the education of two PhD students in engineering specializing on nanoparticle processing. It will allow also Bachelor and Master students to gain knowledge in analytical methods and particle- and nano-technologies. Research results will be presented at international conferences and submitted to refereed journals.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
149144 Multiscale Design of Aerosol Synthesis of Nanomaterials 01.10.2013 Project funding (Div. I-III)
121359 Rig for design and scale-up of flame aerosol synthesis of nanostructured materials 01.07.2008 R'EQUIP

Abstract

Today the high potential of nanostructured materials and their applications are well understood. Their widespread use, however, depends to a large extent on the development of economic manufacturing routes. Though such materials can be made by wet or dry processes, the latter offer a proven scalable route for production of several micro- or nano-structured commodities such as carbon blacks, pigmentary titania, zinc oxide, filamentary nickel, optical fibers, fumed silica and alumina esp. by the flame route that accounts for 90% by volume or value of all aerosol-made materials. As major strides in fundamental understanding of aerosol reactors have been made recently, an array of sophisticated materials (well beyond the above simple ones) have been synthesized (mostly in academic laboratories) that are ready to be used for manufacture of catalysts, sensors, biomaterials and even nutritional supplements.Very recently it was shown that synthesis of these nanostructured materials at the high concentrations that brought them economically to the market will involve particle dynamics beyond the ones engineers are accustomed to. Simply put, agglomerates of the typical fractal-like nanostructured materials influence far more volume than the one corresponding to their solid mass. As a result, the fundamentals of coagulation of such particles need to be re-evaluated as, for example, the classic Smoluchowski equation no longer holds. Here this is accomplished by Langevin dynamic simulations that aim to understand the onset of gelation, effectively meaning the onset of agglomerate restructuring and even fragmentation in particle-laden process streams over the complete size spectrum: from the free molecule to the continuum regime. The employed stochastic algorithms will be rigorously validated against analytical and asymptotic (self-preserving) solutions of the particle size distribution at low particle concentrations with detailed, highly accurate, sectional population balance models. As this quantitative understanding is developed, other fundamental phenomena that affect the characteristics of aerosol-made nanostructured materials such as surface growth, sintering and shear-induced coagulation will be introduced. Simplified expressions would be deduced facilitating the use of such results by practitioners. Emphasis would be on the attainment of self-preserving size distributions as they greatly facilitate coagulation-sintering calculations coupled to fluid mechanics in industrial aerosol processes. Parallel to this, a systematic experimental study would be carried out capitalizing on our reactor units capable of producing up to 1 kg/h of nanostructured particles and in-situ (FTIR and PDA) and ex-situ (gas adsorption, XRD, TGA, Raman, UV-Vis etc.) diagnostics for synthesis of silica, titania, zirconia or alumina particles where an extensive data base and precursor knowledge is available here. Conditions would be identified that are prone to synthesis of fractal-like particles of vastly differing states of agglomeration (aggregates vs. agglomerates) and even gelation. Product particles will be characterized focusing on their primary particle size as well as on aggregate-agglomerate size and structure by state-of-the-art instrumentation in our labs. This project will assist the education of two PhD students in engineering specializing on nanoparticle processing. It will allow also Bachelor and Master students to gain knowledge in analytical methods and particle- and nano-technologies. Research results will be presented at international conferences and submitted to refereed journals.
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