Using In Situ Measurements to Experimentally Characterize TiO2 Nanoparticle Synthesis in a Turbulent Isopropyl Alcohol Flame.

Benedetta Franzelli,Nasser Darabiha,Philippe Scouflaire

doi:10.3390/ma14227083

Abstract

The objective of the present work is to show the potential of in situ measurements for the investigation of nanoparticles production in turbulent spray flames. This is achieved by considering multiple diagnostics to characterize the liquid break-up, the reactive flow and the particles production in a spray burner for TiO nanoparticle synthesis. The considered liquid fuel is a solution of isopropyl alcohol and titanium tetraisopropoxide (TTIP) precursor. Measurements show that shadowgraphy can be used to simultaneously localize spray and nanoparticles, light scattering allows to characterize the TiO nanoparticles distribution in the flame central plane, and spontaneous CH* and OH* chemiluminescences, as well as global light emission results, can be used to visualize the reactive flow patterns that may differ with and without injection of TTIP. Concerning the liquid, it is observed that it is localized in a small region close to the injector nozzle where it is dispersed by the oxygen flow resulting in droplets. The liquid droplets rapidly evaporate and TTIP is quasi-immediately converted to TiO nanoparticles. Finally, results show high interactions between nanoparticles and the turbulent eddies.

Highlights

Synthesis in turbulent spray flames is today considered as a valuable alternative for large-scale production of nanoparticles with a relatively low cost
It would be of interest to combine classical ex situ measurements to in situ optical diagnostics classically used in combustion research to understand the physical processes occurring during the flame synthesis by characterizing the spatial and temporal evolution of spray, flow, flame and nanoparticles
The objective of the present work was to demonstrate the interest in in situ optical diagnostics classically used in combustion research for the investigation of TiO2 nanoparticles synthesis in turbulent spray flames

Summary

Introduction

Synthesis in turbulent spray flames is today considered as a valuable alternative for large-scale production of nanoparticles with a relatively low cost. Laboratory-scale spray flame reactors [1–12] were developed to improve our understanding of nanoparticles production in these reactive flows in order to better control the characteristics and properties of the final product. Ex situ measurements are classically performed to characterize the collected materials in terms of morphology, physical and optical properties depending, for example, on operating conditions such as temperature, pressure, and precursor concentration. It is expected that the properties of nanoparticles produced via flame synthesis will depend on the experienced local conditions governed by the flow and the flame. It would be of interest to combine classical ex situ measurements to in situ optical diagnostics classically used in combustion research to understand the physical processes occurring during the flame synthesis by characterizing the spatial and temporal evolution of spray, flow, flame and nanoparticles. In situ measurements will allow the characterization of boundary conditions necessary to perform numerical simulations [13–17] and they provide an experimental database for their validation [9,18]

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Conclusion