Growth Mechanisms of Nanostructured Titania in Turbulent Reacting Flows

• Published in: Journal of nanotechnology 2015-01, Vol.2015 (2015), p.1-10
• Main Author: Garrick, Sean C.
• Format: Article
• Language: English
• Subjects: Coagulation; Computational fluid dynamics; Condensing; Fluid flow; Nanostructure; Titanium dioxide; Turbulence; Turbulent flow
• ISSN: 1687-9503; 1687-9511
• DOI: 10.1155/2015/642014

Titanium dioxide (titania) is used in chemical sensors, pigments, and paints andholds promise as an antimicrobial agent. This is due to its photoinduced activity and,in nanostructured form, its high specific surface area. Particle size and surface arearesult from the interplay of fluid, chemical, and thermal dynamics as well as nucleation,condensation and coagulation. After nucleation, condensation, and coagulation arethe dominant phenomena affecting the particle size distribution. Manufacture of nanostructured titania via gas-phase synthesis often occurs under turbulent flow conditions. This study examines the competition between coagulation and condensation in thegrowth of nanostructured titania. Direct numerical simulation is utilized in simulatingthe hydrolysis of titanium tetrachloride to produce titania in a turbulent, planar jet. The fluid, chemical, and particle fields are resolved as a function of space and time. As a result, knowledge of titania is available as a function of space, time, and phase(vapor or particle), facilitating the analysis of the particle dynamics by mechanism. Results show that in the proximal region of the jet nucleation and condensation arethe dominant mechanisms. However once the jet potential core collapses and turbulentmixing begins, coagulation is the dominant mechanism. The data also shows that thecoagulation growth-rate is as much as twice the condensation growth-rate.