Flame-nozzle synthesis of nanoparticles
Rapid quenching of a flame aerosol with a critical flow nozzle placed above and into the synthesis flame is investigated for precision control of product particle properties. By controlling the flame length with the expansion nozzle, particle growth can be frozen at desired levels, so synthesis of particles with a broad range of sizes, morphologies and phase compositions can be achieved. For instance, the average primary particle diameter of titania nanoparticles was controlled from 5 to 55 nm and the phase composition from 85 to 10 wt-% anatase and the balance rutile with the flame-nozzle process. The rapid quenching procedure also allows the synthesis of metastable oxides like substoichiometric (blue) titania that are good as pigments in the cosmetics industry.
Further, nozzle-quenching of silica/titania particles facilitates the synthesis of rather smooth silica coatings on titania core particles.
Recent, relevant references:
- K. Wegner, and S.E. Pratsinis, "Nozzle-quenching process for controlled flame synthesis of titania nanoparticles," AIChE J. 49, 1667 (2003).
- A. Teleki, S.E. Pratsnis, K. Wegner, R. Jossen, and F. Krumeich, "Flame-coating of titania particles with silica", J. Mater. Res. 20, 1336 (2005).