Flame synthesis has been applied for several decades for the large-scale manufacturing of metal oxides such as silica and titania. Recent developments including flame spray pyrolysis and reducing flame synthesis further allow the production of biomaterials, carbonates, fluorides and even metal nanoparticles by a cost-efficient gas-phase process. While both the chemical kinetics and mixing properties of highly turbulent flames are poorly understood, gas-phase thermodynamics as well as aggregation and sintering assumptions can be applied for the explanation of shape, size and composition of flame-made nanoparticles.

We show how simple calculations based on solid state chemistry data may be applied together with gas phase thermodynamics to influence the product composition of the flame process. The chemical reaction engineering of flame spray processing is further illustrated by showing possibilities and limitations of a variety of examples starting from cerium oxide[1], calcium-carbonate[2], nano-gypsum, alkali-earth fluorides[3] to metallic bismuth[4], copper[5] and cobalt[6] nanoparticles.

[1] W. J. Stark, L. Madler, M. Maciejewski, S. E. Pratsinis, A. Baiker, Chem. Commun., 2003, 588. [2] M. Huber, W. J. Stark, S. Loher, M. Maciejewski, F. Krumeich, A. Baiker, Chem. Commun., 2005, 648. [3] R. N. Grass, W. J. Stark, Chem. Commun., 2005, 1767. [4] R. N. Grass, W. J. Stark, J. Nanoparticle Res., 2006, In Press. [5] E. A. Athanassiou, R. N. Grass, W. J. Stark, Nanotechnology, 2006, 17, 1668. [6] R. N. Grass, E. K. Athanassiou, W. J. Stark, EP Patent application 05 019287.1, 2005; R. N. Grass, W. J. Stark, J. Mater. Chem., 2006, DOI: 10.1039/b601013j.