(87b) Opportunities And Limitations Of Flame Synthesis: Biomaterials, Metal And Alloys

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 have allowed the large scale production of biomaterials, carbonates and other salts. Controlled oxygen limitation during flame processing gives even access to non-noble metals, complex alloy nanoparticles and metal/ceramic hybrid materials.

We show how simple calculations based on solid state chemistry data may be applied together with gas phase thermodynamics to influence the product composition and to get a better insight in opportunities and limitations of flame processes. This detailed understanding provides a basis for chemical reaction engineering of flames and resulted in a variety of functional nanomaterials starting from nano-gypsum[1], calcium-phosphate[2] for bio applications, to non-noble metal[3-7] nanoparticles, complex alloys[8] and metallic / ceramic[9] nanocomposites for mechanical, magnetic or electronic applications. We demonstrate how such metal nanoparticles can be used for the preparation of bulk nanocrystalline materials, with an up to tripled Vickers hardness if compared to conventional metals.

Fig. 1: Scanning electron microscopy image of nano-NaCl (top left). Transmission electron micrograph of as prepared tricalcium phosphate nanoparticles (bottom left), which can be applied for biomedical applications such as medical implants (top right). Metallic bulk nano-bismuth pill exhibits conducting properties (bottom right).

References:

[1] N. Osterwalder, S. Loher, R. N. Grass, T.J. Brunner, L. K. Limbach, S. C. Halim, W. J. Stark, J. Nanopart. Res., 2007, 9, 275. [2] T.J. Brunner, M. Bohner, C. Dora, C. Gerber, W.J. Stark, J. Biomed. Mater. Res. Part B, 2007, DOI: 10.1002/jbm.b.30809 [3] E. A. Athanassiou, R. N. Grass, W. J. Stark, Nanotechnology, 2006, 17, 1668. [4] R. N. Grass, W. J. Stark, J. Mater. Chem., 2006, 16, 1825. [5] R.N. Grass, W.J. Stark, J. Nanopart. Res., 2006, 8(5), 729. [6] R.N. Grass, M. Dietiker, C. Solenthaler, R. Spolenak, W.J. Stark, Nanotechnology, 2007, 18(3), 035703. [7] R.N. Grass, E.K. Athanassiou, W.J. Stark, Angew. Chem. Int. Ed., 2007, in print [8] E.K. Athanassiou, R.N. Grass, N. Osterwalder and W.J. Stark, Chem. Mater, 2007, under review [9] R.N. Grass, T.F. Albrecht, F. Krumeich, W.J. Stark, J. Mater. Chem., 2007, 17, 1485.