Flame synthesis

Aerosol flame synthesis is a mature technology. A solid phase is generated by dispersing the metal precursors in a flame. The first reports are dated from the 1970s to the 1980s [17-19]. Reviews can be found in [20, 21]. Three different approaches are identified, depending on the state of precursor ... 

Vapor fed aerosol flame synthesis (VAFS) the precursor is in gas phase by using volatile metal precursors such as chlorides. 

Use of flames as external heat source to induce quick drying and calcination One-step aerosol flame synthesis... 

Recently, nanocomposites of calcium and bismuth mixed oxides obtained by flame synthesis were used for the degradation of organic dyes under visible light, with good activity due to the formation of relatively high surface area materials and oxygen vacancy formation in the flame process [119]. 

CNTs can also be produced by diffusion flame synthesis, electrolysis, use of solar energy, heat treatment of a polymer, and low temperature solid pyrolysis. In flame synthesis, combustion of a portion of the hydrocarbon gas provides the elevated temperature required, with the remaining fuel conveniently serving as the required hydrocarbon reagent. Hence, the flame constitutes an efficient source of both energy and hydrocarbon raw material. Combustion synthesis has been shown to be scalable for a high volume commercial production. 

Johannessen T, Jenson JR, Mosleh M, Johansen J, Quaade U, Livbjerg H (2002) Flame synthesis of nanoparticles Application in catalysis and product/process engineering. Chem Eng Res Des 82 1444-1452... 

Hou S, Chung D, Lin T (2009) Flame synthesis of carbon nanotubes in a rotating counterflow. J Nanosci Nanotechnol 9 4826-4833... 

S. Loher, W.J. Stark, M. Maciejewski, A. Baiker, S.E. Pratsinis, D. Reichardt, F. Maspero, F. Krumeich, D. Gunther, Fluoro-apatite and calcium phosphate nanoparticles by flame synthesis, Chem. Mater. 17 (2005) 36-42. 

Jones AC (2002) Molecular design of improved precimsors for the MOCVD of electroceramic oxides. Journal of Materials Chemistry 12(9), 2576-2590 Jones AC, Chalker PR (2003) Some recent developments in the chemical vapour deposition of electroceramic oxides. Journal of Physics D-Applied Physics 36(6), R80-R95 Kammler HK, Madler L, et al (2001) Flame synthesis of nanoparticles. Chemical Engineering Technology 24(6), 583-596... 

The specific surface area (Sbet) °f silicas produced by burning of SiCl4 in an 02/H2/N2 flame can be varied over a large range from 50-500 m2/g (Table l).6,7 Features of the flame synthesis and the nature of amorphous nanosilicas cause certain generic characteristics (i) a roughly spherical shape of nonporous... 

Economically feasible large-scale production and purification techniques must still be developed. In arc discharge, a vapour is created between two carbon electrodes with or without catalyst. In the laser ablation technique, a high-powered laser beam impinges on a volume of carbon-containing feedstock gas. Flame synthesis is used in a controlled flame environment.8... 

Gas-phase nucleation Flame synthesis of particles (e.g., carbon black, silica) cluster formation in chemical vapor deposition manufacture of high-purity silicon cluster structure and energetics plasma synthesis of refractory materials and coatings. 

Strobel R, Baiker A, Pratsinis SE. Aerosol flame synthesis of catalysts. Advanced Powder Technology. 2006 17 457-480. 

Hannemann S, Grunwaldt J-D, Gunther D, Krumeich F, Lienemann P, Baiker A. Combination of flame synthesis and high throughput experimentation preparation of alumina supported noble metal particles and their application in the catalytic partial oxidation of methane. Appl Catal A. 2007 316 226. 

Gas phase ceramic synthesis is the subject of several review papers. The treatment here is analogous to that in Magan [1], Friedlander [2], and Pratsinis and Kodas [3] but instead of using the traditional aerosol nomenclature, this chapter uses the nomenclature developed in Chapter 3 on population balances for educational continuity. Each of the gas phase powder synthesis methods is summarized in Table 7.1. The maximum temperatures are also listed. The adiabatic flame temperature is the maximum possible temperature achieved in flame synthesis and will depend on the concentration of reactants in the feed. Powder synthesis in a furnace uses conduction, convection, and radiation, giving a maximum temperature of 2300 K. A plasma is an ionized gas. High velocity electrons remove other electrons from the neutral gas molecules present in the plasma, thereby producing ions and electrons that sustain the plasma. 

In another example of flame synthesis, H2 (or other fuel) and O2 are used for combustion, and droplets of an aqueous salt solution are entrained in one of the streams. In a particular example an aqueous salt solution of yttrium, barium, and copper nitrates was used to create the aerosol entrained in the dry O2 stream of a hydit en-o gen coan-nular diffusion flame with the oxidant as the inner stream. The result was an una lomerated YBa2Cu30 powder witti a critical superconducting temperature of 92 K [5] confirming its high paiily. 

FIGURE 10.3 Powder x-ray patterns of ceria-zirconia made by using two different liquid carriers for the precursors. The isooctane-hased carrier composition forms a product containing a ceria-rich (Figure 10.2, left peak, hottom trace) and a zirconia-like phase (right peak). In contrast, apphcation of the lanric/acetic acid-based carrier solution resnlts in a single mixed oxide phase (top trace) (From Stark, W.J., Madler, L., Maciejewski, M., Pratsinis, S.E., and Barker, A., Flame synthesis of nanocrystalline ceria-zirconia effect of carrier liquid, Chem. Commun., 5, 588, 2003.)... 

Kammler, H.K., Jossen, R., Morrison, P.W., Jr., Pratsinis, S.E., and Beaucage, G., The effect of external electric fields during flame synthesis of titania, Powder TechnoL, 310, 135-136, 2003. 

Tsantilis, S., Kammler, H.K., and Pratsinis, S.E., Population balance modeling of flame synthesis of titania nanoparticles, Chem. Eng. Set, 57, 2139, 2002. Madler, L., Stark, W.J., and Pratsinis, S.E., Simultaneous deposition of Au nanoparticles during flame synthesis of Ti02 and Si02, J. Mater. Res., 18, 115, 2003. Tani, T., Madler, L., and Pratsinis, S.E., Synthesis of zinc oxide/sihea composite nanoparticles by flame spray pyrolysis, J. Mater. Set, 37, 4627, 2002. 

Kammler, H.K., and Pratsinis, S.E., Carbon-coated titania nanoparticles continuous, one-step flame-synthesis, J. Mater. Res., 18, 2670, 2003. 

Ulrich, G- D. (1984) Flame Synthesis of Fine Particles. Cheiii. Eng. News, 62.22. 

T. Johannessen, S. Koutsopoulos, One-Step Flame Synthesis of an Active Pt/Ti02 Catalyst for S02 Oxidation-A Possible Alternative to Traditional Methods for Parallel Screening, J. Catal. 205 (2002) 404. 

The flame synthesis is a promising method for producing catalysts with high activity and stability. CuZnCeAl showed almost no deactivation and was the most active catalyst after about 10 h on stream. The catalysts can be produced in one step and the production on a larger scale could be beneficial compared to conventional methods. Ti02 and Si02 are already today produced in large quantities by flame synthesis [10]. 

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