Flame aerosol 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... 

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

Fig. 20.26 Schematic for particle formation mechanisms during flame-assisted spray pyrolysis (FASP), FSP, euid vapor-fed aerosol flame synthesis (VAFS) (Reprinted with permission from Strobel and Pratsinis 2(X)7, Copyright 2(X)7 Royal Society of Chemistry)...

Instead of assigning different shear rates, he employed different breakage rate expressions for the two zones. The problem of coupling population balance models with fluid flow models has received some attention recently and coupled PB-CFD models have been developed for a wide variety of processes such as fluidization [70], gas-liquid reactions in bubble columns [71] and nanoparticle synthesis in flame aerosol reactors [72]. Complete description of aggregation in turbulent environments requires simultaneous solution of basic balance equations for mass, momentum, energy and concentration of species present along with population balances for particles/aggregates of different size classes. 

Tiwari, V., Jiang, J., Sethi, V. and Biswas, P. (2008) One-step synthesis of noble metal titanium dioxide nanocomposites in a flame aerosol reactor. Applied Catalysis A General, 345, 241-246. 

Madler L, Kammler HK, Mueller R, Pratsinis SE (2002). Controlled synthesis of nanostructured particles by flame spray pyrolysis. J Aerosol Sci 33 369 -388... 

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. 

Pratsinis, S.E., Flame aerosol synthesis of ceramic powders, Prog. Energy Combust. ScL, 24, 197, 1998. 

Kammler, H.K., Mueller, R., Senn, O., and Pratsinis, S.E., Synthesis of silica-carbon particles in a turbulent Hj-air flame aerosol reactor, AIChE J., 47, 1533, 2001. 

W.J. Stark, K. Wegner, S.E. Pratsinis, A. Baiker, Flame Aerosol Synthesis of Vanadia-Titania Nanoparticles Structural and Catalytic Properties in the Selective Catalytic Reduction of NO by NH3, J. Catal. 197 (2001) 182. 

Thermal plasma synthesis has been used to make colloidal scale and nanoscale aerosol particles. The high temperature and inert atmosphere of the plasma enable the synthesis of materials that cannot be made in flame reactors (see, for example. Reference [46]). 

Strobel, R. Pratsinis, S. E. Flame aerosol synthesis of smart nanostractured materials./owma/ of Materials Chemistry 2007, 17, 4743-4756. 

Kammler, H.K. and Pratsinis, S.E. 2000. Electrically-assisted flame aerosol synthesis of fumed sihca at high production rates. Chem. Eng. Process. 39 219-227. 

An important topic of research is the introduction of the catalyst in the microreactor. In brief solid catalysts can be incorporated on the interior of micromachined reaction channels, prior to or after closure of the channel, by a variety of strategies anodic oxidation, plasma-chemical oxidation, flame combustion synthesis, sol-gel techniques, impregnation, wash coating, (electro-)plating, aerosols, brushing, chemical vapor deposition, physical vapor deposition and nanoparticle deposition or self-assembly. Some of these methods can be applied in combination with photolithography or shadow masking. 

Straumal B, Baretzky B, Mazilkin A, Protasova S, Myatiev A, Straumal P (2009) Increase of Mn solubUity with decreasing grain size in ZnO. J Eur Ceram Soc 29 1963-1970 Strobel R, Pratsinis SE (2007) Flame aerosol synthesis of smart nanostructured materials. J Mater Chem 17 4743-4756... 

Zhan Z, Wang W, Zhu L, An W, Biswas P (2010) Flame aerosol reactor synthesis of nanostructures Sn02 thin films high gas-sensing properties by control of morphology. Sens Actuators B 150 609-615... 

Recent advances in aerosol and combustion science and engineering now allow scalable flame synthesis of mixed oxides, metal salts, and even pure metals in the form of nanoparticles and films with closely controlled characteristics [71-76]. Flame processes are classified into vapor-fed and liquid-fed, depending on the employed state of the metal precursor [77]. Liquid-fed flame processes are distinguished for their flexibility in producing materials of various compositions and morphologies that result in unique product functionalities. 

Strobel R, Pratsinis SE. Flame aerosol synthesis of smart nanostructured materials. J Mater Chem 2007 174743-56. 

The common denominator between these aerosol spray methods is the production of fine and dispersed droplets upon spraying of a liquid solution containing the cations precursors into a flame (FSS and FH) or in a furnace (USS) (Figure 4.1) [4]. Formation of the mixed metal oxide particles occurs in the confined space of each single droplet, which can thus be considered as a microreactor. The synthesis methods differentiate from each other according to the way the liquid solution is nebulized and to the nature of the hot zone where synthesis... 

Arabi-Katbi O.I., Wegner K., Pratsinis S.E. Aerosol synthesis oftitania nanoparticles Effect of flame orientation and configuration. Ann. Chimie, Sci. Mater. 2002 27(6) 37-46 Barnickel P., Wokaun A., Sager W., Eicke H.-F. Size tailoring of silver colloids by reduction in W/0 microemulsions. J. Colloid Interface Sci. 1992 148(1) 80-90 Bender J., Wagner N.J. Reversible shear thickening in monodisperse and bidisperse colloidal dispersions. J. Rheol. 1996 40(5) 899-916... 

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