Synthesis flame spray pyrolysis

In this work, flame spray pyrolysis was applied to the synthesis of titania particles to control the crystal structure and crystallite size and compared with the particle prepared by the conventional spray pyrolysis... 

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

Mueller R, Madler L, et al (2003) Nanoparticle synthesis at high production rates by flame spray pyrolysis. Chemical Engineering Science 58(10), 1969-1976... 

FIGURE 10.6 Result of the fitting using the fundamental parameter approach in ZnO/Si02 powder (2 1). The black and gray lines correspond to the measured and calculated XRD patterns, respectively. (From Tani, T., Madler, L., and Pratsinis, S.E., Synthesis of zinc oxide/silica composite nanoparticles by flame spray pyrolysis, J. Mater. Set, 37, 4627, 2002.)... 

It has been shown that flame spray pyrolysis can be used to produce metal-oxide catalysts with large surface areas. The surface area is strongly influenced by the flame conditions and the burner design. The properties of the final particles can be designed by changing the conditions during the synthesis. 

Two commercial stoichiometric Sp powders (Mg Alsl.0) were used. The first (labeled here Nl) is derived from A1 and Mg hydrated sulfate salts, using solution chemistry it is supplied by Baikowski (La Balme de Silligny, France). The calcination temperature is of-1100°C. The second, produced by Nanocerox (Ann Arbor, Ml, USA) was synthesized by flame-spray pyrolysis from a double Al-Mg alkoxide precursor. The synthesis product is calcined at 650°C. 

Azurdia JA, Marchal J, Laine RM. Synthesis and characterization of mixed-metal oxide nanopowder along the CoO t-Al203 tie line using liquid feed flame spray pyrolysis. J Am Ceram Soc 2006 89(9) 2749-56. 

The technique of flame spray pyrolysis (FSP) is one of the technologies from this list, tested for gas sensor design (Madler et al. 2006a, b Liu et al. 2005b). It should be noted that FSP is a well-known method which is widely applied for the industrial production of powders. One can understand the nature of this method of synthesis from its name. One can find a detailed description of FSP technology in several published papers (Pratsinis 1998 Madler et al. 2002,2006b Tricoli et al. 2010 Strobel and Pratsinis 2007). Usually the FSP apparams involves the scheme shown in Fig. 20.25. 

Yuan et al. used the technique of flame spray pyrolysis to prepare YSZ powder with a narrow particle distribution [6]. Zhang and Messing [7] demonstrated an important criterion for the synthesis of fine solid particles from the observation that the precipitated salt particles do not suffer plastic deformation or melt during heating, because of the formation of droplets from reservoirs with low permeability. Consequently, the residual solvent is trapped in the dried droplet, resulting in an increase in pressure, because then the solvent cannot evaporate... 

Flame spray pyrolysis and ultrasonic spray combustion represent other methods leading to perovskites with comparable morphologies with those produced by solid-sohd reactions and solution combustion synthesis [23]. 

Mueller R., Madler L., Pratsinis S.E., Nanoparticle synthesis at high production rates by flame spray pyrolysis. Chem. Engng Sci. 2003 58(10) 1969-1976 Murphy, P.J., Posner A.M., Quirk J.P. Characterization ofpartially neutralized ferric nitrate solutions. J. Colloid Interface Sci. 1976a 56(2) 270-283... 

Widely used methods in the synthesis of silica nanoparticles are the sol-gel process and flame synthesis [5]. The latter is an effective synthetic route to continuously produce extremely pure nanoparticles, but in many cases the final products are agglomerated or show low reactive surfaces that make them difficult to functionalize. Nevertheless, flame synthesis is a prominent method to commercially produce silica nanopartides in powder form [6]. It is being used since decades for the production of the so-called fumed siUca, which is a filler in many applications, for example, in the pharmaceutical or polymeric business [7]. The extension of this preparation route is the so-called flame spray pyrolysis that has expanded in the last two decades to many other material compositions and is a promising rapid technique for the production of nanopowders [8]. 

We recently described two discoveries that offer solutions to this problem. First, a new, simple synthesis of polymeric precursors to P"-alumina made directly from NaOH, alumina and triethanolamine, TEA (2). Second, we learned to form a wide variety of ultrafine aluminosilicate ceramic powders by flame spray pyrolysis processing of these polymers. The goal of the current research program is to demonstrate that it is possible to produce reasonable quality P"-alumina shapes using these low cost precursors and powders. 

Various methods are applied to the synthesis of titania particles including sol-gel method, hydrothermal method [2], citrate gel method, flame processing and spray pyrolysis [1]. To utilize titania as a photocatalyst, the formation of ultrafme anatase titania particles with large crystallite size and large surface area by various ways has been studied [4]. 

Chemical Vapor Deposition (CVD) has been defined as a materials synthesis process whereby constituents of the vapor phase react chemically near or on a substrate surface to form a solid product. With these traditional processes a reaction chamber and secondary energy (heat) source are mandatory making them different from the Combustion CVD process. Numerous flame-based variations of CVD have been used to generate powders, perform spray pyrolysis, create glass forms, and form carbon films including diamond films. 

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)...

The generic apparatus used in a vapor precursor process is very similar to that used in spray pyrolysis, except that the precursor material is introduced to the reactor as a vapor (see Figure 2.1, 2. la). If the precursor is a liquid, carrier gas is typically bubbled through it. If the precursor is a solid, then the carrier gas is often passed through a heated, packed bed of the material. The vapor-laden carrier gas then flows to a furnace reactor, where thermal decomposition of the precursor occurs and particle formation results. Product powder is collected or measured at the reactor outlet. Flame processes also fall into the vapor precursor/thermal decomposition category of gas-phase powder synthesis. The only difference is that the thermal energy is provided by combustion as opposed to an external source. 

The application oiflame spray pyrolysis to NP synthesis generally resulted in the production of metal oxides and salts [54—57]. Recently, Athanassiou et al. proposed the use of a flame-SP apparatus which operated in continuous fashion in a nitrogen-filled glovebox to produce carbon-coated Cu NPs with a good size uniformity [58]. 

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