Aerosol processing

The first important condition for efficient aerosol processing is to use stable colloidal dispersions or solutions, the so-called sok, as initial hquid phases to be sprayed. These suspensions/solutions must be sufficiently kinetically stable to allow processing of the full batch, which takes from few minutes to 1 h depending on the equipment. The sol precursor can be composed of dispersed dense or porous nanoparticles mixed with soluble sol-gel precursors, organic or hybrid 

Route B corresponds to the use of an initial solution containing molecular reactive sol-gel precursors combined with molecular surfactants or amphiphilic block copolymers. It allows generating mesoporous microspheres via evaporation-induced self-assembly (EISA) [15] or evaporation-induced micelle packing 

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Simulation of aerosol processes within an air quaUty model begins with the fundamental equation of aerosol dynamics which describes aerosol transport (term 2), growth (term 3), coagulation (terms 4 and 5), and sedimentation (term 6) ... 

Specific advancements ia the chemical synthesis of coUoidal materials are noteworthy. Many types of genera ting devices have been used to produce coUoidal Hquid aerosols (qv) and emulsions (qv) (39—43) among them are atomizers and nebulizers of various designs (30,44—50). A unique feature of produciag Hquid or soHd coUoids via aerosol processes (Table 3) is that material with a relatively narrow size distribution can be routinely prepared. These monosized coUoids are often produced by relying on an electrostatic classifier to select desired particle sizes ia the final stage of aerosol production. 

Kodas, T. T. Hampden-Smith, M. J. 1999. Aerosol Processing of Materials. Wiley-VCH, New York. Chapter 5. 

Figure 1. Aerosol process configuration for the continuous preparation of metal oxides by the High Temperature Aerosol Decomposition (HTAD) Process.

To illustrate the capabilities of the aerosol process for the synthesis of solid state oxidation catalysts not normally obtained from classical synthesis, the preparation of a series of P-V-0 catalysts was examined. The original objective was to determine whether the synthesis of the reported (4) active phase, P-(VO)2P207, of the catalyst responsible for the selective oxidation of butane to maleic anhydride could be synthesized by the aerosol technique. 

Aerosol processes afford materials having an optimum phase purity as contrasted to catalysts prepared by other synthetic methods. In addition, their syntheses are reproducible and metal ion concentrations are predictable based on starting... 

Finally the aerosol process could be used to coat particles, as exemplified in the system of titania cores and polyurea shells (39). In this case the titania particles were generated from Ti(IV) ethoxidc as described earlier, then contacted with dried... 

TT Kodas, MJ Hampden-Smith. Aerosol Processing of Materials. New York Wiley-VCH, 1999. 

Figure 7.37 Schematic illustration of gas-to-particle synthesis via thermal aerosol processing. From Carbide, Nitride, and Boride Materials Synthesis and Processing, A. W. Weimer, ed., p. 308. Copyright 1997 by Chapman Hall, London, with kind permission of Kluwer Academic Publishers.

A-V. Brichkin et al, Ibid, 1968, (65/22), 75—92 St CA 71, 31940b (1969) (Aerosol process for charging loose expls, such as Igdanit, into boreholes is claimed to be more convenient, safe and rapid than pneumatic charging)... 

Even though there is no significant change in the CCN number concentrations between days of the week, this is not yet the complete picture of potential aerosol-cloud weekend effects. There are many other potential aerosol processes, such as semi-direct effect, which could have significant effect on the local meteorology. Also, the CCN number concentrations have a weak weekday variation within the cities, which could then lead to meteorological weekend effect directly above the urban environment. However, as the urban or semi-urban areas cover spatially quite small area of the Europe (around 5%) [27], the weekend effect is then of much more a local effect, if it exists at all. 

So far LII has only been applied for aerosol processes without the consideration of particles dispersed in liquids. First, investigations were carried out with re-dispersed carbon blacks. Besides furnace blacks (Printex A, G, 25, 35, and 55), various gas carbon black particles (FW 18, Colour Black SI60 and S170, Printex U and U140) were also considered. The particles were suspended in different liquids and dispersed by ultrasonic excitation. The stability of the suspension was recorded by measuring the aggregate size distribution (diffusion diameter) with DLS. Moreover, this was done before and after the LII measurements in order to control the stability of the particle suspension. To achieve LII... 

Moser, W. R., Lennhoff, J. D., Cnossen, J. E., Fraska, K., Schoonover, J. W., and Rozak, J. R., The preparation of advanced catalytic materials by aerosol processing, in Advanced Catalysts and Nanostructured Materials, Novel Preparative Techniques (W. R. Moser, Ed.), p. 535, Academic Press, New York (1996). 

Nanostructured materials (continued) synthesis for advanced catalysts, 2-3 synthesis of TiC>2 by aerosol process, 6 varying grain size of crystallites, 4 Nanowires... 

Kuhlman, M. R., A Model of Sulfuric Acid Aerosol Processes, Ph.D. diss., University of North Carolina, Chapel Hill, 1982. 

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