Aerosol pyrolysis

There are various processes for synthesizing hydroxyapatite in aqua phase, such as hydrolyzation [223], acid-alkali reaction [224], hydrothermal process [225], coprecipitation [226], sol-gel synthesis [227], aerosol pyrolysis [228], and micro emulsion synthesis [229], etc. 

G. Blandenet, Y. Lagarde, and J. Spitz, Indium Oxide Deposition on Glass by Aerosol Pyrolysis, Chemical Vapor Deposition, 1975, pp. 190-203. 

In an extension of the spray-drying technique called spray roasting , evaporative decomposition of solutions (EDS) , spray pyrolysis , or aerosol pyrolysis , the temperature of the heated chamber is high enough to decompose the dried salts after the solvent has evaporated. Nitrate salts are used because of their low decomposition temperatures. The technique eliminates the problems of handling dried nitrate powders, which can be hydroscopic. These methods are used to prepare chalcogenide powders" and barium titanate . 

Precipitation from a concentrated solution of cations can be performed by solvent evaporation. To ensure that the particle size remains small, the concentrated solution may be atomised at high pressure into fine droplets of 100-500 pm diameter the solvent is rapidly evaporated by an upward stream of hot gas. The particles obtained, which can be as small as 100 nm, are compacted and calcined to produce the ceramic. A schematic representation of the spray-drying process is shown in Fig. 3.4. Several alternative methods are currently under development they are known as aerosol synthesis, aerosol pyrolysis or mist pyrolysis, depending on the specific technique to produce the gaseous suspension of fine particles aerosols are produced in high pressure nozzles and mists are obtained by means of nebulisers. YIG particles (0.25 pm) have been obtained by mist pyrolysis (Matsumoto et ai, 1991) by nebulising an aqueous solution of... 

Kavan, L., Gratzel, M. Highly efficient semiconducting Ti02 photoelectrodes prepared by aerosol pyrolysis. Electrochim. Acta 40, 643-652 (1995)... 

Fig. 23.8 Influence of bulk doping by Pt and Pd on normalized response of differently fabricated SnO -based sensors to CO. (1) Sn02 Pt Aims were deposited by spray pyrolysis of hydrolyzed solution (2,500 ppm, 7 =300-350 °C) (Data extracted from Ramgir et al. 2006). (2) Sn02 Pd powders were prepared by the reverse micelle method (200 ppm, 7 p =300 °C) (Data extracted from Yuasa et al. 2009). (3) SnO iPt films were synthesized in one step using the flame spray pyrolysis (50 ppm, 7p =300 °C) (Data extracted from Madler et al. 2006). (4) Sn02iPt films were prepared by using a submicroscopic aerosol pyrolysis method (1,300 ppm, T -250 °C) (Data extracted from Matko et al. 2002)...

Synthesis of barium titanate powders by aerosol pyrolysis of a Pechini-type precursor solution./. Mater. Chem.,... 

T Gonzalez-Carreno, MP Morales, CJ Serna. Barium ferrite nanoparticles prepared directly by aerosol pyrolysis. Mater Lett 2000 43 97. 

Gon] Gonzalez-Carreno, T., Morales, M.P., Serna C.J., Barium Ferrite Nanoparticles Prepared Directly by Aerosol Pyrolysis , Mater. Lett., 43(3), 97-101 (2000) (Magn. Prop., Experimental, Crys. Structure, 19)... 

Organic compounds are a major constituent of the FPM at all sites. The major sources of OC are combustion and atmospheric reactions involving gaseous VOCs. As is the case with VOCs, there are hundreds of different OC compounds in the atmosphere. A minor but ubiquitous aerosol constituent is elemental carbon. EC is the nonorganic, black constituent of soot. Combustion and pyrolysis are the only processes that produce EC, and diesel engines and wood burning are the most significant sources. 

Silver(I) /3-diketonate derivatives have received significant attention due to the ease with which they can be converted to the elemental metal by thermal decomposition techniques such as metal organic chemical vapor deposition (MOCVD).59 The larger cationic radius of silver(I) with respect to copper(I) has caused problems in achieving both good volatility and adequate stability of silver(I) complexes for the use in CVD apparatus. These problems have been overcome with the new techniques such as super critical fluid transport CVD (SFTCVD), aerosol-assisted CVD (AACVD), and spray pyrolysis, where the requirements for volatile precursors are less stringent. 

Snyder, A. P Maswadeh, W. M. Parsons, J. A. Tripathi, A. Meuzelaar, H. L. C. Dworzanski, J. P. Kim, M. G. Field detection of Bacillus spore aerosols with standalone pyrolysis-gas chromatography-ion mobility spectrometry. Field Anal. Chem. Technol. 1999, 3, 315-326. 

Films at NASA GRC were deposited using homemade spray or aerosol-assisted chemical vapor deposition (AACVD) reactors to exploit the lower deposition temperature enabled by the simpler decomposition chemistry for the SSPs.6 9 AACVD is a simple and inexpensive process that offers the advantage of a uniform, large-area deposition, just like metal organic CVD (MOCVD), while also offering the low-temperature solution reservoir typical of spray pyrolysis methods. 

J.P. Dworzanski, W.H. McClennen, P.A. Cole, S.N. Thornton, H.L.C. Meuzelaar, N.S. Arnold and A.P. Snyder, Field-portable, automated pyrolysis-GC/IMS system for rapid biomarker detection in aerosols A feasibility study, Field Anal. Chem. Technol., 1 (1998) 295-305. 

Spray pyrolysis routes have been extensively investigated to prepare Pt-based catalysts. Typically, a liquid feed of metal precursor and carbon is atomized into an aerosol and fed into a continuous furnace to evaporate and heat-treat to form a collectable powder. The method has good control over final aggregate particle size and metal particle size distributions, as well as producing powder without further isolation or separation. Hampton-Smith et al. have reviewed efforts of Superior MicroPowder (now Cabot Fuel Cells) in this area. ... 

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

Evaporative decomposition erf solutions and spary pyrolysis have been found to be useful in the preparation of submicrometer oxide and non-oxide particles, including high temperature superconducting ceramics [819, 820], Allowing uniform aerosol droplets (titanium ethoxide in ethanol, for example) to react with a vapor (water, for example) to produce spherical colloidal particles with controllable sizes and size distributions [821-825] is an alternative vapor phase approach. Chemical vapor deposition techniques (CVD) have also been extended to the formation of ceramic particles [825]. 

Several compounds were also found to have a seasonal distribution. Kubatova et al. (2002) found that concentrations of lignin and cellulose pyrolysis products from wood burning were higher in aerosol samples collected during low-temperature conditions. On the other hand, concentrations of dicarboxylic acids and related products that are believed to be the oxidation products of hydrocarbons and fatty acids were highest in summer aerosols. PAHs, which are susceptible to atmospheric oxidation, were also more prevalent in winter than in summer. These results suggest that atmospheric oxidation of VOCs into secondary OAs and related oxidative degradation products are key factors in any OA mass closure, source identification, and source apportionment study. However, additional work is much desirable to assess the extent and seasonal variation of these processes. 

Gelencser, A., Meszaros, T., Blazso, M., Kiss, G., Krivacsy, Z., Molnar, A., and Meszaros, E. (2000a). Structural characterisation of organic matter in fine tropospheric aerosol by pyrolysis-gas chromatography-mass spectrometry. J. Atmos. Chem. 37,173-183. 

Vallet-Regf, M., Gutierrez-Rios, M. T. and Aloso, M. P. (1994). Hydroxyapatite particles synthesized by pyrolysis of an aerosol. J. Solid State Chem., 112 58-64. 

The collection of the pyrolysis oils is difficult due to their tendency to form aerosols and also due to the volatile nature of many of the oil constituents. As the aerosols agglomerate into larger droplets, they can be removed by cyclonic separators. However, the submicron aerosols cannot be efficiently collected by cyclonic or inertial techniques, and collection by impact of the aerosols due to their Brownian or random motion must be utilized. A coalescing filter is relatively porous, but it contains a large surface area for the aerosol particles to impact by Brownian motion as they are swept through by the pyrolysis gases. Once the aerosol droplets impact the filter fibers, they are captured and coalesce into large drops that can flow down the fibers and be collected. 

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