Aerosol spray synthesis methods

The ideal control on the structural and textural properties of perovskite-type oxides can be better achieved by exploiting aerosol spray synthesis methods to prepare highly dispersed and nanostructured materials from metal salt precursors. High-specific-surface-area (above 20m /g) crystalline perovskite-type oxides can be then obtained, which are suitable for a variety of applications. A major advantage of spray methods is that the material is directiy processed from the precursor solution with a reduced number of processing steps during powder synthesis (one-step approach), thus making them ideally suited for... 

Several aerosol nanoparticle reactors have been built and characterized in which one or more convenient process parameters can be used to control the particle size distribution, including particle diameter and number concentration. To address the diverse needs of the NOSH Consortium membership, various aerosol nanoparticle synthesis methods have been employed, including thermal decomposition of hquid precursor vajxrrs, spray atomization of hquids of soluble materials or solid susjjensions, and thermal vaporization of solid metals. These aerosol nanoparticle reactors are used in subsequent NOSH Consortium activities as detailed in the remaining... 

Four different routes were employed for the synthesis of iron-oxide-based redox water-sphtting materials Solid-State Synthesis (SSS), Self-Propagating High-Temperature Synthesis (SHS), Gel Combustion (GC) and Aerosol Spray Pyrolysis (ASP) [8]. These synthesis methods were chosen with the rationale to exploit particular characteristics of each one for the synthesis of products with tunable oxygen vacancies concentration. The synthesis details have been reported previously [8], therefore only the general reaction concepts are reported below, where A and B denote the bivalent dopant metals Ni, Mn or Zn. 

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... 

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... 

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