Ceramic powder synthesis atomization

Strength, brittleness, and solvent permeability properties are limited because of lack of control of the ceramic composition on a macro- and microlevel. Even small particle sizes are large compared with the molecular level. There have been a number of attempts to produce uniform ceramic powders including the sol-gel synthesis in which processing involves a stable liquid medium, coprecipitation in which two or more ions are precipitated simultaneously. More recently, Carraher and Xu have used the thermal degradation of metal containing polymers to deposit metal atoms and oxides on a molecular level. 

The simplest system involves the reaction between two solid phases, A and B, to produce a solid solution C. A and B are commonly elements for metallic systems, while for ceramics they are commonly crystalline compounds. After the initiation of the reaction, A and B are separated by the solid reaction product C (Fig. 2.13). Further reaction involves the transport of atoms, ions, or molecules by several possible mechanisms through the phase boundaries and the reaction product. Reactions between mixed powders are technologically important for powder synthesis. However, the study of reaction mechanisms is greatly facilitated by the use of single crystals because of the simplified geometry and boundary conditions. 

The surfaces of oxide nanopowders have been extensively studied either for characterization purposes or for potential catafytic properties investigatioa As for non-oxide ceramic powders, references on their surface studies are scarce. Due to hydrolysis in ambient atmosphere, the unavoidable presence of oxygen in the first atomic layer of these nanostructured powders may drastically modify their expected properties. After briefly introducing our characterization technique of nanosized powder sur ces, we will present as an exan le, the Fourier transform infixed (FT-IR) sur ce analysis of a nanostructured aluminum nitride powder obtained via sol-gel type chemical synthesis. 

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