Combustion aluminum nitride powders

At synthesis of aluminum nitride powders in gaseous nitrogen with the green mixture dilution with nitride, the dilution degree influences greatly the aluminum nitride particle size and morphology and defines practically the combustion... 

Ammonium chloride, which is contained in the green mixture, also affects aluminum nitride particle morphology. The influence of ammonium chloride on AIN particle shape and size is well seen at high content of NH4CI (10 mass%) and minimum combustion temperature, that is, at combustion under the conditions close to threshold [34]. In Figure 1.11b, we can see the general view of aluminum nitride powder obtained at F = 4 MPa and = 1890 K. It is obvious that thread-hke crystals exist along with spherical particles. It supports the idea that... 

Therefore, we can synthesize aluminum nitride powders in a wide range of sizes - from nanosized to micron powders with various morphologies (spherical, laminar, thread- and needle-like) by changing aluminum combustion temperature, nitrogen pressure, and the initial mixture composition. Each size can be considered as optimum for specific appUcations. 

Figure 8.13 SEM images of the combustion products of the (a) silicon, (b) boron, and (c) aluminum nitride powders.

Aluminum nitride powder has been synthesized by combustion and thermal explosion modes of the self-propagating high-temperature synthesis (SHS). The addition of small amounts of ammonium chloride appears to activate the reaction (Rosenband and Gany, 2004). 

Rosenband, V., and Gany, A. (2004) Activation of combustion synthesis of aluminum nitride powder. J. Mater. Proc. Technol., 147 (2), 197-203. 

Combustion Synthesis of Aluminum Nitride (AIN) Powders with Controlled Grain Morphologies... 

Structure formation of nitrides synthesized in the SHS-Az systems is investigated. During the combustion process, the use of SHS-Az systems sodium azide-halide of azotized element in some cases allowed to get nanostruc-tured powders of titanium, borium, silicium, aluminum nitrides with particles of nanofibrous structure with fiber diameter of 50-100nm and nanocrys-talline structure with crystal average-sized of 100-200 nm. 

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