Powder aluminum nitride

Baraton, M. I., Chen, X., and Gonsalves, K. E., FTIR study of nanostructured aluminum nitride powder surface determination of the acidic/basic sites by CO, CO2 and acetic acid adsorptions. Nanostructured Materials 8 (4), 435-445 (1997). 

The hydrolysis of the aluminum nitride powder is well known and has been investigated by many authors. Bowen et al. proposed the following reaction scheme ... 

K. Kmel, T. Kosmac, Reactivity of aluminum nitride powder in dilute inorganic acids, J. Am. Ceram. Soc., 83 (2000) 1375-1378. 

J.G. Highfield, P. Bowen, Diffuse-Reflectance Fourier Transform Infrared Spectroscopic Studies of the Stability of Aluminum Nitride powder in an Aqueous Environment, Anal. Chem., 61 (1989) 2399. 

Aluminum nitride powder synthesized by high-temperature routes can be sintered to a density of more than 97% of the theoretical density by adding calcium or yttrium compounds as sintering aids [52-54]. Therefore, new processing routes to aluminum nitride predominantly aim at powders with lower quantities of cationic impurities. In addition, the formation of aluminum nitride coatings [55-58] or fibers [59] has become subject of extensive research. 

Highfield, J. G., and Bowen, P., Diffuse-reflectance Fourier transform infrared spectroscopic studies of the stability of aluminum nitride powder in an aqueous environment, Anal. Chem., 61, 2399 (1989). 

Ceramic particles in organic liquid media behave differently from those in aqueous media. Many known ceramic-processing techniques involve fine particles dispersed in nonaqueous media. Some of the better known examples are tape casting of barium titanate and aluminum nitride powders and tape or slip casting, extrusion, and injection molding of ceramic high Tc superconductor powders. 

Such calculations showed that the square of the structure amplitude F for aluminum nitride powder was given by the following relationships ... 

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. 

Let us demonstrate comparative analysis of the aluminum nitride powders synthesized in SHS-Az regime according to Equation 8.12 and from the system element-azide-ammonium halide. ... 

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

D. Hotza, et al., Hydrophobic Aluminum Nitride Powder for Aqueous Tape Casting pp. 397-401 in Ceramic Transactions, Vol. 51, Ceramic Processing Science and Technology. Edited by H. Hausner. G. L. Messing, and S. Hirano. The American Ceramic Society, Westerville, OH, 1995. 

Aluminum nitride powder is obtained by the carbothermal reduction of alumina, the decomposition of aluminum chloride and ammonia, and the reaction of aluminum powder with ammonia or nitrogen. 

Study of an Aluminum Nitride Powder Prepared via Chemical Synthesis... 

Due to unsaturation or strain, equilibrium of the interatomic forces on a sur ce is reached by adsorption of surrounding molecules. Therefore, the chemical composition of the fost atomic layer may be different from that of the bulk. The importance of the sur ce with respect to the bulk in nanostructured powders makes the exact knowledge of the sur ce composition critical. Fourier transform infrared (FT-IR) spectrometry is a powerful tool to determine the nature of the chemical sur ce species as well as the reactive sites. As an example of an FT-IR sur ce study, a nanostructured aluminum nitride powder was analyzed and its sur ce was coiiq)ared with the y-alumina sur ce. 

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. 

The sur ce FT-IR stey of a nanosize aluminum nitride powder definitely brought evidence of the specific chemical composition of its first atomic layer. The unavoidable contamination, mainly by atmospheric water, implies the presence of oxygen and hydrogen in this first layer. As a result, a comparison with the alumina sur ce appeared quite reasonable. Indeed, methanol and pyridine used as probe molecules showed the same behavior on both material sur ces. The acidity of the AIN sur ce was proven by the presence of two types of Al Lewis sites. However for AIN, a specific dissociative adsorption mechanism of acidic methanol could be possibly explained by the presence of weakly basic AI3N sites. Besides, the isotopic exchange... 

Aerosol techniques on-line sizing of colloidal nanoparticles, 20-40 ultrafine powder synthesis, 64 Ag particles, synthesis method, 128 Aluminum nitride powder prepared via chemical synthesis, characterization using Fourier-transform IR spectroscopy, 312-332... 

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. 

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