Due to its combined properties of high electrical resistivity and high thermal conductivity, aluminum nitride (AIN) is a highly desirable material for electronics applications. Methods are being sought for symtliesis of unaggloinerated, nanometer-sized powders of this material, prepared in such a way that they can be consolidated into solid compacts having minimal oxygen content. A procedure for synthesizing these powders through gas-phase combustion is described. This novel approach involves reacting AICI3, NH3, and Na vapors. Equilibrium thermodynamic calculations show that 100% yields can be obtained for these reactants,mth the products being AIN, NaCl, and H2. The NaCl by-product is used to coat the AIN particles in situ. The coating allows for control of AIN agglomeration and protects the powders from hydrolysis during post-flaine handling. On the basis of thermodynamic and kinetic considerations. two different approaches were employed to produce the powder, in co-flow diffusion flame configurations. In the first approach, the three reactants were supplied in separate streams. In the second, the AICI3 and NH3 were premixed with HCI and then reacted with Na vapor. X-ray diffraction (XRD) spectra of as-produced powders show only NaCI for the first case and NaCl and AIN for the second. After annealing at 775oC under dynamic vacuum, the salt was removed and XRD spectra of powders from both approaches show only AIN. Aluminum metal was also produced in the co-flow flame by reacting AICI3 with NA..XRD spectra of as-produced powders show the products to be only NaCI and elemental aluminum.
Axelbaum, R.L., Lottes, C.R., Huertas, J.I., Rosen, L.J., Gas-Phase Combustion Synthesis of Aluminum Nitrate Powder, Twenty-Sixth Symposium (International) on Combustion, Combustion Institute, Pittsburgh, PA, pp. 1891-1897, 1996.