A forced-flow reactor has been designed for the synthesis of nanocrystalline AlN via in situ and ex situ nitridation of aluminum. Various reactor parameters, including evaporation temperature, microwave plasma generation, reactor pressure, gas flow rate, nitriding gas, carrier gas, and crucible purge, have been examined and optimized. Fully nitrided powders with crystallite sizes of 10-100 nm and surface areas of 45-370 m(2)/g were produced using these techniques. These ultrafine AlN particles were highly moisture-sensitive, but they could be processed and handled without exposure to air to achieve fully dense materials with low oxygen content.