Quasi-aligned AIN nanofibers were formed by the nitriding combustion synthesis according to a unique micro-reactor model. A charge composed of aluminum and aluminum nitride diluent powders (40/60 mol%) with a mixture of yttria and ammonium chloride as additives (5 wt% each) was combusted at low nitrogen gas pressures of 0.25 MPa. The FE-SEM images of as-synthesized AIN product showed the formation of ball-like grains (same shape and size as the original Al reactant) that consisted of a thin surface nitride layer. or crust cover quasi-aligned AIN nanofibers grown in the interior. The cross-sectional view is sea anemone like. Formation of this novel morphology is believed to occur through a two-stage process. The first one occurs at the preliminary stage of the combustion outside Al particles. After the ignition, the heat generated causes the sublimation and dissociation of ammonium chloride into various gaseous species. This effectively interrupts the combustion and slows down the increase of reaction temperature. In addition, yttria interacts with the native oxide layer present on the surface of Al particles and forms a stable Al-N-Y-O crust. The second stage begins by the infiltration of various gaseous species such as HCl(g), NH3(g), and N-2(g) through the crust into the molten Al cores. The "crust-core" systems function as "micro-reactors" where both the nitridation and growth processes occur inside. The molten Al cores are spontaneously halogenated to AlCl3 vapors and the nitridation proceeds by the gas-gas reaction of AlCl3 and NH3/N-2 vapors. The AIN nanofibers are then grown from the vapor phase quasi-aligned inside the micro-reactors by VLS and VS mechanisms.