Combustion Synthesis of AlN Microfibers with Mg Catalyst

PAPER TITLE: Combustion synthesis of AlN microfibers with Mg catalyst

DATE SUBMITTED: September 14, 2016

ABSTRACT:

AlN fiber has the potential to be a superior filler for heat release because of its unique properties of high thermal conductivity, high electrical resistance and low thermal expansion close to Si. However, traditional methods of producing AlN fibers are time consuming and uneconomical. Combustion synthesis (CS), a process utilizing highly exothermic reactions of Al + 1/2N₂ → AlN (ΔH = -318 kJ/mol), has been successfully used to produce high purity AlN. In comparison to conventional methods, this process is energy saving and can be operated at room temperature. In previous works, additives were effective in controlling the AlN product’s morphology, combustion behavior, and reaction mechanism, in which the growth rate of AlN fibers was promoted by the addition of a volatile material. In our study, we investigated the effect of the addition of Mg on the formation of AlN fiber in a pressurized N₂ atmosphere using the CS method. Mg and Al powders were mixed by ball milling and electrically ignited through carbon foil with the igniter of mixed Al and AlN powders. TG/DSC was used to study the reaction mechanism of CS using Mg as a catalyst. The phase purity and morphology of the products after CS was analyzed by XRD and SEM respectively. The resultant products appeared to be white, needle-like fibers composed of mainly AlN with small amounts of Mg-Al alloy. The SEM images and EDS analysis showed that the fibers obtained were approximately 5 µm in diameter and 0.5 cm in length. The results suggest the possibility of innovative AlN fiber production through CS using Mg.