COMPARISON OF THERMAL-BEHAVIOR OF REGULAR AND ULTRA-FINE ALUMINUM POWDERS (ALEX) MADE FROM PLASMA EXPLOSION PROCESS

Alex powder (an ultra-fine aluminum powder produced by the plasma-expl osion process) has been shown to be a very effective burning rate enha ncer for solid propellants and fuels. The objective of this research i s to investigate the mechanisms responsible for the beneficial effect of Alex. A TGA and DTA were employed to examine the thermal bahavior o f Alex and regular aluminum particles in different gases. An environme ntal scanning electron microscope (ESEM) was utilized to study the par ticle surface bahavior when samples were heated in air and nitrogen. A transmission electron microscope (TEM) was employed for examining the microstructure of Alex particles. Alex powder was demonstrated in TGA and DTA experiments to behave very differently from the regular alumi num in air, oxygen and nitrogen. Rapid weight gain of Alex particles i n air and nitrogen environment occurred around 548 degrees C and 700 d egrees C, respectively. The low-temperature reaction in air correspond s to an oxidation reaction. Comparing DTA traces of Alex and regular a luminum in air, it was found that oxidation of Alex particles occurs a t a lower temperature with a higher degree of reaction. This is believ ed to be mainly due to the higher reactivity associated with greater s urface area of the Alex particles. In the comparison of DTA traces of Alex and regular aluminum in nitrogen, the rapid nitridation reaction of Alex particles occurs at temperature around 680 degrees C and proce eds to near completion.