Spontaneous Ignition Temperature and Burning Velocity Just after the Ignition in the SHS Process for Ti-Al System with Rectangular Shape

Abstract

Relevant to materials synthesis by combustion, not only spontaneous ignition of compacted mixture but also flame propagation just after the ignition has been examined for Ti-Al system with rectangular shape. Not only experimental but also theoretical study has been conducted, after confirming that the size ratio, defined as the ratio of compact thickness and particle diameter, can be useful parameters in correlating experimental results. It is found that with increasing size ratio, the spontaneous ignition comes to occur below the melting point of Al (934 K), due to an increase in the particle surface per unit spatial volume of compacted mixture. Effects of mixture ratio and/or degree of dilution on the spontaneous ignition temperature have also been examined. In addition, effects of various system parameters on the burning velocity just after the ignition have been examined. Experimental comparisons with theoretical results have also been conducted and a fair degree of agreement is demonstrated, indicating that the formulations referred to have captured the essential features of the spontaneous ignition of compacted mixture and the SHS flame propagation that passes through it. Since this kind of particle size effect, especially, relevant to the spontaneous ignition and the flame propagation after the ignition, has not been captured in the previous studies, its elucidation can be considered not only notable but also useful, especially, in manipulating combustion process in materials synthesis.