Effect of premilling Al and CuO in acetonitrile on properties of Al·CuO thermites prepared by arrested reactive milling

Abstract

Thermite powders with molar composition 8Al·3CuO were prepared in two stages by Arrested Reactive Milling (ARM). In the first stage, the starting materials Al and CuO were milled separately in acetonitrile. Composite powders were then prepared in the second milling stage with hexane as process control agent and in the four possible combinations of one, both, or neither starting material being premilled in acetonitrile. Composites were characterized for morphology, size distribution, surface area, and reactive properties at low heating rates (thermal analysis) and high heating rates (ignition). Whether or not CuO was premilled, dense composites formed without premilling of Al. If Al was premilled in acetonitrile, however, loose agglomerates of refined Al and CuO particles formed in the second milling stage. Premilling changed the low-temperature reactions leading to ignition in the 8Al·3CuO thermites. These changes are attributed to increased porosity of the formed composites if aluminum is premilled with acetonitrile. It is shown that greater refinement and lower ignition temperatures are achievable using two-stage milling.