Nanocomposite thermite powders prepared by cryomilling

Reactive nanocomposite materials have been recently prepared by Arrested Reactive Milling (ARM), a method based on mechanical milling of component powders to form micron-sized composite particles where components are mixed on a scale of about 100 nm. The milling temperature affects both the refinement rate and the final product properties. In this paper we report an effort to prepare Al–CuO reactive nanocomposite powders at cryogenic temperatures. The material was processed in a liquid nitrogen bath using steel vials and balls of different sizes as milling media. The number and dimensions of the milling balls as well as the milling time were systematically varied. The products were characterized by X-ray diffraction, particle size analysis, and scanning electron microscopy. Thermal characteristics were studied using a custom wire-ignition setup and differential scanning calorimetry. Results show that the uniformity of mixing and reactivity of the nanocomposite powders can be improved using milling at cryogenic temperatures.