Ignition characteristics of hybrid Al-Ni-Fe2O3 and Al-Ni-CuO reactive composites fabricated by ultrasonic powder consolidation

Reactive composites of compositions 2Al-Fe2O3-x(Al-Ni), 2Al-3CuO-x(Al-Ni) and 2Al-Al2O3-x(Al-Ni) (x = 1-4) were fabricated from nano-thick Al and Ni flakes and Fe2O3 and CuO nanoparticles by ultrasonic powder consolidation (UPC). Application of in-plane ultrasonic vibration for 1 s at 573 K under a uniaxial pressure of 100 MPa produced full-density consolidates. Upon continuous heating at 125 K/min, the composites began self-heating just before they ignited. The 2Al-Fe2O3-1 (Al-Ni) and 2Al-3CuO-1 (Al-Ni) composites ignited at the melting point of aluminum, but all the other composites ignited well below the melting point, indicating that the reaction(s) between the Al and Ni flakes produced hot spots where liquid formed and triggered the ignition. The hybrid bimetallic-thermite compositions, 2Al-Fe2O3-x(Al-Ni) and 2Al-3CuO-x(Al-Ni), combine the large heat output of the Al-metal oxide thermite reaction and the low ignition temperature of Al-Ni exothermic reactions in single reactive composites. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.