Combustion of aluminum nanoparticles and exfoliated 2D molybdenum trioxide composites

Exfoliated two-dimensional (2D) molybdenum trioxide (MoO3) of approximately 3-4 monolayers in thickness was produced from sonicating bulk MoO3 powder, and then mixed with 80 nm diameter Al nanoparticles to prepare nanoenergetic composites with high interfacial contacts between the fuel and oxidizer. Combustion measurements demonstrated peak pressures as high as 42.05 +/- 1.86 MPa, pressurization rates up to 3.49 +/- 0.31 MPa/mu s, and linear combustion rates up to 1,730 +/- 98.1 m/s, the highest values reported to date for Al/MoO3 composites. TGA/DSC measurements indicate energetic reactions between the Al and 2D MoO3 sheets occur prior to the melting temperature of Al. SEM and TEM analysis of the composites prior to combustion suggests high interfacial contact area between the Al and MoO3. After reaction, we observe that the 2D MoO3 sheets are converted to extended alumina flakes during reaction in a process attributed to Al adsorption and diffusion processes. These alumina features 'act as a physical barrier against Al NP sintering while also provide separation for reaction gases to flow and preheat unreacted materials. (C) 2017 Published by Elsevier Inc. on behalf of The Combustion Institute.