Effects of nano-Ag on the combustion process of Al–CuO metastable intermolecular composite

• This work focuses on the fundamental understanding of heat transfer mechanisms.
• The presence of nano-Ag particles improves the heat transfer efficiency.
• A new approach distinguishes conduction from convection in the combustion process.
• Three stages (ignition, acceleration and steady combustion) are observed.

Effects of nano-Ag with high thermal conductivity on the combustion wave behavior of Al–CuO MIC (metastable intermolecular composite) are studied in this paper by incorporating Al–CuO MIC with nano-Ag particles in different weight proportions. The physical and chemical characteristics of Al–CuO MIC are determined using scanning electron microscope (SEM), X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The combustion wave behavior is identified by high-speed video recording (HSVR). The experimental observations confirm that the presence of nano-Ag particles improves the heat transfer efficiency. With nano-Ag increasing from 1 wt% to 10 wt%, the first exothermic peak temperature decreases from 607.8 °C to 567.6 °C, and average combustion speed (ACS) increases at first and then reduces. The most suitable amount of nano-Ag is 2 wt% with the ACS and instantaneous combustion velocity on the order of 954.0 m/s, 1562.5 m/s. Moreover, heat transfer mechanisms in the combustion process of Al–CuO MIC are better understood, especially by distinguishing conduction from convection during the combustion propagation. Furthermore, three stages (ignition, acceleration and steady combustion) of reactive propagation are observed in the combustion process. And the corresponding dominative heat transfer mechanisms in the three stages are conduction, conduction to convection transition, and convection, respectively.