Ignition performance and mechanism of Ti/CuFe2O4 composites with high microwave sensitivity

Abstract

The microwave ignition holds potential in the ignition of weapons due to its simple structure, non-contact property, and simultaneous ignitions of large area. However, the long ignition delay time of the current ignition agents cannot meet the microwave weaponry advancements. To address the issues, a microwave sensitive oxide-CuFe2O4 (CUFO) which was firstly discovered to be easily ignited by microwaves compared many ferrites, was coupled with Ti nanoparticles (n-Ti) to form Ti/CUFO microwave ignition agents by electrostatic spray granulation. The characterization of microwave ignition, volumetric combustion, burning rate and DSC were used to determine its ignition delay time and the energy release properties. It indicates that the microwave sensitivity, maximum peak pressure and pressure pressurization rate of Ti/CUFO first increases and then decreases with the promoting content of n-Ti. The Ti/CUFO at Φ = 3.5 exhibits the lowest ignition delay time by 79.24 ms compared to the 98.7 ms of n-Ti, meanwhile, its maximum peak pressure and pressurization rate reach the highest by 338.54 kPa and 8.57 kPa/ms, respectively. The DSC results indicate that Ti/CUFO exhibits much lower reaction peak temperature by 320–335 °C compared to 488 °C of n-Ti, which suggests Ti-CUFO reaction maybe much easier be activated. The dielectric loss of n-Ti and CUFO under strong electric field transfer the energy of microwaves to heat, reaching to its reaction temperature. The XPS and XRD results of CUFO after microwave radiation disclosing the crystal transition, formation of divalent iron and oxygen vacancies, as well as the released bright light under microwave radiation, suggest the thermal breakdown mechanism of CUFO. When Ti/CUFO exposes into microwaves, CUFO generates oxygen vacancies due to heat loss and n-Ti is dielectric heated, followed by the generated oxygen reacting with n-Ti, improving the combustion performance of n-Ti. This result provides new insight for the designing of microwave ignition.