Effect of CuO on the thermal kinetics and combustion properties of Al/MoO3 thermite prepared by ball milling

To explore the influence of CuO additive on the thermal kinetics and combustion performance of thermite, Al/MoO3 thermite composites with different mass fractions of CuO were prepared by ball milling. Field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), and differential scanning calorimeter (DSC) were used to test the samples. From the DSC results, Al/MoO3 thermite and Al/CuO thermite released 1066 J/g and 849 J/g heat, respectively. The peak temperature of the exothermic reaction was 560.22 degrees C and 609.43 degrees C. Interestingly, the Al/MoO3 thermite with 5% CuO released higher heat, about 1747 J/g. The temperature of the exothermic peak was also greatly advanced to 526 degrees C. Thermodynamic analysis results showed that the activation energy (Ea) of Al/MoO3/5% CuO thermite was merely 184.75 kJ mol(-1), which was a decrease of 18.3% and 20.8% of the Al/MoO3 and Al/CuO thermite. The reaction mechanism function of Al/MoO3 thermite, Al/MoO3/5% CuO and Al/CuO thermite can be set as f(alpha) = 1 - alpha. The fast electric heating wire ignition experiment showed that the flame brightness of the Al/MoO3/5% CuO thermite was the brightest and the burning time was the longest. Surprisingly, when the mass fraction of CuO additives in Al/MoO3 thermite reached 10% and 20%, the thermal kinetics and combustion performance of the thermite were completely changed. There was a violent and sharp exothermic peak accompanied by a large amount of heat release of 2042 J/g and 2252 J/g, respectively. The reaction mechanism of Al/MoO3 thermite with 10% and 20% CuO addition can be set as f(alpha) = 3/2*(1 - alpha)[-ln(1 - alpha)](1/3). The burning speed became faster and the flame was bright with sparks. This work lays the foundation for the further study of the thermite mechanism.

Automated summary

The addition of CuO significantly increases the heat release and decreases the exothermic peak temperature of Al/MoO3 thermite, but when the mass fraction of CuO reaches a certain level, violent explosion reactions occur.