The catalytic effect of Ag/CNTs nanocomposite on the ignition reaction of Mg/KNO₃ pyrotechnic by determination of the kinetic triplet

The ignition reaction of Mg/KNO₃ was improved with addition of Ag/CNTs nanocomposite as catalyst. The nanoparticles of Ag(0) was deposited on the multi-walled carbon nanotubes (CNTs) using NaBH₄ as reducing reagent. The prepared catalyst was analyzed using X-ray diffraction pattern, field emission-scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS) and Brunauer–Emmett–Teller method. The differential scanning calorimetry (DSC) curves of Mg/KNO₃ and Mg/KNO₃/Ag/CNTs pyrotechnic were studied at heating rates of 5, 10, 15 and 20 °C min⁻¹ under nitrogen atmosphere. The shift of the temperature of exothermic peak to lower temperatures and increasing of enthalpy of ignition reaction of Mg/KNO₃ pyrotechnic was seen in DSC curves in presence of Ag/CNTs catalyst. The activation energies (E_a) of ignition reaction of Mg/KNO₃ and Mg/KNO₃/Ag/CNTs pyrotechnics were calculated 172–186 and 152–165 kJ mol⁻¹, respectively, using the free-model methods of Kissinger, Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose. Also the pre-exponential factor (A) and kinetic model function of ignition reaction of pyrotechnics were determined by the compensation effect and nonlinear model fitting method. The values of pre-exponential factor were obtained 2.9 × 10¹² and 1.1 × 10¹⁰ min⁻¹ for the ignition reaction of Mg/KNO₃ in absence and in presence of catalyst of Ag/CNTs, respectively. The mechanism functions of Avrami–Erofeev A₂$\left(f\left(a\right)=2\left(1-\alpha \right){\left[-\ln \left(1-\alpha \right)\right]}^{1/2}\right)$ and A₃$\left(f\left(\alpha \right)=3\left(1-\alpha \right){\left[-\ln \left(1-\alpha \right)\right]}^{2/3}\right)$ were found to be the best pattern for ignition reaction of Mg/KNO₃ and Mg/KNO₃/Ag/CNTs pyrotechnics, respectively.