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

Abstract

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 (Ea) 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 $$\left( {f(a) = 2\left( {1 - \alpha } \right)\left[ { - { \ln }\left( {1 - \alpha } \right)} \right]^{1/2} } \right)$$ 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.