Thermal decomposition of ammonium perchlorate/exfoliated-graphene and the relationship between activation energy and band gap

ABSTRACT

The thermal decomposition of ammonium perchlorate AP with electrochemically exfoliated graphene flakes (EGF) was studied at different heating rates in nitrogen and the combustion behavior of AP/EGF propellant was evaluated. The exothermic reaction kinetics were studied by simultaneous thermal analysis (STA) in non-isothermal conditions and compare with the thermal decomposition of pure AP applying the same experimental conditions. Using the Kissinger method, the calculated activation energies E_a for the low- and high-temperature exothermic reactions were 87 and 198 kJ/mol for pure AP, contrasting with 91 and 55 kJ/mol obtained from AP with 5 wt% EGF. From our experimental activation energy values together with reported and calculated band gaps E_g, it was found the empirical relationship:

$E_a={E_a}_0-\frac{\left(E_{ac}-E_{a0}\right)}{1+{\left(1.5E_g/E_0\right)}^{n/2}}$

where E_a0 corresponds to the activation energy associated with the high-temperature thermal decomposition of pure AP, E_ac is the activation energy associated to the high-temperature thermal decomposition of AP-EGF, E₀ = 2.7 eV is the catalyst band gap threshold required to activate the electron transfer mechanism and n = 6 is the exponential factor associated to pure AP.

KEYWORDS:

• Thermal analysis
• Kissinger method
• thermal decomposition
• ammonium perchlorate
• exfoliated graphene
• band gap