Combustion Catalyst: Nano‐Fe2O3 and Nano‐Thermite Al/ Fe2O3 with Different Shapes

Abstract

In order to enable the energetic materials to possess a more powerful performance, adding combustion catalysts is a quite effective method. Granular, oval, and polyhedral Fe 2 O 3 particles have been prepared by the hydrothermal method and used to fabricate Al/Fe 2 O 3 thermites. All the Fe 2 O 3 and Al/Fe 2 O 3 thermite samples were characterized using a combination of experimental techniques including scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and high-resolution TEM (HRTEM). The non-isothermal decomposition kinetics of the composites and nitrocellulose (NC) can be modeled by the Avrami-Erofeev equation f(α)=3(1-α)[-ln(1-α)] 1/3 /2 in differential form. Through the thermogravimetric analysis infrared (TG-IR) analysis of decomposition processes and products, it is speculated that Fe 2 O 3 and Al/Fe 2 O 3 can effectively accelerate the thermal decomposition reaction rate of NC by promoting the O-NO 2 bond cleavage. Adding oxides or thermites can distinctly increase the burning rate, decrease the burning rate pressure exponent, increase the flame temperature, and improve the combustion wave structures of the ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellants. Among the three studied, different shapes of Fe 2 O 3 , the granular Fe 2 O 3 , and its corresponding thermites (Al/Fe 2 O 3 (H)) exhibit the highest burning rate due to larger surface area associated with smaller particle size. Moreover, Al/Fe 2 O 3 (H) thermites have more effective combustion-supporting ability for AP/HTPB propellants than Fe 2 O 3 structures and the other two as-prepared Al/Fe 2 O 3 thermites.

Hydrothermal Synthesis of Hematite Nanoparticles Decorated on Carbon Mesospheres and Their Synergetic Action on the Thermal Decomposition of Nitrocellulose

“…This behavior could be attributed to the autocatalytic parallel reactions, which can generate reactive species that may accelerate the thermolysis and hydrolysis processes [ 67 , 68 ]. As a very strong oxidizing agent, NO 2 stagnates in the polymer skeleton and then reacts with the RO • radicals or their degradation products, causing the opening of the NC anhydroglucopyranose rings to generate other released gases [ 15 , 73 ]. Moreover, the values of E a and log( A ) obtained are within the range of 158.278–176.137 kJ/mol for E a and 15.2281–17.2619 (s −1 ) for log( A ) which correspond to the common rage values of energetic materials [ 14 ].…”

“…Recently, our research group revealed that NC containing Fe 2 O 3 nanoparticles using iron chloride as precursor decomposes following the random nucleation mechanism (Avrami–Erofeev) [ 4 ]. In other works, chemical reaction mechanism has been assumed for pure NC and NC-Fe 2 O 3 composite utilizing iron chloride as precursor [ 14 ], and for NC-Al/Fe 2 O 3 mixture [ 15 ]. More recently, Chellouche et al [ 42 ] attributed a nucleation (parabolic law) for nitrocellulose.…”

“…Various metal oxide NPs have been tested as NC additives. The effect of CuO [ 13 ], Fe 2 O 3 [ 14 , 15 ] nanoboron [ 16 ], bismuth oxide [ 17 ] on the thermal decomposition of nitrocellulose has been assessed and prominent results have been reported.…”

“…For energetic materials applications, α-Fe 2 O 3 nanoparticles have been used to increase the ammonium perchlorate thermal decomposition [ 21 , 25 ]. Zhao et al have confirmed that Fe 2 O 3 nanoparticles may be used safely with NC without affecting the kinetic thermal decomposition model [ 14 , 15 ]. Nevertheless, Fe 2 O 3 reduces the activation energy and critical temperature of thermal explosion of NC and has a good catalytic effect by promoting the O-NO 2 bond cleavage.…”