Burning Characteristics of Ammonium Nitrate‐Based Composite Propellants Supplemented with Fe₂O₃

Abstract

Ammonium nitrate (AN)‐based composite propellants have attracted a considerable amount of attention because of the clean burning nature of AN as an oxidizer. However, such propellants have several disadvantages such as poor ignition and a low burning rate. In this study, the burning characteristics of AN‐based propellants supplemented with Fe2O3 as a burning catalyst were investigated. The addition of Fe2O3 is known to improve the ignitability at low pressure. Fe2O3 addition also increases the burning rate, while the pressure exponent generally decreases. The increasing ratio (R) of the burning rate of the AN/Fe2O3 propellant to that of the corresponding AN propellant vs. the amount of Fe2O3 added (ξ) depends on the burning pressure and AN content. R decreases at threshold value of ξ. The most effective value of ξ for increasing the burning rate was found to be 4 % for the propellant at 80 % AN, and the value generally decreased with decreasing AN content. According to thermal decomposition kinetics, Fe2O3 accelerates the reactions of AN and binder decomposition gases in the condensed‐ and/or gas‐phase reaction zones. The burning characteristics of the AN‐based propellant were improved by combining catalysts with differing catalytic mechanisms instead of supplementing the propellant with a single catalyst owing to the multiplicative effect of the former.

Thermal Decomposition Behaviors and Burning Characteristics of AN/RDX-Based Composite Propellants Supplemented with MnO2and Fe2O3

“…The addition of catalyst to the propellant generally decreases the energy density of the propellant, but the burning rate is increased by its catalytic effect. These catalysts improved the thermal decomposition of AN and=or the reaction of the decomposition gases of AN and the binder [9,11], but did not affect the thermal decomposition of RDX. The proportion of AN contained in the propellant decreases with increasing n. Below n ¼ 0.2, the propellant contains a sufficient amount of AN for the catalytic effect, but the burning rate increment is very small, as shown in Fig.…”

“…The increase in the burning rate upon the addition of the catalyst was enhanced with increasing pressure. Furthermore, it increased with increasing AN content, because these catalysts improve the thermal decomposition of AN and=or the reaction of the decomposition gases of AN and the binder [9,11], and the mass fraction of AN in the propellant increases with increasing oxidizer content. As described above, the burning rate of the propellant with Fe 2 O 3 and the bicatalyst at 80% AN had its peak at n of 0.8, because the catalytic effect decreased with increasing n as the mass fraction of AN in the propellant decreases, whereas the effect of the replacement by RDX increased.…”

“…However, for the AN-based propellant with the bicatalyst of Fe 2 O 3 and MnO 2 , the catalytic effect of 151 nm Fe 2 O 3 particles was superior to that of 49 nm Fe 2 O 3 particles, according to Naya and Kohga [12]. The heat release in the vicinity of the burning surface increases and the chemical species are varied by the replacement of AN in the propellant by RDX, compared with the propellant prepared with AN alone as the oxidizer.…”

“…The catalysts were added to a concentration of 4% relative to the propellant, because this value has previously been found to be the most effective for increasing the burning rate [9,11]. The burning characteristics of the AN-based propellant were improved by combining catalysts with differing catalytic mechanisms instead of supplementing the propellant with a single catalyst [11]. For the bicatalyst, both 4% MnO 2 and 4% Fe 2 O 3 were added to the propellant; that is, 8% catalyst was added to the propellant.…”

“…The effect of the addition of a burning catalyst to improve the burning characteristics of AN-based propellants has been investigated [1][2][3][4][5][6][7][8][9][10][11][12]. Oommen and Jain reported that transition metal oxides exhibit a catalytic effect in improving the burning characteristics of AN-based propellants [1] and, more recently, the addition of MnO 2 and Fe 2 O 3 was found to be effective at increasing the burning rate and improving the ignitability at a low AN-based propellant pressure [9,11]. The most effective added amount of these catalysts for increasing the burning rate was found to be 4% relative to the propellant.…”