Combustion Of Ammonium Perchlorate Research Articles

High-performance ammonium perchlorate propellants enabled by ferrocene-functionalized carbon nanotube catalysts

Ferrocene-based burning rate catalysts (BRCs) are essential for controlling the combustion of ammonium perchlorate (AP)-based composite solid propellants. However, their efficacy is often limited by migration during storage, leading to performance degradation. This work reports a novel class of covalently grafted ferrocene-functionalized multi-walled carbon nanotubes (CNT-Fc-n, n = 1, 2, 3) exhibiting enhanced catalytic activity and anti-migration properties. Structural characterization confirmed successful functionalization, while electrochemical analysis revealed facilitated electron transfer during AP decomposition due to π-π conjugation within the CNT-Fc-n structure. Consequently, CNT-Fc-n catalysts significantly reduced the AP decomposition activation energy, with CNT-Fc-3 (highest ferrocene loading) demonstrating the most pronounced catalytic effect. Specifically, CNT-Fc-3 lowered the AP decomposition temperature by 103 °C and 39 °C compared to pure AP and Catocene-catalyzed AP, respectively. Kinetic analysis revealed a 28-fold increase in the rate constant for CNT-Fc-3 catalyzed AP decomposition compared to pure AP. Moreover, the unique architecture of CNT-Fc-3 significantly reduced migration during a 50 °C simulation. This work presents a promising strategy for developing high-performance, migration-resistant BRCs for next-generation solid propellants.

The potentials of copper chromite nanoparticles on ammonium nitrate decomposition: Towards eco-friendly oxidizers for green solid propellants

Abstract Ammonium perchlorate (AP) is the universal oxidizer for solid propellants; AP combustion is accompanied with the release of white smoke (HCl). HCl has raised an environmental concern; it could cause acidic rain and deteriorate the fertile soil. Chlorine free and eco-friendly oxidizers are highly appreciated for green solid propellants. Ammonium nitrate (AN) could be the greener substitute for AP; yet AN expose low performance. Whereas AP demonstrated exothermic decomposition with the release of -733 J/g; AN demonstrated strong endothermic decomposition process of +1707 J/g. AN with strong endothermic decomposition process could render high burning rates. Copper chromite Nano catalyst of 45 nm was developed via hydrothermal synthesis. Copper chromite was integrated into AN matrix. Catalyzed AN demonstrated advanced exothermic decomposition enthalpy of -1492 J/g. Catalysed AN experienced diminish in activation energy by - 41.5 %, and – 40.6 % using Kissinger and Ozawa models respectively. Copper chromite NPs could secure novel catalytic effect via condensed phase reactions of chromium, and copper ions with nitrate ions (NO-3) to develop NOx gases. This catalytic effect can secure alternative pathway with low energy barrier. Consequently, catalysed AN can expose novel characteristics as a green eco-friendly oxidizer.

Combustion of ammonium perchlorate fo near adiabatic condition at high pressures and elevated Initial temperature

AbstractThis paper addresses the combustion of ammonium perchlorate (AP) near adiabatic conditions at high pressures and higher initial temperatures. The AP pellets were coated with a thin layer of silica grease to simulate the near adiabatic condition. The experiments were performed at initial temperatures of 30 and 70 °C in the pressure range of 2.5–30 MPa for coated and bare pellets. The bare pellets were found to exhibit mesa burning as reported in the literature. However, the coated pellets did not exhibit mesa burning. The burn rates of coated AP pellets increased linearly for the entire pressure range of 2.5–30 MPa with 0.64 pressure index. Further, the experiments were carried out for the first time at an initial temperature of 90 °C for 14–30 MPa pressure range, wherein, AP combustion did not display any characteristics of mesa burning (pressure index of 0.33). The surface morphology of quenched samples of both bare and coated pellets of AP were studied, by quenching (rapid depressurization technique) pellets at 6, 12, and 18 MPa pressures. The surface structure of quenched samples for near adiabatic conditions was similar for all three pressures. However, for bare pellets the changes in surface structure were observed with change in pressure, similar to the literature. Mesa burning was found to be an effect of convective heat loss from the periphery of the pellets and it was not observed when heat loss was reduced or initial temperature was higher than the critical initial temperature.

MOF-74 derivatives spinel CuCo2O4/C with d-band center modulation for accelerating ammonium perchlorate thermolysis

As one of main components of solid propellant, ammonium perchlorate (AP) shows slow sluggish decomposition kinetics with unconcentrated heat release. In the past, researchers have done a lot of work using spinel oxides as combustion modifiers to improve the combustion performance of AP. However, AP decomposition process is very complicated, and the relationship between intrinsic activity of cobalt-based spinel catalysts and AP combustion process is still unclear. In this paper, a series of cobalt-based spinel structure catalysts, MCo2O4/C, were prepared by pyrolysis of cobalt-containing bimetal MOF-74 and used as AP combustion catalysts. All of them showed excellent catalytic performance, among which CuCo2O4/C had the best catalytic activity. It effectively reduces the activation energy of the reaction, speeds up the reaction rate, and reduces the peak temperature of the AP decomposition reaction by 161.2 ℃, and the reaction rate k is 10.28 times of Co3O4/C. XPS and NH3-TPD tests indicate that substitution CoTd2+ with Cu2+ increases the ratio of Co3+/Co2+ and enhance interaction between NH3 and catalyst. The essential reason is that Cu–O-Co corner sharing effect changes electron distribution and enhances CoOh3+ Lewis acidity accompanied with the proximity of d-band center to EF by density functional theory calculations.

Kinetic Parameters Governing the Rapid Pyrolysis Of Ammonium Perchlorate

Ammonium Perchlorate (AP) has been in use in many solid propellant formulations since decades. However, data regarding the chemical reactions taking place in the condensed phase during combustion of AP and their associated kinetic parameters are sparse. This data is crucial in modelling the combustion of AP. To mimic the behaviour of AP in condensed phase during its combustion, it is necessary to isolate the condensed phase reactions and study pyrolysis of AP at heating rates similar to those observed during combustion (~105K.s-1). In the current study, an electrical fast pyrolyser coupled to a Fourier Transform Infrared (FTIR) spectrometer was used to study the fast pyrolysis of AP. Activation energy (Ea) of the global pyrolysis reaction was extracted from the variation of mole fraction with time of the observed pyrolysis products. An activation energy of 48 kJ.mol-1 was obtained along with a pre-exponential factor (A) of 4039 s-1. The value of activation energy obtained in the current study is significantly different than that obtained from Thermo-Gravimetric Analysis (TGA) studies. This signifies that the mechanism of decomposition during rapid pyrolysis maybe different from that occurring during slow pyrolysis.

A revised model of ammonium perchlorate combustion with detailed kinetics

In this study, we propose a revised coupled combustion model for ammonium perchlorate (AP), leveraging recent advances in the modeling of ammonia and NOx chemistry. A coupled combustion model relies on three founding bricks: a detailed gas-phase kinetic model, a condensed-phase decomposition model, and a pyrolysis law describing the relationship between the surface temperature and mass flow. The proposed gas-phase kinetic model, is validated against data on species sampling in jet-stirred reactors, laminar flame speed, and ignition delay time. These test cases, rarely used by the solid propellant community, highlight deficiencies in a reference mechanism from the literature. A new model for AP decomposition in the condensed phase is proposed to be used with the gas-phase mechanism. A suitable pyrolysis law is designed using the Zel’dovich–Novozhilov theory to ensure the stability of the coupled combustion model. The methodology employed is described in detail, for others to replicate. Finally, the overall model is applied to simulate the AP laminar flame in a 1D coupled approach. These calculations provide results on the regression rate, surface temperature, temperature sensitivity and species profiles for prescribed initial temperature of AP and ambient pressure. The behavior of the proposed combustion model is presented in comparison with other reference models. The role of gas-phase kinetics in modeling AP combustion is discussed.

Micro-aluminum powder with bi- or tri-component alloy coating as a promising catalyst: Boosting pyrolysis and combustion of ammonium perchlorate

A novel design of micro-aluminum (μAl) powder coated with bi-/tri-component alloy layer, such as: Ni–P and Ni–P–Cu (namely, Al@Ni–P, Al@Ni–P–Cu, respectively), as combustion catalysts, were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate (AP) at a lower temperature in aluminized propellants. The microstructure of Al@Ni–P–Cu demonstrates that a three-layer Ni–P–Cu shell, with the thickness of ∼100 nm, is uniformly supported by μAl carrier (fuel unit), which has an amorphous surface with a thickness of ∼2.3 nm (catalytic unit). The peak temperature of AP with the addition of Al@Ni–P–Cu (3.5%) could significantly drop to 316.2 °C at high-temperature thermal decomposition, reduced by 124.3 °C, in comparison to that of pure AP with 440.5 °C. It illustrated that the introduction of Al@Ni–P–Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol. The laser ignition results showed that the ignition delay time of Al@Ni–P–Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni–P/AP (118 ms), decreased by 33.90%. Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions (7597.7 J/g) of Al@Ni–P–Cu, resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion. Moreover, it is believed to provide an alternative Al-based combustion catalyst for propellant designer, to promote the development the propellants toward a higher energy.

Embracing Anisotropy – Opportunities and Challenges to the Functional Application of Advanced Manufacturing of Energetic Materials

Embracing Anisotropy – Opportunities and Challenges to the Functional Application of Advanced Manufacturing of Energetic Materials

Defective-activated-carbon-encapsulated Co as a super reactive catalyst for combustion of ammonium perchlorate

Defective-activated-carbon can serve as both fuel and combustion catalyst for ammonium perchlorate (AP) based energetic composites owing to the promoted reactivity and catalytic activity. However, the poor ability of carbon materials in accelerating the electron transfer in the secondary reaction of HClO4 decomposition hinders their applications in composite solid propellant. Herein, a hybrid with metallic Co nanoparticles encapsulated in N-doped defective activated carbon (denoted as DAC/Co) is reported to achieve bi-functional additives with simultaneously high catalytic activity and high reactivity. The DAC with high defect can not only serves as fuel due to its high reactivity, but also favors the proton transfer in the initial decomposition of AP owing to its rich defects. Moreover, the combination of the Co nanoparticles and DAC is also beneficial to electrons transfer in the secondary decomposition of AP, leading to a high catalytic activity for thermal decomposition of AP. As a result, the AP/DAC/Co-20 composite possesses a greatly enhanced combustion performance, with the combustion duration shorten by 107 ms compared to that of AP/DAC (348 ms) and pressurization rate increase by 9.8%. The present work demonstrates the feasibility of DAC/Co hybrid for practical applications in AP based solid propellant.

Defect-engineered sp2 carbon as highly active catalyst and reactive fuel for combustion of ammonium perchlorate

Defect engineering is a vital technique to modulate the properties of carbon nanomaterials. The unique advantage of intentionally introducing intrinsic defects and heteroatom dopants in sp2 C–C bond framework is to increase the active sites, optimize the adsorption/desorption behavior of the reaction intermediates, and alter the surface charge transfer properties of various electrochemical systems. Herein, a defects and bonding disorder regulation strategy is reported to enhance both catalytic activity and combustion reactivity of sp2 carbon toward the thermal decomposition and combustion of ammonium perchlorate (AP), which is the key reaction of modern solid propellants in aerospace field. A layered defect-rich carbon (LDC) has been prepared by inlayer carbonization of graphite-like 1,3,5-Triamino-2,4,6-trinitrobenzene (TATB) crystals. The intentionally designed LDC with rich intrinsic defects and N dopants provides abundant active sites for adsorption of AP decomposition intermediates, which facilitates efficient charge transfer in rate controlling steps. Moreover, the LDC with high bond disorder can react with AP as fuel with high reaction kinetics. As compared to other carbon materials with different bonding disorder and defects, this highly reactive catalyst greatly enhances the combustion performance of AP/LDC composites in terms of more complete chemical energy release (increased combustion pressure) and enhanced reaction kinetics (increased burning rate). The defect engineering provides an effective way to activate the inert sp2 carbon materials to efficient combustion catalysts and highly reactive fuels for AP based solid propellants.

Effect of metal additives on neutralization and characteristics of AP/HTPB solid propellants

Conventional ammonium perchlorate (AP) based solid propellant system has been used in rocket boosters and most tactile missiles. But the toxic chloride emissions from the combustion of AP during the rocket launch increase the air pollution by 1%. For the conversion of conventional AP based propellant into Green propellant there approaches can be used. These are scavenging propellants, Neutralizing propellants and Non-chlorine propellants. In present study an attempt is made to investigate the characteristics of neutralizing propellant with the help of different metal additives such as Al, Mg, and combined Al–Mg. The investigations were theoretically and experimentally carried out and the results compared with base composite solid formulation (AP/HTPB). Theoretical investigation on that addition of metal additives clearly indicated helps in the reduction of toxic HCl without the compensation of performance. The burn rate study was carried out using Crawford strand burner setup in inert atmosphere under different pressure conditions ranges from 0.689 MPa to 4.136 MPa. A considerable enhancement in the burn rate of AP based solid propellant by 14.02% using pure metals as additives and by 54% using binary metal mixtures as additives was observed. Studies on HCl reduction of AP based propellant samples using gas bubbling setup shows that addition of Mg-15% to the base propellant enhances the HCl reduction by 47% but the propellant was porous in nature and addition of Al–Mg(15%) to the base propellant enhances the reduction by 37%. Thus, the binary metal mixtures in AP/HTPB based solid propellant resulted in better reduction of toxic HCl without reduction in performance than the sample without metal additives.

Response function of ammonium perchlorate monopropellant

Response function of ammonium perchlorate (AP) has been studied. An unsteady model of AP combustion has been used based on the recent experimental findings reported. The key findings of this work are the good comparisons with experimental results, which until date had not been predicted accurately. Variation of thermal properties as a function of temperature in the condensed phase predicted the experimental data better.

Catalytic decomposition mechanism of aqueous ammonium dinitramide solution elucidated by thermal and spectroscopic methods

Ammonium dinitramide (ADN) is a green, energetic and oxygen rich molecule, developed to replace the commonly used oxidizer ammonium perchlorate (AP). On combustion ADN produces relatively environmental-friendly species such as H2O, NO2, N2O, NO etc., compared to HCl, Cl2, CO2, CO, H2, H2O, N2 and highly reactive chlorine species produced by AP combustion. The ADN synthesized in our laboratory was dissolved in deionized water to prepare aqueous ADN solutions (aq. ADN). The thermal decomposition of solid ADN and aq. ADN were studied and the products of decomposition are identified using a thermogravimetric analyser hyphenated with a FTIR instrument. Nano CuO catalyst was synthesized and aq. ADN was decomposed over the nanocatalyst and the catalytic decomposition mechanism is also elucidated. The study shows that, the condensed phase decomposition of aq. ADN is influenced by the CuO nanocatalyst leading to the generation of higher concentrations of NO2, which autocatalyzes the remaining ADN decomposition.

Effect of ageing on combustion of ammonium perchlorate with copper chromite additive

Ageing is an irreversible process during which, the material undergoes a series of slow chemical degradation/oxidation reactions. The aim of this paper is to study the effect of ageing of ammonium perchlorate-copper chromite (AP-CC) pellets on the burn rate. It also focuses on any change in CC properties due to direct contact with an oxidizer (AP). Accelerated ageing with cyclic temperature profile has been used to replicate the natural ageing. The effect of ageing of individual ingredients on the burn rate was studied. The burn rate of AP-CC pellets was found to reduce when AP-CC were aged together. X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS) analysis were used to identify the change in properties of copper chromite during ageing.

Electrospun copper oxide nanofibers and catalysis for combustion of ammonium perchlorate

Copper oxide (CuO) nanofibers were successfully prepared by electrospinning and subsequent heat treatment. The chemical composition and morphology of the fibers were characterized by SEM, XRD and EDS. Beaded nanofibers with 100nm in diameter were prepared by simple electrospinning and calcining. The catalytic effect of CuO nanofibers on the combustion of ammonium perchlorate (AP) was investigated by TG and DTA. The results showed that the decomposition temperature of AP shifted by 101.9 °C to the low temperature and the catalytic efficiency was very high. This is mainly attributed to the higher surface to volume ratio of beaded copper oxide nanofibers compared with smooth nanofibers and spherical nanoparticles. The results suggest that the electrospinning of CuO nanofibers is a promising one-dimensional nanometer material in the field of propellant catalysis.

Combustion of Ammonium Perchlorate monopropellant: Role of heat loss

The combustion characteristics of Ammonium Perchlorate (AP) monopropellant have been revisited. The use of silica grease to prevent heat loss from the sides of the pellet and the ignition methodology opened up new area; one of them being the low pressure deflagration limit (LPDL) of AP itself and the other being the burn rate of AP at different pressures. The new burn rate law for pure AP was obtained for conditions close to adiabatic. Using slow depressurization method, wherein the LPDL was independent of ignition transients, the LPDL of pure AP was found to be 14 bar The burn rate of pure AP at 70 bar was found to be 10.66 mm/s, which was much higher than the ones reported in literature. The pressure index for this case was found to be 0.71. This new result completely changes the understanding of AP combustion and called for a new set of parameters to be developed to predict the results obtained with silica grease on the sides. Using the same set of parameters, along with a heat loss model the predictions for the case when there was no silica grease applied was made. These results were in reasonable agreement with the experimental data reported in literature without the silica grease on the sides of the AP pellet. This brings out the critical role of heat loss in AP combustion.

Moving boundary modeling for solid propellant combustion

Moving boundary problem frequently occurs in chemical engineering to describe various problems when the boundaries to describe domain keep changing. Combustion of solid propellant is a notorious example, which involves three phases (solid, condensed, and gas phase) and the positions of the interface between phases change in relation to the state of phases. In this study, moving boundary modeling approach was suggested to develop a rigorous mathematical model of solid propellant combustion. The mathematical model of a solid propellant was divided into three sub-models for each phase, which include conservation equations (mass, energy, and momentum conservation) and constitutive equations within the framework of moving interface. Coordinate transformation was carried out to achieve a fixed interface formulation from the moving interface problem, which leads to a fixed domain of each phase ranging from 0 to 1.In order to validate the feasibility of this approach, the mathematical model for the combustion of ammonium perchlorate was developed and dynamic simulation was performed with various operating conditions. The simulation results, including burning rate, temperature, mole fraction, and phase thickness, were compared with various reference data. Based on the comparison, it was concluded that the suggested moving boundary modeling approach can be used for the combustion of solid propellant and can accurately predict dynamic behaviors of the combustion.

Study of aluminum particle combustion in solid propellant plumes using digital in-line holography and imaging pyrometry

The combustion of molten metals is an important area of study with applications ranging from solid aluminized rocket propellants to fireworks displays. This work uses digital in-line holography (DIH) to experimentally quantify the three-dimensional position, size, and velocity of aluminum particles during combustion of ammonium perchlorate (AP) based solid-rocket propellants. In addition, spatially resolved particle temperatures are simultaneously measured using two-color imaging pyrometry. To allow for fast characterization of the properties of tens of thousands of particles, automated data processing routines are proposed. Using these methods, statistics from aluminum particles with diameters ranging from 15 to 900 µm are collected at an ambient pressure of 83 kPa. In the first set of DIH experiments, increasing initial propellant temperature is shown to enhance the agglomeration of nascent aluminum at the burning surface, resulting in ejection of large molten aluminum particles into the exhaust plume. The resulting particle number and volume distributions are quantified. In the second set of simultaneous DIH and pyrometry experiments, particle size and velocity relationships as well as temperature statistics are explored. The average measured temperatures are found to be 2640 ± 282 K, which compares well with previous estimates of the range of particle and gas-phase temperatures. The novel methods proposed here represent new capabilities for simultaneous quantification of the joint size, velocity, and temperature statistics during the combustion of molten metal particles. The proposed techniques are expected to be useful for detailed performance assessment of metalized solid-rocket propellants.

Modeling of burning rate equation of ammonium perchlorate particles over Cu–Cr–O nanocomposites

The present study is aimed at introducing the application of design of experiment (DOE) with artificial neural networks (ANN) in couple over Cu–Cr–O nanocomposites, which can be used as catalysts in the combustion of ammonium perchlorate (AP), as well as a method of data collection/fitting for the experiments. To this end, a practical scheme has been proposed to select the characterization parameters of Cu–Cr–O nanocomposites as the catalytic combustion of AP propellant. Moreover, a calculation model has been established to identify the primary combustion characteristics based on backpropagation neural networks. The model was subsequently validated and then used to predict the primary combustion characteristics of the aforementioned propellant. In addition, due to the complex nature of the system, neural networks were employed as an efficient and accurate tool to model the behavior of the system. Response surface methodology (RSM) and ANN methods were also constructed based upon the DOE’s points and were then utilized to generate extra simulated data. The data sets, including the original experimental data and the simulation results yielded by the ANN and RSM methods were subsequently used to fit the combustion rate expression for AP. A comparison of the results of kinetic modeling with the simulated data sets from ANN and RSM models was then made, which indicated that both methods could satisfactorily fit the experimental data presented in the literature. The results also revealed that the error of burning rate calculation is less than ±5 % and the variations of the calculation results were consistent with those of the experimental results.

Mechanisms of combustion catalysis by ferrocene derivatives. 1. Combustion of ammonium perchlorate and ferrocene

Combustion of ammonium perchlorate (20–90%) mixtures with ferrocene is studied. It is demonstrated that, depending on the ratio of the components in the examined compositions, in addition to the usual gas-phase combustion model, another possible combustion mechanism exists. A somewhat unusual condensed-phase (c-phase) model may be realized, in which the heat-generating reaction occurs in a foam/aerosol layer at the temperature of evaporation of the less volatile component, which the surface temperature is defined by evaporation of the more volatile component. The efficiency of ferrocene depends on the propellant combustion mechanism: in systems that obey the gas-phase combustion mechanism, the influence of ferrocene addition is higher than the influence of addition of a hydrocarbon fuel; in systems with the c-phase mechanism of combustion, ferrocene addition produces a significant effect. Depending on the ratio of the components, ferrocene first acts in these compositions simply as a highly reactive fuel; it is only in fuel-enriched compositions with a high equivalence ratio that the burning rate increases owing to catalysis of the combustion process by the ferric oxide on the soot skeleton.