Decomposition Of Propellants Research Articles

Thermal decomposition kinetics and storage life prediction of nitramine propellants with different energetic plasticizers based on model-fitting method

The research on the thermal decomposition of propellant is critical to determining its safe storage life. The thermogravimetry (TG) testing of nitramine propellants plasticized by nitroglycerin (NG), glycidyl azide polymer (GAP), 2,2-dinitropropanol hexanoate (DNPH), and N-butyl-2-nitratoethylnitramine (BuNENA) was performed under non-isothermal circumstances. The thermal decomposition mechanism of propellant was then analyzed using the model-fitting method, and the storage life was predicted based on the mechanism. The results show that when heated to the same mass loss, the temperature of GAP-NC-RDX, BuNENA-NC-RDX, and DNPH-NC-RDX is higher than that of NG-NC-RDX. GAP-NC-RDX, BuNENA-NC-RDX, and DNPH-NC-RDX propellants have superior thermal stability to that of NG-NC-RDX. The kinetic mechanism functions and equations of the propellants were calculated, and multi-step reaction models of the thermal decomposition were built. The major thermal decomposition mechanism of nitramine propellants was discovered to be composite autocatalytic decomposition (Kamal-Sourour equation), which means that the reaction of reactants and the reaction catalyzed by products occur in tandem. The decomposition depth of propellants increases as the temperature rises during the same storage time. The storage lifetimes of GAP-NC-RDX, BuNENA-NC-RDX, DNPH-NC-RDX, and NG-NC-RDX propellants at 288 K are 28.71 years, 24.49 years, 18.34 years, and 16.33 years, respectively. The inclusion of GAP, DNPH, and BuNENA in the formulation improves the storage life of propellant more than NG. This study offers an attractive strategy for analyzing the decomposition mechanism of propellant with a multi-step decomposition reaction and forecasting its storage life.

Insights into the Fragmentation of Aluminum Hydride and Its Effect on Combustion and Agglomeration of HTPB Propellant.

AlH3 has gained considerable attention as a fuel additive due to its ability to offer high specific impulse and superior combustion performance. However, few studies have focused on the fragmentation and agglomeration behavior of AlH3. This study investigated the effects of fragmentation of AlH3 and AlH3/PVDF particles on the thermal decomposition, ignition, agglomeration, and combustion of HTPB propellants. Thermal analysis indicated that AlH3 and AlH3/PVDF can accelerate the decomposition of ammonium perchlorate by abundant active sites for the adsorption of the decomposition intermediates. Single-particle combustion uncovered the mechanism behind the directional spray of molten Al from the AlH3 particle and the fragmentation of the AlH3/PVDF particle. The melting of porous Al induces particle shrinkage due to solid-liquid interfacial tension and the structural restoration of the oxide shell, which consequently results in the sealing of cracks in the oxide shell of AlH3. Additionally, the accumulation of internal tensile stress leads to the reopening of these cracks and the directional ejection of the molten Al. The flexible oxide shell contributes to a smaller minimum normalized diameter of the AlH3/PVDF particle, aiding in the generation of internal tensile stress, while the sublimation of AlF3 induced the fragmentation. Synchrotron-based X-ray imaging revealed the formation of aggregates promoted by molten Al, the splitting of AlH3 aggregates due to hydrogen explosion, and the enhanced fragmentation of AlH3/PVDF due to the synergistic effect of hydrogen explosion and the sublimation of AlF3. Compared to raw particles, the CCPs (condensed combustion products) of SP2 propellant display a 48% reduction in average size (D50 = 24.5 μm), whereas there is an over 89% decrease in particle size for the CCPs of SP3 propellant (D50 = 5.14 μm). This study contributes to understanding the fragmentation of AlH3 and AlH3/PVDF upon ignition and combustion, providing valuable insights for the development and optimization of propellants containing AlH3.

Modified Arrhenius kinetics for double base propellant decomposition: Effect of water

Numerous studies have been conducted on the decomposition mechanisms of cellulose nitrate (NC), a polymer employed in double base (DB) rocket propellants. It is well known that storage temperature affects the lifetime of these energetic formulations. However, less studies have been published on the influence of water. This research examined the role of water on the stabiliser consumption rate during accelerated ageing of a DB rocket propellant, as well as the impact on the shelf life prediction of the energetic formulation. Different volumes of water (0.8, 1.6, 2 and 4 µl/g) were added to the propellant in sealed vials, which were then isothermally aged (70, 80, 90, 100 °C). Analyses of the stabiliser consumption showed a faster decomposition kinetics in presence of water which is indirectly linked to the shortening of the storage life of the NC based propellant by 35 %. For the conditions, an activation energy of 133 ± 4 kJ/mol was reported for the water catalytic decomposition mechanism. A numerical model that included water as a variable was reported to reduce the uncertainty in the determination of the service life of NC based propellant. International standards such as Allied Ordnance Publication 48 should not overlook the effect of water/moisture on the safety of ammunition containing NC and should implement a modified Arrhenius equation.

Impacts of metal oxide crystalline structure on the decomposition of solid propellants under combustion heating rates

Ammonium perchlorate (AP) has been the oxidizer of choice for composite solid propellants for decades and has been the object of decomposition studies for safety monitoring. Typically, studies perform differential scanning calorimetry (DSC) or thermogravimetric analysis (TGA) to show how metal oxides (MO) commonly incorporated into propellants alter AP decomposition rates and completeness of reaction. Most past decomposition work studies temperatures below the crystal phase transition (240°C) from orthorhombic phase to cubic, which impose internal stresses within the lattice of AP particles. Phase change induces a partial decomposition, which does not follow a shrinking core behavior; instead, it develops a network of pores up to a few microns in size throughout. During low-temperature decomposition, particles lose approximately 30-40 % of their mass. Simultaneous DSC/TGA (STA) use low heating rates for combustion environments but offer information on MO's catalytic and electron transport modifications. This work demonstrates how the crystalline morphology MO additives mechanistically alter the combustion properties of composite propellants by identifying modes for promoting decomposition in AP and HTPB. MO morphology determines the electron structure of the molecule, which sets the band gap properties of the particles. This study evaluated different morphologies and a range of MOs to identify the most active MO for decomposing A.P. Kissinger analysis was applied using STA data at heating rates of 10-, 20-, and 30-°C/min revealing significant shift in the high-temperature decomposition with a range of metal oxides. Higher heating rates were evaluated using CO2 laser ignition to identify the time to first gas using the MO that offers the best heat absorption, such as the aluminum oxides. This higher heating rate was found do more accurately represent the changes in the combustion rates in the final propellant mixture. Additionally, it was shown that electron transport additives like CuO show the most significant impact on combustion, and thermal absorbers offer the lowest impact on AP/HTPB combustion. This understanding offers a new approach to propellant design not previously presented and suggests future testing for tailoring the use of metal oxides in propellants.

Uncovering the decomposition mechanism of nitrate ester plasticized polyether (NEPE): a neural network potential simulation.

Nitrate ester plasticized polyether (NEPE) propellants have attracted widespread attention due to their high energy density and excellent low-temperature mechanical properties. However, little is known about the thermal decomposition process of the NEPE propellant, particularly lacking microscale models and interaction mechanisms. This work aims to establish a high-precision and efficient neural network potential (NNP) model covering the NEPE matrix, describing its mechanical behavior and detailed thermal decomposition mechanisms. The model accuracy, including atomic energies and forces, was validated through density functional theory (DFT) results, and the NEPE propellant decomposition model was verified via molecular dynamics (MD) simulations with DFT precision. The results demonstrate that the NNP model accurately predicts the energies and forces of the NEPE matrix for single and mixed systems at the DFT-level precision, and reproduces the mechanical properties consistent with DFT calculations. Meanwhile, the thermal decomposition order of the NEPE matrix predicted by NNP is consistent with the experimental results, accurately capturing complex physical phenomena and detailed decomposition processes among components. It is also revealed that the addition of a binder can improve the stability of the propellant and extend its energy release time. This study applies innovative machine learning algorithms to develop an NNP computational model for the NEPE matrix with DFT precision, which is crucial for practical propellant formulation design.

Insight into thermal decomposition behavior of ammonium dinitramide‐based liquid propellant through reactive molecular dynamics simulations

AbstractThe thermal decomposition characteristics and fuel oxidation mechanism of ammonium dinitramide (ADN)‐based liquid propellant are of great practical significance, but it is difficult to detect the whole intermediates and products using traditional experimental methods. In this paper, the thermal decomposition of ADN‐based liquid propellant at different temperatures (1500, 2000, 2500, and 3000 K) was simulated using the reactive molecular dynamics method. The effect of temperature on the thermal decomposition of propellant and the distribution of the main products were investigated. The results showed that the temperature played a role in promoting the decomposition of propellant. The main products of ADN‐based liquid propellant were N2, H2O, NH3, HNO3, ⋅NHO, CH2O, CO2, and NO2, while their evolution and generation pathways were also described in detail. The initial decomposition of ADN was the breakage of N−H bonds in ⋅NH4 or N−N/N−O bonds in ⋅N(NO2)2, and methanol generated free radicals by dehydrogenation. There was no direct chemical reaction between ADN and methanol, and the interaction was accomplished through the generation and consumption of free radicals. H2O provided a large amount of ⋅H and ⋅HO leading to a lower activation energy of ADN in propellant than that from reference. The overall reaction mechanism of the liquid propellant was deduced. The results would help to further investigate the reaction mechanism of ADN‐based liquid propellants.

Tunning Combustion Behaviors of Composite Modified Double-Based Propellants with a Novel Energetic Burn Rate Modifier

ABSTRACT The flexible control in burning rate and stable combustion of solid propellants over a broad range of pressures essentially determine the performance of solid rocket motors. The nanoscale metals and their oxides are usually utilized as the traditional burn rate modifiers in adjusting the combustion behaviors of solid propellants, but the energy characteristics of propellants are greatly compromised owing to the inert nature of additives used. In this paper, a series of metal complexes of triaminoguanidine-glyoxal polymer (TAGP-Ms) with high nitrogen content were synthesized and employed as energetic burn rate inhibitors in tunning the combustion properties of composite modified double-based (CMDB) propellants. The influences of prepared TAGP-Ms on the thermal decomposition and combustion of CMDB propellants were comprehensively investigated based on thermal analysis technique and combustion characterization methods. It was found that the peak temperatures of the second exotherm displayed for the propellants containing TAGP-Ms inhibitors were significantly increased by more than 30°C (except for TAGP-Cu), indicating the TAGP-Ms is capable of suppressing the thermal decomposition of CMDB propellants. More importantly, the heat releases of CMDB propellants were substantially enhanced by 16%~34% determined by DSC analysis. In comparison to the blank reference, the energetic TAGP-Ms inhibitors could promote the heat of combustion for the involved CMDB propellants by 5%~9%. The burning rates of CMDB propellants were notably reduced over a wide range of pressures by adding TAGP-Ms, whereas the calculated pressure exponents at pressures ranging from 10 to ~ 22 MPa appear to be relatively high due to the accelerated HMX decomposition. The measured combustion wave temperatures suggest that the CMDB propellants with TAGP-Ms undergo a three-stage combustion process with the highest temperatures in the range of 2160 ~ 2230°C.

Performance of MEMS-Based Monopropellant Microthruster With Insulating Effect

Excessive heat loss in micro scale has been a long-lasting issue, affecting catalyst reactivity particularly for monopropellant thrusters and causing insufficient propellant decomposition. Various MEMS fabrication substrates and technologies were utilized for micro propulsion, but few studies on MEMS-based propulsion have reported their propulsion performance, due to not only insufficient propellant decomposition, but also difficulties of measuring high temperature and pressure in a micro scale chamber. In this work, a microthruster was fabricated using high insulation material (glass) in an optical lithography process of photosensitive glass to suppress heat loss. Chamber temperature and pressure sensing tips were integrated in a MEMS fabrication process, which were essential to evaluating propulsion performance and gaining an understanding of the insulating effects of the material on micro propulsion performance. Experimental test results showed successful propellant decomposition with 78% temperature efficiency, which is one of the highest temperature efficiencies in MEMS-based micro propulsion studies reported. The use of glass as a MEMS fabrication substrate was evaluated favorably through numerical analysis as well, in terms of suppression of thermal energy loss and superior propulsion performance.[2022-0014]

Thermal decomposition and kinetic investigation of AP and AP based composite solid propellant in the presence of nickel ferrite additive

Nanosize nickel ferrite (NiF) with an average crystalline size of 28.6 nm has been successfully synthesized via the co-precipitation method. NiF was found to efficiently reduce the thermal decomposition of ammonium perchlorate (AP) and Composite solid propellants (CSPs) along with an increment in the burning rate of CSPs by 1.6 times. The high-temperature DSC exothermic decomposition peak of AP was decreased by 59.04 °C in the presence of 1% by weight NiF additive. Differential Scanning Calorimeter (DSC) exothermic peak of CSPs based on AP + NiF was decreased by 37.72 °C as compared to that of CSPs based on pure AP. Further, the kinetics parameters of AP and AP + NiF mixture were evaluated using iso-conversional methods. The results indicated that the activation energy the of AP + NiF mixture was increased despite reduction in the thermal decomposition temperature.

Nano Size NiCuZnFe2O4 Tri Metal Spinel Ferrite: Synthesis, Characterizations and Additive for Thermolysis of Ammonium Perchlorate

AbstractFerrites especially transition metal based catalysts show a versatile catalytic ability for thermal decomposition of solid propellants. Herein, XRD, UV‐visible spectroscopy, Raman spectroscopy, and N2‐adsorption desorption analyses were used to analysis trimetallic nano‐ferrite NiCuZnFe2O4 synthesized by co‐precipitation method. The particle size of the NiCuZnFe2O4 found between 9–20 nm. Moreover, we have studied catalytic activity of tri metal ferrite (NiCuZnFe2O4) on thermal decomposition of propellant oxidizer ammonium perchlorate (AP) and monitored by simultaneous thermal analyses. The increased surface area, smaller band gap, and crystalline Raman phase of the AP + NiCuZnFe2O4 mixture contributed to substantial physico‐chemical and catalytic outcomes. The combination of AP with the nano‐catalyst NiCuZnFe2O4 reduced ignition delay, which was ascribed to a lower thermal decomposition temperature.

Thermal Decomposition Kinetics of Potential Solid Propellant Combustion Catalysts Fe(II), Zn(II), Hydroxylammonium, and Hydrazinium Pentazolates

AbstractHerein, we prepared Fe(II), Zn(II), hydroxylammonium, and hydrazinium pentazolates and investigated their thermal behavior, decomposition kinetics, and thermodynamic activation parameters. The thermolysis of metal and non‐metal salts featured three and two mass‐loss stages, respectively, with the decomposition of pentazolate anions occurring at 105–135 °C. Moreover, metal salts exhibited higher thermal safety than non‐metal salts under the same conditions. Iron and zinc pentazolates decomposed at lower temperatures than sodium pentazolate, i. e., Fe(II) and Zn(II) ions promoted the decomposition of pentazolate anions. The obtained results demonstrate that the prepared compounds hold great promise as energetic catalysts for solid propellant decomposition.

Impact of HAN Ternary Propellant System Decomposition on Catalytic Sustainability

AbstractAqueous solution of Hydroxylammonium nitrate (HAN) in combination with a suitable fuel has been explored as a promising high performing green monopropellant in recent times. The current study primarily explores the effect of the addition of a fuel component into HAN solution on the sustainability of a recently developed catalyst which was examined for the only binary system consisting of HAN and water. The HAN ternary system examined was HAN: methanol: water in 70 : 15 : 15 (w/w) composition. The endurance of an ‘iridium over alumina’ catalyst and an indigenously developed cobalt doped ceria‐based catalyst was analysed using a batch reactor wherein a pressure rise during decomposition of propellant whilst a pulse mode operation was monitored. Catalysts were also characterized via SEM/EDS, XRD, and XPS to identify changes over the period of sequential injection in the batch reactor. Doped ceria catalyst was found to be far robust and resistant to any poisoning when compared to iridium catalyst at run time of the operation involving nearly 45 sequential injections of propellant over the catalyst.

Decomposition of Low-toxic Propellant by Cu-La-Al/honeycomb Catalysts

Decomposition of Low-toxic Propellant by Cu-La-Al/honeycomb Catalysts

Study on High Energy Propellant Waste in the Processing of Fired Clay Bricks

Utilisation of propellant waste in fabrication of bricks is not only used as efficient waste disposal method but also to get better functional properties. In the present study, high energy propellant (HEP) waste additive mixed with soil and fly ash in different proportions during manufacturing of bricks has been investigated experimentally. X-ray diffraction (XRD) studies were carried out to confirm the brick formation and the effect of HEP waste. Ceramic bricks were fabricated with HEP waste additive in proper proportions i.e. 0.5 wt %, 1.0 wt %, 1.5 wt %, 2.0 wt %, 2.5 wt %, 3 wt %, 3.5 wt %, and 4 wt % and then evaluated for water absorption capability and compressive strength. Compressive strength of 6.7 N/mm2, and Water absorption of 22 % have been observed from modified fired bricks impregnated with HEM waste additive. Scanning electron microscopy (SEM) studies were carried out to analyze the effect of HEP waste additive on pore formation and distribution in the bricks. Further, the heat resulting from decomposition of propellants can cause a decrease in the energy required of baking process. The process of manufacturing of bricks with HEP waste additive is first of its kind till date.

Numerical analysis of cook-off behavior of cluster tubular double-based propellant

To study the thermal security of solid rocket motors filled with cluster tubular double-based propellants, a 3-D transient heat transfer and cook-off response model was established. This was based on the global reaction model of double-based propellants, which follows the first-order Arrhenius law. Under the conditions that the fast cook-off ambient temperature is 600 ~ 1000 K and the slow cook-off heating rate is 1.8 ~ 5.4 K/h, the cook-off response characteristics of the tubular charge are numerically predicted. The results show that, in the case of fast cook-off, propellant begins thermal decomposition reaction at 420 K. The ignition position is close to the end faces on both sides of the propellant. The radial cross-sectional area of the ignition increases as the environment temperature increasing, but the ignition position does not change. In the case of slow cook-off, the incoming heat and release heat from the propellant decomposition reaction (start at 360 K) to heighten the temperature of the propellant. After reaching the ignition temperature, the thermal decomposition reaction accelerates, and the ignition occurs. Ignition areas are symmetrically distributed at both ends, and the ignition area moves from the inside to the outside as the heating rate increases.

Kinetics of Thermal Decomposition of Solid Propellant Based on Aluminum and Ammonium Perchlorate

Kinetic regularities of the mass loss and heat and-gas release were studied in the thermal decomposition of a solid propellant composed of aluminum, ammonium perchlorate, and a polymer binder. It was shown that, under heating from 40 to 340°C under permanent vacuum conditions, propellant samples decompose without ignition, with the limiting mass loss in the decomposition being 48%. When experiments were performed in air, the propellant formulation decomposes with sharp ignition, with the inflammation temperature (270–287°C) and amount of volatiles released by this instant of time (10–16 wt %) dependent on the heating rate. The kinetic regularities of the mass loss in the decomposition of a solid propellant were described in terms of the polychromatic kinetics model that assumes that the reaction system has ensembles of particles differing in reactivity. The distribution functions of the mass fractions of the propellant by activation energies of decomposition were calculated. The heat release kinetics in the decomposition of a propellant formulation in the temperature range 153–270°C in a closed evacuated system is described by a sum of equations for two parallel reactions: 1st-order reaction with a heat effect Q1 = 200 ± 5 kJ kg–1 and 1st-order autocatalysis with heat effect Q2 = 1900 ± 50 kJ kg–1. The rate constants and the activation parameters of the process were determined.

Simplified numerical simulation model for hydroxyl ammonium nitrate-based monopropellant rocket engines

A simplified model is proposed to simulate the working process of hydroxyl ammonium nitrate-based monopropellant rocket engines. The porous medium model and volume-of-fluid model are used to solve for the internal flow field of a monopropellant engine containing a catalyst bed to emphasize the establishment of a propellant decomposition model. The decomposition process is assumed to be separable into mass transfer and quick energy release processes. The mass transfer process is described by a two-stage decomposition model that combines catalytic and thermal decompositions according to temperature. This paper explains how to implement the two-stage decomposition model by using a titration experiment and thermal decomposition data. A detailed example is provided involving the calculation of the steady-state flow field of a 150-N monopropellant rocket engine in FLUENT. The results obtained using only the catalytic decomposition model and the two-stage decomposition model were compared with those of hot-fire tests, and show that the two-stage decomposition model is accurate. The combustion chamber pressure obtained from two- and three-dimensional simulations for the flow field of the engine agreed with the results of hot-fire tests. The calculated external wall temperature of the lower catalyst bed was slightly higher than the measured temperature, whereas the external wall temperature of the upper catalyst bed was close to the measured values.

Catalytic activity of nano-sized CuO on AP-CMDB propellant

ABSTRACTIn this work, nano-sized CuO prepared by mechanical grinding method was applied to the AP-CMDB propellant. The catalytic activity of nano-sized CuO on AP-CMDB propellant was investigated by thermogravimetric analysis/differential scanning calorimetric techniques. The combustion rates at atmospheric pressure of AP-CMDB propellant modified by nano-sized CuO were measured by strand burner method. The experimental results show enhancements on the thermal decomposition and combustion of AP-CMDB propellant in the presence of nano-sized CuO. Compared with blank propellant, the thermal decomposition temperature of AP-CMDB propellant shifts downward. Simultaneously, the combustion rate of AP-CMDB propellant at atmospheric pressure increases by about 22.2%. Encouragingly, the catalytic activity of nano-sized CuO on AP-CMDB propellant is superior to that of the bulk CuO, which leads to a potential application of nano-sized CuO in the AP-CMDB propellant.

Experimental investigation on combustion behaviors and reaction mechanisms for 5-aminotetrazole solid propellant with nanosized metal oxide additives under elevated pressure conditions

5-AT/Sr(NO3)2 based composite propellants have been applied in fire extinguishing fields as novel power source for several years due to its high thermal stability and large gas production, but the disadvantage of poor combustion stability still indeed to improve. In this study, the influential mechanism of two common burning modifier, nanosized Copper oxide (nano-CuO) and nanosized Zinc oxide (nano-ZnO), on the thermal behavior and combustion characteristics under high pressure of 5-AT based composite propellant was deeply investigated. Simultaneous thermogravimetric-differential thermal analysis (TG-DTA) have been used to identify the changes in the thermal and kinetic behavior of the catalyzed composite propellant. Thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG-FTIR) analysis and pyrolysis-gas chromatography with mass spectrometry (Py-GC/MS) analysis were employed to characterize the composition of evolved gas in propellant decomposition process. Combined with results of the combustion characteristics measurement conducted on a strand burner (1–5 MPa), different kinds of influential mechanisms of these two catalysts on decomposition process and combustion process under elevated pressure conditions were proposed based on presumed physical combustion model. Outcomes of this study will contribute to the design of 5-aminotetrazole solid propellant with a superior combustion property under high pressure, and promote its application into fire-fighting area.

Thermal stability evaluation of multiple tubes of fireworks by calorimetry approaches

Fireworks are constructed of powder and other materials that can readily release light and heat by oxidation reaction. Pyrotechnic compositions are highly susceptible and readily result in explosive decomposition. Fireworks have led to numerous accidents during their manufacture, storage, and display. Water as an impurity affects the decomposition properties of fireworks, and consequently influences their emission safety. This research focused on the thermal stability of multiple tubes of propellant, effect pieces, and propellant mixed with water using differential scanning calorimetry (DSC) and thermokinetic analysis. The thermokinetic method was employed to determine the apparent activation energy and predict the long-term stability of dry and humid propellants. According to the predicted results, the decomposition of dry and humid propellants was severely limited after 30 days at an isothermal condition of 80 °C. However, the DSC tests indicated that water could substantially influence the heat release, emission ability, and sensitivity of the propellant. The exothermic peak for the humid propellant was ca. 275 °C, which was lower than dry propellant of 318 °C. The water visibly diminished the heat emitted from and peak intensity of the propellant. Insufficient energy supply might result in lower emission height, and lower exothermic onset temperatures in wetted propellant could lead to faulty ignition times. Therefore, contact with water (that could lead to water infiltration) should be avoided to increase the probability of successful launching and ignition.