Propellant Applications Research Articles

Numerical Modeling and Experimental Investigation of Spray Combustion Process in Regenerative Liquid Propellant Mortar

AbstractRegenerative liquid propellant guns (RLPGs) have been studied for many years. However, the presence of large pressure oscillations is observed in almost each RLPG firing. In order to push forward the liquid propellant application in guns, a low pressure firing system called regenerative liquid propellant mortar (RLPM) is developed. The multiphase multidimensional fluid‐dynamics model is presented to research the interior ballistic properties of RLPM. A high‐speed liquid sheet spray model is presented for the annular jet in RLPM based on the linear stability analysis and surface wave breakup theory. In addition to the jet atomization, the droplets secondary breakup is considered. The experiments on a 60 mm RLPM test fixture are carried out, and the results indicate that the liquid propellant combustion oscillations are effectively suppressed. The spray and combustion processes have been simulated for the 60 mm RLPM which are in agreement with the experimental data well. Numerical results indicate an important benefit for the RLPM that the muzzle velocity is improved by increasing the charge quantity while the maximum chamber pressure remains unchanged.

Nitrostarch as a promising insensitive energetic biopolymer: Synthesis, characterization, and thermal decomposition kinetics

Natural polysaccharides have been outlined as one of the natural sources with more potential to obtain bio-energetic polymers through the chemical modification of their structure. In this work, nitrostarch, as an energetic nitrogen-rich polysaccharide, was successfully synthesized through the chemical modification of native potato starch . The synthesized energetic polymer and its precursor were extensively characterized using various analytical techniques and the obtained results confirm the functionalization process of the starch. In addition, its physicochemical features, molecular structure, morphology, and thermal behavior were determined using an electronic densimeter, elemental analysis, FTIR, SEM, TGA, and DSC . The sensitivity characteristics, the heat of combustion, and the heat of formation of the synthesized nitrostarch have been determined and its energetic performances were predicted using the EXPLO5 V6.04 software. Experimental results highlight promising features of the nitrostarch such as nitrogen content of 13 %, a density of 1.7365 g/cm 3 , and a detonation velocity of 7892 m/s in comparison to those of conventional nitrocellulose . In addition, the thermal decomposition kinetics of the nitrostarch have been deeply investigated as well using isoconversional kinetics analysis, and its Arrhenius parameters were derived for the first time. Finally, the obtained results demonstrated that this newly produced nitrogen-rich energetic material exhibits interesting energetic performance, which may further promote its application in explosives and high-performance propellants. In addition, this study will help to restore the forgotten interest concerning the employment of nitrostarch as a high-energy bio-polymer and to complete knowledge gaps and future trends for the industrial applications of this compound. • Nitrostarch was successfully prepared from native potato starch. • The properties of nitrostarch were compared to those of cellulose nitrate. • The synthesized nitrostarch revealed high nitrogen content, increased densities, good thermal stability, and outstanding insensitivity characteristics. • The thermal decomposition kinetics of nitrostarch has been deeply investigated and reported for the first time in the literature. • The calculated detonation parameters highlighted the interesting energetic performances of nitrostarch.

3D Electron-Rich ZIF-67 Coordination Compounds Based on 2-Methylimidazole: Synthesis, Characterization and Effect on Thermal Decomposition of RDX, HMX, CL-20, DAP-4 and AP

ZIF-67 is a three-dimensional zeolite imidazole ester framework material with a porous rhombic dodecahedral structure, a large specific surface area and excellent thermal stability. In this paper, the catalytic effect of ZIF-67 on five kinds of energetic materials, including RDX, HMX, CL-20, AP and the new heat-resistant energetic compound DAP-4, was investigated. It was found that when the mass fraction of ZIF-67 was 2%, it showed excellent performance in catalyzing the said compounds. Specifically, ZIF-67 reduced the thermal decomposition peak temperatures of RDX, HMX, CL-20 and DAP-4 by 22.3 °C, 18.8 °C, 4.7 °C and 10.5 °C, respectively. In addition, ZIF-67 lowered the low-temperature and high-temperature thermal decomposition peak temperatures of AP by 27.1 °C and 82.3 °C, respectively. Excitingly, after the addition of ZIF-67, the thermal decomposition temperature of the new heat-resistant high explosive DAP-4 declined by approximately 10.5 °C. In addition, the kinetic parameters of the RDX+ZIF-67, HMX+ZIF-67, CL-20+ZIF-67 and DAP-4+ZIF-67 compounds were analyzed. After the addition of the ZIF-67 catalyst, the activation energy of the four energetic materials decreased, especially HMX+ZIF-67, whose activation energy was approximately 190 kJ·mol-1 lower than that reported previously for HMX. Finally, the catalytic mechanism of ZIF-67 was summarized. ZIF-67 is a potential lead-free, green, insensitive and universal EMOFs-based energetic burning rate catalyst with a bright prospect for application in solid propellants in the future.

Fabrication of alginate-based microspheres with cellular structure for tuning ammonium dinitramide performance

Recently, an emerging category green of energetic material ammonium dinitramide (ADN) has exhibited promising application in propellants due to its outstanding merits in energy release and environmental friendliness. It can be considered to substitute traditional oxidizer of ammonium perchlorate (AP) in military systems and aerospace. In this paper, a novel spherical energetic composite ADN/copper alginate (CA) with a microporous structure was designed and prepared by the W/O gel emulsion method, and a desirable porous microsphere structure was obtained. Multiple characterization techniques were used to investigate the structure and properties of ADN/CA composites. The results showed that ADN crystals were homogeneously encapsulated in an alginate-gel matrix. Thermal decomposition temperature was reduced to 151.7 °C compared to ADN, while the activation energy of them was reduced from 129.73 kJ/mol (ADN) to 107.50 kJ/mol (ADN/CA-4). In addition, as-prepared samples had lower impact and frictional sensitivity than ADN. The mechanism of sensitivity reduction and decomposition are also discussed. Constant-volume combustion tests show that peak pressure of the ADN/CA-4 achieves 253.4 kPa and pressurization rate of 2750.4 kPa/s. Hence, this has a promising application in improving the combustion performance and safety performance of solid propellants.

Acid-base synthesis of aluminum iodate hexahydrate powder as a promising propellant oxidizer

An acid-base precipitation reaction is detailed to synthesize pure crystals of the oxidizer rich compound [Al(H2O)6](IO3)3(HIO3)2 and described here for the first time. The molecule is called aluminum iodate hexahydrate (AIH) and characterized for its energetic potential as an oxidizer in propellant applications. The synthesis method produced bipyramidal hexagonal crystals that are characterized physically and chemically by microscopy, pycnometry, and X-ray crystallography. Further energetic characterization is performed by bomb calorimetry, and impact, friction, and electrostatic discharge ignition sensitivity. This study introduces the potential of AIH as an alternative solid propellant by comparison to the properties of ammonium perchlorate (AP) and ammonium nitrate (AN).

Elaboration, Characterization and Thermal Decomposition Kinetics of New Nanoenergetic Composite Based on Hydrazine 3-Nitro-1,2,4-triazol-5-one and Nanostructured Cellulose Nitrate.

This research aims to develop new high-energy dense ordinary- and nano-energetic composites based on hydrazine 3-nitro-1,2,4-triazol-5-one (HNTO) and nitrated cellulose and nanostructured nitrocellulose (NC and NMCC). The elaborated energetic formulations (HNTO/NC and HNTO/NMCC) were fully characterized in terms of their chemical compatibility, morphology, thermal stability, and energetic performance. The experimental findings implied that the designed HNTO/NC and HNTO/NMCC formulations have good compatibilities with attractive characteristics such as density greater than 1.780 g/cm3 and impact sensitivity around 6 J. Furthermore, theoretical performance calculations (EXPLO5 V6.04) displayed that the optimal composition of the as-prepared energetic composites yielded excellent specific impulses and detonation velocities, which increased from 205.7 s and 7908 m/s for HNTO/NC to 209.6 s and 8064 m/s for HNTO/NMCC. Moreover, deep insight on the multi-step kinetic behaviors of the as-prepared formulations was provided based on the measured DSC data combined with isoconversional kinetic methods. It is revealed that both energetic composites undergo three consecutive exothermic events with satisfactory activation energies in the range of 139–166 kJ/mol for HNTO/NC and 119–134 kJ/mol for HNTO/NMCC. Overall, this research displayed that the new developed nanoenergetic composite based on nitrated cellulose nanostructure could serve as a promising candidate for practical applications in solid rocket propellants and composite explosives.

Rotating Detonation Combustion for Advanced Liquid Propellant Space Engines

Rotating (also termed continuous spin) detonation technology is gaining interest in the global research and development community due to the potential for increased performance. Potential performance benefits, thrust chamber design, and thrust chamber cooling loads are analyzed for propellant applications using liquid oxygen or high-concentration hydrogen peroxide oxidizers with kerosene, hydrogen, and methane fuels. Performance results based on a lumped parameter treatment show that theoretical specific impulse gains of 3–14% are achievable with the highest benefit coming from hydrogen-fueled systems. Assessment of thrust chamber designs for notional space missions shows that both thrust chamber length and diameter benefits are achievable given the tiny annular chamber volume associated with the rotating detonation combustion. While the passing detonation front drastically increases local heat fluxes, global energy balances can be achieved if operating pressures are limited to be comparable to existing or prior space engines.

Ultra-stretchable and ultra-low temperature self-healing polyurethane enabled by dual dynamic bonds strategy

The successful development of polyurethane with excellent low-temperature self-healing capability will facilitate it to find wider applications in composite solid propellants and other fields. Here, we report a design strategy that both quadruple hydrogen bonds and aliphatic disulfide bonds are introduced into polyurethane networks to achieve an ultra-stretchable and ultra-low temperature self-healing polyurethane. The polyurethane has excellent mechanical properties, including high tensile strength and elongation at breaks of 1303.56%, 1503.42%, 2381.88%, and 1814.07% at −40 °C, −20 °C, 25 °C, and 60 °C, respectively. Furthermore, after self-repair at −20 °C, the elongation at break of the cut polyurethane can reach 1120.14%, and the repair efficiency is 74.5%, whereas at −40 °C, the elongation at break and repair efficiency are 811.75% and 62.2%, respectively, which are rarely seen in the literature. In addition, the glass transition temperature of the polyurethane is extremely low (−78.34 °C), which facilitates their low-temperature application. The excellent properties of the prepared polyurethane will allow the preparation of composite solid propellants for use in a wider temperature range. More importantly, the proposed material is expected to have broader application prospects such as in cold-proof coatings, electronic devices, and so on.

Silicon alloying enhances fast heating rate combustion of aluminum particles

Alloys and composites of aluminum (Al) have shown promise in regulating and enhancing particle combustion for energy generation applications. Recent work on aluminum-silicon (Al-Si) spherical alloy particles has shown improved combustion at low heating rates through enhanced diffusion accompanying a lower melting temperature. This study extends reactivity analysis to higher heating rates, comparing oxidation of Al-Si with Al. Flame speeds of Al-Si powder mixed with molybdenum trioxide (MoO3) powder (Al-Si+MoO3) exhibited a faster transition to steady propagation relative to Al+MoO3. Bomb calorimetry experiments revealed up to 5.8% greater early temperature rise for Al-Si powder. Rapid steady propagation for Al-Si mixture and faster temperature rise for Al-Si particles were attributed to accelerated kinetics evidenced in thermal equilibrium analysis of the mixtures using a differential scanning calorimeter (DSC). Larger DSC exotherms in the early stages of oxidation (i.e., 480–720 °C) correlated with early heat release and promoted steady flame propagation for Al-Si+MoO3 compared with Al+MoO3. Furthermore, in multiple heating rate DSC studies, Al-Si+MoO3 ignited at a lower heating rate (i.e., 15 ⁰C/min) than Al+MoO3 (i.e., 20 ⁰C/min). Both mixtures ignited at temperatures less than 625 °C which is above the melting temperature of Al-Si (574 °C) and below Al (659 °C). Thus, alloy particle fuels with enhanced diffusion-controlled kinetics promote steady flame propagation and show promise for energy generation applications. This is especially promising for technologies driven by enhanced condensed phase combustion such as some propellant additives or applications dependent on reliable burn rates such as pyrotechnic time delay formulations and primers.

Investigation of the Gum Stock Behavior of Polyurethane Crosslinking Matrix by Adding Triol Diol Mixtures for the Application of Composite Solid Rocket Propellants

The addition of some advanced additives to improve the mechanical properties of polyurethane (PU) polymeric matrix, which acts as a binder system in composite solid rocket propellants (CSRPs), is a target for the energetic materials researchers. In this investigation, 45 compositions of different crosslinked PU matrices were produced to demonstrate the effect of adding crosslinking mixture (CM) on the mechanical capabilities of polyurethane gum stock. The crosslinking mixture (CM) is composed of a triol crosslinker, trimethylolpropane (TMP), and a chain extender, 1,4-butanediol
 (BD). For comparison, traditional PU samples without crosslinking additives were formulated. As a prepolymer, HTPB was used with a curing agent (HMDI). The research was carried out with different ratios of TMP to BD, different curing ratios (NCO/OH=0.7, 0.9, and 1.1), and crosslinking mixture contents in the range of 0-5 wt.%. The mechanical characteristics of all the cured formulations were measured. It was demonstrated that changing the ratio of TMP to BD has a significant impact on the mechanical performance causing a wide range of elongation and strength qualities. Increasing the wt.% of triol crosslinker in the sample enhanced the tensile strength, whereas the strain has been decreased. The addition of diol chain extender increased the strain rate of the samples. The mechanical parameters were adjusted simply by employing the crosslinking ingredients to get exceptional mechanical characteristics at each NCO/OH curing ratios. Also it was concluded that PU samples of curing ratio (NCO/OH= 0.7-0.9) with TMP:BD (1:1) showed a promising results and could be used according to the requirements of the rocket system designers.

Anti-sintering behavior and combustion process of aluminum nano particles coated with PTFE: A molecular dynamics study

The characteristic of easy sintering of aluminum nanoparticle (ANP) limits its application in solid propellants. Coating ANP with fluoropolymer could effectively improve its combustion performance. To find out how the coating layer inhibits sintering and promotes complete combustion of particles from an atomic view, a comparative study has been done for bare ANP and PTFE coated ANP by using reactive molecular dynamics simulations. The sintering process is quantified by shrinkage ratio and gyration radius. Our results show that, at the same heating rate and combustion temperatures, bare ANPs are sintered together after the temperature exceeds the melting point of aluminum but the decomposition of PTFE coating layer pushes particles away and increases reaction surface area by producing small Al–F clusters. The sintering of ANPs which are heated in PTFE is alleviated compared with particles heated in oxygen, but particles still sinter together due to the lack of intimate contact between PTFE and alumina surface. The effect of temperature on the combustion of PTFE coated ANPs is also studied from 1000 to 3500 K. The number density analysis shows the particles will not be sintered at any temperature. Aluminum fluoride prefers diffusing to the external space and the remained particles are mainly composed of Al, C and O. Fast ignition simulations are performed by adopting micro canonical ensemble. With the expansion of aluminum core and the melting of alumina shell, bare ANPs are sintered into a liquid particle directly. For PTFE coated ANPs, the volatilization of gaseous aluminum fluoride products continually endows particles opposite momentum.

Electrostatic spraying synthesis of energetic RDX@NGEC nanocomposites

It displays a favorable spherical morphology of the energetic RDX@NGEC nanocomposites and the 3D distribution of Raman mapping images, as well as the gas products detected by IR, and the mechanism of the desensitization. • Electrospray technology is utilized to assemble a novel energetic RDX@NGEC nanocomposites successfully. • The obtained RDX@NGEC composites exhibit favorable thermal decomposition and significant reduced sensitivity. • The mechanism of coating process, thermal decomposition and desensitization was proposed and discussed. • This construction strategy of novel energetic binder NGEC-based composites provides an application potential in propellants. Recently, an emerging category of thermal plastic energetic binder: nitrate glycerol ether cellulose (NGEC) exhibits promising application in propellants with extraordinary mechanical performance, and can be considered for using in military system instead (or partial) of traditional nitrocellulose (NC). In this paper, the electrostatic spraying technology is performed to synthesis a novel kind of nanocomposites energetic materials (nEMs) (hexahydro-1,3,5-trinitro-1,3,5-triazine) RDX@NGEC by adjusting the mass ratio of NGEC:RDX (0:5 ∼ 2.5:2.5). The results demonstrate that the NGEC patches with content of 30% were coated relatively uniformly on the surface of RDX crystal, and an ideal spherical structure, with dramatically reduced particle size (100 ∼ 800 nm) was obtained. Most importantly, the thermal decomposition properties are investigated systematically by traditional DSC (differential scanning calorimeter) analysis, DSC-TG-IR (DSC-thermogravimetric analysis-fourier-transform infrared spectroscopy) combining technology, where the kinetic parameters of thermal decomposition reaction are also calculated by two traditional methods: the Kissinger and Ozawa methods. It reveals that the process of the decomposition is mainly controlled by RDX when content of NGEC is low (10%∼20%), and the decomposition peak of NGEC is gradually appearing with the increasing content of NGEC (30%∼50%). Furthermore, the impact and friction sensitivities are tested and have been reduced about 1 ∼ 3 times. The mechanism of the sensitivity reduction, coating process and decomposition are also discussed detailly. Hence, this preparation and properties strategy of novel energetic RDX@NGEC nanocomposites may provide foundational theory research and exhibits application potential in propellants and explosives.

Hydrogen peroxide – A promising oxidizer for rocket propulsion and its application in solid rocket propellants

This paper discusses the potential use of hydrogen peroxide as oxidizer for solid rocket propulsion. While hydrogen peroxide is a liquid in normal conditions, it may be used in solid rocket motor grains. Use of hydrogen peroxide of HTP class (High Test Peroxide) is proposed. It has been known for many decades but its utilization has been historically limited to liquid propellants. Until recently is application even in liquid state in rocket propulsion for space and defence has been limited due to storability and safety issues. With the availability of new grades of HTP with higher purity and concentrations, enhanced performance, safety and storability are possible. This results in HTP being considered for a wide range of rocket propulsion systems: as oxidizer in bipropellant and hybrid propulsion systems, as well a monopropellant. To ensure proper analysis of the potential of using HTP in next-generation solid rocket propellants, this paper reviews existing rocket propulsion applications of HTP. Modern use requires high performance and common current composite propellant compositions utilize ammonium perchlorate (AP) as oxidizer, what has several disadvantages, which are discussed. Alternative oxidizing compounds include ammonium dinitiramide (ADN), ammonium nitrate (AN), hydrazinium nitroformate (HNF), hexanitrohexaazaisowurtzitane (HNIW) and several other secondary explosives. Key properties of solid propellant oxidizers are listed and discussed. The need for further alternatives, despite numerous recent advances in solid rocket oxidizer technology is justified. The global push forward high performance green propulsion is one of the main motivations behind considering HTP for solid rocket propulsion. Theoretical performance of solid rocket motors using solid grains containing a high mass fraction of HTP is presented. This includes performance considering several fuels and additives and different oxidizer loadings. Up to date concepts of using hydrogen peroxide in solid propellants are reviewed. Solid cryogenic propellants using hydrogen peroxide are mentioned, but focus is given to solid propellants which could ensure flexible operations, thus use in state-of-the-art solid rocket motors. Challenges of HTP application as an oxidizer for solid propulsion are listed. This includes a discussion concerning its reactivity, thus limited compatibility with organic materials. Recommendations for further experimental work are proposed. Potential technology applications are listed with explanations why these particular niches may benefit from utilization of the new solid propellant technology.

Comprehensive Performance Evaluation of Densified Liquid Hydrogen/Liquid Oxygen as Propulsion Fuel

Densified liquid hydrogen/liquid oxygen is a promising propulsion fuel in the future. In order to systematically demonstrate the benefits and challenges of densified liquid hydrogen/liquid oxygen, a transient thermodynamical model considering the heat leakage, temperature rise, engine thrust, pressurization pressure of the tank, and wall thickness of tank is developed in the present paper, and the performance of densified liquid hydrogen/liquid oxygen as propulsion fuel is further evaluated in actual application. For liquid hydrogen/liquid oxygen tanks at different structural dimensions, the effects of many factors such as temperature rise during propellant ground parking, lift of engine thrust, mass reduction of the tank structure, and extension of spacecraft in-orbit time are analyzed to demonstrate the comprehensive performance of liquid hydrogen/liquid oxygen after densification. Meanwhile, the problem of subcooling combination matching of liquid hydrogen/liquid oxygen is proposed for the first time. Combining the fuel consumption and engine thrust lifting, the subcooling combination matching of liquid hydrogen/liquid oxygen at different mixing ratios and constant mixing ratios are discussed, respectively. The results show that the relative engine thrust enhances by 6.96% compared with the normal boiling point state in the condition of slush hydrogen with 50% solid content and enough liquid oxygen. The in-orbit time of spacecraft can extend about 2–6.5 days and 24–95 days for slush hydrogen with 50% solid content and liquid oxygen in the triple point state in different cryogenic tanks, respectively. Due to temperature rise during parking, the existing adiabatic storage scheme and filling scheme for densification LH2 need to be redesigned, and for densification LO2 are suitable. It is found that there is an optimal subcooling matching relation after densification of liquid hydrogen/liquid oxygen as propulsion fuel. In other words, the subcooling temperature of liquid hydrogen/liquid oxygen is not the lower the better, but the matching relationship between LH2 subcooling degree and LO2 subcooling degree needs to be considered at the same time. It is necessary that the LO2 was cooled to 69.2 K and 54.5 K, when the LH2 of 13.9 K and SH2 with 45% was adopted, respectively. This research provides theoretical support for the promotion and application of densification cryogenic propellants.

Thermal decomposition and combustion behavior of solid propellant containing Si-based composites

In this work, Si@NC/AP and Si@PVDF/CL-20 composites with different Si contents have been fabricated by spray-drying technique. The flame structure, ignition delay time and combustion process have been investigated. It has been shown that the ignition delay of Si-based fuel with 40 wt% of Si is the shortest. This means that oxygen balance and the catalytic effect of Si on the energetic composites are playing a dominant role during the combustion processes of these composites. The solid composite propellants (SCP, named as SCP-1 and SCP-2) contains two typical Si-based composites Si-80@NC/AP and Si-80@PVDF/CL-20 have been prepared for propellant applications. Their propellants containing the corresponding mechanical mixtures (named as SCP-3 and SCP-4) have been fabricated as a comparison. It has been observed that the cross sections of propellants containing Si-based composites are denser than that of the reference propellants. The burn rate of SCP-1 (with Si-80@NC/AP) and SCP-2 (with Si-80@PVDF/CL-20) are 5.74 and 5.10 mm s−1 at 2.0 MPa, respectively, which are lower than those of the reference samples SCP-3 (6.51 mm s−1) and SCP-4 (5.70 mm s−1). However, the pressure exponent of former is slightly lower than that of the latter. Moreover, the combustion products (CCPs) of SCP-1 and SCP-3 are more fluffy and smaller in particles size than those of SCP-2 and SCP-4. This indicates that the core-shell structured composites have much better combustion performances due to better heat and mass transfer between the oxidizers and Si as fuel.

Study on catalytic activity and mechanism of tetrazole-based energetic metal-organic frameworks for thermal decomposition of ammonium perchlorate

ABSTRACT In order to comprehensively improve the energy performance and combustion properties of the propellants, four energetic metal–organic frameworks (EMOFs) constructed from transition-metal ions (Ag+, Cd2+, Pb2+) and tetrazole-based energetic ligands (5-methyl tetrazole (HMtta), N,N-bis(1H-tetrazole-5-yl)-amine (H2bta), 3-(1H-tetrazol-5-yl)-1H-triazole (H2tztr)) were prepared by hydrothermal synthesis. The crystal phase and structure of the as-prepared samples were analyzed by XRD and IR characterization. Their catalytic activity on thermal decomposition of ammonium perchlorate (AP) was evaluated by DSC. The results show that as-prepared EMOFs can significantly reduce the thermal decomposition temperature of AP and increase its heat release. Under the optimal condition that the addition amount is 10 wt%, the high-temperature decomposition peak temperatures of [AgMtta]n/AP, [Cd5(Mtta)9]n/AP, [Pb3(bta)2(O)2(H2O)]n/AP, and [Pb(Htztr)2(H2O)]n/AP are decreased by 107.2°C, 94.2°C, 54.6°C, and 91.1°C compared to the case of pure AP, while the heat releases of them are increased by 1243.9 J∙g−1, 1226.2 J∙g−1, 1332.2 J∙g−1, 1444.4 J∙g−1, respectively. In addition, compared with the reported catalysts such as [Pb(BTF)(H2O)2]n, CuFe2O4, [Cu2(en)2(HBTI)2]2, and [Cu2(en)(HBTI)2]2en, the EMOFs prepared in this study show equal or even higher catalytic activity and heat release. Moreover, the catalytic mechanism of EMOFs on thermal decomposition of AP is also analyzed based on the electron transfer theory. With the excellent energy properties and catalytic performances, the prepared EMOFs may become promising energetic additives for composite solid propellant applications.

Synthesis of two novel neutral polymeric bonding agents to enhance the mechanical properties of composite solid propellants.

Currently, only a few bonding agents can be utilized efficiently in nitramine filler material-based solid rocket energetic binder systems. Herein, we demonstrate the synthesis and specific characterization of two kinds of neutral polymeric bonding agents (NPBA-1 and NPBA-2) and their application in composite propellants consisting of the nitramine octogen (HMX) and glycidyl azide polymer (GAP). The as-obtained NPBAs were well-coated on the surface of HMX and RDX due to their functionalized groups, and they significantly affected the viscosity of the uncured propellant mixtures and possessed obviously enhanced mechanical properties in the cured AP/HMX/GAP propellant mixtures, even at low concentrations (down to 0.001 wt% of the whole propellant). In addition, because of the existence of an epoxy group and no hydroxyl functionalities, NPBA-2 exhibited improved mechanical strength and glass transition temperature as compared to NPBA-1, which has plenty of reactive hydroxyl groups. The as-synthesized epoxy-modified NPBAs are essential for obtaining NEPE propellants with high bonding and mechanical properties.

Response Surface Methodology for Optimization of Nitrocellulose from Bacterial Cellulose Nata De Coco for Potential Propellant Application

Response Surface Methodology for Optimization of Nitrocellulose from Bacterial Cellulose Nata De Coco for Potential Propellant Application

Two novel heterobimetallic metal-organic frameworks for the enhanced catalytic thermolysis and laser ignition of CL-20

The study of multiple complex catalytic mechanisms is currently one of the great scientific issues for the application of high-energy solid propellants. Two novel heterobimetallic metal-organic frameworks (MOFs), Ba4Pb4(CH3CO2)8 [(CH6CO2)4Pb](CH3CO2)4 (PbBa-MOF) and Ba2Ni(CO2H)6(OH2)4 (NiBa-MOF), were prepared via the solvothermal method, and their structures and composition were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR) techniques and N2 adsorption/desorption experiment. The thermal decomposition characteristics of the two MOFs and their catalytic performances on the hexanitro hexaazaisowurtzitane (CL-20) thermolysis were also studied by differential scanning calorimetr (DSC) and thermogravimetric-fourier transform infrared spectroscopy-mass spectrum (TG-FTIR-MS) methods. The results showed that the NiBa-MOF presented a lower initial decomposition temperature than the PbBa-MOF, and the difference of the MOFs structures affected the starting point of thermal decomposition. Compared with the pure CL-20, the thermolysis peak temperature and apparent activation energy (Ea) of the CL-20/PbBa-MOF mixture were decreased by 2.2 °C and 23.76 kJ‧mol−1, respectively. The Ea of CL-20/NiBa-MOF mixture was lower and 42.01 kJ‧mol−1, indicating the better catalytic activity of NiBa-MOF. The thermolysis catalytic mechanisms were studied by analyzing the transformation of gas products during the pyrolysis of mixtures. The effect of these two MOFs on the CL-20 thermolysis is primarily owing to the strong attraction of metal cations to electronics, bimetallic synergistic catalysis, and the release of active free radicals. Furthermore, the laser ignition and flame propagation features showed that these two MOFs reduced the minimum ignition power density and ignition delay time of the CL-20, and the flame becomes brighter and more luminous. The influence of the two MOFs on the flame bright spot of CL-20 based mixtures was described.

Unique thermal and combustion behaviors of composite propellants containing a high-energy insensitive nitropyrimidine derivative

Owing to the novel insensitive high-energy-density material 2,4,6-triamino-5-nitropyrimidine-1,3-dioxide (ICM-102) has lower sensitivity and higher energy(see in Table S1, Supporting Information), it has great advantages in the application of low-vulnerability propellants. In this paper, the evaluation of ICM-102-containing composite propellants has been carried out, where the decomposition and combustion performances of these propellants have been comprehensively investigated. It has been shown that the main exothermic decomposition peak temperature can be increased from 235 ºC to 350 ºC, when 6 to 10 wt% of ICM-102 was used to replace RDX, but heat release rate was largely increased. Moreover, the burning rate of ICM-102 containing propellants at 3 MPa is in the range of 6.97–7.75 mm•s − 1, depending on its content. The pressure exponent (0.5–3 MPa) is between 0.34–0.44. Compared with the typical propellants with RDX, the burn rate and the flame temperature of ICM-102- containing propellants are higher. In addition, the particle size distributions of condensed combustion products of ICM-102 propellants are narrower and smaller than that of RDX-based one. It also shows that extra products such as aluminum carbide (Al20C) and aluminum oxide nitride (Al5O6N) were produced once ICM-102 was used.