Recent advances in new oxidizers for solid rocket propulsion

Synthesis, Characterization and Energetic Properties of Hydroxymethyl-Bishomocubanone Derivatives

The present work reports synthesis, characterization and theoretical insights on novel hydroxymethyl-bishomocubanone derivatives. Twelve new bishomocubanes (BHCs) were synthesized and fully characterized by various spectroscopic techniques and single crystal X-ray analysis. The densities of the title compounds were in the range of 1.30-1.59 g/cm3. Density-functional theory (DFT) based calculations at B3LYP/6-311++G(d,p) level of theory were performed on ten selected BHC based cage compounds. Propulsive and ballistic properties of newly synthesized hydroxymethyl-bishomocubanone derivatives in solid and liquid propulsion systems were calculated, and the results suggested that these compounds are superior to conventional fuel RP1 and binder HTPB. The detonation parameters revealed that these compounds are not explosive in nature and safe to use as solid propellants. Furthermore, kinetic and thermal stabilities of the title compounds were determined by HOMO-LUMO energy gap, ESP maps, impact sensitivity (h50) and bond dissociation energies (BDEs) followed by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Three compounds, a dinitroazide (Isp,vac=310.98 s), a dinitrate (Isp,vac=309.51 s), and a dinitronitrate (Isp,vac=309.20s) were found to be excellent candidates for volume limited applications.

Theoretical study of a series of 1,2-diazete based trinitromethyl derivatives as potential energetic compounds

CONTEXT

Explosive properties of novel potential high energy density materials of a series of 1,2-diazete-based molecules with trinitromethyl functional group were investigated computationally. All the sixty seven molecules were optimised to obtain their molecular geometries and electronic structures. Electrostatic potential analysis was also carried out in the determination of different parameters. The calculations indicate that the majority of the compounds have high positive heat of formations, high density and good detonation performance greater than that of traditional energetic materials like RDX and HMX. They are also having comparable values of impact sensitivity. These features promise their potential to be used as energetic materials for future applications. Most of the designed molecules are having high positive oxygen balance values so that the study of these molecules can also be extended as potential candidates for oxidisers in solid propellants.

METHODS

Optimisation and vibrational frequency analysis of the studied molecules were done with density functional theory using B3LYP/aug-cc-pVDZ as the basis set to zero imaginary frequencies using Gaussian 09. Electrostatic potential analysis were carried using the Multiwfn program.

Perchlorate-Free Energetic Oxidizers Enabled by Ionic Cocrystallization

The search for a suitable replacement for the ubiquitous oxidizer ammonium perchlorate (AP) is a top priority to enable more sustainable solid rocket motors. The oxidizing salts ammonium nitrate (AN) and ammonium dinitramide (ADN) are regarded as potential green replacements for AP, but suffer from a plethora of handling and processing issues including poor stability and a needle-like crystal morphology which inhibits dense packing; these prevent their widespread use. In the present work, ionic cocrystallization is leveraged to produce the first cocrystals of these oxidizing salts with an energetic coformer and the first such cocrystals to maintain a positive oxygen balance. The azole-based energetic molecule 5,5'-dinitro-2H,2H'-3,3″-bi-1,2,4-triazole (DNBT) is successfully cocrystallized with AN to yield the cocrystal 2AN:DNBT. Differential scanning calorimetry data confirms that AN, which in its pure form suffers from a problematic solid-state phase transition, is stabilized in the cocrystal. Application of this cocrystallization strategy to ADN produces 2ADN:DNBT, which has the highest oxygen balance of any organic cocrystal.

Electrochemical Synthesis of the Energetic Combustion Catalyst Co(BODN)·9H2O and Its Catalytic Effect on Ammonium Perchlorate Thermal Decomposition

Safe, efficient, and green synthetic energetic combustion catalysts are of great importance for the application of ammonium perchlorate (AP) in solid propellants. In this study, a novel, simple, efficient, and green electrochemical method for synthesizing energetic combustion catalysts was designed and implemented to successfully synthesize Co(BODN)·9H2O (BODN = [2,2'-bi{1,3,4-oxadiazole}]-5,5'-dinitramide), a novel energetic combustion catalyst. The target products were characterized via single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared spectroscopy, optical microscopy, scanning electron microscopy, differential scanning calorimetry, and thermogravimetric analysis. Results reveal that Co(BODN)·9H2O crystallizes in the triclinic P1̅ space group and has a density of 1.836 g cm-3. The size of the Co(BODN)·9H2O crystal increases gradually with the increase in the reaction current and the prolongation of the reaction time, respectively. However, the change in reaction current and time does not affect the crystal form. In addition, with the increase in Co(BODN)·9H2O content, the peak temperature of high-temperature decomposition (HTD) and apparent activation energy of AP/Co(BODN)·9H2O gradually decrease, and the heat release during thermal decomposition gradually increases. The HTD peak temperature and apparent activation energy of AP/Co(BODN) 9H2O (10%) decrease by 97.9 °C and 94.2 kJ·mol-1, respectively, compared with those of pure AP, and the heat release during thermal decomposition increases by 1613 J·g-1. Furthermore, compared with those of the propellant containing pure AP, the burning rate and flame temperature of the propellant containing AP/Co(BODN)·9H2O (10%) increase by 8.15 mm s-1 and 458.44 °C, respectively. Real-time Fourier transform infrared spectroscopy reveals that CoO catalyzes the thermal decomposition of AP mainly by promoting electron transfer to accelerate the oxidation of NH3 and the conversion of N2O to NO. In brief, this work provides new insights into synthesizing energetic combustion catalysts. Moreover, Co(BODN)·9H2O synthesized through the electrochemical method exhibits considerable application prospects for improving the thermal and energy performance of AP and the combustion performance of propellants.

Backbone Isomerization to Enhance Thermal Stability and Decrease Mechanical Sensitivities of 10 Nitro-Substituted Bipyrazoles

The development of novel, environmentally friendly, and high-energy oxidizers remains interesting and challenging for replacing halogen-containing ammonium perchloride (AP). The trinitromethyl moiety is one of the most promising substituents for designing high-energy density oxidizers. In this study, a backbone isomerization strategy was utilized to manipulate the properties of 10 nitro group-substituted bipyrazoles containing the largest number of nitro groups among the bis-azole backbones so far. Another advanced high-energy density oxidizer, 3,3',5,5'-tetranitro-1,1'-bis(trinitromethyl)-1H,1'H-4,4'-bipyrazole (3), was designed and synthesized. Compared to the isomer 4,4',5,5'-tetranitro-2,2'-bis(trinitromethyl)-2H,2'H-3,3'-bipyrazole (4) (Td = 125 °C), 3 possesses better thermostability (Td = 156 °C), which is close to that of ammonium dinitramide (ADN) (Td = 159 °C), and it possesses better mechanical sensitivity (impact sensitivity (IS) = 13 J and friction sensitivity (FS) = 240 N) than that of 4 (IS = 9 J and FS = 215 N), thereby demonstrating a promising perspective for practical applications.

Tripodal Organic Cages with Unconventional CH···O Interactions for Perchlorate Remediation in Water

Perchlorate anions used in industry are harmful pollutants in groundwater. Therefore, selectively binding perchlorate provides solutions for environmental remediation. Here, we synthesized a series of tripodal organic cages with highly preorganized Csp3-H bonds that exhibit selectively binding to perchlorate in organic solvents and water. These cages demonstrated binding affinities to perchlorate of 105-106 M-1 at room temperature, along with high selectivity over competing anions, such as iodide and nitrate. Through single crystal structure analysis and density functional theory calculations, we identified unconventional Csp3-H···O interactions as the primary driving force for perchlorate binding. Additionally, we successfully incorporated this cage into a 3D-printable polymer network, showcasing its efficacy in removing perchlorate from water.

Design and synthesis of phenylene-bridged isoxazole and tetrazole-1-ol based energetic materials of low sensitivity

A variety of phenylene-bridged isoxazole and tetrazole-1-ol based green energetic materials was synthesized, for the first time, in good to excellent yields. The structures of the newly synthesized compounds were confirmed by spectroscopic techniques, elemental analysis, and single-crystal X-ray analysis. The value of the present work is that all newly synthesized compounds have good thermal stabilities ranging between 167-340 °C and acceptable densities between 1.51 g cm^-3 to 1.82 g cm^-3. Detailed computational insight into the energetic properties of the new compounds shows that they have good energetic properties (propulsive and ballistic) with excellent thermal and mechanical stabilities which makes them promising candidates for solid propulsion systems. Compounds 5, 12 and 14 are the superior candidates as melt-castable energetic materials.

Unraveling the Effect of MgAl/CuO Nanothermite on the Characteristics and Thermo-Catalytic Decomposition of Nanoenergetic Formulation Based on Nanostructured Nitrocellulose and Hydrazinium Nitro-Triazolone

The present study aims to develop new energetic composites containing nanostructured nitrocellulose (NNC) or nitrated cellulose (NC), hydrazinium nitro triazolone (HNTO), and MgAl-CuO nanothermite. The prepared energetic formulations (NC/HNTO/MgAl-CuO and NNC/HNTO/MgAl-CuO) were analyzed using various analytical techniques, such as Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), thermogravimetry (TGA), and differential scanning calorimetry (DSC). The outstanding catalytic impact of MgAl-CuO on the thermal behavior of the developed energetic composites was elucidated by kinetic modeling, applied to the DSC data using isoconversional kinetic methods, for which a considerable drop in the activation energy was acquired for the prepared formulations, highlighting the catalytic influence of the introduced MgAl-CuO nanothermite. Overall, the obtained findings demonstrated that the newly elaborated NC/HNTO/MgAl-CuO and NNC/HNTO/MgAl-CuO composites could serve as promising candidates for application in the next generation of composite explosives and high-performance propellants.

Towards Investigating the Effect of Ammonium Nitrate on the Characteristics and Thermal Decomposition Behavior of Energetic Double Base NC/DEGDN Composite

This research work aimed to elaborate on a new modified double-base propellant containing nitrocellulose (NC), ammonium nitrate (AN), and diethylene glycol dinitrate (DEGDN). The developed AN/NC-DEGDN formulation was successfully obtained through a casting process and fully characterized in terms of its chemical structure, morphological features, and thermal behavior. Beforehand, theoretical calculation by the CEA-NASA program was applied to select the optimal composition of the formulation. Experimental findings demonstrated the homogenous dispersion of AN oxidizer in the NC-DEGDN matrix without alteration of their molecular structures. The catalytic influence of AN on the thermal decomposition behavior of NC-DEGDN film was also elucidated by thermal analyses. When AN was incorporated into the formulation, the decomposition peak temperatures for the different decomposition processes were shifted toward lower temperatures, while the total enthalpy of decomposition increased by around 1272.24 J/g. In addition, the kinetics of the thermal decomposition of the developed modified double base propellant were investigated using DSC results coupled with model kinetic approaches. It was found that the addition of AN decreases the activation energy of nitrate esters from 134.5 kJ/mol to 118.84 kJ/mol, providing evidence for its excellent catalytic effect. Overall, this investigation could serve as a reference for developing future generation of modified double-base propellants.

Effect of rGO with BaCuO3 perovskite on the thermal decomposition of AP and NTO

In this study, the syntheses of a BaCuO₃ perovskite-structured oxide and rGO were conducted using a sol-gel method and ultrasonication process, respectively. Their physico-chemical characteristics were studied by powder X-ray diffraction (PXRD), Raman spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy analyses. The perovskite type particles were found to present as a cubic crystal system with a crystal size in the range of 10-60 nm. Their catalytic performance was investigated using differential thermal analysis (DTA) measurements at varying heating rates via the thermal decomposition of ammonium perchlorate (AP) and 3-nitro-1,2,4-triazol-5-one (NTO). The kinetics and thermodynamics parameters, such as the average activation energy, pre-exponential factor, entropy, and Gibbs free energy, were also investigated, which showed a decrease in the decomposition peak temperature of AP and NTO in the presence of the catalysts rGO, BaCuO₃, and rGO + BaCuO₃ compared to pure AP and NTO.

Energetic bimetallic complexes as catalysts affect the thermal decomposition of ammonium perchlorate

Two bimetallic complexes of 4-hydroxy-3,5-dinitropyrazole, [K₂Mn(DNPO)₂(H₂O)₄]_n·2H₂O (BMEP-1) and [K₂Zn(DNPO)₂(H₂O)₆]_n (BMEP-2), were synthesized and characterized by IR spectroscopy and elemental analysis. The crystal structures of BMEP-1 and BMEP-2 were determined by single-crystal X-ray diffraction. It is noteworthy that these complexes presented different metal-organic frameworks. The thermal behaviors of BMEP-1 and BMEP-2 were investigated by differential scanning calorimetry and thermogravimetric analysis measurements. These bimetallic complexes exhibited high thermal stability (348.0 °C and 331.0 °C) due to their large coordination bonds and three-dimensional interconnected structure. The catalytic performances of BMEP-1 and BMEP-2 on the thermal decomposition of ammonium perchlorate were investigated by TGA-DSC, TGA-FTIR, and non-isothermal kinetic analyses. The results showed that BMEP-1 and BMEP-2 exhibited excellent catalytic performance in the thermal decomposition of ammonium perchlorate. Notably, there was only a single exothermic peak at 302.6 °C and 318.6 °C, and the activation energy values of ammonium perchlorate decreased to 123.88 kJ mol^-1 and 128.43 kJ mol^-1, respectively. TGA-FTIR results showed that BMEP-1 and BMEP-2, as effective components of catalysis, will promote the production of H₂O, N₂O, NO₂, and HCl in advance, during the thermal decomposition of ammonium perchlorate. BMEP-1 and BMEP-2 are expected to be two candidate additives for the catalytic decomposition of ammonium perchlorate in composite solid propellants.

Experimental and simulation study on hydrogen-bond-induced crystallization of spherical ammonium dinitramide

The effects of hydrogen bonding between solvents (ethanol, ethanol–acetone and ethanol–ethyl acetate) and ammonium dinitramide (ADN) crystal faces on the morphology of ADN are studied experimentally and by molecular dynamics (MD) simulation. Scanning electron microscopy shows that ADN recrystallized from ethanol, ethanol–acetone and ethanol–ethyl acetate takes the form of a slice, a sheet aggregate and a sphere, respectively. The MD results show that the order of the standard deviation (E dev) of the hydrogen-bonding energy (E b) in the three solvent systems is as follows: ethanol > ethanol–acetone > ethanol–ethyl acetate. The larger the E dev, the larger the difference of each crystal plane size. The radial distribution function reveals that the carbonyl group of ethyl acetate promotes hydrogen-bond formation between O atoms in the nitro groups of ADN and H atoms in ethanol; meanwhile the O atom in the C—O bond of ethyl acetate forms a hydrogen bond with an H atom in ADN. Therefore, the E dev of each crystal face is further lowered, and finally a spherical ADN is obtained.

First-Principles Investigation of Graphene and Fe2O3 Catalytic Activity for Decomposition of Ammonium Perchlorate

The employment of catalysts is an effective way to improve ammonium perchlorate (AP) decomposition performance during the combustion of composite solid propellants. Understanding the micromechanism of catalysts at the atomic level, which is hard to be observed by experiments, can help attain more excellent decomposition properties of AP. In this study, first-principles simulations based on density functional theory were used to explore the effect of the graphene catalyst and iron oxide (Fe₂O₃) catalyst on AP decomposition. Considering the transfer of a H atom during AP decomposition, the most stable adsorption sites for aforementioned catalysts were found: the top of the C atom of the graphene surface with the adsorption energy of -0.378 eV and the top of the Fe atom of the Fe₂O₃ surface with the adsorption energy of -1.596 eV. On the basis of adsorption results, our transition state calculations indicate that, in comparison to control groups, graphene and Fe₂O₃ can reduce the activation energy barrier by ∼19 and ∼37%, respectively, to promote AP decomposition with a transfer process of a H atom on the catalyst surface. Our calculations provide a way for explaining the micromechanism of the catalytic activity of graphene and Fe₂O₃ nanocomposites in AP decomposition and guide experimental applications of graphene and Fe₂O₃ for catalytic reactions.

Construction of a physically cross-linked carrageenan/chitosan/calcium ion double-network hydrogel for 3-Nitro-1, 2, 4-triazole-5-one removal

3-Nitro-1, 2, 4-triazole-5-one (NTO) is an important insensitive explosive. The discharge of NTO wastewater not only pollutes the environment but also causes the economic loss of the valuable explosive. Currently, the NTO wastewater in industrial production is often treated with activated carbon adsorbents. There are no green, efficient and specific adsorption materials for the NTO treatment yet. In the present work, polymer materials suitable for NTO adsorption were screened by molecular dynamics simulation. With the optimized materials, a carrageenan/chitosan/calcium ion physically cross-linked double network hydrogel (KC/CTS/Ca²⁺ PCDNH) was successfully prepared by the semi-soluble-acidified sol-gel conversion method. The structure and NTO adsorption performance of the hydrogel were investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The NTO adsorption kinetics, isotherm, and thermodynamics were further studied to understand the adsorption behavior and mechanism. In addition, the adsorbed NTO was successfully released and recovered by soaking the hydrogel in NaOH solution. Our work has provided an environmentally friendly and targeted preparation method of NTO adsorbent materials for NTO wastewater treatment.

Synthesis of Diaminoacetic Acid Derivatives as a Promising Scaffold for the Synthesis of Polyheterocyclic Cage Compounds

Here, we explored in detail an acid-catalyzed condensation of glyoxylic acid or its ethyl ester with several carboxamides of different basicity, or with mesyl amide, to furnish diaminoacetic acid derivatives. The most suitable synthesis conditions and the reaction catalysts were identified. Properties such as structure and basicity of the starting amides were demonstrated to influence the condensation process. Elemental iodine was used for the first time herein as an acid catalyst for the condensation of glyoxylic acid or its ester, which gave access to diaminoacetic acid derivatives in higher yields in most cases, as opposed to p-toluenesulfonic acid (PTSA). An abnormally high activity of mesyl amide when condensed with ethyl glyoxylate was noticed, which may evidence a special impact of the sulfonyl moiety in the amide molecule on the condensation.

Design and Computational Insight on Two Novel CL-20 Analogues, BNMTNIW and BNIMTNIW: High Performance Energetic Materials

In this study, a theoretical Insight into two newly designed novel CL-20-based high performance energetic compounds, namely bis(nitromethyl)-tetranitrohexaaza-isowurtzitane (BNMTNIW) and bis(nitratomethyl)-tetranitrohexaaza-isowurtzitane BNIMTNIW), is reported. The title compounds are expected to...

Host–guest energetic materials: a promising strategy of incorporating small insensitive molecule into the lattice cavities of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane to enhance the safety on the premise of maintaining the excellent energy density

A novel HNIW-MA host–guest explosive was constructed by embedding the mall molecules into the lattice cavities of HNIW, and it enhances the safety on the premise of maintaining its energy density.

Study on the thermal decomposition behavior of ammonium perchlorate catalyzed by Zn–Co cooperation in MOF

The combustion performance of solid propellants plays a decisive role in the overall application of rockets.

Smart Host-Guest Energetic Material Constructed by Stabilizing Energetic Fuel Hydroxylamine in Lattice Cavity of 2,4,6,8,10,12-Hexanitrohexaazaisowurtzitane Significantly Enhanced the Detonation, Safety, Propulsion, and Combustion Performances

The host-guest inclusion strategy has become a promising method for developing novel high-energy density materials (HEDMs). The selection of functional guest molecules was a strategic project, as it can not only enhance the detonation performance of host explosives but can also modify some of their suboptimal performances. Here, to improve the propulsion and combustion performances of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW), a novel energetic-energetic host-guest inclusion explosive was obtained by incorporating energetic rocket fuel, hydroxylamine (HA), into the lattice cavities of HNIW. Based on their perfect space matching, the crystallographic density of HNIW-HA was determined to be 2.00 g/cm³ at 296 K, which has reached the gold standard regarding the density of HEDMs. HNIW-HA also showed higher thermal stability (T_d = 245.9 °C) and safety (H₅₀ = 16.8 cm) and superior detonation velocity (D_V = 9674 m/s) than the ε-HNIW. Additionally, because of the excellent combustion performance of HA, HNIW-HA possessed higher propulsion performances, including combustion speed (S_C = 39.5 mg/s), combustion heat (Q_C = 8661 J/g), and specific impulse (I_sp = 276.4 s), than ε-HNIW. Thus, the host-guest inclusion strategy has potential to surpass the limitations of energy density and suboptimal performances of single explosives and become a strategy for developing multipurpose intermolecular explosives.

Energetic Co-Crystal of a Primary Metal-Free Explosive with BTF. Ideal Pair for Co-Crystallization

Co-crystallization is an elegant technique to tune the physical properties of crystalline solids. In the field of energetic materials, co-crystallization is currently playing an important role in the engineering of crystals with improved performance. Here, based on an analysis of the structural features of the green primary explosive, tetramethylammonium salt of 7-oxo-5-(trinitromethyl)-4,5,6,7-tetrahydrotetrazolo[1,5-a][1,3,5]triazin-5-ide (1), a co-former such as the powerful secondary explosive, benzotrifuroxan (BTF, 2), has been proposed to improve it. Compared to the original 1, its co-crystal with BTF has a higher detonation pressure and velocity, as well as an initiating ability, while the impact sensitivity and thermal stability remained at about the same level. Both co-formers, 1 and 2, and co-crystal 3 were characterized by single-crystal X-ray diffraction and their crystal packing was analyzed in detail by the set of approaches, including periodic calculations. In the co-crystal 3, all intermolecular interactions were significantly redistributed. However, no new types of intermolecular interactions were formed during co-crystallization. Moreover, the interaction energies of structural units in crystals before and after co-crystallization were approximately the same. A similar trend was observed for the volumes occupied by structural units and their densifications. The similar nature of the organization of the crystals of the co-formers and the co-crystal gives grounds to assert that the selected co-formers are an ideal pair for co-crystallization, and the invariability of the organization of the crystals was probably responsible for the preservation of some of their properties.

Performance and Sensitivity Properties of Solid Heterogeneous Rocket Propellant Based on a Binary System of Oxidizers (PSAN and AP)

Solid heterogeneous rocket propellants (SHRP) containing ammonium perchlorate (AP) emit a lot of hydrogen chloride (HCl) during combustion, which poses various environmental issues and makes the detection of the rockets easier. Part of the AP can be replaced by ammonium nitrate (V) (AN), which does not lead to the production of HCl. AN is a commonly used environmentally friendly oxidizer, but it is not usually applied in SHRP due to its disadvantages. One of these disadvantages is a phase transition near room temperature, which causes the density change of AN. Three types of phase stabilized ammonium nitrate (V) (PSAN) with inorganic potassium salts were obtained in order to shift this transition into higher temperatures (above the temperature range of the storage and the usage of SHRP). The SHRP with the PSAN were obtained, and the measurements of the heat of combustion, density, hardness, the sensitivity to mechanical stimuli and the thermomechanical properties were performed. The obtained propellants were characterized by similar operational parameters or were slightly lower than those without the PSAN. This means that AP can be partially replaced without significantly compromising the handling, safety or functionality of the propellants, while increasing the environmental performance of the solution.

Enhanced thermal and energetic properties of NC-based nanocomposites with silane functionalized GO

The surface functionalization of graphene oxide (GO) is always attractive in improving certain properties of the polymer. In this study, 3-aminopropyltriethoxysilane (APTES) and 3-mercaptopropyl-trimethoxysilane (SPTES) have been used to make silane functionalized graphene oxides (SiGOs). The APTES-grafted GO (NH-SiGO), SPTES-grafted GO (SH-SiGO) and pure GO have been separately introduced into the nitrocellulose (NC) matrix. The morphology, thermal properties and energetic properties of the prepared nanocomposites (NH-SiGO and SH-SiGO) were investigated comprehensively. It is shown that the presence of GO and SiGOs have different influences on the thermal reactivity of NC with various contents, and NH-SiGO with 0.5 wt% content showed better catalytic performance on the thermal decomposition of NC than others and showed prominently higher efficiency in improving its heat of combustion. Adding 0.5 wt% of NH-SiGO to NC may decrease its decomposition temperature from 202.1 °C to 196.6 °C, and the residue was decreased from 10.61 wt% to 3.95 wt%, respectively. One isoconversional kinetic method was exploited to determine the kinetic parameters of NC and its nanocomposites. It was found that NH-SiGO had a strong catalytic action on the thermal decomposition of NC-based nanocomposites for which the activation energy and the pre-exponential factor were considerably lowered, while SH-SiGO exhibited an inverse effect. The heat of combustion from NC/GO/0.5, NC/NH-SiGO/0.5 and NC/SH-SiGO/0.5 were determined as 11 249.5, 11 675.1 and 11 491.5 J g^-1, respectively, which are higher than that of the pure NC (10 908.4 J g^-1). From the combustion process of NC/NH-SiGO/0.5, it was shown that the nanocomposite was combusted completely.

Solid Propellant Formulations: A Review of Recent Progress and Utilized Components

The latest developments in solid propellants and their components are summarized. Particular attention is given to emerging energetic binders and novel, 'green' oxidizing agents and their use in propellant formulations. A brief overview of the latest reports on fuel additives is included. Finally, a summary of the state of the art and challenges in its development are speculated on.

Optimized energetic HNTO/AN co-crystal and its thermal decomposition kinetics in the presence of energetic coordination nanomaterials based on functionalized graphene oxide and cobalt

The present research aims to select the optimal molar ratio of hydrazine 3-nitro-1,2,4-triazol-5-one (HNTO) and ammonium nitrate (AN) to produce an energetic co-crystal. For a comparison purpose, the heat release, cost, density and hygroscopicity of the different co-crystals were evaluated. The obtained results indicated that HNTO/AN at the 1 : 3 ratio exhibited a higher heat release, better thermal stability, low water content and a reasonable cost, compared to other co-crystals. This new co-crystal was fully characterized through powder X-ray diffraction (XRD), infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), confirming that this latter displayed similar characteristics to those of the co-crystal with a 1 : 1 ratio, which was recently developed. On the other hand, the catalytic activity of two energetic coordination polymers of triaminoguanidine-cobalt (T-Co) complexes, with or without graphene oxide (GO-T-Co-T), on the thermolysis of the developed co-crystal has been also assessed by DSC under non-isothermal conditions. It is revealed that these catalysts have greatly decreased the decomposition temperature of the HNTO/AN cocrystal. Moreover, because of the complete decomposition in the case of the (HNTO/AN)/GO-T-Co-T composite, the heat release has been increased as well. Isoconversional integral kinetic methods were exploited to determine the kinetic parameters of the different systems. According to the obtained results, these catalysts have a strong catalytic action on the decomposition of the co-crystal AN/HNTO for which the activation energy and the pre-exponential factor are considerably lowered. Consequently, the developed co-crystal and the energetic catalysts could be considered as potential ingredients for the next generation of composite solid propellant formulations.

Kinetic Stability of Pentazole

The utility of high energy density materials (HEDMs) comes from their thermodynamic properties which arise from specific structural features that contribute to energy storage. Studies of such structural features seek to increase our understanding of these energy storage mechanisms in order to further enhance their properties. High-nitrogen-containing HEDMs are of particular interest because they are less toxic than traditional HEDMs. Pentazole is the largest of the nitrogen rings which has been synthesized and considered for an HEDM; however, few experimental studies exist due to the difficulty involved in the synthesis, and most previous theoretical studies employed composite methods where lower level geometries were used with higher level methods. Here, the decomposition reaction of pentazole is studied. Geometries, fundamental frequencies, and energies for each of the stationary points of the decomposition pathway are computed using ab initio methods up to CCSDT(Q). Decomposition rates are calculated over a range of temperatures using canonical transition state theory in order to determine the kinetic stability of pentazole. Based on the present results, it would be difficult for pentazole to act as an HEDM, requiring temperatures close to 200 K to achieve a suitable level of stability.

Contemporary biomedical engineering perspective on volitional evolution for human radiotolerance enhancement beyond low-earth orbit

A primary objective of the National Aeronautics and Space Administration (NASA) is expansion of humankind's presence outside low-Earth orbit, culminating in permanent interplanetary travel and habitation. Having no inherent means of physiological detection or protection against ionizing radiation, humans incur capricious risk when journeying beyond low-Earth orbit for long periods. NASA has made large investments to analyze pathologies from space radiation exposure, emphasizing the importance of characterizing radiation's physiological effects. Because natural evolution would require many generations to confer resistance against space radiation, immediately pragmatic approaches should be considered. Volitional evolution, defined as humans steering their own heredity, may inevitably retrofit the genome to mitigate resultant pathologies from space radiation exposure. Recently, uniquely radioprotective genes have been identified, conferring local or systemic radiotolerance when overexpressed in vitro and in vivo. Aiding in this process, the CRISPR/Cas9 technique is an inexpensive and reproducible instrument capable of making limited additions and deletions to the genome. Although cohorts can be identified and engineered to protect against radiation, alternative and supplemental strategies should be seriously considered. Advanced propulsion and mild synthetic torpor are perhaps the most likely to be integrated. Interfacing artificial intelligence with genetic engineering using predefined boundary conditions may enable the computational modeling of otherwise overly complex biological networks. The ethical context and boundaries of introducing genetically pioneered humans are considered.

Synthesis and Stability of Hydrogen Storage Material Aluminum Hydride

Aluminum hydride (AlH₃) is a binary metal hydride with a mass hydrogen density of more than 10% and bulk hydrogen density of 148 kg H2/m3. Pure aluminum hydride can easily release hydrogen when heated. Due to the high hydrogen density and low decomposition temperature, aluminum hydride has become one of the most promising hydrogen storage media for wide applications, including fuel cell, reducing agents, and rocket fuel additive. Compared with aluminum powder, AlH₃ has a higher energy density, which can significantly reduce the ignition temperature and produce H₂ fuel in the combustion process, thus reducing the relative mass of combustion products. In this paper, the research progress about the structure, synthesis, and stability of aluminum hydride in recent decades is reviewed. We also put forward the challenges for application of AlH₃ and outlook the possible opportunity for AlH₃ in the future.

NOx removal with efficient recycling of NO2 from iron-ore sintering flue gas: A novel cyclic adsorption process

Conventional flue gas nitrogen oxides (NO_x) abatement technologies commonly convert NO_x into harmless compounds, while less effort has been made to recycle NO₂ as a profitable chemical in many industries. Towards this end, adsorption is a promising technology for which an advanced technique for NO₂ desorption and efficient sorbent regeneration provides the key step for success in practical applications. This work reports a novel cyclic adsorption process for NO_x removal with recycling of NO₂ from iron-ore sintering flue gas of a steel plant. This process using self-prepared and validated pelletized Na-ZSM-5 zeolites as low-cost sorbents involves NO_x catalytic adsorption and reversible desorption using multiple hot gas circulations (GC) within the enclosed fixed bed followed by scavenging and purge at mild conditions. In comparison to conventional cyclic processes, greater amount of recyclable NO₂ was obtained, rendering the NO_x recovery of >92% and the mean NO₂ concentration of >2% significantly enriched from original 20 ppm in feed gas. A robust adsorption-desorption performance with appreciable NO_x working capacity was achieved for up to 16 cycles. The key role of the segmentation of GC in boosting NO_x regenerability was addressed, providing an economical three-tower strategy for continuous NO₂ production for practical use.

Facile synthesis of MXene-supported copper oxide nanocomposites for catalyzing the decomposition of ammonium perchlorate

MXene-supported CuO nanocomposites were synthesized by ice crystal templating and could effectively reduce the HTD temperature and increase the heat release of AP. A possible mechanism for the excellent catalytic performance was also proposed.

Nanoenergetic Materials: Preparation, Properties, and Applications

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