Promotion of the Co3O4/TiO2 Interface on Catalytic Decomposition of Ammonium Perchlorate

Efficiently Constructed Core-Shelled Structured AP-Based Composites with Excellent Balance of High Energy Release and Low Sensitivity

Ammonium perchlorate (AP) plays an important role in solid propellants because of its high specific impulse, high energy density and low cost. However, the excellent performance cannot conceal the many shortcomings of AP, and the problems of non-concentrated exothermic, high sensitivity and hygroscopicity still seriously impede its application in solid propellants. In this study, the solvent evaporation method is used to directionally modify the order of the cupric oxide (CuO) and fluororubber (F2603) shell layers so as to obtain AP-based composites with different core-shell structures. The interlayer binding energies of the composites with different structures are explored by theoretical calculations, and it is demonstrated that AP-based composites have excellent stability. In addition, CuO with valence-band holes not only reduces the peak temperature of the high temperature decomposition of AP (440.4 to 354.5 °C), but also enhances its combustion properties by undergoing thermite reaction with Al. Furthermore, the excellent hydrophobicity and barrier properties of F2603 greatly strengthened the hydrophobicity and mechanical properties of the AP-based composites and reduced their sensitivity. In summary, the core-shelled structures AP-based composites prepared by this strategy possessed 5-in-1 excellent properties, which provided a new idea for targeted modulation of the properties of energetic materials.

Droplet and solution contact assembled cobalt alginate for enhanced properties of ammonium perchlorate

Ammonium perchlorate (AP), a widely used oxidizer in solid propellants, requires the incorporation of combustion catalysts to enhance its thermal decomposition efficiency. However, such modifications often compromise safety performance. Inspired by the rapid metal-ion-induced gelation of sodium alginate (Na-A), this study introduces a novel "droplet-solution contact assembly" strategy to encapsulate AP within a three-dimensional porous network framework derived from cobalt alginate (Co-A), thereby fabricating spherical AP/Co-A composites with simultaneously improved catalytic activity and safety. During thermal decomposition, Co-A breaks down into catalytically active nano-Co3O4 particles uniformly dispersed on a carbonized porous framework. The unique architecture facilitates efficient charge transfer and synergistically accelerates AP decomposition. In the event of collision and friction, the spherical morphology of AP/Co-A minimizes localized hot spot formation under mechanical stress, while the organic framework formed by Co-A functions as a spring-like buffer network to alleviate collision and friction energy, significantly enhancing the safety performance. The study provides a simple and safe preparation method for spherical composite materials and offers novel insights into its design.

Efficient construction of core/double-shelled structured AP@nano-graphite@F2603 energetic microcapsules with low sensitivity and hygroscopicity

Ammonium perchlorate (AP) is widely utilized in aerospace, defense and other fields due to its high energy density, exceptional stability, easy availability and adaptability. However, the high sensitivity and hygroscopicity of AP severely constrain its application in numerous fields. In this study, a two-step continuous coating method was employed to construct AP-based energetic microcapsules with low sensitivity and hygroscopicity. The formation process of the F2603 shell on the AP@nano-graphite surface was simulated using Materials Studio (MS), which proved the rationality of the shell formation process. In addition, the excellent electrical and thermal conductivity of the nano-graphite shell combined with the superior hydrophobicity and thermal insulation of the F2603 shell advanced the high-temperature decomposition process of the AP-based energetic microcapsules, enhanced the hydrophobicity of the AP (the water contact angle increased from 0° to 73° and the hygroscopic rates decreased from 0.132% to 0.051%), and reduced the impact sensitivity of the AP (the H50 value increased from 42.2 cm to 86.6 cm). Clearly, the diverse materials in the shell layer could endow the core AP with multiple functions. Therefore, this meaningful work provides a novel and extensive strategy to improve the performance of AP-based energetic microcapsules.

Earth-abundant catalyst for modification of wheat straw to enhance ammonia mitigation from fertilized alkaline soil

In this study, inexpensive earth-abundant catalyst of Co/TiO2 is coupled with a low-temperature modification approach to enhance NH3 adsorption capacity on wheat straw (WS). The highest NH3 uptake achieved is 111.9 mg/g, with 80.8 % retention even after 3 h of desorption. Mechanistic investigation indicates that the enhanced adsorption capacity stems from Co/TiO2, which facilitates generation of reactive oxygen species, leading improved ultra-micropore structure that enhances the interaction between NH3 and oxygen-containing functional groups through a trapping effect. The robust stability of adsorbed NH3 is attributed to the formation of amides or amines. Incorporation of only 1 wt% WS-Co to urea-fertilized alkaline soil reduced NH3 volatilization by 83.1 %. The significant effect is primarily attributed to the excellent adsorption capacity of WS-Co, rather than alterations in the relative abundance of the microbial community. These findings present a novel approach for development of effective fertiliser additive to mitigate NH3 volatilization from alkaline soil.

Research progress on the catalytic and thermal decomposition of ammonium dinitramide (ADN)

Ammonium dinitramide (NH4N(NO3)2, ADN) is regarded as a promising oxidizer due to its low signature and high specific impulse. Generally, ADN undergoes exothermic decomposition above 140 °C accompanied by the byproduct of ammonium nitrate (AN). The inevitable endothermic decomposition of AN decreases the overall heat release, and so there is a need to develop efficient catalysts to guide ADN decomposition along desired pathways with a lower decomposition temperature and higher heat release. A suitable catalyst should be able to withstand the harsh conditions in a thruster to achieve a stable thrust force, which poses a huge obstacle for manufacturing a stable and active catalyst. This review gives a comprehensive summary of the thermal and catalytic decomposition pathways of ADN for the first time, which is expected to deepen the understanding of its reaction mechanism and provide useful guidance for designing prospective catalysts toward efficient ADN decomposition.

Proficient sonophotocatalytic degradation of organic pollutants using Co3O4/TiO2 nanocomposite immobilized on zeolite: Optimization, and artificial neural network modeling

The health of all living organisms is greatly influenced by the quality of the water. Therefore, developing cost-effective, eco-friendly, and easily accessible methods is desperately needed to meet the high global demand for clean water. Recently, nanozyme-based dye degradation methods have been promising for the remediation of water pollution. In this work, peroxidase-mimic Co3O4/TiO2 nanocomposite was synthesized and characterized for its size, morphology, and crystalline structure. Colorimetric assay results showed that the peroxidase-like activity of the Co3O4/TiO2 nanocomposite was considerably enhanced compared to the pure Co3O4 NPs and TiO2 NPs. Besides excellent enzyme-mimic activity, the higher sonophotocatalytic dye degradation capability of the nanocomposite after immobilization on zeolite (Co3O4/TiO2@Ze) was also demonstrated. Under optimal conditions (pH = 5.0, 25 °C), 0.1 g/L of catalyst was able to degrade 100 % of methylene blue (MB) with 600 μM in the presence of 30 μM H2O2 within 12 min. GC/MS analysis and toxicity studies revealed less toxic metabolite production after treatment of MB with sonophotocatalytic Co3O4/TiO2@Ze. Modeling of MB degradation using artificial neural networks (ANN) with a 5:6:1 topology was successfully performed, and the results confirmed the fitness of theoretical and experimental outputs according to the calculated correlation coefficient values. The prepared nanocomposite could thus be used as a promising and highly effective catalyst for the removal of organic dyes from polluted water.

In situ growth of copper-based energetic complexes on GO and an MXene to synergistically promote the thermal decomposition of ammonium perchlorate

In this work, using tri(5-aminotetrazolium)triazine (H3TATT) as an energetic ligand, two new energetic complexes (ECs), Cu(HTATT)(H2O)2 (EC-Cu1) and [Cu3(TATT)2(H2O)2]n (EC-Cu2), have been synthesized under hydrothermal conditions. Their crystal structures, thermal decomposition behaviors and specific heat capacities were determined respectively. In addition, two ECs were combined with GO (graphene oxide) and an MXene (Ti3C2TX) respectively by an in situ growth strategy to obtain four carbon nanomaterials/EC composites, which were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The effects of two ECs and four composites on the thermal decomposition of AP were studied by differential scanning calorimetry (DSC). Among them, the sample containing 8 wt% composite (GO/EC-Cu2) has the best promoting effect on AP, causing the high temperature decomposition peak to overlap with the low temperature decomposition peak of AP, reducing the decomposition peak temperature of AP from 443.6 °C to 308.9 °C, and the heat release is up to 4875 J g-1. Compared with ECs acting solely on AP, composite materials have stronger synergistic and promoting effects. This study provides a new example of the synthesis of carbon nanomaterial/EC composites and the improvement of the performance of AP-based solid propellants.

Construction of Hydrophobic Ammonium Perchlorate with Synergistic Catalytic Effect Based on Supramolecular Self-Assembly for Synchronously Catalyzing the Thermal Decomposition of Ammonium Perchlorate and the Combustion of Aluminum

Ammonium perchlorate (AP), as an important additive component of composite propellants, is critical to the combustion performance of propellants. Herein, AP@1H,1H,2H,2H-perfluorodecyltrichlorosilane (AP@PF) was prepared by establishing a tannic acid-iron ion (TA-Fe) supramolecular self-assembly layer on the AP surface and connecting the 1H,1H,2H,2H-perfluorodecyltrichlorosilane interfacial layer. Results demonstrate that TA-Fe and 1H,1H,2H,2H-perfluorodecyltrichlorosilane are uniformly bound to the surface layer of AP. AP@PF has a lower high-temperature thermal decomposition peak compared to AP. Meanwhile, the exothermic values of low-temperature thermal decomposition (338 J/g) and high-temperature thermal decomposition (597 J/g) of AP@PF are significantly higher than those of AP. In addition, AP@PF exhibits different surface interfacial properties, such as floating on the water surface and exhibiting a static contact angle of 105° on water. AP@PF shows almost no moisture absorption after aging in humid air for 30 days. The exothermic value of the mixture of AP@PF and aluminum powder (156 J/g) is significantly higher than that of the mixture of AP and aluminum (54 J/g), and the mixture of AP@PF and aluminum powder exhibits a higher calorific value and a stronger emission spectrum. Finally, the synergistic catalytic mechanism of AP@PF on the thermal decomposition of AP and the combustion of aluminum powder is also discussed.

In Situ Cutting of Ammonium Perchlorate Particles by Co-Bipy "scalpel" for High Efficiency Thermal Decomposition

Burning rate of solid propellants can be effectively improved by adding catalysts and using smaller size ammonium perchlorate (AP). Although few reports, the exploration of changing the size of AP primary particles by catalysts is of great significance for improving combustion performance. Here, taking Co-bipy as an example, the potential advantages of such materials as AP decomposition catalysts are reported. Due to the existence of NO3 - combined with oxygen rich environment provided by AP, the structural self-transformation from micronrods to nanoparticles can be quickly realized during the heating process. More importantly, when Co-bipy decomposes, it can play the role of "scalpel" and in situ cut AP particles. Results show that high-temperature decomposition of Co-bipy/AP occurs at 305.8 °C, which is 137.5 °C lower than that of pure AP. Catalytic mechanism is discussed by in situ IR and TG-IR, CoO can effectively increase the content of reactive oxygen species and weaken the N-H bond, realizing the rapid oxidation of NH3 . Eventually, the behavior of Co-bipy cutting AP particles is tested. This interesting catalyst structure self-transformation behavior can not only realize the influence on AP, but also perform a positive function in the combustion process of solid propellants, such as opening the adhesive AP interface.