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

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.