Hematite: A Good Catalyst for the Thermal Decomposition of Energetic Materials and the Application in Nano-Thermite

Metal oxides (MOs) are of great importance in catalysts, sensor, capacitor and water treatment. Nano-sized MOs have attracted much more attention because of the unique properties, such as surface effect, small size effect and quantum size effect, etc. Hematite, an especially important additive as combustion catalysts, can greatly speed up the thermal decomposition process of energetic materials (EMs) and enhance the combustion performance of propellants. This review concludes the catalytic effect of hematite with different morphology on some EMs such as ammonium perchlorate (AP), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenete-tranitramine (HMX), etc. The method for enhancing the catalytic effect on EMs using hematite-based materials such as perovskite and spinel ferrite materials, making composites with different carbon materials and assembling super-thermite is concluded and their catalytic effects on EMs is also discussed. Therefore, the provided information is helpful for the design, preparation and application of catalysts for EMs.

Polymeric Carbon Nitride/Iron Oxide Composites: A Novel Class of Catalysts with Reduced Metal Content for Ammonium Perchlorate Thermal Decomposition

The ever-growing number of space launches triggering an enormous release of metallic dead weight into the atmosphere has become a global concern. Despite technological advancements, the inclusion of environmental concerns in space research has become the need of the hour. Here, we report the impact of iron oxide (Fe₂O₃)-doped polymeric carbon nitride (gCN) composites with varying metal contents (namely, GF1, GF2, and GF3 with iron contents of 0.1, 0.25, and 2 mmol, respectively) as a new class of catalysts for ammonium perchlorate (AP) thermolysis. Morphology studies revealed the dendritic morphology of the synthesized Fe₂O₃, and X-ray photoelectron spectroscopy (XPS) analysis confirmed the effective interaction between Fe₂O₃ and gCN in the composites. Among all of the synthesized composites, GF2 shows superior catalytic competence toward AP decomposition by amalgamating the double-stage decomposition process into a single stage followed by a considerable decrease in the decomposition temperature. The kinetic parameters calculated for the thermal decomposition of AP with and without catalysts using the KAS method substantiated the above results by significantly reducing the activation energy from 173.2 to 151.7 kJ/mol. Later, thermogravimetric and mass-spectrometric (TG-MS) analysis gives a clear idea about the catalytic efficiency of the synthesized catalyst GF2 toward AP decomposition from the accelerated emission of decomposition products NO, NO₂, Cl, HCl, Cl₂, and N₂O in the presence of GF2. In a nutshell, gCN/Fe₂O₃ will open up new horizons in the field of synthesis of new catalytic systems with minimal metal content for composite solid propellants.

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.

A nanozyme-catalysis-based ratiometric electrochemical sensor for general detection of Cd2+

AuPt–rGO showed good peroxidase-like activity for the oxidation of OPD to DAP (a novel internal reference) and achieved sensitive and reliable detection of Cd2+ based on a ratiometric strategy.

Preparation of different morphology Cu/GO nanocomposites and their catalytic performance for thermal decomposition of ammonium perchlorate

Cu nanoparticles are more active catalytically than CuO nanoparticles, which have been widely studied as catalysts for organic synthesis, electrochemistry, and optics. However, Cu nanoparticles are easily agglomerated and oxidized in air. In this research, columnar, flower-like, bubble-like and teardrop-shaped Cu/GO nanocomposites were fabricated via a water-solvent thermal method and high temperature calcination technique using deionized water (H₂O), methanol (CH₃OH), ethanol (CH₃CH₂OH) and ethylene glycol (EG) as the solvent, respectively. The structures, the morphology and the catalytic performance and catalytic mechanism for thermal decomposition of ammonium perchlorate (AP) of the Cu/GO nanocomposites have been studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen adsorption tests (BET), simultaneous thermogravimetry-differential scanning calorimetry (TGA/DSC) and thermogravimetric couplet with Fourier transform infrared spectroscopy (TGA–FTIR), respectively. The experimental results show that the morphology of the Cu/GO nanocomposites has a significant effect on the surface area and the teardrop-shaped Cu/GO nanocomposites have the largest specific surface area and the best catalytic performance among them. When 5 wt% of the Cu/GO nanocomposites was added, the decomposition temperature of AP decreased from 426.3 °C to 345.5 °C and the exothermic heat released from the decomposition of AP increased from 410.4 J g⁻¹ to 4159.4 J g⁻¹. In addition, the four morphological Cu/GO nanocomposites exhibited good stability, their catalytic performance for thermal decomposition of AP remained stable after 1 month in air. Excellent catalytic performance and stability were attributed to the strong catalytic activity of pure metal nanoparticles, and GO can accelerate electron movement and inhibit the agglomeration of nanoparticles, as well as the multiple effects of inhibiting the oxidation of Cu nanoparticles in air. Therefore, it has important application potential in high-energy solid propellant.

Cu nanoparticles are more active catalytically than CuO nanoparticles, which have been widely studied as catalysts for organic synthesis, electrochemistry, and optics.

Effect of Bi2WO6/g-C3N4 composite on the combustion and catalytic decomposition of energetic materials: An efficient catalyst with g-C3N4 carrier

An effective strategy involving a suitable carrier is needed to improve the dispersion, combustion and catalytic performances of catalyst nanoparticles. Herein, a Bi₂WO₆/g-C₃N₄ composite employing g-C₃N₄ as the catalyst carrier was prepared by a one-step in situ hydrothermal method, which was used as the combustion catalyst of solid propellants. The catalyst's structure, morphology and its catalytic decomposition on several energetic materials were characterized by a series of analyses. The optimal ratio of g-C₃N₄ and Bi₂WO₆ was systematically determined. The results demonstrate that Bi₂WO₆/g-C₃N₄ (4:6) composite can diminish the decomposition temperatures of ammonium perchlorate (AP), cyclotrimethylenetrinitramine (RDX), dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) and cyclotrimethylenetrinitramine + nitrocellulose (RDX + NC) by 25.0, 5.2, 24.0 and 1.2 (4.9) ° C, and reduce their apparent activation energy by 59.5, 116.7, 11.6 kJ mol^-1, respectively. Moreover, the laser ignition tests indicate that Bi₂WO₆/g-C₃N₄ can effectively promote the ignition performance of RDX and RDX + NC. A possible mechanism of Bi₂WO₆/g-C₃N₄ on AP was proposed. The g-C₃N₄ catalyst carrier is superior to GO carrier due to its low cost, simple synthesis process, improved combustion and catalytic performances, as well as high N content. These make it have broad engineering application prospects in solid propulsion and other energetic materials.

Ferrocene functionalized graphene: preparation, characterization and application as an efficient catalyst for the thermal decomposition of TKX-50

Novel ferrocene functionalized graphene with different molecular structures were designed, fabricated and characterized via SEM, EDS, FTIR, XPS and RAMAN methods. SEM results show the two-dimensional structure of the as-prepared catalysts, and the active metal Fe is uniformly distributed on the surface of graphene. The FTIR, XPS and RAMAN results confirmed the successful preparation of ferrocene functionalized graphene. The catalytic effects of the as-synthesized catalysts for the thermal decomposition of energetic TKX-50 were monitored by DSC, and the corresponding kinetic parameters were calculated using multi kinetic methods including traditional and nonlinear models. The results showed that the as-prepared ferrocene functionalized graphene can effectively promote the thermal decomposition of TKX-50 with the reduced decomposition peak temperatures and activation energies. In addition, the effects of ferrocene functionalized graphene for TKX-50 decomposition are reflected in both high and low temperature stages, and the effect on the high temperature stage is more significant. The outstanding catalytic activity of ferrocene functionalized graphene is related not only to the good dispersion of active Fe, but also to the enhanced interaction of small molecule products on two-dimensional graphene. Among the ferrocene functionalized graphene studied, G-792-Fe and G-902-Fe exhibit better catalytic effects on the thermal decomposition of TKX-50, which can be used as candidate catalysts for TKX-50-based solid propellants.

Surface-tuned hierarchical ɤ-Fe2O3-N-rGO nanohydrogel for efficient catalytic removal and electrochemical sensing of toxic nitro compounds

4- Nitrophenol (4-NP) is a top rated hazardous environmental pollutant and secondary explosive chemicals. For the sake of ecology and environment safety, the catalytic reduction and detection of 4-NP is highly important. In this work, ɤ-Fe₂O₃-nitrogen doped rGO (ɤ-Fe₂O₃-N-rGO) nanohydrogel was synthesized by green hydrothermal method. The morphology and phase purity of prepared ɤ-Fe₂O₃-N-rGO nanohydrogel were confirmed by various analytical (SEM, TEM, XRD, and XPS) and electrochemical techniques. The morphological structure of ɤ-Fe₂O₃-N-rGO nanohydrogel confirmed that the nanocrystals are well covered over the 2D N-rGO layer. Further, ɤ-Fe₂O₃-N-rGO nanohydrogel was applied for the catalytic reduction and electrochemical detection of ecotoxic 4-NP. A low cost, ɤ-Fe₂O₃-N-rGO nanohydrogel displayed an excellent catalytic activity, high recyclability (>5 cycles) and high conversion efficiency of 4-NP to 4-Aminophenol (4-AP). In addition, ɤ-Fe₂O₃-N-rGO nanohydrogel modified GCE displayed a wide linear sensing range (0.1-1000 μM), and a low detection limit (LOD) of 0.1 μM with excellent sensitivity, high selectivity (<1.2%) and good stability (>4 weeks). The developed sensor electrode shows the low reduction potential of -0.3 V and -0.60 V for the determination of 4-NP. The proposed ɤ-Fe₂O₃-N-rGO nanohydrogel is promising catalyst for the detection and removal of toxic aromatic nitro compounds in real site applications.

Glycerol-controlled synthesis of a series of cobalt acid composites and their catalytic decomposition toward several energetic materials

One of the challenges in solid propellant formulation is the ability to extend the combustion performance by efficiently catalyzing the decomposition of energetic additives.

Preparation, characterization of spherical 1,1-diamino-2,2-dinitroethene (FOX-7), and study of its thermal decomposition characteristics

The sensitivity and properties of energetic materials strongly depend on their crystal morphology. In this article, spherical 1,1-diamino-2,2-dinitroethylene (FOX-7) was produced via a combination of the cooling crystallization method and repeated grinding technique. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), optical microscopy, scanning electron microscopy (SEM) and laser particle size analysis were used to characterize the structure, infrared characteristics, morphology, and particle size of the product. The results show that the obtained product has a smoother spherical morphology with granularity gradation and shows similar diffraction peak positions to raw FOX-7. Differential scanning calorimetry (DSC), thermal gravimetry (TG), and accelerating rate calorimetry (ARC) were used to analyse the thermal behavior of spherical FOX-7 under nonisothermal and adiabatic conditions. The thermal performance test results show that spherical FOX-7 releases energy faster and releases more energy as compared to raw FOX-7. These findings showed that the cooling crystallization method combined with the repeated grinding technique is suitable for efficient preparation of spherical FOX-7, which could greatly improve the thermal stability of FOX-7.

Spherical FOX-7 was produced via a combination of cooling crystallization method and repeated grinding technique, and the crystal morphology, size, structure, and thermal behavior were systematically investigated in detail.

Unusual Cu-Co/GO Composite with Special High Organic Content Synthesized by an in Situ Self-Assembly Approach: Pyrolysis and Catalytic Decomposition on Energetic Materials

An interesting Cu-Co/GO composite with special high organic content was accidentally fabricated for the first time via a one-pot solvothermal method in the mixed solvent of isopropanol and glycerol. The Cu-Co/GO composite was calcined separately in three different atmospheres (air, nitrogen, and argon) and further investigated by a series of characterization techniques. The results indicate that the spinel phase nano-CuCo₂O₄ composite, nanometal oxides (CuO and CoO), and nanometal mixture of Cu and Co were unexpectedly formed after calcination in air, N₂, and Ar atmospheres, respectively, and the possible reaction mechanism was discussed. The specific mass losses of the Cu-Co/GO composite calcined in air, N₂, and Ar atmospheres were 28.14 %, 21.68 %, and 23.76 %, respectively. The catalytic decomposition performances of the as-prepared samples for cyclotrimethylenetrinitramine (RDX) and the mixture of nitrocellulose (NC) and RDX (NC + RDX) were investigated and compared via DSC method, and the results demonstrate that Cu-Co/GO composites obviously decrease the thermal decomposition temperature of RDX from 242.3 to 236.5 (before calcination), 238.6 (air), 235.8 (N₂), and 228.6 °C (Ar), respectively. Cu-Co/GO(Ar) composite exhibits the best catalytic decomposition performance among all samples, which makes the decomposition temperature of RDX and NC + RDX decrease by 13.7 and 4.9 °C and the apparent activation energy of decomposition for RDX decrease by 110.1 kJ/mol. The enhanced catalytic performance of Cu-Co/GO(Ar) composite could be attributed to the smaller particle size, better crystallinity, and specific well-dispersed metal atoms, whereas the Cu-Co/GO(air) composite after air calcination presents a bad catalytic performance due to the removal of GO.

The catalytic effects of nano-Fe2O3 and rGO–Fe2O3 on the thermal decomposition properties of CL-20/HMX cocrystals

Adding nano-Fe₂O₃ to a CL-20/HMX cocrystal affects its thermal decomposition peak temperature and products.