Decomposition Process Of Ammonium Perchlorate Research Articles

Constructing the combination bridge of aluminum hydride (AlH3) and polyvinylidene fluoride (PVDF) through the self-assembly of dopamine: Improving the stability and ignition properties of AlH3

Surface coating is an important method to solve the poor stability of aluminum hydride (AlH3). To overcome the difficulty of uneven coating of fluorine-containing polymers on the surface of AlH3, this study utilizes the adhesion properties of polydopamine (PDA) to establish a bridge between the oxide layer of AlH3 (Al2O3) and polyvinylidene fluoride (PVDF), so that Polyvinylidene fluoride (PVDF) was uniformly coated on the AlH3 surface, and a dual-core shell structure AlH3@PDA@PVDF composite was successfully prepared. Molecular dynamics simulations reveal significantly higher binding energy per unit area for γ-Al2O3@PDA/PVDF (1.2270 Kcal·mol−1·Å−2) compared to γ-Al2O3/PVDF (0.6644 Kcal·mol−1·Å−2), affirming that PDA can effectively enhance the interfacial interaction between AlH3 and PVDF. The morphology characterization and performance testing of raw AlH3 and AlH3@PDA@PVDF composite were carried out through SEM, XPS, FT-IR, DSC, VST, etc. The results indicate that through the interface modification of AlH3 by PDA, PVDF with a hydrophobic surface can be evenly coated on the surface of AlH3, causing the water contact angle (WCA) of the AlH3@PDA@PVDF composite to increase from 41° for the raw AlH3 to 124°. Furthermore, the total decomposition time of the AlH3@PDA@PVDF composite (2326 min) is improved by 1.8 times than that of the raw sample (1277 min), and its apparent activation energy (117.75 kJ·mol−1) was also higher than that of the raw sample (99.88 kJ·mol−1), indicating that coating with PDA and PVDF can improve the stability of AlH3. Ignition experiments demonstrate that the AlH3@PDA@PVDF composite has superior ignition reaction performance compared with the raw AlH3. Especially, adding a small amount of AlH3@PDA@PVDF composite can also significantly catalyze the thermal decomposition process of ammonium perchlorate (AP), reducing its high-temperature decomposition temperature from 405.37 °C to 352.20 °C.

Synthesis of Cu-MOF-derived complex copper–chromium oxides and their catalytic study on the thermal decomposition of ammonium perchlorate

In this work, a series of complex copper-chromium oxides were prepared by adjusting the molar ratio of Cr3+/Cu2+ using MOF-199 as a template. X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the structure, microscopic morphology and valence information of the samples. The specific surface area of the sample was estimated by the Brunauer-Emmett-Teller method (BET), and the pore size parameters of the sample were obtained by using the Barrett-Joyner-Halenda (BJH) model. The effect of the samples on the thermal decomposition process of ammonium perchlorate (AP) was investigated by differential scanning calorimetry-thermogravimetric analysis. The results show that the copper and chromium oxides in the complex exhibit good catalytic effects. Among them, CuCr(0.8) had the best catalytic effect, reducing the peak pyrolysis temperature of AP by 95.7 °C, increasing the heat release by 817 J/g, and reducing the reaction activation energy by 62.4 kJ/mol. Real-time FTIR was used to characterize the gas products during the thermal decomposition of AP, and the gas products of AP with CuCr(0.8) catalyst were different from those of pure AP, which may also be the reason for the increase of AP heat release after adding CuCr(0.8) catalyst.

MOF-74 derivatives spinel CuCo2O4/C with d-band center modulation for accelerating ammonium perchlorate thermolysis

As one of main components of solid propellant, ammonium perchlorate (AP) shows slow sluggish decomposition kinetics with unconcentrated heat release. In the past, researchers have done a lot of work using spinel oxides as combustion modifiers to improve the combustion performance of AP. However, AP decomposition process is very complicated, and the relationship between intrinsic activity of cobalt-based spinel catalysts and AP combustion process is still unclear. In this paper, a series of cobalt-based spinel structure catalysts, MCo2O4/C, were prepared by pyrolysis of cobalt-containing bimetal MOF-74 and used as AP combustion catalysts. All of them showed excellent catalytic performance, among which CuCo2O4/C had the best catalytic activity. It effectively reduces the activation energy of the reaction, speeds up the reaction rate, and reduces the peak temperature of the AP decomposition reaction by 161.2 ℃, and the reaction rate k is 10.28 times of Co3O4/C. XPS and NH3-TPD tests indicate that substitution CoTd2+ with Cu2+ increases the ratio of Co3+/Co2+ and enhance interaction between NH3 and catalyst. The essential reason is that Cu–O-Co corner sharing effect changes electron distribution and enhances CoOh3+ Lewis acidity accompanied with the proximity of d-band center to EF by density functional theory calculations.

Initiation Step in the Condensed Phase Decomposition Process of Ammonium Perchlorate

AbstractAmmonium perchlorate (AP) is a commonly used oxidizer in solid propellant compositions. As a result, numerous experimental and theoretical studies have been carried out in order to better understand the behavior of its decomposition in both the liquid and gas phases. In this work, the first step of Ammonium perchlorate (AP) decomposition in the condensed phase has been investigated using quantum mechanics‐based calculations. The process of proton transfer from ammonium ion (NH4+) to perchlorate ion (ClO4−) was investigated in‐depth as it is thought to be the preferred reaction for the initiation of AP decomposition in the condensed phase. The calculations were carried out using density functional theory (DFT) at the B3LYP level in conjunction with the 6‐311G++(d,p) basis set. The current study revealed that proton transfer from ammonium cation to perchlorate anion takes place in two steps. The first step involves the decomposition of ClO4− to ClO2− and O2 followed by the second step which is H+ transfer from NH4+ to ClO2− giving NH3 and HClO2. In order to better understand protonation and deprotonation, it is essential to know the proton affinity (PA) of the involved species. In this study, the CBS‐QB3 method is used to determine the PA of various energetic ionic compounds. These compounds include guanidinium azotetrazolate, triaminoguanidinium azotetrazolate, guanidinium nitrate, ammonium nitrate, and ammonium perchlorate. Based on the results of the calculations, it is concluded that direct proton transfer process does not occur in the condensed phase because the proton affinities of all cations are significantly higher than those of the corresponding anions. In conjunction with experimental studies, this modelling study can help in the development of a better understanding of AP decomposition in the condensed phase.

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

Supports can widely affect or even dominate the catalytic activity and selectivity of nanoparticles because atomic geometry and electronic structures of active sites can be regulated, especially at the interface of nanoparticles and supports. However, the underlying mechanisms of most systems are still not fully understood yet. Herein, we construct the interface of Co3O4/TiO2 to boost ammonium perchlorate (AP) catalytic decomposition. This catalyst shows enhanced catalytic performance. With the addition of 2 wt % Co3O4/TiO2 catalysts, AP decomposition peak temperature decreases from 435.7 to 295.0 °C and activation energy decreases from 211.5 to 137.7 kJ mol-1. By combining experimental and theoretical studies, we find that Co3O4 nanoparticles can be strongly anchored onto TiO2 supports accompanied by charge transfer. Moreover, at the interfaces in the Co3O4/TiO2 nanostructure, NH3 adsorption can be enhanced through hydrogen bonds. Our research studies provide new insights into the promotion effects of the nanoparticle/support system on the AP decomposition process and inspire the design of efficient catalysts.

Establishing the interface layer on the aluminum surface through the self-assembly of tannic acid (TA): Improving the ignition and combustion properties of aluminum

Aluminum powder is widely used in the field of propellants and explosives due to its high energy density. However, the dense oxide film on its surface will hinder the combustion of aluminum powder. Herein, Al@TA-Fe with core-shell structure was prepared by self-assembly of tannic acid (TA) and Fe(III) ion on the surface of aluminum, and was characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetry-differential scanning calorimetry (TG-DSC). The results show that the TA-Fe interface layer in Al@TA-Fe can effectively promote the ignition of aluminum powder, which can make the aluminum powder be ignited at the temperature far below the melting point of aluminum. Meanwhile, the carbides formed by the decomposition of tannic acid are beneficial to the cracking of the alumina on the surface of the aluminum powder, which can promote the internal aluminum to participate in the reaction and improve the reaction efficiency of aluminum. The TA-Fe layer can inhibit the agglomeration of molten aluminum during the combustion of aluminum and can effectively improve the corrosion resistance of aluminum powder. The iron ions in the TA-Fe interface layer can successfullycatalyze the thermal decomposition process of ammonium perchlorate (AP). In addition, Al@TA-Fe can effectively increase the burning rate of the propellant compared with pure aluminum powder.

In situ synthesis of hydrophobic coatings: an effective strategy to reduce hygroscopicity and catalyze decomposition of ammonium perchlorate

An in situ reaction of stearic acid with copper acetate or cobalt acetate was adopted to prepare hydrophobic coatings, which effectively reduced the hygroscopicity and accelerated the thermal decomposition process of ammonium perchlorate.

Facile synthesis of flower-like ZnO@Fe2O3 hierarchical nanostructures with enhanced catalytic activity on the thermal decomposition of ammonium perchlorate

This paper reports a facile two-step hydrothermal method for the fabrication of f-ZnO@Fe2O3 nanostructures. Various characterization results show that the hierarchical nanocomposites are formed by the loading of well-crystallized α-Fe2O3 nanoparticles onto the flower-like ZnO. The nanostructures exhibit large specific surface area and narrow mesoporous size distribution. Morphological measurements indicate that Fe2O3 nanoparticles are densely and uniformly attached onto the entire surface of the f-ZnO. The catalytic performance of the f-ZnO@Fe2O3 on the thermal decomposition of AP is measured by TG and DTA methods. The results demonstrate that the f-ZnO@Fe2O3 nanostructures can lower the decomposition temperature and accelerate the decomposition process of ammonium perchlorate, which may be presumably ascribed to the synergistic effect between f-ZnO and α-Fe2O3 nanoparticles.

In-situ and self-distributed: A new understanding on catalyzed thermal decomposition process of ammonium perchlorate over Nd2O3

Catalyzed thermal decomposition process of ammonium perchlorate (AP) over neodymium oxide (Nd2O3) was investigated. Catalytic performances of nanometer-sized Nd2O3 and micrometer-sized Nd2O3 were evaluated by differential scanning calorimetry (DSC). In contrast to universal concepts, catalysts in different sizes have nearly similar catalytic activities. Based on structural and morphological variation of the catalysts during the reaction, combined with mass spectrum analyses and studies of unmixed style, a new understanding of this catalytic process was proposed. We believed that the newly formed chloride neodymium oxide (NdOCl) was the real catalytic species in the overall thermal decomposition of AP over Nd2O3. Meanwhile, it was the “self-distributed” procedure which occurred within the reaction that also worked for the improvement of overall catalytic activities. This work is of great value in understanding the roles of micrometer-sized catalysts used in heterogeneous reactions, especially the solid–solid reactions which could generate a large quantity of gaseous species.

Preparation of Hydrotalcites Derived Ni/Co/Cu/Fe Nanocomposite Oxides and their Catalytic Activities for Thermal Decomposition of Ammonium Perchlorate

Ni/Co/Cu/Fe nano-composite oxides (Ni/Co/Cu/Fe–NCOs) were prepared by calcination of Ni/Co/Cu/Fe hydrotalcites (Ni/Co/Cu/Fe–HTs) precursors. Ni/Co/Cu/Fe–NCOs were used as new catalysts on improving thermal decomposition of ammonium perchlorate (AP). Their catalytic activities were investigated using DTA and TG–MS. The results revealed that Ni/Co/Cu/Fe–NCOs exhibited NiO and spinel phase with high specific surface areas of 90–120 m2 g–1. They have homogenous particles with average crystallite size in the range of 50–60 nm. The thermal decomposition process of AP can be accelerated by the addition of Ni/Co/Cu/Fe–NCOs. Ni/Co/Cu/Fe–NCOs achieved the purpose of improving thermal decomposition of AP based on the presence of superoxide ion (O2–) on the surface of Ni/Co/Cu/Fe–NCOs.

Preparation and characterization of Mg nanoparticles

In this paper, Mg nanoparticles were prepared in tetrahydrofuran via lithium reduction of the corresponding Mg salt. X-ray diffraction and scanning electron microscope investigations confirm the formation of hexagonal phase Mg particles with an average size of 300 nm. X-ray photoelectron spectrometer analysis indicates that the as-prepared Mg nanoparticles are covered with a protecting layer consisting of residue solvents, naphthalene and Mg(OH) 2, which slows down further oxidation under ambient conditions. Thermal analysis shows that the rapid oxidation and nitridation processes of the particles take place at around 500 °C and 553 °C, respectively. Furthermore, the addition of a small amount of magnesium nanoparticles remarkably catalyzes the decomposition process of ammonium perchlorate by lowering the decomposition temperature and enhancing its heat output.

Inhibition Reaction of SrCO3 on the burning rate of ammonium perchlorate propellants

AbstractThe buring rate of ammonium perchlorate (AP) composite propellants is decreased significantly by the addition of SrCO3 without increasing the pressure exponent of burning rate. Results of microthermocouple measurements indicate that the burning surface temperature is increased from 700 K to 970 K by the addition of SrCO3, although the heat release rate in the gas phase is remained unchanged. DTA (differential thermal analysis) and TG (thermogravimetry) experiments were also carried out in order to determine the role of SrCO3 in the decomposition process of AP. The AP decomposition temperature is increased from 590 K to 620 K by the addition of SrCO3. The results of analysis show that the reduction of the burning rate is caused by the increased AP decomposition temperature.