Search

2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is one of the high-energy oxidants, but has limited application due to its high sensitivity. In this work, polyvinylidene fluoride (PVDF) was used as a co-oxidizer, which is expected to increase the safety of CL-20. One kind of novel graphene-based carbohydrazide complex (GCCo and GCNi) was employed to modify the properties of dual-oxidant CL-20@PVDF composites by the spray drying method and compared with traditional nanocarbon materials (CNTs and GO). The properties of these composites were investigated using the TGA/DSC technique and impact test. The results show that GCCo and GCNi could increase the activation energy (Ea) of CL-20@PVDF composites, and change the physical model of CL-20@PVDF, which followed the random chain scission model and then the first-order reaction model. In addition, these nanocarbon materials could reduce the impact sensitivity of CL-20@PVDF by their unique structure. Besides that, a dual-oxidant CL-20@PVDF system was used to improve the combustion property of Boron. GCCo and GCNi with the synergetic effect could increase the flame temperature and control the burn rate of CL-20@PVDF@B compared with CNTs and GO. The energetic nanocarbon catalyst-modified oxidant provides a facile method for stabilizing high-energy but sensitive materials to broaden their application. [ABSTRACT FROM AUTHOR]

Graphical abstract The Diaminotriazole group has great effect on the physical models and activation energies of the initial decomposition of tetrazine derivatives. Highlights • The heat flow behaviour of three insensitive and thermostable s -tetrazine derivatives was evaluated. • The mass loss properties of these compounds were compared with DSC results. • Their decomposition kinetic parameters and physical models were determined. • The gaseous products were analyzed with proposed initial thermolysis mechanisms. Abstract The thermal behaviour, decomposition kinetics and mechanisms of three diaminotriazole-substituted tetrazine compounds have been investigated using simultaneous DSC-TG and TG/MS techniques. It has been found that TBDM-2NB is much more stable than TBDM-NB and TBDM, where the latter decomposes in two steps with different kinetic parameters. The TBDM decomposes with peak temperature of 379.0 °C, while it is 355.6 °C and 386.5 °C for TBDM-NB and TBDM-2NB, respectively. The activation energy of the first step of TBDM is much higher (176.2 kJ mol−1) than the second step (102.3 kJ mol−1). The decomposition of TBDM-NB follows 2-d diffusion model, while it is a first order reaction model for TBDM and nucleation growth model for TBDM-2NB. The rearrangement of s-tetrazine ring is typical for thermal decomposition of the title compounds, which may undergo a homo-scission to produce N 2 and followed by production of NH 3. [ABSTRACT FROM AUTHOR]

Mixtures of 1,3,5-trinitroso-1,3,5-triazinane (TMTA) with 1,3,5-trinitro-1,3,5-triazinane (RDX), cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole (BCHMX) and ɛ-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), respectively, have been investigated by DSC and TGA techniques. It has been found that there are two endothermic peaks at about 96 °C and 107 °C, due to polymorphic transition and melting of TMTA, whereas only small endothermic peaks were observed in the temperature region of 92.8–95.0 °C for mixtures of RDX-TMTA, BCHMX-TMTA and CL-20-TMTA. These differences in exothermic temperatures of the pristine TMTA versus its mixtures could be a result of co-crystals formation. Moreover, only one complex step for decomposition of TMTA and RDX-TMTA was observed, while at least two steps were found for BCHMX-TMTA and CL-20-TMTA mixtures. TGA measurements showed that a mass loss of TMTA begins at 89.3 °C and has a peak temperature of 185.9 °C. In contrast, the mass loss of RDX-TMTA mixture begins at 142.9 °C and has a peak temperature of 227.6 °C, evidently showing a behavior of a single compound. On the other hand, the activation parameters for the first step decomposition of the BCHMX-TMTA (2.355 J g −1 ) and CL-20-TMTA mixtures were found to be very close to that of TMTA (1.320 J g −1 ), strongly indicating that most probably TMTA undergoes decomposes during the first decomposition steps of these mixtures. [ABSTRACT FROM AUTHOR]

Highlights: [•] The thermal behavior of Fluorel bonded explosives (PBXs) containing cyclic nitramines have been investigated. [•] Their decomposition kinetics parameters have been calculated by modified Kissinger–Akahira–Sunose (KAS) method. [•] It has been found that Fluorel matrix has a significant effect on the activation energy distribution of cyclic nitramines. [•] The Fluoropolymer is chemical incompatible cyclic nitramines with crowded molecule such as BCHMX. [Copyright &y& Elsevier]

Highlights: [•] The effects of Viton A binder on the thermal behavior of cyclic nitramines have been investigated by using non-isothermal techniques. [•] The decomposition kinetics parameters have been calculated by modified Kissinger-Akahira-Sunose method. [•] As a thermostable polymer, Viton A could inhibit the initial autocatalysis effect of cyclic nitramines. [•] It would improve the thermal stability of corresponding PBXs containing RDX, β-HMX and ε-CL-20. [Copyright &y& Elsevier]

• Thermal reactivity of core–shell Al@AP and Al@AP/CuO composites were characterized. • The decomposition kinetics and gaseous products of composites were fully identified. • The Al@AP and Al@AP/CuO composites demonstrated better combustion performance. • Mutual interactions of Al@AP embedded with CuO under high temperature were clarified. Conventional solid propellants suffer from undesirable combustion performance due to the poor mass and heat transfer between metal fuels and oxidizers, as well as a lack of catalytic active sites between the catalyst and catalyzed objects. Embedding metal fuels and catalysts within the oxidizer has shown promise in improving the overall combustion performance of HTPB/AP/Al and HTPB/AP/RDX/Al composite solid propellants. However, the underlying mechanisms responsible for this enhancement remain to be further understood. In this study, we investigated the reactivities of core–shell Al@AP and Al@AP/CuO composites using thermal analysis and combustion diagnostic techniques. The results demonstrated that the decomposition of AP was promoted, as evidenced by a lower peak temperature (415.2–334.7 ℃), higher total heat release (116.4–720.8 J·g−1), a transition in the decomposition physical model from the random nucleation and 2D/3D growth of nuclei model to the auto-catalytic model, and increased generation of NO 2. Furthermore, the Al@AP/CuO propellant pellet exhibited a more stable flame without agglomeration, and the condensed combustion products (CCPs) contained a lower amount of unreacted Al compared to that of conventional mixtures. These findings highlighted the potential of core–shell Al@AP and Al@AP/CuO composites as replacements for discrete ingredients of solid propellants, thereby offering improved performance for next-generation propulsion systems. [ABSTRACT FROM AUTHOR]

The zero-order reaction rates (specific rate constants) of isothermal decomposition at 120 °C of plastic bonded explosives (PBXs) in the first six hours of decomposition were measured by means of the Czech vacuum stability test, STABIL. The PBXs were filled by RDX (1,3,5-trinitro-1,3,5-triazinane), β−HMX (β−1,3,5,7-tetranitro-1,3,5,7-tetrazocane), BCHMX and ϵ-CL20 (ϵ-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, ϵ-HNIW) and, in one case, on a mixture of BCHMX and 3-nitro-1,2,4-triazol-5-one (NTO), in a 1:1 wt. ratio. These nitramines were bonded by 9% by wt. of softened polyisobutylene matrix, 13% by wt. of softened polystyrene-butadiene matrix, 18% by wt. of crosslinked hydroxyl-terminated polybutadiene, 12% by wt. of polydimethylsiloxane and by 40% of TNT. The relationships of specific rate constants with experimental detonation velocities, impact and friction sensitivities of these PBXs are shown and discussed. It is postulated that this approach provides results which are applicable to studies of initiation reactivity of energetic materials and which are fully comparable with those of other methods of investigation in this area. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) was investigated in this paper as a promising catalyst for the effective thermal decomposition of tetraamminecopper (II) nitrate coordination complexes. CuC has been synthesized by doping GO nanoparticles in a one-step method and it demonstrates a uniform deposition of the produced nanocomposites onto the surface of the complex. The kinetics of decomposition and underlying mechanisms of GO on CuC have been studied using a Differential Scanning Calorimetry (DSC) technique and Thermal Gravimetric Analysis (TGA) coupled Fourier-Transform Infrared Spectroscopy (FTIR) technique and relevant theories. Under the effect of GO, the release of heat from the decomposition process is significantly increased from 97.1 J·g-1 to 69.2 J·g-1. Under the effect of GO, the activation energy of the CuC decreased from 94.3 to 82.2 ± 0.5 kJ·mol−1 (for endothermic reaction). The significance of this discovery is due to the reactive sites and great thermal conductivity of the GO. By FTIR analysis, GO affected by the formation of NH 3 and N 2 O; and the decomposition of CuC complex in cooperation with the GO may follow a random scission model (A2) since it highly depends on the edge defects of GO as well as coordination center reactive sites (scission sites). In addition, the combustion behavior of CuC and CuC–GO in the physical mixture with B/KNO 3 has been investigated. The results show that the pressure exponent " n " samples (CuC: n = 0.621 vs. CuC–GO: n = 0.703) can be stable and investigated composites are available for successful application as energetic materials. [ABSTRACT FROM AUTHOR]

• Core-shell structured AP@Al/TMs reactive composites have been prepared. • Al/Ni and Al/Co improved the heat release of thermal decomposition of AP by 84.8% and 42.1%, respectively. • The physical models for AP thermal decomposition reaction under the effect of Al/TMs have been proposed. A series of AP reactive composites modified by Al/TMs bi-metal compounds including Al/Ti, Al/Ni and Al/Co have been successfully prepared by acoustic resonance mixing. Various analysis techniques have been utilized and results indicate that the Al/Co exhibits the strongest thermal interaction effect on the thermal decomposition of ammonium perchlorate (AP) by merging reaction steps with enhanced thermal reactivity. In comparison to the pure AP, the peak temperatures of high temperature decomposition (HTD) of AP in the presence of Al/Ti, Al/Ni and Al/Co are significantly decreased by 60.3 °C, 76.9 °C and 100.2 °C, respectively. Moreover, the apparent activation energies obtained for AP@Al/Ti, AP@Al/Ni and AP@Al/Co composites are 96.5 kJ·mol−1, 103.5 kJ·mol−1 and 53.6 kJ·mol−1, respectively. The thermolysis physical models of AP in composites of AP@Al/Ti, AP@Al/Ni and AP@Al/Co appear to follow three-dimensional random nucleation and nucleus growth (A3), whereas the A3, chain scission and phase boundary-controlled reaction are found to be the most appropriate models to represent the three-step thermal decomposition of pure AP. Owing to the high thermal interaction activity, as great bi-metal fuels, Al/TMs can also be considered as outstanding additives for AP thermal decomposition. [ABSTRACT FROM AUTHOR]

Preparation of highly reactive core-shell Al/Co@AP composite and their physical models for the thermal decomposition of AP and the intermetallic reactions under the mutual interaction. [Display omitted] • Core-shell structured Al/Co@AP composite has been prepared. • Al/Co improved the heat release of the thermal decomposition of AP by 52.6%. • AP enhanced the heat release of the intermetallic reaction between Al and Co by 67.7%. • The physical models for the AP thermal decomposition reaction and Al/Co intermetallic reaction have been proposed. In this paper, a group of novel intermetallic metastable composites Al/Co@AP has been designed, and three methods including ultrasonic dispersion, mechanical grinding and spray-drying have been attempted for their preparation. The latter one has demonstrated to be the most appropriate means, by which the core–shell structured Al/Co@AP with desired properties could be successfully obtained. The thermal reactivity of Al/Co/AP composites prepared differently has been investigated and compared by TG/DSC technique. It has been shown that the heat release rate of AP in DSC curve was largely increased in the presence of Al/Co when spray-drying technique was used, which may be attributed to the increased nuclear site by the intimate contact. The initial reaction temperature of AP in Al/Co@AP was decreased by 7.8 °C and the heat releases by the thermal decomposition of AP and the intermetallic reaction between Al and Co were enhanced by 52.6 % and 67.7% in comparison with that of pure AP and Al/Co. The types of major gaseous products of Al/Co@AP are almost identical to that of pure AP, which include HCl, H 2 O, N 2 O and NO 2. However, the concentrations of NO 2 and N 2 O in gaseous products for Al/Co@AP are lower than that observed for pure AP, which may be due to the partial consumption of N element by the reaction of Al with acidic substance (HNO 3) decomposed from AP. In addition, the AP in Al/Co@AP composite decomposes in one-step with the apparent activation energy (E a) of 98.8 kJ·cm−3. The decomposition process of the AP in Al/Co@AP composite follows two-dimensional nucleation and growth model(A2), whereas the pure AP follows different physical models, which are close to three-dimensional nucleation and growth, chain scission and phase boundary-controlled reaction (contracting area) models. The intermetallic reaction between Al and Co in Al/Co@AP is merged into one-step following the A2 physical model. [ABSTRACT FROM AUTHOR]

Owing to the novel insensitive high-energy-density material 2,4,6-triamino-5-nitropyrimidine-1,3-dioxide (ICM-102) has lower sensitivity and higher energy(see in Table S1, Supporting Information), it has great advantages in the application of low-vulnerability propellants. In this paper, the evaluation of ICM-102-containing composite propellants has been carried out, where the decomposition and combustion performances of these propellants have been comprehensively investigated. It has been shown that the main exothermic decomposition peak temperature can be increased from 235 ºC to 350 ºC, when 6 to 10 wt% of ICM-102 was used to replace RDX, but heat release rate was largely increased. Moreover, the burning rate of ICM-102 containing propellants at 3 MPa is in the range of 6.97–7.75 mm• s − 1, depending on its content. The pressure exponent (0.5–3 MPa) is between 0.34–0.44. Compared with the typical propellants with RDX, the burn rate and the flame temperature of ICM-102- containing propellants are higher. In addition, the particle size distributions of condensed combustion products of ICM-102 propellants are narrower and smaller than that of RDX-based one. It also shows that extra products such as aluminum carbide (Al20C) and aluminum oxide nitride (Al5O6N) were produced once ICM-102 was used. [ABSTRACT FROM AUTHOR]

• Recent advances on preparation/regeneration methods and processing techniques of high energy fuel (AlH 3) are summarized and discussed. • The detailed thermal decomposition properties and mechanisms under different conditions are elucidated. • The ignition and combustion properties and modifications methods are summarized and discussed for the first time. • Various challenges and future perspectives on the development of AlH 3 as high energy fuel have been proposed. As a novel energetic material, aluminum hydride (AlH 3) has attracted much attention because of its high hydrogen storage capacity and rapid dehydrogenation at low temperatures, which can be used as a promising energetic additive in solid propellants or in some other areas such as catalysts, fuel cell, and reducing agents. In particular, AlH 3 as a component of solid propellant may largely promote the specific impulse of rocket engines and effectively reducing the erosion of engine nozzles. This review focuses on the research results in synthesis/regeneration, thermal decomposition, oxidation, ignition and combustion characteristics, and stabilization of AlH 3 over the past decades. In particular, the stabilizing of AlH 3 is essential for the its application in solid propellants, where the most widely used strategies have been introduced and compared, based on which some suggestions regarding possible future research directions are proposed. [ABSTRACT FROM AUTHOR]

• Novel PDA/GO coating methodology using PDA as an interfacial layer can further stabilize thermostable EMs. • The thermal reactivity properties and gaseous products of coated composites are clarified. • The kinetics models of multi-stage decomposition reactions are obtained. The high performance energetic materials (EMs) with reduced sensitivity and improved thermostability are essential for propellant and explosive applications. In this paper, two thermostable derivatives of dibenzotetraazapentene Tetranitro-Benzopyridotetraazapentalene (NBTTP) and Tetranitro-Dipyridotetraazapentalene (NPTTP) are further stabilized by Polydopamine (PDA) and Graphene Oxide (GO) coating, resulting in highly thermostable composites. The thermal behavior and decomposition mechanisms of these composites have been investigated by TG-DSC/FTIR technique. It has been shown that the PDA/GO coating layer is effective to stabilize NBTTP and NPTTP crystals by largely increasing their decomposition activation energy (E a). As a typical product, the NBTTP@PDA/GO-1–1 decomposes in two steps, with the E a 38.0% and 59.0% higher than that of pristine NBTTP, respectively. In comparison, the E a for rate-limiting decomposition step of NPTTP@PDA/GO-1–2 is 92.6% higher than that of NPTTP. After coating PDA/GO, the decomposition heat does not change much, which is about 2259 to 2458 J g−1. The last decomposition step for these composites follows 2D nucleation and nucleus growth model, whereas it is 3D nucleation and growth model for the pristine crystals, indicating a much lower decomposition reaction rate. The major gaseous products of NBTTP and NPTTP are CO 2 , C 2 H 2 , N 2 O, C N, CO, NO and H 2 O. Volatile hydrocarbon products appear in modified NBTTP composites, which are responsible for the slow reaction rates. [ABSTRACT FROM AUTHOR]

• A variety of novel hybrid qy-HMX crystals with different structure have been prepared and evaluated. • The kinetics models governing the rate-limiting thermolysis reactions are obtained. • The structure and thermal reactivity properties of qy-HMX and corresponding mechanism are clarified. In this paper, the 2D (two-dimensional) high nitrogen triaminoguanidine-glyoxal polymer (TAGP) has been used to dope HMX crystals. Various constraint TAGP-doped HMX crystals (qy-HMX) with higher density and better stability have been obtained due to strong constraint interactions between dopant and HMX molecules. The structure and thermal reactivity properties of qy-HMX are unexpectedly largely affected by a slight change in the way of co-crystallization/precipitation under the same precursor conditions. In particular, the density of qy-HMX could be largely changed in the range of 0.94 g cm−3 to 2.12 g cm−3 due to varied doping state, depending on the crystallization conditions. These qy-HMX crystals are more thermally stable than HMX, showing either no polymorphic transition or increased transition temperature. As a typical example, the polymorphic transition of qy-HMX-211 with doping amount of 21.1 wt% was excluded due to formation of a completely new more stable phase of HMX. The qy-HMX-341 has the highest heat release (1869 J g−1), even higher than that of HMX. The average E a (activation energy) for the polymorphic transition of qy-HMX-341 is about 334.1 kJ mol−1, following a random chain scission model (L2), whereas it is 222 kJ mol−1 for HMX. The E a for thermal decomposition of qy-HMX-341 is 215.7 kJ mol−1, which is 39.8 kJ mol−1 lower than that of HMX. Therefore, the qy-HMX crystal has high potential to be used as a promising high explosive to replace HMX for various applications in the future. [ABSTRACT FROM AUTHOR]