Tuning the thermal,mechanical, and combustion properties of NC-TEGDN-RDX propellants via incorporation of graphene nanoplates

ABSTRACT

Graphene nanoplates (GNPs) were incorporated into a solid composite propellant (NC-TEGDN-RDX) to tune the thermal, mechanical, and combustion properties of the material. Physical, thermal, and combustion properties of NC-TEGDN-RDX with <2 wt% addition of GNPs were characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), tensile/compressive/impact strength testing, and constant volume combustion experiments. Microstructure of the composite propellants examined using SEM demonstrated uniform dispersion of the GNPs at low-weight percent additives (<1 wt%), but began to show large agglomerations of the additives at higher additive content. Decomposition enthalpy of the propellant with 1 wt% GNPs increased by ~130 J/g compared to neat propellants. Moreover, the maximum burning rate was observed for samples containing 1 wt% GNPs, with values of 19 cm/s at 20°C and 17 cm/s at ?40°C. Dynamic vivacity of the propellant achieved a maximum upon addition of 1 wt% GNPs. The pressure exponent of the propellant decreased with the addition of GNPs, as well. The mechanical properties including tensile, compressive, and impact strength were improved at 20°C and ?40°C. These results demonstrate that the addition of GNPs may offer new methods by which to tune and improve thermal decomposition, thermal conductivity, combustion performance, and mechanical properties of the NC-TEGDN-RDX propellants.     

Ammonium perchlorate decomposition: Neat and solution1

Abstract

The thermal decomposition of ammonium perchlorate (AP) was examined over a broad temperature range (215°C to 385°C) in solution and condensed phase. Over the entire temperature range, the decomposition, as monitored by loss of ammonium ion, appeared first-order out to 70% decomposition. Up to about 350°C the decomposition of AP in methanol (5wt% AP) proceeded at a rate similar to neat AP, but the AP in aqueous solution (20wt%) decomposed considerably slower than the neat material. Activation energies and frequency factors were determined for each experimental condition. In addition, decomposition products, both gaseous and condensed phase, were identified and quantified. For neat AP decomposition, the following reaction stoichiometries were determined.

At low temperatures, decomposition of ammonium perchlorate in methanol proceeded at a similar rate to that of neat AP. In contrast to decomposition of neat AP, the only nitrogen-containing decomposition product was nitrogen gas, while chlorine appeared only as chloride. The presence of CO and CO₂ as decomposition gases and chromatographic analysis of the solvent indicated interaction between methanol and AP. The decomposition of AP in water was slowed, but product distribution was not significantly different than that of neat AP.     

Nanocatalysts: Effect of Active-phase and Promoter on Catalytic Properties and Performance in the Hydrodesulfurization Reaction

The influence of various amounts of phosphorus addition on performance of NiMoP/Al₂O₃ and CoMoP/Al₂O₃ nanocatalysts was examined in hydrodesulfurization of thiophene. The nanocatalysts were synthesized via sonochemical technique. The prepared samples were characterized by XRD, FESEM, BET, and FTIR analysis. The catalytic activity in hydrodesulfurization reaction was investigated in a batch stirred slurry reactor at 160°C and atmospheric pressure. The characterizations confirmed highly dispersion of active phase and formation of amorphous AlPO₄ species on the support surface. The results obtained from thiophene hydrodesulfurization showed the nanocatalysts contained 1 wt% of phosphorus had the highest activity. The CoMoP/Al₂O₃ and NiMoP/Al₂O₃ nanocatalysts with optimum phosphorus loading nearly gave 100% conversion of thiophene, so that the sulfur compound concentration in final solution was less than 50 ppm.     

Dibenzothiophene Hydrodesulfurization Activity of MoS2 Supported in Sol–Gel ZrO2–TiO2 Mixed Oxides

Abstract

In this work, we report the effect of support composition on the properties of MoS₂ impregnated in sol–gel ZrO₂–TiO₂ mixed oxides as dibenzothiophene hydrodesulfurization catalyst. The supports calcined at 500°C were characterized by N₂ physisorption and X-ray diffraction (electronic radial distribution function). The oxidic impregnated materials (2.8 Mo atoms/nm²) were sulfided at 400°C under a H₂S/H₂ stream. The sample impregnated on the equimolar support showed the highest activity per mass of catalysts whereas the one with TiO₂ carrier was superior in a per mass of Mo basis. Marked differences in products selectivity were observed by TiO₂ addition in the supports. The hydrodesulfurization route to partially hydrogenated compounds was favored over the mixed oxides-supported catalysts meanwhile the direct desulfurization (to biphenyl) was promoted on the ZrO₂-supported solid. It is suggested that among other properties the dispersion and morphology of the MoS₂ phase could influence that behavior.     

Nanoparticles of Transition Metals as Accelerants in the Thermal Decomposition of Ammonium Perchlorate,Part 62

Four transition metal nanoparticles (TMNs) of 3d series (Cu, Co, Ni, and Fe) were prepared by hydrazine reduction of metal chloride in ethylene glycol at 60°C and characterized by X-ray diffraction (XRD). The XRD pattern showed average particle sizes for Cu, Ni, Co, and Fe of 16.7, 40.5, 27.4, and 35.0 nm, respectively. The activity of these TMN accelerants on the thermal decomposition of ammonium perchlorate (AP) was investigated using thermogravimetry (TG), differential scanning calorimetry (DSC), and ignition delay studies. Isothermal TG data were used to evaluate the kinetic parameters by model fitting as well as an isoconversional methods. The activation energy for thermal decomposition of AP was found to be 66.8, 68.7, 78.5, and 85.4 kJmol^?1, respectively, for Co, Cu, Ni, and Fe, when they were mixed with AP. Hence, the order of activity was found to be Co > Cu > Ni > Fe. The accelerant effect of nanoparticles of TMNs was found to be better than their respective nano-oxides.     

Copper (II) complexes of 1-methyl-5-aminotetrazole with different energetic anions: syntheses,crystal structures and properties

ABSTRRACT

Three energetic copper (II) complexes, [Cu(1-MAT)₂(HDNBA)₂](DNBA)₂ (1), [Cu(1-MAT)₂](PA)₂ (2) and [Cu(1-MAT)₄(H₂O)₂](ClO₄)₂ (3) [1-MAT: 1-methyl-5-aminotetrazole; HDNBA: 3,5-dinitrobenzoic acid; PA: picric acid] were synthesized and characterized. The X-ray single-crystal diffraction results illustrate that the structure of the coordination compounds 1, 2 and 3 belong to the P21/c, P2₁2₁2 and C2/m space group, respectively. The central copper ion forms a hexacoordinated octahedral structure with N and O atoms. All of them possess good thermal stability, with the thermal decomposition temperatures of 254°C (1), 272°C (2) and 322°C (3), respectively, due to their plenty of coordination bonds, intramolecular and intermolecular H-bonds. According to the results of impact sensitivity and friction sensitivity, these compounds are insensitive to impact (>40 J) and friction (>360 N), except the impact sensitivity of 3 is 2.7 J. The measured constant volume combustion energies of 1, 2 and 3 are 13480, 3537 and 7442 kJ mol^?1, respectively.     

Studies on Triple Base Gun Propellant Based on Two Energetic Azido Esters

Triple base propellant is the workhorse propellant because it possesses several advantages like reduced flash, flame temperature, and erosion of the barrel as compared to double and single base propellant. Hence, efforts are going on worldwide to increase its performance by increasing its energy using energetic plasticizers and binders. In the present article, nonenergetic plasticizer dibutyl phthalate (DBP) is replaced by two energetic azido ester plasticizers, tris(azido acetoxy methyl) propane (TAAMP) and bis(azido acetoxy) bis(azido methyl) propane (BABAMP), in triple base composition and their different properties are studied.

Experimental closed vessel (CV) results (loading density 0.2 g/cm³) clearly indicate that the triple base composition with 2% DBP has force constant 1018 J/g, which is increased to 1026 and 1030 J/g on replacement of DBP by 1 and 2% TAAMP, respectively. Mechanical properties of propellant compositions containing 1 and 2% TAAMP (compression strength 279 and 291 kg_f/cm², percentage compression 11.2 and 10.5, respectively) are also better than those of composition containing DBP (compression strength 275 kg_f/cm² and 10.3% compression). Similarly, 1 and 2% replacement of DBP by BABAMP shows further rise in energy (1032 J/g, 1038 J/g respectively) than that of compositions containing 1 and 2% TAAMP. These two compositions also exhibit better mechanical properties (compression strength 311.2 and 312.3 kg_f/cm², % compression 11.0 and 10.5, respectively) than compositions containing 1 and 2% TAAMP. The differential thermal analysis (DTA) results brought out the fact that the compositions containing energetic plasticizers revealed maximum decomposition temperature in the range of 172–174°C which is close to DBP plasticized triple base gun propellants (174°C). The energetic plasticized propellant compositions of both (TAAMP and BABAMP) showed sensitivity data in the range of (H₅₀ 19 to 22 cm, F of I 25 to 29 and friction insensitivity 19.2 kg) acceptable limit for gun propellant.     

2,4,6-Tris(2,2,2-trinitroethylamino)-1,3,5-triazine: Synthesis,Characterization, and Energetic Properties

A simple and straightforward route for the synthesis of 2,4,6-tris(2,2,2-trinitroethylamino)-1,3,5-triazine (TTET) has been developed. The compound was fully characterized by multinuclear (¹H, ¹³C) magnetic resonance and infrared (IR) spectroscopy, elemental analysis, electron ionization–mass spectrometry, and differential scanning calorimetry (DSC). TTET was found to have good physical properties, such as good thermal stability (T_d = 186°C), reasonable impact sensitivity (21.5 J), and high density (1.88 g · cm^?3). Additionally, the detonation properties of TTET obtained with the empirical Kamlet-Jacobs equations identify it as a competitively energetic compound, which in some cases is superior to 1,3,5-Trinitroperhydro-1,3,5-triazine.     

Hydrogen production by catalytic methane decomposition over Ni,Co, and Ni-Co/Al2O3 catalyst

Hydrogen is a chief source of energy. Catalytic decomposition produces hydrogen and carbon. In this work, x%M/Al₂O₃ (where M is Ni, Co and combined Ni-Co, and x is 10%, 15%, and 30%) has been successfully employed as a catalyst. The effect of activation temperature and active metal type and loading on catalyst perfomance was investigated. The catalysts were characterized with BET, XRD, TPO, TPR, TEM, XPS, and Raman. The results displayed that the 30%Co/Al₂O₃ catalyst activated at 500°C provided the greatest catalytic performance toward methane conversion. 30%Co/Al₂O₃ catalyst activated at 500°C formed amorphous carbon.     

Silicone bridged iron metallocene butadiene composite solid propellant binder: aspects of thermal decomposition kinetics,pyrolysis and propellant burning rate

Propellant binders are essential components of composite solid propellants (CSP’s) used in launch vehicles and missiles. Binders act as a fuel and contribute directly to the combustion in conjunction with oxidizer particles and metallic fuel apart from imparting structural integrity to the solid propellant grain .The performance of CSP’s are directly related to the burn rate of the propellant. The burn rates of the ammonium perchlorate (AP) propellants are generally moderated using various types of transition metal oxide (TMO) catalysts. However, TMO’s are associated with inherently large dispersions in propellant burn rates and compromise on energetics. One of the most suitable methods for achieving lower dispersion in burn rate is using binders wherein a burn rate catalyst is grafted to the polymer matrix. In the present paper, the thermal decomposition of ferrocene bound hydroxyl terminated polybutadiene (FC-Si-HTPB) grafted to butadiene backbone via hydrosilylation was investigated The thermal degradation mechanism, stability and its effectiveness as burn rate catalyst are the most important aspects for use in CSP’s. The mechanism of decomposition of the neat resin and in combination with AP has been elucidated using pyrolysis gas chromatography–mass spectrometric technique (GC-MS). FC-Si-HTPB exhibits single stage decomposition in the temperature range of 263–491°C. The decomposition of FC-Si-HTPB with AP oxidizer follows a two stage mechanism in the 195–490°C.The char residue was characterized using FTIR, Raman spectroscopy and FE-SEM analysis, which enables to vindicate the mechanism of reaction. The activation energy for the decomposition of HTPB is 283.6 kJ/mol, FC-Si-HTPB is 251.5 kJ/mol and for Fc-Si-HTPB-AP system is 67.1 kJ/mol. The major pyrolysis products of neat FC-Si-HTPB are ferrocenyl derivatives, silylated ferrocenyl derivatives and precursors emanating from polybutadiene backbone. The propellants based on the new binder exhibited an increase in burn rate with iron content and higher fine content. A comparison of propellant burn rate with conventional micron sized ferric oxide exhibited an improvement of 34%.Based on the thermal analysis studies, the thermal endurance of the system was computed to be FC-HTPB> HTPB> FC-HTPB-AP.     

Novel high-energy ionic molecules deriving from new monovalent and divalent 4-oxyl-3,5-dinitropyrazolate moieties

ABSTRACT

In recent years, the exploration of a practical strategy for novel energetic molecules with high energy and low sensitivity is very desirable but highly challenging. Novel ionic energetic molecules have attracted much attention in this area due to their prominent advantages including low sensitivities, high thermal stability, and excellent energy performances. Herein, five different ionic energetic molecules based on new monovalent and divalent 4-oxyl-3,5-dinitropyrazolate moieties with enhanced oxygen balance have been synthesized, characterized and evaluated as potential high-energy materials. Thermal stability, sensitivities and energy output test were measured and studied in detail. The heats of formation and energetic parameters were calculated by using Gaussian 09 suite of programs and EXPLO 5 code. The results suggest that all as-prepared new molecules exhibit good thermal stability with high decomposition temperature (3, 231°C; 5, 160°C; 6, 185°C; 7, 180°C; 8, 213°C), and relative low sensitivity (IS > 20 J, FS = 324 N). Inheriting the significant oxygen content of monovalent and divalent 4-oxyl-3,5-dinitropyrazolate moieties, they also possess good energy properties (v _D = 8238 ~ 9208 m s^?1, P = 26.8 ~ 36.7 GPa, V _o = 481.8 ~ 959.4 L kg^?1), which make them competitive high-energy materials.     

Applying Pebax-1657/ZnO mixed matrix membranes for CO2/CH4 separation

Abstract

Membrane technologies as conservative approaches have absorbed much attention in chemical and petroleum engineering, recently. The current research presents the preparation of effectively mixed matrix membranes (MMMs) using polyether-block-amide (Pebax-1657) as a polymeric matrix and zinc oxide (ZnO) nanoparticles with various contents (0.0, 2.5, 5.0, 7.5, and 10.0?wt%) as a filler. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and field emission scanning microscopy (FESEM) were conducted to characterize the prepared membranes. The membrane performance was evaluated by caring out permeation experiments of the CO₂ and CH₄ at a pressure of 3?bar and temperature of 30?°C. Based on the obtained results, the CO₂ permeability and ideal CO₂/CH₄ selectivity increased about 13 and 21%, respectively at 10.0?wt% loading of ZnO in the polymer matrix.     

Facile preparation of Cr2O3 nanoparticles and their use as an active catalyst on the thermal decomposition of ammonium perchlorate

ABSTRACT

Cr₂O₃ nanoparticles were prepared by repeated wet mechanical milling technique. Three drying methods, oven drying, vacuum drying, and vacuum freeze-drying were comparatively used to dry Cr₂O₃ nanoparticles. These processes can be easily scaled up to 10-kg quantities. It took only 2–3 h to cut bulk size to nanometer by milling. The obtained Cr₂O₃ nanoparticles are semi-spherical and homogeneous with an average size of 30 nm measured by SEM and TEM and show similar diffraction peak positions to bulk one investigated by XRD. The TG/DSC study indicated that, compared with bulk Cr₂O₃, Cr₂O₃ nanoparticles obtained by oven drying and vacuum drying, the catalytic performance of Cr₂O₃ nanoparticles obtained by vacuum freeze-drying is the best in lowering the peak temperature of high temperature decomposition and the activation energy, while increasing the apparent decomposition heat and the reaction rate constant of ammonium perchlorate (AP) due to their good dispersion and large specific surface area. The possible catalytic mechanism of Cr₂O₃ on the thermal decomposition of AP was proposed by TG-MS analysis. These findings showed that wet mechanical milling technique combined with vacuum freeze-drying technology is suitable for efficient preparation of Cr₂O₃ nanoparticles, which could be a promising additive for accelerating the thermal decomposition of AP.     

Massive Preparation of Reduced-Sensitivity Nano CL-20 and Its Characterization

Nano 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) was produced massively by ball milling. One thousand grams of the raw CL-20 were used per batch. The product was characterized using laser granularity measurement, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The results show that the pulverized particles were pseudo-spheres with an average particle size (d₅₀) of 200 nm, and the thermal decomposition peak temperature of the nano CL-20 was 239.61°C lower than that of the micrometer-sized CL-20 at a heating rate of 15°C · min^?1. Furthermore, compared with the raw CL-20, the impact and friction sensitivities of the nano CL-20 were considerably reduced by 116.2 and 22%, respectively, indicating the great improvement in safety of CL-20.     

Kinetics of (TBAF + CO2) semi-clathrate hydrate formation in the presence and absence of SDS

In this communication, the impacts of adding SDS (sodium dodecyl sulfate), TBAF (tetra-n-butylammonium fluoride) and the mixture of SDS + TBAF on the main kinetic parameters of CO₂ hydrate formation (induction time, the quantity and rate of gas uptake, and storage capacity) were investigated. The tests were performed under stirring conditions at T = 5 ℃ and P = 3.8 MPa in a 169 cm³ batch reactor. The results show that adding SDS with a concentration of 400 ppm, TBAF with a concentration of 1–5 wt%, and the mixture of SDS + TBAF, would increase the storage capacity of CO₂ hydrate and the quantity of gas uptake, and decrease the induction time of hydrate formation process. The addition of 5 wt% of TBAF and 400 ppm of SDS would increase the CO₂ hydrate storage capacity by 86.1% and 81.6%, respectively, compared to pure water. Investigation of the impact of SDS, TBAF and their mixture on the rate of gas uptake indicates that the mixture of SDS + TBAF does not have a significant effect on the rate of gas uptake during hydrate formation process.     

The effect of nano-SiO2 and the styrene butadiene styrene polymer on the high-temperature performance of hot mix asphalt

The production of modified asphalt mixtures with appropriate performance in high temperature has always been under the attention of researchers. One of these modifiers is Styrene Butadiene Styrene (SBS) polymer. Since the application of SBS polymer in bitumen and asphalt mixture does not have expected performance of field due to phase separation of bitumen and polymer, oxidation, and aging, the present study tries to not only improve the polymer defects, but also analyzes its high-temperature performance by using nano-SiO₂ and SBS polymer in bitumen modification. According to the study results, adding nano-SiO₂ and SBS polymer with 3 and 4.5 bitumen weight percent, respectively, to bitumen in asphalt mixture leads to an increase of flow number in dynamic creep test at 50°C for 399 times and at 60°C for 1,015 times compared to unmodified asphalt mix. This, in turn, indicates the considerable improvement of asphalt mixture high-temperature performance.     

Fe0/Graphene Nanocomposite as a Catalyst for the Viscosity Reduction of Heavy Crude Oil

Fe⁰/graphene nanocomposites were prepared via a thermal polymerization method and used as a catalyst to reduce the viscosity of heavy crude oil. The nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, N₂ adsorption-desorption isotherms and thermal analysis. Their performance on the aquathermolysis of heavy crude oil was assessed in an autoclave. Under the reaction conditions of 200°C and 24 h, the viscosity of the oil was remarkably reduced when the catalysts were added.     

Preparation of PbCO3–CuO nanoparticles and catalytic performance on NC/NG and NC/NG/NQ propellants

This study demonstrates a direct, high-yield, and inexpensive route for preparation of nearly spherical PbCO₃–CuO nanoparticles (NPs) through mechanical ball milling method. The NPs were characterized by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, EDS, and dynamic light scattering techniques. Catalytic decomposition effects of PbCO₃–CuO NPs and PbCO₃/CuO raw material mixture on nitrocotton (NC)/nitroglycerin (NG) propellant were studied by DSC analysis. Then, the combustion properties of NC/NG and nitroguanidine (NQ)/NC/NG propellants with above catalysts were researched. The results showed that the NPs exhibited good catalytic effect on both propellants. By adding 1.5% NPs in mass, decomposition temperature of NC/NG decreased by 29.35°C, and the heat of decomposition increased by 606 J g^?1. PbCO₃–CuO NPs used as burning catalyst of above propellants can increase the burning rate, decrease the pressure exponent and form good “plateau” effect at 4–12 MPa. And the NPs showed better comprehensive catalytic performance than the PbCO₃/CuO mixture. Thus, PbCO₃–CuO NPs could be a promising addictive in modifying burning behaviors of solid propellants with double base component.     

Desulfurization of FCC Gasoline Over Mordenite Modified with Al2O3

Abstract

Mordenite modified with Al₂O₃ (Al₂O₃/mordenite) was synthesized and used for the desulfurization of FCC gasoline. The influences of operating parameters on the results were studied for the model solution composed of dibenzothiophene (DBT) and isooctane. Al₂O₃/mordenite exhibits higher sulfur capacity than other kinds of chemisorbents. The suitable composition of the chemisorbent is 30 wt% Al₂O₃ to 70 wt% mordenite. The optimal operating parameters are: temperature 160°C; velocity 3 h^?1 (WHSV). Under the stated conditions, desulfurization was carried out for the FCC gasoline with sulfur content of 220.4 μg/g. The chemisorbent can maintain the sulfur content under 50 μg/g for 40 h and has good regeneration ability after desorption using benzene.     

Hydrothermal synthesis of unsupported MoS2 as catalyst for hydrodesulfurization of gas oil

Hydrothermal synthesis with ammonium heptamolybdate and thiourea as precursors was used to obtain an unsupported MoS₂ catalyst. The catalyst was obtained in sulfide state directly at mild reaction conditions (i.e., 180°C during 5 h). After catalyst was obtained, it was characterized through nitrogen physisorption, transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Catalytic evaluation was carried out in a batch reactor at 350°C, 55 bar of hydrogen pressure, 750 rpm, and 3 h of reaction time using straight-run gas oil (SRGO) as feedstock. A commercial CoMo/Al₂O₃ catalyst was used for comparison of activity. The synthesized catalyst was slightly more active toward SRGO hydrodesulfurization than commercial one keeping constant the sulfur removal after two runs.