A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energ...A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.展开更多
Biomass chitosan(CS)was used as a template,graphitic phase carbon nitride(g-C_(3)N_(4))with high nitrogen content and certain catalytic activity was used as a dopant,and nano-transition metal cobalt(Co)was used as a c...Biomass chitosan(CS)was used as a template,graphitic phase carbon nitride(g-C_(3)N_(4))with high nitrogen content and certain catalytic activity was used as a dopant,and nano-transition metal cobalt(Co)was used as a catalytic center point.The carbon aerogel(C(CS)/g-C_(3)N_(4)/Co)with a three-dimensional network-like structure was prepared by assembling the three materials through experimental operations such as freeze-drying and high-temperature carbonization.It was demonstrated by scanning and transmission characterization that the CS in the carbon aerogel could provide more active sites for the cobalt nanoparticles,and the doping of graphite-phase carbon nitride as a template dispersed the cobalt nanoparticles and changed the conductivity of the CS.To investigate the catalytic effect of carbon aerogel on ammonium perchlorate(AP),it was investigated by differential thermal analyzer and TG thermal analysis.This carbon aerogel was very effective in catalyzing AP,and the 10 wt% content of the catalyst reduced the AP pyrolysis peak from 703.9 to 595.5 K.And to further investigate the synergistic effect of the three materials,further carbon aerogels such as C(CS)/Co,g-C_(3)N_(4)/Co were prepared and applied to catalyze AP,and the same ratio reduced the AP pyrolysis peak by 98.1℃ and 97.7℃.This result indicates a synergistic effect of the assembly of the three materials.展开更多
The monodispersed Co nanoparticles were successfully prepared by means of hydrogen plasma method in inert atmosphere. The particle size, specific surface area, crystal structure and morphology of the samples were char...The monodispersed Co nanoparticles were successfully prepared by means of hydrogen plasma method in inert atmosphere. The particle size, specific surface area, crystal structure and morphology of the samples were characterized by transmission electron microscopy (TEM), BET equation, X-ray diffraction (XRD), and the corresponding selected area electron diffraction (SAED). The catalytic effect of Co nanoparticles on the decomposition of ammonium perchlorate (AP) was investigated by differential thermal analyzer (DTA). Compared with the thermal decomposition of pure AP, the addition of Co nanoparticles (2%-10%, by mass) decreases the decomposition temperature of AP by 145.01-155.72℃. Compared with Co3O4 nano-particles and microsized Co particles, the catalytic effect of Co nanoparticles for AP is stronger. Such effect is attributed to the large specific surface area and its interaction of Co with decomposition intermediate gases. The present work provides useful information for the application of Co nanoparficles in the AP-based propellant.展开更多
Ammonium perchlorate(APC)is the most common oxidizer in use for solid rocket propulsion systems.However its initial thermal decomposition is an endothermic process that requires 102.5 J·g^-1.This manner involves ...Ammonium perchlorate(APC)is the most common oxidizer in use for solid rocket propulsion systems.However its initial thermal decomposition is an endothermic process that requires 102.5 J·g^-1.This manner involves high activation energy and could render high burning rate regime.This study reports on the sustainable fabrication of CuO nanoparticles as a novel catalyzing agent for APC oxidizer.Colloidal CuO nanoparticles with consistent product quality were fabricated by using hydrothermal processing.TEM micrographs demonstrated mono-dispersed particles of 15 nm particle size.XRD diffractogram demonstrated highly crystalline material.The synthesized colloidal CuO particles were effectively coated with APC particles via co-precipitation by using fast-crash solvent-antisolvent technique.The impact of copper oxide particles on APC thermal behavior has been investigated using DSC and TGA techniques.APC demonstrated an initial endothermic decomposition stage at 242℃ with subsequent two exothermic decomposition stages at 297,8℃ and 452.8℃ respectively.At 1 wt%,copper oxide offered decrease in initial endothermic decomposition stage by 30%.The main outcome of this study is that the two main exothermic decomposition peaks were merged into one single peak with an increase in total heat release by 53%.These novel features can inherit copper oxide particles unique catalyzing ability for advanced highly energetic systems.展开更多
A new energetic complex, Ni(3,4'-Hbpt)2(Hoba)2(H20)2 (3,4'-Hbpt = 3-(3-pyridyl)- 5-(4'-pyridyl)-l-H-l,2,4-triazole and H2oba = 4,4'-oxybis(benzoic acid)), has been synthesized by hydrothermal reactio...A new energetic complex, Ni(3,4'-Hbpt)2(Hoba)2(H20)2 (3,4'-Hbpt = 3-(3-pyridyl)- 5-(4'-pyridyl)-l-H-l,2,4-triazole and H2oba = 4,4'-oxybis(benzoic acid)), has been synthesized by hydrothermal reaction and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, thermogravimetric analyses and X-ray powder diffraction. Single-crystal X-ray diffraction analysis indicates that the complex belongs to the monoclinic system, space group P2j/c with a = 10.2357(9), b = 24.594(2), c = 10.4225(9)/k, β = 114.0110(10)°, V = 2396.7(4) A3, Dc = 1.460 g/cm3,μ = 0.482 mm-1, Mr = 1053.63, F(000) = 1088, Z = 2, the final R = 0.0358 and wR = 0.0973 with I 〉 2σ(I). Both 3,4'-Hbpt and H2oba ligands adopt monodentate modes linking one Ni(II) ion to form a 0D motif. Furthermore, the 0D motifs are linked into a 3D supramolecular architecture with hydrogen bonds. In addition, the catalytic performance for thermal decomposition of the efficacy of ammonium perchlorate (AP) is explored by differential scanning calorimetry (DSC), which indicates that the complex is a good candidate for a promoter of the thermal decomposition of ammonium perchlorate.展开更多
As a main oxidizer in solid composite propellants,ammonium perchlorate(AP)plays an important role because its thermal decomposition behavior has a direct influence on the characteristic of solid composite propellants....As a main oxidizer in solid composite propellants,ammonium perchlorate(AP)plays an important role because its thermal decomposition behavior has a direct influence on the characteristic of solid composite propellants.To improve the performance of solid composite propellant,it is necessary to take measures to modify the thermal decomposition behavior of AP.In recent years,transition metal oxides and carbon-supported transition metal oxides have drawn considerable attention due to their extraordinary catalytic activity.In this review,we highlight strategies to enhance the thermal decomposition of AP by tuning morphology,varying the types of metal ion,and coupling with carbon analogue.The enhanced catalytic performance can be ascribed to synergistic effect,increased surface area,more exposed active sites,and accelerated electron transportation and so on.The mechanism of AP decomposition mixed with catalyst has also been briefly summarized.Finally,a conclusive outlook and possible research directions are suggested to address challenges such as lacking practical application in actual formulation of solid composite propellant and batch manufacturing.展开更多
A new energetic complex,[Co(3,3?-Hbpt)(Htm)]·H_2O(1,3,3?-Hbpt = 3,5-bis(3-pyridyl)-1H-1,2,4-triazole and H_3tm = trimesic acid),has been synthesized by hydrothermal reactions and characterized by single...A new energetic complex,[Co(3,3?-Hbpt)(Htm)]·H_2O(1,3,3?-Hbpt = 3,5-bis(3-pyridyl)-1H-1,2,4-triazole and H_3tm = trimesic acid),has been synthesized by hydrothermal reactions and characterized by single-crystal X-ray diffraction,elementary analysis,IR spectroscopy,thermogravimetric analysis and X-ray powder diffraction. Single-crystal X-ray diffraction indicates that the complex belongs to triclinic system,space group P 1 with a = 10.0911(1),b = 10.2573(1),c = 10.6393(1) ?,α = 103.793(2),β = 101.041(2),γ = 107.918(3)o,V = 974.9(2) ?~3,Z = 2,D_c = 1.732 g·cm-3,μ = 0.941 mm^(-1),M_r = 508.31,F(000) = 518,the final R = 0.0523 and wR = 0.0935 with I 〉 2σ(I). In the title complex,Co(Ⅱ) ions are connected by Htm2-anions generating 1D ladder-like chains which are linked by 3,3?-Hbpt to form 1D cages. In addition,the thermal decomposition of ammonium perchlorate(AP) with complex 1 was explored by differential scanning calorimetry(DSC). AP is completely decomposed in a shorter time in the presence of complex 1,and the decomposition heat of the mixture is 2.531 kJ·g^(-1),significantly higher than that of pure AP. By Kissinger's method,the ratio of Ea/ln(A) is 11.05 for the mixture,which indicates that complex 1 shows good catalytic activity toward the AP decomposition.展开更多
Ammonium perchlorate (AP), mainly used as solid propellants, was reported to interfere with homeostasis via competitive inhibition of iodide uptake. However, detailed mechanisms remain to be elucidated. In this stud...Ammonium perchlorate (AP), mainly used as solid propellants, was reported to interfere with homeostasis via competitive inhibition of iodide uptake. However, detailed mechanisms remain to be elucidated. In this study, AP was administered at 0, 130, 260 and 520 mg/kg every day to 24 male SD rats for 13 weeks. The concentrations of iodine in urine, serum thyroid hormones levels, to- tal iodine, relative iodine and total protein, and malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) activity in thyroid tissues were measured, respectively. Our results showed that high-dose perchlorate induced a significant increase in urinary iodine and serum thyroid stimu- lating hormone (TSH), with a decrease of total iodine and relative iodine content. Meanwhile, free thyroxine (FT4) was decreased and CAT activity was remarkably increased. Particularly, the CAT activity was increased in a dose-dependent manner. These results suggested that CAT might be en- hanced to promote the synthesis of iodine, resulting in elevated urinary iodine level. Furthermore, these findings suggested that iodine in the urine and CAT activity in the thyroid might be used as biomarkers for exposure to AP, associated with thyroid hormone indicators such as TSH. FT4.展开更多
V-Cr-Al-O nanospheres were successfully synthesized using V2O5, Al(OH)3, CrO3, and H2C2O4·H2O as the starting materials by a facile one-pot hydrothermal approach. Several techniques containing X-ray powder diffra...V-Cr-Al-O nanospheres were successfully synthesized using V2O5, Al(OH)3, CrO3, and H2C2O4·H2O as the starting materials by a facile one-pot hydrothermal approach. Several techniques containing X-ray powder diffraction, hydrogen temperature programmed reduction, scanning electron microscopy were used to characterize the composition, morphology and redox property of V-Cr-Al-O nanospheres. The catalytic behavior of prepared nanospheres on the thermal decomposition of AP was investigated by the thermogravimetric analysis and differential thermal analysis(TG/DTA). The experimental results show that the thermal decomposition temperature of AP in the presence of V-Cr-Al-O nanospheres is to 395 ℃(decreased by 35 ℃), which proves better catalyst for the thermal decomposition of AP.展开更多
Highly dispersed perovskite NdCoO3 nanoparticles were prepared by a novel salt-assisted combustion process. The effects of NaCl content and calcination temperature on the characteristics of the products were character...Highly dispersed perovskite NdCoO3 nanoparticles were prepared by a novel salt-assisted combustion process. The effects of NaCl content and calcination temperature on the characteristics of the products were characterized by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and BET surface area measurement. The facile introduction of NaCl in the conventional combustion synthesis process was found to result in the formation of well-dispersed perovskite nanoparticles and increase specific surface areas of the resultants from 1.7 to 43.2 m2·g-1. The catalytic properties of the typical NdCoO3 samples for thermal decomposition of ammonia perchlorate (AP) and their correlation with the NdCoO3 microstructure were investigated by Differential Scanning Calorimetry (DSC). The DSC results indicate that the addition of the amorphous NdCoO3 nanoparticles to AP incorporates two small exothermic peaks of AP into a strong exothermic peak, decreases the temperature of the AP exothermic peak to 314.0 ℃ by reduction of 138.3 ℃ and increases the apparent decomposition heat from 515 J·g-1 to over 1441 J·g-1, showing the intense catalytic activity for thermal decomposition of AP. It is also clear that the catalytic activity of the resultant NdCoO3 is related to their microstructure. According to Kissinger′s method, the kinetics parameters of the thermal decomposition of AP catalyzed by the as-prepared NdCoO3 samples were calculated to account for the order of their catalytic activity.展开更多
Ammonium perchlorate(AP)is the component with the highest content in composite propellants,and it plays a crucial role in propellant performance.In view of the effects of low-temperature AP thermal decomposition on th...Ammonium perchlorate(AP)is the component with the highest content in composite propellants,and it plays a crucial role in propellant performance.In view of the effects of low-temperature AP thermal decomposition on thermal safety and combustion characteristics,porous ammonium perchlorate(PAP)samples with different mass losses were first prepared by thermal convection heating,and the structures were characterized and analysed.Second,the effects of decomposition degree on the thermal decomposition characteristics of PAP were studied by DSC-TG.Finally,the combustion characteristics of AP/Al binary mixtures were tested with high-speed photography and in a sealed bomb.The results showed that low-temperature decomposition of AP resulted in formation of porous structures for AP particles.The pores first appeared near the surfaces of the particles and began from multiple points at the same time.The pores increased in size to approximately 5 mm and then expanded,and finally,the AP particles were full of pores.After partial decomposition,the crystal structure of AP remained unchanged,but the low and high decomposition temperatures decreased obviously.The decomposition rate accelerated.Due to the porous structure of PAP,the combustion rate of the AP/Al system increased obviously with increasing decomposition of AP.The relationship between the combustion rate and the mass loss was approximately linear under open conditions,and it was exponential for a high-pressure environment.A computational model of the combustion process for the AP/Al binary system was established to explain the effects of pore structure and pressure on the combustion process.展开更多
Given their unique and excellent properties,metal-organic frameworks(MOFs)materials have been used in many scientific fields.EMOFs use energetic materials as ligands,which can provide part of the energy for the system...Given their unique and excellent properties,metal-organic frameworks(MOFs)materials have been used in many scientific fields.EMOFs use energetic materials as ligands,which can provide part of the energy for the system while catalyzing ammonium perchlorate.The energetic material 1.1'-dihydroxyazotetrazole(H_(2)AzTO),as a high-energy nitrogen-rich material,was selected as a ligand.Five kinds of La^(3+),Ce^(3+),Pr^(3+),Nd^(3+),and Sm^(3+)lanthanide EMOFs were synthesized and obtained.Single crystal X-ray diffraction tests were conducted to obtain the crystal structures of EMOFs 1-5,which indicate that they have similar crystal structures.The thermal stabilities of EMOFs 1-5,which are obtained by differential scanning calorimetry(DSC)tests,are improved compa red with that of the ligand.The results of thermicdecomposition of ammonium perchlorate(AP)and AP mixtures with 10 wt%EMOFs 1-5 show that except for AP mixed with 10 wt%co mpound 2,the high-temperature decomposition peak tempe rature of AP mixed with other compounds is significantly advanced(up to 59.3-88.3 K),and the decomposition of AP is continuous and violent.EMOFs 3-5 have good application prospects for the catalytic thermicdecomposition of AP.展开更多
Three new cobalt(II) coordination compounds, [Co(3,3'-Hbpt)2(H2pm)(H20)2]'2H20 (1), [Co(4,4'-Hbpt)(pm)0.5(H20)]'3H20 (2) and [Co(3,4'-Hbpt)(pm)0.5(H20)3]'2H20 (3) (3,3'-Hbpt = 3,5-bis...Three new cobalt(II) coordination compounds, [Co(3,3'-Hbpt)2(H2pm)(H20)2]'2H20 (1), [Co(4,4'-Hbpt)(pm)0.5(H20)]'3H20 (2) and [Co(3,4'-Hbpt)(pm)0.5(H20)3]'2H20 (3) (3,3'-Hbpt = 3,5-bis(3-pyridyl)-lH-1,2,4-triazole; 4,4'-bpt = 3,5-bis(4-pyridyl)- 1H-1,2,4-triazole, 3,4'-Hbpt = 3-(3-pyridyl)-5-(4'-pyridyl)-lH-1,2,4-triazole and Hapm = pyromellitic acid) have been synthe- sized by hydrothermal reactions. Single-crystal X-ray diffraction reveals that compound 1 has a one-dimensional (1D) chain network, 2 exhibits a four-connected three-dimensional (3D) structure with 1D open channels encapsulated by water molecules, while 3 displays a regular two-dimensional (2D) architecture connected through 1D metal helical chains. In addition, the effi- cacy of compounds 1-3 as additives to promote the thermal decomposition of ammonium perchlorate (AP) is explored by dif- ferential scanning calorimetry (DSC).展开更多
In this study,four new energetic complexes(1)[Cu(vimi)_(4)]DCA_(2),(2)[Co(vimi)_(4)]DCA_(2),(3)[Ni(vimi)_(4)]DCA_(2),and(4)[Cu(vimi)_(4)]CBH_(2)(vimi:1-vinylimidazole,DCA:dicyanamide anion,CBH:cyanoborohydride anion)w...In this study,four new energetic complexes(1)[Cu(vimi)_(4)]DCA_(2),(2)[Co(vimi)_(4)]DCA_(2),(3)[Ni(vimi)_(4)]DCA_(2),and(4)[Cu(vimi)_(4)]CBH_(2)(vimi:1-vinylimidazole,DCA:dicyanamide anion,CBH:cyanoborohydride anion)were prepared,and their structures were characterized via single-crystal X-ray diffraction,elemental analysis,and Fourier-transform infrared spectroscopy.The catalytic effects of the complexes on ammonium perchlorate thermal decomposition were studied via thermal analysis methods,including differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).Among the complexes,complex 2 showed the best catalytic performance.The two decomposition peaks in the DSC curve of the pure ammonium perchlorate-low-temperature decomposition(LTD)peak:2950C and high-temperature decomposition(HTD)peak:418℃-were merged into a lower decomposition peak(325℃)in the curve of AP with complex 2.Moreover,the heat released by ammonium perchlorate with complex 2(1661.7 J g^(-1))was significantly higher than that released by the pure ammonium perchlorate(814.5 J g^(-1)).The kinetic parameters calculated using Kissinger's method revealed that the complexes had a significant effect on the activation energy of ammonium perchlorate decomposition(223.5 kJ mol^(-1)),and complex 2 lowered the activation energy to 115.6 kJ mol^(-1).The results indicate that complex 2 is a potential energetic additive for ammonium perchlorate-based solid propellants.展开更多
Nanoporous Gd2O3 powders(NGPs) with different specific surface areas were prepared by a nonaqueous sol-gel method and utilized to tune the exothermal decomposition of ammonium perchlorate(AP) for enhanced propellant e...Nanoporous Gd2O3 powders(NGPs) with different specific surface areas were prepared by a nonaqueous sol-gel method and utilized to tune the exothermal decomposition of ammonium perchlorate(AP) for enhanced propellant efficiency and improved safety.It is found that with the increasing dosage of NGPs into AP,the two exothermal peaks of AP merge into one intense exothermal peak,indicating that an "energy stacking" has been achieved.Meanwhile,the unique delay of the first exothermal peak of AP is conducive to the safety of AP in application process.Furthermore,the dependence of decomposition heat of AP on dosage and calcination temperature is more evident than on the surface areas of NGPs,suggesting that the promotion effect of NGPs on the thermal decomposition of AP does not only rely on the surface interaction.Therefore,an electron transfer mechanism is proposed to illustrate the decomposition process of AP tuned by NGPs.展开更多
The decomposition kinetic parameters of ammonium perchlorate(AP) having different grain size(10-390 μ m) were investigated through simultaneous DSC / TGA(differential scanning calorimetry / thermal gravimetric analys...The decomposition kinetic parameters of ammonium perchlorate(AP) having different grain size(10-390 μ m) were investigated through simultaneous DSC / TGA(differential scanning calorimetry / thermal gravimetric analysis) analyzer in a dynamic nitrogen atmosphere under heating rate of 40K / min.The kinetic parameters such as activation energy and pre-exponential factor were determined by the modified isoconversional method.The Brurzauer-Emmett-Teller(BET)-method was applied to measure AP specific surface areas.The results show that the higher the AP particle size the lower the determined kinetic parameters and are matched with some important literatures.展开更多
Three novel rare-earth,nitrogen-rich and oxygen heterocyclic supramolecular complexes,namely[Nd(BTF)_(2)(H_(2)O)_(5)]_(n),[Sm(BTF)_(2)(H_(2)O)_(5)]_(n),and[Eu(BTF)_(2)(H_(2)O)_(5)]_(n),were synthesized.A single crysta...Three novel rare-earth,nitrogen-rich and oxygen heterocyclic supramolecular complexes,namely[Nd(BTF)_(2)(H_(2)O)_(5)]_(n),[Sm(BTF)_(2)(H_(2)O)_(5)]_(n),and[Eu(BTF)_(2)(H_(2)O)_(5)]_(n),were synthesized.A single crystal was obtained by the solvent evaporation method,and the structure and coordination mode of metal complexes were determined by single crystal X-ray diffraction.Results show that the supramolecular complexes contain many hydrogen bonds and thus have good thermal stability(T_(dec)>540 K).The thermal decomposition of ammonium perchlorate(AP)catalyzed by the complexes was investigated by differential thermal analysis,which reveals a pre-eminent catalytic effect on AP.The high temperature decomposition peak of AP can be advanced by nearly 90 K at the amount of added complexes of 10 wt%,and the activation energy of AP descent range is from 70 to 150 kJ/mol.The other properties were fully characterized through elemental analysis and Fourier transform infrared spectroscopy.展开更多
Thermogravimetry-differential scanning calorimetry-mass spectrometry-Fourier transform infrared spectrometry(TG-DSC-MS-FTIR) simultaneous analysis was used to study the effects of 10.7 μm and 40 nm Al on the therma...Thermogravimetry-differential scanning calorimetry-mass spectrometry-Fourier transform infrared spectrometry(TG-DSC-MS-FTIR) simultaneous analysis was used to study the effects of 10.7 μm and 40 nm Al on the thermal decomposition of the Hexogen/ammonium perchlorate(RDX/AP,1/2,mass ratio) mixture.TG-DSC results show that there are two mass loss processes for the thermal decomposition of RDX/AP/Al.The first one is mainly ascribed to the thermal decomposition of RDX.The reaction rate of RDX/AP/10.7 μm Al is so fast that the apparent activation energy,calculated by model-free Friedman method,is negative,which is the same as that of RDX/AP.30%(mass fraction) 40 nm Al added in RDX/AP change the activation energy from negative to positive value.The second mass loss process of the RDX/AP/A1 mixture is ascribed to the thermal decomposition of AP.This process can be divided into three stages for RDX/AP with and without Al.The kinetics model is not changed in the presence of micro-sized Al,while it is changed from CnB/D1/D1 to CnB/D1/D4 after the addition of 40 nm Al to RDX/AP.The reaction rate constant of the first stage and the end temperature of the second stage decrease,while the end temperatures of the third stage increase in the presence of 40 nm Al.The MS-FTIR results show there is a competition between the formation reactions of HNCO,N2O and NO2 during the second mass loss process.展开更多
To investigate the process optimizationof Cu-en/AP composite microspheres preparation via electrostatic spraying,and to reveal the effects of droplet properties and flow rate variations on the experimental results dur...To investigate the process optimizationof Cu-en/AP composite microspheres preparation via electrostatic spraying,and to reveal the effects of droplet properties and flow rate variations on the experimental results during the electrostatic spraying process,the prepared process parameters of Cu-en/AP composite microspheres by electrostatic spray method under the orthogonal experimental design simulated by ANSYS(Fluent).The influence of flow rate,solvent ratio,and solid mass on the experimental results is examined using a controlled variable method.The results indicate that under the conditions of a flow rate of 2.67×10^(-3)kg/s an acetone-to-deionized water ratio of 1.5∶1.0,and a solid mass of 200 mg,the theoretical particle size of the composite microspheres can reach e nanoscale.Droplet trajectories in the electric field remain stable without significant deviation.The simulation results show that particle diameter decreases with increasing flow rate,with the trend leveling off around a flow rate of 1×10^(-3)kg/s.As the solvent ratio increases(with higher acetone content),particle diameter initially decreases,reaching a minimum around a ratio of 1.5∶1.0 before gradually increasing.Increasing the solid mass also reduces the particle diameter,with a linear increase in diameter observed at around 220 mg.Cu-en/AP composite microspheres with nanoscale dimensions were confirmed under these conditions by the final SEM images.展开更多
Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination te...Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination temperature on crystallite size of the products were studied. The catalytic performance of the as-prepared yttria for the ammonium perchlorate (AP) decomposition was investigated by differential scanning calorimetry (DSC). The results indicate that the nano-sized cubic yttria particles with less than 20 nm in average crystallite size can be obtained after 2 h reflux at 70℃, dried at 90 ℃, forming xerogel, and followed by annealing of xerogel for 2 h, and that the addition of the nano-sized yttria to AP incorporates two small exothermic peaks of AP in the temperature ranges of 310 - 350 ℃ and 400 - 470 ℃ into a strong exothermic peak of AP and increases the apparent decomposition heat from 515 to over 1110 J·g^- 1. It is also clear that the temperature of AP decomposition exothermic peak decreases and the apparent decomposition heat of AP increases with the increase of the amount of nano-sized yttria. The fact that the addition of the 5 % nano-sized yttria to AP decreases the temperature of AP exothermic peak to 337.7℃ by reduction of 114.6℃ and increases the apparent decomposition heat from 515 to 1240 J·g^-1, reveals that nano-sized yttria shows strong catalytic property for AP thermal decomposition.展开更多
基金supported by the National Natural Science Foundation of China,China(Grant Nos.U20B2018,U21B2086,11972087)。
文摘A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.
基金the financial support received from the Natural Science Foundation of China(21875192)Outstanding Youth Science and Technology Talents Program of Sichuan(no.19JCQN0085)Open Project of State Key Laboratory of Environment-friendly Energy Materials(Southwest University of Science and Technology,No.22fksy18)。
文摘Biomass chitosan(CS)was used as a template,graphitic phase carbon nitride(g-C_(3)N_(4))with high nitrogen content and certain catalytic activity was used as a dopant,and nano-transition metal cobalt(Co)was used as a catalytic center point.The carbon aerogel(C(CS)/g-C_(3)N_(4)/Co)with a three-dimensional network-like structure was prepared by assembling the three materials through experimental operations such as freeze-drying and high-temperature carbonization.It was demonstrated by scanning and transmission characterization that the CS in the carbon aerogel could provide more active sites for the cobalt nanoparticles,and the doping of graphite-phase carbon nitride as a template dispersed the cobalt nanoparticles and changed the conductivity of the CS.To investigate the catalytic effect of carbon aerogel on ammonium perchlorate(AP),it was investigated by differential thermal analyzer and TG thermal analysis.This carbon aerogel was very effective in catalyzing AP,and the 10 wt% content of the catalyst reduced the AP pyrolysis peak from 703.9 to 595.5 K.And to further investigate the synergistic effect of the three materials,further carbon aerogels such as C(CS)/Co,g-C_(3)N_(4)/Co were prepared and applied to catalyze AP,and the same ratio reduced the AP pyrolysis peak by 98.1℃ and 97.7℃.This result indicates a synergistic effect of the assembly of the three materials.
基金Supported by the National Natural Science Foundation of China (50306008, 50602024).
文摘The monodispersed Co nanoparticles were successfully prepared by means of hydrogen plasma method in inert atmosphere. The particle size, specific surface area, crystal structure and morphology of the samples were characterized by transmission electron microscopy (TEM), BET equation, X-ray diffraction (XRD), and the corresponding selected area electron diffraction (SAED). The catalytic effect of Co nanoparticles on the decomposition of ammonium perchlorate (AP) was investigated by differential thermal analyzer (DTA). Compared with the thermal decomposition of pure AP, the addition of Co nanoparticles (2%-10%, by mass) decreases the decomposition temperature of AP by 145.01-155.72℃. Compared with Co3O4 nano-particles and microsized Co particles, the catalytic effect of Co nanoparticles for AP is stronger. Such effect is attributed to the large specific surface area and its interaction of Co with decomposition intermediate gases. The present work provides useful information for the application of Co nanoparficles in the AP-based propellant.
文摘Ammonium perchlorate(APC)is the most common oxidizer in use for solid rocket propulsion systems.However its initial thermal decomposition is an endothermic process that requires 102.5 J·g^-1.This manner involves high activation energy and could render high burning rate regime.This study reports on the sustainable fabrication of CuO nanoparticles as a novel catalyzing agent for APC oxidizer.Colloidal CuO nanoparticles with consistent product quality were fabricated by using hydrothermal processing.TEM micrographs demonstrated mono-dispersed particles of 15 nm particle size.XRD diffractogram demonstrated highly crystalline material.The synthesized colloidal CuO particles were effectively coated with APC particles via co-precipitation by using fast-crash solvent-antisolvent technique.The impact of copper oxide particles on APC thermal behavior has been investigated using DSC and TGA techniques.APC demonstrated an initial endothermic decomposition stage at 242℃ with subsequent two exothermic decomposition stages at 297,8℃ and 452.8℃ respectively.At 1 wt%,copper oxide offered decrease in initial endothermic decomposition stage by 30%.The main outcome of this study is that the two main exothermic decomposition peaks were merged into one single peak with an increase in total heat release by 53%.These novel features can inherit copper oxide particles unique catalyzing ability for advanced highly energetic systems.
基金Supported by the National Natural Science Foundation of China(No.21263019)
文摘A new energetic complex, Ni(3,4'-Hbpt)2(Hoba)2(H20)2 (3,4'-Hbpt = 3-(3-pyridyl)- 5-(4'-pyridyl)-l-H-l,2,4-triazole and H2oba = 4,4'-oxybis(benzoic acid)), has been synthesized by hydrothermal reaction and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, thermogravimetric analyses and X-ray powder diffraction. Single-crystal X-ray diffraction analysis indicates that the complex belongs to the monoclinic system, space group P2j/c with a = 10.2357(9), b = 24.594(2), c = 10.4225(9)/k, β = 114.0110(10)°, V = 2396.7(4) A3, Dc = 1.460 g/cm3,μ = 0.482 mm-1, Mr = 1053.63, F(000) = 1088, Z = 2, the final R = 0.0358 and wR = 0.0973 with I 〉 2σ(I). Both 3,4'-Hbpt and H2oba ligands adopt monodentate modes linking one Ni(II) ion to form a 0D motif. Furthermore, the 0D motifs are linked into a 3D supramolecular architecture with hydrogen bonds. In addition, the catalytic performance for thermal decomposition of the efficacy of ammonium perchlorate (AP) is explored by differential scanning calorimetry (DSC), which indicates that the complex is a good candidate for a promoter of the thermal decomposition of ammonium perchlorate.
基金This work was financially supported by the Science and Technology project of Jiangsu province(BN2015021,XZ-SZ201819).
文摘As a main oxidizer in solid composite propellants,ammonium perchlorate(AP)plays an important role because its thermal decomposition behavior has a direct influence on the characteristic of solid composite propellants.To improve the performance of solid composite propellant,it is necessary to take measures to modify the thermal decomposition behavior of AP.In recent years,transition metal oxides and carbon-supported transition metal oxides have drawn considerable attention due to their extraordinary catalytic activity.In this review,we highlight strategies to enhance the thermal decomposition of AP by tuning morphology,varying the types of metal ion,and coupling with carbon analogue.The enhanced catalytic performance can be ascribed to synergistic effect,increased surface area,more exposed active sites,and accelerated electron transportation and so on.The mechanism of AP decomposition mixed with catalyst has also been briefly summarized.Finally,a conclusive outlook and possible research directions are suggested to address challenges such as lacking practical application in actual formulation of solid composite propellant and batch manufacturing.
基金Supported by the National Natural Science Foundation of China(No.21263019 and 21467022)
文摘A new energetic complex,[Co(3,3?-Hbpt)(Htm)]·H_2O(1,3,3?-Hbpt = 3,5-bis(3-pyridyl)-1H-1,2,4-triazole and H_3tm = trimesic acid),has been synthesized by hydrothermal reactions and characterized by single-crystal X-ray diffraction,elementary analysis,IR spectroscopy,thermogravimetric analysis and X-ray powder diffraction. Single-crystal X-ray diffraction indicates that the complex belongs to triclinic system,space group P 1 with a = 10.0911(1),b = 10.2573(1),c = 10.6393(1) ?,α = 103.793(2),β = 101.041(2),γ = 107.918(3)o,V = 974.9(2) ?~3,Z = 2,D_c = 1.732 g·cm-3,μ = 0.941 mm^(-1),M_r = 508.31,F(000) = 518,the final R = 0.0523 and wR = 0.0935 with I 〉 2σ(I). In the title complex,Co(Ⅱ) ions are connected by Htm2-anions generating 1D ladder-like chains which are linked by 3,3?-Hbpt to form 1D cages. In addition,the thermal decomposition of ammonium perchlorate(AP) with complex 1 was explored by differential scanning calorimetry(DSC). AP is completely decomposed in a shorter time in the presence of complex 1,and the decomposition heat of the mixture is 2.531 kJ·g^(-1),significantly higher than that of pure AP. By Kissinger's method,the ratio of Ea/ln(A) is 11.05 for the mixture,which indicates that complex 1 shows good catalytic activity toward the AP decomposition.
基金supported by the National Natural Science Foundation of China(No.30972452)
文摘Ammonium perchlorate (AP), mainly used as solid propellants, was reported to interfere with homeostasis via competitive inhibition of iodide uptake. However, detailed mechanisms remain to be elucidated. In this study, AP was administered at 0, 130, 260 and 520 mg/kg every day to 24 male SD rats for 13 weeks. The concentrations of iodine in urine, serum thyroid hormones levels, to- tal iodine, relative iodine and total protein, and malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) activity in thyroid tissues were measured, respectively. Our results showed that high-dose perchlorate induced a significant increase in urinary iodine and serum thyroid stimu- lating hormone (TSH), with a decrease of total iodine and relative iodine content. Meanwhile, free thyroxine (FT4) was decreased and CAT activity was remarkably increased. Particularly, the CAT activity was increased in a dose-dependent manner. These results suggested that CAT might be en- hanced to promote the synthesis of iodine, resulting in elevated urinary iodine level. Furthermore, these findings suggested that iodine in the urine and CAT activity in the thyroid might be used as biomarkers for exposure to AP, associated with thyroid hormone indicators such as TSH. FT4.
基金Funded by the National Natural Science Foundation of China(51572201)
文摘V-Cr-Al-O nanospheres were successfully synthesized using V2O5, Al(OH)3, CrO3, and H2C2O4·H2O as the starting materials by a facile one-pot hydrothermal approach. Several techniques containing X-ray powder diffraction, hydrogen temperature programmed reduction, scanning electron microscopy were used to characterize the composition, morphology and redox property of V-Cr-Al-O nanospheres. The catalytic behavior of prepared nanospheres on the thermal decomposition of AP was investigated by the thermogravimetric analysis and differential thermal analysis(TG/DTA). The experimental results show that the thermal decomposition temperature of AP in the presence of V-Cr-Al-O nanospheres is to 395 ℃(decreased by 35 ℃), which proves better catalyst for the thermal decomposition of AP.
基金the National Natural Science Foundation of China (50306008)Start up Research Fund of Nanchang University and the Natural Science Foundation of Higher Education Institutions in Anhui Province (KJ2007B231)
文摘Highly dispersed perovskite NdCoO3 nanoparticles were prepared by a novel salt-assisted combustion process. The effects of NaCl content and calcination temperature on the characteristics of the products were characterized by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and BET surface area measurement. The facile introduction of NaCl in the conventional combustion synthesis process was found to result in the formation of well-dispersed perovskite nanoparticles and increase specific surface areas of the resultants from 1.7 to 43.2 m2·g-1. The catalytic properties of the typical NdCoO3 samples for thermal decomposition of ammonia perchlorate (AP) and their correlation with the NdCoO3 microstructure were investigated by Differential Scanning Calorimetry (DSC). The DSC results indicate that the addition of the amorphous NdCoO3 nanoparticles to AP incorporates two small exothermic peaks of AP into a strong exothermic peak, decreases the temperature of the AP exothermic peak to 314.0 ℃ by reduction of 138.3 ℃ and increases the apparent decomposition heat from 515 J·g-1 to over 1441 J·g-1, showing the intense catalytic activity for thermal decomposition of AP. It is also clear that the catalytic activity of the resultant NdCoO3 is related to their microstructure. According to Kissinger′s method, the kinetics parameters of the thermal decomposition of AP catalyzed by the as-prepared NdCoO3 samples were calculated to account for the order of their catalytic activity.
基金the National Natural Science Foundation of China(Grant No.11772058).
文摘Ammonium perchlorate(AP)is the component with the highest content in composite propellants,and it plays a crucial role in propellant performance.In view of the effects of low-temperature AP thermal decomposition on thermal safety and combustion characteristics,porous ammonium perchlorate(PAP)samples with different mass losses were first prepared by thermal convection heating,and the structures were characterized and analysed.Second,the effects of decomposition degree on the thermal decomposition characteristics of PAP were studied by DSC-TG.Finally,the combustion characteristics of AP/Al binary mixtures were tested with high-speed photography and in a sealed bomb.The results showed that low-temperature decomposition of AP resulted in formation of porous structures for AP particles.The pores first appeared near the surfaces of the particles and began from multiple points at the same time.The pores increased in size to approximately 5 mm and then expanded,and finally,the AP particles were full of pores.After partial decomposition,the crystal structure of AP remained unchanged,but the low and high decomposition temperatures decreased obviously.The decomposition rate accelerated.Due to the porous structure of PAP,the combustion rate of the AP/Al system increased obviously with increasing decomposition of AP.The relationship between the combustion rate and the mass loss was approximately linear under open conditions,and it was exponential for a high-pressure environment.A computational model of the combustion process for the AP/Al binary system was established to explain the effects of pore structure and pressure on the combustion process.
基金Project supported by the National Natural Science Foundation of China(21875192)the Basic Research Project of Sichuan Province for Science and Technology Development(2019YJ0355)+1 种基金Outstanding Youth Science and Technology Talents Program of Sichuan(19JCQN0085)the Project of State Key Laboratory of Environment-friendly Energy Materials,Southwest University of Science and Technology(20fksy04)。
文摘Given their unique and excellent properties,metal-organic frameworks(MOFs)materials have been used in many scientific fields.EMOFs use energetic materials as ligands,which can provide part of the energy for the system while catalyzing ammonium perchlorate.The energetic material 1.1'-dihydroxyazotetrazole(H_(2)AzTO),as a high-energy nitrogen-rich material,was selected as a ligand.Five kinds of La^(3+),Ce^(3+),Pr^(3+),Nd^(3+),and Sm^(3+)lanthanide EMOFs were synthesized and obtained.Single crystal X-ray diffraction tests were conducted to obtain the crystal structures of EMOFs 1-5,which indicate that they have similar crystal structures.The thermal stabilities of EMOFs 1-5,which are obtained by differential scanning calorimetry(DSC)tests,are improved compa red with that of the ligand.The results of thermicdecomposition of ammonium perchlorate(AP)and AP mixtures with 10 wt%EMOFs 1-5 show that except for AP mixed with 10 wt%co mpound 2,the high-temperature decomposition peak tempe rature of AP mixed with other compounds is significantly advanced(up to 59.3-88.3 K),and the decomposition of AP is continuous and violent.EMOFs 3-5 have good application prospects for the catalytic thermicdecomposition of AP.
基金supported by the National Natural Science Foundation of China(21073142,21173168and21127004)the Natural Science Foundation of Shaanxi Province(SJ08B09)the Natural Science Foundation of the Department of Education of Shaanxi Province(2010JK882,2010JQ2007and11JS110)
文摘Three new cobalt(II) coordination compounds, [Co(3,3'-Hbpt)2(H2pm)(H20)2]'2H20 (1), [Co(4,4'-Hbpt)(pm)0.5(H20)]'3H20 (2) and [Co(3,4'-Hbpt)(pm)0.5(H20)3]'2H20 (3) (3,3'-Hbpt = 3,5-bis(3-pyridyl)-lH-1,2,4-triazole; 4,4'-bpt = 3,5-bis(4-pyridyl)- 1H-1,2,4-triazole, 3,4'-Hbpt = 3-(3-pyridyl)-5-(4'-pyridyl)-lH-1,2,4-triazole and Hapm = pyromellitic acid) have been synthe- sized by hydrothermal reactions. Single-crystal X-ray diffraction reveals that compound 1 has a one-dimensional (1D) chain network, 2 exhibits a four-connected three-dimensional (3D) structure with 1D open channels encapsulated by water molecules, while 3 displays a regular two-dimensional (2D) architecture connected through 1D metal helical chains. In addition, the effi- cacy of compounds 1-3 as additives to promote the thermal decomposition of ammonium perchlorate (AP) is explored by dif- ferential scanning calorimetry (DSC).
基金the National Natural Science Foundation of China(Grant No.21805008)the Beijing Institute of Technology Research Fund Program for Young Scholars.
文摘In this study,four new energetic complexes(1)[Cu(vimi)_(4)]DCA_(2),(2)[Co(vimi)_(4)]DCA_(2),(3)[Ni(vimi)_(4)]DCA_(2),and(4)[Cu(vimi)_(4)]CBH_(2)(vimi:1-vinylimidazole,DCA:dicyanamide anion,CBH:cyanoborohydride anion)were prepared,and their structures were characterized via single-crystal X-ray diffraction,elemental analysis,and Fourier-transform infrared spectroscopy.The catalytic effects of the complexes on ammonium perchlorate thermal decomposition were studied via thermal analysis methods,including differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).Among the complexes,complex 2 showed the best catalytic performance.The two decomposition peaks in the DSC curve of the pure ammonium perchlorate-low-temperature decomposition(LTD)peak:2950C and high-temperature decomposition(HTD)peak:418℃-were merged into a lower decomposition peak(325℃)in the curve of AP with complex 2.Moreover,the heat released by ammonium perchlorate with complex 2(1661.7 J g^(-1))was significantly higher than that released by the pure ammonium perchlorate(814.5 J g^(-1)).The kinetic parameters calculated using Kissinger's method revealed that the complexes had a significant effect on the activation energy of ammonium perchlorate decomposition(223.5 kJ mol^(-1)),and complex 2 lowered the activation energy to 115.6 kJ mol^(-1).The results indicate that complex 2 is a potential energetic additive for ammonium perchlorate-based solid propellants.
基金Project supported by the National Natural Science Foundation of China(51864033,51274123,21761020)the National Key Basic Research Program of China(973 Program,2012CBA01204)Jiangxi Provincial Scientific&Technological Support Project of China(20132BBE500041)
文摘Nanoporous Gd2O3 powders(NGPs) with different specific surface areas were prepared by a nonaqueous sol-gel method and utilized to tune the exothermal decomposition of ammonium perchlorate(AP) for enhanced propellant efficiency and improved safety.It is found that with the increasing dosage of NGPs into AP,the two exothermal peaks of AP merge into one intense exothermal peak,indicating that an "energy stacking" has been achieved.Meanwhile,the unique delay of the first exothermal peak of AP is conducive to the safety of AP in application process.Furthermore,the dependence of decomposition heat of AP on dosage and calcination temperature is more evident than on the surface areas of NGPs,suggesting that the promotion effect of NGPs on the thermal decomposition of AP does not only rely on the surface interaction.Therefore,an electron transfer mechanism is proposed to illustrate the decomposition process of AP tuned by NGPs.
文摘The decomposition kinetic parameters of ammonium perchlorate(AP) having different grain size(10-390 μ m) were investigated through simultaneous DSC / TGA(differential scanning calorimetry / thermal gravimetric analysis) analyzer in a dynamic nitrogen atmosphere under heating rate of 40K / min.The kinetic parameters such as activation energy and pre-exponential factor were determined by the modified isoconversional method.The Brurzauer-Emmett-Teller(BET)-method was applied to measure AP specific surface areas.The results show that the higher the AP particle size the lower the determined kinetic parameters and are matched with some important literatures.
基金project supported by the National Natural Science Foundation of China(21875192)Outstanding Youth Science and Technology Talents Program of Sichuan(19JCQN0085)the Basic Research Project of Sichuan Province for Science and Technology Development(2019YJ0355)。
文摘Three novel rare-earth,nitrogen-rich and oxygen heterocyclic supramolecular complexes,namely[Nd(BTF)_(2)(H_(2)O)_(5)]_(n),[Sm(BTF)_(2)(H_(2)O)_(5)]_(n),and[Eu(BTF)_(2)(H_(2)O)_(5)]_(n),were synthesized.A single crystal was obtained by the solvent evaporation method,and the structure and coordination mode of metal complexes were determined by single crystal X-ray diffraction.Results show that the supramolecular complexes contain many hydrogen bonds and thus have good thermal stability(T_(dec)>540 K).The thermal decomposition of ammonium perchlorate(AP)catalyzed by the complexes was investigated by differential thermal analysis,which reveals a pre-eminent catalytic effect on AP.The high temperature decomposition peak of AP can be advanced by nearly 90 K at the amount of added complexes of 10 wt%,and the activation energy of AP descent range is from 70 to 150 kJ/mol.The other properties were fully characterized through elemental analysis and Fourier transform infrared spectroscopy.
基金Supported by the National Natural Science Foundation of China(Nos.11172042, 51304024) and the Scientific Research Foundation for Retumed Overseas Students, Ministry of Education, China.
文摘Thermogravimetry-differential scanning calorimetry-mass spectrometry-Fourier transform infrared spectrometry(TG-DSC-MS-FTIR) simultaneous analysis was used to study the effects of 10.7 μm and 40 nm Al on the thermal decomposition of the Hexogen/ammonium perchlorate(RDX/AP,1/2,mass ratio) mixture.TG-DSC results show that there are two mass loss processes for the thermal decomposition of RDX/AP/Al.The first one is mainly ascribed to the thermal decomposition of RDX.The reaction rate of RDX/AP/10.7 μm Al is so fast that the apparent activation energy,calculated by model-free Friedman method,is negative,which is the same as that of RDX/AP.30%(mass fraction) 40 nm Al added in RDX/AP change the activation energy from negative to positive value.The second mass loss process of the RDX/AP/A1 mixture is ascribed to the thermal decomposition of AP.This process can be divided into three stages for RDX/AP with and without Al.The kinetics model is not changed in the presence of micro-sized Al,while it is changed from CnB/D1/D1 to CnB/D1/D4 after the addition of 40 nm Al to RDX/AP.The reaction rate constant of the first stage and the end temperature of the second stage decrease,while the end temperatures of the third stage increase in the presence of 40 nm Al.The MS-FTIR results show there is a competition between the formation reactions of HNCO,N2O and NO2 during the second mass loss process.
基金National Natural Science Foundation of China(No.2275150)。
文摘To investigate the process optimizationof Cu-en/AP composite microspheres preparation via electrostatic spraying,and to reveal the effects of droplet properties and flow rate variations on the experimental results during the electrostatic spraying process,the prepared process parameters of Cu-en/AP composite microspheres by electrostatic spray method under the orthogonal experimental design simulated by ANSYS(Fluent).The influence of flow rate,solvent ratio,and solid mass on the experimental results is examined using a controlled variable method.The results indicate that under the conditions of a flow rate of 2.67×10^(-3)kg/s an acetone-to-deionized water ratio of 1.5∶1.0,and a solid mass of 200 mg,the theoretical particle size of the composite microspheres can reach e nanoscale.Droplet trajectories in the electric field remain stable without significant deviation.The simulation results show that particle diameter decreases with increasing flow rate,with the trend leveling off around a flow rate of 1×10^(-3)kg/s.As the solvent ratio increases(with higher acetone content),particle diameter initially decreases,reaching a minimum around a ratio of 1.5∶1.0 before gradually increasing.Increasing the solid mass also reduces the particle diameter,with a linear increase in diameter observed at around 220 mg.Cu-en/AP composite microspheres with nanoscale dimensions were confirmed under these conditions by the final SEM images.
基金Project supported by the National Natural Science Foundation of China (50306008)Advance Research Foundation forGeneral Equipment Department (41328030507)
文摘Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination temperature on crystallite size of the products were studied. The catalytic performance of the as-prepared yttria for the ammonium perchlorate (AP) decomposition was investigated by differential scanning calorimetry (DSC). The results indicate that the nano-sized cubic yttria particles with less than 20 nm in average crystallite size can be obtained after 2 h reflux at 70℃, dried at 90 ℃, forming xerogel, and followed by annealing of xerogel for 2 h, and that the addition of the nano-sized yttria to AP incorporates two small exothermic peaks of AP in the temperature ranges of 310 - 350 ℃ and 400 - 470 ℃ into a strong exothermic peak of AP and increases the apparent decomposition heat from 515 to over 1110 J·g^- 1. It is also clear that the temperature of AP decomposition exothermic peak decreases and the apparent decomposition heat of AP increases with the increase of the amount of nano-sized yttria. The fact that the addition of the 5 % nano-sized yttria to AP decreases the temperature of AP exothermic peak to 337.7℃ by reduction of 114.6℃ and increases the apparent decomposition heat from 515 to 1240 J·g^-1, reveals that nano-sized yttria shows strong catalytic property for AP thermal decomposition.