Propellant Energy Research Articles

Study on meso-damage evolution process of high-energy propellant based on MCT

The complex microstructure of composite solid propellant makes the evolution of meso-damage very complicated during loading. It is always a hot issue to study the damage evolution law of propellant from the microscopic point of view.Based on the established tensile platform of MCT, the tensile test of high energy propellant specimens was carried out. The variation trend of internal porosity with the increase of tensile strain is obtained. It can be seen that during the drawing process, the internal porosity of high-energy propellant increases exponentially with the drawing rate.

Study on erosion-reducing additives and erosion inhibition principle for R2 high energy propellant

In view of the serious erosion problem of the gun barrel with the R2 high-energy propellant, an erosion tube device method was adopted, and silane organic substances, silicate inorganic substances, titanium dioxide nanoparticles and paraffin wax were selected as erosion-reducing additives. The effect of different erosion-reducing additives on the erosive property of R2 propellant was investigated by means of external addition. The erosion inhibition principle was also briefly investigated by scanning electron microscope and energy dispersive X-ray spectroscopy. The results show that paraffin wax has excellent ability to improve gun barrel erosion resistance, the erosion-reducing efficiency can reach up to 31.2%, the erosion-reducing efficiency of silanes is the next most effective, and silicate is poor.

Theoretical and Experimental Investigation of Geomagnetic Energy Effect for LEO Debris Deorbiting

Space debris is increasingly problematic and needs active removal, especially in low Earth orbits (LEO). Paying for the vast cost of the disposal of debris from the situation is still inevitable even though pivotal technical hurdles have been overcome with the growing maturity of capturing and deorbiting methods. To this end, a novel geomagnetic energy (GME) propellant approach is firstly proposed to propel a spinning tethered spacecraft for LEO debris deorbiting, without the use of expendable fuel and a large-length tether. In this method, the time-cumulative effect of the interacted torque of the spacecraft’s electromagnet and geomagnetic field is used to accelerate the rotating system for GME storage, and the space momentum exchange from the angular momentum of system to the linear momentum of debris is introduced to deorbit the debris for GME release. Next, an on-orbit directional GME storage mechanism is built, and the corresponding two optimal strategies are put forward. Both theoretical and simulation results demonstrate that GME can be stored in the expected direction on any inclined LEO below 1000 km. Deorbiting kg-level debris can be accomplished within several orbital periods with the existing magnetorquer technology. Finally, proof-of-principle experiments of the GME effect are performed and elementarily validate the LEO GME utilization in space.

Enhancement strategy of mechanical property by constructing of energetic RDX@CNFs composites in propellants, and investigation on its combustion and sensitivity behavior

In the domain of energetic materials (EMs), the high-energy and high-strength propellants are always what are the scientists pursuing to satisfy the great demands of fast development and replacement for artillery. Recently, the emerging of cellulose nanofibers (CNFs) has attracted great interests since its extraordinary performances like biocompatibility, carbon-neutral nature, tailorable surface chemistry, and unprecedented mechanical properties. Inspired by the fascinating high strengthen of CNFs, this study prepared a kind of energetic hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)@CNFs composites firstly, and then applied them in conventional double-based gun propellant (GP) to study its energy, combustion and mechanical, and sensitivity performances. The results of the mechanical properties demonstrated that the impact strength of RDX@CNFs-GP with different content of CNFs was improved by 34.9-104.7%, 7.1-39.4%, 14.4-51.2% under the condition of low, room and high temperature, the compression strength was improved by 8.6-49.5%, 4.3-45.9%, 6.2-47.8%, while the tensile strength was improved by 0.6-21.2%, 7.0-19.5%, 9.0-26.0%, respectively. Moreover, the impact and electrostatic spark sensitivities have also been increased by 21.8% and 61.8% in terms of the maximum value and exert favorable desensitization effect compared with blank sample. Notably, the propellant added with CNFs could burn steadily without anomalous combustion behavior, and the energy level of the RDX@CNFs-2.0%-GP (1180.70 J/g) maintain relative close value to that of RDX@CNFs-0%-GP (1184.84 J/g) with regard to the gunpowder impetus. Lastly, the enhancement mechanism of the CNFs in GP was discussed and proposal. Hence, this present work could potentially provide fundamental theory and data support for the development of CNFs in high-strength and high energy propellants.

Prediction of material properties of propellant waste modified bricks through microstructures by Topographic independent component analysis coupled 3D Convolution neural networks

PurposeDeciphering materials properties from the textural information of microstructural images is still a challenge. ObjectiveProposes a Topographic Independent Component Analysis coupled with 3-D Convolutional Neural Network (TICA- 3DCNN) architecture that processes the features from scanning electron microscope (SEM) images to predict the material properties of high energy propellant (HEP) modified bricks. MethodFirst, high-energy modified bricks with ten different HEP additives fractions is prepared, and their microstructural information is acquired with SEM. Then, SEM images of each group are pre-processed and subjected to the TICA analysis to decipher the distinct higher-order microstructural dependencies, such as co-activation of components. These microstructural co-activation components are subsequently ordered and passed into 3D CNN architecture to map them with the material properties such as water absorption, compressive strength, density, and porosity. An extreme learning machine is employed as a fully connected classification layer in the 3D-CNN architecture. Finally, the performance of the proposed TICA - 3DCNN approach is compared with the traditional 2D CNN frameworks such as Inception-v4 and Faster RCNN. ResultsProposed TICA-3DCNN architecture has performed with higher sensitivity and specificity than Inception-v4 and Faster RCNN architecture in deciphering microstructural textural properties and mapping them with materials properties. ConclusionThe Proposed model can be used in the construction and building materials to predict material properties through microstructural features.

Orchestration of energy metabolism and osteogenesis by Mg2+ facilitates low-dose BMP-2-driven regeneration

The clinical application of bone morphogenetic protein-2 (BMP-2) is limited by several factors, including ineffectiveness at low doses and severe adverse effects at high doses. To address these efficacy and safety limitations, we explored whether orchestration of energy metabolism and osteogenesis by magnesium ion (Mg2+) could reduce the dose and thereby improve the safety of BMP-2. Our results demonstrated that rapid metabolic activation triggered by BMP-2 was indispensable for subsequent osteogenesis. Moreover, inadequate metabolic stimulation was shown to be responsible for the ineffectiveness of low-dose BMP-2. Next, we identified that Mg2+, as an ''energy propellant", substantially increased cellular bioenergetic levels to support the osteogenesis via the Akt-glycolysis-Mrs2-mitochondrial axis, and consequently enhanced the osteoinductivity of BMP-2. Based on the mechanistic discovery, microgel composite hydrogels were fabricated as low-dose BMP-2/Mg2+ codelivery system through microfluidic and 3D printing technologies. An in vivo study further confirmed that rapid and robust bone regeneration was induced by the codelivery system. Collectively, these results suggest that this bioenergetic-driven, cost-effective, low-dose BMP-2-based strategy has substantial potential for bone repair.

Synthesis of Novel Hexaazaisowurtzitane Cages to Access CL‐20

AbstractA novel hexacyclopropylhexaazaisowurtzitane (HCPIW) and hexacyclobutylhexaazaisowurtzitane (HCBIW) cage compounds were synthesized using a straightforward method by reacting glyoxal with the corresponding cycloalkylamines such as cyclopropylamine and cyclobutylamine in the presence of a catalytic amount of an acid. The obtained compounds were characterized in detail by spectroscopic and X‐ray diffraction analyses. HCPIW and HCBIW with 99% and 98% purity were obtained without column chromatography. Nitration of HCPIW with H2SO4/HNO3 in dichloromethane solvent successfully afforded CL‐20, high energy propellant and explosive in 25% yield.

Utilisation of High Energy Propellant Waste in Manufacturing of Fired Clay Bricks to Enhance the Acoustic Properties

The disposal and waste management of solid high energy propellant (HEP) is a considerate conservational problem. HEP waste is currently disposed in open or confined burning which may cause environmental hazards. In this paper, we examined and discussed results on recycling of HEP waste into fired clay bricks baked in different orientation. HEP modified bricks with 1.5%, 3% and 5 wt. % HEP waste content were manufactured and tested, and then compared against virgin clay bricks without HEP content. The effect of directional orientation of bricks baked with varying HEP content on acoustic properties were experimented and discussed. The sound transmission loss decreases with increase in HEP waste due to formation of independently closed directional pores. The transmission loss of horizontally baked during firing of bricks is nearly 5dB lower than vertically baked bricks. Results of the experimental studies indicate that HEP waste can be utilised in fired clay bricks and different orientation baking further enhances the acoustic properties.

Effects of phase change material (PCM)-based nanocomposite additives on thermal decomposition and burning characteristic of high energy propellants containing RDX

A kind of phase change material (PCM)-based nanocomposite was prepared and added into high energy propellants containing RDX as additives to investigate its effect on thermal decomposition and burning characteristic of high energy propellants. The effect of PCM-based nanocomposites on thermal decomposition of high energy propellants is investigated by TG/DSC-FTIR-MS technology. Due to the delayed protection effect (PCM-based nanocomposites can absorb lots of heat at the range of certain temperature when it undergoes structure change or phase transitions) of PCM-based nanocomposites under the thermal decomposition condition, the thermal stability of high energy propellants modified with PCM-based nanocomposites is improved. At the same time, the concentration of N2, NO2, H2O and CO2 is increased during thermal decomposition of high energy propellants whereas NO and CO is decreased. The burning gaseous products and burning characteristic of high energy propellants are studied by the combination of closed bomb test and Fourier transform infrared spectrum. The main burning gaseous products are N2, CO2, CO, H2O, CH4, etc. After the high energy propellant modified with PCM-based nanocomposites, the concentration of CH4 is increased while CO, CO2 and H2O is decreased under the high-pressure burning condition. The progressivity factor of high energy propellants is increased by 22.2% compared with the control sample while the maximum pressure is merely decreased 1.25% after the addition of the PCM-based nanocomposite, thus PCM-based nanocomposites can be used to adjust the burning process and improve the burning progressivity of high energy propellants. This study is expected to boost the practical application of PCM-based nanocomposite to the propellant formulation and effectively control the burning characteristic of high energy propellants.

Study on High Energy Propellant Waste in the Processing of Fired Clay Bricks

Utilisation of propellant waste in fabrication of bricks is not only used as efficient waste disposal method but also to get better functional properties. In the present study, high energy propellant (HEP) waste additive mixed with soil and fly ash in different proportions during manufacturing of bricks has been investigated experimentally. X-ray diffraction (XRD) studies were carried out to confirm the brick formation and the effect of HEP waste. Ceramic bricks were fabricated with HEP waste additive in proper proportions i.e. 0.5 wt %, 1.0 wt %, 1.5 wt %, 2.0 wt %, 2.5 wt %, 3 wt %, 3.5 wt %, and 4 wt % and then evaluated for water absorption capability and compressive strength. Compressive strength of 6.7 N/mm2, and Water absorption of 22 % have been observed from modified fired bricks impregnated with HEM waste additive. Scanning electron microscopy (SEM) studies were carried out to analyze the effect of HEP waste additive on pore formation and distribution in the bricks. Further, the heat resulting from decomposition of propellants can cause a decrease in the energy required of baking process. The process of manufacturing of bricks with HEP waste additive is first of its kind till date.

Textural analysis of aluminum hydride

The textural properties of aluminum hydride (alane, AlH3) prepared by wet synthesis from lithium aluminum hydride (LiAlH4) and aluminum chloride (AlCl3) were closely investigated with a focus on the effect of reactant ratios on crystal formation. XRD analysis showed that three crystals were almost similar, α-type AlH3, despite the different external morphology. TEM observations also demonstrated their similarity in chemical structures with an average lattice distance between atoms of 1.16Å. Slight differences in thermal decomposition and hydrogen content of each crystalline alane would be due to morphological difference and a little amount of impurities or by-products. When the ratio of reactants (LiAlH4 and AlCl3) was 3:1, a more evident cubic form which is desirable for the use of high energy propellants could be obtained, and the crystal size was 10–20μm.

Preparation, Thermal and Sensitivity Properties of Nano‐Sized Spherical Nitrocellulose Composite Crystal

AbstractThe sensitivity study of propellants has been the concern of many researchers, and many achievements have been gained in this field. Nitrocellulose was replaced by some energetic thermoplastic elastomers to prepare insensitive high energy propellants, which is an effective method for reducing the sensitivity of propellants. However, the propellants based on these binders still have some defects. Preparation and application of insensitive nitrocellulose may overcome these drawbacks and becomes a potential candidate to be used as an ingredient of insensitive high energy propellants without energetic thermoplastic elastomers. To reduce the sensitivity of nitrocellulose, a nano‐sized spherical nitrocellulose composite crystal was prepared by pretreatment, degradation and nitration of microcrystalline cellulose. The products were characterized by TEM, FT‐IR, XRD, XPS, elemental analysis, TGA, DSC and sensitivity tests. Results show that the prepared nano‐sized cellulose is spherical with a diameter in the range of 15–30 nm and displays a composite crystal with two kinds of crystalline structure. The nano‐sized spherical nitrocellulose composite crystal has a higher crystallinity and nitrogen content and less impact sensitivity in comparison with the common nitrocellulose. The improvement of crystal quality of nitrocellulose using composite crystal method is beneficial for reducing the impact sensitivity of nitrocellulose.

RDX Based Enhanced Energy Propellant for Tank Gun Ammunition

AbstractAmmunition designers are faced now a day with the tasks of improving muzzle velocity (MV) to achieve required penetration as well as developing gun propellant with minimum variation of ballistics at extremes of temperatures so as to maintain safe chamber pressure of gun. In order to meet the requirement an optimized propellant composition containing RDX, energetic plasticizer, nitrocellulose (NC), cellulose acetate (CA) and additives referred as Enhanced Energy Propellant (EEP) was processed and evaluated theoretically and experimentally. Performance in respect of ballistic parameters (static and dynamic), sensitivity, thermal characteristics, thermal stability and mechanical properties were evaluated and compared with that of the conventional triple base propellant (TBP). Experimental data on comparative study indicated that the newly developed EEP is superior to existing TBP in terms of energy, stability and thermal properties while sustaining the safe chamber pressure of gun. Dynamic firing results show that, EEP requires lower charge mass (7.43 kg) and lesser chamber pressure (459 MPa) to realize MV at par with standard. This illustrates high energy of EEP.

Investigation Aging Behavior of High Energy Propellant Materials

NEPE propellants were exposed to aging at 55°C, 65°C, 70°C, and 75°C, respectively. The relative contents of stabilizer (MNA), tensile strength and are measured to analysis the aging characteristic of NEPE propellants. Based on aging mechanism of the stabilization depletion and the physical aging properties of NEPE propellants, the whole aging process can be separated into two processes: stabilizer gradual degradation at first stage (chemical aging stage) and degradation reaction of polymer at seconded stage. The stabilizer degradation occurred in the first process, therefore the storage life prediction at normal temperature for NEPE propellant ought to be based on the first process during high temperature aging stage. The storage life of the NEPE propellant at room temperature has been evaluated via Arrhenius and Berthelot approach.

Effect of Carbon Nanotubes on the Catalysis of Propellant Combustion

The effect of carbon nanotubes (CNTs) on the catalysis of combustion of high energy propellants was studied. Carbon nanotubes increased the burning rate of a propellant in the presence of a catalyst to a much higher extent than carbon black. The structure and composition of quenched propellant samples were studied by scanning electron microscopy and electron probe X-ray microanalysis. In the presence of CNTs, a higher carbon frame was formed virtually over the whole combustion surface and the accumulation of the catalyst particles on it was much more pronounced than in the case of carbon black. The obtained results unambiguously indicate that CNTs are more efficient in the catalyzed propellant combustion.

Thermal Analysis of a Certain Type of High Energy Propellant

In order to study the thermal decomposition characteristics of four component HTPB propellants, the thermo gravimetric analysis (TG) experiment was carried out. The TG curves of propellants at different temperatures, and the TG curves of different components of propellants at the same temperature were obtained, and the kinetic parameters at different heating rates were calculated. In general, the heat of the solid propellant was found. Decomposition is a continuous process with thermal stability and thermal safety.

Synthesis, Thermal Properties and Sensitivity of Ladder‐Like Nitrocellulose Grafted by Polyethylene Glycol

AbstractThe sensitivity study of propellants has been receiving heightened attentions from a lot of investigators. These propellants based on nitrocellulose are sensitive to accidental stimuli that result in catastrophic accidents. Thus energetic thermoplastic elastomers have been used as binders to replace some nitrocellulose to prepare insensitive high energy propellants. However, some defects are presented in the application of these binders. Based on the reason above, a novel binder named as step ladder‐like nitrocellulose was synthesized by isophorone diisocyanate reacting with free hydroxyl groups of nitrocellulose first, and then reacting with polyethylene glycol. The reaction product was characterized by FT‐IR, XRD, SEM, TGA, DSC and sensitivity tests. Results show that step ladder‐like nitrocellulose is successfully synthesized from nitrocellulose, and it has a quasi‐spherical shape and regular crystal structure. Furthermore, the thermal weight loss course of step ladder‐like nitrocellulose is relatively gentle in the range of 175–450 °C and its mechanical sensitivity is less than that of raw nitrocellulose.

Robust Microencapsulated Silicone Oil with a Hybrid Shell for Reducing Propellant Erosion

AbstractA morphologically stable silicon oil microcapsule base polystyrene as shell modified with TiO2 and Si3N4 nanoparticles was synthesized, characterized and applied as an inhibitor for high energy propellant to reduce erosion of gun barrel. The composite microcapsules were obtained by an eco‐friendly method. Embedding heat‐resistant TiO2 and Si3N4 nanoparticles in polystyrene shell enhances the reliability of polymeric shell. The anti‐erosion effect of composite microcapsules for high energy propellant was investigated by using an erosion tester. Results showed that the erosion property of high energy propellant with composite microcapsule was significantly decreased when compared to control sample (without microcapsules). It showed a decrease of 20.6 % in erosion mass when 7 wt.% of composite microcapsules were added to the high energy propellant. Moreover, the anti‐erosion efficiency of composite additives exhibited an increasing trend with the increase of their contents. The pressure and time history confirmed that the composite microcapsules also have ability to adjust the combustion performance of high energy propellants. The developed silicon oil microcapsule shows a potential application for propellant erosion additive.

Effects of an Organic‐inorganic Nanocomposite Additive on the Combustion and Erosion Performance of High Energy Propellants Containing RDX

AbstractA nanocomposite microsphere consisting of solid paraffin, nano‐TiO2, nano‐BN, zeolitic imidazolate framework‐67 particles and polymethyl methacrylate was prepared and applied as a functional additive for high energy propellants (with about 23 wt % RDX) to reduce the barrel erosion and improve its combustion performance as well. High energy propellants modified with the nanocomposite were manufactured by a solvent extrusion technique. According to the scanning electron microscope and differential scanning calorimetry results, there exists a good compatibility between the nanocomposite and propellant matrix. The energy and combustion performance as well as erosion of the modified propellants were studied by a closed bomb test and an erosion tube device, respectively. Results showed that compared with the unmodified propellant, both the erosion and energy performance of modified high energy propellant gradually decreased with the increase of nanocomposites contents. When the content of nanocomposites was 5.1 %, the erosion mass of the modified propellant reduced to 37.0 % while the propellant force only decreased 5.7 %, indicating that the nanocomposite has enormous ability to improve gun erosion resistance while barely affect energy performance of propellant. Furthermore, the closed bomb burning curves of the samples showed that addition of nanocomposites to propellant matrix could prolong the combustion time, efficiently inhibit the initial generation rate of combustion gas, and further achieve the progressive burning of the propellants.

Nitrato Functionalized Polymers for High Energy Propellants and Explosives: Recent Advances

Future propellants and explosive research focus on developing compositions with less vulnerability without compromising performance. This has provided impetus for research in the area of high energy materials and compounds free from pollution, for safe handling, high performance, reliability and reproducibility. The energetic oxidizers and energetic binders are being developed in this scenario for use in composite propellants and explosives. In a propellant, the binder holds together the matrix containing solid oxidizer particles and finely divided metal particles. It provides structural integrity and aid the combustion of the propellant. Any new development in this area wherein the binder can contribute to the energetic is of immense importance. This can be achieved by incorporation of energetic groups such as nitrato (−ONO2), azide (−N3) or flurodinitro CF(NO2)2 as side chain or on to the existing polymer backbone. Among these, nitrato functionalized energetic binders can find application in myriad areas like boosters, plastic bonded explosives, gas generators and pyrogen igniters. The present article is a concise review on various types of nitrato binders; their synthesis, properties and their propellant studies. Copyright © 2017 John Wiley & Sons, Ltd.