Combustion within small motors is key in the application-specific development of nanothermite-based micro-energetic systems. This study evaluates the performance of nanothermite mixtures in a converging-diverging nozz...Combustion within small motors is key in the application-specific development of nanothermite-based micro-energetic systems. This study evaluates the performance of nanothermite mixtures in a converging-diverging nozzle and an open tube. Mixtures were prepared using nano-aluminum(n-Al),potassium perchlorate(KClO_(4)), and different carbon nanomaterials(CNMs) including graphene-oxide(GO), reduced GO, carbon nanotubes(CNTs) and nanofibers(CNFs). The mixtures were packed at different densities and ignited by laser beam. Performance was measured using thrust measurement,high-speed imaging, and computational fluid dynamics modeling, respectively. Thrust, specific impulse(ISP), volumetric impulse(ISV), as well as normalized energy were found to increase notably with CNM content. Two distinctive reaction regimes(fast and slow) were observed in combustion of low and high packing densities(20% and 55%TMD), respectively. Total impulse(IFT) and ISPwere maximized in the 5%GO/Al/KClO_4 mixture, producing 7.95 m N·s and 135.20 s respectively at 20%TMD, an improvement of 57%compared to a GO-free sample(5.05 m N·s and 85.88 s). CFD analysis of the motors over predicts the thrust generated but trends in nozzle layout and packing density agree with those observed experimentally;peak force was maximized by reducing packing density and using an open tube. The numerical force profiles fit better for the nozzle cases than the open tube scenarios due to the rapid nature of combustion. This study reveals the potential of GO in improving oxygenated salt-based nanothermites,and further demonstrates their applicability for micro-propulsion and micro-energetic applications.展开更多
Experimental investigation has been carried out for laser ignition and combustion of nanothermites based on aluminum and oxides of copper,bismuth and molybdenum.Ultrasonic mixing of nanosized powders was used to produ...Experimental investigation has been carried out for laser ignition and combustion of nanothermites based on aluminum and oxides of copper,bismuth and molybdenum.Ultrasonic mixing of nanosized powders was used to produce compositions.For thermite ignition,initiating laser pulse with a maximum intensity of 770 W/cm2 was generated by a laser diode with a wavelength of 808 nm.The ignition delay times,the minimum initiation energy density,and the average burning rate at various thermite densities and mass fractions of components were determined by recording the emission of radiation of the reaction products using a multichannel pyrometer jointly with a high-speed video camera.The effect of adding carbon black on the threshold parameters of a laser pulse was also studied.Based on the obtained results,certain assumptions were put forward with regard to the mechanism of nanothermites’ignition by laser radiation and their burning.In particular,the assumptions were made on the two-stage process of the reaction initiation and jet burning mechanism of porous nanothermites.展开更多
A sol-gel synthetic approach combined with an ultrasonic method was utilized to prepare Al/B/Fe2O3 nanothermites.The structure and properties of the prepared nanothermites were characterized by thermogravimetric analy...A sol-gel synthetic approach combined with an ultrasonic method was utilized to prepare Al/B/Fe2O3 nanothermites.The structure and properties of the prepared nanothermites were characterized by thermogravimetric analysis,differential scanning calorimetry,scanning electron microscopy,X-ray diffraction,and an impact sensitivity test.The results verified that the nano-aluminum and the micro-boron were uniformly dispersed in the pores of the iron oxide gel.The heat of the prepared Al/B/Fe2O3 nanothermites was 1.3 times that of the simple physically mixed sample.In addition,the heat of the combustion test showed that these materials were indeed energetic.Small-scale safe experiments also showed that the prepared materials through sol-gel were relatively insensitive to standard impact.展开更多
A new nanothermite system,composed of titanium and tungsten trioxide is reported.Initial investigations show that it has low-average sensitivity to mechanical stimuli(friction,impact),but that its sensitivity to laser...A new nanothermite system,composed of titanium and tungsten trioxide is reported.Initial investigations show that it has low-average sensitivity to mechanical stimuli(friction,impact),but that its sensitivity to laser irradiation can be controlled in a moderately wide range.The combustion of this nanothermite system takes place at a very high apparent temperature(>3695 K)and it follows the key predictions of the established reactive sintering mechanism,as supported by SEM-EDS and XRD analyses.展开更多
The safety and reliability of weapon systems would be significantly affected by changes in the performance of energetic materials due to ambient temperature and humidity.Nanothermites have promising applications due t...The safety and reliability of weapon systems would be significantly affected by changes in the performance of energetic materials due to ambient temperature and humidity.Nanothermites have promising applications due to their excellent reactivity.Therefore it becomes extremely important to understand their aging and failure process in the environment before using them.Here,the aging and failure process of Al/CuO in 71°C/60%RH were investigated,and showed that CuO nanoparticles negatively catalyze Al nanopowders,resulting in rapid hydration.The anti-aging effect of FAS-17-coated Al nanopowder was also examined.The aging process of Al,Al/CuO,and Al@FAS-17/CuO in high humidity and heat environment were revealed by quasi-in situ SEM and TEM methods.Compared with the aging of pure Al,the Al nanopowder in the nanothermites strongly agglomerated with the CuO nanopowder and hydrated earlier.This may be caused by CuO catalyzed hydration of Al nanopowder.The energy release experiments showed that the performance of Al/CuO decreased rapidly and failed to ignite after 4 h of aging.In contrast,the Al@FAS-17/CuO thermite can achieve long-term stability of up to 60 h in the same environment by simple cladding of FAS-17.It is found that FAS-17 coated Al nanopowder can prevent both particle agglomeration and water erosion,which is an effective means to make nanothermites application in high humidity and heat environment.展开更多
The core-shell metastable intermolecular composites(MIC)have attracted much attention in the past few years due to their unique properties.Here,the preparation of Al-Core heterojunction fibers using PVP as a template ...The core-shell metastable intermolecular composites(MIC)have attracted much attention in the past few years due to their unique properties.Here,the preparation of Al-Core heterojunction fibers using PVP as a template is proposed.The nano-Al was directly added to the precursor solution of cupric acetate monohydrate(CAM)/Polyvinylpyrrolidone(PVP),and the initial Al@CAM/PVP fibers were obtained via electrospinning.The core-shell MIC fibers are then obtained by calcining the initial fibers.The morphology,structure,and composition of Al-core MIC fibers were characterized,that the energetic fibers calcined at 300℃,350℃,and 400℃have a core-shell structure with shell compositions CuxO and PVP,CuxO and Cu O,respectively.The energy release characteristics of Al-core MIC were investigated,and preliminary ignition tests were performed using an ignition temperature measuring instrument and a pulsed laser.The energetic fibers calcined at 300℃exhibited unique properties.The decomposition of PVP in the shell layer promoted exotherm,and a low-temperature exothermic peak was shown at 372-458℃.Lower ignition temperatures and higher flame heights were observed in the combustion tests than calcination at 350℃and 400℃.An unexpected result was that PVP can play a positive role in Al/CuO nanothermites.Simultaneously,this preparation method provided an idea for the integrated preparation of core-shell Al-Core MIC fibers and tuning the properties of MIC.展开更多
The storage stability of energetic materials is important for its application. Here, the storage stability of Al/CuO nanothermite, which was prepared by electrospray method and stored with different storage time, was ...The storage stability of energetic materials is important for its application. Here, the storage stability of Al/CuO nanothermite, which was prepared by electrospray method and stored with different storage time, was systematically researched. The activation energy of Al/CuO nanothermite was calculated by differential scanning calorimetry(DSC). The ignition temperature and the curve pressure history of Al/Cu O nanothermite was measured using ignition temperature measuring device and constant-volume pressurization tests, respectively. Further, the thermites were characterized by X-ray Diffractometer(XRD), X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM) and Transmission electron microscopy(TEM). The results show that the morphology of the thermites did not change significantly. The activation energy was decreased from 254.1 k J/mol to 181.8 k J/mol after storage for 13 months. When stored for 0, 7 and 13 months, the peak pressures of Al/CuO nanothermite were 685.8 k Pa,626.3 k Pa and 625.5 k Pa, respectively. In addition to the ignition temperature, it was 775 ℃, 739 ℃ and754 ℃, respectively. This result indicated that the ignition and combustion properties of Al/CuO nanothermite are obviously reduced when stored for a long time, at room temperature.展开更多
Nanothermites (metal oxide/metal) can offer tremendously exothermic self sustained reactions. CuO is one of the most effective oxidizers for naonothermite applications. This study reports on two prospectives for the m...Nanothermites (metal oxide/metal) can offer tremendously exothermic self sustained reactions. CuO is one of the most effective oxidizers for naonothermite applications. This study reports on two prospectives for the manufacture of CuO nanoparticles. Colloidal CuO particles of 15 nm particle size were developed using hydrothermal synthesis technique. Multiwalled carbon nanotubes (MWCNTs) with surface are 700m2/g was employed as a substrate for synthesis of CuO-coated MWCNTs using electroless plating. On the other hand, aluminium particles with combustion heat of 32000 J/g is of interest as high energy density material. The impact of stoichiometric nanothermite particles (CuO/Al & Cuo-coated MWCNTs/Al) on shock wave strength of Al/TNT nanocomposite was evaluated using ballistic mortar test. While CuO-coated MWCNTs decreased the shock wave strength by 15%;colloidal CuO enhanced the shock wave strength by 30%. The superior performance of colloidal CuO particles was correlated to their steric stabilization with employed organic solvent. This is the first time ever to report on fabrication, isolation, and integration of stablilized colloidal nanothermite particles into energetic matrix where intimate mixing between oxidizer and metal fuel could be achieved.展开更多
Nanothermites have been employed as fuel additives in energetic formulations due to their higher energy density over CHNO energetics. Nevertheless, sintering and degradation of nanoparticles significantly limit the pr...Nanothermites have been employed as fuel additives in energetic formulations due to their higher energy density over CHNO energetics. Nevertheless, sintering and degradation of nanoparticles significantly limit the practical use of nanothermites. In this work, combustion characteristic and aging behavior of aluminum/iron oxide(Al/Fe2O3) nanothermite mixtures were investigated in the presence of micron-scale nickel aimed to produce bimetal thermite powders. The results showed that the alumina content in the combustion residue increased from 88.3% for Al/Fe2O3 nanothermite to 96.5% for the nanothermite mixture containing 20 wt% nickel. Finer particle sizes of combustion residue were obtained for the nanothermite mixtures containing nickel, indicative of the reduced agglomeration. Both results suggested a more complete combustion in the bimetal thermite powders. Aging behavior of the nanothermite mixture was also assessed by measuring the heat of combustion of the mixture before and after aging process. The reduction in heat of combustion of nanothermite mixtures containing nickel was less severe as compared to a significant decrease for the nanothermite mixture without nickel, indicating better aging resistance of the bimetal thermite powders.展开更多
In this study,AleCuO nanocomposites were fabricated by sol-gel method.As a contrast,the thermite was prepared by physical mixing at the equivalence ratio of 0.5,1,2,respectively.The intermediates and samples as prepar...In this study,AleCuO nanocomposites were fabricated by sol-gel method.As a contrast,the thermite was prepared by physical mixing at the equivalence ratio of 0.5,1,2,respectively.The intermediates and samples as prepared were characterized by SEM and XRD.The exothermic properties of the two samples prepared at different equivalence ratios were tested and the reaction products were characterized by XRD.The SEM results show that the sample prepared by the sol-gel method demonstrates a micron-sized agglomerated sphere formed by a mutual wrapping of Al NPs and CuO NPs,and the particles are evenly distributed in the agglomerate.In addition,when the content of Al powder is seriously insufficient,the heat release of the sample prepared by physical mixing is 1.6 times that of by sol-gel method.With the increase of Al powder content,the exothermic properties of Al/CuO NPs prepared by sol-gel method began to increase significantly compared with physical mixing and the difference is 1.5 times when the equivalence ratio increases to 2.It can be concluded that the reason for this result may be attributed to the different mass transfer modes of components due to the different morphologies of samples.展开更多
Fluoropolymers get increasing attention in energetic materials application due to the high fluorine content.To explore the effect of poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF-HFP))on Al/MnO_(2) nanothermi...Fluoropolymers get increasing attention in energetic materials application due to the high fluorine content.To explore the effect of poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF-HFP))on Al/MnO_(2) nanothermite,the samples with different contents are prepared and characterized by SEM,TGDSC,XRD,and their ignition and combustion behavior are tested and recorded.The results show that P(VDF-HFP)as an energetic binder can combine the nanothermite components together,even exist in the gaps.The integrity of energetic materials has been improved.Thermal analysis shows that the addition of P(VDF-HFP)greatly changes the thermal reaction processes,and the exothermic peaks appear early,but the utilization of fuel and oxidizer is not efficient from the XRD results.Furthermore,the appropriate addition of P(VDF-HFP)can directly reduce the ignition energy threshold and increase the combustion time,which is necessary for the potential ignition charge application.The possible reasons for above phenomena are discussed and analyzed.This research provides a reference for improvement of thermitebased ignition charge formulation.展开更多
Additive manufacturing(AM),also called three-dimensional(3D)printing,has been developed to obtain energetic materials within the past decade.3D printing represents a family of flexible manufacturing techniques that en...Additive manufacturing(AM),also called three-dimensional(3D)printing,has been developed to obtain energetic materials within the past decade.3D printing represents a family of flexible manufacturing techniques that enable fast and accurate fabrication of structures with complex 3D features and a broad range of sizes,from submicrometer to several meters.Various methods have already been explored,including templating,melting extrusion,inkjet printing and electrospray methods.It was demonstrated that the structure achieved by AM could be used to manipulate the reactivity of energetic or reactive materials by changing the flow of gases and entrained particles via architecture.By employing different AM techniques,energetic materials with controllable nanostructures and uniformly dispersed ingredients can be prepared.It is exciting to tailor the energy release without defaulting to change the formulation of the conventional method.The combustion and mechanical properties of conventional energetic materials can be retained at the same time.In this review,the preparation and characterization of AM energetic materials that have been developed in the last decade are summarized.Various AM techniques used in the fabrication of energetic materials are compared and discussed.In particular,formulations of energetic materials applied in AM,metallic fuels,binders and energetic fillers and their advantages in terms of combustion efficiency and other properties are proposed.展开更多
基金financial funding from the Egyptian governmentthe financial funding from the NSERC Discovery grant。
文摘Combustion within small motors is key in the application-specific development of nanothermite-based micro-energetic systems. This study evaluates the performance of nanothermite mixtures in a converging-diverging nozzle and an open tube. Mixtures were prepared using nano-aluminum(n-Al),potassium perchlorate(KClO_(4)), and different carbon nanomaterials(CNMs) including graphene-oxide(GO), reduced GO, carbon nanotubes(CNTs) and nanofibers(CNFs). The mixtures were packed at different densities and ignited by laser beam. Performance was measured using thrust measurement,high-speed imaging, and computational fluid dynamics modeling, respectively. Thrust, specific impulse(ISP), volumetric impulse(ISV), as well as normalized energy were found to increase notably with CNM content. Two distinctive reaction regimes(fast and slow) were observed in combustion of low and high packing densities(20% and 55%TMD), respectively. Total impulse(IFT) and ISPwere maximized in the 5%GO/Al/KClO_4 mixture, producing 7.95 m N·s and 135.20 s respectively at 20%TMD, an improvement of 57%compared to a GO-free sample(5.05 m N·s and 85.88 s). CFD analysis of the motors over predicts the thrust generated but trends in nozzle layout and packing density agree with those observed experimentally;peak force was maximized by reducing packing density and using an open tube. The numerical force profiles fit better for the nozzle cases than the open tube scenarios due to the rapid nature of combustion. This study reveals the potential of GO in improving oxygenated salt-based nanothermites,and further demonstrates their applicability for micro-propulsion and micro-energetic applications.
基金supported by a grant for large scientific projects in priority areas of scientific and technological development No.13.1902.21.0035carried out at Federal Research Center for Chemical Physics,Russian Academy of Sciences(FRC CP RAS),Russian Academy of Sciences(RAS)financially supported by subsidies for the implementation of the state assignment on the topic No.0082-2019-0016。
文摘Experimental investigation has been carried out for laser ignition and combustion of nanothermites based on aluminum and oxides of copper,bismuth and molybdenum.Ultrasonic mixing of nanosized powders was used to produce compositions.For thermite ignition,initiating laser pulse with a maximum intensity of 770 W/cm2 was generated by a laser diode with a wavelength of 808 nm.The ignition delay times,the minimum initiation energy density,and the average burning rate at various thermite densities and mass fractions of components were determined by recording the emission of radiation of the reaction products using a multichannel pyrometer jointly with a high-speed video camera.The effect of adding carbon black on the threshold parameters of a laser pulse was also studied.Based on the obtained results,certain assumptions were put forward with regard to the mechanism of nanothermites’ignition by laser radiation and their burning.In particular,the assumptions were made on the two-stage process of the reaction initiation and jet burning mechanism of porous nanothermites.
文摘A sol-gel synthetic approach combined with an ultrasonic method was utilized to prepare Al/B/Fe2O3 nanothermites.The structure and properties of the prepared nanothermites were characterized by thermogravimetric analysis,differential scanning calorimetry,scanning electron microscopy,X-ray diffraction,and an impact sensitivity test.The results verified that the nano-aluminum and the micro-boron were uniformly dispersed in the pores of the iron oxide gel.The heat of the prepared Al/B/Fe2O3 nanothermites was 1.3 times that of the simple physically mixed sample.In addition,the heat of the combustion test showed that these materials were indeed energetic.Small-scale safe experiments also showed that the prepared materials through sol-gel were relatively insensitive to standard impact.
基金the scientific and innovative merit Grant No.04/040/RGJ24/0275 of the Rector of the Silesian University of Technologythe scientific and innovative merit grant no.04/040/RGJ24/0278 of the Rector of the Silesian University of Technologythe support of the MERA.NET 3 Room temperature hydrogen sensors based on polycarbazole and its derivatives,"Hydro Sens"project(Grant No.9150,M-ERA.NET3/2021/93/HYDROSENS/2022。
文摘A new nanothermite system,composed of titanium and tungsten trioxide is reported.Initial investigations show that it has low-average sensitivity to mechanical stimuli(friction,impact),but that its sensitivity to laser irradiation can be controlled in a moderately wide range.The combustion of this nanothermite system takes place at a very high apparent temperature(>3695 K)and it follows the key predictions of the established reactive sintering mechanism,as supported by SEM-EDS and XRD analyses.
基金supported by the National Natural Science Foundation of China(Grant No.22275092)。
文摘The safety and reliability of weapon systems would be significantly affected by changes in the performance of energetic materials due to ambient temperature and humidity.Nanothermites have promising applications due to their excellent reactivity.Therefore it becomes extremely important to understand their aging and failure process in the environment before using them.Here,the aging and failure process of Al/CuO in 71°C/60%RH were investigated,and showed that CuO nanoparticles negatively catalyze Al nanopowders,resulting in rapid hydration.The anti-aging effect of FAS-17-coated Al nanopowder was also examined.The aging process of Al,Al/CuO,and Al@FAS-17/CuO in high humidity and heat environment were revealed by quasi-in situ SEM and TEM methods.Compared with the aging of pure Al,the Al nanopowder in the nanothermites strongly agglomerated with the CuO nanopowder and hydrated earlier.This may be caused by CuO catalyzed hydration of Al nanopowder.The energy release experiments showed that the performance of Al/CuO decreased rapidly and failed to ignite after 4 h of aging.In contrast,the Al@FAS-17/CuO thermite can achieve long-term stability of up to 60 h in the same environment by simple cladding of FAS-17.It is found that FAS-17 coated Al nanopowder can prevent both particle agglomeration and water erosion,which is an effective means to make nanothermites application in high humidity and heat environment.
文摘The core-shell metastable intermolecular composites(MIC)have attracted much attention in the past few years due to their unique properties.Here,the preparation of Al-Core heterojunction fibers using PVP as a template is proposed.The nano-Al was directly added to the precursor solution of cupric acetate monohydrate(CAM)/Polyvinylpyrrolidone(PVP),and the initial Al@CAM/PVP fibers were obtained via electrospinning.The core-shell MIC fibers are then obtained by calcining the initial fibers.The morphology,structure,and composition of Al-core MIC fibers were characterized,that the energetic fibers calcined at 300℃,350℃,and 400℃have a core-shell structure with shell compositions CuxO and PVP,CuxO and Cu O,respectively.The energy release characteristics of Al-core MIC were investigated,and preliminary ignition tests were performed using an ignition temperature measuring instrument and a pulsed laser.The energetic fibers calcined at 300℃exhibited unique properties.The decomposition of PVP in the shell layer promoted exotherm,and a low-temperature exothermic peak was shown at 372-458℃.Lower ignition temperatures and higher flame heights were observed in the combustion tests than calcination at 350℃and 400℃.An unexpected result was that PVP can play a positive role in Al/CuO nanothermites.Simultaneously,this preparation method provided an idea for the integrated preparation of core-shell Al-Core MIC fibers and tuning the properties of MIC.
文摘The storage stability of energetic materials is important for its application. Here, the storage stability of Al/CuO nanothermite, which was prepared by electrospray method and stored with different storage time, was systematically researched. The activation energy of Al/CuO nanothermite was calculated by differential scanning calorimetry(DSC). The ignition temperature and the curve pressure history of Al/Cu O nanothermite was measured using ignition temperature measuring device and constant-volume pressurization tests, respectively. Further, the thermites were characterized by X-ray Diffractometer(XRD), X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM) and Transmission electron microscopy(TEM). The results show that the morphology of the thermites did not change significantly. The activation energy was decreased from 254.1 k J/mol to 181.8 k J/mol after storage for 13 months. When stored for 0, 7 and 13 months, the peak pressures of Al/CuO nanothermite were 685.8 k Pa,626.3 k Pa and 625.5 k Pa, respectively. In addition to the ignition temperature, it was 775 ℃, 739 ℃ and754 ℃, respectively. This result indicated that the ignition and combustion properties of Al/CuO nanothermite are obviously reduced when stored for a long time, at room temperature.
文摘Nanothermites (metal oxide/metal) can offer tremendously exothermic self sustained reactions. CuO is one of the most effective oxidizers for naonothermite applications. This study reports on two prospectives for the manufacture of CuO nanoparticles. Colloidal CuO particles of 15 nm particle size were developed using hydrothermal synthesis technique. Multiwalled carbon nanotubes (MWCNTs) with surface are 700m2/g was employed as a substrate for synthesis of CuO-coated MWCNTs using electroless plating. On the other hand, aluminium particles with combustion heat of 32000 J/g is of interest as high energy density material. The impact of stoichiometric nanothermite particles (CuO/Al & Cuo-coated MWCNTs/Al) on shock wave strength of Al/TNT nanocomposite was evaluated using ballistic mortar test. While CuO-coated MWCNTs decreased the shock wave strength by 15%;colloidal CuO enhanced the shock wave strength by 30%. The superior performance of colloidal CuO particles was correlated to their steric stabilization with employed organic solvent. This is the first time ever to report on fabrication, isolation, and integration of stablilized colloidal nanothermite particles into energetic matrix where intimate mixing between oxidizer and metal fuel could be achieved.
文摘Nanothermites have been employed as fuel additives in energetic formulations due to their higher energy density over CHNO energetics. Nevertheless, sintering and degradation of nanoparticles significantly limit the practical use of nanothermites. In this work, combustion characteristic and aging behavior of aluminum/iron oxide(Al/Fe2O3) nanothermite mixtures were investigated in the presence of micron-scale nickel aimed to produce bimetal thermite powders. The results showed that the alumina content in the combustion residue increased from 88.3% for Al/Fe2O3 nanothermite to 96.5% for the nanothermite mixture containing 20 wt% nickel. Finer particle sizes of combustion residue were obtained for the nanothermite mixtures containing nickel, indicative of the reduced agglomeration. Both results suggested a more complete combustion in the bimetal thermite powders. Aging behavior of the nanothermite mixture was also assessed by measuring the heat of combustion of the mixture before and after aging process. The reduction in heat of combustion of nanothermite mixtures containing nickel was less severe as compared to a significant decrease for the nanothermite mixture without nickel, indicating better aging resistance of the bimetal thermite powders.
文摘In this study,AleCuO nanocomposites were fabricated by sol-gel method.As a contrast,the thermite was prepared by physical mixing at the equivalence ratio of 0.5,1,2,respectively.The intermediates and samples as prepared were characterized by SEM and XRD.The exothermic properties of the two samples prepared at different equivalence ratios were tested and the reaction products were characterized by XRD.The SEM results show that the sample prepared by the sol-gel method demonstrates a micron-sized agglomerated sphere formed by a mutual wrapping of Al NPs and CuO NPs,and the particles are evenly distributed in the agglomerate.In addition,when the content of Al powder is seriously insufficient,the heat release of the sample prepared by physical mixing is 1.6 times that of by sol-gel method.With the increase of Al powder content,the exothermic properties of Al/CuO NPs prepared by sol-gel method began to increase significantly compared with physical mixing and the difference is 1.5 times when the equivalence ratio increases to 2.It can be concluded that the reason for this result may be attributed to the different mass transfer modes of components due to the different morphologies of samples.
基金This work was supported by the National Natural Science Foundation,project no.51704302was also supported by China Scholarship Council,no.201903170086.
文摘Fluoropolymers get increasing attention in energetic materials application due to the high fluorine content.To explore the effect of poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF-HFP))on Al/MnO_(2) nanothermite,the samples with different contents are prepared and characterized by SEM,TGDSC,XRD,and their ignition and combustion behavior are tested and recorded.The results show that P(VDF-HFP)as an energetic binder can combine the nanothermite components together,even exist in the gaps.The integrity of energetic materials has been improved.Thermal analysis shows that the addition of P(VDF-HFP)greatly changes the thermal reaction processes,and the exothermic peaks appear early,but the utilization of fuel and oxidizer is not efficient from the XRD results.Furthermore,the appropriate addition of P(VDF-HFP)can directly reduce the ignition energy threshold and increase the combustion time,which is necessary for the potential ignition charge application.The possible reasons for above phenomena are discussed and analyzed.This research provides a reference for improvement of thermitebased ignition charge formulation.
基金the National Natural Science Foundation of China(Nos.21875020 and 22075024)。
文摘Additive manufacturing(AM),also called three-dimensional(3D)printing,has been developed to obtain energetic materials within the past decade.3D printing represents a family of flexible manufacturing techniques that enable fast and accurate fabrication of structures with complex 3D features and a broad range of sizes,from submicrometer to several meters.Various methods have already been explored,including templating,melting extrusion,inkjet printing and electrospray methods.It was demonstrated that the structure achieved by AM could be used to manipulate the reactivity of energetic or reactive materials by changing the flow of gases and entrained particles via architecture.By employing different AM techniques,energetic materials with controllable nanostructures and uniformly dispersed ingredients can be prepared.It is exciting to tailor the energy release without defaulting to change the formulation of the conventional method.The combustion and mechanical properties of conventional energetic materials can be retained at the same time.In this review,the preparation and characterization of AM energetic materials that have been developed in the last decade are summarized.Various AM techniques used in the fabrication of energetic materials are compared and discussed.In particular,formulations of energetic materials applied in AM,metallic fuels,binders and energetic fillers and their advantages in terms of combustion efficiency and other properties are proposed.
