A facile and economical approach was developed for the large-scale production of powdered core-shell structured PTFE/Al (CS-PA) energetic materials through ultrasonic-assisted mixing. The low-cost micrometer-sized PTF...A facile and economical approach was developed for the large-scale production of powdered core-shell structured PTFE/Al (CS-PA) energetic materials through ultrasonic-assisted mixing. The low-cost micrometer-sized PTFE and Al particles were used as starting materials. Under high-power ultrasonic waves, the PTFE powder was dispersed into nano-to sub-micrometer-sized particles and then encapsulated the Al microparticles to form the core-shell structure. The heat of combustion, burning rate, and pressurization rate of the powdered CS-PA were measured. The thermal-initiated reaction behavior was further evaluated using thermogravimetry-differential scanning calorimetry. Subsequently, the bulk CS-PA with a uniform microstructure was obtained via cold isostatic pressing of the powdered CS-PA followed by vacuum sintering. For the bulk CS-PA, the quasi-static compression behavior was characterized, and the impact-initiated reaction processes were conducted using the Split Hopkinson Pressure Bar (SHPB) and evaluated by a high-speed camera. Compared to physically mixed PTFE/Al materials, the powdered and bulk CS-PA demonstrated enhanced thermal- and impact-initiated reaction characteristics respectively, proving the effectiveness of our approach for constructing core-shell structures.展开更多
Titanium hydride(TiH_(2)), a promising high-energy additive, is doped into PTFE/Al to optimize the energy output structure of the reactive jet and strive for better aftereffect damage ability to the target. Six types ...Titanium hydride(TiH_(2)), a promising high-energy additive, is doped into PTFE/Al to optimize the energy output structure of the reactive jet and strive for better aftereffect damage ability to the target. Six types of PTFE/Al/TiH_(2) reactive liners with different TiH_(2) content are prepared by the molding and sintering method. The energy release characteristics of PTFE/Al/TiH_(2) reactive jet are tested by the transient explosion energy test, and are characterized from pressure and temperature. The reaction delay time,pressure history, and temperature history of the energy release process are obtained, then the actual value of released energy and reaction efficiency of the reactive jet are calculated. The results show that the peak pressure and temperature of the PTFE/Al/TiH_(2) jet initially increase and then decrease with increasing TiH_(2) content. When the TiH_(2) content is 10%, the actual value of released energy and reaction efficiency increased by 24% and 6.4%, respectively, compared to the PTFE/Al jet. The reaction duration of the reactive material is significantly prolonged as the TiH_(2) content increased from 0% to 30%. Finally,combined with the energy release behaviors of PAT material and the dynamic deformation process of liner, the enhancement mechanism of TiH_(2) on energy release of the reactive jet is expounded.展开更多
In this paper,the ballistic impact experiments,including impact test chamber and impact double-spaced plates,were conducted to study the reaction behaviors of a novel functionally graded reactive material(FGRM),which ...In this paper,the ballistic impact experiments,including impact test chamber and impact double-spaced plates,were conducted to study the reaction behaviors of a novel functionally graded reactive material(FGRM),which was composed of polytetrafluoroethylene/aluminum(PTFE/Al)and PTFE/Al/bismuth trioxide(Bi_(2)O_(3)).The experiments showed that the impact direction of the FGRM had a significant effect on the reaction.With the same impact velocity,when the first impact material was PTFE/Al/Bi_(2)O_(3),compared with first impact material PTFE/Al,the FGRM induced higher overpressure in the test chamber and larger damaged area of double-spaced plates.The theoretical model,which considered the shock wave generation and propagation,the effect of the shock wave on reaction efficiency,and penetration behaviors,was developed to analyze the reaction behaviors of the FGRM.The model predicted first impact material of the FGRM with a higher shock impedance was conducive to the reaction of reactive materials.The conclusion of this study provides significant information about the design and application of reactive materials.展开更多
Aluminum(Al)powder is widely applied in thermobaric explosives due to its high energy density and favorable reaction kinetics.However,the inert oxide layer(Al_(2)O_(3))on Al particles limits combustion reactivity and ...Aluminum(Al)powder is widely applied in thermobaric explosives due to its high energy density and favorable reaction kinetics.However,the inert oxide layer(Al_(2)O_(3))on Al particles limits combustion reactivity and energy efficiency.Fluoride-based surface modification has been developed as an effective approach to address this issue.Here,four classical fluoropolymers(F11,F14,PVDF,PTFE)are employed as coatings to prepare core-shell Al/Fluoropolymer.The combustion experimental results demonstrate that the core-shell Al/PTFE exhibits the highest flame propagation rate(52.88 mm·ms^(-1))and pressure output(109.02 k Pa)performance.Consequently,core-shell Al/PTFE is selected as a high-energy fuel to prepare RDX/Al/PTFE microspheres via the emulsion and solvent evaporation method,which can enhance the energy performance of RDX.The effects of the core-shell Al/PTFE ratio and RDX content on the combustion heat and pressure output are systematically investigated.The peak pressure reaches a maximum of 187.8 k Pa when the mass ratio of RDX,Al,and PTFE is 60:25:10.Additionally,RDX/Al/PTFE microspheres exhibit significantly higher laser-induced air shock velocities,detonation heat,and detonation pressure than those of pure RDX and RDX/Al.The mechanism underlying the enhanced reactivity and energetic performance is attributed to the ability of PTFE to etch the inert Al_(2)O_(3)shell on the surface of Al particles,thereby improving post-combustion reactions and significantly increasing the overall energy output of RDX explosives.This work offers a novel design strategy for high-energy structural thermobaric explosives for the practical applications.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.51571033,11804022)the Science and Technology on Transient Impact Laboratory Foundation(No.6142606183208).
文摘A facile and economical approach was developed for the large-scale production of powdered core-shell structured PTFE/Al (CS-PA) energetic materials through ultrasonic-assisted mixing. The low-cost micrometer-sized PTFE and Al particles were used as starting materials. Under high-power ultrasonic waves, the PTFE powder was dispersed into nano-to sub-micrometer-sized particles and then encapsulated the Al microparticles to form the core-shell structure. The heat of combustion, burning rate, and pressurization rate of the powdered CS-PA were measured. The thermal-initiated reaction behavior was further evaluated using thermogravimetry-differential scanning calorimetry. Subsequently, the bulk CS-PA with a uniform microstructure was obtained via cold isostatic pressing of the powdered CS-PA followed by vacuum sintering. For the bulk CS-PA, the quasi-static compression behavior was characterized, and the impact-initiated reaction processes were conducted using the Split Hopkinson Pressure Bar (SHPB) and evaluated by a high-speed camera. Compared to physically mixed PTFE/Al materials, the powdered and bulk CS-PA demonstrated enhanced thermal- and impact-initiated reaction characteristics respectively, proving the effectiveness of our approach for constructing core-shell structures.
基金National Natural Science Foundation of China (Grant No. 12002045)State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology (QNKT22-09) to provide fund for conducting experiments。
文摘Titanium hydride(TiH_(2)), a promising high-energy additive, is doped into PTFE/Al to optimize the energy output structure of the reactive jet and strive for better aftereffect damage ability to the target. Six types of PTFE/Al/TiH_(2) reactive liners with different TiH_(2) content are prepared by the molding and sintering method. The energy release characteristics of PTFE/Al/TiH_(2) reactive jet are tested by the transient explosion energy test, and are characterized from pressure and temperature. The reaction delay time,pressure history, and temperature history of the energy release process are obtained, then the actual value of released energy and reaction efficiency of the reactive jet are calculated. The results show that the peak pressure and temperature of the PTFE/Al/TiH_(2) jet initially increase and then decrease with increasing TiH_(2) content. When the TiH_(2) content is 10%, the actual value of released energy and reaction efficiency increased by 24% and 6.4%, respectively, compared to the PTFE/Al jet. The reaction duration of the reactive material is significantly prolonged as the TiH_(2) content increased from 0% to 30%. Finally,combined with the energy release behaviors of PAT material and the dynamic deformation process of liner, the enhancement mechanism of TiH_(2) on energy release of the reactive jet is expounded.
基金National Natural Science Foundation of China[grant number U1730112],China.
文摘In this paper,the ballistic impact experiments,including impact test chamber and impact double-spaced plates,were conducted to study the reaction behaviors of a novel functionally graded reactive material(FGRM),which was composed of polytetrafluoroethylene/aluminum(PTFE/Al)and PTFE/Al/bismuth trioxide(Bi_(2)O_(3)).The experiments showed that the impact direction of the FGRM had a significant effect on the reaction.With the same impact velocity,when the first impact material was PTFE/Al/Bi_(2)O_(3),compared with first impact material PTFE/Al,the FGRM induced higher overpressure in the test chamber and larger damaged area of double-spaced plates.The theoretical model,which considered the shock wave generation and propagation,the effect of the shock wave on reaction efficiency,and penetration behaviors,was developed to analyze the reaction behaviors of the FGRM.The model predicted first impact material of the FGRM with a higher shock impedance was conducive to the reaction of reactive materials.The conclusion of this study provides significant information about the design and application of reactive materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.T2222027 and 12202416)。
文摘Aluminum(Al)powder is widely applied in thermobaric explosives due to its high energy density and favorable reaction kinetics.However,the inert oxide layer(Al_(2)O_(3))on Al particles limits combustion reactivity and energy efficiency.Fluoride-based surface modification has been developed as an effective approach to address this issue.Here,four classical fluoropolymers(F11,F14,PVDF,PTFE)are employed as coatings to prepare core-shell Al/Fluoropolymer.The combustion experimental results demonstrate that the core-shell Al/PTFE exhibits the highest flame propagation rate(52.88 mm·ms^(-1))and pressure output(109.02 k Pa)performance.Consequently,core-shell Al/PTFE is selected as a high-energy fuel to prepare RDX/Al/PTFE microspheres via the emulsion and solvent evaporation method,which can enhance the energy performance of RDX.The effects of the core-shell Al/PTFE ratio and RDX content on the combustion heat and pressure output are systematically investigated.The peak pressure reaches a maximum of 187.8 k Pa when the mass ratio of RDX,Al,and PTFE is 60:25:10.Additionally,RDX/Al/PTFE microspheres exhibit significantly higher laser-induced air shock velocities,detonation heat,and detonation pressure than those of pure RDX and RDX/Al.The mechanism underlying the enhanced reactivity and energetic performance is attributed to the ability of PTFE to etch the inert Al_(2)O_(3)shell on the surface of Al particles,thereby improving post-combustion reactions and significantly increasing the overall energy output of RDX explosives.This work offers a novel design strategy for high-energy structural thermobaric explosives for the practical applications.
