As a typical energetic composite,polytetrafluoroethylene(PTFE)/aluminum(Al)has been widely applied in explosives,pyrotechnics,and propellants due to its ultra-high energy density and intense exothermic reaction.In thi...As a typical energetic composite,polytetrafluoroethylene(PTFE)/aluminum(Al)has been widely applied in explosives,pyrotechnics,and propellants due to its ultra-high energy density and intense exothermic reaction.In this work,the radial gradient(RG)structure of PTFE/Al cylinders with three different PTFE morphologies(200 nm and 5μm particles and 5μm fiber)and content changes are prepared by 3D printing technology.The effect of radial gradient structure on the pressure output of PTFE/Al has been studied.Compared with the morphology change of PTFE,the change of component content in the gradient structure has an obvious effect on the pressure output of the PTFE/Al cylinder.Furthermore,the relationships of the morphology,content of PTFE and the combustion reaction of the PTFE/Al cylinder reveal that the cylinder shows a more complex flame propagation process than others.These results could provide a strategy to improve the combustion and pressure output of PTFE/Al.展开更多
基于16 mm口径气炮撞击实验,对铝颗粒增强的聚四氟乙烯(polytetrafluoroethylene)/Al(PTFE/Al)冲击反应复合材料的冲击反应阈值开展了研究。为研究不同撞击加载条件下应变率和碰撞应力对PTFE/Al冲击诱发反应的影响,实验中采用铝、钢和...基于16 mm口径气炮撞击实验,对铝颗粒增强的聚四氟乙烯(polytetrafluoroethylene)/Al(PTFE/Al)冲击反应复合材料的冲击反应阈值开展了研究。为研究不同撞击加载条件下应变率和碰撞应力对PTFE/Al冲击诱发反应的影响,实验中采用铝、钢和低密度聚乙烯(low density polyethylene,LDPE)这3种不同材料的靶板及不同长度的试样,进行不同加载条件下的测试分析。实验结果显示,PTFE/Al材料的冲击诱发同时受到碰撞压力和加载应变率的影响。同时,通过对试样撞靶过程进行数值模拟,并与实验和理论结果进行对比。基于实验数据,拟合出PTFE/Al材料冲击反应的的预测曲线。展开更多
Magnesium hydride(MgH2)was doped into PTFE/Al to improve the energy release characteristics of the material system and strive for better application in military engineering.Five types of PTFE/Al/MgH2 reactive material...Magnesium hydride(MgH2)was doped into PTFE/Al to improve the energy release characteristics of the material system and strive for better application in military engineering.Five types of PTFE/Al/MgH2 reactive materials with different MgH2 content were prepared by molding sintering method.The dynamic mechanical properties of the materials were studied by performing split-Hopkinson pressure bar(SHPB)tests and scanning electron microscope characterizations.The thermal behavior,reaction energy,reaction process and reaction mechanism were systematically investigated by conducting thermogravimetry-differential scanning calorimetry tests,oxygen bomb calorimeter measurements,Xray diffraction and SHPB tests.The results show that MgH2 particles less than 10%content contribute to heightening the dynamic mechanical properties of PTFE/Al system.The product Mg generated by decomposition of MgH2 can not only react with gas phase C2F4þbut also undergo a Grignard-type reaction with condensed PTFE.The reaction energy and ignition threshold of PTFE/Al/MgH2 reactive materials enhance monotonously as MgH2 content rose.With the increase of MgH2 content from 0%to 20%,the reaction time is prolonged as well as the reaction intensity is enhanced dramatically arising from the massive water vapour produced by the reaction between O2 and H2.The gaseous products generated can form a high pressure shortly after the reaction,which helps to elevate the damage effect of the PTFE/Al system.展开更多
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
In order to improve the wear resistance of elastic metallic-plastic thrust bearing pad, micro-assembling PTFE/Al2O3 multi-layer film was developed by alternating radio frequency（RF） magnetron sputtering PTFE and Al2...In order to improve the wear resistance of elastic metallic-plastic thrust bearing pad, micro-assembling PTFE/Al2O3 multi-layer film was developed by alternating radio frequency（RF） magnetron sputtering PTFE and Al2O3 targets. For enhancing the adhesion of the interfaces between PTFE and Al2O3 film, N+ implantation was employed. The structure, mechanical and micro-tribological properties were studied by XPS, X-ray photoelectron spectrometer and atomic force and friction force microscope （AFM/FFM）. The results show that the multi-layer consists of Al2O3 component and crystalline PTFE. The hardness of the multi-layer modified by ion implantation is less than that of Al2O3,but its toughness is greatly improved. The friction coefficient of PTFE/ Al2O3 multi-layer modified by ion implantation is much lower than that of Al2O3 film, and its resistance to wear is much greater than that of PTFE film. Therefore the wear resistance of elastic metallic-plastic thrust bearing pad is greatly improved.展开更多
<div style="text-align:justify;"> The constitutive behaviors of the sintered reactive material PTFE/Al/Si, one new formulation proposed by the author, were studied systematically and found it appears s...<div style="text-align:justify;"> The constitutive behaviors of the sintered reactive material PTFE/Al/Si, one new formulation proposed by the author, were studied systematically and found it appears strain-harden, stain-rate harden and temperature-soften effects, so it is more appropriate to describe the mechanical behavior with the Johnson-Cook model. With the static and dynamic experimental results and using the nonlinear fitting method, the mechanical and physical parameters in the Johnson-Cook model were determined, which supply one basis for the future numerical simulation study. </div>展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11872341 and 22075261)。
文摘As a typical energetic composite,polytetrafluoroethylene(PTFE)/aluminum(Al)has been widely applied in explosives,pyrotechnics,and propellants due to its ultra-high energy density and intense exothermic reaction.In this work,the radial gradient(RG)structure of PTFE/Al cylinders with three different PTFE morphologies(200 nm and 5μm particles and 5μm fiber)and content changes are prepared by 3D printing technology.The effect of radial gradient structure on the pressure output of PTFE/Al has been studied.Compared with the morphology change of PTFE,the change of component content in the gradient structure has an obvious effect on the pressure output of the PTFE/Al cylinder.Furthermore,the relationships of the morphology,content of PTFE and the combustion reaction of the PTFE/Al cylinder reveal that the cylinder shows a more complex flame propagation process than others.These results could provide a strategy to improve the combustion and pressure output of PTFE/Al.
文摘基于16 mm口径气炮撞击实验,对铝颗粒增强的聚四氟乙烯(polytetrafluoroethylene)/Al(PTFE/Al)冲击反应复合材料的冲击反应阈值开展了研究。为研究不同撞击加载条件下应变率和碰撞应力对PTFE/Al冲击诱发反应的影响,实验中采用铝、钢和低密度聚乙烯(low density polyethylene,LDPE)这3种不同材料的靶板及不同长度的试样,进行不同加载条件下的测试分析。实验结果显示,PTFE/Al材料的冲击诱发同时受到碰撞压力和加载应变率的影响。同时,通过对试样撞靶过程进行数值模拟,并与实验和理论结果进行对比。基于实验数据,拟合出PTFE/Al材料冲击反应的的预测曲线。
基金support from the National Natural Science Foun-dation of China(General Program.Grant No.51673213)Na-tional Natural Science Foundation of China(Grant No.51803235)are gratefully acknowledged.
文摘Magnesium hydride(MgH2)was doped into PTFE/Al to improve the energy release characteristics of the material system and strive for better application in military engineering.Five types of PTFE/Al/MgH2 reactive materials with different MgH2 content were prepared by molding sintering method.The dynamic mechanical properties of the materials were studied by performing split-Hopkinson pressure bar(SHPB)tests and scanning electron microscope characterizations.The thermal behavior,reaction energy,reaction process and reaction mechanism were systematically investigated by conducting thermogravimetry-differential scanning calorimetry tests,oxygen bomb calorimeter measurements,Xray diffraction and SHPB tests.The results show that MgH2 particles less than 10%content contribute to heightening the dynamic mechanical properties of PTFE/Al system.The product Mg generated by decomposition of MgH2 can not only react with gas phase C2F4þbut also undergo a Grignard-type reaction with condensed PTFE.The reaction energy and ignition threshold of PTFE/Al/MgH2 reactive materials enhance monotonously as MgH2 content rose.With the increase of MgH2 content from 0%to 20%,the reaction time is prolonged as well as the reaction intensity is enhanced dramatically arising from the massive water vapour produced by the reaction between O2 and H2.The gaseous products generated can form a high pressure shortly after the reaction,which helps to elevate the damage effect of the PTFE/Al system.
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.
文摘In order to improve the wear resistance of elastic metallic-plastic thrust bearing pad, micro-assembling PTFE/Al2O3 multi-layer film was developed by alternating radio frequency（RF） magnetron sputtering PTFE and Al2O3 targets. For enhancing the adhesion of the interfaces between PTFE and Al2O3 film, N+ implantation was employed. The structure, mechanical and micro-tribological properties were studied by XPS, X-ray photoelectron spectrometer and atomic force and friction force microscope （AFM/FFM）. The results show that the multi-layer consists of Al2O3 component and crystalline PTFE. The hardness of the multi-layer modified by ion implantation is less than that of Al2O3,but its toughness is greatly improved. The friction coefficient of PTFE/ Al2O3 multi-layer modified by ion implantation is much lower than that of Al2O3 film, and its resistance to wear is much greater than that of PTFE film. Therefore the wear resistance of elastic metallic-plastic thrust bearing pad is greatly improved.
文摘<div style="text-align:justify;"> The constitutive behaviors of the sintered reactive material PTFE/Al/Si, one new formulation proposed by the author, were studied systematically and found it appears strain-harden, stain-rate harden and temperature-soften effects, so it is more appropriate to describe the mechanical behavior with the Johnson-Cook model. With the static and dynamic experimental results and using the nonlinear fitting method, the mechanical and physical parameters in the Johnson-Cook model were determined, which supply one basis for the future numerical simulation study. </div>
