Tantalum electrolytic capacitors have performance advantages of long life,high temperature stability,and high energy storage capacity and are essential micro-energy storage devices in many pieces of military mechatron...Tantalum electrolytic capacitors have performance advantages of long life,high temperature stability,and high energy storage capacity and are essential micro-energy storage devices in many pieces of military mechatronic equipment,including penetration weapons.The latter are high-value ammunition used to strike strategic targets,and precision in their blast point is ensured through the use of penetration fuzes as control systems.However,the extreme dynamic impact that occurs during penetration causes a surge in the leakage current of tantalum capacitors,resulting in a loss of ignition energy,which can lead to ammunition half-burst or even sometimes misfire.To address the urgent need for a reliable design of tantalum capacitor for penetration fuzes,in this study,the maximum acceptable leakage current of a tantalum capacitor during impact is calculated,and two different types of tantalum capacitors are tested using a machete hammer.It is found that the leakage current of tantalum capacitors increases sharply under extreme impact,causing functional failure.Considering the piezoresistive effect of the tantalum capacitor dielectric and the changes in the contact area between the dielectric and the negative electrode under pressure,a force–electric simulation model at the microscale is established in COMSOL software.The simulation results align favorably with the experimental results,and it is anticipated that the leakage current of a tantalum capacitor will experience exponential growth with increasing pressure,ultimately culminating in complete failure according to this model.Finally,the morphological changes in tantalum capacitor sintered cells both without pressure and under pressure are characterized by electron microscopy.Broken particles of Ta–Ta_(2)O_(5)sintered molecular clusters are observed under pressure,together with cracks in the MnO_(2)negative base,proving that large stresses and strains are generated at the micrometer scale.展开更多
Greener synthesis of nanoparticle is a revolutionizing area in research field.Biological method of reduction of metal ions is often preferred because they are clean,safe,biocompatible,and environmentally acceptable th...Greener synthesis of nanoparticle is a revolutionizing area in research field.Biological method of reduction of metal ions is often preferred because they are clean,safe,biocompatible,and environmentally acceptable than physical,chemical,and mechanical methods.The wet biomass of Aspergillus terreus（A.terreus） was utilized for the intracellular synthesis of gold nanoparticles.Gold nanoparticles were produced when an aqueous solution of chloroauric acid was reduced by A.terreus biomass as the reducing agent.Production of gold nanoparticles was confirmed by the color change of biomass from yellow to pinkish violet.The produced nanoparticles were then characterized by FT-IR,SEM,EDS,and XRD.The SEM images revealed that the nanoparticles were spherical,irregularly shaped with no definite morphology.Average size of the biosynthesized gold nanoparticles was 186 nm.The presence of the gold nanoparticle was confirmed by EDS analysis.Crystalline nature of synthesized gold nanoparticle was confirmed by XRD pattern.展开更多
In this paper, a kind of three-dimensional analysis technology for characterizing non-metallic inclusions in steel was clearly elaborated. It is an electron microscopy observation, namely the non-aqueous electrolysis ...In this paper, a kind of three-dimensional analysis technology for characterizing non-metallic inclusions in steel was clearly elaborated. It is an electron microscopy observation, namely the non-aqueous electrolysis extraction method with a settled coulometer. In the research,the extraction effects of non-metallic inclusions in different electrolysis systems were studied, and it was concluded that alkalescent 2% TEA non-aqueous electrolyte was applicable for extracting most of non-metallic inclusion particles in steel. And then, in order to ensure the microscopic characterization and statistical calculation of inclusion particles, some electrolysis parameters should be confirmed, such as the size of the sample, control of the electrolysis mass, electric current, etc. Furthermore, for preventing the disturbance of carbides and presenting clear three-dimensional appearance by microscopic characterization, magnetic separation was utilized to separate the inclusion particles from carbides, which was useful for getting more veracious types, particle sizes and chemical composition of inclusions. Moreover, through calculation of quantity and particle size of inclusions in continuous determinate fields, the total quantity per unit volume or area and the particle size distribution of inclusions could be acquired by conversion with electrolysis loss. Besides, the comparison between this method and traditional quantitative metallography was also discussed, and finally, a conclusion was drawn that both of them have respectively applications in characterizing inclusions.展开更多
In this study,the compressive,split tensile,and flexural strengths of concrete with nano-CaCO_(3) only were compared with those of concrete with nano-CaCO_(3) and basalt fibers through field experiments,and the underl...In this study,the compressive,split tensile,and flexural strengths of concrete with nano-CaCO_(3) only were compared with those of concrete with nano-CaCO_(3) and basalt fibers through field experiments,and the underlying mechanisms were analyzed by the Scanning Electron Microscope (SEM) techniques.On the mesoscale,a damage model of concrete was established based on the continuum progressive damage theory,which was used to investigate the influence of different lengths and contents of fibers on the mechanical properties of concrete.Then,the experimental and numerical simulation results were compared and analyzed to verify the feasibility of model.The results show that nano-CaCO_(3) can enhance the compressive strength of the concrete,with an optimal content of 2.0%.Adding basalt fibers into the nano-CaCO_(3) reinforced concrete may further enhance the compressive,split tensile,and flexural strengths of the concrete;however,the higher content of basalt fiber can not lead to higher performance of concrete.The optimal length and content of fiber are 6 mm and 0.20%,respectively.The SEM result shows that the aggregation of basalt fibers is detrimental to the mechanical properties of concrete.The numerical simulation results are in good agreement with the experimental results.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.52007084).
文摘Tantalum electrolytic capacitors have performance advantages of long life,high temperature stability,and high energy storage capacity and are essential micro-energy storage devices in many pieces of military mechatronic equipment,including penetration weapons.The latter are high-value ammunition used to strike strategic targets,and precision in their blast point is ensured through the use of penetration fuzes as control systems.However,the extreme dynamic impact that occurs during penetration causes a surge in the leakage current of tantalum capacitors,resulting in a loss of ignition energy,which can lead to ammunition half-burst or even sometimes misfire.To address the urgent need for a reliable design of tantalum capacitor for penetration fuzes,in this study,the maximum acceptable leakage current of a tantalum capacitor during impact is calculated,and two different types of tantalum capacitors are tested using a machete hammer.It is found that the leakage current of tantalum capacitors increases sharply under extreme impact,causing functional failure.Considering the piezoresistive effect of the tantalum capacitor dielectric and the changes in the contact area between the dielectric and the negative electrode under pressure,a force–electric simulation model at the microscale is established in COMSOL software.The simulation results align favorably with the experimental results,and it is anticipated that the leakage current of a tantalum capacitor will experience exponential growth with increasing pressure,ultimately culminating in complete failure according to this model.Finally,the morphological changes in tantalum capacitor sintered cells both without pressure and under pressure are characterized by electron microscopy.Broken particles of Ta–Ta_(2)O_(5)sintered molecular clusters are observed under pressure,together with cracks in the MnO_(2)negative base,proving that large stresses and strains are generated at the micrometer scale.
文摘Greener synthesis of nanoparticle is a revolutionizing area in research field.Biological method of reduction of metal ions is often preferred because they are clean,safe,biocompatible,and environmentally acceptable than physical,chemical,and mechanical methods.The wet biomass of Aspergillus terreus（A.terreus） was utilized for the intracellular synthesis of gold nanoparticles.Gold nanoparticles were produced when an aqueous solution of chloroauric acid was reduced by A.terreus biomass as the reducing agent.Production of gold nanoparticles was confirmed by the color change of biomass from yellow to pinkish violet.The produced nanoparticles were then characterized by FT-IR,SEM,EDS,and XRD.The SEM images revealed that the nanoparticles were spherical,irregularly shaped with no definite morphology.Average size of the biosynthesized gold nanoparticles was 186 nm.The presence of the gold nanoparticle was confirmed by EDS analysis.Crystalline nature of synthesized gold nanoparticle was confirmed by XRD pattern.
文摘In this paper, a kind of three-dimensional analysis technology for characterizing non-metallic inclusions in steel was clearly elaborated. It is an electron microscopy observation, namely the non-aqueous electrolysis extraction method with a settled coulometer. In the research,the extraction effects of non-metallic inclusions in different electrolysis systems were studied, and it was concluded that alkalescent 2% TEA non-aqueous electrolyte was applicable for extracting most of non-metallic inclusion particles in steel. And then, in order to ensure the microscopic characterization and statistical calculation of inclusion particles, some electrolysis parameters should be confirmed, such as the size of the sample, control of the electrolysis mass, electric current, etc. Furthermore, for preventing the disturbance of carbides and presenting clear three-dimensional appearance by microscopic characterization, magnetic separation was utilized to separate the inclusion particles from carbides, which was useful for getting more veracious types, particle sizes and chemical composition of inclusions. Moreover, through calculation of quantity and particle size of inclusions in continuous determinate fields, the total quantity per unit volume or area and the particle size distribution of inclusions could be acquired by conversion with electrolysis loss. Besides, the comparison between this method and traditional quantitative metallography was also discussed, and finally, a conclusion was drawn that both of them have respectively applications in characterizing inclusions.
基金Funded by the National Natural Science Foundation of China (No. 51969026)the Natural Science Foundation of Qinghai Province in China (No. 2018-ZJ-750)。
文摘In this study,the compressive,split tensile,and flexural strengths of concrete with nano-CaCO_(3) only were compared with those of concrete with nano-CaCO_(3) and basalt fibers through field experiments,and the underlying mechanisms were analyzed by the Scanning Electron Microscope (SEM) techniques.On the mesoscale,a damage model of concrete was established based on the continuum progressive damage theory,which was used to investigate the influence of different lengths and contents of fibers on the mechanical properties of concrete.Then,the experimental and numerical simulation results were compared and analyzed to verify the feasibility of model.The results show that nano-CaCO_(3) can enhance the compressive strength of the concrete,with an optimal content of 2.0%.Adding basalt fibers into the nano-CaCO_(3) reinforced concrete may further enhance the compressive,split tensile,and flexural strengths of the concrete;however,the higher content of basalt fiber can not lead to higher performance of concrete.The optimal length and content of fiber are 6 mm and 0.20%,respectively.The SEM result shows that the aggregation of basalt fibers is detrimental to the mechanical properties of concrete.The numerical simulation results are in good agreement with the experimental results.
