Metal mold micron scale precision casting technology was developed successfully,and three-dimension complicated microgear castings in micron scale were produced.Evolvement regularity of microgear castings were observe...Metal mold micron scale precision casting technology was developed successfully,and three-dimension complicated microgear castings in micron scale were produced.Evolvement regularity of microgear castings were observed by optical microscope and scanning electron microscope.Compared with conventional casting,microcasting is characterized by typical nonequilibrium solidification,for example,its grain size can be refined significantly,eutectic structure is transformed from lamellar morphology to rod eutectic,and the ratio of primary phase is increased.This kind of microstructure can promote mechanical properties of microcasting.展开更多
The effects of sintering temperature on the surface roughness of gypsum bonded investments were investigated to find the appropriate sintering temperature applied for micro-investment casting.The surface roughness tes...The effects of sintering temperature on the surface roughness of gypsum bonded investments were investigated to find the appropriate sintering temperature applied for micro-investment casting.The surface roughness tests were carried out at sintering temperatures ranging from room temperature to 1,000 ℃ for investment compounds mixed from calcium sulphate α-hemihydrate and quartz powder (wt.%, 6:4; 5:5, 4:6, 3:7).In this experiment, each investment compound was prepared by pouring the investment materials into a plastic bottle with the good surface roughness (Ra～0.2 μm).DTA-TG curves were measured using a thermal analyzer to investigate the difference of surface roughness at different temperatures.The results show that the surface roughness of gypsum bonded investment is temperature sensitive.The preheating temperature of the mold should be up to 600 ℃, but not over 700 ℃, and the investment compound with 60 % plaster and 40 % quartz powder is applicable for preparing the micro-structures.The micro-structures with 100 μm diameter were produced in the present studies.The results show that the surface roughness of the casting is only Ra～0.51 μm, slightly rougher than that of the investment mold.展开更多
The rapid development of nanotechnology has significantly revolutionized wearable electronics and expanded their functionality.Through introducing innovative solutions for energy harvesting and autonomous sensing,this...The rapid development of nanotechnology has significantly revolutionized wearable electronics and expanded their functionality.Through introducing innovative solutions for energy harvesting and autonomous sensing,this research presents a cost-effective strategy to enhance the performance of triboelectric nanogenerators(TENGs).The TENG was fabricated from polyvinylidene fluoride(PVDF)and N,N'-poly(methyl methacrylate)(PMMA)blend with a porous structure via a novel optimized quenching method.The developed approach results in a highβ-phase content(85.7%)PVDF/3wt.%PMMA porous blend,known for its superior piezoelectric properties.PVDF/3wt.%PMMA modified porous TENG demonstrates remarkable electrical output,with a dielectric constant of 40 and an open-circuit voltage of approximately 600 V.The porous matrix notably increases durability,enduring over 36000 operational cycles without performance degradation.Moreover,practical applications were explored in this research,including powering LEDs and pacemakers with a maximum power output of 750mWm^(-2).Also,TENG served as a self-powered tactile sensor for robotic applications in various temperature conditions.The work highlights the potential of the PVDF/PMMA porous blend to utilize the next-generation self-powered sensors and power small electronic devices.展开更多
Carbon nanostructures, including carbon nanotubes （CNTs） and gra- phene, have been studied extensively due to their special structures, excellent electrical properties and high chemical stability. With the developme...Carbon nanostructures, including carbon nanotubes （CNTs） and gra- phene, have been studied extensively due to their special structures, excellent electrical properties and high chemical stability. With the development of nanotechnology and nanoscience, various methods have been developed to synthesize CNTs/graphene and to assemble them into microelectroniclsensor devices. In this review, we mainly demon- strate the latest progress in synthesis of CNTs and graphene and their applications in field-effect transistors （FETs） for biological sensors.展开更多
基金Project(50475028)supported by the National Natural Science Foundation of China
文摘Metal mold micron scale precision casting technology was developed successfully,and three-dimension complicated microgear castings in micron scale were produced.Evolvement regularity of microgear castings were observed by optical microscope and scanning electron microscope.Compared with conventional casting,microcasting is characterized by typical nonequilibrium solidification,for example,its grain size can be refined significantly,eutectic structure is transformed from lamellar morphology to rod eutectic,and the ratio of primary phase is increased.This kind of microstructure can promote mechanical properties of microcasting.
基金supported by the National Natural Sicience Foundation of China (No.50475028)the Natural Science Foundation of Heilongjiang Province of China (No.ZJG04-01)
文摘The effects of sintering temperature on the surface roughness of gypsum bonded investments were investigated to find the appropriate sintering temperature applied for micro-investment casting.The surface roughness tests were carried out at sintering temperatures ranging from room temperature to 1,000 ℃ for investment compounds mixed from calcium sulphate α-hemihydrate and quartz powder (wt.%, 6:4; 5:5, 4:6, 3:7).In this experiment, each investment compound was prepared by pouring the investment materials into a plastic bottle with the good surface roughness (Ra～0.2 μm).DTA-TG curves were measured using a thermal analyzer to investigate the difference of surface roughness at different temperatures.The results show that the surface roughness of gypsum bonded investment is temperature sensitive.The preheating temperature of the mold should be up to 600 ℃, but not over 700 ℃, and the investment compound with 60 % plaster and 40 % quartz powder is applicable for preparing the micro-structures.The micro-structures with 100 μm diameter were produced in the present studies.The results show that the surface roughness of the casting is only Ra～0.51 μm, slightly rougher than that of the investment mold.
基金supported by the research projects AP14869428 from the Ministry of Science and Higher Education of the Republic of Kazakhstan20122022FD4135 from Nazarbayev University.
文摘The rapid development of nanotechnology has significantly revolutionized wearable electronics and expanded their functionality.Through introducing innovative solutions for energy harvesting and autonomous sensing,this research presents a cost-effective strategy to enhance the performance of triboelectric nanogenerators(TENGs).The TENG was fabricated from polyvinylidene fluoride(PVDF)and N,N'-poly(methyl methacrylate)(PMMA)blend with a porous structure via a novel optimized quenching method.The developed approach results in a highβ-phase content(85.7%)PVDF/3wt.%PMMA porous blend,known for its superior piezoelectric properties.PVDF/3wt.%PMMA modified porous TENG demonstrates remarkable electrical output,with a dielectric constant of 40 and an open-circuit voltage of approximately 600 V.The porous matrix notably increases durability,enduring over 36000 operational cycles without performance degradation.Moreover,practical applications were explored in this research,including powering LEDs and pacemakers with a maximum power output of 750mWm^(-2).Also,TENG served as a self-powered tactile sensor for robotic applications in various temperature conditions.The work highlights the potential of the PVDF/PMMA porous blend to utilize the next-generation self-powered sensors and power small electronic devices.
文摘Carbon nanostructures, including carbon nanotubes （CNTs） and gra- phene, have been studied extensively due to their special structures, excellent electrical properties and high chemical stability. With the development of nanotechnology and nanoscience, various methods have been developed to synthesize CNTs/graphene and to assemble them into microelectroniclsensor devices. In this review, we mainly demon- strate the latest progress in synthesis of CNTs and graphene and their applications in field-effect transistors （FETs） for biological sensors.
