Mg-6Zn-1Y(at.%)ribbons with strengthening precipitates of multi-type nanoquasicrystals were prepared by melt-spinning followed by aging treatments.Microstructural evolution of the rapidly solidified ribbons during iso...Mg-6Zn-1Y(at.%)ribbons with strengthening precipitates of multi-type nanoquasicrystals were prepared by melt-spinning followed by aging treatments.Microstructural evolution of the rapidly solidified ribbons during isothermal aging was comprehensively studied using various electron microscopy techniques.Two new kinds of decagonal quasicrystals were formed in aged ribbons,in addition to precipitation of nanometer icosahedral quasicrystals.Atomic-resolution observations reveal that both decagonal quasicrystals can be modeled by quasiperiodic tiling with decagonal clusters of 2.5 nm in diameter,but overlap of neighboring clusters in both decagonal quasicrystals is different from the Gummelt model observed in other quasicrystals.A shell composed of complex Laves Mg-Zn domains was formed surrounding each decagonal quasicrystal precipitate upon prolonged aging.In addition,all kinds of nanoprecipitates exhibit excellent structure and size stability at 573 K.Our findings may have implications for not only fundamental studies about quasicrystals,but also microstructural manipulation of high-performance Mg alloys.展开更多
The microstructural evolution of a Mg-10Ni-2Mm（molar fraction,%）（Mm=Ce,La-rich mischmetal） hydrogen storage alloys applied with various solidification rates was studied.The results show that the grain size of melt...The microstructural evolution of a Mg-10Ni-2Mm（molar fraction,%）（Mm=Ce,La-rich mischmetal） hydrogen storage alloys applied with various solidification rates was studied.The results show that the grain size of melt-spun ribbon is remarkably reduced by increasing the solidification rate.The microcrystalline,nanocrystalline and amorphous microstructures are obtained by applying the surface velocities of the graphite wheel of 3.1,10.5 and 20.9 m/s,respectively.By applying the surface velocity of the graphite wheel of 3.1 m/s,the melt-spun specimen obtains full crystalline with a considerable amount of coarse microcrystalline Mg and Mg2Ni except for some Mm-rich particles.The amount of nanocrystalline phases significantly increases with increasing the surface velocity of the wheel to 10.5 m/s,and the microstructure is composed of a large amount of nanocrystalline phases of Mg and Mg2Ni particles.A mixed microstructure containing amorphous and nanocrystalline phases is obtained at a surface velocity of the wheel of 20.9 m/s.The optimal microstructure with a considerable amount of nanocrystalline Mg and Mg2Ni in an amorphous matrix is expected to have the maximum hydrogen absorption capacity and excellent hydrogenation kinetics.展开更多
针对传统LTE(long term evolution)系统开始传输前需要获得相关信息的周期过长问题,提出LTE在占用ISM(industrial scientific medical)频段时的快速传输方法.该方法对MAC(media access control)层的RTS/CTS(request to send/clear to se...针对传统LTE(long term evolution)系统开始传输前需要获得相关信息的周期过长问题,提出LTE在占用ISM(industrial scientific medical)频段时的快速传输方法.该方法对MAC(media access control)层的RTS/CTS(request to send/clear to send)帧进行重新定义,使其帧控制字段和地址字段有空闲位来提前交换一些必需的信令,以达到在LTE系统短时间占用ISM频段的情况下,能够快速开始LTE传输.分析表明,该方法可缩短LTE系统开始数据传输的时延.展开更多
基金supported by the National Natural Science Foundation of China (grant number: 51771202, 51971225, 52001225)Key Research of Frontier Science, Chinese Academy of Science (grant number: QYZDY-SSW-JSC207)+1 种基金Ji Hua Laboratory (X210141TL210)Guangdong Province (2021B0301030003)
文摘Mg-6Zn-1Y(at.%)ribbons with strengthening precipitates of multi-type nanoquasicrystals were prepared by melt-spinning followed by aging treatments.Microstructural evolution of the rapidly solidified ribbons during isothermal aging was comprehensively studied using various electron microscopy techniques.Two new kinds of decagonal quasicrystals were formed in aged ribbons,in addition to precipitation of nanometer icosahedral quasicrystals.Atomic-resolution observations reveal that both decagonal quasicrystals can be modeled by quasiperiodic tiling with decagonal clusters of 2.5 nm in diameter,but overlap of neighboring clusters in both decagonal quasicrystals is different from the Gummelt model observed in other quasicrystals.A shell composed of complex Laves Mg-Zn domains was formed surrounding each decagonal quasicrystal precipitate upon prolonged aging.In addition,all kinds of nanoprecipitates exhibit excellent structure and size stability at 573 K.Our findings may have implications for not only fundamental studies about quasicrystals,but also microstructural manipulation of high-performance Mg alloys.
基金Project(2007DFA50590)supported by the International S&T Cooperation Projects the Norwegian Research Council for financial support
文摘The microstructural evolution of a Mg-10Ni-2Mm（molar fraction,%）（Mm=Ce,La-rich mischmetal） hydrogen storage alloys applied with various solidification rates was studied.The results show that the grain size of melt-spun ribbon is remarkably reduced by increasing the solidification rate.The microcrystalline,nanocrystalline and amorphous microstructures are obtained by applying the surface velocities of the graphite wheel of 3.1,10.5 and 20.9 m/s,respectively.By applying the surface velocity of the graphite wheel of 3.1 m/s,the melt-spun specimen obtains full crystalline with a considerable amount of coarse microcrystalline Mg and Mg2Ni except for some Mm-rich particles.The amount of nanocrystalline phases significantly increases with increasing the surface velocity of the wheel to 10.5 m/s,and the microstructure is composed of a large amount of nanocrystalline phases of Mg and Mg2Ni particles.A mixed microstructure containing amorphous and nanocrystalline phases is obtained at a surface velocity of the wheel of 20.9 m/s.The optimal microstructure with a considerable amount of nanocrystalline Mg and Mg2Ni in an amorphous matrix is expected to have the maximum hydrogen absorption capacity and excellent hydrogenation kinetics.
文摘针对传统LTE(long term evolution)系统开始传输前需要获得相关信息的周期过长问题,提出LTE在占用ISM(industrial scientific medical)频段时的快速传输方法.该方法对MAC(media access control)层的RTS/CTS(request to send/clear to send)帧进行重新定义,使其帧控制字段和地址字段有空闲位来提前交换一些必需的信令,以达到在LTE系统短时间占用ISM频段的情况下,能够快速开始LTE传输.分析表明,该方法可缩短LTE系统开始数据传输的时延.
