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Metastable liquid properties and rapid crystal growth of Ti-Ni-Al alloy investigated by electrostatic levitation and molecular dynamics simulation

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Science China(Technological Sciences) 2021年第10期64卷 2200-2210页

作者： XIAO RuiLin RUAN Ying LIN MaoJie QIN JingYu LI Hui HU Liang WEI BingBo MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions School of Physical Science and TechnologyNorthwestern Polytechnical UniversityXi’an 710072China Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of EducationShandong UniversityJinan 250061China

electrostatic levitation technique and molecular dynamics simulation were performed to investigate the thermophysical properties,liquid structure and crystal growth dependence on undercooling of Ti_(85)Ni_(10)Al_(5) *** liquid Ti_(85)Ni_(10)Al_(5) alloy was substantially undercooled up to 335 K(0.18T_(L)).As undercooling increased,the potential energy of the liquid alloy decreased and the alloy entered into a high metastable *** this state,the atoms tended to bond with each other and the clusters were inclined to convert into high-coordinated clusters,as confirmed by the fraction of the high-coordinated clusters *** enlarged clusters and enhanced local structure stability contributed to the increase of the thermophysical parameters and crystal growth velocity,and eventually dendrite *** density,the specific heat and the surface tension of liquid alloy exhibited a linear relation with temperature and the shear viscosity of liquid alloy showed exponential variation which showed good agreement with the calculation results by molecular dynamics *** growth velocity first increased slowly and then dramatically once the undercooling exceeded the *** achieved maximum crystal growth velocity was 12.4 m s^(−1) and it was up to 326 times of the value at 94 K undercooling.

关键词： electrostatic levitation thermophysical properties liquid structure crystal growth molecular dynamics

Research of electrostatic levitation techniques applied on microgravity measurement

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Research of electrostatic levitation techniques applied on m...

Geometric optimization of electrostatic fields for stable levitation of metallic materials

The 7th China-Japan Workshop on Microgravity Sciences

作者： Liming Wu Jingxin Dong Fengtian Han Department of precision instruments and mechanology Tsinghua University Beijing 100084 China

＜正＞electrostatic levitation accelerometers（ELA）have been successfully used in microgravity measurement in space,in which electrostatic levitation is one of key techniques for *** sensing mass is only suspended by controllable electrostatic forces in closed-loop force-balanced feedback *** of no mechanical constraint of the sensing mass,the sensitivity,

关键词： electrostatic levitation MEMS accelerometer Rotational gyroscope Bulk silicon process

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Science China(Technological Sciences) 2013年第1期56卷 53-59页

作者： HU Liang WANG HaiPeng LI LiuHui WEI BingBo Department of Applied Physics Northwestern Polytechnical University

Experimental and computational methods are used to optimize the electrostatic field for levitating metallic *** calculated launch voltage increases linearly with the distance between top and bottom *** combination of a larger top electrode diameter with a smaller bottom diameter may enhance the levitation ability because the electric field intensity near the levitated sample is *** convex and bottom concave electrodes can guarantee good levitation stability but decrease the levitation *** design of bottom electrode is crucial to attain not only a stable levitation state but also a higher levitation *** a measure characterizing the intrinsic levitation ability of various materials,the product of density and diameter of levitated samples can be used to determine the launch voltage for counteracting gravity according to a power relationship.

关键词： electrostatic levitation containerless processing capacitive induction space science

Dust levitation and transport over the surface of the Moon

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Science China Earth Sciences 2016年第10期59卷 2053-2061,2060-2061页

作者： LI Lei ZHANG YiTeng ZHOU Bin FENG YongYong State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100190China

Exposed to space plasma and solar radiation, electrostatic potential may build up in the lunar regolith, leading to a wealth of dust phenomena, including levitation, oscillation, and transport over the surface. Based on plasma sheath theory,the global near-surface plasma environment is modeled, and the dynamics of charged dust are investigated. Results show that sub-micron sized dust particles can be levitated by the electric field over the surface, forming a dust belt that changes in position and thickness depending on the solar zenith angle. On the dayside of the Moon, stably levitated particles are about ten times smaller, and collect in a thinner belt closer to the surface than do those on the nightside. Although the size and charge of stably levitated dust particles are dependent on ambient plasma conditions, initial charge and velocity, which are closely related to the dynamics of dust particles including charging, oscillation, and damping, will determine whether, or not, a particle can attain stable levitation. Horizontal electrostatic dust transport near to the terminator region may lead to net deposition of dust from the dark into the sunlit hemisphere. Finally, because of different charging processes that result due to rotation of the Moon, before precipitation,dust particles in the dusk terminator region may be transported much longer distances and oscillate to much higher altitude than these in the dawn terminator.

关键词： Moon Lunar dust Dust particle dynamics electrostatic levitation

Modeling and Analysis of a Micromotor with an electrostatically Levitated Rotor

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Chinese Journal of Mechanical Engineering 2009年第1期22卷 1-8页

作者： HAN Fengtian WU Qiuping ZHANG Rong Department of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China

The modeling and evaluation of a prototype rotary micromotor where the annular rotor is supported electrostatically in five degrees of freedom is presented in order to study the behavior of this levitated micromotor and further optimize the device geometry. The analytical torque model is obtained based on the principle of a planar variable-capacitance electrostatic motor while the viscous damping caused by air film between the stator and rotor is derived using laminar Couette flow model. Simulation results of the closed-loop drive motor, based on the developed dynamic model after eliminating mechanical friction torque via electrostatic suspension, are presented. The effects of the high-voltage drive, required for rotation of the rotor, on overload capacity and suspension stiffness of the electrostatic bearing system are also analytically evaluated in an effort to determine allowable drive voltage and attainable rotor speed in operation. The analytical results show that maximum speed of the micromotor is limited mainly by viscous drag torque and stiffness of the bearing system. Therefore, it is expected to operate the device in vacuum so as to increase the rotor speed significantly, especially for those electrostatically levitated micromotors to be used as an angular rate micro-gyroscope.

关键词： electrostatic levitation electrostatic micromotor variable-capacitance motor micro-gyroscope