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The attenuation of oscillatory thermo-capillary convection in the oxide melt by a transverse magnetic field

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Science China(Physics,Mechanics & Astronomy) 2007年第4期50卷 519-524页

作者： jin weiqing AI Fei HONG Yong LUO HaoSu LIU Yan PAN XiuHong Shanghai Institute of Ceramics Chinese Academy of SciencesShanghai 200050China

The effect of a transverse magnetic field on the oscillatory thermocapillary con- vection in the NaBi(WO4)2 melt was studied by using the in-situ observation system. The oscillation was attenuated when the 60 mT magnetic field was applied, as shown by the decrease in the amplitude and the frequency. Furthermore, the os- cillation under smaller temperature difference was stabilized after the magnetic field was applied. The magnetic effect could be due to the Lorentz force generated by the interaction between motional ions and the vertical magnetic field. The ionic conductivities were measured to demonstrate the effect of the magnetic field. The solid ionic electrical conductivity increases with the temperature rise, and the melt ionic electrical conductivity was measured to be about 2.0×10-4 -1cm-1. Experi- mental results manifest that the effect of the magnetic field on anions and cations in the melt makes the flow change to the direction normal to the applied field, so the flow is more orderly and the oscillation is suppressed.

关键词： oscillatory thermocapillary convection high-temperature melt in-situ observation magnetic field

EXPERIMENTAL STUDIES ON GROWTH KINETICS OF SALOL CRYSTALS FROM THE MELT

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Chinese Physics Letters 1987年第1期4卷 17-20页

作者： jin weiqing Hiroshi Komatsu Shanghai Institute of Ceramics Academia SinicaShanghai The Research Institute for Iron Steel and Other MetalsTohoku UniversityJapan

In situ observation method has been carried out to investigate the growth kinetics of salol from the *** temperature-dependence of growth rate of salol crystals in a supercooling range of 0 to 3°C for(102)and(012)faces are *** lateral(two dimensional nucleation)–to-continuous growth transition has been *** free energy of stepε,the radius of the critical nucleus r*,and the excess free energy of a critical nucleusΔG*are measured for(102)and(012)faces.

关键词： critical kinetics radius

Morphologies of solid-liquid interface and surface steps during rapid growth of BaB_2O_4 single crystals

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Science China(Physics,Mechanics & Astronomy) 2007年第4期50卷 539-545页

作者： PAN XiuHong, AI Fei, jin weiqing, LIU Yan & ZHANG Ying Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China 1. Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050 China

The evolution of solid-liquid interface during BBO single crystal growth was stud- ied by the differential interference microscopy. And the step morphology on (0001) surface of the as-grown crystal was observed by the atomic force microscopy as well. It was found that the transition from a flat solid-liquid interface to a skeletal shape will occur in case of rapid growth. However, AFM images of surface steps revealed morphology differences correlated with crystallographic directions. The steps advancing along direction form the step flow, whereas those steps propagating along direction shape into step segments. Measurements of step heights by AFM indicated that it is the high anisotropy of the dimension of growth unit and step bunching due to the enlargement of concentration difference along the surface that results in the anisotropy of step morphologies.

关键词： crystal growth morphological instability growth step AFM observation

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材料制备中的界面质量输运现象

稀有金属材料与工程 2004年第z1期33卷 80-82页

作者：金蔚青中国科学院上海硅酸盐研究所上海200050

具有明确边界条件的多组元体系在凝固时,溶液内的热量和质量输运方程的严格求解非常困难,因此简化方程是十分必要的.本文在普适质量输运方程的基础上,采用二维模型中的无量纲Pct数,简化了双组元体系的扩散方程.证实了简化后的质量扩散... 详细信息

具有明确边界条件的多组元体系在凝固时,溶液内的热量和质量输运方程的严格求解非常困难,因此简化方程是十分必要的.本文在普适质量输运方程的基础上,采用二维模型中的无量纲Pct数,简化了双组元体系的扩散方程.证实了简化后的质量扩散模型在凝固现象中的物理有效性.明确地指出存在着由扩散引起的沿着固液界面的整体流,它亦被限制在质量边界层内,即固液界面溶液一侧溶质浓度有显著变化的区域内.氧化物晶体生长实时观测实验证实了上述结论的正确性.为了强调质量流的物理概念,讨论采用了二维双组元模型.

关键词：质量扩散方程凝固:界面质量整体流

In situ observation of NaBi(WO_4)_2 dendrite growth and the study on microstructure of solidification

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Science China(Physics,Mechanics & Astronomy) 2007年第4期50卷 525-530页

作者： AI Fei, HONG Yong, jin weiqing, LUO HaoSu, LIU Yan & PAN XiuHong Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China 1. Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050 China

The dendrite growth process of transparent NaBi(WO4)2 with small prandtl and high melting point was studied by using the in-situ observation system. According to the dynamic images and detailed information, there are two kinds of restriction effect on the dendrite growth, the competition between arms and branches and the convection in the melt. The dendrite growth rate was time dependent, and the rate of arm growth reached the maximum 5.8 mm/s in the diffusive-advective region and rapidly decreased in the diffusive-convective region. The growth rate of branch had the same change trends as the arm’s. Based on the EPMA-EDS data of solidifica- tion structure of quenched NaBi(WO4)2 melt, it was found that there were compo- nent differences from stoichiometric concentration in the melt near the interface during the growth process.

关键词： oxide dendrite in-situ observation solidification structure

EXPERIMENTAL AND THEORETICAL MORPHOLOGY OF SALOL

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Chinese Physics Letters 1986年第2期3卷 53-56页

作者： jin weiqing Hiroshi Komatsu Tetsuo Inoue Shanghai Institute of Ceramics Academia SinicaShanghai The Research Institute for Iron Steel and Other MetalsTohoku UniversityJapan

The morphology of salol crystals in relation to supercooling has been studied by means of the in situ obseirvation method and the Kyropoulos technique;and Hartman-Perdok's PBC method was used to analyse the morphology based on the relationship between crystal form and its *** experimental results of the morphology of salol crystals are compared with the theoretical calculations.

关键词： structure Hartman crystal

NUMERICAL MODELLING OF VELOCITY AND TEMPERATURE DISTRIBUTIONS OF THE BUOYANCY CONVECTION EFFECT IN KNbO3 MELT

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空间科学学报 2002年第Z1期22卷 164-164页

作者： LIU Zhaohua jin weiqing PAN Zhilei Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China

　　Numerical modelling of velocity and temperature fields in high-temperature KNbO3 melt of a loop-shaped Pt wire heater is carried out by using the commercial com putational code ANSYS for the mathematical solution of the governing *** on the experimental boundary conditions and the Boussinesq approximation,the numerical modelling of a steady and two-dimensional model is applied to study the process under consideration of the buoyancy-driven convection condition. The result is compared with the previous experimental and theoretical data obtained in our laboratory, and the former is in agreement with the latter. Thus a theoretical guide for reasonable growth conditions is provided by studying in depth the real fluid flow effects in the crystal growth from the melt.……

关键词： numerical modelling Boussinesq approximation boundary conditions temperature fields crystal growth fluid flow

EFFECTS OF CONVECTIVE FLUID MOTION UPON OXIDE CRYSTAL GROWTH IN HIGH TEMPERATURE SOLUTION

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空间科学学报 2002年第Z1期22卷 159-159页

作者： jin weiqing CAI Lixia LIANG Xinan PAN Zhilei Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China Shanghai Institute of Ceramics The Chinese Academy of Sciences Shanghai 200050 P.R. China

　　For understanding of the influence of convective flow on crystal growth, space high temperature in situ observation instrument (SHITISOI) is dedicated to visualize and record the whole growth process of oxide crystals in high temperature up to 1000°C. Model experiments using transparent liquids such as KNbO3 and a mix ture of Li2B4O7+KNbO3 were chosen to investigate effects on ground and in *** the earth, an investigation of growth kinetics of KNbO3 crystal related to two different states of convection: diffusive-advective flow and diffusive-convective flow,has been performed. The per unit length of a step e is calculated from the exper imental data for two different states of convection. Analyses of these data show the effect of buoyancy convection is to enhance the sharpness of the interface. The growth of KNbO3 crystals from solution of KNbO3+Li2B4O7 was investigated in space. The streamlines of the steady thermocapillary convection in Li2B4O7 solvent was observed. Due to thermocapillary convection, KNbO3 crystal grains grew and filled the whole solution homogeneously. Earth-based quenching experiments are de signed in order to study polyhedral instability of KNbO3 crystal, which is controlled by diffusion mechanism limitation. In all cases, when the crystal was nucleated near air/solution surface, it lost its polyhedral stability and varied from polyhedrons to dedrites. The thickness of diffusion mechanism limitation layer is about 60μm.……

关键词： HIGH TEMPERATURE thermocapillary convection diffusion mechanism high temperature polyhedral instability in situ observation growth kinetics oxide crystals crystal growth the earth in order

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一种卷绕系统大行程精密自动测量计米方法

传感技术学报 2021年第8期34卷 1062-1068页

作者：金伟清李郁刘笃喜西安明德理工学院智能制造与控制技术学院陕西西安710124 西北工业大学机电学院陕西西安710072

大行程位移测量计米精度决定了卷绕式系统的位置控制精度。目前的计米方法测量误差大,不易实现正反双向计米。提出并设计了一种面向卷绕系统的大行程位移精密自动测量计米方法,以双同步齿形带传动副作为精确夹持传送装置,同时采用主动... 详细信息

大行程位移测量计米精度决定了卷绕式系统的位置控制精度。目前的计米方法测量误差大,不易实现正反双向计米。提出并设计了一种面向卷绕系统的大行程位移精密自动测量计米方法,以双同步齿形带传动副作为精确夹持传送装置,同时采用主动驱动计米与从动轮计米,主动轮由带编码器的交流伺服电机驱动,从动轮计米采用霍尔齿轮转速传感器,可减小同步带轮打滑引起的测量误差。经分析同步带传动多边形效应引起的直线传动位移误差,提出采用加厚聚氨酯圆弧齿同步带以提高测量精度,提出了一种同步带打滑检测及误差修正方法。该方法已用于某型飞机试飞空气静压测量拖锥自动收放系统线缆收放位移检测,结果证明,该方法原理正确可行,位移测量误差不大于0.2%。

关键词：卷绕系统精密自动测量同步带传动夹持传送机构主动轮计米从动轮计米霍尔齿轮转速传感器