The solid-liquid interface motion of NaBi（WO4）2 （NBWO） melt crystal growth is observed in an in situ system, in which the whole processes of interface transition from fiat interface and cellular to dendrite are vi...The solid-liquid interface motion of NaBi（WO4）2 （NBWO） melt crystal growth is observed in an in situ system, in which the whole processes of interface transition from fiat interface and cellular to dendrite are visualized. The spacing of the dendrite under smaller temperature gradient turns out to be larger than that under larger temperature gradient, which is found to be sensitive to the temperature distribution. The mechanism of dendrite growth of NBWO is studied based on the model of the growth units of anion coordination polyhedra. The { 001} face has two apex links, so it shows higher stability and has high growth rate and forms the arm of dendrite, whereas the {010} face has only one apex link, and thus shows relative slower growth rate and firstly forms the branches.展开更多
The Schlieren technique coupling with a differential interference microscope was applied to visualize the KNbO_(3) melt motion in a loop-shaped Pt wire heater.The natural convection in KNbO_(3) melt was traced by obse...The Schlieren technique coupling with a differential interference microscope was applied to visualize the KNbO_(3) melt motion in a loop-shaped Pt wire heater.The natural convection in KNbO_(3) melt was traced by observing the movement of the tiny KNbO_(3) crystals(~10μm)and the stream velocities of these tracer crystals were measured.In theoretical analysis,the Navier--Stokes equation was solved as a stable field.The general solution for this system of the differential equation was expressed by an approximate power series of azimuth and radius vector.The expression was substituted in the differential equation;a non-trivial solution was obtained exactly.The velocity distribution in the vertical section was obtained which is in qualitative agreement with the experimental result.展开更多
We have investigated experimentally and theoretically the thermocapillary convective flow phenomena in a loop-shaped Pt wire heater of KNbO_(3)(20wt.%)and Li_(2)B_(4)O_(7) solution.Optical evaluations in connection wi...We have investigated experimentally and theoretically the thermocapillary convective flow phenomena in a loop-shaped Pt wire heater of KNbO_(3)(20wt.%)and Li_(2)B_(4)O_(7) solution.Optical evaluations in connection with thermocouple measurements made it possible to get a new type of thermocapillary convective flow in the considered system.To study the kinematical behavior of thermocapillary convection,we have measured the stream velocities of flow.In a theoretical analysis,the flow velocity due to thermocapillary effect alone was estimated by balancing the surface tension forces by viscous forces.The velocity distribution in the solution near the margin of the heater was obtained,which is in agreement with the experimental result.展开更多
We have investigated experimentally and theoretically the thermocapillary convec tive flow phenomena in a loop-shaped Pt wire heater of KNbO_(3)(20wt.%)and Li_(2)B_(4)O_(7) solutions.Optical evaluations in connection ...We have investigated experimentally and theoretically the thermocapillary convec tive flow phenomena in a loop-shaped Pt wire heater of KNbO_(3)(20wt.%)and Li_(2)B_(4)O_(7) solutions.Optical evaluations in connection with thermocouple measure ments made it possible to get a new type of thermocapillary convective flow in the considered system.To study the kinematical behaviour of thermocapillary convec tion,we have measured the stream flow velocities.In a theoretical analysis,the flow velocity due to the thermocapillary effect alone was estimated by balancing the sur face tension forces by viscous forces.The velocity distribution in the solution near the margin of the heater was obtained,which is in agreement with the experimental result.……展开更多
The Schlieren technique coupling with a differential interference microscope was applied to visualize the KNbO3 melt motion in a loop-shaped Pt wire heater. The natural convection in KNbO3 melt was traced by obser... The Schlieren technique coupling with a differential interference microscope was applied to visualize the KNbO3 melt motion in a loop-shaped Pt wire heater. The natural convection in KNbO3 melt was traced by observing the movement of the tiny KNbO3 crystals (～10μm) and the stream velocities of these tracer crystals were measured. In theoretical analysis, the Navier-Stokes equation was solved as a stable field. The general solution for this system of the differential equation was expressed by an approximate power series of azimuth and radius vector. The expression was substituted in the differential equation; a non-trivial solution was obtained exactly.The velocity distribution in the vertical section was obtained which is in qualitative agreement with the experimental result.……展开更多
Experimentally, it was observed that there were various morphologies of KNbO3 crystals in different regions of the melt of Li2B4O7 and KNbO3 mixture in Pt loop heater. Dendrites grew in the central area of the mel... Experimentally, it was observed that there were various morphologies of KNbO3 crystals in different regions of the melt of Li2B4O7 and KNbO3 mixture in Pt loop heater. Dendrites grew in the central area of the melt, the diffusive-advective region,in which the temperature gradient is negligible; whereas crystals with smooth sur face were observed in the marginal area, the diffusive-convective region, with large temperature gradient. Based on the solute concentration over the KNbO3 crystal surface examined by electronic probe analysis, it was proved that the combinative effect of buoyancy and surface tension convection induced by temperature gradient enhanced the homogeneity of the solute concentration around KNbO3 crystals and thus their morphological stability.……展开更多
Experiments on the thermocapillary convection of high temperature Bi12SiO20 melts have been carried out in the in situ observation system. The steady flow pattern comprises of the main trunk and branches, which is dee...Experiments on the thermocapillary convection of high temperature Bi12SiO20 melts have been carried out in the in situ observation system. The steady flow pattern comprises of the main trunk and branches, which is deemed as the surface deformation. The oscillatory thermocapillary convection is characterized by the oscillatory main trunk and traveling branches. The transition of the melt from steady spatial to oscillatory behavior under the temperature differences 120, 60 and 10 K has been considered. The free surface deformation is observed to transform with the change of the applied temperature difference, which manifests that the thermocapillary convection is sensitive to the temperature difference. Moreover, taking the temperature distribution into account, it is noted that the deformation is formed in the colder area of the melt. The oscillatory frequency of the main trunk, which is also sensitive to the applied temperature difference, increases with the rise of temperature.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 50331040, and the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KJCXZ-SW-105-03.
文摘The solid-liquid interface motion of NaBi（WO4）2 （NBWO） melt crystal growth is observed in an in situ system, in which the whole processes of interface transition from fiat interface and cellular to dendrite are visualized. The spacing of the dendrite under smaller temperature gradient turns out to be larger than that under larger temperature gradient, which is found to be sensitive to the temperature distribution. The mechanism of dendrite growth of NBWO is studied based on the model of the growth units of anion coordination polyhedra. The { 001} face has two apex links, so it shows higher stability and has high growth rate and forms the arm of dendrite, whereas the {010} face has only one apex link, and thus shows relative slower growth rate and firstly forms the branches.
基金Supported by a grant for key research project of microgravity science from the State Science and Technology Commission of China(95-Yu-34)the National Natural Science Foundation of China under Grant No.59832080National Space Development Agency of Japan(NASDA).
文摘The Schlieren technique coupling with a differential interference microscope was applied to visualize the KNbO_(3) melt motion in a loop-shaped Pt wire heater.The natural convection in KNbO_(3) melt was traced by observing the movement of the tiny KNbO_(3) crystals(~10μm)and the stream velocities of these tracer crystals were measured.In theoretical analysis,the Navier--Stokes equation was solved as a stable field.The general solution for this system of the differential equation was expressed by an approximate power series of azimuth and radius vector.The expression was substituted in the differential equation;a non-trivial solution was obtained exactly.The velocity distribution in the vertical section was obtained which is in qualitative agreement with the experimental result.
基金Supported by the Foundation for Kay Research Project of Microgravity Science of the State Science and Technology Commission of China(95-Yu-34)the National Natural Science Foundation of China under Grant No.59832080National Space Development Agency of Japan(NASDA).
文摘We have investigated experimentally and theoretically the thermocapillary convective flow phenomena in a loop-shaped Pt wire heater of KNbO_(3)(20wt.%)and Li_(2)B_(4)O_(7) solution.Optical evaluations in connection with thermocouple measurements made it possible to get a new type of thermocapillary convective flow in the considered system.To study the kinematical behavior of thermocapillary convection,we have measured the stream velocities of flow.In a theoretical analysis,the flow velocity due to thermocapillary effect alone was estimated by balancing the surface tension forces by viscous forces.The velocity distribution in the solution near the margin of the heater was obtained,which is in agreement with the experimental result.
文摘We have investigated experimentally and theoretically the thermocapillary convec tive flow phenomena in a loop-shaped Pt wire heater of KNbO_(3)(20wt.%)and Li_(2)B_(4)O_(7) solutions.Optical evaluations in connection with thermocouple measure ments made it possible to get a new type of thermocapillary convective flow in the considered system.To study the kinematical behaviour of thermocapillary convec tion,we have measured the stream flow velocities.In a theoretical analysis,the flow velocity due to the thermocapillary effect alone was estimated by balancing the sur face tension forces by viscous forces.The velocity distribution in the solution near the margin of the heater was obtained,which is in agreement with the experimental result.……
文摘 The Schlieren technique coupling with a differential interference microscope was applied to visualize the KNbO3 melt motion in a loop-shaped Pt wire heater. The natural convection in KNbO3 melt was traced by observing the movement of the tiny KNbO3 crystals (～10μm) and the stream velocities of these tracer crystals were measured. In theoretical analysis, the Navier-Stokes equation was solved as a stable field. The general solution for this system of the differential equation was expressed by an approximate power series of azimuth and radius vector. The expression was substituted in the differential equation; a non-trivial solution was obtained exactly.The velocity distribution in the vertical section was obtained which is in qualitative agreement with the experimental result.……
文摘 Experimentally, it was observed that there were various morphologies of KNbO3 crystals in different regions of the melt of Li2B4O7 and KNbO3 mixture in Pt loop heater. Dendrites grew in the central area of the melt, the diffusive-advective region,in which the temperature gradient is negligible; whereas crystals with smooth sur face were observed in the marginal area, the diffusive-convective region, with large temperature gradient. Based on the solute concentration over the KNbO3 crystal surface examined by electronic probe analysis, it was proved that the combinative effect of buoyancy and surface tension convection induced by temperature gradient enhanced the homogeneity of the solute concentration around KNbO3 crystals and thus their morphological stability.……
基金This work was supported by the National Natural Science Foundation of China(Grant No.5033 1040)the Innovation Funds from the Chinese Academy of Sciences(Grant No.KJCXZ-SW-105-03).
文摘Experiments on the thermocapillary convection of high temperature Bi12SiO20 melts have been carried out in the in situ observation system. The steady flow pattern comprises of the main trunk and branches, which is deemed as the surface deformation. The oscillatory thermocapillary convection is characterized by the oscillatory main trunk and traveling branches. The transition of the melt from steady spatial to oscillatory behavior under the temperature differences 120, 60 and 10 K has been considered. The free surface deformation is observed to transform with the change of the applied temperature difference, which manifests that the thermocapillary convection is sensitive to the temperature difference. Moreover, taking the temperature distribution into account, it is noted that the deformation is formed in the colder area of the melt. The oscillatory frequency of the main trunk, which is also sensitive to the applied temperature difference, increases with the rise of temperature.
