空间高温实时观察装置（SHITISOI）被用于观察和记录在Li2B4O7溶体中KNbO3胞状结晶的整个生长过程，并对胞状结晶生长过程中浮力对流和表面张力对流的影响进行了研究．首次观察到空间条件下，Li2B4O7溶体中稳态表面张力对流图像，它呈镜面对称的抛物线状．由于表面张力对流的作用，KNbO3胞晶生长且充满了整个的溶体．而在地面上，由于浮力抑制表面张力，降低了胞晶在流体中的生长速度，使溶质KNbO3胞晶在Li2B4O7溶体中分布不均匀，本文还提出了胞状结晶生长理论的模型．这个模型的主要特点是表面张力对流起始于KNbO3胞晶的界面上；这是由于KNbO3溶质扩散速率减少而引起的KNbO3溶质表面张力梯度．本模型的预言和实验所观察的现象吻合得比较好，这说明该理论模型是合理、可靠的．
Space High Temperature In Situ Observation Instrument “SHITISOI” was dedicated to visualize and record the
whole KNbO3 cellular growth process in Li2B4O7 flux. The dependence of buoyancy and surface tension convections on the cellular
growth was studied. In space, the streamlines of the steady surface tension convections in the Li2B4O7 flux were observed. The steady
convections occur in the form of a mirror symmetric pattern. Due to the surface tension convection, the KNbO_3 grains grow and fill the whole
solution homogeneously. On the ground, the buoyancy drive flow in direction opposite to that of surface tension flow can reduce the cellular growth
and the distribution of KNbO3 solute grains is inhomogeneous in the Li2B4O7 flux. A theoretical model of cellular growth was also
accounted. A pivotal feature in this model is the initiation of the surface tension convection on the interface of KNbO3 grain. This is initiated
by KNbO3 solute surface tension gradient which is caused by less rapid diffusion of KNbO3 solutes. Direct comparison of the model predictions
and experimental observed phenomena demonstrates the predictive capability of this model.
参考文献
| [1] | Benard H. Rev. Gen. Sci. Pure Appl., 1900, 11: 1261--1263, 1309--1311. [2] Benard H. Ann. Chim. Phys., 1901, 23: 62--64. [3] Chai A T, Zhang N. Proc. 3rd Microgravity Fluid Physics Conf., NASA Conference Publication, 1996, 3338: 521--526. [4] Lord Rayleigh. Phil. May., 1916, 32: 529--531. [5] Block M J. Nature, 1956, 178: 650--652. [6] Pearson J R A. J. Fluid Mech., 1958, 4: 489--492. [7] Nield D A. J. Fluid Mech., 1964, 16: 341--344. [8] Jin W Q, Pan Z L, Liu Z H, et al. Microgravity Science and Technology, 1997, 4: 194--196. [9] Jin W Q, Chen J Y, Li W S, et al. Ferroelectrics 1993, 142: 13--18. [10] Jin W Q, Pan Z L, Liu Z H, et al. Proceedings of Joint 1st Pan-Pacific Basin Workshop and 4th Japan-China Workshop on Microgravity Sciences, J. Jpn. Soc. Microgravity Appl. 15, Supplement II 1998. 566--570. [11] Jin W Q, Chen J Y, Li W S. Microgravity Quarterly, 1993, 3: 129--133. [12] 金蔚青, 蒋元方, 孙绪宝等(JIN Wei-Qing, et al). 无机材料学报(Journal of Inorganic Materials), 1998, 13: 291--295. |
- 下载量()
- 访问量()
- 您的评分：
-
10%
-
20%
-
30%
-
40%
-
50%