摘要
作者采用显微摄影技术对NaNO_3-H_2O系统中的接触成核现象进行了研究,用一个NaNO_3母晶的(100)晶面靠滑动与玻片进行接触。当母晶在饱和溶液中进行接触时,没有接触核形成,但在过饱和溶液中进行接触时,却形成了接触核。这个研究结果说明,必须有一个生长的晶体表面才能形成晶核,母晶的破碎并非晶核的来源。通过连续摄影测出了晶核的成长速率。每粒单晶的成长速率均不随时间而变,但各晶体的成长速率却有所不同,并发现其成长速率受该晶核的初始尺寸及溶液过冷度(即过饱和度)所影响。用线性回归法处理实验数据,分别关联出了在相同过冷度条件下晶体成长速率与初始尺寸的关系。最后再用最小二乘法关联其在各个过冷度条件下所得的结果,得出了NaNO_3接触成核成长速率的数学模型。
Contact nucleation in the sodium nitrate-water system was studied by using a photomicroscopic technique. The (100) face of a parent crystal of sodium nitrate was contacted by sliding along a glase plate. When the parent crystal was contacted while in saturated solution, no nuclei were formed; however, neclei were formed when the parent crystal was contacted in supersaturated solution. These results suggest that a growing crystal surface is necessary for formation of the nuclei and that breakage of the parent crystal is not the source of the nuclei, The growth rates of the nuclei formed were determined from photographs taken at timed intervals. The growth rate of any individual crystal was found to be invariant with time, but the growth rates from crystal to crystal were different. The growth rates of the nuclei were found to be correlated to initial size and to the supercooling. The data obtained under same supercooling were correlated by using linear regressions. The results obtained from linear regressions were treated with least square method, and a mathematic model describing the growth rates of sodinm nitrate contact nuclei were obtained.
关键词
硝酸钠
晶体
接触成核
Sodium nitrate
Contact nuclei
Crystallisation
