“蒸发成核法”研究KDP晶核大小及形状

Research on the nucleus of KDP by a method named "nucleation from droplet by evaporation"

提出一种有望用于研究临界或近临界晶核大小及形状的新方法,借助于原子力显微镜(AFM),对磷酸二氢钾(KDP)晶核的大小以及形状进行了研究。结果表明,应用"蒸发成核法"可得到纳米尺寸的晶核,随溶液浓度的增大,晶核直径从25.8nm增大至59.1nm。其中最小尺寸的晶核,与低过饱和度下的理论预测值较接近。一般情况下,晶核呈球缺型,与经典理论假设形状相符。但蒸发温度低时,晶核可呈矩形(柱状),与KDP晶体的宏观形状更为接近。在蒸发速度较快时,晶核难以形成,只会出现溶质的堆积体。

A new method which can be used to investigate the critical nucleus or the near-critical nucleus was proposed in present paper.The size and shape of the nucleus of potassium dihydrogen phosphate（KDP）were investigated by atomic force microscopy（AFM）.The experimental results show that nuclei with nm dimension can be obtained by this new method named＂nucleation from droplet by evaporation＂.The average diameter of the nuclei increases from 25.8 to 59.1nm with the increase of solution concentration.The size of the minimum nucleus gets close to the value of critical nucleus presumed by classical nucleation theory under the condition of low solution concentration.Generally speaking,the nucleus shows itself as a segment,which is in accordance with the classical nucleation theory.But when the temperature of evaporation is low,the nucleus exhibits a rectangle（pillar）,which is similar to the shape of macroscopical crystal.When the speed of evaporation is fast,nucleuses could not form.There only leaves accumulation of solute.