【作者】 郭晋丽；

【导师】 李明伟；

【作者基本信息】 重庆大学 ， 动力工程及工程热物理， 2010， 硕士

【摘要】 磷酸二氢铵(ADP)是KDP型晶体家族中的一员,作为大尺寸晶体应用于人们的生产实践中由来已久。由于其具有激光倍频效应、电光效应、压电效应等多种特殊功能,所以关于ADP晶体的研究应用一直为人们所关注。对于其研究的热点,主要在于:在保证晶体质量的前提下尽量提高晶体的生长速度、缩短其生长周期、降低成本。近年来,随着人们对ADP晶体特性的深入了解以及对其新用途的开发,ADP晶体在人类生活中也起着越来越重要的作用,所以对其研究也持续不断。不过对于其成核方面虽然前人已经做了一些研究,但是pH值改变后ADP过饱和溶液成核诱导期方面的实验研究及相关计算尚未见有文献报道。另外,到目前为止,通过测量生长速度以对不同pH值下ADP晶体(100)面生长动力学和生长机制的研究尚未见有文献报道。鉴于以上原因,本课题对ADP晶体的生长情况进行实验研究,主要做了以下几个方面的工作:①在30℃到60℃范围内,利用称重法对不同pH值条件下ADP溶液的溶解度进行了实验测定,并给出了相应的溶解度曲线。最后对实验结果进行了分析和解释。②研究了不同pH值下、不同温度的ADP过饱和溶液的成核过程,利用全程摄像的方法测定了不同情况下ADP过饱和溶液的诱导期,讨论了pH值、温度和过饱和比S等因素对诱导期的影响。并根据经典均匀成核理论,针对ADP溶液均匀成核的状况计算出了不同pH值和温度下的固-液界面张力、临界成核半径等成核参数。并通过对上述成核参数的分析,对改变pH值后溶液稳定性加强的微观原因进行了估计。最后通过对计算得到的表面熵因子与理论的比较,确定了ADP晶体的微观生长机制。③对40℃、不同pH值和过饱和度下ADP晶体(100)面的法向生长速度进行了测定。同时,利用实验数据计算出了不同pH值下、二维成核生长机制控制晶体生长时的台阶棱边能。我们也运用原子力显微镜(AFM)非实时观察了不同过饱和度、不同pH值下生长的ADP晶体(100)面的微观形貌,发现与正常pH值相比,在较低的过饱和度下,pH=2.5和pH=5.0的溶液中生长的晶体晶面上就出现了二维核。更多还原

【Abstract】 The large-size ammonium dihydrogen phosphate (ADP) crystal has been applied in production and practice for a long time, which is a member of KDP crystal family. The investigation of ADP crystal attracts more attention for its multiplier effect of laser, electro-optic effect, piezoelectric effect and many other special features. The researches focus on how to maximize crystal’s growth rate, shorten the growth cycle, reduce costs, and improve the quality of the crystal.Recently, with the deep understanding of ADP crystal’s property and the exploitation of new purposes, ADP crystal becomes more and more important in the human beings’life. As a result, the research is continued. However, there is no experimental investigation and related calculations about its induction period by changing pH value although predecessors have done some researches about nucleation of ADP crystal. In addition, so far, the papers that growth kinetics and growth mechanisms of the (100) surface of ADP crystal with different pH values are studied by measuring the growth rate have also not been found. For these reasons, ADP crystal growth experiments were carried out in the present paper. The main works can be summarized as follows:①The solubility of ADP in H2O with different pH values in the temperature range from 30℃to 60℃were determined by weighed method,and the solubility curves are given. At last, the experiment results were explained.②For different pH values,the nucleation of ADP supersaturation solution was investigated at different temperature. The induction period was measured for different growth conditions of ADP solution by the method of photography, and the influence of some factors such as pH value, temperature and supersaturation ratios on the induction period was discussed. According to the classical homogeneous nucleation theory, nucleation parameters such as solid-liquid interfacial tension, radius of critical nucleus and others were calculated using the experimentally determined values of the induction period. The microscopic reason of improving the stability of the ADP solution by changing pH value was also been estimated through the analysis of the nucleation parameters. At last, by comparing the calculated value of the surface entropy factor with theory, the surface growth model of ADP crystal in these experiments was identified.③The growth rates of the (100) face of ADP crystal with different pH values were investigated at different supersaturations at 40℃. And the edge free energy of the (100) face of ADP crystal with different pH values were calculated when the growth was controlled by 2D nucleation mechanism. Finally, the topography of the (100) surface of ADP crystal with different pH values at different supersaturations were observed by ex situ AFM. It was found that there were 2D nucleations appearing in the crystal surface with pH=2.5 and pH=5.0 at lower supersaturations compared with the normal pH.更多还原