金红石型晶体的非传统晶化行为

发布时间：2018-06-24 17:36

本文选题：非传统晶化 + 金红石　；参考：《浙江大学》2016年硕士论文

【摘要】：晶化在固体化学、生物以及材料科学中都有着根本重要性,是科学中研究最多的过程之一,同时也是具有极大实际价值。在经典的晶体生长理论建立一百多年来,传统成核和热力学/动力学生长模型取得了巨大成功,但现在仍有许多晶化行为是经典理论所无法解释的。并且,过去的晶化研究往往只是局限于表面形貌,未能真正将晶化过程中表面形貌与内部结构演变相结合来研究其生长机理。近些年来,聚焦离子束微纳加工技术和球差校正电镜技术的发展为同时研究微米级颗粒内/外结构提供了可能。本文主要利FIB和TEM技术来研究非平衡条件下金红石晶体的晶化过程,特别是表面/内部结构演变以及该过程中发生的非传统晶体生长行为。FIB和TEM技术的交叉运用使我们能够观察和分析内部结构以及缺陷的变化,结合观察到的表面结构演变,我们对金红石晶体的非传统生长机理有更加深入的了解。具体如下：(1)利用氢氟酸和盐酸的协同吸附效应通过简便的低温水热方法可控制备了一种具有新型曲面的金红石型氧化钛单晶,揭示了该新型曲面表面结构。结合理论计算和实验分析,我们发现封端剂以及实验环境对这种弧形表面的形成和转变有着重大意义。(2)利用聚焦离子束技术以及透射电镜技术去研究曲面金红石TiO2晶体的内部结构,发现了该金红石晶体中存在一种新奇的竞争生长现象,即生长过程中同时存在两种生长模式在三维空间上相互竞争。我们研究了其在二维平面上的生长动力学过程以及三维空间上两种不同生长模式区域的分布,分析了这种竞争生长现象存在的原因,并且成功构造了晶体内部同样具有该竞争生长的曲面SnO2介晶。该工作首次展示了一种晶体生长过程中同时存在平衡和非平衡两种生长模式,并半定量地描述两种生长模式的动力学过程。(3)引入了一种预接种的处理方法去研究一种新型的胶囊状的金红石TiO2介晶的生长初期的非传统晶化行为,发现其可能是由先形成的介孔纳米棒团簇定向自组装而成。生长初期出现的那纳米胶囊雏形以及晶体连接过程中初级颗粒轻微取向失配现象强有力地证明了定向聚集这一生长行为的存在。
[Abstract]:Crystallization is of fundamental importance in solid chemistry, biology and material science. It is one of the most studied processes in science and has great practical value. Since the classical crystal growth theory has been established for more than 100 years, the traditional nucleation and thermodynamic / kinetic growth models have achieved great success, but there are still many crystallization behaviors that cannot be explained by the classical theory. Moreover, in the past, the study of crystallization was usually confined to the surface morphology, and the growth mechanism was not really studied by combining the surface morphology with the evolution of internal structure in the process of crystallization. In recent years, the development of focused ion beam microfabrication and spherical aberration correction electron microscopy has made it possible to study the inner / outer structure of micron particles simultaneously. In this paper, the crystallization process of rutile crystals under non-equilibrium conditions is studied by using LiFIB and TEM techniques. In particular, the surface / internal structure evolution and the cross-use of non-traditional crystal growth behavior. FIB and TEM techniques during this process enable us to observe and analyse the changes in internal structure and defects, and to combine the observed surface structure evolution. We have a better understanding of the unconventional growth mechanism of rutile crystals. The main results are as follows: (1) A rutile titanium oxide single crystal with a new surface can be controlled by using the synergistic adsorption effect of hydrofluoric acid and hydrochloric acid. The surface structure of the new surface is revealed. Combined with theoretical calculation and experimental analysis, We find that the capping agent and experimental environment are of great significance to the formation and transformation of the curved surface. (2) the internal structure of the curved rutile TiO2 crystal is studied by focusing ion beam technique and transmission electron microscopy. It is found that there is a novel competitive growth phenomenon in the rutile crystal, that is, there are two growth modes competing with each other in the three dimensional space during the growth process. In this paper, we study the dynamic process of growth in two-dimensional plane and the distribution of two different growth modes in three dimensional space, and analyze the reason why the competitive growth phenomenon exists. The surface Sno _ 2 mesocrystals with the same competitive growth in the crystal have been successfully constructed. This work shows for the first time that there are both equilibrium and non-equilibrium growth patterns in the process of crystal growth. The kinetic processes of the two growth modes were described semi-quantitatively. (3) A preinoculation method was introduced to study the unconventional crystallization behavior of a new type of capsule rutile TiO2 mesocrystalline in the early stage of growth. It is found that it may be formed by self-assembly of mesoporous nanorods. The initial appearance of the nanocapsule and the slight misalignment of the primary particles in the process of crystal joining strongly prove the existence of the growth behavior of the directional aggregation.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O614.411;O782

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