水溶液的液固转变以及玻璃化转变的研究

发布时间：2018-05-11 22:02

本文选题：水溶液 + 玻璃化转变　；参考：《北京科技大学》2017年博士论文

【摘要】：水是地球上最常见之物,也被视为生命之源。尽管水分子结构简单,但这并不意味着水简单或容易理解。相反,由于液态水中存在皮秒量级内打开和形成的氢键,几乎水所有的性质都异于寻常液体,因此水也被誉为最复杂的液体。水参与各种物理、化学和生命过程,对水的研究是理解自然种种奥秘的关键。然而,到目前为止我们对水所知甚少。直接对纯水展开研究十分困难,但水溶液的研究则相对简单。尽管溶质的引入会使得水变得更加复杂,但水溶液的多种性质都与溶质类型和浓度密切相关,低温水溶液的热力学和动力学性质往往蕴含丰富的物理图像。水溶液的晶化和玻璃化是水科学领域的研究热点及难点之一。本文通过差示扫描量热仪、宽频介电谱以及拉曼光谱等实验手段研究多种常见电解质、有机物二元水溶液、电解质和有机物的三元混合水溶液以及受限水溶液的液-固转变和玻璃化转变行为,本论文的主要研究内容如下:(1)通过系统的对多种水溶液玻璃化转变行为的测量,发现水溶液的玻璃化转变温度(T_g)对水的质量分数浓度(X_(aqu))有普适的依赖关系,并依据此关系把水溶液分为三个浓度区域。当X_(aqu) X_(aqu)~(cr)时(1区),水溶液的T_g是一个与浓度无关的常数T_g~',发生玻璃化转变的成分为冰析出后浓度为X_(aqu)~'的浓缩相水溶液;当X_(aqu)X_(aqu)~(cr)时,水溶液完全玻璃化,其T_g随X_(aqu)增加单调递减(Ⅱ区:X_(aqu)~(cr)X_(aqu)X_(aqu)~', Ⅲ区:X_(aqu)X_(aqu)~')。根据三个浓度区域内水溶液的液-固转变和玻璃化转变行为,我们将浓度为X_(aqu)~'和X_(aqu)~(cr)的水溶液中水与溶质的摩尔比nh和化ncr分别定义为溶质的结合水数和最大(临界)结合水数。确定了溶质的结合水数,同时也就确定了水溶液中自由水的含量。我们发现自由水的质量分数(x_f)可以普适的描述电解质和小分子有机物水溶液的均质形核温度(T_H)、冰的熔化温度(T_m)以及相应水溶液的活度(a_w)。此外,X_f与T_H、T_m和a_w的关系对压力条件下的纯水和水溶液依然有效。(2)水的液-液相变是水科学领域内的一个充满争议的热门话题。最近,有课题组基于一些特定浓度的水溶液经过退火处理后T_g的变化断言水溶液中确实存在水的液-液相变。我们发现他们提出的特定浓度的水溶液均处于区浓度范围内。经过对Ⅱ区浓度范围内水溶液的细致研究发现,样品退火前后T_g的变化是由于水溶液经过再结晶后浓度变化引起的,而不是由于水溶液中的高密度水变为低密度水即液-液相变造成的。(3)含有可晶化结合水的水溶液的玻璃化转变和再结晶现象通常纠缠在一起,这不仅给实际应用带来困难还经常造成相关实验解释上的误解。我们根据水溶液玻璃化转变温度与浓度的关系提出了一个确定可晶化结合水含量的方法,并对可能发生再结晶现象的水溶液的浓度给出了一个明确的界定。我们还发现可晶化结合水的性质与其含量相关,根据可晶化结合水的含量需要设计不同实验方案才能使其完全析出晶化。(4)通过对多种二元水溶液和三元混合水溶液体系的结合水数(n_h)和临界结合水数(n_(cr))的测量,我们发现电解质水溶液中的n_(cr)/n_h～1.7,有机物水溶液中的n_(cr)/n_h依赖于溶质类型且明显大于电解质水溶液,除氯化锌以外的氯化物和甘油三元混合水溶液的n_(cr)~(mix)/n_h~(mix)均处于电解质水溶液与甘油水溶液之间。通过测量溶质结合水数随水溶液浓度的变化,揭示了甘油、氯化锌和水三者间的多体相互作用,发现甘油与氯化锌之间的相互作用同时依赖于甘油和水的含量。并依此提出一种探讨混合溶质水溶液中多体相互作用的方法。(5)体相氯化钠水溶液玻璃形成能力弱,只有在高压环境下才能玻璃化。通过测量受限于不同孔径纳米孔内氯化钠水溶液的玻璃化转变行为,讨论受限尺寸和受限载体内表面的浸润性对氯化钠水溶液玻璃形成能力的影响,发现受限尺寸效应是导致氯化钠水溶液玻璃化的主要原因,并提出了一个模型来解释受限氯化钠水溶液的玻璃化转变行为对临界浓度的依赖性。
[Abstract]:Water is the most common thing on earth and is also considered as the source of life. Although the structure of water is simple, it does not mean that water is simple or easy to understand. On the contrary, almost all the properties of water are different from ordinary liquids because of the hydrogen bonds that are opened and formed in the picosecond order of magnitude in liquid water, so water is also known as the most complex liquid. Water is involved in each water. The study of water is the key to understanding the mysteries of nature. However, we know little about water so far. It is difficult to study pure water directly, but the study of water solution is relatively simple. Although the introduction of the solute will make the water more complex, the various properties of the aqueous solution are all with the solute. Types and concentrations are closely related. The thermodynamic and kinetic properties of low temperature aqueous solutions often contain rich physical images. Crystallization and vitrification of aqueous solutions are one of the hotspots and difficulties in the field of water science. In this paper, a variety of common electrolytes are studied by means of differential scanning calorimeter, broadband dielectric spectroscopy and Raman spectroscopy. In this paper, the main contents of this paper are as follows: (1) the glass transition temperature (T_g) of aqueous solution (T_g) has been found by measuring the glass transition behavior of a variety of aqueous solutions by measuring the glass transition behavior of various aqueous solutions. The concentration (X_ (aqu)) has a universal dependence, and the water solution is divided into three concentration regions according to this relationship. When X_ (aqu) X_ (aqu) ~ (CR) is (1), the T_g of the aqueous solution is a constant T_g~'unrelated to the concentration, and the composition of the glass transition is a concentrated phase aqueous solution of X_ (aqu) ~' after the ice precipitates. The solution is fully vitrified, and its T_g increases monotonically with X_ (aqu) (X_ (aqu) ~ (CR) X_ (aqu) X_ (aqu) X_ (aqu) ', III region: X_ (aqu)). The number of combined water and the maximum (critical) water number are defined as the solute. The number of water in the solute is determined and the free water content in the aqueous solution is determined. We found that the mass fraction of the free water (x_f) can be used to describe the homogeneous nucleation temperature (T_H) of the electrolyte and the water solution of the small molecule organic matter (T_m), and the melting temperature of the ice (T_m) and The activity of corresponding aqueous solutions (a_w). In addition, the relationship between X_f and T_H, T_m and a_w is still effective for pure water and aqueous solutions under pressure conditions. (2) liquid liquid phase transition in water is a controversial hot topic in water science. Recently, the group based on the changes of some specific concentration of aqueous solution after annealing treatment of T_g asserted water solubility. There is a liquid liquid phase transition in the liquid. We find that the specific concentration of water solution they put forward is in the range of concentration. After careful study of the water solution in the concentration range of the second region, the change of T_g before and after the annealing is due to the concentration change after the water solution is recrystallized, not the high of the water solution. The change of density water into low density water is caused by liquid liquid phase transformation. (3) the glass transition and recrystallization of aqueous solutions containing crystallizable water are usually entangled together, which not only brings difficulties to practical applications but also often causes misunderstandings in relevant experimental explanations. We suggest that the relationship between temperature and concentration of glass transition in aqueous solution is based on the relationship between the glass transition temperature and the concentration of aqueous solution. A method for determining the content of the crystallizable binding water is determined and a definite definition is given to the concentration of the aqueous solution that may be recrystallized. We also found that the properties of the crystallizable binding water are related to its content. According to the content of the crystallizable binding water, different testing schemes can be designed to crystallize them completely. (4) through the crystallization of the crystallizable binding water For the measurement of the combined water number (n_h) and the critical combined water number (n_ (CR)) of a variety of two yuan aqueous solutions and three mixed solution systems, we found that the n_ (CR) /n_h ~ 1.7 in the electrolyte solution, n_ (CR) /n_h in the aqueous solution of the organic matter depended on the type of solute and was obviously larger than the electrolyte solution, except for the chloride and glycerol three other than zinc chloride. The n_ (CR) ~ (mix) /n_h~ (mix) of the mixed aqueous solution is between the electrolyte solution and the glycerol solution. By measuring the change of the number of solute combined water with the concentration of water solution, the multibody interaction between glycerol, zinc chloride and water are revealed, and the interaction between glycerol and zinc chloride is found to be dependent on the content of glycerol and water at the same time. In addition, a method is proposed to discuss the interaction of multibody in mixed solute aqueous solution. (5) the glass formation ability of the glass of bulk sodium chloride solution is weak and can be vitrified only in the high pressure environment. By measuring the glass transition behavior of sodium chloride solution confined in different pore sizes, the limited size and the confined body surface are discussed. The influence of wettability on the glass formation ability of sodium chloride aqueous solution is found. It is found that the limited size effect is the main reason for the vitrification of sodium chloride solution, and a model is proposed to explain the dependence of the glass transition behavior on the critical concentration of the restricted sodium chloride solution.

【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O645.16

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