NH4Cl水溶液的结构和物性研究

Microstructure and Physical Properties of NH4Cl Aqueous Solution

中文关键词:  NH₄Cl水溶液  密度泛函理论  拉曼光谱  同步辐射X射线散射

英文关键词:Aqueous NH₄Cl solution  Density functional theory  Raman spectroscopy  Synchrotron radiation X-ray scattering

中文摘要:

      通过密度泛函理论(DFT)计算、拉曼光谱和同步辐射X射线散射法,研究了质量分数为1.0 %～28.0 %的NH₄Cl水溶液的微观结构。在室温下测量了粘度、接触角和电导率。由DFT计算和拉曼光谱结果可知,当溶质浓度升高至10.0 %时,在2 900 cm-1和3 100 cm-1附近出现了明显的N-H作用峰,且随着质量分数的升高,NH₄Cl水溶液中的DDAA型氢键转变为DA和DAA型氢键。X射线散射结果表明,当NH₄Cl水溶液质量分数升高至10.0 %时,差值对分布函数G(r)在0.298 nm附近出现明显双峰,表明在该浓度下溶液中NH₄⁺-Cl-接触离子对开始成为主要微观作用形式。NH₄Cl水溶液的粘度、接触角和电导率均随着NH₄Cl水溶液质量分数的增加而增大。NH₄Cl水溶液中氢键类型的转变、O-H...N键占比增多以及逐渐增加的NH₄⁺-Cl-接触离子是粘度和接触角变化的微观本质因素；电导率的增加与溶液中有效导电离子数量增加有关。

英文摘要:

      Density functional theory calculation (DFT),Raman spectroscopy and synchrotron radiation X-ray scattering were employed to study the microstructure of NH₄Cl solution with mass fraction of 1.0%~28.0%. Viscosity,contact angle and conductivity were measured at room temperature. From the results of DFT calculation and Raman spectroscopy,when the solute concentration increases to 10.0%,there are significant N-H peaks near 2 900 cm-1 and 3 100 cm-1,and with the increase of mass fraction,the double donor-double acceptor (DDAA) type hydrogen bonds in the NH₄Cl solution transform into the single donor-single acceptor (DA) and the single donor-double acceptor (DAA) type hydrogen bonds. X-ray scattering shows that the reduced pair distribution functions G(r) have a clear double peak near 2.98  when the mass fraction of aqueous NH₄Cl solution increases to 10.0%,indicating that the NH⁺₄-Cl- contact ion pairs start to become the dominant microscopic interaction in the solution at this concentration. With the increase of the mass fraction of aqueous NH₄Cl solutions,the viscosity,contact angle and conductivity of aqueous NH₄Cl solution increase. The shift in the type of hydrogen bonding in aqueous NH₄Cl solutions,the O-H..N bonding occupancy,and the progressively increasing NH⁺₄-Cl- contact ion pairs are the microscopic essential factors for the increased viscosity and contact angle with increasing solute concentration; the increase in conductivity is related to the increase in the number of effective conducting ions in the solution.