NH4Cl水溶液的微观结构和宏观物性研究

通过拉曼光谱、同步辐射X射线散射和密度泛函理论(DFT)模拟,研究了质量分数为1.0 %-28.0 %的NH₄Cl水溶液的微观结构变化。同时在室温下测量了粘度、接触角和电导率。由拉曼光谱和密度泛函理论模拟结果可知,当溶质浓度升高至10.0 %时,在2900 cm_-1^和3100 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水溶液中的氢键类型发生了转变。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2.98 ?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。对}NH₄Cl水溶液的宏观物性研究表明,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。作者推断,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_-^{接触离子对},是粘度和接触角随溶质浓度增加而增加的微观本质因素；电导率的增加与溶液中有效导电离子数量增加有关。

Study on the Microstructure and Macroscopic Physical Properties of NH4Cl Aqueous Solution

Through Raman spectroscopy, synchrotron radiation X-ray scattering, and density functional theory (DFT) simulations, the microstructure changes of NH4Cl aqueous solution with mass fraction of 1.0 %-28.0 % were studied. Viscosity, contact angle, and conductivity were also measured at room temperature. From the simulation results of Raman spectroscopy and density functional theory, when the solute concentration increased to 10.0 %, there was a significant N-H peak near 2900 cm-1 ^{and 3100 cm}-1^{, and with the increase} in mass fraction, the hydrogen bond type in the Aqueous NH4Cl solution changed regularly. X-ray scattering results showed that the reduced pair distribution function G(r) showed a clear double peak near 2.98 ? when the mass fraction of aqueous NH4Cl solution was increased to 10.0 %, indicating that the NH4+^-Cl- contact ion pair started to become the dominant microscopic interaction in the solution at this concentration. The macroscopic physical properties of aqueous NH4Cl solutions showed that viscosity, contact angle, and conductivity increased with the increasing mass fraction of aqueous NH4Cl solutions. The authors inferred that the shift in the type of hydrogen bonding in aqueous NH4Cl solutions, the O-H...N bonding occupancy, and the progressively increasing NH4+^-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.