超声波对钨酸铵溶液结晶机制影响的研究

【作者】 谭艳芝；

【导师】 陈启元；

【作者基本信息】 中南大学 ， 物理化学， 2004， 硕士

【摘要】 本文对钨和仲钨酸铵的性质、应用，以及超声波对化学反应过程的影响与其机制进行了全面综述。并在此基础上进行了超声波对钨酸铵溶液结晶机制影响的系统研究，主要是研究了超声波对仲钨酸铵晶体的晶型、热化学性质、晶貌、粒度及反应时间的影响，并探讨了钨酸铵溶液结晶过程的宏观机制。 通过蒸发和中和两种不同比重的钨酸铵溶液，在超声波作用下制备含不同结晶水的仲钨酸铵晶体：（NH₄）₁₀W₁₂O₄₁·nH₂O（n=11，7，5）。用X-衍射分析、热重分析和粒度分析，研究并确定了仲钨酸铵的晶型，结果表明同样条件下超声作用后与无超声作用得到相同的晶体，但从X-衍射分析图谱上看出超声作用后所得到的晶体杂峰少，其X衍射分析d／（?）值与文献d／（?）值吻合的更好。超声作用对两种不同比重的钨酸铵溶液的结晶粒度都有明显影响。且超声作用后的仲钨酸铵晶体颗粒比未超声作用的仲钨酸铵晶体颗粒更细小、均匀，晶粒尺寸分布范围更窄。超声对不同比重的钨酸铵溶液出现晶核的时间都有影响，缩短了晶核出现的时间，提高了成核速率，这种影响在低温下更为显著。 从热力学和动力学角度探讨了钨酸铵溶液结晶的宏观机制，从平衡和结晶过程驱动力角度分析了钨酸铵溶液结晶的热力学过程：从晶体生成、晶核形成速率及晶核长大速率等方面研究了钨酸铵溶液结晶的动力学过程。同时，也探讨了超声波对钨酸铵溶液结晶过程影响的宏观机制。更多还原

【Abstract】 The characteristics and applications of tungsten and ammonium paratungstate, and the effect of ultrasonic on chemical process were summarized. The effect of ultrasonic on the crystallization of ammonium tungstate aqueous solution has been investigated systematically based on these. The crystalline form, thermochemistry, crystalline particle and crystalline growth rate were discussed. Macro mechanism of the process of crystallization was analyzed.By evaporating and neutralizing of two ammonium tungstates with different density, crystals of ammonium paratungstate (NH4) 10W12O11 nH2O (n=11, 7, 5) were prepared with ultrasonic. Using XRD, TG, DTG and granularity analysis, the crystalline form was confirmed and researched. The results proved that the effect of ultrasonic on ammonium tungstate was in evidence. The crystalline forms were the same with ultrasonic and without ultrasonic, but impure apexes on the XRD patterns were less and value of d/A more tallied with literature with ultrasonic. Distributing of crystalline granularity became narrower and the crystal was more homogeneous. Ultrasonic shortened the formation time nucleus of crystal.Macro mechanism of the process of crystallization was discussed with thermodynamics and kinetics. Thermodynamics process was analyzed using balance and driving force of crystallization process. Kinetics process were studied using crystal creating, the rate of formation and grow of nucleus. Macro mechanism of the effect of ultrasonic on the crystallization of ammonium paratungstate from aqueous solution was also discussed.更多还原