Harry Reid Center for Environmental Studies, University of Nevada, Las Vegas, Box 454009, 4505 Maryland Parkway, Las Vegas, Nevada 89154, USA.
Inorg Chem. 2009 Jul 6;48(13):5736-46. doi: 10.1021/ic900632g.
Synthesis of (NH(4))(4)ThF(8) by a solid state reaction of ThO(2) and NH(4)HF(2) and the formation of ThNF by ammonolysis of (NH(4))(4)ThF(8) and ThF(4) under different experimental conditions were investigated. The solid state reaction of ThO(2) with NH(4)HF(2) led to the terminal product (NH(4))(4)ThF(8) through a known intermediate (NH(4))(3)ThF(7) and most likely two other unknown chemical phases as determined by X-ray powder diffraction. Conversion of (NH(4))(4)ThF(8) into ThNF occurs through a ThF(4) intermediate phase. Studies on the ammonolysis of ThF(4) revealed it converted into ThNF through a continuous formation of low-stoichiometric thorium-nitride-fluorides such as ThN(0.79)F(1.63) and ThN(0.9)F(1.3). Thermal behavior of ThNF was also examined under different atmospheres and temperatures, with evaluation of formation kinetics. The ThNF decomposed to low-stoichiometric thorium nitride fluorides (ThN(x/3)F(4-x)) under different environments up to 1100 degrees C. Significant morphological changes in the products compared to that of the precursors confirmed the reaction steps involved. Microstructural characterization of (NH(4))(4)ThF(8) and ThNF were performed by HRTEM and are presented in this work for the first time. The (NH(4))(4)ThF(8) product was shown to contain polycrystalline characteristics in the majority of its nanostructure. On the other hand, ThNF has a high order of nanostructure, which explains the high thermal stability of the compound up to 1100 degrees C and the difficulty of making ThN(x), in initial target product, from the described experimental conditions.
通过 ThO2 与 NH4HF2 的固态反应合成 (NH4)4ThF8，以及在不同实验条件下通过 (NH4)4ThF8 和 ThF4 的氨解合成 ThNF 的研究。ThO2 与 NH4HF2 的固态反应通过已知的中间产物 (NH4)3ThF7 和很可能另外两种未知的化学相，导致终端产物 (NH4)4ThF8。通过 X 射线粉末衍射确定。(NH4)4ThF8 转化为 ThNF 是通过 ThF4 中间相进行的。对 ThF4 氨解的研究表明，它通过连续形成低化学计量的钍氮氟化物，如 ThN(0.79)F(1.63)和 ThN(0.9)F(1.3)，转化为 ThNF。还在不同气氛和温度下研究了 ThNF 的热行为，并评估了形成动力学。在不同的环境中，ThNF 分解为低化学计量的钍氮氟化物（ThN(x/3)F(4-x)），温度高达 1100°C。与前体相比，产物的形貌发生了显著变化，证实了所涉及的反应步骤。通过 HRTEM 对 (NH4)4ThF8 和 ThNF 进行了微观结构表征，并首次在本工作中进行了介绍。(NH4)4ThF8 产物在其大部分纳米结构中表现出多晶特性。另一方面，ThNF 具有高度有序的纳米结构，这解释了该化合物高达 1100°C 的高热稳定性，以及在描述的实验条件下从初始目标产物中制备 ThN(x)的困难。
