Mohamed Mouhib , Rodica Chiriac , François Toche , Jean-Jacques Counioux , Joseph Saab , Mohammed Kaddami , Christelle Goutaudier
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引用次数: 0
摘要
为了了解这两种化合物的结晶条件并强调它们可能存在的多态性,我们重新开始了对正磷酸和焦磷酸形成的体系的研究。为此,对焦磷酸的固液平衡(SLE)进行了深入研究。通过系统的实验:溶解度测量、差示扫描量热法(DSC)和 X 射线衍射法(XRD),解决了文献数据中的矛盾之处。量热测量证实了焦磷酸两种结晶形式的存在,并确定了它们的稳定域。此外,通过对 SLE 进行热力学建模,对观察到的现象进行了一致而精细的描述。特别是,确定了焦磷酸从低温形态(形态 I)到高温形态(形态 II)的转变温度为 298.4 K,并精确确定了 HPO 和 HPO (I) 之间共晶点的坐标。建模还证实,在几乎整个成分范围内,液态三磷酸的数量都不可忽略。最后,使用 EXPO 2014 软件,利用 X 射线粉末衍射数据确定了焦磷酸的晶胞参数和空间群。
Liquid and crystallized phases stability in the sub-system H3PO4H4P2O7: Experimental determination and modeling
The study of the system formed by ortho- and pyrophosphoric acid was resumed in order to understand the crystallization conditions of these two compounds and to highlight the existence of their possible polymorphism. To this end, the solid-liquid equilibria (SLE) of pyrophosphoric acid was studied in depth. Contradictions in literature data were resolved through systematic experimentation: solubility measurements, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Calorimetric measurements confirmed the existence of two crystalline forms of pyrophosphoric acid, and their stability domains were determined. Furthermore, thermodynamic modeling of the SLE has led to a consistent and refined representation of the observed phenomena. In particular, the transition temperature from low-temperature (form I) to high-temperature form (form II) of pyrophosphoric acid was determined at 298.4 K and the coordinates of the eutectic point common between H3PO4 and H4P2O7 (I) were precisely determined. Modeling also confirms the non-negligible quantity of triphosphoric acid in the liquid state throughout virtually the entire compositional range. Finally, X-ray powder diffraction data were used to determine the cell parameters and space group of pyrophosphoric acid using EXPO 2014 software.
期刊介绍:
Thermochimica Acta publishes original research contributions covering all aspects of thermoanalytical and calorimetric methods and their application to experimental chemistry, physics, biology and engineering. The journal aims to span the whole range from fundamental research to practical application.
The journal focuses on the research that advances physical and analytical science of thermal phenomena. Therefore, the manuscripts are expected to provide important insights into the thermal phenomena studied or to propose significant improvements of analytical or computational techniques employed in thermal studies. Manuscripts that report the results of routine thermal measurements are not suitable for publication in Thermochimica Acta.
The journal particularly welcomes papers from newly emerging areas as well as from the traditional strength areas:
- New and improved instrumentation and methods
- Thermal properties and behavior of materials
- Kinetics of thermally stimulated processes