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Showing 2 results for Phase Diagram

M. Goodarzi, P. Mohammadpoor,
Volume 36, Issue 3 (11-2017)
Abstract

In this study, the phase diagram and thermodynamic properties of Ti-O system up to 30 mole percent of oxygen was calculated with Calphad method. In this range of oxygen, Ti-O system includes αTi, βTi and liquid phases. αTi and βTi were modeled by “sublattice” model and the model of liquid phase was modeled by “ionic liquid”. Gibbs energy parameters of each phase was optimized by Thermo-Calc software and their phase and thermodynamic diagrams were drawn using this software. The obtained results were compared with experimental and other calculated results. A good accordance was observed between calculated and experimental results. In calculation of phase diagram, with increasing temperature and mole fraction of oxygen, the use of “ionic liquid” model instead of “sublattice” model in thermodynamic description of liquid phase showed better accordance with experimental data.

S. Solgi, M. Jafar Tafreshi, M. Sasani Qhamsari,
Volume 38, Issue 1 (6-2019)
Abstract

The synthesis of calcium tetraborate was investigated in a temperature ranging from 800℃ to 900℃ using the solid-state reaction method. The synthesis was done using ammonium tetraborate tetrahydrate as the source of boron. At temperatures of 800 ℃ and 880 ℃, the mixed phases from different compounds were formed. At the optimum temperature of 840℃, the mixed phase was only composed of meta and tetraborate phases. A 2wt% excess of ammonium tetraborate tetrahydrate led to the calcium tetraborate phase formation. X-ray diffraction analysis (XRD) confirmed the monoclinic structure at the optimum temperature of 840℃ and by 2wt% excess of ammonium tetraborate tetrahydrate. Formation of BO3 and BO4 units  composition and morphology of the prepared sample were studied by Field emission scanning electron microscopy (FE-SEM). The stoichiometry of the prepared powders was almost the same as the theoretical amounts, and powder particles exhibited some monoclinic characteristics.


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