Thermodynamic Study On The Phase Diagram In The Al₂O₃-MgO-SiO₂-CaO Oxide System

90%of the mineral components of bulk industrial solid waste exist in the form of aluminosilicate,among which Al₂O₃,MgO,SiO₂,CaO,Fe₂O₃ and Na₂O are important oxide components.The Al₂O₃-MgO-SiO₂-CaO system is the main system of typical industrial solid waste such as gangue and fly ash.The study of phase diagram thermodynamics of this system can provide key basic data for the reconstruction and transformation of solid waste materials.In this work,the phase diagram thermodynamics of the Al₂O₃-MgO-SiO₂-CaO oxide system is studied,during which,the thermodynamic evaluation and calculation combined with key experimental studies are carried out based on CALPHAD method.This work is an important part of constructing the thermodynamic database of the Al₂O₃-MgO-SiO₂-CaO-Fe₂O₃-Na₂O six-component system.The database will serve as an important theoretical basis for the materialization design and high-value application of bulk aluminosilicate solid waste,and therefore provides guidance for industrial process control and research of new materialization methods.The main research work is summarized as follows:（1）Based on the rigorous evaluation of phase diagram data and thermodynamic data reported in literature,the CALPHAD method was used to re-optimize the thermodynamic parameters of the important Al₂O₃-MgO sub-system,and a set of self-consistent thermodynamic parameters was obtained.On this basis,the thermodynamic optimization of Al₂O₃-MgO-SiO₂ system was carried out using experimental data.The calculated results are in good agreement with the experimental data,which shows that the thermodynamic parameters of Al₂O₃-MgO-SiO₂ system obtained in this work are reasonable.（2）The key samples of Al₂O₃-MgO-CaO ternary system were prepared experimentally,and the isothermal section of the system at1350°C was investigated.Based on the thermodynamic parameters of the Al₂O₃-MgO binary system optimized in this work,combined with the phase diagram data in literature and the experimental data obtained in this work,the thermodynamic optimization of the Al₂O₃-MgO-CaO ternary system was carried out.The obtained thermodynamic parameters can reasonably describe the system.On the basis of the above work,combined with the thermodynamic parameters of Al₂O₃-SiO₂-CaO and CaO-MgO-SiO₂ ternary systems reported in literature,the thermodynamic parameters of Al₂O₃-MgO-SiO₂-CaO quaternary system was established.This work is an important basis for the construction of multi-component oxide system thermodynamic database,which can better guide the design of material composition and the improvement of preparation process.And this work is beneficial to enhance the added value of solid waste resources in the process of comprehensive utilization,achieve higher economic benefits,and better implement the idea of sustainable development.