A 100% high-aluminum fly ash-based high-density mullite ceramic with a triple microstructure: Preparation and mechanical characterization

The value-added utilization of high-aluminum fly ash (HAFA) is of significance to China's solid waste development strategy because of the country's large amount of emissions. Mullite is the main component of HAFA, which is an important raw material that is used for the preparation of high-performance ceramics. Therefore, a new technology for the preparation of ceramics from HAFA is proposed in this study. Based on the combination of the concept of particle grading used in engineering geology with ceramics preparation, rearrangement of the ceramic microstructure, and the use of production experience and the Furnas model to calculate the best particle reorganization solution, a 100% HAFA-based high-density mullite ceramic with a triple microstructure was successfully designed. By analyzing the ceramic body using X-ray diffraction, scanning electron microscopy, and a mineral liberation analyzer, the roles of the three different structures and strengthening principles of the ceramics were determined. Given the synergy of the triple microstructure, the ceramic exhibits excellent physical properties (bulk density of 2.29 g/cm³; rupture modulus of 116.74 MPa; apparent porosity of 0.00%; and water absorption of 0.00%). Therefore, the mullite-based ceramic can be used as a high-strength waterproof material in high-temperature and/or high-corrosion environments. The proposed microstructure opens up a new route for the utilization of HAFA, greatly improves the value of its utilization, and provides new research ideas for future studies.