Diopside-like based ceramics prepared via one-step sintering of extracted titanium slag and coal fly ash

Abstract

Diopside-Like based ceramics as the main crystalline phase (expressed as ‘Diopside’) were prepared via one-step sintering using extracted titanium slag (ETS) and coal fly ash (CFA) as raw materials. The effects of CFA content and sintering temperature on the crystal phase composition, microstructure, properties and crystallization kinetics were studied by X-ray fluorescence, X-ray diffraction, scanning electron microscopy, and inductively coupled plasma emission spectrometry. According to the findings, the addition of CFA supplemented the deficiency of Si and Al in ETS and balanced the Ca/Al/Si molar ratio in the system. Moreover, at the CFA doping of 20 %, melilite was gradually transformed into ‘diopside’ at 800–1100 °C that further remained stable at 1160–1200 °C. ‘Despite’ the fact that the crystallization activation energy increased and the Avrami index was at its lowest level (1.75), the crystallization temperature was reduced, whereas the crystallization rate increased, causing the ceramic body and surface to crystallize and thereby improving the properties of ceramics. Sintering at 1180 °C for 1 h resulted in ceramics with ‘diopside’ as the primary crystal phase composition. The water absorption, linear shrinkage, bulk density, bending strength, and acid resistance were respectively 1.3 %, 13 %, 2.89 g cm−3, 141.8 MPa, and 97.36 %. Finally, ‘diopside’ possessed the higher acid resistance than melilite and anorthite.