Effect of Ball Milling Time on the Physical, Thermal and Fracture Behaviour of 2MgO.2Al2O3.5SiO2 Precursors

Abstract

In this study, an evaluation has been made into the influence of milling time on the thermo-physical and fracture properties of a MgO-Al2O3-SiO2 system. The powdery and compacted formulation of the raw materials was studied using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), particle size distribution (PSD), Fourier Transform Infrared (FTIR), and acoustic emission technique (AE). The milling mechanism comprised of essentially three stages of milling time viz.; 120, 240, and 360 min respectively, with no milling (0 min) serving as the control batch. During the first stage of milling (120 min), it was observed that the greatest deformation occurred for the powdery formulation with increasing surface area, control batch inclusive, from 26.4 to 41.1 m2 g−1. It was also noticed that the density of the samples increased with progressive ball milling time. The mean crystallite sizes of un-milled and milled powders were calculated as 36.61, 48.82, 34.27 and 52.13 μm for control batch and powders milled at 120, 240, and 360 min, and denoted as MT0, MT120, MT240, and MT360, respectively. The mean crystallite sizes further reduced with increasing milling time up to 240 min and increased with milling time up to 360 min. These results were in line with the SEM findings. The acoustic emission (AE) intensity increased reaching a maximum at MT240, and a noticeable decline in the case of MT360 was observed. This indicated a gradual crack growth behavior because of the highly stressed powders used for the compacts.