Glass ceramics with different colours from granite wastes prepared by changing crystallisation temperature: Crystallisation and properties

Abstract

Granite is a popular natural decorative material, and its production generates large amounts of waste. Therefore, researchers have paid close attention to the utilization of granite waste as a resource. In this work, glass-ceramic containing the same concentration of copper oxide were prepared from granite waste using a melting technique. The effects of different crystallisation temperatures on the valence of copper ions and the crystallisation of the glass-ceramics were carefully examined. The glass-ceramics crystallised at 724 °C, 783 °C, and 904 °C contained copper oxide (CuO), diopside (CaMgSi2O6), and clinoenstatite (MgSiO3). Meanwhile, those crystallised at 987 °C and 1080 °C contained richterite ((Na, F)syn (Na(Na, Ca)Mg5Si8O22F2)) and cuprite (Cu2O). The crystallisation temperature influenced the valence state of copper ions in the glass-ceramics, as demonstrated by X-ray photoelectron spectroscopy (XPS). Not only was the Cu+ content heterogeneous among samples crystallised at the different temperatures heterogeneous, but the samples also exhibited dissimilar colours. The atomic percentage of Cu+ ions (ACu+) in the sample crystallised at 987 °C was higher than that in the other samples. The mechanical properties of the sample crystallised at 1080 °C included a bending strength of 127.14 MPa and a Vickers hardness of 8.16 GPa.