Effect of CuO on crystallisation and properties of red R2O-CaO-MgO-Al2O3-SiO2 glass-ceramics from granite wastes

Granite waste occupies valuable land, pollutes the environment, and may cause health hazards; however, it contains the building blocks of glass-ceramics. Further, copper red glass-ceramics are valuable as high-grade decorative architectural materials. Therefore, we developed a method for creating copper red glass ceramics from granite waste. This study focused on the effect of 3, 5, 7, 9 and 15 wt% CuO on the crystallisation and properties of the R2O-CaO-MgO-Al2O3-SiO2 glass-ceramics prepared from granite wastes. Differential scanning calorimetry results determined that the 5 wt% CuO dopant level produced the most stable glass-ceramic. X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectrometry showed the presence of rod-like richterite(Na, F)syn (Na(Na, Ca)Mg5Si8O22F2) and granular cuprite (Cu2O) phases. X-ray photoelectron spectroscopy indicated that the Cu+ atomic percentages (A(Cu+)) in the 5 wt% CuO glass-ceramic was 86.4%, higher than any other sample. The colour of the 5 wt% CuO sample was copper red, and further increasing the CuO content did not significantly change the colour. The mechanical properties of the 5 wt% CuO glass-ceramic were suitable for structural applications, with a bending strength 167.80 MPa and a Vickers hardness of 7.62 GPa. Therefore, we showed that 5 wt% CuO doped granite waste can be processed into copper red glass-ceramics that are suitable for high-grade architectural decorative materials.