Effect of Copper Oxide Addition on Physical and Optical Properties of Glass Prepared from Sugarcane Leaf Ash from Biomass Power Plants

Abstract

This research aims to investigate the influence of copper oxide (CuO) addition on the physical and optical properties of glass prepared from sugarcane leaf ash, a byproduct from biomass power plants. Chemical composition analysis using Energy Dispersive X-Ray Fluorescence (EDXRF) indicates that the sugarcane leaf ash primarily consists of SiO2 (66.77% by weight) and CaO (17.26% by weight). Consequently, this ash can serve as a primary raw material to replace pure chemicals in the glass system. The glass synthesis was conducted using the melt-quenching technique at a melting temperature of 1,200°C, followed by an annealing process at 500°C.The experimental results reveal that as the CuO concentration increases, the density of the glass samples tends to decrease from 2.8756 to 2.8479 g/cm3. Conversely, the molar volume increases from 22.2437 to 22.4941 cm3/mol. This phenomenon is attributed to the role of CuO as a network modifier, which disrupts the original glass network and increases the formation of non-bridging oxygen (NBO) atoms, leading to structural expansion and increased free volume within the glass matrix. Regarding optical properties, the refractive index exhibits a downward trend from 1.5703 to 1.5646, which is consistent with the Lorentz-Lorenz theory. Optical absorption analysis shows a prominent peak at approximately 760 nm, corresponding to the transition of Cu2+ ions within a distorted octahedral coordination. This transition causes the glass to change from its natural yellowish-brown tint—resulting from inherent impurities—to a more intense green hue as the dopant concentration increases. This color shift is further confirmed by CIE L*a*b* colorimetric analysis, where the a* value becomes increasingly negative.