Ahmad Saeedi

Steel slag waste produced by the steel industry accumulates in open areas or is disposed of in landfills, causing harm to the environment and human health. Valorizing steel slag through comprehensive data analysis is imperative and could add value to the product with respect to energy conversion and storage applications. This study investigated the morphological, structural, and optical characteristics of a thermally annealed steel slag composite generated from iron and steel factories. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, and UV–visible spectrophotometry were subsequently used to evaluate the impact of thermal treatment on the morphology, structure, elemental composition, and optical properties. It was found that the pre-treated slag composites contained a variety of irregular grain sizes and microscale fragments, primarily composed of C (18.55%), O (50.85%), and Fe (29.41%), with lower amounts of Mg (0.31%), Si (0.44%), and Ca (0.44%), indicating the natural formation of a disordered iron composite. Thermal treatment at different temperatures (300 °C, 600 °C, and 900 °C) increased the grain density and clustering, resulting in denser two-dimensional microstructures at 900 °C. Additionally, XRD and Raman analyses of both untreated and thermally treated slag composites revealed the presence of a disordered iron oxide composite, including (Fe3O4), hematite (α-Fe2O3), and maghemite (γ-Fe2O3) phases. A significant increase in optical absorbance was also observed after annealing at 600 °C, highlighting the successful optimization of the elemental composition of the slag composite. A band gap energy of approximately 2.2 eV was obtained from this optimization at 600 °C. The optical conductivity of the composite reached 2.1 × 106 S−1 at 600 °C, which indicates an enhancement in charge transfer among the optimized chemical elements in the waste composite. These findings suggest an optimization method for novel composites derived from steel slag waste, indicating its potential as a low-cost material for energy storage systems (batteries, supercapacitors, and fuel cells) and optoelectronic devices.

Herein, sol–gel are used to synthesize pure and calcium‐doped ZnO (CZO). X‐ray diffraction shows that all samples have hexagonal wurtzite structure with a slight distortion of ZnO lattice and no extra secondary phases. The crystallite size increases after the addition of calcium from 31 to 34 nm. Photoluminescence shows the vanishment of the green emission band existed in the pure sample; in addition to the appearance of new peaks at 408, 448, 465, and 596 nm attributed to zinc interstitials (Zn i ), zinc vacancy (V Zn ), oxygen vacancy defect (V o ), and oxygen interstitial (O i ), respectively. The increase of crystallites size influences the efficacity of CZO sample against microbes. The different mechanisms to enhance the antibacterial activities are the release of Zn 2+ , reactive oxygen species production, and electrostatic interactions. Increasing the amount of CZO powder in dimethyl sulfoxide from 50 to 100 μg mL −1 leads to an increase of antibacterial activity of samples; and this is probably due to enhancement of number of interaction sites. Promising results are illustrated, which proves the potentiality of doping with Ca. The growth curves through optical density (OD 600 nm ) measurements of strains in CZO nanoparticles using serial fold dilution method indicated that strains viability decreases with increasing nanoparticles concentrations.