Synthesis of Hematite Using Different Additives and The Fabrication of Hematite/SiO₂ Composite

Hematite (α-Fe₂O₃) is a widely studied iron oxide due to its broad functional versatility in catalysis, sensing, and environmental applications. However, controlling its morphology and crystallinity remains a challenge, which limits its performance in composite materials. This study investigates the role of sodium hydroxide and citric acid as additives to identify optimal hematite characteristics on the fabrication of hematite/SiO₂ composite via the sol-gel method. Sodium hydroxide serves as a source of hydroxide ions, accelerating nucleation and acting as a precipitating agent, while citric acid chelates Fe³⁺ ions and caps growing nuclei, which enhances crystallinity and suppresses particle agglomeration. As a result, hematiteCA exhibited brownish-purple appearance and higher crystallinity, whereas hematiteSH showed larger and more agglomerated particles. Integrating silica into hematiteCA produced wine-red hematite/SiO2 composites and porous-like surface morphology. These findings demonstrate that additive selection is a critical parameter in synthesizing hematite microstructure and enhancing its compatibility with silica, thereby enabling the development of composites for advanced applications.