Tailoring Structural, Chemical, and Photocatalytic Properties of ZnO@β-SiC Composites: The Effect of Annealing Temperature and Environment.

For achieving unified functionalities of rare-earth free materials, the development of innovative zinc oxide and β-silicon carbide (ZnO@β-SiC) composites by a solid-state reaction method is presented. The evolution of zinc silicate (ZnSiO) is evidenced by X-ray diffraction when annealed in air beyond 700 °C. Detailed X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses reveal the involvement of silicon dioxide in forming ZnSiO. Transmission electron microscopy and the associated energy-dispersive X-ray spectroscopy elucidate the evolution of the zinc silicate phase at the ZnO/β-SiC interface, though it can be averted by vacuum annealing. These results manifest the importance of air in oxidizing SiC before a chemical reaction with ZnO from 700 °C. Finally, ZnO@β-SiC composites are found to be promising for methylene blue dye degradation under ultraviolet radiation, but the annealing above 700 °C is detrimental due to the evolution of a potential barrier in the presence of ZnSiO at the ZnO/β-SiC interface.