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

Abstract

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 (Zn2SiO4) 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 Zn2SiO4. 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 Zn2SiO4 at the ZnO/β-SiC interface.

Tuning Visible-to-Near Infrared Dual-Band Emission in ZnO@β-SiC Composite Phosphor

“…On the other side, the 560 nm peak is found to be slightly blue-shifted after annealing at 1200 °C and remained unchanged up to 1400 °C. Furthermore, the amount of ZnO was previously shown to be reduced significantly in ZS-12A by subsequent formation of Zn 2 SiO 4 at the ZnO/β-SiC interface due to strong chemical reaction of ZnO with SiO 2 . A similar green emission was also reported for a ZnO/porous Si system due to the formation of V O at the interface. , …”

“…Such an intriguing dual emission at ∼560 and 740 nm has never been reported before to the best of our knowledge. One can also find the suppression of the near band edge emission of ZnO (∼380 nm) with the evolution of a relatively weak peak at ∼420 nm, which can be attributed to the formation of defects like SiO related species , due to the formation of SiO 2 by surface oxidation of β-SiC after a heat treatment at 1100 °C. In addition to defects such as SiO-related species, nonbridging oxygen-hole centers (NBOHC) (O 3 Si–O°) have also been suggested to arise during the surface oxidation of β-SiC.…”

“…In fact, the specific reason behind the decrease in E a , A and I o for S-12A depends on the material and its unique characteristics, including changes in the structure by introducing defects, doping, and/or composition variation. In this respect, the formation of SiO 2 and its related defects in S-12A sample around β-SiC are most probably responsible for reducing E a .…”

“…A typical XRD pattern of the 1200 °C annealed ZnO@β-SiC composite is compared with the corresponding reference samples ZnO (JCPDF file #00-036-1451) and SiC (JCPDF file #00-029-1129) in Figure , confirming the presence of Zn 2 SiO 4 . Detailed structural analysis has been given in ref , showing that the high temperature annealing of the ZnO@β-SiC composite up to 1200 °C leads to the formation of an additional Zn 2 SiO 4 (JCPDF file #01-083-2270) phase at the cost of ZnO and β-SiC. Most importantly, this new phase has been demonstrated to be originated from the solid-state reaction at the ZnO/β-SiC interfaces …”

“…Detailed structural analysis has been given in ref , showing that the high temperature annealing of the ZnO@β-SiC composite up to 1200 °C leads to the formation of an additional Zn 2 SiO 4 (JCPDF file #01-083-2270) phase at the cost of ZnO and β-SiC. Most importantly, this new phase has been demonstrated to be originated from the solid-state reaction at the ZnO/β-SiC interfaces …”