Wenxiu Liu

Synergistic effect of Fe-doping and stacking faults on the dielectric permittivity and microwave absorption properties of SiC whiskers

Previously, we have found that the stacking faults density in SiC whisker (SiCw) significantly affects its dielectric permittivity mainly through the enhanced dipolar loss mechanism. Doping has been considered as another effective way to increase the dielectric permittivity of granular SiC. In order to further investigate the possible synergistic effect of Fe-doping and stacking faults on permittivity, permeability, and microwave absorption properties, Fe-doped SiCw with various stacking faults densities were prepared. Experimental results indicate that the Fe-doped SiCw with internal stacking faults shows a higher dielectric permittivity than that of undoped SiCw with only stacking faults. Both dielectric permittivity and microwave absorption properties of Fe-doped SiCw increased significantly with the increase in dopant concentration. First-principle calculation reveals that Fe-doping tunes SiC to be half-metallic, and thus, its electric conductivity as well as conduction loss is enhanced. So, both the dielectric permittivity and microwave absorption properties of Fe-doped SiCw were significantly improved due to the synergistic effect of the enhanced conduction loss caused by Fe-doping and the dipolar loss induced by stacking faults. And, the measured weak magnetic loss contributes to that as well.

Role of ammonium ions on the stability of TiO2 sol

Abstract In this paper, the role of the trace ammonium ions on the stability of TiO2 sol prepared by peroxo titanic acid (PTA) sol was investigated. The results showed that the removal of ammonium ions in PTA sol is beneficial to reduce agglomeration and increase the negative charge on the surface of TiO2 colloidal particles, contributing to the higher stability and longer storage time of the TiO2 sol. It was also approved by the increase of interaction energy calculated by classical DLVO theory. In addition, the photocatalytic performance of TiO2 sol was improved due to the decrease of aggregation of TiO2 colloidal particles. Graphical Abstract

Synthesis of mesoporous core-shell TiO 2 microstructures with coexposed {001}/{101} facets: enhanced intrinsic photocatalytic performance

TiO2 microstructures were synthesized via a facile one-step route for enhanced intrinsic photocatalytic performance. The prepared TiO2 microstructures are featured by both mesoporous core-shell structures and coexposed {001}/{101} facets. Their intrinsic photocatalytic performance were remarkably enhanced due to their high specific surface area, coexposed {001}/{101} facets, and promoted separation of photogenerated carriers. Furthermore, the origin and detailed mechanism for diethylenetriamine (DETA) that served as a high efficient stabilizer of TiO2 {001} facet have been theoretically investigated. Finally, a new DETA-modified Ostwald ripening mechanism was originally proposed when studying the growth mechanism of the mesoporous core-shell TiO2 spherical microstructures with coexposed {001}/{101} facets.