Benxue Liu

Seedless growth of ZnO nanorods on TiO2 fibers by chemical bath deposition

A chemical bath deposition method without using ZnO seed layers was developed to grow dense ZnO nanorods (NRs) on TiO2 fibers in saturated nutrition solution. The crystal phase, microstructure and photoluminescence of the as received heterostructure were examined by X-ray diffraction (XRD), scanning-electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and photoluminescence spectroscopy (PL). The structure consists of a TiO2 fiber core and a radial ZnO NR shell, with growth directions almost perpendicular to the central fibers. Luminescence quenching of TiO2 was observed in the PL spectra of the heterostructure due to the shielding effect of the covered ZnO NRs. According to the results of SEM, XRD, infrared spectroscopy (IR) and EDX, the seedless growth mechanism was discussed. It was found that at room temperature, Zn-based layered double hydroxides (Zn-LDHs) with positive charges, which are the building blocks for the nucleation and growth of ZnO NRs, were firstly formed in ZnO growth solution. The Zn-LDHs were deposited on the negatively charged TiO2 fibers through electrostatic attraction followed by being dehydrated into ZnO NRs at an elevated temperature. The cooperative interaction between the TiO2 fibers and ZnO NRs was investigated. The two components in the structure have a robust interaction that even violent ultrasonic power could not peel the ZnO NRs off from the TiO2 fibers.

Improvement of mechanical strength of ultralight resorcinol–formaldehyde/silica aerogel by addition of zirconia

In the present work, RF/SiO2 aerogels reinforced by zirconia (ZrO2) were fabricated by a sol–gel process combined with N2-ethanol supercritical drying. The physical properties and microstructures of the aerogels were investigated by uniaxial compression, X-ray diffraction, N2 physico-adsorption, scanning electron microscopy, X-ray photoelectron spectroscopy, and infrared spectrum. The compressive strengths of the aerogels were improved obviously with the addition of ZrO2. The composite aerogels remained amorphous state even the percentage of ZrO2 reached up to 6.77 wt%. The pore sizes of the aerogels with various ZrO2 were hierarchical and the Brunauer-Emmett-Teller surface area increased distinctly with the increase of ZrO2. On the contrary, the aerogel particle sizes decreased as the increase of ZrO2. In our opinion, the enhanced compressive strengths derive from both of the varied pore structures and the decrease of the particle sizes.Graphical Abstract

ZnO long fibers: large scale fabrication, precursor and the transformation process, microstructure and catalytic performance

The development of effective and low-cost catalysts for the synthesis of chemical energy and for the photo-assisted elimination of pollution is of great importance for the sustainable development of human society. This work designs a fibrous ZnO catalyst, which was composed of stacked ZnO nanoparticles. Photocatalysis investigations demonstrated that the fibers possess higher catalytic ability compared to their powder counterparts. Moreover, the fibrous form is more suitable for application in a continuous mode and simple separation operation. The ZnO fibers were fabricated by the centrifugal-spinning of a molecular precursor sol into gel fibers, followed by heat treatment. The viscous precursor sol was synthesized by concentrating a zinc citrate aqueous solution, which was made from citric acid and ZnO powders. The mechanism of formation of the organozinc sol was investigated by a series of characterizations of the precursor solution, gel precursor, and the decomposition of the gel precursor. The results indicate that zinc citrate monomers in precursor solution were assembled into a multinuclear structure induced by solvent evaporation.