Wenzhi Huang

Preparation of TiO2 hollow nanofibers by electrospining combined with sol–gel process

TiO2 hollow nanofibers have been fabricated by directly annealing electrospun polyvinylpyrrolidone (PVP)/Tetra-butyl titanate (TBT) composite nanofibers. In this approach, PVP/TBT composite fibers were first synthesized by electrospinning PVP/TBT solution, and then calcined at high temperature with an appropriate heating rate to form hollow TiO2 nanofibers. During the heat treatment, the solvent composition, the amount of TBT and the heating rate have important influences on the morphologies of the TiO2 nanofibers. Morphologies of TiO2 could be tuned from solid nanofibers to belts, hollow nanofibers and rods by controlling the appropriate preparation conditions. The crystal structure, morphology, surface composition and specific surface area of the TiO2 hollow nanofibers were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Brunauer–Emmett–Teller analysis, respectively.

Preparation and characterization of MgO nanorods

Abstract Synthesis of magnesium oxide (MgO) nanorods was achieved by simply heating MgCl 2 powder at 750°C for 1.5 h in a constant flow of mixture gas (90% pure argon and 10% pure hydrogen). Transmission electron microscopy (TEM) morphology and energy-dispersive X-ray spectrometry (EDX) analysis showed that the product is mainly composed of MgO nanorods with diameters of 15 to 50 nm, and lengths ranging from 1 to 3 micrometers. After the MgO nanorods were incorporated into (Bi, Pb)-2223 superconductor, the critical current densities (Jc’s) of the nanorod-superconductor composites are significantly enhanced.

Morphology-controlled synthesis of gadolinium fluoride nanocrystalsvia ultrasonic and salt assisted method

Gadolinium fluoride NaxGdyFx+3y crystals with different morphologies and compositions have been successfully synthesized via a facile ultrasonic and salt assisted method at room temperature without any template or organic additive. Crystal structure and morphology of the fluorides were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Reaction conditions, such as ultrasonic irradiation, F/Gd molar ratio (R(F/Gd)), concentration of sodium nitrate and ultrasonic time have a close relationship with the morphology and phase composition of the final products. The growth mechanism of the uniform and monodisperse GdF3 nanospindles was proposed based on the time-dependent experiments. The photoluminescent (PL) properties of the as-obtained products revealed that Eu3+ doped NaGdF4 nanocrystals with different morphologies present characteristic luminescence of Eu3+, and their emission intensities strongly depend on morphology.

Thermal Shock Resistance of APS 8YSZ Thermal Barrier Coatings on Titanium Alloy

Thermal barrier coatings (TBCs) with a typical 8YSZ ceramic top coat and CoNiCrAlY bond coat were deposited on titanium alloy substrate (Ti-6Al-4V in wt.%) by air plasma spraying. Thermal insulation and thermal shock resistance of the TBCs at different temperatures as well as their failure behavior were investigated. The results showed that the test temperature had a significant effect on thermal shock life of the TBCs. Failure of the TBCs systems was caused by the formation of crack, bond coat oxidation and elemental diffusion. The vertical cracks induced by thermal shock cycles were probably responsible for the enhancement in thermal shock resistance of the TBCs. Furthermore, elemental diffusion had a great effect on the acceleration of the TBCs failure. The TBCs could provide a good thermal protection for the titanium alloy substrate.