Zhong-Yong Yuan

Preparation and structure analysis of titanium oxide nanotubes

Well crystallized nanoscale tubular materials have been synthesized via the reaction of TiO2 crystals of either anatase or rutile phase and NaOH aqueous solution. The atomic structure of the synthesized tubular material is imaged by high-resolution transmission electron microscopy (HRTEM), and the composition of individual tubular structures is determined using selected area energy dispersive X-ray spectroscopy (EDX). Our results show that the tubular materials are well crystallized tubes with an average diameter of about 9 nm and little dispersion, and are composed of mainly titanium and oxygen. The atomic ratio of O/Ti is found, however, to vary from tube to tube. Detailed electron and x-ray diffraction studies show that the structure of our titanium oxide nanotubes do not agree with those made of TiO2 crystals with either anatase or rutile phase. HRTEM observations revealed that the titanium oxide nanotubes usually have multiple shells, in analogy with multiwalled carbon nanotubes, but the shell spacin...

Simple approach to highly oriented ZnO nanowire arrays: large-scale growth, photoluminescence and photocatalytic properties

A simple and low-cost soft route has been developed to the direct large-scale production of highly oriented ZnO nanowire arrays at 60 °C. It has been found that the growth of well-aligned ZnO nanowire arrays is dependent on several parameters, such as the reaction time and the concentration of ammonium ions. The environmentally benign ZnO nanowires obtained, with significant photoluminescence property and interesting photocatalytic activity, are single crystals and have a low defect concentration, which could be expected to find promising potential for optoelectronic and environmental application.

Surfactant-assisted synthesis of unprecedented hierarchical meso-macrostructured zirconia

A surfactant-assisted one-step synthesis route was developed, leading to the formation of a very high surface area (600 m2 g−1) of zirconia and unprecedented hierarchical meso-macroporous structure with wormhole-like mesoporous walls and a novel, uniform assembly of macropores ranging in size from 300 to 500 nm.

Cyclohexanol dehydrogenation over Co/carbon nanotube catalysts and the effect of promoter K on performance

Carbon nanotubes (CNT) were used as support medium to prepare Co catalysts for the selective dehydrogenation of cyclohexanol. Due to the unique structure and electronic property of CNT, Co/CNT possessed less acid sites than Co/activated carbon (AC). It seems to be easier to form multi-point complexes on Co/CNT than on Co/AC, resulting in a little higher selectivity to cyclohexanone and different distribution of by-products. The effect of K addition, attributed to electronic promotion, was also stronger on Co–K/CNT than on Co–K/AC.

Transmission electron microscopy and electron energy-loss spectroscopy analysis of manganese oxide nanowires

Single-crystalline MnOOH and Mn3O4 nanowires have been prepared by hydrothermal treatment of commercial bulky manganese oxide particles. β-MnO2 and α-Mn2O3 nanowires were prepared by calcination of MnOOH nanowires. Transmission electron microscopy analysis demonstrates that MnOOH nanowires grow directly from MnO2 raw particles. The diameter of the nanowires is 20–70 nm, while the length can reach several micrometers. MnOOH nanowires grow preferentially along the [010] direction and Mn3O4 nanowires prefer to grow along the [001] direction; the long dimension of both β-MnO2 and α-Mn2O3 nanowires is along [001]. Electron energy-loss spectroscopy analysis shows that the position of the prepeak of the oxygen K edge shifts to higher energy and the energy separation between the two main peaks of the oxygen K edge decreases with decreasing manganese oxidation state. The manganese-white-line ratios (L3∕L2) were calculated.

A simple method for coating carbon nanotubes with Co–B amorphous alloy

A simple chemical method was employed to coat carbon nanotubes (CNTs) with a layer of Co-B amorphous alloy. This technique involved a redox reaction using KBH4 as reducing agent and Na-2[Co(OH)(4)] complex as cobalt precursor. The amorphous character of the Co-B alloy was confirmed by high-resolution transmission electron microscopy (HRTEM) and Xray diffractogram analysis (XRD). These coated carbon nanotubes may be of great interest in magnetic research and as highly active catalysts in heterogeneous catalysis

Co/carbon-nanotube monometallic system: the effects of oxidation by nitric acid

Multi-walled carbon nanotubes, produced from catalytic decomposition of C2H2, were pre-oxidized by boiling nitric acid before being used as support media in a Co/carbon-nanotube monometallic catalyst system. The microstructures of nanotubes and the cobalt particles were examined by using high-resolution transmission electron microscopy and X-ray diffractometry. Various structural modifications on the nanotubes, such as thinned tubes, tubes with holes, and stepped surface with open edges of graphitic sheets were observed. In comparison with cobalt particles on unoxidized nanotubes, the cobalt nanoparticles deposited on the oxidized nanotubes have much smaller size and higher dispersion, resulting in significantly better catalytic performance (18.4% higher in initial conversion) in dehydrogenation of cyclohexanol to cyclohexanone.

Controlled Synthesis of Carbon-Encapsulated Co Nanoparticles by CVD

Communication: Carbon-encapsulated cobalt nanoparticles are prepared over a range of temperatures and partial pressures by CVD from cyclohexane on prepared substrates consisting of ground powders Of SiO2 impregnated with Co(NO3)(2) and (NH4)(2)Mo2O7. The encapsulated cobalt nanoparticles are freed from the incorporated SiO2 and molybdenum by treating the deposition product with aqueous hydrofluoric acid. Extracted material is dispersed in ethanol and deposited on a carbon-coated and prior to investigation by high-resolution TEM.

Thermally stable macroporous zirconium phosphates with supermicroporous walls: a self-formation phenomenon of hierarchy

A self-formation phenomenon leading to the hierarchically thermally stable macroporous zirconium phosphates with amorphous supermicroporous walls from the precursors of zirconium propoxide and orthophosphoric acid solution was observed.

Hierarchical interlinked structure of titanium oxide nanofibers

A novel hierarchical interlinking structure of titanium oxide nanofibers with high surface area has been prepared by a soft hydrothermal chemical process via the reactions of amorphous TiO2 gel (or commercial TiOSO4 particles) and NaOH solution.