Fung-luen Kwong

A Versatile Method for Controlled Synthesis of Porous Hollow Spheres

A versatile method was developed to synthesize nickel silicate, silica, and silica-nickel composite porous hollow spheres by using silica spheres as templates. In the preparation, silica spheres were treated with a mixture of NiSO(4)·6H(2)O and NH(3)·H(2)O. The nickel-based ingredient reacted with the silica to form a shell while the alkaline solution could remove the silica core, thus forming the nickel silicate hollow spheres. After these spheres were further treated with hydrogen in reduction or with HCl in etching, they became silica-nickel hollow spheres or silica hollow spheres, respectively. The sizes of these hollow spheres depended on the concentration of the precursor. Our investigation also found that their surface properties or magnetic properties could be tailored by adjusting the fabrication parameters.

Template-free hydrothermal synthesis of hexagonal ZnO micro-cups and micro-rings assembled by nanoparticles

The hexagonal ZnO micro-cups and micro-rings assembled by nanoparticles have been successfully synthesized via a template-free hydrothermal synthetic method, using only one reactant Zn(CH3COO)2·2H2O, which not only serves as the zinc source, but also provides an effective etchant CH3COOH that plays a strategic role in the formation of these ZnO hollow structures.

Preparation and Characterization of Activated Carbon Fiber from Paper

Activated carbon fibers (ACFS) with surface area of 1388 m2/g prepared from paper by chemical activation with KOH has been utilized as the adsorbent for the removal of methylene blue from aqueous solution. The experimental data were analyzed by Langmuir and Freundlich models of adsorption. The effects of pH value on the adsorption capacity of ACFS were also investigated. The rates of adsorption were found to conform to the kinetic model of Pseudo-second-order equation with high values of the correlation coefficients (R>0.998). The Langmuir isotherm was found to fit the experimental data better than the Feundlich isotherm over the whole concentration range. Maximum adsorption capacity of 520 mg/g at equilibrium was achieved. It was found that pH played a major role in the adsorption process, higher pH value favored the adsorption of MB.

Superconductivity in fluorine and yttrium co-doped SmFeAsO

Polycrystalline fluorine and yttrium co-doped SmFeAsO samples are synthesized by solid state sintering and their physical properties are studied. The lattice parameters of the Sm1−yYyFeAsO0.8F0.2 samples decrease with the increasing y due to the smaller Y ions and the stiffness of the Y-O bond. The maximum critical temperature Tc of the samples is at y = 0.05. This may be due to the fact that the strong interaction between Sm and Fe of the Fe-As bond is being re-disturbed by the doped Y ions.

Reaction mechanisms between Al and Fe3O4 powders in the formation of an Al-based metal matrix composite

The reaction mechanisms between Al and Fe3O4 powders were investigated. Differential thermal analysis revealed that a two-step displacement reaction between Al and Fe3O4 took place during sintering. Initially, the Fe3O4 was converted to amorphous FeO at ∼720°C and some of the Al was oxidized to amorphous Al2O3. In the final stage, when the temperature reached ∼840°C, crystalline Al2O3 particles were produced in the molten Al–Fe liquid. The effects of cooling rate on the microstructures were studied. When the Al–Fe liquid was furnace-cooled to room temperature, proeutectic Al3Fe plates, plate-like divorced eutectic Al3Fe and Al2O3 particles were in situ formed in the Al(Fe) matrix. While quenching from 700°C, nanometer-sized Al dendrites and Al–Al6Fe eutectic lamellae were produced in the Al matrix. However, when it was rapidly quenched from 900°C, the size of the proeutectic Al3Fe phases was further reduced and Al6Fe nanorods were found in the Al–Al6Fe eutectics. A model was proposed to describe the transformation of the Al–Fe intermetallics during solidification.

Fabrication of Hollow Anatase Structure by Using Sea Wool Sponges

Highly porous carbon-doped anatase was produced by a simple and time-saving method. The product was prepared by using sea wool sponges and a titanium-contained organic solution. The intermediate product was pyrolyzed sponges coated with amorphous anatase. When further annealed, the final product was an entirely carbon – anatase product with the original structure of sea wool sponges. The struts in the carbon – anatase product were hollow with wall thickness less than 300 nm. Cathodoluminescence measurement showed that this C-TiO 2 product was sensitive to visible light.