Papers by Author: Yue Hui Wang

Abstract: Surfactant-zirconium phosphate composites were prepared by surfactant cetyltrimethylammonium bromide intercalating to α-zirconium phosphate. The interlayer spacing of the lamellar structure was greatly expanded to 39.6 Å, as compared to 7.6 Å of α-zirconium phosphate. The molar ratio of surfactant to α-zirconium phosphate in the composites was found to be 1/1.46. The expanded interlayer separation is beneficial for complicated guest molecules intercalating to the galleries of the composites.

Abstract: This paper studied the dielectric performances and microstructure of the Ba-Ti-B-Si-O glass-ceramics fabricated with different methods. The experimental results showed that the pre-calcined method was an effective way to decrease the sintering temperature in glass-ceramic fabricating process, and the dielectric properties of the LTCC materials were εr ≈10, tanδ ≤ 2×10-3 (@1MHz). This study provided a composite method to fabricate LTCC for different applications that was composed of pre-calcined powders and molten powders with different ratios; Moreover, the dielectric constant and sintering performance of composite LTCC were adjustable by changing the ratio of pre-calcined powders and molten powders.

Abstract: Nanocrystalline Ag doped silica inverse opals were prepared by a sol-gel chemistry method via templating of polystyrene colloidal crystals. The ordered structures of colloidal crystal templates and inverse opals are characterized by scanning electron microscopy. Ag nanocrystals size is estimated as 20~30nm by Scherrer Formula from X-ray diffraction. The color and the stop band of the inverse opals are characterized by transmission spectrum. And five emission peaks of the nanocrystalline silver clusters are observed from fluorescence spectrum.

Abstract: A series of ferrroelectric-ferromagnetic composites were synthesized from BaTiO3 and NiFe2O4 ferrite by conventional solid-state route. XRD studies indicated that the composites comprised of only two phases, BaTiO3 phase with perovskite structure and NiFe2O4 phase with spinel structure. Frequency dependence of permittivity and permeability were also measured. Experimental results showed that the dielectric constant and initial permeability of these composites could be tunable by varying the composition of composites. Thus, these composites can be used for multilayer chips EMI filters.

Abstract: A series of powders of (Ba1-xLa2x/3)(Ti1-xNb4x/5)O3 (0.05≤x≤0.3) have been synthesized by solid-state reaction route, and the effects of the dopants on the microstructure of BaTiO3 were investigated by XRD, SEM, HTEM and EDS in the BaTiO3-La2O3-Nb2O5 ternary system. It was found that the secondary titanium-rich phase occurred for x ≤ 0.1, while Ba3La3Ti5Nb5O30 yields as secondary phase for x ≥ 0.2. In the whole range of 0.05 ≤ x ≤ 0.3, the crystal structure of BaTiO3 solid solutions is cubic system. There are two substitution modes in the system: the substitution mode of La ions dissolved into Ba sites is significant for x ≤ 0.2, but the substitution mode of Nb ions dissolved into Ti sites is significant for x>0.2. TEM observation and EDS analysis revealed that the concentration gradient of Nb existed and La almost distributed homogeneously in a grain. Thus, the dielectric materials composed of La-Nb-codoped BT are not fitted to form the core-shell structure for the higher dopants.

Abstract: Infrared-to-visible upconversion phosphors Y2O3: Yb, Er and Gd2O3:Yb, Er with narrow size distribution were synthesized by using a stable microemulsion system, which included triton X-100, n-hexanol, cyclohexane and water. Appearance-controllable nanocrystals were achieved by adjusting the ratios of assistant surfactant and surfactant. The X-ray diffraction patterns of the samples showed that the powders were cubic phases of Y2O3 and Gd2O3, respectively. After calcination with different temperature settings in air atmosphere, the particles were spherical through the observation by scanning electronic microscopy. Red and green upconversion luminescence was obtained under 980 nm infrared excitation. Several contributions to the intensity of upconversion emission were also investigated. These upconversion phosphors may be used as fluorescent labels for the sensitive detection of biomolecule, immunoassay or DNA assays.