Papers by Author: Ying Chun Zhang

Abstract: Bi₂Ti₂O₇ nanopowders were prepared using bismuth nitrate and tetrabutyl titanate as starting materials by sol-gel method. The decomposition of precursors, crystal structure and microstructure of the sample was characterized by TG/DTA, XRD and TEM techniques, and the results indicate that the sample is well-crystallized pyrochlore Bi₂Ti₂O₇ phase with spherical shape and an average grain size of 30 nm. Photocatalytic activity of Bi₂Ti₂O₇ powders was evaluated by photodegrading methyl orange solution. The result shows that Bi₂Ti₂O₇ has a higher photocatalytic activity than TiO₂ (mixed with rutile and anatase) with the same concentration, and when concentration of Bi₂Ti₂O₇ increased to 9g/L, half-life period T_1/2 is 0.97h, then methyl orange solution can be completely degraded in more than an hour.

Abstract: In this article we present the testing, evaluation of infrared radiation properties of polycrystalline materials especially as cordierite-based glass-ceramics. Researches aim to make a comprehensive and systematic exposition of emissivity definition, test principles and test methods. And on the basis of measurement results of the infrared emissivity of cordierite-based glass-ceramics, the Infrared radiation property of this polycrystalline material was discussed. Research has a positive significance on the development of the infrared radiation heating and drying materials.

Abstract: As an important solid tritium breeding ceramic material, Li2TiO3 pebbles with the diameter of 1mm are used in the breeding pebble bed for ITER test blanket module (TBM). Therefore, it is very important to evaluate the densities of Li2TiO3 ceramic pebbles accurately. In this paper, Li2TiO3 ceramic pebbles with the diameter of about 1mm were prepared by wet method using Li2CO3 and TiO2 as the main raw materials. The shape and microstructure are characterized by SEM technique. Densities of the ceramic pebbles were analyzed by both Archimedes principle and Mercury porosimetry methods. The results show that the density measured by Archimedes principle is higher than reality density, while the density measured by mercury porosimetry is accurate.

Abstract: ZnNb2O6 ceramics with a columbite crystal structure, is a promising candidate for application in microwave devices. In this study, ZnNb2O6 nano-powders were prepared using Nb2O5 and Zn(NO3)2 as raw materials by Pechini method. The microstructure and crystal structure of ZnNb2O6 powders were investigated systematically using X-ray powder diffraction and SEM techniques. The effect of amount of citric and ethylene on the formation of sol-gel and the particle size of ZnNb2O6 powders were also investigated using orthogonal design. Finally, the optimum process parameters for synthesis ZnNb2O6 nano-powders were obtained in this study.

Abstract: The carbon nanotube reinforced Ni-P matrix composite coating on 45# steel has been prepared by electroless plating method in this study. The microstructure and the corrosion properties of the composite coating were investigated systematically using SEM and a potentiostat. SEM results show that the carbon nanotube was uniform embedded in the crystal grains of Ni-P. The polarization curves indicate that the composite coating exhibit excellent corrosion resistance properties which is superior to that of the conventional Ni-P coating.

Abstract: The adsorption behavior of clay minerals in cadmium contaminated soils has been studied in order to remedy soils contaminated with this metal in this work. The results show that Langmuir model best describes the adsorption of Cd2+, and the maximum sorption values of 8.45 mg/g for bentonite, 5.69mg/g for sepiolite and 10.57mg/g for attapulgite are obtained at pH 5-6. In addition, the effect of clay minerals amendment on a highly cadmium contaminated soil has been studied by means of pot experiments. The results indicate that the metal concentrations in shoot and root of plant decreased with addition of clay minerals to soil (1%), and the highest decrease value of metal concentrations is obtained in the soils added by attapulgite amendment.

Abstract: The crystal structure, phase relation, microstructure and dielectric properties of microwave dielectric ceramics comprised of Zn(Nb1-xTax)2O6 were investigated systematically using XRD, SEM and a network analyzer in this study. XRD results show that the Zn(Nb1-xTax)2O6 ceramics have the orthorhombic for all x values. However, two kinds of solid solutions phase regions based on columbite structure and ZnTa2O6 structure were observed. SEM results show that the growth of grains is restrained with increase of Ta content in Zn(Nb1-xTax)2O6 ceramics. The dielectric properties exhibited a significant dependence on the crystal structure and compositions of the ceramics. The dielectric constant (εr) of Zn(Nb1-xTax)2O6 ceramics increased with increasing Ta content. However, the quality factors (Q×f) of this system show a different trend, and decrease with increasing Ta content. At x=0.65, a zero temperature coefficient of resonant frequency ( τ f) can be realized in Zn(Nb1-xTax)2O6 ceramics system.

Abstract: The effects of additions on the microstructure and microwave dielectric properties of 0.42ZnNb2O6-0.58TiO2 (ZNT) ceramics were investigated systematically. The sintering temperature of ZNT ceramics doped with different amounts of CuO, Bi2O3 and V2O5 can be effectively reduced. The phase of doped samples was studied compared to the undoped ZNT ceramics. For densified ZNT ceramics with the increasing amount of dopant CuO-Bi2O3-V2O5, the dielectric constants (εr) of densified samples ranges from 38 to 42, the Q×f values decrease evidently and ranges from 13300 GHz to 5000 GHz and the τf values are shifted toward negative.

Abstract: The microstructure and microwave dielectric properties of dielectric ceramics comprised of ZnNb2(1-x)TixO(6-3x) (x = 0 ~ 1) were investigated systematically using X-ray powder diffraction, SEM and a network analyzer in this study. The results showed that four phases were observed in this system. The dielectric properties at microwave frequencies exhibit a significant dependence on the composition and crystal structure of the ceramics. The dielectric constant ( er) of ZnNb2(1-x)TixO(6-3x)ceramics increases with increasing Ti content and the quality factors (Q ×f) significantly decreased. However, the temperature coefficient of resonant frequency ( t f ) changes from –59.08 ppm/oC at x = 0 to + 25.1 ppm/oC at x = 1, and a zero temperature coefficient of resonant frequency ( t f ) for this ceramics system was obtained at x = 0.84.

Abstract: The Ba5(Nb1-xTax)4O15 (x=0~0.5) solid-solution ceramics with hexagonal perovskite structure were prepared by solid-state oxide route. The phases and structure of the sintered ceramics were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influences of composition and sintering temperature on the bulk density, microstructure and microwave dielectric properties were also investigated. As the value of x increased from 0 to 0.5, the Q×f value increases from 36,049 to 49,493 GHz (at ~9GHz), whereas the dielectric constant (εr) decreases from 39.21 to 33.03 and the temperature coefficient of resonant frequency (τf ) decreases from 78.6 to 19.4 ppm/oC. The results indicate that the microwave dielectric properties of Ba5(Nb1-xTax)4O15 ceramics can be easily modified in a large range by changing the relative content of Ta to Nb.