Papers by Author: Qi Bing Chang

Abstract: Membrane modification is an important technology to improve the membrane performance. Ceramic membranes modified with nanometal oxide coating are prepared by homogeneous precipitation or in-situ hydrolysis method. TEM images show that the nanocoating distributes in the surface of the membrane pores. The nanocoating has no the separation function but just changes the surface characters of ceramic membrane. The permeate flux of the modified membrane increase above 20% than the unmodified membrane while treating the stable o/w emulsion with the concentration of 4g/L.

Abstract: To meet the requirement of ceramic pigment for ink jet printing, CoAl₂O₄ pigment was prepared by nitrate-glycine method. The effect of nitrate/glycine ratio, calcination temperature and organic sacrificial agent on the particle size and chroma of the blue pigment were considered. The results show that the particle size of the pigment increases with the increase of glycine in the ratio and the decrease of the calcination temperature. However, the increase of the calcination temperature results in the broadening of the particle size distribution of the pigment. The addition of the organic sacrificial agent contributes to decrease the particle size of the pigment, which is about 2.0 μm. The chroma of the pigment is L*=47.62、a*=9.49、b*=-51.41. The blue pigment can be used in ink jet printing.

Abstract: The high sintering temperature of Al₂O₃ is the main reason of the high cost of the common ceramic membrane supports. To decrease the sintering temperature, kaolin and talc were chosen as sintering aid because the reaction between kaolin, talc and Al2O3 generates cordierite. The Al₂O₃-cordierite porous ceramic samples were sintered in the range of 1450~1510°C. The microstructure and the bending strength of the samples were characterized. The results show that the content of kaolin is no more than 8%, the bending strength of the porous ceramic sintered at 1460°C and 1510°C are 77MPa and 153MPa, respectively. The further increases of the kaolin content result in the decrease of the bending strength and the porosity. The needle-like cordierite locates in the neck of Al₂O₃ grains. The reaction between kaolin and Al₂O₃ contributes to increasing the sintering velocity. The ceramic support using cordierite as sintering aid has the acid/alkali corrosion resistance in some degree.

Abstract: A cobalt-free perovskite oxide Ba_0.5Sr_0.5Fe_0.8Cu_0.2O_3−δ (BSFCu) is applied as the cathode material for intermediate temperature micro-tubular solid oxide fuel cells (SOFCs) with asymmetric structure anode. The NiO-YSZ hollow fiber anode as support was prepared by the phase inversion technique. The as-prepared fiber anode shows a special asymmetric structure consisting of porous sponge-like structure in the middle and finger-like porous structure on the inner and outer side. Dense thin YSZ electrolyte membrane and SDC transition layer were deposited on the NiO-YSZ hollow fiber anode by a vacuum-assisted dip-coating and co-sintering technique. Laboratory-sized micro-tubular single cells of NiO-YSZ/YSZ+SDC/BSFCu-SDC were tested at 650-750°C with humidified H2 as the fuel and static ambient air as the oxidant. The peak power densities of 437.2, 326.5 and 214.4 mWcm^-2 can be obtained at 750, 700 and 650°C, respectively. The experimental results indicate that the cobalt-free perovskite oxide BSFCu is a promising cathode material candidate for the developed intermediate temperature micro-tubular SOFC with asymmetric hollow fiber anode.

Abstract: The idealized microstructure of NiO/YSZ anode of solid oxide fuel cell (SOFC) is that YSZ structures the bone of the anode and NiO is segregated by YSZ to keep Ni from congregation. To obtain this microstructure, the mixture of coarse YSZ and fine YSZ was used. The effect of the particle size gradation of YSZ on the microstructure of anode was studied. The results show that the homogenous microstructure can be obtained when the mass ratio of the coarse YSZ (d50＝3.38µm) to the fine YSZ (d50＝0.4µm) is 7:3. The pre-sintering temperature has obvious effect on the porosity of the NiO/YSZ. The bending strength of NiO/YSZ and Ni/YSZ are 123MPa and 85MPa, respectively. The reduction of NiO to Ni has less effect on the bending strength for 40vol%Ni/YSZ (7/3).

Abstract: A green silicon-containing carbon black pigment was synthesized via a sol-geo combustion technique using TEOS and black ink as raw materials. The obtained black pigment was characterized by XRD, TEM and UV-vis absorption spectrophotometer. The results show that the silicon coated with carbon black pigment can be formed at pH ≥ 2 and the black pigment does not change its color after calcinations at 1300 °C in air implying the carbon black is coated completely with SiO2. When pH is 4, the properties of as-prepared sample are similar with the conventional high-temperature pigment. XRD and SEM further confirm that silicon coats with carbon black fully. The silica/ carbon black pigment may represent an opportunity for the applications in the decoration of the high-temperature ceramic.

Abstract: Mesoporous alumina is usually used as adsorption material, catalyst carrier or separation media due to its high adsorption and good thermal stability. However, the nanosized powder trends to aggregation except that its size is in sub-micron scale. The best choice is that the sub-micron alumina particles with mesoporous structure are prepared. In the present work, the mesoporous alumina spheres were prepared by micro emulsion method using aluminium isopropoxide as raw material and water/dimethylbenzene emulsion as reaction media. The obtained powder was characterized by XRD, TEM and BET. The results show that the particles are global. The particles size is in the range of 100 ~ 200 nm to several micrometers. The particle owns the worm-like structure with the pore size of 5 nm. The BET surface area of the mesoporous alumina is 81.8 m²/g. The obtained powder is suit to be used as the packing material in chromatograph.

Abstract: Membrane surface modification is the important method to decrease membrane fouling. The hydrophilic modification of ceramic membrane with nano-sized inorganic coating is prepared by the wet chemical methods. The thin nano coating is not a separating top layer but distributes uniformly on the surface of the membrane pore wall. The coating does not change the structure of the membrane pores. Therefore, water flows on not the pore wall but the nano coating surface. The results show that the water flux of the modified membrane is higher than that of the unmodified membrane despite that the mean pore size of the modified membrane decreases. The “boundary slip” is used to explain this special phenomenon. What generates the slippage The slippage is relative with the molecular layer adhered tightly on the hydrophilic pore wall, the roughness and the surface charge of the nano coating, the interaction between the ions in water and the nano coating, et al.

Abstract: In order to develop porous ceramics with high strength and corrosion resistance as the support for the preparation of asymmetric ceramic membranes, porous ZrO₂-Al₂O₃ composite is designed and fabricated by adding Zr(OH)₄.as sintering aid. The content of Zr(OH)₄, the sintering temperature and the bending strength before and after corrosion of the composite are discussed. The results shows that 10wt% ZrO₂-10wt% Zr(OH)₄ -80wt%Al₂O₃ composite bar fabricated by cold press with the porosity of 32% can be fabricated in 1550°C for 4 h. The bending strength of the composite is 111.2MPa. After corrosion, the quality lose and the bending strength lose is no more than 1%. The tubular composite is suit for the preparation of micro-filtration membrane.

Abstract: Traditional settling height method is used to characterize the stability of suspension by the height of sedimentation when suspension is placed undisturbed for some time. However, for the semi-stable suspension with solid loading in the range of 0.1%~30%, it hardly to differentiate the boundary between the liquid and the suspension. In this work, the settling height method is improved that the deflection of average solid loading in the equidistant portions following the settlement direction is used to characterize the stability of suspension. The equipment was improved to achieve the suspension without the disturbance. And the solid loading of each layer is measured by weighing when it was kept undisturbed for some time. Semi quantitative data can be obtained by the improved settling height method that contributes to estimate the stabilization of the suspension, especially the slight unstable suspension. The improved method contributes to decrease the deflection between the data achieved by different researchers.