Papers by Author: Yong Qing Wang

Abstract: As an oxidized form of graphene, graphene oxide has a variety of oxygen-containing groups together with a laminar structure, showing great potential in various engineering applications. In this work, on the basis of the top-down fabrication principle, superhydrophilic graphene oxide nanosheets with a uniform sheet size of ~50 nm diameter and 0.7 nm thickness were prepared by the modified Hummers method, and using microcrystalline graphite as the carbon source. After chemical oxidation, the obtained graphene oxide nanosheets had a great amount of C-O-C, C-OH and C=O groups and its water contact angle was ~3.9°. This result offers a facile strategy to fabricate superhydrophilic and monolayer graphene oxide nanosheets with well-defined morphology.

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: Alumina microfiltration membrane was prepared with solid particle sintering method by changing the content of TiO2. The membrane flux, rejection to PEG10000 and rupture strength were tested. The results showed that: when the firing temperature is 1400°C, PVA is 2%, TiO2 is 1%, alumina microfiltration membrane flux reached 1.93m3/m2·h, PEG10000 retention rate is 13.5%, and the flexural strength is 74.38MPa.

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: Acicular mullite porous ceramics were synthesis by high-temperature sintering technique. In the present work, Kaolin and industrial aluminum hydroxide were selected as raw materials, AlF₃ used as catalyst. XRD and SEM were used to detect the crystal type and microstructure of prepared mullite ceramics, respectively. The influences of sintering temperature on the growth of crystal, the apparent porosity and compressive strength of the resulting porous ceramics were investigated. The results indicate when sintering temperature ranges from 1250 ~ 1400°C, much acicular mullite crystal appeared in the resulting ceramics. The apparent porosity, the compressive strength and the morphology of the mullite whisker changed obviously with the sintering temperature. When sintering temperature is 1400°C, the porous ceramics showed the maximum compressive strength of ~28 MPa and the maximum apparent porosity of ~63%.

Abstract: Porous acicular mullite ceramic was prepared by in-situ reaction sintering, using clay materials and Al (OH)₃) as the raw materials. The influences of different clay materials on the phase composition, formation of acicular grains and microstructure of prepared porous ceramics were investigated. Results show that the metal oxide impurities were beneficial for the synthesis of acicular mullite. The prepared porous ceramic from Longyan kaolin with high impurity content has the highest mullite content of 93.5%, and composed of interlaced acicular grains with high slenderness ratio of 26.4 and large average diameter of about 0.7μm when sintered 1400°C for 2h. The TEM analysis indicates that the growth direction of acicular grains is along the [001] direction (c axis) of orthorhombic mullite crystals.

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: Micro-tubular solid oxide fuel cell (SOFC) has been fabricated with NiO-YSZ hollow fiber as anode support and SrFe_0.9Sb_0.1O _3−δ-Sm_0.2Ce_0.8O_1.9 (SFSb-SDC) composite cathode. The NiO-YSZ hollow fiber anode was prepared by the immersion-induced phase inversion technique and shows a special asymmetrical structure with long and large finger-like porous structure near the lumen side of the hollow fiber. A thin and dense electrolyte membrane (about 12μm) was deposited on the anode by a vacuum-assisted dip-coating process. The performance of the as-prepared micro-tubular SOFC was tested at 600-800°C with humidified H2 as fuel and ambient air as the oxidant. The peak power densities of 462.8, 336.6 and 201.4 mWcm^-2 can be obtained at 800, 700 and 600°C, respectively. The experimental results indicate that the cobalt-free SFSb was a promising cathode material and the prepared YSZ-based micro-tubular SOFC has potential applications as power sources for portable devices.