Papers by Author: Jian Er Zhou

Abstract: The Nb₂O₅-Al₂O₃ binary system ceramics were prepared by high temperature solid state reaction sintering, using Nb₂O₅ and Al₂O₃ micro powder as the raw materials. The samples were characterized by XRD, SEM, thermodilatometric analysis and mechanical strength measurement. The influences of Al₂O₃ content on the phase composition, microstructure, thermal expansion properties and bending strength were investigated. Results show the samples shows obvious changes in phase composition and microstructure with the addition of Al₂O₃ from 2.5% to 15%. The pure Nb₂O₅ ceramic is composed of monoclinic phase Nb₂O₅, while different monoclinic aluminum niobates were formed with different Al₂O₃ additions. Obvious microcracking can be observed for the samples without and with 2.5% and 7.5% Al₂O₃ additions. The addition of Al₂O₃ leads to significant increase of bending strength, and all the samples keep relatively low thermal expansion coefficient (TEC). The Nb₂O₅-Al₂O₃ binary system ceramics with ultra low TEC (0.55~0.86×10^-6°C^-1) and improved bending strength (50.4~70.6MPa) could be obtained with the addition of 7.5~15% Al₂O₃ when sintered at 1390°C for 2h.

Abstract: Smooth and dense films of CaTiO₃ were prepared on the glass substrate by a sol-gel dip coating method. Characterization of the product was carried out by different techniques such as powder X-ray diffraction (XRD), scanning electron microscope (SEM) and UV–vis optical spectroscopy. The results showed that pH and water contents had a great influence on morphology of CaTiO₃ film. When water content is 0.128 mol at PH=1.56, CaTiO₃ film presents an absorption in the UV region and the band gap is estimated to 3.35 ev. The results show the large potential of this material in electronic structure.

Abstract: C/C composite and TC4 alloy were successfully brazed using 70Ag28Cu2Ti (wt. %) as filler metal at brazing temperature 820 º°C~920 °C for soaking time 5 min ~30 min. The effects of brazing parameters on the microstructures and phase composition and the fracture modes of the brazed joints were investigated by SEM and XRD. The mechanical performances of the brazed joints were measured by a universal mechanical testing machine. The results show that the maximum shear strength of the brazed joint is 28 MPa at brazing temperature 860°C and soaking time 10min. Fracture surface analysis of the brazed joints indicates that the position of the fracture surface is related to the orientation of carbon fiber. The brazed joints are fractured in the C/C composite when the carbon fiber is parallel to the joined surface, and the brazed joints are fractured at the C/C composite / 70Ag28Cu2Ti interface when the carbon fiber is vertical to the joined surface.

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: 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: Micro-tubular solid oxide fuel cell (SOFC) has been fabricated with NiO-YSZ hollow fiber as anode support and La_0.6Sr_0.4Co_0.8Cu_0.2O_3−δ-Sm_0.2Ce_0.8O_1.9 (LSCCu-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 porous sponge-like structure in the middle and finger-like structure on the inner and outer 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 hollow fiber SOFC (HF-SOFC) was tested at 600-800°C with humidified H₂ as fuel and ambient air as the oxidant. The peak power densities of 531.1, 362.5 and 214.6mWcm^-2 can be obtained at 800, 700 and 600°C, respectively. The good performance at intermediate temperature (IT) indicates promising applications as power sources for portable devices for the prepared YSZ-based micro-tubular SOFCs with LSCCu-SDC composite cathode.

Abstract: To explain the deformation during the co-sintering of NiO/YSZ-YSZ coating, the sintering shrinkage of NiO, NiO/YSZ and YSZ were measured by dilatometer. The coefficient of deformation variable (CDV, α) is defined to describe the difference of the sintering behaviors between the layers constrained.

Abstract: Membrane surface modification is the important method to decrease membrane fouling. Recent efforts have been made to develop the hydrophilic modified ceramic membrane with nano-sized inorganic coating in our research group. In the modified membrane, the nano coating does not form a separating layer, just distributes uniformly on the surface of the membrane pore wall. It results in that: (1) if the feed is water, the water flux of the modified membrane is higher than that of the unmodified one despite the fact that the mean membrane pore size decreases after the modification; (2) if the feed is oily emulsion, the steady flux is obtained in a short time and keeps in the following time. The flux is far higher than that of the unmodified one because the hydrophilic nano coating prevents the cake from forming on the membrane surface. The nano-sized metal oxide modification application in the membrane technology not only expands the newly research area of the membrane technology but also makes the modified ceramic membrane have a good perspective application in the industry. This paper will introduce the development of the modified membrane with nano inorganic coating and give a clear future research direction.