Xiao Zhen Zhang

Preparation and Characterization of Coated Carbon Black Pigment

Black pigment is an important pigment in the ceramic decoration. The traditional black pigment is spinel type matter containing Co, Fe or Cr elements. Carbon black is the best black pigment and is nontoxic. However, carbon black is oxygenated in the ceramic sintering process at atmosphere. Carbon black enclosed in the crystal latter of ZrSiO4 was reported. However, the content of carbon black is little which decreases the color generation. Carbon black coated with SiO2 was prepared by sol-gel method using combustion method using SiO2 sol and black ink as raw materials. The obtained black pigmenSubscript textt was characterized by XRD, TEM and ultraviolet-visible spectrophotometer. The results show that the black pigment does not change its color after calcinations at 1300 °C at atmosphere implying the carbon black is coated completely with SiO2.

Effect of Al2O3 Addition on Microstructure, Thermal Expansion and Mechanical Properties of Ta2O5 Ceramics

The Ta2O5-based ceramics were prepared by dry pressing/sintering technique using Ta2O5 and Al2O3 as the starting materials. The present work investigated the effect of alumina (Al2O3) additions on the composition, microstructure, thermal expansion coefficient (TEC) and bending strength of Ta2O5 ceramics. The thermal expansion of the samples was measured by the dilatometry method. It was found that Al2O3 additions can effectively inhibit the β to α phase transformation in Ta2O5 ceramics. Orthorhombic AlTaO4 as the minor phase formed when 2.5 and 7.0 wt% Al2O3 was added. The addition of Al2O3 results in obvious change of TEC and an increase of bending strength. This work demonstrated that the addition of Al2O3 is an effective way to modify the TEC and mechanical strength of Ta2O5 ceramics.

Particle Size and Chroma Control of CoAl2O4 Pigment

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.

Preparation and Characterization of Nb2O5-Al2O3 System Ceramics with Different Al2O3 Additions

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.

Preparation of Carboxymethyl Cellulose Sodium/PEI Nanofiltration Membrane

Carboxymethyl cellulose (CMC) sodium with negatively charged character was used as functional layer of polyetherimide (PEI) ultrafiltration membrane. The preparation parameter such as CMC concentration, cross-linking agent concentration and curing temperature are studied in detail. When the composite membrane was prepared under optimized conditions and tested at 0.4 MPa and 20 °C, the flux of the composite NF membrane was about 3 L/m2h and the MgCl2 rejection of it was about 87%. The composite membrane showed classical negatively charged membrane character which had higher rejection to high valent anion.

Investigation of Cobalt-Free Cathode Material Ba0.5Sr0.5Fe0.8Cu0.2O3−δ for Micro-Tubular SOFC with Asymmetric Structure Anode

A cobalt-free perovskite oxide Ba0.5Sr0.5Fe0.8Cu0.2O3−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.

Micro-Tubular Solid Oxide Fuel Cell with Graded Anode and Cobalt-Free SrFe0.9Sb0.1O 3−δ Perovskite Cathode

Micro-tubular solid oxide fuel cell (SOFC) has been fabricated with NiO-YSZ hollow fiber as anode support and SrFe0.9Sb0.1O 3−δ-Sm0.2Ce0.8O1.9 (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.

Micro-Tubular Solid Oxide Fuel Cell with Asymmetric Structure Anode and La0.6Sr0.4Co0.8Cu0.2O3−δ Perovskite Cathode

Micro-tubular solid oxide fuel cell (SOFC) has been fabricated with NiO-YSZ hollow fiber as anode support and La0.6Sr0.4Co0.8Cu0.2O3−δ-Sm0.2Ce0.8O1.9 (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.

Preparation of Highly Permeable Al2O3 Hollow Fiber Membrane via Phase Inversion Method with Ethanol as External Coagulant

Highly permeable porous alumina (Al2O3) hollow fiber membranes have been developed by a combined phase inversion and sintering technique. Ethanol substituting for water was used as the external coagulant in order to prepare Al2O3 hollow fiber membranes with low trans-membrane resistance. The prepared Al2O3 membranes show a special asymmetric structure with an outer skin layer, highly porous inner surface and sub-layer composed of long and large finger-like pores. The influences of sintering temperature on the average pore size, N2 permeability and bending strength were investigated. Results show that Al2O3 hollow fiber membranes with higher permeability can be prepared using ethanol as the external coagulant. The prepared Al2O3 hollow fiber membranes show a N2 permeability of 871.5 m3·m-2·h-1·bar-1 and a bending strength of 91.4 MPa when sintered at 1550°C for 5h.

Influence of Operational Parameters on Oil-Water Separation Efficiency of Titanium Oxide Modified Alpha-Alumina Microfiltration Membrane

During oil-water separation process, the influence of the operational parameters such as transmembrane pressure, crossflow velocity and feed temperature on the oil-water separation efficiency of TiO2 modified α-alumina microfiltration membrane was studied. The results show that the permeation flux of the membrane is 371.68 L•m-2•h-1 and the oil content in the permeation is 9.63 mg•L-1 when the TMP is 0.15 MPa, the crossflow velocity is 5.89 m•s-1 and the feed temperature is 30°C.