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A novel layered perovskite oxide PrBaCuCoO5+i (PBCCO) is employed as a potential cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Thermal expansion and electrochemical performance on samarium-doped ceria (SDC) electrolyte are evaluated. The thermal expansion coef- ficient (TEC) of PrBaCuCoO5+i (PBCCO) is close to that of SDC electrolyte and electrical conductivity of PrBaCuCoO5+i (PBCCO) reaches the general required value of cathode material. Symmetrical electro- chemical cell with the configuration of PrBaCuCoO5+i (PBCCO)/SDC/PrBaCuCoO5+i (PBCCO) applied for the impedance studies, the area specific resistance of PrBaCuCoO5+i (PBCCO) cathode is as low as 0.047 � cm2 at 700

Bulk porous mullite supports for ceramic membranes were prepared directly using a mixture of industrial waste fly ash and bauxite by dry-pressing, followed by sintering between 1200 and 1550 degrees C. The effects of sintering temperature on the phase composition and shrinkage percent of porous mullite were studied. The XRD results indicate that secondary mullitization reaction took place above 1200 degrees C, and completed at 1450 degrees C. During sintering, the mixture samples first shrunk, then expanded abnormally between 1326 and 1477 degrees C, and finally shrunk again above 1477 degrees C. This unique volume self-expansion is ascribed to the secondary mullitization reaction between bauxite and fly ash. More especially, the micro-structural variations induced by this self-expansion sintering were verified by SEM, porosity, pore size distribution and nitrogen gas permeation flux. During self-expansion sintering, with increasing temperature, an abnormal increase in both open porosity and pore size is observed, which also results in the increase of nitrogen gas flux. The mineral-based mullite supports with increased open porosity were obtained. Furthermore, the sintered porous mullite membrane supports were characterized in terms of thermal expansion co-efficient and mechanical strength.

Titanium alloys are used widely for their high strength-to-weight ratio and good corrosion resistance characteristics. However, these alloys have been classified as ‘difficult-to-machine’ materials. In order to improve the cutting efficiency in machining the titanium alloys, a new WC matrix composite tool material was prepared by hot pressing technology in this research. The cutting performance of the newly developed tool material in machining titanium alloy Ti6Al4V was investigated. The factors which influence the wear modes of the tool were investigated and the wear mechanisms were analyzed. Results show that the high temperature and mechanical friction are the main factors in the wear process. The wear mechanisms of the tool in machining titanium alloys are adhesion wear and abrasive wear.

In order to develop cost-effective method to prepare ceramic interconnect membrane for solid oxide fell cell stacks, the triple-phase composites of NiO/Sm 0.2 Ce 0.8 O 2− δ /La 0.7 Ca 0.3 Cr 0.97 O 3− δ with the weight ratios of 6:4: x ( x = 0, 2, 3, 4, 5) were, respectively prepared, and then examined as novel anode supports. The sintering character, microstructure, electrical conductivity, fracture strength, and thermal expansion coefficient of the anodes were, respectively investigated in detail as a function of La 0.7 Ca 0.3 Cr 0.97 O 3− δ content. Results indicate the above-mentioned performances of NiO/Sm 0.2 Ce 0.8 O 2− δ /La 0.7 Ca 0.3 Cr 0.97 O 3−δ anode at x ≤ 3 have no significant reduction, and are still acceptable for the practical requirements for solid oxide fell cells. Furthermore, by using a simple and cost-effective drop-coating/co-firing process, dense La 0.7 Ca 0.3 Cr 0.97 O 3− δ interconnect membrane was successfully prepared on the anode support of NiO/Sm 0.2 Ce 0.8 O 2− δ /La 0.7 Ca 0.3 Cr 0.97 O 3−δ at x = 3. This work presents a simple technical route for developing dense interconnect membranes for Sm 0.2 Ce 0.8 O 2− δ -based fuel cell stacks.

In order to develop a simple and cost-effective route to fabricate proton-conductor intermediate-temperature SOFCs, a dense BaZr0.1Ce0.7Y0.2O3−δ (BZCY) electrolyte was fabricated on a porous anode by in situ drop-coating. The PrBaCuFeO5+δ (PBCF) composite oxide with layered perovskite structure was synthesized by auto ignition process and examined as a novel cathode for proton-conductor IT-SOFCs. The single cell, consisting of PBCF/BZCY/NiO-BZCY structure, was assembled and tested from 600 to 700 °C with humidified hydrogen (∼3% H2O) as the fuel and the static air as the oxidant. An open-circuit potential of 1.01 V and a maximum power density of 445 mW cm−2 at 700 °C were obtained for the single cell. A relatively low interfacial polarization resistance of 0.15 Ω cm2 at 700 °C indicated that the PBCF is a promising cathode for proton-conductor IT-SOFCs.

Unique ZrO 2 crystals within pores were prepared by a sol–gel-hydrothermal method and characterized by XRD, TG/DTA, TEM, SEM, and N 2 adsorption–desorption isotherms. Results show that the dried sol–gel was converted into monoclinic zirconia crystals after calcined above 550 °C. The crystal sizes of the zirconia single crystal were in the range of 20–70 nm. A number of irregular pores were embedded within the zirconia crystals. This unique structure was obtained due to the combination of sol–gel and hydrothermal treatments.

BaCe0.8Y0.2O3−δ and BaCe0.9−xYxNb0.1O3−δ (x = 0.1, 0.15, 0.2, 0.25, 0.3, 0.35) were prepared by a solid-state reactions. It was found that the BaCe0.8Y0.2O3−δ samples decomposed into CeO2 and BaCO3 after being exposed in the atmosphere (3% CO2 + 3% H2O + 94% N2) at 700 °C for 10 h. However, samples containing Nb remains unchanged in the same conditions, demonstrating a better stability in the presence of CO2 and H2O. The conductivity of BaCe0.9−xYxNb0.1O3−δ increased with the increase of Y content (x ≤ 0.30), and the highest value was observed at x = 0.30 where a significant decrease in conductivity took place at x = 0.35. The conductivity of BaCe0.6Y0.3Nb0.1O3−δ reaches 0.01 S/cm in humid hydrogen at 700 °C, slight lower than BaCe0.8Y0.2O3−δ, 0.012 S/cm in the same conditions. Fuel cell with BaCe0.6Y0.3Nb0.1O3−δ as-prepared was successfully prepared and humidified hydrogen was supplied as fuels in evaluating the fuel cell performance. The open circuit voltage, peak power density and interfacial resistance at 700 °C were 1.02 V, 345 mW/cm2 and 0.27 Ω cm2, respectively.

Simple, easily sintered perovskite oxide as a novel interconnect material for solid oxide fuel cells (SOFCs) was evaluated at a SOFC co-firing temperature (1400 °C). Chemical compatibility, sintering character, electrical conductivity and thermal expansion were investigated to characterize the compatibilities of La 0.7 Ca 0.3 Cr 0.97 O 3− δ (LCC97) with Y 0.16 Zr 0.84 O 2− δ (YSZ), NiO, Sm 0.2 Ce 0.8 O 2− δ (SDC), La 0.8 Sr 0.2 MnO 3− δ (LSM), and BaZr 0.1 Ce 0.7 Y 0.2 O 3− δ (BZCY), respectively. The XRD analysis indicates LCC97 chemically incompatible with BZCY. The mixtures of LCC97/SDC and LCC97/NiO, respectively, exhibit high relative densities of 97.6% and 96.2% after sintering at 1400 °C for 5 h in air. However, the samples of LCC97/YSZ and LCC97/LSM only have poor sintering abilities. The samples of LCC97 mixed with LSM, SDC, NiO and YSZ, respectively, have a decreasing electrical conductivity of 24.0 S cm −1 , 12.2 S cm −1 , 7.8 S cm −1 and 0.17 S cm −1 at 850 °C in air, which are all much lower than that of the LCC97 sample (62.0 S cm −1 ). Different mixing slightly increases the TEC value of LCC97. Results indicate that, under SOFC co-firing conditions, the novel interconnect material LCC97 has desired compatibilities with SDC and NiO, while it displays poor compatibilities with YSZ and LSM.

Protonic ceramic membrane fuel cells (PCMFCs) based on oxide proton conductors exhibit more advantages than traditional solid oxide fuel cells (SOFCs) based on oxygen-ion conducting electrolytes, such as low activation energy and high energy efficiency. In order to develop a simple and cost-effective route to fabricate PCMFCs with SrCo 0.9 Sb 0.1 O 3− δ (SCS) cubic perovskite cathode, a dense BaCe 0.5 Zr 0.3 Y 0.16 Zn 0.04 O 3− δ (BCZYZn) electrolyte was fabricated in situ metal oxide on a porous anode support by gel-casting and suspension spray, which is cost-effective, easy to realize, and suitable for mass-production. The key part of this process is to directly spray well-mixed suspension of BaCO 3 , CeO 2 , ZrO 2 , Y 2 O 3 and ZnO instead of pre-synthesized BCZYZn ceramic powder on the anode substrate. With SCS cubic perovskite cathode synthesized by gel-casting on the bi-layer, single cells were assembled and tested with H 2 as fuel and the static air as oxidant. An open-circuit potential of 0.987 V, a maximum power density of 364 mW cm −2 , and a low polarization resistance of the electrodes of 0.07 Ω cm 2 was achieved at 700 °C.

In order to reduce fabrication cost and process time, porous cordierite membranes with micro-filtration function were prepared by a simple co-sintering process from the low-cost industrial grade powder. Aqueous medium ball-milling was used as the effective classification method to obtain the fine powders with narrow particle size distribution. Then, the sintering characteristics of the selected two types of cordierite powders were studied by dilatometric measurements. And the effects of co-sintering temperature on the main properties of the prepared membranes were investigated such as micro-structure morphology and pore size distribution. The results prove that the co-sintering of two-layer cordierite membranes (45.0 and 15.0 μm thick) was feasible because of their low difference in sintering shrinkage behavior. The co-sintered tubular cordierite micro-filtration membranes showed some characteristics such as crack-free morphology, average pore diameters of 1.55 and 2.17 μm, 60.0 μm in total thickness and narrow pore size distribution.

In order to develop cost-effective macro-porous ceramic membrane supports, the porous supports with large pore size were prepared from the coarse industrial mullite-corundum powder (M) with the mixture of kaolin and basic carbonate magnesium (KM) as sintering additive. Crystalline phase transition mechanism of the sintering additive and the supports was studied respectively by TG/DTA and XRD. The results confirm that at 1200–1400 °C α-cordierite formed from the sintering additive, and that above 1400 °C α-cordierite decomposed into mullite and liquid glassy phase. Sintering characteristic of the coarse mullite-corundum compacts was revealed as a function of KM/M mass ratio. The result indicates that the sintering ability of coarse mullite-corundum improved because of the produced liquid silica-rich glassy phase via the decomposition of KM-derived α-cordierite. In addition, the open porosity of the macro-porous mullite-corundum could be effectively tailored by choosing the KM/M mass ratio, the pore-former/M mass ratio and sintering temperature. The fabricated mullite-based macro-porous supports showed an average pore size of 26.21 μm and nitrogen flux of 2.375 × 104 m3/(m2 h), as well as good mechanical and thermal properties.

Ba(Ce 0.8− x Sn x )Y 0.2 O 3− σ ( x = 0, 0.05, 0.10, 0.15, 0.20, 0.25) powders were prepared by solid state reaction method. The powder samples with Sn element still keep pervoskite-type configuration after boiling in water for 3 h while the BaCe 0.8 Y 0.2 O 3− σ powders apparently decompose into amorphous phases, which indicates the oxides doped with Sn exhibit good chemical stability. Thermal gravity analysis indicates the compounds with Sn possess better chemical stability in CO 2 compared with BaCe 0.8 Y 0.2 O 3− σ . The BaCe 0.7 Sn 0.1 Y 0.2 O 3− σ sample displays a conductivity of 0.007 S/cm at 700 °C in wet hydrogen. Although the relative density of BaCe 0.8 Y 0.2 O 3− σ only reaches 88.3% after sintering at 1400 °C, the Ba(Ce 0.8− x Sn x )Y 0.2 O 3− σ samples exhibit relative densities as high as 96.0%. A fuel cell with BaCe 0.7 Sn 0.1 Y 0.2 O 3− σ electrolyte was prepared by a suspension spray combining with in situ sintering method and tested in humid hydrogen. Its output and interface resistance are 470 mW/cm 2 and 0.13 Ω cm 2 at 700 °C, respectively. The short-term performance test also indicates it has good stability as well as desirable compatibility between electrolyte and electrodes.

La0.7–xSmx+0.02Ca0.3CrO3-δ (0≤x≤0.4) powders with A-site excessive perovskite structure were synthesized by auto-ignition process and characterized. X-ray diffraction (XRD) patterns of samples after sintering at 1400 °C for 4 h were indexed as tetragonal structure. The relative densities were all above 96% although decreased slightly with the increasing content of samarium, indicating that the excessive A-site element was helpful to enhance their sinterability. Conductivities of the specimens in air increased with increasing content of samarium. The conductivity of La0.6Sm0.12Ca0.3CrO3-δ was 33.6 S/cm in air at 700 °C which was about 1.7 times as high as that of La0.7Ca0.3CrO3–δ (20.1 S/cm). Average thermal expansion coefficients (TECS) of the specimens increased from 11.06×10−6 to 12.72×10−6 K−1 when x increased from 0 to 0.4, and they were close to that of Y doped ZrO2 (YSZ). La0.7–xSmx+0.02Ca0.3CrO3–δ (0.1≤x≤0.3) were good choices for intermediate temperature solid oxide fuel cells (IT-SOFCs) interconnect materials.

BaZr0.1Ce0.7Y0.2O3−δ (BZCY7) perovskite oxide was prepared by gel-casting and solid-state reaction techniques as proton-conducting electrolyte for low-temperature solid oxide fuel cells (LT-SOFCs). X-ray diffraction analysis indicated that the phase formation temperature of BZCY7 powder synthesized by gel-casting was 100–150 °C lower than that by solid-state reaction method. The BZCY7 electrolytes prepared by gel-casting exhibited better sintering activity and higher electrical conductivity. After sintering at 1550 °C for 5 h, the relative density and electrical conductivity of the gel-casting derived BZCY7 reached 95% and 5 × 10−3 S/cm in H2 (∼3% H2O) at 500 °C. However, for the solid-state reaction method, the sample had a relative density of 86% and electrical conductivity of 2 × 10−3 S/cm under the same condition.

We used HCl and NH3 gases to adjust the pH value of the suspension prepared by mixing the Pb(Ac)2 and K2CrO4 aqueous solutions, and found the structure, morphology and size of the initial precipitates changed at room temperature. In the acid condition, when the ratio of [Pb2+]/[CrO42−] was 1:1, 1:5 or 1:10, the initial orthorhombic PbCrO4 precipitates would translate to the monoclinic PbCrO4. And the aspect ratio of the obtained particles increased with a decrease in the ratio of [Pb2+]/[CrO42−]. In the basic condition, with the increase in the concentration of the hydroxyl ions, the products converted from the orthorhombic PbCrO4 to the monoclinic Pb2CrO5. The phenomena and results provide the information of the phase formation and transition in the Pb–Cr–O system, and enrich the field of the crystal growth.

BaCe 0.8− x Nb x Sm 0.2 O 3− δ ( x = 0, 0.05, 0.1) powders were prepared by a solid-state reaction method. After boiling in water for 3 h, the BaCe 0.8 Sm 0.2 O 3− δ powders obviously decomposed into CeO 2 and BaCO 3 while the other two powder samples containing Nb element in B site were hardly affected. According to thermal gravity analysis, the BaCe 0.8 Sm 0.2 O 3− δ powders displayed obvious reaction with CO 2 while the BaCe 0.7 Nb 0.1 Sm 0.2 O 3− δ powders were quite stable. Moreover, the sintered BaCe 0.7 Nb 0.1 Sm 0.2 O 3− δ sample exhibited a conductivity value of 0.0026 S/cm at 700 °C in wet hydrogen. A fuel cell with BaCe 0.7 Nb 0.1 Sm 0.2 O 3− δ as electrolyte was prepared by a suspension spray combining with in situ sintering method and tested in hydrogen from 600 °C to 700 °C. The peak power densities respectively reached 245 mW/cm 2 at 700 °C, 110 mW/cm 2 at 650 °C and 75 mW/cm 2 at 600 °C. The interface resistances were 0.31 Ω cm 2 at 700 °C, 0.43 Ω cm 2 at 650 °C and 1.2 Ω cm 2 at 600 °C, correspondingly.

The SrCo0.9Sb0.1O3–δ (SCS) composite oxide with cubic perovskite structure was synthesized by a modified Pechini method, and examined as a novel cathode for intermediate-to-low temperature solid oxide fuel cells (ILT-SOFCs). At 700°C and under open-circuit condition, a symmetrical SCS cathode on Sm0.2Ce0.8O1.9 (SDC) electrolyte showed a low polarization resistance (Rp) of 0.09 Ωcm2 in air. A porous layer of SCS was deposited on an anode-supported fuel cell, consisting of a ∼30 μm thick dense electrolyte of SDC prepared by a cost-effective dip coating process, and an NiO-SDC cermet as an anode (Ni-SDC/SDC/SCS). The single cells obtained were tested with humidified (∼3% H2O) hydrogen as fuel and static air as oxidant. A high open-circuit voltage of 0.86 V, a maximum power density of 354 mW/cm2, and a low polarization resistance of the electrodes of 0.13 Ωcm2 was achieved at 650°C.

In order to develop co-fired yttrium-stabilized zirconia (YSZ)-based solid oxide fuel cells (SOFCs), stable and easily sintered Y 0.7 Ca 0.3 Cr 1− x Zn x O 3−δ ( x = 0–0.15) perovskite oxides were synthesized by the microwave-aided sol–gel process and then examined as novel ceramic interconnect materials. (The characterizations focused on phase structure, sintering behavior, relative density, electrical conductivity and thermal expansion.) The XRD analysis indicates that a pure orthorhombic perovskite phase was obtained for all the samples. Cell volume decreases as x increases from 0 to 0.10. The Y 0.7 Ca 0.3 Cr 0.9 Zn 0.1 O 3– δ (YCCZ10) powder exhibited the best sintering ability, and a relative density of 96.6% could be obtained for the sample sintered at 1400 °C for 4 h in air. The electrical conductivities of the specimens increase with the Zn 2+ content at x ≤ 0.10, but then remarkably decrease at x = 0.15, which might relate to the over-range of the substitution amount of Zn (0.15) for Cr position. YCCZ10 shows a remarkable electrical conductivity of 20.9 S cm −1 at 850 °C in air, and a very suitable thermal expansion coefficient value of 10.8 × 10 −6 K −1 (YSZ: ∼10.8 × 10 −6 K −1 ). These investigations have indicated that YCCZ10 is a promising interconnect material for co-fired YSZ-based SOFCs.

BaCe 0.7 Nb 0.1 Gd 0.2 O 3− δ (BCNG) and BaCe 0.8 Gd 0.2 O 3− δ (BCG) were synthesized by solid-state reaction method. The samples obtained were exposed in 3% CO 2 + 3% H 2 O + 94% N 2 at 700 °C for 20 h in order to evaluate their chemical stability. It was found that BCNG exhibited adequate chemical stability while BCG decomposed and impurities were observed in the final products. Additionally, the BCNG demonstrated similar behavior as BCG in high-temperature thermal stability and in TEC and displayed a conductivity of 0.007 S cm −1 at 700 °C in humid hydrogen which was slightly lower than BCG (0.009 S cm −1 ) at the same conditions. Fuel cells with BCNG as electrolyte were successfully fabricated and the thickness of BCNG layer can be easily adjusted as lower as 10 μm by a simple all-solid-state process. The fuel cells exhibited OCV as high as 1.0 V at 700 °C with maximum output power 340 mW cm −2 and interfacial resistance as low as 0.51 Ω cm 2 .

Relatively low temperature (1150–1300 °C) sintering characteristics and electric conductivities of La0.7Ca0.3Cr0.97O3 with a slight Cr deficiency of 0.03, prepared by an auto-ignition process, have been discussed. The material could reach 94.3% relative density at 1200 °C for 5 h in air, which is about 200 °C lower than that of with no Cr deficiency. XRD results indicated that pure perovskite phase was formed after sintered at the temperature range of 1150–1300 °C. The sample sintered at 1250 °C had the maximum conductivity of 62.0 S cm−1 at 850 °C in air, which is about 2.6 times as high as that of La0.7Ca0.3CrO3 with no Cr deficiency. In pure H2, it got the maximum electrical conductivity of 3.3 S cm−1 at 850 °C as sintered at 1200 °C. The TEC of the material was about 11.4 × 10−6 K−1, which is very compatible to that of other common used SOFC components. Therefore, it is a simple and cost-effective interconnect material for SOFCs.

The perovskite-type Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ –BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ (BSCF–BZCY) composite oxides were synthesized by a modified Pechini method and examined as a novel composite cathode for intermediate-to-low temperature protonic ceramic membrane fuel cells (ILT-PCMFCs). Thin proton-conducting BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ (BZCY) electrolyte and NiO–BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ (NiO–BZCY) anode functional layer were prepared over porous anode substrates composed of NiO–BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ by a one-step dry-pressing/co-firing process. A laboratory-sized quad-layer cell of NiO–BZCY/NiO–BZCY(∼50 μm)/BZCY(∼20 μm)/BSCF–BZCY(∼50 μm) was operated from 550 to 700 °C with humidified hydrogen (∼3% H 2 O) as fuel and the static air as oxidant. A high open-circuit potential of 1.009 V, a maximum power density of 418 mW cm −2 , and a low polarization resistance of the electrodes of 0.10 Ω cm 2 was achieved at 700 °C. These investigations have indicated that proton-conducting BZCY electrolyte with BSCF perovskite cathode is a promising material system for the next generation solid oxide fuel cells (SOFCs).

In order to develop a simple and cost-effective route to fabricate protonic ceramic membrane fuel cells (PCMFCs) with layered SmBaCo2O5+x (SBCO) cathode, a dense BaZr0.1Ce0.7Y0.2O3−δ (BZCY) electrolyte was fabricated on a porous anode by in situ screen printing. The porous NiO–BaZr0.1Ce0.7Y0.2O3−δ (NiO–BZCY) anode was directly prepared from metal oxide (NiO, BaCO3, ZrO2, CeO2 and Y2O3) by a simple gel-casting process. An ink of metal oxide (BaCO3, ZrO2, CeO2 and Y2O3) powders was then employed to deposit BaZr0.1Ce0.7Y0.2O3−δ (BZCY) thin layer by an in situ reaction-sintering screen printing process on NiO–BZCY anode. The bi-layer with 25 μm dense BZCY electrolyte was obtained by co-sintering at 1400 °C for 5 h. With layered SBCO cathode synthesized by gel-casting on the bi-layer, single cells were assembled and tested with H2 as fuel and the static air as oxidant. A high open-circuit potential of 1.01 V, a maximum power density of 382 mW cm−2, and a low polarization resistance of the electrodes of 0.15 Ω cm2 was achieved at 700 °C.

The SrCo0.9Sb0.1O3-delta (SCS) composite oxide with cubic perovskite structure was synthesized by a modified Pechini method and examined as a novel cathode for protonic ceramic membrane fuel cells (PCMFCs). At 700 degrees C and under open-circuit condition, symmetrical SCS cathode on BaZr0.1Ce0.7Y0.2O3-delta (BZCY7) electrolyte showed low polarization resistances (R-p) of 0.22 Omega cm(2) in air. A laboratory-sized tri-layer cell of NiO-BZCY7/BZCY7/SCS was operated from 500 to 700 degrees C with humidified hydrogen (similar to 3% H2O) as fuel and the static air as oxidant. A high open-circuit potential of 1.004V, a maximum power density of 259mWcm(-2), and a low polarization resistance of the electrodes of 0.14 Omega cm(2) was achieved at 700 degrees C.

Porous cordierite ceramics were prepared from a mixture of coal fly ash and basic magnesium carbonate at 1100–1350°C. Porosity, flexural strength and thermal expansion coefficient of the samples sintered at 1300°C were estimated to be 26%, 65 MPa and 4.21×10−6/°C, respectively. The kinetics of the formation progress was investigated by stepwise isothermal dilatometry (SID) accompanied with XRD, SEM and porosity measurement. It was found that the isothermal shrinkage data from SID could be well analyzed to get kinetic parameters according to the empirical rate equation developed by Makipirtti-Meng, dY/dt = nk(T)Y(1 − Y)(Y/1 − Y)n/1, where Y is the fractional shrinkage during the sintering process and n is a dimensionless component. The apparent activation energy ΔE values for 900–1000°C and 1050–1150°C were 1294 and 1778 kJ/mol, respectively.

LiF-doped TiO{sub 2} was prepared by hydrolysis of tetrabutyl titanate in a mixed LiF-H{sub 2}O-alcohol solution. The prepared LiF-doped TiO{sub 2} powders were characterized by X-ray diffraction (XRD), differential thermal analysis-thermogravimetry (DTA-TG), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy and photoluminescence spectra (PL). The photocatalytic activity was evaluated by the decomposition of trichloromethane (CHCl{sub 3}). The results showed that LiF-doping increased the amount of O{sub OH} and oxygen vacancy (OV) on the surface of TiO{sub 2}, which were beneficial to photocatalytic activity. LiF-doping inducted the new isolated energy band located above the valence band of TiO{sub 2}, which extended the absorption region of TiO{sub 2} to visible light. The results of photocatalytic reaction showed that the photocatalytic activity of LiF-doped TiO{sub 2} was 2.5 times higher than that of pure TiO{sub 2}.

A thin Ba3Ca1.18Nb1.82O9−δ (BCN18) membrane electrolyte was prepared by a novel and facile method on a NiO–BCN18 anode substrate. The interesting aspect of the method was the adoption of a in situ reaction of BaCO3, CaCO3, and Nb2O5 on the anode substrate to prepare a dense BCN18 membrane. The BCN18 membrane obtained, which was about 15 μm in thickness and showed high chemical stability against H2O and CO2, attained a high density after sintering at 1400°C. The elemental composition of the BCN18 membrane prepared was identified by energy-dispersive X-ray spectroscopy analysis. With La0.7Sr0.3FeO3−σ (LSF) as the cathode, the fuel cell performance with the structure of Ni–BCN18/BCN18/LSF was studied.

A green BaZr 0.1 Ce 0.7 Y 0.2 O 3− δ (BZCY) electrolyte layer was deposited on porous anode substrate (BZCY:NiO = 35:65, in weight ratio) by a suspension spray. In this process, the suspension was prepared by directly ball-milling the mixed BaCO 3 , CeO 2 , ZrO 2 and Y 2 O 3 powders in ethanol for 24 h. Then the bi-layers were co-sintered at 1400 °C for 5 h in air to obtain dense and uniform electrolyte membrane in the thickness of 10 μm. With Nd 0.7 Sr 0.3 MnO 3− δ cathode, a fuel cell was assembled. It was tested from 600 °C to 700 °C using humid hydrogen as fuel and air as oxidant. The cell at 700 °C exhibited 1.02 V for open circuit voltage (OCV), 450 mW/cm 2 for peak output and 0.18 Ω cm 2 for electrode polarizations under open circuit conditions, respectively. The results indicate that it is feasible to fabricate thin electrolyte membrane for solid oxide fuel cells (SOFCs) by this simple, cost-effective and efficient technique.

Anode coking problem of solid oxide fuel cell (SOFC) when using hydrocarbon fuels has been the major barrier for the practice and commercialization of well-developed high performance SOFC. In this work, based on fuels consideration, we chose liquid methanol as the candidate fuel for SOFC with the configuration of NiO/SDC–SDC–SSC/SDC. For comparison, traditional fuels, hydrogen and ammonia, were tested. With methanol as fuel, the maximum power densities were 698, 430 and 223 mW cm −2 at 650, 600 and 550 °C, respectively, which were higher than that with ammonia and lower than that of hydrogen. The electrochemical properties of the cells with the three fuels were investigated by AC impedance spectroscopy. The long-term stability of the cell with methanol, methane and ethanol were also studied at a constant output voltage of 0.5 V.

In order to develop a cost-effective route to fabricate solid oxide fuel cells (SOFCs), a dense Ce 0.8 Sm 0.2 O 1.9 (SDC) electrolyte was fabricated on a porous cathode based on a mixed conducting La 0.8 Sr 0.2 FeO 3− δ (LSF) via a suspension spray/co-firing process. For the purpose of shrinkage matching between the cathode support and the electrolyte membrane, nano-SDC1 powder for the easily sinterable electrolyte was synthesized with ammonia as the precipitant from the nitrates, whereas SDC2 powder prepared by modified glycine–nitrate method (GNP) was added into cathode to favor the shrinkage of La 0.8 Sr 0.2 FeO 3− δ (LSF) . Sm-doped ceria solid solution was directly formed during precipitation at 50 °C, and this is ascribed to the role of OH − . The powders calcined at 800 °C for 2 h were still uniform and exhibited an average particle size of 20 nm. The bi-layer with 10 μm dense SDC electrolyte was obtained by co-sintering at 1250 °C for 5 h. A thin and well-adherent anode was formed by depositing ultra-fine NiO–SDC powders, followed by sintering at 1000 °C. The obtained single cells were tested with humidified (3% H 2 O) hydrogen as fuel and the static air as oxidant. The maximum power density reached 67.2 mW/cm 2 at 600 °C.

The SOFC interconnect materials La0.7Ca0.3Cr1−xO3−δ (x = 0–0.09) were prepared using an auto-ignition process and characterized. XRD analysis indicated that all the samples displayed a pure perovskite phase after sintered at 1400 °C for 4 h. The relative density increased from 67% (x = 0) to 95.8% (x = 0.02) and reached to about 97% (x > 0.02), as sintered at 1400 °C for 4 h. The electrical conductivity in air dramatically increased and then lowered slowly with x values. The sample with 0.03 Cr deficiency got a maximum conductivity of 61.7 S cm−1 at 850 °C in air, which is about three times as high as that of the sample with no Cr deficiency (20.6 S cm−1). The sample with 0.06 Cr deficiency exhibited the highest electrical conductivity of 3.9 S cm−1 at 850 °C in pure H2. The thermal expansion coefficient (TEC) were below 11.8 × 10−6 K−1 for samples of x = 0.02–0.09, that was of well compatibility with other components in SOFCs. Results indicate that the materials with 0.02–0.06 Cr deficiency have high properties and are much suitable for SOFC interconnect.

Protonic ceramic membrane fuel cells (PCMFCs) based on proton-conducting electrolytes have attracted much attention because of many advantages, such as low activation energy and high energy efficiency. BaZr0.1Ce0.7Y0.2O3−δ (BZCY7) electrolyte based PCMFCs with stable Ba0.5Sr0.5Zn0.2Fe0.8O3−δ (BSZF) perovskite cathode were investigated. Using thin membrane BZCY7 electrolyte (about 15 μm in thickness) synthesized by a modified Pechini method on NiO-BZCY7 anode support, PCMFCs were assembled and tested by selecting stable BSZF perovskite cathode. An open-circuit potential of 1.015 V, a maximum power density of 486 mW cm−2, and a low polarization resistance of the electrodes of 0.08 Ω cm2 was achieved at 700 °C. The results have indicated that BZCY7 proton-conducting electrolyte with BSZF cathode is a promising material system for the next generation solid oxide fuel cells. Keywords: Solid oxide fuel cells, BaZr0.1Ce0.7Y0.2O3−δ, Ba0.5Sr0.5Zn0.2Fe0.8O3−δ, Protonic ceramic membrane fuel cells, Cathode

A stable, easily sintered perovskite oxide BaCe0.5Zr0.3Y0.16Zn0.04O3-delta (BCZYZn) as an electrolyte for protonic ceramic mernbrane fuel cells (PCMFCs) with Ba0.5Sr0.5Zn0.2Fe0.8O3-delta (BSZF) perovskite cathode was investigated. The BCZYZn perovskite electrolyte synthesized by a modified Pechini method exhibited higher sinterability and reached 97.4% relative density at 1200 degrees C for 5 h in air, which is about 200 degrees C lower than that without Zn dopant. By fabricating thin membrane BCZYZn electrolyte (about 30 mu m in thickness) on NiO-BCZYZn anode support, PCMFCs were assembled and tested by selecting stable BSZF perovskite cathode. An open-circuit potential of 1.00V, a maximum power density of 236 mWcm(-2), and a low polarization resistance of the electrodes of 0.17 Omega cm(2) were achieved at 700 degrees C. This investigation indicated that proton conducting electrolyte BCZYZn with BSZF perovskite cathode is a promising material system for the next generation solid oxide fuel cells. (C) 2008 Elsevier B.V. All rights reserved.

A dense $${\text{BaCe}}_{{\text{0}}{\text{.8}}} {\text{Sm}}_{{\text{0}}{\text{.2}}} {\text{O}}_{{\text{3 - }}\delta } $$ (BCSO) membrane was fabricated by a modified suspension spraying on porous NiO–BCSO anode support. In the process, the suspension was directly prepared by ball-milling the BaCO3, CeO2, and Sm2O3 powders in ethanol. A dense and uniform electrolyte layer in the thickness of 10 μm was successfully prepared on porous anode support by suspension spray process after co-sintering at 1,400 °C for 5 h. With $${\text{Nd}}_{{\text{0}}{\text{.7}}} {\text{Sr}}_{{\text{0}}{\text{.3}}} {\text{MnO}}_{{\text{3 - }}\sigma } $$ (NSMO) cathode, a single cell was assembled and tested with hydrogen and ammonia as fuels, respectively. The hydrogen-fueled cell exhibits 1.01 V for open circuit voltage (OCV) and 560 mW/cm2 for peak power density at 700 °C. In comparison, the cell in ammonia displays a similar performance (1.02 V for OCV and 530 mW/cm2 for output), which indicates the liquid ammonia is a promising substitute for hydrogen. Moreover, the fuel cell displays good interface contacts. To sum up, ammonia-fueled solid oxide fuel cells prepared by this simple suspension spray is an alternative way to promote the commercialization.

Low-cost mullite ceramics were prepared from the mixtures of natural bauxite and industrial waste fly ash. The fired samples, including fly ash, bauxite and their mixture based on the composition of 3:2 mullite, were characterized respectively by XRD (X-ray diffraction). The results indicate that the secondary mullitization occurred by the solid-state reaction of cristobalite and corundum below 1300 °C, followed by the dissolution of corundum into transitory glassy phase at higher temperatures. The dilatometric results reveal that the formation of secondary mullite resulted in a slight expansion in spite of the shrinkage induced by sintering. In addition, the samples were fired at elevated temperatures and then characterized in terms of relative density, porosity, micro-structure and fracture strength. At 1600 °C, the relative density and fracture strength are 93.94% and 186.19 MPa, respectively. Only a small amount of nearly spherical closed pores were observed in the sintered body.

Mullite precursors, waste flyash coated with aluminum hydroxide, were used to prepare low cost porous mullite-based ceramics by reaction sintering. The samples with different alumina contents (0–41.20 wt.%) were sintered at several temperatures from 1000 to 1500 °C. Phase evolution, sintering characteristics and microstructures were investigated in terms of alumina coating content and heat treating temperature. The X-ray diffraction (XRD) results showed, for the 33.30 wt.% alumina coated samples, the mullitization began to occur at 1250 °C via the reaction of α-alumina coating and silica (cristobalite and silica-rich glassy phase) in flyash, and completed at around 1400 °C. With increasing alumina content, both the crystallinity of mullite phase and aspect ratio of mullite crystals were decreased. Our results also demonstrated that the introduction of aluminum hydroxide coating had a positive effect on improving open porosity by inhibiting sintering shrinkage. Compared with flyash, the aluminum hydroxide coated samples showed a more wide sintering temperature range and well-controlled open porosity.

Sm-doped cerium dioxide (SDC) with fcc structure was formed using a gas–liquid chemical co-precipitation process at room temperature. Morphology and structure of the as-prepared samples were characterized using TG, XRD, TEM, HRTEM and SAED techniques. Under our specific experimental conditions, two kinds of 1D nano-structures SDC have been mainly obtained. SDC nanowires are 0.3–1.2 μm in lengths and 5–20 nm in diameters. SDC nanotubes have outer diameters in 10–40 nm with lengths up to 2 μm. The as-prepared SDC shows very strong UV absorption ability and the maximum absorption peak redshifts compared with that of SDC nanoparticles.

A NiO/Yttrium-stabilized zirconia (YSZ) transition layer and/or a SDC function layer were introduced into the anode/electrolyte and/or electrolyte/cathode interface to decrease the activation polarization resulted from the mass transfer at electrode/electrolyte interface. With a NiO/YSZ transition layer, the activation polarization simulated from I–V curves drops from 4.42 to 2.42 Ω cm2 at 600 °C, about 45% less than that of cell I; with additional SDC function layer, no activation polarization is obviously observed. The cell performance was also remarkably improved with the introduction of both the transition layer and the SDC function layer. Peak power densities of 187 and 443 mW cm−2 at 600 and 650 °C, respectively, were achieved for a single cell with both a transition layer and a function layer, with an increment of 87% and 95% compared to that of the cell without any structural improvement, and about 30% and 25% compared to that of the cell with only anode transition layer. The study by ac impedance spectroscopy technique also indicated that the interfacial polarization resistance, the main source of cell resistance, could be effectively reduced by interface improvement.

In order to prepare a dense proton-conductive Ba(Zr0.1Ce0.7)Y0.2O3−δ (BZCY7) electrolyte membrane, a proper anode composition with 65% Ni2O3 in weight ratio was determined after investigating the effects of anode compositions on anode shrinkages for co-sintering. The thermal expansion margins between sintered anodes and electrolytes, which were less than 1% below 750 °C, also showed good thermal expansion compatibility. A suspension spray combined with particle gradation method had been introduced to prepare dense electrolyte membrane on porous anode support. After a heat treatment at 1400 °C for 5 h, a cell with La0.5Sr0.5CoO3−δ (LSCO) cathode was assembled and tested with hydrogen and ammonia as fuels. The outputs reached as high as 330 mW cm−2 in hydrogen and 300 mW cm−2 in ammonia at 700 °C, respectively. Comparing with the interface of another cell prepared by dry-pressing method, this one also showed a good interface contact between electrodes and electrolyte. To sum up, this combined technique can be considered as commercial fabrication technology candidate.

A novel fuel, methylcellulose (MC) was used in the combustion synthesis of Ce 0.8 Sm 0.2 O 1.9 (SDC) powders for the first time. The formation of SDC powders with small crystal size could be attributed to the special performance of MC, which made mixed nitrate entrapped within the cage formed by the cross-linking of MC chains. The precursor solution decomposed violently at about 150 °C confirmed by TG–DTA test. The influence of fuel contents on the powder's properties was investigated by XRD measurements. The experimental cell parameters calculation showed that stoichiometric SDC powders could be obtained only when stoichiometric or fuel-rich MC was used. High sintering activity was favorable for compacted bodies achieving almost near theoretical density. By this combustion synthesis method, SDC powders with high conductivity, which was 0.00765 S cm −1 at 600 °C, was obtained and suitable for the solid oxide fuel cell's applications.

In order to improve the sintering ability of La0.7Ca0.3CrO3−δ (LCC), which has been considered as the interconnect material for SOFC but needs rather high temperature to densification, the ceramic powder with a nominal composition of La0.7Ca0.3Cr0.95Zn0.05O3−δ (LCCZ) was prepared by auto-ignition process. The result was quite positive, that the specimens made by pressing the powder under 360 MPa and sintered at 1200 °C in air for 5 h showed a relative density of 95.2%. The electrical conductivity of LCCZ sintered at 1400 °C for 5 h reached 47.5 S cm−1 in air and 6.15 S cm−1 in hydrogen at 800 °C, which were much higher than the values of LCC. The thermal expansion coefficient of LCCZ was 11.5 × 10−6 K−1, which well matches other components of SOFC.

Anatase TiO 2 powders were calcined with sulfur at 500 °C for 2 h in vacuumized and sealed circumstance. TiO 2 processed with this method has stronger absorbance to visible light than pure TiO 2 . But its absorbance to ultraviolet is weaker comparing to the absorbance of pure TiO 2 . In degradation of methylene blue under visible light (W.L. >430 nm), efficiency of TiO 2 processed in sulfur is obviously higher than that of pure TiO 2 .

In order to develop a simple and cost-effective route to fabricate protonic ceramic membrane fuel cells (PCMFCs) with layered GdBaCo 2 O 5+ x (GBCO) cathode, a dense BaZr 0.1 Ce 0.7 Y 0.2 O 3− δ (BZCY7) electrolyte was fabricated on a porous anode by gel-casting and suspension spray. The porous NiO–BaZr 0.1 Ce 0.7 Y 0.2 O 3− δ (NiO–BZCY7) anode was directly prepared from metal oxide (NiO, BaCO 3 , ZrO 2 , CeO 2 and Y 2 O 3 ) by a simple gel-casting process. A suspension of BaZr 0.1 Ce 0.7 Y 0.2 O 3− δ powders synthesized by gel-casting was then employed to deposit BaZr 0.1 Ce 0.7 Y 0.2 O 3− δ (BZCY7) thin layer by pressurized spray process on NiO–BZCY7 anode. The bi-layer with 10 μm dense BZCY7 electrolyte was obtained by co-sintering at 1400 °C for 5 h. With layered GBCO cathode synthesized by gel-casting on the bi-layer, single cells were assembled and tested with H 2 as fuel and the static air as oxidant. An open-circuit potential of 0.98 V, a maximum power density of 266 mW cm −2 , and a low polarization resistance of the electrodes of 0.16 Ω cm 2 was achieved at 700 °C.

The effect of cobalt oxide addition on the sintering process and electrical performance of BaCe0˙8Gd0˙2O2˙9 (BCGO) ceramics has been evaluated. By adding 1 mol.-% (1CoBCGO) and 2 mol.-% (2CoBCGO) of cobalt, the density of 1CoBCGO and 2CoBCGO samples can reach 91 and 94% respectively, after sintering at 1300°C for 10 h, and the open current voltages (OCV) of H2/air fuel cell with the electrolytes of which were over 0˙95 V at different temperatures. Moreover, there were abnormal OCV decreases for the two samples under 700°C. AC impedance and fuel cell testing showed 1CoBCGO sintered at 1300°C had a higher electrical performance than that of 2CoBCGO, and was very similar to that of BCGO sintered at 1500°C.

To improve cathode–electrolyte interfaces of solid oxide fuel cells (SOFCs), dense YSZ electrolyte membranes with indented surfaces were fabricated on tubular NiO/YSZ anode supports by two comparable methods. Electrochemistry impedance spectroscopy (EIS) and current–voltage tests of the cells were carried out to characterize the cathode–electrolyte interfaces. Results showed that the electrode polarization resistances of the modified cells were reduced by 52% and 35% at 700 °C, and the maximum power densities of cells were remarkably increased, even by 146.6% and 117.8% at lower temperature (700 °C), respectively. The indented surfaces extended the active zone of cathode and enhanced interfacial adhesion, which led to the major improvement in the cell performance.

(Pr–Nd)1−ySryMnO3−δ (P-NSM, y = 0.2, 0.25, 0.3, 0.35) powders made from commercial Pr–Nd mixed oxide, as well as (Pr1−xNdx)0.7Sr0.3MnO3−δ (PN3SM, x = 0, 0.5, 0.7, 1) were synthesized by a glycine-nitrate process and characterized as cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFC). XRD patterns showed the powders had formed pure perovskite phase after being calcined at 800 °C for 2 h. (Pr–Nd)0.7Sr0.3MnO3−δ (P-N3SM) achieved a high conductivity of 194 S cm−1 at 500 °C and showed a good chemical stability against YSZ at 1150 °C. And the thermal expansion coefficient of P-N3SM/YSZ cathode was 11.1 × 10−6 K−1, which well matched YSZ electrolyte film. The tubular SOFC with P-N3SM/YSZ cathode exhibited the maximum power densities of 415, 367, 327 and 282 mW cm−2 at 850, 800, 750 and 700 °C, respectively, which indicated P-N3SM was potentially applied in SOFC for low cost.

A microwave-induced monomer gelation and gel combustion synthesis process was successfully developed to synthesize well-dispersed Pr 0.35 Nd 0.35 Sr 0.3 MnO 3− δ (PNSM)/YSZ composite cathode powders for tubular solid oxide fuel cells (SOFCs). The thermo-gravimetric (TG) analysis of as-prepared ash indicated the decomposition process of most of metal nitrates during gel combustion. The X-ray diffraction (XRD) pattern of the powders calcined at 1000 °C showed only pure PNSM and YSZ phase. Transmission electron microscopy (TEM) revealed that the morphology of powders was characterized with the YSZ particles enwrapped by fine PNSM particles so that PNSM/YSZ composite powders were much better-dispersed compared with the powders made simply by mechanical mixing process. The cell made from PNSM/YSZ composite powder showed lower cathode ohmic resistance and polarization resistance, and produced higher power density subsequently.

Tubular solid oxide fuel cells (SOFCs) with different Pr0.35Nd0.35Sr0.3MnO3/YSZ cathode layers made by slurry spraying, slurry dip-coating and paste brushing were assembled and compared in their performance. In order to improve cathode–electrolyte coherency and interface behavior, dip-coating process was also employed to make the dense electrolyte surface with porous morphology. Electrochemistry impedance spectroscopy (EIS) and current–voltage tests were carried out to characterize the interfaces and the cell performance. Compared with the cell made by normal paste brushing, the cells made by slurry spraying and dip-coating exhibited a decrease of about 50% in electrode polarization resistance and an increase of 67% in the peak power output at 750 °C.

Tubular macro-porous supports for ceramic micro-filtration membranes were prepared by extrusion followed by sintering from low cost commercial grade cordierite powder. The effects of sintering temperature on the micro-structure, fracture strength, LTEC (linear thermal expansion coefficient), pore size distribution and permeation flux were studied. Our results indicate that the optimized sintering temperature was in the vicinity of 1380 °C. The fabricated cordierite supports showed an average pore diameter of 8.66 μm, open porosity of 36.20%, nitrogen gas flux of 1.45 × 104 m3 m−2 h−1 and LTEC of 4.34 × 10−6 °C−1 (between 25 and 1000 °C). To verify the practicability in the strong corrosive environment, the chemical resistance tests were carried out in the sodium hydroxide and sulfuric acid solutions under the boiling condition, respectively. Compared with the as-used alumina supports, the cordierite supports exhibited better thermal alkali resistance but poorer acid resistance according to the mass loss results. In addition, the corroded cordierite supports were characterized by fracture strength, open porosity and pore size distribution. The fabricated macro-porous supports are expected to have potential applications in the pre-treatment of strong alkali media and dust-containing hot gas.

A nickel-based anode-supported solid oxide fuel cell (SOFC) was assembled with a 10 μm thick Ce0.8Sm0.2O2−δ (SDC) electrolyte and a Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) cathode. The cell performance was investigated with hydrogen and ammonia gas evaporated from liquefied ammonia as fuel. Fueled by hydrogen the maximum power densities were 1872, 1357, and 748 mW cm−2 at 650, 600, and 550 °C, respectively. While with ammonia as fuel, the cell showed the maximum power densities of 1190, 434, and 167 mW cm−2, correspondingly. The power densities lower than that predicted, particularly at the lower operating temperatures for ammonia fuel cell, compared to hydrogen fuel cell, could be attributed to actual lower temperature than thermocouple display due to endothermic reaction of ammonia decomposition as well as the rather larger inlet ammonia flow rate. The results demonstrated that the ammonia was a right convenient liquid fuel for SOFCs as long as it was keeping the decomposition completion of ammonia in the cell or before entering the cell.

An overall comparative study was carried out on Li-doped, F-doped, and Li–F-codoped TiO 2 powders in order to elucidate the roles of Li + and F − ions in photocatalyst. The characteristic data were based on the analysis of XRD, XPS, and PL spectra. The effects of atomic ratio of Li/Ti and F/Ti on the photocatalytic activity were also investigated. As the results, Li doping accelerated the phase formation of rutile in lower temperature while F doping prevented the phase transition from anatase to rutile. Li doping inducted a large amount of O OH on the surface of TiO 2 , while F doping consumed much of O OH . Li + ions acted as the roles of recombination center of electron–hole pairs while F doping could restrain the recombination of electron–hole pairs on the center of Li + ions. The roles of Li + and F − ions were also confirmed in the experimental section, where the photocatalytic activity of TiO 2 was improved greatly by synergistic reaction of Li + and F − ions.