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1.
Y2O3-stabilized ZrO2 (YSZ) and Gd-doped CeO2 (GDC) oxide impregnated Ni was investigated and developed as anodes of solid oxide fuel cells. Performance of the Ni anodes for the H2 oxidation reaction was substantially enhanced after the impregnation of submicrometer (100–300 nm) YSZ and GDC oxide particles. After impregnation of 1.7 mg/cm2 GDC (∼8.5 vol% GDC), the electrode polarization resistance dropped to 0.71 Ω·cm2 at 800°C, close to 0.24 Ω·cm2 reported on good Ni (50 vol%)/YSZ (50 vol%) cermet anodes at the same temperature. The results demonstrated that ion or wet impregnation is an effective process to introduce ionic conducting and catalytic active nano-sized YSZ and GDC phases into stable and porous Ni electronic network structure without the high temperature sintering process.  相似文献   

2.
A thin film (60 μm thick) of a gadolinium-doped ceria (GDC) electrolyte was prepared by the doctor blade method. This film was laminated with freeze-dried 42 vol% NiO–58 vol% GDC mixed powder and pressed uniaxially or isostatically under a pressure of 294 MPa. This laminate was cosintered at 1100 °–1500 °C in air for 4–12 h. The laminate warped because of the difference in the shrinkage of the electrolyte and electrode during the sintering. A higher shrinkage was measured for the electrode at 1100 °–1200 °C and for the electrolyte at 1300 °–1500 °C. The increase of the thickness of anode was effective in decreasing the warp and in increasing the density of the laminated composite. The maximum electric power density with a SrRuO3 cathode using 3 vol% H2O-containing H2 fuel was 100 mW/cm2 at 600 °C and 380 mW/cm2 at 800 °C, respectively, for the anode-supported GDC electrolyte with 30 μm thickness.  相似文献   

3.
A centrifugal casting technique was developed for depositing thin 8-mol%-yttrium-stabilized zirconia (YSZ) electrolyte layers on porous NiO-YSZ anode substrates. After the bilayers were cosintered at 1400°C, dense pinhole-free YSZ coatings with thicknesses of ∼25 μm were obtained, while the Ni-YSZ retained porosity. After La0.6Sr0.4Co0.2Fe0.8O3 (LSCF)-Ce0.9Gd0.1O1.95 (GDC) or La0.8Sr0.2MnO3 (LSM)-YSZ cathodes were deposited, single SOFCs produced near-theoretical open-circuit voltages and power densities of ∼1 W/cm2 at 800°C. Impedance spectra measured during cell tests showed that polarization resistances accounted for ∼70%–80% of the total cell resistance.  相似文献   

4.
Nanostructured La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) oxide powder was synthesized by a facile autocombustion process based on a modified glycine-nitrate process (GNP) using cellulose fiber as micro-reactor. As compared with the normal GNP, this novel process allows the combustion to proceed in a much more environmentally friendly and controllable way. The resulted powder is nanocrystallized with particle size of only 15–20 nm as observed by transmission electron microscopy examination. More importantly, because the metal ions could disperse homogenously in cellulose–GN precursor, SrCO3 impurity was effectively suppressed. The concentrations of SrCO3 impurity in LSCF products were determined by carbon dioxide–temperature-programmed desorption technique, which decreased to as low as 1.3 wt% from cellulose–GN process, in contrast to 4.3 wt% from the normal GNP. These features resulted in the attractive improvement of its cathode performance in solid-oxide fuel cells (SOFCs). The interfacial resistances of only ∼0.70 and ∼0.36 Ω·cm2 at 600° and 650°C under air, respectively, were observed, which was about two times better than the LSCF cathode derived from the normal GNP. A peak power density of ∼346 mW/cm2 was achieved at 600°C with cellulose–GN-derived LSCF cathode based on thin-film Sm0.2Ce0.8O1.9 electrolyte SOFC using 3% humidified H2 as the fuel.  相似文献   

5.
Porous Y2O3-stabilized ZrO2 (YSZ) samples were synthesized by preparing NiO/YSZ composites by tape casting and calcining at 1800 K, reducing the NiO to nickel in H2 at 973 K, and finally leaching the nickel out of the structure with 2.2 M HNO3 at 353 K. Porous YSZ was prepared from NiO/YSZ composites containing 0, 20, 40, and 50 wt% NiO. Complete removal of the nickel was demonstrated by XRD, weight changes, and porosity increases. Porosities >75% could be achieved without structural collapse of the YSZ phase. Finally, the method was applied to the fabrication of a solid oxide fuel cell with a copper-based anode operating on H2 and n -butane.  相似文献   

6.
(La0.8Sr0.2)0.98Fe0.98Cu0.02O3−δ can be sintered directly onto YSZ (without the need for a protective ceria interlayer). Though subject to an extended "burn-in" period (∼200 h), anode-supported YSZ cells using the Cu-doped LSF achieve power densities ranging from 1.3 to 1.7 W/cm2 at 750°C and 0.7 V. These cells have also demonstrated 500 h of stable performance. The results are somewhat surprising given that XRD indicates an interaction between (La0.8Sr0.2)0.98Fe0.98-Cu0.02O3−δ and YSZ resulting in the formation of strontium zirconate and/or monoclinic zirconia. The amount and type of reaction product was found to be dependent on cathode and electrolyte powder precalcination temperatures.  相似文献   

7.
A solid electrolyte electrochemical cell of the type Pt|Ni:NiO a =1∥ZrO2+7.5% CaO∥Ni:NiO a <1+glass|Pt was used to measure the activities of NiO in sodium disilicate glass from 750° to 1100°C. The data indicate a solubility varying from 11 mol% (5.0 wt%) at 800° to 20 mol% (9.3 wt%) at 1100°C. From the variation in NiO activity, the activity of sodium disilicate in glass solution was estimated; from these combined data partial molar free energies and entropies of solution of NiO and Na2Si2O5 and free energies and entropies of mixing were calculated. A partial phase diagram for the system NiO-Na2Si2O5 proposed from solubility data indicates a eutectic at ∼12 mol% (5.3 wt%) NiO at 830°C.  相似文献   

8.
Cone-shaped Sm-doped CeO2 (Ce0.8Sm0.2O1.9, SDC) electrolyte cylinders have been fabricated using the slip-casting technique. A single solid oxide fuel cell has been prepared by applying a Sm0.5Sr0.5CoO3 cathode on the outside of the cylinders and a NiO–SDC (7:3 wt%) anode on the inside. The open circuit voltage of the cell was 0.93 V at 400°C, and a maximum power density of about 300 mW/cm2 at 700°C was obtained with humidified hydrogen (3% H2O) as the fuel and ambient air as the oxidant. Impedance results showed that the performance of the cell was mainly influenced by the ohmic resistance of the electrolyte.  相似文献   

9.
The sintering behavior and electrical conductivity of high-purity 8-mol% Y2O3-stabilized ZrO2 (8YSZ) with Al2O3 additions were investigated. The addition of 1 wt% AI2O3 to 8YSZ provided dense, sintered samples with 9.1% relative density at 1400°C without a holding time. Addition of 1 wt% SiO2 enhanced the sinterability of 8YSZ. Na2O addition of 0.1 wt% remarkably lowered it. Electrical conductivity at 1000°C in air increased slightly with increased Ai2O3 content up to 1 wt% and then monotonously decreased. 8YSZ with 1 wt% AI2O3 showed the maximum conductivity of 0.16 S/cm at 1000°C.  相似文献   

10.
Sample disks prepared from Al2O3 (61 wt%), SiO2 (28 wt%), and Fe2O3(II wt%) powders were sintered at 1270° and 1440°C and then annealed between 1300° and 1670°C. The annealed samples consisted of mullite as the main compound with minor amounts of glass and sometimes magnetite. The iron content of the mullites decreases strongly from ∼ 10.5 wt% Fe2O3 at 1300°C to ∼ 2.5 wt% Fe2O3 at 1670°C. A complex temperature-controlled exsolution mechanism of iron from mullite is considered.  相似文献   

11.
SiO2-Al2O3 melts containing 42 and 60 wt% A12O3 were homogenized at 2090°C (∼10°) and crystallized by various heat treatment schedules in sealed molybdenum crucibles. Mullite containing ∼78 wt% A12O3 precipitated from the 60 wt% A12O3 melts at ∼1325°± 20°C, which is the boundary of a previously calculated liquid miscibility gap. When the homogenized melts were heat-treated within this gap, the A12O3 in the mullite decreased with a corresponding increase in the Al2O3 content of the glass. A similar decrease of Al2O3 in mullite was observed when crystallized melts were reheated at 1725°± 10°C; the lowest A12O3 content (∼73.5 wt%) was in melts that were reheated for 110 h. All melts indicated that the composition of the precipitating mullite was sensitive to the heat treatment of the melts.  相似文献   

12.
A colloidal deposition without any binder was developed to prepare a dense La0.8Sr0.2Ga0.85Mg0.15O3−δ (LSGM) film on porous NiO/YSZ substrates, using an incompletely crystallized LSGM powder as starting material. Both the dense LSGM film with a thickness of 15 μm and the required phase composition of the LSGM were achieved simultaneously by sintering at 1400°C for 6 h. The conductivity of the supported LSGM film attained 0.102 S/cm at 800°C, which was comparable with those of the self-supported LSGM films. The maximum power density of the LSGM film cell was 480 at 800°C and 614 mW/cm2 at 850°C, respectively.  相似文献   

13.
A simple and elegant approach to fabrication of dense ceramic membranes on porous substrates, a traditional dry pressing of foam powders, has been developed to reduce the cost of fabrication. Gd-doped ceria (GDC, Gd0.1Ce0.9O1.95) electrolyte membranes as thin as 8 μm are obtained by dry-pressing highly porous GDC powders. The membrane thickness can be readily controlled by the amount of powder. The electrolyte membranes are studied in a solid-oxide fuel cell (SOFC) with air as oxidant and humidified hydrogen (3% H2O) as fuel. Open-circuit voltages of about 1.0 V are observed, implying that the permeability of the membranes to molecular gases is insignificant. Power densities of 140 and 380 mW/cm2 are demonstrated at 500° and 600°C, respectively, representing a significant progress in developing low-temperature SOFCs.  相似文献   

14.
Gas-tight Y2O3-stabilized ZrO2 (YSZ) films were prepared on NiO–YSZ and NiO–SDC (Sm0.2Ce0.8O1.9) anode substrates by a novel method. A cell, Ni–YSZ/YSZ(10 μm)/LSM–YSZ, was tested with humidified hydrogen as fuel and ambient air as oxidant. The maximum power densities of 1.64, 1.40, 1.06, and 0.60 W/cm2 were obtained at 850°, 800°, 750°, and 700°C, respectively. With methane as fuel, a cell of Ni–SDC/YSZ (12 μm)/LSM–YSZ exhibited the maximum power densities of 1.14, 0.82, 0.49, and 0.28 W/cm2 at 850°, 800°, 750°, and 700°C, respectively. The impedance results showed that the performance of the cell was controlled by the electrode polarization rather than the resistance of YSZ electrolyte film.  相似文献   

15.
Cation-doped CeO2 electrolyte has been evaluated in single-cell and short-stack tests in solid oxide fuel cell environments and applications. These results, along with conductivity measurements, indicate that an ionic transference number of ∼0.75 can be expected at 800°C. Single cells have shown a power density >350 mW/cm2. Multicell stacks have demonstrated a peak performance of >100 mW/cm2 at 700°C using metallic separators.  相似文献   

16.
Subsolidus phase relations in the low-Y2O3 portion of the system ZrO2-Y2O3 were studied using DTA with fired samples and X-ray phase identification and lattice parameter techniques with quenched samples. Approximately 1.5% Y2O3 is soluble in monoclinic ZrO2, a two-phase monoclinic solid solution plus cubic solid solution region exists to ∼7.5% Y2O3 below ∼500°C, and a two-phase tetragonal solid solution plus cubic solid solution exists from ∼1.5 to 7.5% Y2O3 from ∼500° to ∼1600°C. At higher Y2O3 compositions, cubic ZrO2 solid solution occurs.  相似文献   

17.
The performance of La0.8Sr0.2Ga0.83Mg0.17O2.815 (LSGM) as an optimized electrolyte of a solid oxide fuel cell was tested on single cells having a 500-µm-thick electrolyte membrane. The reactivity of NiO and LSGM suggested use of an interlayer to prevent formation of LaNiO3. The interlayer Sm-CeO2 was selected and sandwiched between the electrolyte and anode. Comparison of Sm-CeO2/Sm-CeO2+ Ni and Sm-CeO2+ Ni as anodes showed that Sm-CeO2/Sm-CeO2+ Ni gave an exchange current density 4 times higher than that of Sm-CeO2+ Ni. The peak power density of the interlayered cell is 100 mW higher than that of the standard cell without the interlayer. This improvement is due to a significant reduction of the anode overpotential; the overpotential of the cathode La0.6Sr0.4CoO3-delta (LSCo) remained unchanged. Comparison of the peak power density in this study and with that of a previous study, also with a 500-µm-thick electrolyte, indicates a factor of 2 improvement, i.e., from 270 mW/cm2 to 550 mW/cm2 at 800°C. The excellent cell performance showed that an LSGM-based thick membrane SOFC operating at temperatures 600° < T op < 800°C is a realistic goal.  相似文献   

18.
SrCe0.9Eu0.1O3−δ thin-film (∼30 μm) tubular hydrogen separation membranes were developed in order to obtain high hydrogen fluxes. Fifteen centimeters long, one end closed, NiO–SrCeO3 tubular supports were fabricated by tape casting, followed by rolling the green tape on a circular rod. SrCe0.9Eu0.1O3−δ powders were prepared by the citrate process and coated on partially sintered NiO–SrCeO3 tubular supports. Leakage-free hydrogen membrane cells were obtained by adjusting the presintering and final sintering temperatures to reduce the difference of linear shrinkage rates between SrCe0.9Eu0.1O3−δ thin films and NiO–SrCeO3 supports. A hydrogen flux of 2.2 cm3/min was obtained for the SrCe0.9Eu0.1O3−δ on Ni–SrCeO3 tubular hydrogen separation membranes at 900°C using 25% H2 balanced with Ar and 3% H2O as the feed gas and He as the sweep gas. Thus, a 40% single pass yield of pure H2 was achieved with this membrane.  相似文献   

19.
The subsolidus phase relations in the entire system ZrO2-Y2O3 were established using DTA, expansion measurements, and room- and high-temperature X-ray diffraction. Three eutectoid reactions were found in the system: ( a ) tetragonal zirconia solid solution→monoclinic zirconia solid solution+cubic zirconia solid solution at 4.5 mol% Y2O3 and ∼490°C, ( b ) cubic zirconia solid solutiow→δ-phase Y4Zr3O12+hexagonalphase Y6ZrO11 at 45 mol% Y2O3 and ∼1325°±25°C, and ( c ) yttria C -type solid solution→wcubic zirconia solid solution+ hexagonal phase Y6ZrO11 at ∼72 mol% Y2O3 and 1650°±50°C. Two ordered phases were also found in the system, one at 40 mol% Y2O3 with ideal formula Y4Zr3O12, and another, a new hexagonal phase, at 75 mol% Y2O3 with formula Y6ZrO11. They decompose at 1375° and >1750°C into cubic zirconia solid solution and yttria C -type solid solution, respectively. The extent of the cubic zirconia and yttria C -type solid solution fields was also redetermined. By incorporating the known tetragonal-cubic zirconia transition temperature and the liquidus temperatures in the system, a new tentative phase diagram is given for the system ZrO2-Y2O3.  相似文献   

20.
Interpenetrating phase composite (IPC) coatings consisting of continuously connected Al2O3 and epoxy phases were fabricated. The ceramic phase was prepared by depositing an aqueous dispersion of Al2O3 (0.3 μm) containing orthophosphoric acid, H3PO4, (1–9.6 wt%, solid basis) and heating to create phosphate bonds between particles. The resulting ceramic coating was porous, which allowed the infiltration and curing of a second-phase epoxy resin. The effect of dispersion composition and thermal processing conditions on the phosphate bonding and ceramic microstructure was investigated. Reaction between Al2O3 and H3PO4 generated an aluminum phosphate layer on particle surfaces and between particles; this bonding phase was initially amorphous, but partially crystallized upon heating to 500°C. Flexural modulus measurements verified the formation of bonds between particles. The coating porosity (and hence epoxy content in the final IPC coating) decreased from ∼50% to 30% with increased H3PO4 loading. The addition of aluminum chloride, AlCl3, enhanced bonding at low temperatures but did not change the porosity. Diffuse reflectance FTIR showed that a combination of UV and thermal curing steps was necessary for complete curing of the infiltrated epoxy phase. Al2O3/epoxy IPC coatings prepared by this method can range in thickness from 1 to 100 μm and have potential applications in wear resistance.  相似文献   

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