•Co-infiltration of ZrO2 and PdO increased the thermal stability of PdO particles.•Performance of LSM-YSZ cathode was greatly improved by the PdO/ZrO2 co-infiltration.•The growth of PdO showed a self-limited kinetics model with relaxation time.•Stable and high performance of PdO/ZrO2-infiltrated LSM-YSZ cathode was obtained.To enhance the electrochemical performance of (La0.8Sr0.2)0.95MnO3-δ-8 mol. % Y2O3 stabilized ZrO2 (LSM-YSZ) cathode at reduced temperatures, PdO and ZrO2 (Pd/Zr = 0.8/0.2) are co-infiltrated into the LSM-YSZ scaffold. Such prepared composite cathode is investigated at temperatures between 600 and 750 °C and cathodic current densities of 400 and 800 mA cm−2. It is observed that PdO particles are uniformly deposited on the surface of the LSM-YSZ and surrounded by nano-sized ZrO2 particles. This distinctive microstructure possesses improved thermal stability under current at 750 °C due to the hindering effect of ZrO2 on the agglomeration and growth of PdO particles. As a result, the electrocatalytic activity of the cathode for oxygen reduction reaction (ORR) is greatly enhanced due to presence of the self-limited PdO particles. At open circuit voltage, the initial polarization resistance decreases from 1.68 to 0.40 Ω cm2 as temperature increases from 600 to 750 °C; and the polarization resistance is fully stabilized at the level of 0.36 and 0.34 Ω cm2, respectively, after current polarization at 750 °C under 400 and 800 mA cm−2 for less than 200 h.

Conventional anode materials for solid oxide fuel cells (SOFCs) are Ni-based cermets, which are highly susceptible to deactivation by contaminants in hydrocarbon fuels. Hydrogen sulfide is one of the commonly existed contaminants in readily available natural gas and gasification product gases of pyrolysis of biomasses. Development of sulfur tolerant anode materials is thus one of the critical challenges for commercial viability and practical application of SOFC technologies. Here we report a viable approach to enhance substantially the sulfur poisoning resistance of a Ni-gadolinia-doped ceria (Ni-GDC) anode through impregnation of proton conducting perovskite BaCe0.9Yb0.1O3−δ (BCYb). The impregnation of BCYb nanoparticles improves the electrochemical performance of the Ni-GDC anode in both H2 and H2S containing fuels. Moreover, more importantly, the enhanced stability is observed in 500 ppm of H2S/H2. The SEM and XPS analysis indicate that the infiltrated BCYb fine particles inhibit the adsorption of sulfur and facilitate sulfur removal from active sites, thus preventing the detrimental interaction between sulfur and Ni-GDC and the formation of cerium sulfide. The preliminary results of the cell with the BCYb+Ni-GDC anode in methane fuel containing 5000 ppm of H2S show the promising potential of the BCYb infiltration approach in the development of highly active and stable Ni-GDC-based anodes fed with hydrocarbon fuels containing a high concentration of sulfur compounds.Keywords: impregnation; Ni-GDC anode; solid oxide fuel cells; sulfur tolerance; ytterbium-doped barium cerate

•The NCF-BZCYYb possesses higher activity for CH4 steam reforming compared to Ni-YSZ.•The use of NCF-BZCYYb catalyst in the Ni-YSZ supported SOFC is studied.•NCF-BZCYYb coated single cell exhibits higher electrochemical performance in CH4.•NCF-BZCYYb coated single cell exhibits better durability and carbon resistance.Two types of anode-supported cell are fabricated by tape casting, screen printing and sintering processes. The first one is a conventional anode supported cell (ASC); and the other, namely CASC, contains an extra layer of Ni-Cu/Ni-Fe alloys-BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (NCF-BZCYYb) cermet catalyst on the surface of the anode-support. Using CH4-3 mol. % H2O as the fuel, the initial performance of the CASC is moderately improved, compared with that of the ASC; the power density of the CASC and ASC at 500 mA cm−2 and 800 °C remain stable on the level of 470 mW cm−2 for approximately 11 and 0.8 h, respectively, before cell disintegration caused by carbon formation. The performances of the CASC in the fuel of CH4-33.3 mol. % H2O are significantly increased above the level of the ASC, demonstrating an initial peak power density ranging from 280 to 1638 mW cm−2 at temperatures between 600 and 800 °C and a stable power density of 485 mW cm−2 at 500 mA cm−2 and 800 °C for 48 h. Carbon deposition in the anode region of the tested CASC cell is not detected, as the NCF-BZCYYb is a more active catalyst than the Ni-Zr0.92Y0.08O2-δ (YSZ) anode-support for CH4 steam reforming.Download high-res image (457KB)Download full-size image

•Sb anode chemical-looping carbon-air fuel cell achieved reasonable performance.•Bio-char fueled carbon-air fuel cell achieved an electrical efficiency of 30.8%.•Molar ratio of CO/CO2 in exhaust gas increased with working temperature.•Energy conversion efficiency increased to 41.8% by series power generation.To take the advantage chemical-looping combustion (CLC) process for CO2 sequestration, carbon-air fuel cell (CAFC) and conventional solid oxide fuel cell (SOFC) are prepared for high-efficiency series power generation. The tubular CAFC (Cell-I) consisting of Sb anode, (Y2O3)0.08(ZrO2)0.92 (YSZ) electrolyte and La0.6Sr0.4Co0.2Fe0.8O3-δ-Gd0.1Ce0.9O3-δ (LSCF-GDC) cathode has achieved peak power densities of 117, 186 and 295 mW cm−2 at 700, 750 and 800 °C, respectively. Fueled by repeatedly added 3 g of coconut-derived activated charcoal, Cell-I has operated stably at 800 °C for 21 h under the condition of 0.4 A cm−2 and 0.502 V, with an electrical efficiency of 30.8%. The tubular conventional SOFC (Cell-II) is designed with Ni-YSZ as anode, YSZ electrolyte as electrolyte and (La0.8Sr0.2)0.95MnO3-δ-YSZ (LSM-YSZ) as cathode. The anode exhaust gas of Cell-I, which is operated at temperatures from 750 to 850 °C, contains CO and CO2. Using this exhaust gas as fuel, Cell-II has demonstrated peak power densities between 87 and 133 mW cm−2 at 750 °C, and performed stably for 6 h at 0.1 A cm−2 and 0.720 V during which 69.6% of CO in the exhaust gas is consumed. Cell-II has achieved an extra electrical efficiency of 11.0%, giving a total electrical efficiency of 41.8% for the series power generation.

Conventional Ni-based cermet anodes such as Ni-gadolinia doped ceria (Ni-GDC) suffer from low carbon deposition resistance in direct methane solid oxide fuel cells (SOFCs). Here we show that impregnating proton conducting perovskites like BaCe0.9Y0.1O3−δ (BCY) and BaCe0.9Yb0.1O3−δ (BCYb) in Ni-GDC not only improves the initial polarization performance but also, most importantly, significantly enhances the stability in wet methane fuel (3% H2O in CH4) by inhibiting carbon deposition and formation. In wet methane, the voltage of the cell with the conventional Ni-GDC anode decreases rapidly from 0.58 to 0.15 V within 6 h at 200 mA cm−2 and 750 °C. In contrast, in the case of the cells with BCY + Ni-GDC and BCYb + Ni-GDC anodes, the cell voltage is essentially constant at 0.62–0.65 V over a period of 48 h tested under identical conditions. The microstructure and Raman spectroscopy analysis reveal that the impregnated fine BCY and BCYb particles are preferentially distributed on the surface of the Ni grains in the Ni-GDC anode, decreasing the exposed surface of Ni grains and inhibiting carbon deposition. Also, the proton conducting and fine BCY and BCYb particles can adsorb and decompose water, which in turn reacts with deposited carbon to form CO and H2, alleviating the carbon deposition problem in the anode and thus significantly improving the cell stability of direct methane SOFCs.

•SSM show better electrochemical performance than LSM82.•SSM55 possesses high surface Mn4+/Mn3+ and Oad/Olattice concentration ratios.•The surface oxygen exchange kinetics for SSM are faster than LSM82.SmxSr1−xMnO3 with x = 0.3, 0.5 and 0.8, denoted as SSM37, SSM55 and SSM82, respectively, have been prepared via a sol–gel route as materials for cathodes in solid oxide fuel cells. Their activities in the oxygen reduction reaction (ORR) have been evaluated in comparison with the state-of-the-art cathode material La0.8Sr0.2MnO3 (LSM82) by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and thermogravimetry (TG). Among all the prepared cathodes, the SSM55 exhibits the lowest values, while the LSM82 exhibits the highest polarization resistance, at open circuit voltage (OCV) and temperatures from 650 to 800 °C. This result indicates that the prepared SmxSr1−xMnO3 is a promising replacement for LSM82 as cathode material for SOFCs, and the SSM55 represents the optimal concentration in SmxSr1−xMnO3 series. The remarkably high ORR activity of the SSM55 is ascribed to its high surface Mn4+/Mn3+ and Oad/Olattice ratios and fast surface oxygen exchange kinetics.

•Metal support SOFC was prepared by tape casting-screen printing-sintering process.•Ni0.9Fe0.1 anode-support is more active for CH4 reforming than its Ni counterpart.•There is no significant degradation within 50 h durability test with CH4 fuel.Ni0.9Fe0.1-supported solid oxide fuel cells are fabricated by tape casting-screen printing-sintering process; and the activity for CH4 reforming and electrochemical performance are examined with wet (3 vol.% H2O) CH4 as the fuel at 650 °C, in comparison with Ni-supported cells. At a flow rate of 100 ml min−1, the wet CH4 is partially (35 vol.%) reformed to H2, CO and CO2 in the Ni0.9Fe0.1 anode-support, demonstrating a higher reforming activity than that of the Ni anode-support. The maximum power density is 1.01 Wcm−2 at a high limiting current density of 2.6 A cm−2; and cell voltage at 0.4 A cm−2 is slightly decreased from 0.65 to 0.60 V within 50 h durability test. This high performance is attributed to the Ni0.9Fe0.1 anode-support that is more active for CH4 reforming and resistant to carbon deposition than its Ni counterpart.

•LaNbO4–NiO–YSZ composites prepared with LaNbO4 contents between 5 and 30 wt.%.•The thermal expansion coefficients of the composites were investigated.•Flexural strength and fracture toughness of the composites were examined.LaNbO4–NiO–Y2O3 stabilized ZrO2 (YSZ) composites are prepared and investigated as an anode-support material for solid oxide fuel cells. To tailor the coefficient of thermal expansion (CTE), electrical conductivity, fracture strength σ and fracture toughness KIC of the composite, various amounts of LaNbO4 from 0 to 30 wt.% are added into 53 wt.% NiO–47 wt.% YSZ composite. With LaNbO4 addition into the NiO–YSZ, σ changes insignificantly, whereas CTE decreases and KIC increases monotonously. For 30 wt.% LaNbO4–NiO–YSZ, the CTE is 12.4 × 10−6 K−1 (250–1000 °C), which is much closer to that of YSZ, and the KIC is 3.1 MPa-m1/2, which is 42% increase compared with that of the NiO–YSZ. The increase in fracture toughness is possibly due to the domain switch within LaNbO4 and the overall grain refinement of the composite. The electrical conductivity of the reduced composites decreases with increasing the amount of LaNbO4 and shows metallic conducting behavior with temperature.

Surface reactions of O2 molecules on a Sr-doped LaMnO3 (LSM) cathode and Pd impregnated LSM cathode are investigated by the first principles method. A tetrahedral Pd4 cluster is used to simulate the Pd particles on the LSM surface. The calculated adsorption energies demonstrate that the pre-adsorbed Pd facilitates O2 adsorption on the surface. The bond length of adsorbed O2 species and corresponding dissociation energies indicate that O2 molecules on the Pd/LSM cathode surface can be dissociated more easily than on the pure LSM surface. The pre-adsorbed Pd (atom and cluster) can serve as an active center on the surface and enhance the electron transference properties during the oxygen reduction reactions.

The microstructure evolution and phase transformation of high strength 22SiMn2TiB steel during non-isothermal deformation were investigated by using in situ time-of-flight (TOF) neutron diffraction technique. The results indicate that the deformation of austenite promotes pearlite and ferrite transformation while suppresses bainite transformation. Deformation texture forms in austenite and then it influences the evolution of transformation texture. Deformation of austenite brings the changes in lattice parameters of austenite caused by carbon partitioning and elastic strains during the transformation. Volume fraction of the retained austenite decreases with a decreased carbon content as deformation amount increases.

A novel anode with a Ni0.5Cu0.5Fe2O4 (NCFO)–BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) composite on NiO–Y2O3 stabilized ZrO2 (YSZ) is fabricated and investigated in dry and wet (3 mol% H2O) CH4 at temperatures ranging from 650 to 800 °C. For comparison, a conventional NiO–YSZ anode is also prepared. In H2–3 mol% H2O at 600 °C for 2 h, NCFO and NiO are fully reduced to Ni–Cu–Fe alloys (NCF) and Ni, respectively, forming bi-layer NCF–BZCYYb/Ni–YSZ (BL) and single-layer Ni–YSZ (SL) anodes. The polarization resistance of the BL anode in dry and wet CH4 is only approximately 1/5 of that of the SL anode due to the enhancement of NCF–BZCYYb on CH4 oxidation. This improvement is also supported by the results from DC polarization. Carbon deposition is inhibited in the BL anode by adding only 3 mol% H2O into dry CH4 and the carbon formed in dry CH4 can be removed by subsequent exposure of the BL anode to wet CH4. The overall electrochemical performance of the BL anode is significantly stable in wet CH4, which suggests that it is promising for applications in direct CH4 solid oxide fuel cells (SOFCs).

•SSM50 has better oxygen storage capacity than LSM50.•The absorbed O2 species on SSM50 (100) surface are readily dissociated.•SSM50 has the best catalysis for the ORR among the considered systems.Cubic perovskite SmxSr1−xMnO3 (SSM) surface and bulk models have been constructed to simulate the oxygen reduction reactions by employing first-principles calculations. The results demonstrate that oxygen vacancies can be formed easily in Sm0.5Sr0.5MnO3 (SSM50). The oxygen migration barrier in bulk SSM50, which is predicted by the nudged elastic band (NEB) method, is the lowest, while the adsorption energy of O2 molecular on SSM50 (100) surface is the lowest among the considered doping systems, indicating the potential application of SSM50 as a cathode for intermediate-temperature solid oxide fuel cell (IT-SOFC). The reaction mechanisms of oxygen reduction on SSM50 (100) surface have also been studied.

•Optimization of the half cell performance by the LSCF loadings and LSCF particle morphology.•Novel surfactant was introduced in the precursor solution.•N-ethyl-perfluoyooctylsulfonamide had a great effect on the performance of LSCF-YSZ cathodes.The electrocatalytic performance of the oxygen-reduction reaction of La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)–Y2O3 stabilized ZrO2 (YSZ) cathodes prepared by an impregnation technique has been investigated as cathodes for intermediate temperature solid oxide fuel cells. The electrocatalytic activity of LSCF-YSZ cathodes increases with the introduction of LSCF phases to the YSZ scaffold. The introduction of surfactants into LSCF-precursor solutions during preparation has a great effect on the microstructure and electrochemical performance of LSCF-YSZ composite cathodes. N-ethyl-perfluoyooctylsulfonamide (DF10) is a type of commonly used nonionic flusurfactant which affects the LSCF particles' morphology on the YSZ scaffold. Using N-ethyl-perfluoyooctylsulfonamide (DF10) + acetylacetone during the preparation of LSCF-YSZ composite cathodes decreases the electrode polarization resistance (Re) of cathodes from 0.45 to 0.18 Ω cm2. We obtained a notable improvement in the electrochemical performance of LSCF-YSZ-composite cathodes with uniform and continuous LSCF particle distribution on the surface of YSZ scaffold.

•BZCYYb perovskite is evaluated as a potential anode material for the first time.•Excellent performance of BZCYYb anode is obtained both in H2 and CH4 atmosphere.•BZCYYb anode exhibits superb carbon resistance in the absence of excess steam.BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) perovskite is synthesized and examined as an alternative anode material for intermediate temperature solid oxide fuel cells (IT-SOFCs) based on direct hydrocarbon fuels, using polarization and electrochemical impedance spectroscopy techniques. Single-phased BZCYYb anode shows an excellent activity for both hydrogen and methane oxidation reactions, achieving a polarization resistance of 0.25 and 0.93 Ω cm2, and overpotential of 20 and 202 mV at 100 mA cm−2 and 750 °C in wet H2 (3% H2O/97% H2) and wet CH4 (3% H2O/97% CH4), respectively. The electrocatalytic activity of BZCYYb anodes is significantly higher than that of the (La,Sr)(Cr,Mn)O3 anodes as reported in the literature. Furthermore, BZCYYb exhibits excellent resistance to carbon deposition. The present study demonstrates that BZCYYb perovskite is a promising alternative anode material for direct hydrocarbon fuels based SOFCs.

The morphology of domain structure in LaNbO4 added to YSZ–NiO composite was examined using a focused ion beam prepared specimen in a transmission electron microscope with a straining stage. It is confirmed for the first time that the morphology is changed under load through domain boundary movement. The driving force for this domain switch is the difference in Gibbs free energy between domains with different crystallographic orientations. This domain switch improves toughness by dissipating stress build-up at the crack tips.

Al2O3–glass composite seals are fabricated by tape casting Al2O3 and HGS glass powder mixtures with glass contents ranging from 20 to 60 wt%. Their leaking performance is evaluated for various temperatures, gas pressures and compressive loads. The seal with optimized glass content is subjected to thermal cycling and single-cell tests to investigate the viability of the seal. The sealing performance of the seal is significantly improved by increasing the glass content in the composite seal; the seal containing 50 wt% glass (AG50) shows the best sealing performance among the studied compositions. Increasing the testing gas pressure or decreasing the testing temperature and compressive load increase the leak rate of the seal. After 25 thermal cycles between 750 and 200 °C, the leak rate of the AG50 seal is still below 0.021 sccm cm−1 under the conditions of 750 °C, a compressive load of 0.12 MPa and a testing gas pressure of 3.5 kPa to 10.5 kPa. Using the AG50 seal, a high open circuit voltage of above 1.16 V after 6 thermal cycles is achieved for a 10 × 10 cm2 anode-supported single cell (active area of 9 × 9 cm2), which demonstrates the applicability of the AG50 seal in practical SOFC operations.Highlights► Al2O3–HGS composite seals were prepared by tape-casting. ► Leakage was tested at various temperatures, N2 pressures and compressive loads. ► Thermal cycle sealing performance of AG50 was evaluated between 200 and 750 °C. ► Single cell was tested at 750 °C with H2 fuel, air oxidant and AG50 seal.

Industrial-sized planar anode-supported SOFC cells with a cell dimension of 15 × 15 × 0.1 cm and an active area of 13 × 13 cm2 are fabricated through a processing route of tape casting-screen printing-cofiring. Electrochemical performance and thermal cyclicability of the cell are evaluated in a single cell stack at 750 °C with H2 as the fuel and air as the oxidant. With a gas flow rate of 3 L min−1, the initial open circuit voltage (OCV) is 1164 mV, and the stack demonstrates a power density of 380 mW cm−2 at 473 mA cm−2 with an extrapolated maximum power output of 100 W. After three thermal cycles, the reduction of the stack output voltage is around 5%, and the OCV is maintained at a level above 1145 mV. Based on the obtained results, issues related to stack performance, such as cell quality, contact resistance and sealing, are discussed.Highlights► Large-scale anode supported planar SOFC cells fabricated by tape casting-screen printing-cofiring process. ► Electrochemical performance and thermal cyclicability evaluated at 750 °C in a single cell stack. ► Issues affecting the performance of large-scale single cell stack discussed.

LaCo0.6Ni0.4O3−δ (LCN64) was prepared through the polymeric steric entrapment precursor route with Polyvinyl alcohol (PVA) as the entrapment agent and was evaluated as a contact material between the metallic interconnect and the cathode in planar intermediate temperature solid oxide fuel cell stacks (IT-SOFC). The ratio of PVA to metal nitrates and the calcination temperature of the precursor were optimized for the process. The electrical conductivity and thermal expansion coefficient (TEC) of the synthesized LCN64 and its chemical compatibility with SUS 430 were also characterized. The results indicate that 1:4 is a proper ratio of PVA to metal nitrates for process control and safety management; and calcination of the precursor at temperatures above 650 °C leads to formation of single perovskite phase LCN64. The conductivity of fully sintered LCN64 is above 1150 S cm−1 in the temperature range between 100 °C and 800 °C, which is higher than those of conventional contact materials La1−xSrxMnO3 (LSM) and LaNiyFe1−yO3 (LNF). The average TEC is 17.22 × 10−6 K−1 at temperatures below 900 °C, which is higher than those of the metallic interconnect and cell components. Mn and Cr elements contained in SUS 430 migrated into the porous LCN64 layer at 800 °C without chemically forming resistive phases.Highlights► LaCo0.6Ni0.4O3−δ (LCN64) was synthesized using PVA as the entrapment agent. ► Conductivity and thermal expansion coefficient of the LCN64 determined. ► Compatibility between LCN64 and SUS 430 interconnect characterized.

•Cation exchange between LSCN and GDC was identified by XRD at 1150 °C for 10 h.•LSCN performance seems reversible under anodic than cathodic current treatment.•High and low frequency arcs of LSCN show different response to current treatment.Thermochemical compatibilities with Ce0.8Gd0.2O2−δ (GDC) electrolyte and electrochemical behaviors under the condition of anodic or cathodic current treatment are investigated for La0.8Sr0.2Co0.8Ni0.2O3−δ (LSCN) cathode of solid oxide fuel cell (SOFC). X-ray diffractometer (XRD) shows that cation exchange at 1150 °C leads to the formation of solid state solution between the cathode and electrolyte. Considering thermal expansion coefficient (TEC) and conductivity, La1−xSrxCo1−yNiyO3−δ with the composition of La0.8Sr0.2Co0.8Ni0.2O3−δ is indicated as a promising cathode for intermediate temperature SOFC. Electrochemical measurement reveals that the performance of LSCN cathode shows reversibility under anodic with subsequent cathodic current treatment. Further, the low frequency electrode process is strongly affected by anodic current. While the high frequency arc shows independent relationship with current polarization.

NiO–Y2O3 stabilized ZrO2 (YSZ) composite is the state-of-the-art material for the anode support of planar solid oxide fuel cells (SOFCs). To improve its fracture toughness (KC), lanthanum orthoniobate LaNbO4 is synthesized by the method of solid state reaction and added to the mixture of YSZ and NiO at the weight ratio of 47:53. The content of LaNbO4 in the composite is in the range between 5 and 30 wt%. The microstructure of the composites is examined by scanning electron microscopy (SEM); and the chemical compatibility among the components is evaluated by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). Vickers hardness test is performed for estimating the KC of the composites. The results indicate that the KC increases with the addition of LaNbO4 in the composites; and the toughening effect is associated with the grain-refinement in the composite and the domain switch in the monoclinic LaNbO4.Highlights► LaNbO4 synthesized by solid reaction using La2O3 and Nb2O5 as raw materials. ► LaNbO4–NiO–YSZ composites prepared with LaNbO4 contents between 5 and 30 wt%. ► Vickers hardness and fracture toughness of the composites examined.

Non-isothermal compressive deformation was performed on high strength steel 22SiMn2TiB for the study of martensitic phase transformation from deformed austenite. The transformation start temperature Ms decreased with the increase of deformation from 0 to 50 pct, and the variation of deformation rate (0.1 and 10 s−1) and the appearance of deformation-induced ferrite and bainite showed no influence on the change of Ms temperature. The deformation at both the rates increased the volume fraction of retained austenite; however, the carbon content of retained austenite decreased at 10 s−1 and remained basically unchanged at 0.1 s−1. The yield strength of austenite at Ms temperature and the stored energy in deformed austenite were experimentally obtained, with which the relationships between the change of Ms temperature and the thermodynamic driving force for martensitic phase transformation from deformed austenite were established by the use of the Fisher-ADP–Hsu model. And finally, the transformation kinetics was analyzed by the Magee–Koistinen–Marhurger equation.

The contact resistance and chemical compatibility of LaCo0.6Ni0.4O3−δ (LCN) coated Ni–Mo–Cr alloy are investigated at 750 °C in air for more than 530 h to simulate the contact situation of cathode/contact layer/interconnect in SOFC stacks. With La0.72Sr0.18MnO3 (LSM) as the cathode, the area specific resistance (ASR) of LSM/LCN/Ni–Mo–Cr alloy assembly increases to a maximum of 240 mΩ cm2 during the early stage of the test, and decreases after 55 h to a steady level of ∼220 mΩ cm2 till the end of the test. The contribution of formed oxide scale on the alloy to the measured ASR is negligible, compared to that of big AgLaMo2O8 particles sporadically distributed in LCN matrix. AgLaMo2O8 is formed of evaporated Mo from the alloy, Ag from the testing lead and La from the LCN before the oxide scale on the alloy is well developed. This reaction is expected to cease once the oxide scale is fully established.Highlights► The situation of cathode/contact layer/interconnect in SOFC stacks was simulated. ► Compatibility between LCN and Ni–Mo–Cr alloy was characterized. ► The ASR of LSM/LCN/Ni–Mo–Cr assembly was tested at 750 °C in air for 533.5 h.

Carbon deposition and sulfur poisoning are issues that limit the state-of-the-art Ni-YSZ anode material of solid oxide fuel cell to be used in direct hydro-carbon fuels. In the present study, density functional theory calculations are performed to investigate the adsorption of C and S on Ni(111), Cu(111) and alloyed Ni-Cu(111) surfaces. It is confirmed that C and S energetically favor the hollow sites of Ni(111) and Cu(111) surfaces; forming Ni-Cu alloy by addition of Cu into Ni weakens the adsorption of C and S with lowered adsorption energies due to less overlapping between the C 2p or S 3p and the metallic 3d orbits.Highlights► Adsorption energy and electronic structure of adsorbed assemblies were calculated. ► Tendency of adsorption were discussed. ► It is confirmed that Cu lowers the degree of C and S adsorption on Ni surface.

A hot-rolled steel, 22SiMn2TiB, was employed to study the effect of austenite deformation on the microstructure and strength of the subsequently formed lath martensite. It was revealed that the sizes of the martensite packet, block and lath were refined by the tensile deformation of austenite at temperatures above 850 °C. With the increase of the deformation temperature, the packet size increased, whereas the block size decreased. The width of the lath was independent of the prior austenite grain size and the deformation temperature. The refinement of martensite blocks was considered to strengthen the ausformed martensite.

The microstructure evolution and phase transformation of high strength 22SiMn2TiB steel during non-isothermal deformation were investigated in detail. The results indicate that deformation temperature range and amount play a predominant role in phase constitution and volume fraction of the microstructure formed in the process of the non-isothermal compressive deformation. The start martensitic phase transformation temperature Ms is monotonously decreased with the deformation amount and slightly influenced by the deformation rate, and not affected by the cooling rate and initial deformation temperature. The diffusional transformation, such as polygonal ferrite and bainitic ferrite, is promoted by the non-isothermal deformation of austenite under specific circumstances where the deformed austenite passes through its transformation temperature region.Highlights► Ms temperature was lowered by non-isothermal deformation of austenite. ► Ms temperature was monotonously decreased by increasing deformation amount. ► Diffusional transformation was promoted under specific circumstances. ► Deformation temperature range and amount played a crucial role in phase constitution.

Five (Ni52.5Mn23.5Ga24)100−xCox (x = 0, 2, 4, 6, 8) alloys were prepared by arc melting, and the effects of Co addition on the martensitic phase transformation, crystal structure and magnetization were investigated. The phase transformation temperatures Ms, Mf, As and Af are proportional to the content of Co in the (Ni52.5Mn23.5Ga24)100−xCox alloys, which appears to be due to the variation in the valance electron concentration. The Curie temperature is sensitive to the composition of the alloy. As the amount of Co changes, both the Co-Mn exchange interaction and the distance between Mn atoms change. These, in turn, affect the Curie temperature and magnetization behavior of the alloy. The martensite phases in all the alloys are domained in three different orientations, the domain boundary was determined to belong to the family of {1 1 2} lattice planes.

A straight capillary model is developed to estimate the mass leak rate of the cast ceramic tape seals for planar solid oxide fuel cells (SOFCs), which is further rectified with consideration of microstructure complexity including the tortuosity, cross-section variation and cross-link of leak paths. The size distribution of the leak path, effective porosity and the microstructure complexity are the main factors that influence the leak rate of the cast tape seals. According to the model, Al2O3 powders are selected for preparation of the seals by tape casting, and the leak rate is evaluated under various compressive stresses and gauge pressures. The results indicate that Al2O3 powder with D50 value about 2 μm and specific surface area near 5 m2 g−1 can be used for the cast tape seals; and the obtained leak rate can satisfy the allowable leak limit.

One of the critical issues in test blanket module (TBM) system is to reduce tritium permeation from Pb–Li into the water/helium coolant. Use of alumina coating is one of the most promising methods to solve this problem. In the present study, well-adhered alumina coatings on ferritic steel substrates were prepared by the sol–gel method. X-ray diffraction (XRD) and field-emission scanning electron microscope (FSEM) were employed to identify the phase and examine the microstructure of the coating. The coating prepared at 500 °C is amorphous, while that prepared at 650 °C is γ-Al2O3. When calcination temperature is elevated to 1100 °C, α-Al2O3 is formed. The surface of the well-adhered coating was smooth and uniform. No spallations and cracks were observed in the coating or at the scale/alloy interface. The grain size of the coating remains very small even at 1100 °C (in the range 30–40 nm for 1100 °C). The thickness of the coating can be controlled by changing aging time and the number of dipping cycles. The flexibility to coat complex geometries by this method, even inside tubes, is guaranteed.

Conventional Ni-based cermet anodes such as Ni-gadolinia doped ceria (Ni-GDC) suffer from low carbon deposition resistance in direct methane solid oxide fuel cells (SOFCs). Here we show that impregnating proton conducting perovskites like BaCe0.9Y0.1O3−δ (BCY) and BaCe0.9Yb0.1O3−δ (BCYb) in Ni-GDC not only improves the initial polarization performance but also, most importantly, significantly enhances the stability in wet methane fuel (3% H2O in CH4) by inhibiting carbon deposition and formation. In wet methane, the voltage of the cell with the conventional Ni-GDC anode decreases rapidly from 0.58 to 0.15 V within 6 h at 200 mA cm−2 and 750 °C. In contrast, in the case of the cells with BCY + Ni-GDC and BCYb + Ni-GDC anodes, the cell voltage is essentially constant at 0.62–0.65 V over a period of 48 h tested under identical conditions. The microstructure and Raman spectroscopy analysis reveal that the impregnated fine BCY and BCYb particles are preferentially distributed on the surface of the Ni grains in the Ni-GDC anode, decreasing the exposed surface of Ni grains and inhibiting carbon deposition. Also, the proton conducting and fine BCY and BCYb particles can adsorb and decompose water, which in turn reacts with deposited carbon to form CO and H2, alleviating the carbon deposition problem in the anode and thus significantly improving the cell stability of direct methane SOFCs.

Cobaltite-based double perovskite oxides with high electrocatalytic activity and conductivity have been developed as high-performance cathode alternatives for solid oxide fuel cells (SOFCs). However, the use of cobaltite-based double perovskites on Y2O3 stabilized ZrO2 (YSZ)-based SOFCs requires the application of a doped ceria barrier layer. This is due to their poor chemical and physical compatibility with the YSZ electrolyte during high-temperature sintering and fabrication processes. Here we report a viable approach to in operando assemble double perovskites such as PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF), on YSZ electrolyte and thus effectively form an electrode/electrolyte interface without high-temperature processing. The electrochemical performance of the in situ assembled PBSCF cathode is comparable to that of the cathode prepared by conventional methods. A single cell with an in situ assembled PBSCF–GDC (Gd-doped ceria) cathode achieved a peak power density (PPD) of 1.37 W cm−2 at 750 °C and exhibited a high stability at 500 mA cm−2 and 750 °C for 100 h. Surface and cross-sectional microstructure analysis offer solid evidence that the PBSCF–GDC cathode/YSZ electrolyte interface was formed by electrochemical polarization. This work offers new opportunities to effectively and effortlessly use high-performance double perovskite cathodes in commercial SOFCs.

A novel anode with a Ni0.5Cu0.5Fe2O4 (NCFO)–BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) composite on NiO–Y2O3 stabilized ZrO2 (YSZ) is fabricated and investigated in dry and wet (3 mol% H2O) CH4 at temperatures ranging from 650 to 800 °C. For comparison, a conventional NiO–YSZ anode is also prepared. In H2–3 mol% H2O at 600 °C for 2 h, NCFO and NiO are fully reduced to Ni–Cu–Fe alloys (NCF) and Ni, respectively, forming bi-layer NCF–BZCYYb/Ni–YSZ (BL) and single-layer Ni–YSZ (SL) anodes. The polarization resistance of the BL anode in dry and wet CH4 is only approximately 1/5 of that of the SL anode due to the enhancement of NCF–BZCYYb on CH4 oxidation. This improvement is also supported by the results from DC polarization. Carbon deposition is inhibited in the BL anode by adding only 3 mol% H2O into dry CH4 and the carbon formed in dry CH4 can be removed by subsequent exposure of the BL anode to wet CH4. The overall electrochemical performance of the BL anode is significantly stable in wet CH4, which suggests that it is promising for applications in direct CH4 solid oxide fuel cells (SOFCs).