Relationship Between Particle and Plasma Properties and Coating Characteristics of Samaria-Doped Ceria Prepared by Atmospheric Plasma Spraying for Use in Solid Oxide Fuel Cells

Samaria-doped ceria (SDC) has become a promising material for the fabrication of high-performance, intermediate-temperature solid oxide fuel cells (SOFCs). In this study, the in-flight characteristics, such as particle velocity and surface temperature, of spray-dried SDC agglomerates were measured and correlated to the resulting microstructures of SDC coatings fabricated using atmospheric plasma spraying, a manufacturing technique with the capability of producing full cells in minutes. Plasmas containing argon, nitrogen and hydrogen led to particle surface temperatures higher than those in plasmas containing only argon and nitrogen. A threshold temperature for the successful deposition of SDC on porous stainless steel substrates was calculated to be 2570?°C. Coating porosity was found to be linked to average particle temperature, suggesting that plasma conditions leading to lower particle temperatures may be most suitable for fabricating porous SOFC electrode layers.     

Atmospheric Plasma Spraying Low-Temperature Cathode Materials for Solid Oxide Fuel Cells

Atmospheric plasma spraying (APS) is attractive for manufacturing solid oxide fuel cells (SOFCs) because it allows functional layers to be built rapidly with controlled microstructures. The technique allows SOFCs that operate at low temperatures (500-700 °C) to be fabricated by spraying directly onto robust and inexpensive metallic supports. However, standard cathode materials used in commercial SOFCs exhibit high polarization resistances at low operating temperatures. Therefore, alternative cathode materials with high performance at low temperatures are essential to facilitate the use of metallic supports. Coatings of lanthanum strontium cobalt ferrite (LSCF) were fabricated on steel substrates using axial-injection APS. The thickness and microstructure of the coating layers were evaluated, and x-ray diffraction analysis was performed on the coatings to detect material decomposition and the formation of undesired phases in the plasma. These results determined the envelope of plasma spray parameters in which coatings of LSCF can be manufactured, and the range of conditions in which composite cathode coatings could potentially be manufactured.     

Solution Precursor Plasma Spray of Nickel-Yittia Stabilized Zirconia Anodes for Solid Oxide Fuel Cell Application

In conventional plasma spray of SOFC components, the large NiO and YSZ particles used, about 50-150 microns for high porosity coating, reduce the density of three-phase sites for electrode reaction. In this article, the SPPS process was used to synthesize and deposit Ni-YSZ anodes. The results show that several process parameters have significant effects on the microstructure and phase composition of the deposited material. The deposits were composed of tower-like, irregularly shaped agglomerates and smooth surface deposits. The sizes of the agglomerates increase with the decrease of the plasma-torch power and most are not completely molten during the impact. After heat treatment to reduce the NiO present in the as deposited coatings, the coatings were found to contain spherical YSZ particles about 0.5 μm in diameter distributed in a continuous Ni matrix, which is verified by both SEM observation and electrical resistance measurement. The coatings have 30-50% porosity. This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2007.     

NiO包覆YSZ固体氧化物燃料电池阳极材料的制备研究

采用包覆沉淀法制备NiO包覆YSZ阳极粉。用包覆沉淀法在YSZ颗粒表面均匀包覆一层氧化镍，600℃下煅烧得到NiO-YSZ固体氧化物燃料电池阳极粉。应用此材料制备的SOFC阳极在1400℃烧结4h。经过SEM扫描电镜分析，高温电导测试，用这种方法制备的SOFC阳极中，NiO分布更加均匀，YSZ、NiO交替排布并有效的连接在一起，使阳极结构得到优化，电池性能提高。     

NiO包覆YSZ固体氧化物燃料电池阳极材料的制备研究

采用包覆沉淀法制备NiO包覆YSZ阳极粉.用包覆沉淀法在YSZ颗粒表面均匀包覆一层氧化镍,600 ℃下煅烧得到NiO-YSZ固体氧化物燃料电池阳极粉.应用此材料制备的SOFC阳极在1400℃烧结4 h.经过SEM扫描电镜分析,高温电导测试,用这种方法制备的SOFC阳极中,NiO分布更加均匀,YSZ、NiO交替排布并有效的连接在一起,使阳极结构得到优化,电池性能提高.     

Development of a Ni/Al2O3 Cermet-Supported Tubular Solid Oxide Fuel Cell Assembled with Different Functional Layers by Atmospheric Plasma-Spraying

A cermet-supported tubular configuration amenable to preparation by a relatively low-cost thermal spraying process is proposed. An Al₂O₃-Ni cermet thick deposit prepared by flame spraying is employed as both support tube and anode current collector. Atmospheric plasma spraying (APS) has been employed to prepare the anode, cathode, and stabilized ZrO₂-based electrolyte with the aim of reducing manufacturing costs. Gas-tightness of the APS electrolyte has been achieved by a postdensification process. The effects of the densification process on the gas-tightness of the plasma-sprayed YSZ electrolyte and the open-circuit voltage of the SOFC have been investigated. The effects of the microstructures of the plasma-sprayed anode, electrolyte, and cathode on the performance of the SOFC test cell have been investigated.     

Microstructure and Electrochemical Behavior of a Structured Electrolyte/LSM-Cathode Interface Modified by Flame Spraying for Solid Oxide Fuel Cell Application

Plasma-sprayed yttria-stabilized zirconia (YSZ) can be potentially employed as electrolyte layers in solid oxide fuel cells (SOFCs). The formation of a structured electrolyte surface characterized by convex micro deposits generated by only partially molten particles at spraying will increase the specific surface area and subsequently improve the output performance of SOFCs. However, using completely molten YSZ particles during plasma spraying leads to the formation of locally flat surface. In this study, flame spraying was employed to deposit YSZ particles on YSZ substrate using surface-melted particles. The deposition was carried out at different spray distances on YSZ substrate preheated to 650 °C. The surface and cross-section morphology of YSZ particles were characterized by SEM. The electrochemical behavior of single cell with the structured cathode was characterized by the electrochemical impedance spectroscopy. The results show that spray distance exhibits significant influence on the morphology of deposited YSZ particles. The cathode polarization of a structured cathode was decreased by about 30-43% compared to a flat cathode at different temperatures.     

Study on the Pore-formers for Porous Anode Substrates of Solid Oxide Fuel Cell

采用甘氨酸硝酸盐法合成了超细的La0.7Sr0.3Cr0.5Mn0.5O3-δ(LSCM)粉末,并把制备的阳极粉末与3种不同含量的造孔剂活性炭、淀粉和石墨混合制备多孔阳极基底。应用阿基米德排水法测试了多孔阳极基底的孔隙率,得到最大孔隙率为45%。接着再采用SEM、EDS和XRD等材料表征手段对阳极基底的表面形貌和结构进行了分析,结果显示混合20%(质量分数)的活性炭制备的阳极基底孔隙分布均匀,并没有裂纹出现。甲烷催化实验得到混合20%活性炭造孔剂制备的阳极基底在高温下的催化性能最好,甲烷转化效率达到71.88%.     

流延浸渍法制备Cu-CeO2-YSZ固体氧化物燃料电池阳极

通过流延浸渍法制备Cu-CeO2-YSZ阳极,采用淀粉做造孔剂,确定了多孔YSZ基体的制备工艺,主要包括造孔剂用量及流延浆料配比.并通过复合流延制备多孔YSZ支撑的多孔-YSZ/致密-YSZ复合基体,以Pt浆为阴极,通过电池放电考察了氢气条件下多孔YSZ孔隙率、Ce和Cu的浸渍条件等对Cu-CeO2-YSZ阳极性能影响.结果表明,原料中淀粉含量为65%(质量分数),1500℃烧结6 h得到多孔YSZ孔隙率可达到70%左右.采用真空顺次浸渍法制备20%Cu-10?O2-YSZ(质量分数)阳极,其电池800℃时的最大功率密度为113 mW/cm2.     

Oxidation Behavior and Electrical Properties of De-siliconized AISI 430 Alloy with Mn1.5Co1.5O4 Coating for Solid Oxide Fuel Cell Interconnect

Oxidation of Metals - The effect of de-siliconization on the oxidation behavior of AISI 430 stainless steel used for solid oxide fuel cell interconnect application was investigated....     

Microstructure and Properties of Porous Ni50Cr50-Al2O3 Cermet Support for Solid Oxide Fuel Cells

The microstructure of the cermet support significantly influences the performance of solid oxide fuel cells (SOFCs). The properties required for the support include high electrical conductivity, necessary permeability, good match of thermal expansion with other layers, and high strength. In this study, a flame-sprayed porous Ni50Cr50-Al₂O₃ cermet was designed as the support of SOFCs. The effect of cermet microstructure on its gas permeability, electrical conductivity, thermal expansion coefficient (TEC), and bending strength was investigated. Results show that the gas leakage rate of the cermet increased with the increase of polyester content in the starting powder. The cermet exhibited a thermal expansion coefficient of 11.39 × 10^?6 K^?1 from 25 to 1000 °C. Moreover, the electrical conductivity of the cermet increased significantly and reached 1015 S/cm after sintering at 1000 °C for 15 h. The bending strength of the cermet reached 171 MPa. The cermet stability at high temperatures and SOFCs’ performance are discussed.     

Structural, Mechanical and Erosion Properties of Yttrium Oxide Coatings by Axial Suspension Plasma Spraying for Electronics Applications

Yttrium oxide (Y₂O₃) coatings have been prepared by axial suspension plasma spraying with fine powders. It is clarified that the coatings have high hardness, low porosity, high erosion resistance against CF₄ -containing plasma and retention of smooth eroded surface. This suggests that the axial suspension plasma spraying of Y₂O₃ is applicable to fabricating equipment for electronic devices, such as dry etching. Surface morphologies of the slurry coatings with splats are similar to conventional plasma-sprayed Y₂O₃ coatings, identified from microstructural analysis. Dense coating structures with no lamellar boundaries have been seen, which is apparently different from the conventional coatings. It has also been found that crystal structure of the suspension coatings mainly composed of metastable monoclinic phase, whereas the powders and the conventional plasma spray coatings have stable cubic phase. Mechanism of coating formation by plasma spraying with fine powder slurries is discussed based on the results.     

Chemistry of the Ammonia Pressure Process for Leaching Ni,Cu, and Co from Sherritt Gordon Sulphide Concentrates

The paper relates to the laboratory and pilot plant studies that have been carried out by Sherritt Gordon Mines Ltd., Metallurgical Research Div., in developing the ammonia pressure leach process for extracting copper, nickel, cobalt, and sulphur from high grade nickel concentrate produced from Lynn Lake ores, and describes in some detail the chemistry of the process.     

Development and characterisation of (Ni, Cu, Co)-YSZ and Cu-Co-YSZ cermets anode materials for SOFC application

To improve the internal reforming reactions at SOFC anode, alternative (Ni, Cu, Co) -YSZ and Cu-Co-YSZ anode cermets materials are coated by atmospheric plasma spraying (APS). The spray parameters including carrying gas flow rate, spraying distance, argon flow rate and hydrogen flow rate were investigated by an orthogonal experiment to fabricate gas-permeable anode cermets coatings. Scanning electron microscopy and X-ray diffraction are used to characterise the morphology and structure of coated films respectively. The porosity was deduced by the statistical image analysis. By proper selection of the spray parameters to decrease the particles velocity and temperature, the sprayed coatings monometallic and bimetallic ones show that the cross porosity is dependent of metal weight ratio. In fact, when the metal percentage increases, the porosity decreases. Monometallic Ni-YSZ, Cu-YSZ and Co-YSZ cermets with a weight ratio of (3:2) appear to be less porous than those with (1:1) and (2:3) ones respectively, to reach a maximum porosity of 21.57% for Co-YSZ cermet of (2:3) weight ratio. Cu-Co-YSZ bimetallic cermet coating with weight ratio of (0.5:1:2.5) is more porous than those with (1:2:3) and (2:1:2) weight ratios respectively. Its porosity is about 19.15% which is closed to that of Ni-YSZ (2:3) coating. The X-ray diffraction results showed that the metal content in the cermets have a negligible influence on the crystalline phase structure. Such bimetallic materials anode are very interesting because Co diffuses in Cu lattice offering thus, best electronic conductivity, thermal stability and an avoided carbon formation, by replacing Ni with an electron conductor such as Cu that does not catalyze carbon formation.     

Effect of Cu, Ni on the property and microstructure of ultrafine WC-10Co alloys by sinter-hipping

Sub-micron size (0.4-0.6 μm) Co-Cu/Ni composite powders were synthesized by a co-precipitation method. The effects of minor Cu and Ni additions on the microstructure and the mechanical properties of ultrafine WC-10Co alloys were investigated using scanning electron microscope, X-ray diffraction and mechanical properties tests. The results show that Co-Cu binder phase refines the WC grains and increases the hardness of the base alloys. But the addition of Ni can't refine the WC grains and increase the hardness. The addition of minor Cu or Ni can improve transverse rupture strength of alloys through the solid solution strengthening. However, adding excess Cu can lead to the decrease in transverse rupture strength. With the partial substitution of Co by Cu and Ni, the hardness and transverse rupture strength of the alloys have a little change.     

On the influence of sol-gel derived CeO2 coatings on high-temperature oxidation of Co, Ni and Cu

The effects of CeO₂ coatings on high-temperature oxidation of Co, Ni and Cu have been investigated as a function of temperature at oxygen pressures from 1×10⁻⁴ to 1 atm. The oxidation mechanisms for Co and Cu are essentially unaffected by CeO₂ coatings, whereas the oxidation rate of Ni decreases by approximately one order of magnitude. The oxygen pressure dependence does not change markedly with CeO₂ coatings for any of the metals studied. For oxidation of Ni plus CeO₂ coatings, the temperature dependence is less marked at lower temperatures, whereas essentially the same behavior is observed for Co and Cu with and without the coating. Differences in the effects of CeO₂ coatings for the three metal systems have been attributed to the relative influence of grain boundary transport on the overall rates of oxidation.     

Comparative Study of the Magnetic Properties and Glass-Forming Ability of Fe-Based Bulk Metallic Glass with Minor Mn,Co, Ni,and Cu Additions

Fe_(43)M_5Cr_(15)Mo_(14)C_(15)B_6Y_2 (M=Mn,Co,Ni,and Cu in at.%)bulk metallic glasses(BMGs)are synthesized using the suction casting technique,and the glass-forming ability(GFA),microstructure,and thermal and magnetic properties of these glasses are extensively examined using X-ray diffraction,differential scanning calorimeter,and vibrating sample magnetometer techniques.Among the four BMG alloys,Fe_(43)Ni_5Cr_(15)Mo_(14)C_(15)B_6Y_2 exhibits the lowest coercivity and the highest saturation magnetization,Curie temperature,effective magnetic moment,and GFA.By contrast,Fe_(43)Mn_5Cr_(15)Mo_(14)C_(15)B_6Y_2 presents the poorest magnetic properties,such as the highest coercivity and the lowest saturation magnetization,Curie temperature,and effective magnetic moment.Fe_(43)Cu_5Cr_(15)Mo_(14)C_(15)B_6Y_2 demonstrates the lowest thermal stability and GFA.The observed thermal,structural,and magnetic properties of these BMG alloys are discussed in terms of the kinetics of BMG synthesization and the formation of different ferromagnetic,ferrimagnetic,and antiferromagnetic phases.     

Phase stability of the X2AlTi (X: Fe,Co, Ni and Cu) Heusler and B2-type intermetallic compounds

Ordering and phase separation between the B2 and L21 phases in the X2AlTi (X: Fe, Co, Ni, Cu) intermetallic compounds were investigated. The B2/L21 continuous ordering was determined using the diffusion couple technique in the temperature range of 1273–1573 K. It was found that the substitution of Co for Fe results in raising the B2/L21 ordering temperature and that of Cu for Ni brings about widening of the B2+L21 two-phase region on both the NiAl and NiTi sides. It is shown that the maximum temperatures of B2/L21 order–disorder transition (TcB2/L21max), the tricritical temperatures (TtB2/L21) and the phase boundaries of the miscibility gap between the B2 and L21 phases in the XAl–XTi pseudobinary systems can be well described by the 3d+4s electron concentration of the elements occupying the X site. On the basis of this finding, the phase stability and the interchange energies between Al and Ti in the next nearest neighbors of X–Al–Ti (X: Ti, V, Cr, Mn, Fe, Co, Ni and Cu) system are discussed.     

An Instant,Green, Microwave Irradiated Process for the Preparation of Advanced,Hybrid, Nanoflower of Thorium Oxide and Thorium Oxalate Hydrate Useful for Broad Application Spectrum

Protection of Metals and Physical Chemistry of Surfaces - We report a facile and reproducible method to synthesize advanced, homogenized, hybrid, nanoflower of thorium oxide and thorium oxalate...