Fabrication and performance of advanced multi-layer SOFC cathodes

Multilayered cathodes for solid oxide fuel cells are presented. The cathodes are composed of strontium doped lanthanum manganate and yttria stabilised zirconia, the ratio of which is increased with increasing distance from a supporting zirconia electrolyte. Some cathodes additionally carry a number of layers with a graded transition from manganite to cobaltite to add an electronically highly efficient current collector. The cathodes were prepared by spray painting and low temperature sintering. Electrochemical measurements revealed a performance up to 0.2 Ω cm² at 750°C for the first generation of these cathodes. The electrochemical performance was found to be influenced further by the microstructure at the interface close to the solid electrolyte and the quality of electrical contact thorough the sintered electrode.     

Fabrication and characterization of composite electrolyte for intermediate-temperature SOFC

In this study, a ceria-based composite electrolyte was investigated for intermediate-temperature solid oxide fuel cells (SOFCs) based on SDC-25 wt.% K₂CO₃. Sodium carbonate co-precipitation process by which SDC powder was adopted and sound cubic fluorite structure was formed after SDC powders were sintered at 750 °C for 3 h. The crystallite size of the particle was 21 nm in diameter as calculated from data obtained through X-ray diffraction. The conductivity of the composite electrolyte proposed in this study was much higher than that of pure SDC at the comparable temperature of 550-700 °C. The transition of the ionic conductivity occurred at 650 °C. Based on this type of composite electrolyte, single cell with the electrolyte thickness of 0.3 mm were fabricated using dry pressing, with nickel oxide adopted as anode and SSC as cathode. The single cell was then tested at 550-700 °C on home-made equipment in this study, using hydrogen/air. The maximum power density and open circuit voltage (OCV) achieved 600 mW cm⁻² and 1.05 V at 700 °C, respectively.     

A Novel Cell‐Array Design for Single Chamber SOFC Microstack

A novel design of single chamber solid oxide fuel cell (SC‐SOFC) microstack with cell‐array arrangement is fabricated and operated successfully in a methane–oxygen–nitrogen mixture. The small stack, consisting of five anode‐supported single cells connected in series, exhibits an open circuit voltage (OCV) of 4.74 V at the furnace temperature of 600 °C and a maximum power output of 420 mW (total active electrode area is 1.4 cm²) at the furnace temperature of 700 °C. A gas mixture of CH₄/O₂ = 1 leads to best performance and stability.     

Novel glass-ceramic SOFC sealants from glass powders and a reactive silicone binder

The processing of sintered ceramics is often conditioned by the debinding step. The binders may determine some defects in the final product directly, by causing some gas evolution even at an advanced state of densification, due to incomplete decomposition at low temperature, or indirectly, by offering poor adhesion between particles, so that ‘green’ compacts may be easily damaged. The present investigation is aimed at exploring a novel concept for sintered glass-ceramics, based on the adoption of a silicone polymer as reacting binder, providing an abundant ceramic residue after firing. A glass belonging to the CaO-MgO-Al₂O₃-SiO₂ system, already studied as a sealant in solid oxide fuel cell (SOFC) planar stack design, was reproduced in form of ‘silica-defective’ variants, featuring a SiO₂ content, in the overall formulation, reduced up to 15?wt%. The overall silica content was recovered by mixing powders of the new glasses with the silicone: upon firing in air, the interaction between glass powders and polymer-derived silica led to glass-ceramics with the same phase assemblage than that formed by the reference glass and with a CTE of 9.5?×?10^?6 K^-1. The new approach has been successfully applied to the manufacturing of glass-ceramic seals as joining materials for solid oxide cells.     

Fabrication of 8-YSZ thin-wall tubes by powder extrusion moulding for SOFC electrolytes

In this work the processing steps for producing YSZ thin tubes by means of powder extrusion moulding (PEM) technique are investigated. Different feedstocks were prepared from a commercial YSZ powder and a multicomponent thermoplastic binder system based in polypropylene and paraffin wax. The surface coating of YSZ powder with stearic acid in a high-performance dispersing instrument reduces the viscosity of the feedstock one order of magnitude respect to a feedstock with a same composition and un-coated powder. This fact allows increasing the solid loading up to 58 vol.% to obtain sintering tubes with densities higher than 97% and with wall thickness lower than 200 μm.     

Planar Metal‐Supported SOFC with Novel Cermet Anode

Metal‐supported solid oxide fuel cells are expected to offer several potential advantages over conventional anode (Ni‐YSZ) supported cells. For example, increased resistance against mechanical and thermal stresses and a reduction in material costs. When Ni‐YSZ based anodes are used in metal supported SOFC, elements from the active anode layer may inter‐diffuse with the metallic support during sintering. This work illustrates how the inter‐diffusion problem can be circumvented by using an alternative anode design based on porous and electronically conducting layers, into which electrocatalytically active materials are infiltrated after sintering. The paper presents the electrochemical performance and durability of the novel planar metal‐supported SOFC design. The electrode performance on symmetrical cells has also been evaluated. The novel cell and anode design shows a promising performance and durability at a broad range of temperatures and is especially suitable for intermediate temperature operation at around 650 °C.     

Fabrication of a Novel Biocompatible Magnetic Biomaterial with Hyperthermia Potential

Preparation and characterization of a novel biocompatible magnetic biomaterial having hyperthermia potential is reported in this study. Fe³⁺ and Ni²⁺ (2:1) cosubstituted hydroxyapatite nanoparticles were synthesized by simple wet precipitation method followed by freeze‐drying which on heat treatment at 1150°C yielded the above mentioned biocompatible magnetic biomaterial composed of hydroxyapatite and β‐tricalcium phosphate along with nickel ferrite. The product was characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscope along with composition analysis. The magnetic behavior was analyzed by vibrating sample magnetometer and biocompatibility was assessed by testing the toxicity on Hela cells using MTT assay. The hyperthermia potential of the material was studied using induction heating. The prepared material has the potential to generate sufficient heat that could be easily controlled by magnetic field parameters and amount of sample. Hence, it can be a potential candidate for making implantable thermoseed for hyperthermia treatment.     

Design,Fabrication, and Characterization of Novel Porous Conductive Scaffolds for Nerve Tissue Engineering

Highly conductive polypyrrole/graphene (PYG) nanocomposite was synthesized with chemical oxidation process via emulsion polymerization and used for the preparation of novel porous conductive gelatin/chitosan-based scaffolds. The effect of PYG loading on various properties of scaffolds was investigated. The obtained results indicated that by introducing PYG into the polymeric matrix, the porosity and swelling capacity decreased while electrical conductivity and Young's modulus demonstrated increasing trend. The in vitro biodegradation test revealed that pure gelatin/chitosan matrix lost 80% of its weight after six weeks in the presence of lysozyme whilst the biodegradation rate was significantly lower for the conductive scaffolds. Furthermore, Schwann cell attachment and proliferation were evaluated by MTT assay and SEM image and the results revealed significant cell biocompatibility of the conductive scaffold with low amount of PYG. The results confirmed the potential of gelatin/chitosan/PYG compounding as a suitable biomaterial for using in nerve tissue engineering applications in which electrical stimulation plays a vital role.     

新颖金属卟啉膜修饰电极的研制和对分子氧的催化

本文采用三种方法(滴涂,SAM和CV法)将修饰剂[PyTPPMn(Ⅲ)]Cl修饰与玻碳电极表面,并用循环伏安法研究了修饰电极在各种介质中对分子氧的催化性能。发现该卟啉化合物对分子氧均具有一定的催化还原作用,并就其在各种介质(0．5mol／LH2SO4、乙醇和0．1mol／L碳酸钠溶液)中的催化还原机理做了深入的讨论。比较三种方法修饰的电极,按CV法制得的[PyTPPMn(Ⅲ)]Cl膜修饰电极,修饰剂吸附牢固,响应灵敏、稳定。有望作为检测溶液中分子氧和双氧水的传感器。     

Flow Characteristics in a Honeycomb Structure to Design Nanobubble Generating Apparatus

A nanobubble generator with honeycomb structures producing a large amount of water including large nanobubble density in a short time is described. The nanobubble-generating performance is investigated for large and small apparatus having different honeycomb cell dimensions by applying computational fluid dynamics (CFD) coupled with a population balance model (PBM). The CFD simulation shows that a significant pressure drop and shear stress occur in the bubbly flow in the honeycomb cell. The numerical model is based on the Eulerian multiphase model and the PBM is used to calculate the bubble size distribution. The obtained CFD-PBM results are compared with the experimental results for large and small apparatus. Bubble size distributions in the honeycomb structure under different inlet absolute pressure can be predicted by the PBM. The maximum shear stress is determined as the main controlling factor for nanobubble generation.     

Fabrication,characterization, and performance of YbDSB ternary compounds for IT‐SOFC applications

(Yb₂O₃)_x(Dy₂O₃)_y(Bi₂O₃)_1?x?y (0.04≤x+y≤0.20) powders (xYbyDSB) were synthesized by modified sol‐gel Pecchini method. The powders were characterized for structural, surface morphological, thermal, and electrical properties and power density measurements by means of X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis/thermal gravimetry (DTA/TG), and impedance spectroscopy, respectively. Lattice parameters and crystalline size of δ‐phase of Yb₂O₃‐ and Dy₂O₃‐doped Bi₂O₃ samples were calculated from the X‐ray diffraction data. Surface and grain properties of the related phases were determined by SEM analysis. In the investigated system, the maximum electrical conductivity was observed as σ=0.954 S cm^?1 for 6% mol Yb₂O₃ and 6% mol Dy₂O₃ at 800°C among all δ‐YbDSB systems. Cathode supported electrochemical cell was fabricated and 6Yb6DSB was used as the electrolyte. Maximum power density of single cell with an active area of 1.5 cm² is 72.50 mW/cm² at 700°C.     

蜂窝式板束结构的设计及比较

简要介绍了一台板壳式换热器蜂窝式板束的结构特点、参数及制作,由此引出一种新型的蜂窝夹套,并将此种蜂窝夹套与传统的蜂窝夹套作以比较。     

Fabrication of a Novel Calcium Carbonate Composite Ceramic as Bone Substitute

The coral, whose main composition is aragonite‐type calcium carbonate, has been widely used as bone substitute in clinic. However, the study on calcium carbonate bioceramic has not been largely reported due to difficulty in sintering calcium carbonate which is liable to evidently decompose at low temperature. In this study, a novel calcium carbonate composite ceramic was fabricated by sintering fast at a low temperature. A degradable, biocompatible phosphate‐based glass (PG) which grew liquid at a low temperature was added as sintering agent in the sintering process. The sintering schedule was explored by thermal analysis. The phase composition, microstructure, compressive strength, and biocompatibility of calcium carbonate composite ceramics were evaluated. The results revealed that the optimum holding time at the sintering temperature was 20 min. The obtained calcium carbonate composite ceramics did not produce calcium oxide but new compounds according to phase analysis. The compressive strength of calcium carbonate composite ceramics correspondingly increased with growing addition of PG ranging from 10 to 50 wt%. The cell proliferation on the calcium carbonate composite ceramic was not compromised but augmented compared to the neat calcium carbonate ceramic without adding PG as sintering agent. The novel calcium carbonate composite ceramic is a promising bone substitute for bone defects.     

Development and Fabrication of a New Concept Planar‐tubular Solid Oxide Fuel Cell (PT‐SOFC)

The paper reports a new concept of planar‐tubular solid oxide fuel cell (PT‐SOFC). Emphasis is on the fabrication of the required complex configuration of Ni‐yttria‐stabilised zirconia (YSZ) porous anode support by tert‐butyl alcohol (TBA) based gelcasting, particularly the effects of solid loading, amounts of monomers and dispersant on the rheological behaviour of suspension, the shrinkage of a wet gelcast green body upon drying, and the properties of final sample after sintering at 1350 °C and reduction from NiO‐YSZ to Ni‐YSZ. The results show that the gelcasting is a powerful method for preparation of the required complex configuration anode support. The anode support resulted from an optimised suspension with the solid loading of 25 vol% has uniform microstructure with 37% porosity, bending strength of 44 MPa and conductivity of 300 S cm^—1 at 700 °C, meeting the requirements for an anode support of SOFC. Based on the as‐prepared anode support, PT‐SOFC single cell of Ni‐YSZ/YSZ/LSCF has been fabricated by slurry coating and co‐sintering technique. The cell peak power density reaches 63, 106 and 141 mW cm^—2 at 700, 750 and 800 °C, respectively, using hydrogen as fuel and ambient air as oxidant.     

Novel Fabrication of Nickel Hydrosilicate Hollow Spheres

Hollow Ni₃Si₂O₅(OH)₄ nanospheres were synthesized via a facile deposition process at room temperature. The diameters of the products are in the range of 300–320 nm, and the average wall thickness is about 10 nm. Furthermore, the synthesis process of Ni₃Si₂O₅(OH)₄ hollow spheres was briefly described and this solution-based approach could be extendable to the preparation of other spherical materials with hollow interiors.     

新型层状结构可见光催化剂的制备与性能研究

以合成层状双羟基金属氧化物（LDH）为掺杂手段,制备了Zn-Cr LDH、Zn-Ti LDH两种半导体光催化剂。XRD和SEM分析表明Zn-Cr LDH和Zn-Ti LDH具有层状结构,层间距分别为0.73 nm和0.69 nm。UV-vis分析表明Zn-Cr LDH在410 nm和560 nm分别有2个最大吸收峰,而Zn-Ti LDH无法吸收400 nm以上的可见光。在可见光（≥420 nm）照射与添加AgNO3作为电子受体的条件下,光分解水实验中,反应300 min后Zn-Cr LDH产氧量约为0.79 mL。在光降解亚甲基蓝（MB）中,MB在反应300 min后被完全降解。而Zn-Ti LDH在实验中不具备光催化活性。     

Fabrication of Transparent Spinel Honeycomb Structures by Methyl Cellulose–Based Thermal Gelation Processing

Transparent MgAl₂O₄ spinel of flat as well as honeycomb structure was fabricated by employing thermally induced gel casting of the slurry with 56 wt% solid loading containing 0.2 wt% of methylcellulose. The green specimens were pressureless sintered to 98%–99% of theoretical density with no open porosity at an optimum temperature of 1700°C. Final densification by hot isostatic pressing of both the specimens at the optimum temperature of 1800°C and 195 MPa pressure enabled further elimination of residual porosities and full densification resulting in theoretical density of 3.58 g/cc. The design of the honeycomb was such that it exhibited a surface area to volume ratio of 0.65 cm²/cm³ and a relative density of 0.69. The hardness of the honeycomb specimens has been found to be 13 GPa, which is at par with the solid specimens processed under identical conditions. Solid specimens of around 4 mm thickness exhibited a transmission of >80% in the visible (0.4–0.8 μm) region. Specimens were also tested according to ASTM procedures and have shown a flexural strength (σ_f) of 195 MPa and plane‐strain fracture toughness (K_Ic) of 1.87 MPa·m^1/2 as reported in this study.     

改良式真空潜弧系统制备TiO2纳米流体

利用改良式真空潜弧制造系统制备纳米二氧化钛悬浮液,改良重点为原有真空潜弧制造系统的压力控制系统、冷却液循环系统、参数控制系统、机台尺寸等部件,获得了可制备出较稳定、颗粒较小的二氧化钛纳米悬浮颗粒的制备条件及颗粒尺寸再现性良好的实验平台.所制备纳米二氧化钛颗粒为锐钛矿(Anatase)结构,在光催化性能实验方面,纳米二氧化钛在光波长360～380 nm时具有良好吸收能力.在吸附实验中,所制备的二氧化钛颗粒的吸附效果优于商用的二氧化钛及氧化锌纳米颗粒.在亚甲基蓝的脱色实验中,所制备的二氧化钛颗粒能在60 min内达到脱色率100%.     

新型机械臂设计及运动学研究

提出了一种新型3自由度混联机械臂。运用Pro/E和Adams软件对其进行了运动学仿真分析,结果表明,该机构具有较大的工作空间及平稳的运动性能,且结构简单,在注塑机自动化生产中具有良好的应用前景。     

Fabrication of continuous linear pores in an SOFC anode using unidirectional carbon fibers as sacrificial templates

We describe the manufacturing of a solid-oxide fuel cell anode of NiO−8 mol.% Y₂O₃-stabilized ZrO₂ with micro-scale continuous linear pores (CLPs) and nano-scale interparticle pore structures, achieved through thermal decomposition of unidirectional amorphous carbon fibers. The CLP structure prepared by this sacrificial templating method is characterized by its controllable uniform size, a tortuosity (ie, uniformity) of 1.003, and a coefficient of variation of 0.59. These highly regular CLPs are expected to minimize Knudsen diffusion, resulting in enhanced mass transport of hydrogen gas at the active sites, known as triple-phase boundary sites. Simulations using the Lattice Boltzmann Method (LBM) were used to determine the mass transport in the systems. An optimum diameter of 3 µm and an interparticle pore size of 185 nm was shown to maximize the acceleration of mass transport of H₂ and maintain the number of TPB sites to minimize concentration overpotential. Thus, the proposed porous design can increase the energy efficiency of a solid-oxide fuel cell primarily by reducing the concentration overpotential.