Co-sintering Technique Research Articles

A novel dual-layer ceramic hollow fibre membrane reactor for methane conversion

A highly compact multifunctional ceramic hollow fibre membrane reactor with a unique dual-layer structure (DL-HFMR) has been developed in this study for methane conversion using a single-step co-extrusion and co-sintering technique. The developed DL-HFMR consists of a thin outer oxygen separation layer (approximately 75 μm) supported on an inner Ni-based catalytic substrate (171 μm). The former is comprised of 40 vol.% La 0.8Sr 0.2MnO 3− δ (LSM) and 60 vol.% yttria-stabilized zirconia (YSZ), while the latter consists of 30 vol.% NiO and 70 vol.% YSZ. The inner support layer possesses a highly porous structure and is catalytic active, after an easy post-reduction of NiO to Ni, to the reactions for methane conversions, such as partial oxidation of methane (POM) to syngas. Benefiting from this membrane reactor design as well as the single-step fabrication technique, a surface area/volume ratio of approximately 2770 m 2/m 3 can be achieved with a great adhesion between the separation and catalytic support layers. CO selectivity over 90% with a H 2/CO ratio of about 2 can be obtained at 950 °C. Although methane conversion is greatly affected by coke formation during the reaction, the catalytic activity of the inner layer is easily recovered by periodically switching between methane and the sweep gas at high temperatures, because the coke formed during the reaction can be removed by the permeated oxygen.

Single-step fabrication and characterisations of electrolyte/anode dual-layer hollow fibres for micro-tubular solid oxide fuel cells

An electrolyte/anode hollow fibre (HF) for micro-tubular solid oxide fuel cells (SOFCs), i.e. a cerium–gadolinium oxide (CGO)/Ni–CGO dual-layer HF, has been developed in this study via a novel single-step co-extrusion and co-sintering technique, and followed by a reduction process. The microstructure of the developed dual-layer HFs, which are co-sintered at 1450–1550 °C, can be characterised by an electrolyte outer layer of approximately 80 μm supported by an anode inner layer of around 220 μm. Benefiting from the advantages of this fabrication technique, great adhesion between the anode layer and the electrolyte layer can be achieved without any crack formation during the co-sintering. Moreover, no elemental inter-diffusion between layers, such as Ni, was observed even at 1550 °C. With the increasing co-sintering temperature, mechanical strength of the developed dual-layer HF, gas-tightness of the electrolyte layer and electrical conductivity of the anode layer are increased. However, gas permeability through the anode layer decreases dramatically with the increasing temperature, which may greatly reduce the efficiency of the related micro-tubular SOFC. According to the investigations on the effects of co-sintering temperature on the mechanical, structural and electrical conducting properties of the dual-layer HFs, a co-sintering temperature at 1500 °C is recommended for the construction of the electrolyte/anode half-cell for micro-tubular solid oxide fuel cells (SOFCs).

Intermediate temperature fuel cell with a doped ceria–carbonate composite electrolyte

The performance of a composite electrolyte composed of a samarium doped ceria (SDC) and a binary eutectic carbonate melt phase has been examined. This material shows higher ionic conductivity than pure SDC in intermediate temperature region. SDC with different morphologies is obtained by co-precipitation, sol–gel and glycine-nitrate combustion preparation techniques. A tri-layer single cell is prepared with a cost-effective co-pressing and co-sintering technique. It is found that the surface properties of SDC and the electrolyte thickness have a great influence on the fuel cell performance. When the co-precipitated SDC is used as the electrolyte component and CO 2/O 2 gas mixture is adopted as the cathode oxidant gas, a fuel cell with an excellent performance is obtained, which has a peak power output of 1704 mW cm −2 at a current density of 3000 mA cm −2 at 650 °C. The influence of cathode atmosphere is examined with conductivity measurement and fuel cell performance test. The results support the concept of O 2−/H +/CO 3 2− ternary conduction.

Evaluation of Micro LSM-Supported GDC/ScSZ Bilayer Electrolyte with LSM–GDC Activation Layer for Intermediate Temperature-SOFCs

A gadolinium-doped ceria (GDC)/scandia-stabilized zirconia (ScSZ) bilayer electrolyte on a microtubular (LSM) support was prepared via extrusion of a microtubular cathode support and subsequent surface coatings with electrolyte and anode slurries. The GDC/ScSZ bilayer electrolyte was obtained on the LSM support using a cosintering technique, and the LSM-supported microtubular solid oxide fuel cells (SOFCs) were evaluated using field-emission scanning electron microscopy, X-ray diffraction, and electrochemical measurements in wet hydrogen (3% ) atmosphere. An LSM–GDC activation layer was also introduced between the cathode tube and the electrolyte layers for improvement of cell performance. The micro-SOFC exhibited a stable open-circuit voltage above 1.03 V in the temperature range from 450 to , and the cell generated a maximum power density of 15, 73, 230, and at 500, 600, 700, and , respectively. This result indicates that our developed cosintering fabrication technology can realize a stable and high-performance, LSM-supported micro-SOFC.