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A novel electrical current applied technique known as flash sintering has been applied to rapidly (within 10 min) densify electrolytes including Ce0.8Gd0.2O1.9 ( GDC20), Ce0.9Gd0.1O1.95 ( GDC10), and Ce0.8Sm0.2O1.9 ( SDC20) for application in Solid Oxide Fuel Cells ( SOFCs). The densification temperature for the three electrolytes was 554°C, 635°C, and 667°C, respectively, which is far below conventional sintering temperatures. All specimens after flash sintering maintained the pure fluorite structure and exhibited a well-densified microstructure. To investigate the flash-sintering mechanism, we have applied Joule heating effect with blackbody radiation theory, and found that this theory could reasonably interpret the flash-sintering phenomenon by matching theoretically calculated temperature with the real temperature. More importantly, one of the materials inherent properties, the electronic conductivity, has been found correlated with the onset of flash sintering, which indicates that the electrons and holes are the primary current carriers during the start of flash-sintering process. As a result, potential densification mechanisms have been discussed in terms of spark plasma discharge. [ABSTRACT FROM AUTHOR]

Cu-Al spinel oxide, which contains a small portion of the CuO phase, has been successfully used in methanol steam reforming (MSR) without prereduction. The omission of prereduction not only avoids the copper sintering prior to the catalytic reaction, but also slows down the copper-sintering rate in MSR. During this process, the CuO phase can initiate MSR at a lower temperature, and CuAl2O4 releases active copper gradually. The catalyst CA2.5-900, calcined at 900 °C with n(Al)/ n(Cu)=2.5, has a higher CuAl2O4 content, higher BET surface area, and smaller CuAl2O4 crystal size. Its activity first increases and then decreases during MSR. Furthermore, both fresh and regenerated CA2.5-900 showed better catalytic performance than the commercial Cu-Zn-Al catalyst. [ABSTRACT FROM AUTHOR]

Abstract: BaZr0.1Ce0.7Y0.1Yb0.1O3 (BZCYYb), a promising proton conductor of poor sinterability used in Solid Oxide Fuel Cells (SOFCs), has been densified in one hour at 850 °C by applying direct current sintering technique (DC-sintering). Under a constant electrical field, the current density through the specimen of BZCYYb rises rapidly when the temperature increases to a certain value. In DC-sintering process, we restrict the current density when the sharp increase occurs. By limiting current density to different values for one hour, we find that current density is the most important factor in DC-sintering process. The conductivity and the grain size of BZCYYb electrolyte increase significantly with the enhanced current density, while the different initial applied electrical fields have negligible effect. The stable stage of DC-sintering process can be explained by Joule heating. Corresponding real temperature of specimens is estimated by applying black body radiation theory. [Copyright &y& Elsevier]

Abstract: In order to lower the sintering temperature and shorten firing time, a novel, effective and facile technique has been developed for sintering Yttria-stabilized zirconia (YSZ) electrolyte thin film. Herein this technique, which employs a weak direct current (DC), is used for the first time in the manufacture of the anode-supported solid oxide fuel cell (SOFC). A single cell is directly assembled using a pre-sintered anode/electrolyte and screen printed cathode and subsequently sintered under electric assistance from room temperature to 800 °C at a heating rate of 5 °C min−1. A fully dense YSZ electrolyte film can be observed by scanning electron microscopy (SEM) and the open circuit voltages (OCVs) are in accordance with theoretical values, confirming that the cell possesses a dense YSZ film. Using hydrogen fuel, the maximum power density of this cell was 0.8, 1.1 and 1.4 W cm−2 at 650, 700 and 750 °C, respectively. We believe this DC assisted sintering technique (DC-AST) may not only reduce the cost, but also maintain the anode nanostructure, thus offering a potentially useful manufacturing technique for SOFCs. [Copyright &y& Elsevier]

Abstract: A fully dense Ce0.8Gd0.2O1.9 (gadolinia doped ceria, GDC) is obtained by a novel using a sintering technique for several seconds at 545°C by applying a direct current (DC) electrical field of 70Vcm−1. The onset applied field value of this phenomenon is 20Vcm−1, and the volume specific power dissipation for the onset of flash sintering is about ∼10mWmm−3. Through contrast with the shrinkage strain of the conventional sintering as well as scanning electron microscopy (SEM) analysis, we conclude that GDC specimens are sintered to fully density under various applied fields. In addition, we demonstrate that the grain size of GDC is decreasing with the increase of applied field and the decrease of sintering temperature. Through calculation, we find that sintering of GDC can be explained by the Joule heating from the applied electrical field. [Copyright &y& Elsevier]

The ability to directly utilize hydrocarbons and other renewable liquid fuels is one of the most important issues affecting the large scale deployment of solid oxide fuel cells (SOFCs). Herein we designed La 0.2 Sr 0.7 TiO 3 –Ni/YSZ functional gradient anode (FGA) supported SOFCs, prepared with a co-tape casting method and sintered using the field assisted sintering technique (FAST). Through SEM observations, it was confirmed that the FGA structure was achieved and well maintained after the FAST process. Distortion and delamination which usually results after conventional sintering was successfully avoided. The La 0.2 Sr 0.7 TiO 3 –Ni/YSZ FGA supported SOFCs showed a maximum power density of 600 mW cm −2 at 750 °C, and was stable for 70 h in CH 4 . No carbon deposition was detected using Raman spectroscopy. These results confirm the potential coke resistance of La 0.2 Sr 0.7 TiO 3 –Ni/YSZ FGA supported SOFCs. [ABSTRACT FROM AUTHOR]