Honeycomb Unit Cell Research Articles

Two-cell Stack Test of Honeycomb SOFCs with Air Preheating Channels

We report a two-cell stack test of honeycomb SOFCs with air preheating channels. The honeycomb was made of 3YSZ with 3×3 channels. The size of each channel was 5×5 mm and the thickness of channel walls was 1 mm. Electrode materials were Ni(60 wt%)/8YSZ and La0.7Sr0.3MnO3. The OCV of 2.19 V was obtained at 800 ºC. Ag plates were used for the gas sealing and the interconnection between the honeycomb unit cells. The high value of OCV and the stable current during the experiment indicates a good gas sealing and small leak currents. After the measurement, the stack was cooled to room temperature, and held for 10 days, then it was heated again to 800 ºC. A small amount of OCV reduction was observed, however, no reduction was observed in the maximum power density. This successful test indicates that the interconnection using Ag plates is promising for honeycomb SOFC stacks.

Numerical and experimental uniaxial loading on in-plane auxetic honeycombs

Auxetic honeycombs show in-plane negative Poisson's ratio properties; they expand in all directions when pulled in only one, and contract when compressed. This characteristic is due to the reentrant shape of the honeycomb unit cell. The cell convoluteness gives a geometric stiffening effect that affects the linear elastic properties of the whole cellular solid. In this paper finite element simulations are carried out to calculate the in-plane Poisson's ratio and Young's moduli of re-entrant cell honeycombs for different geometric layout combinations (side cell aspect ratio, relative thickness and internal cell angle) subjected to uniaxial loading. The results show a high sensitivity of the mechanical properties for particular ranges of the geometric cell parameters. An image data detection technique is used to extract displacements and strains from an aramid paper re-entrant honeycomb sample in a tensile test. The comparison between numerical and experimental results shows good agreement.

Two dimensional metallic photonic crystal in the THz range

A two dimensional metallic photonic crystal with three honeycomb unit cells was constructed. Two gaps for an s wave were observed in the frequency range of 0.78–1.7 THz, which is beyond the cut-off frequency. The band structure and the transmission spectra were simulated by the plane wave expansion method and the multiple scattering approach, respectively. The agreement between measurement and calculation was reasonably good. The effects induced by structure's disorder was studied. We found that the misalignment of the cylinders in the photonic crystal can result in a serious change of the transmission spectra.