Deni S. Khaerudini

Prospects of oxide ionic conductivity bismuth vanadate-based solid electrolytes

Abstract The benefits of lowering the operation temperature of solid oxide fuel cells (SOFCs) have attracted great attention worldwide. There has been an enormous effort in the literature for the improvement of the electrolyte materials working at lower temperatures. The family of BiMeVOx (Bi–bismuth, Me–dopant metal, V–vanadium, Ox–oxide) materials has been found to have specific properties as oxide ion conductor (electrolyte) for low operation temperature. These materials exhibit uniquely structural features rather different from those of other solid electrolytes. It is possible to use these as the electrolyte in SOFCs. This article attempts to review the main structural and electrochemical characteristics of BiMeVOx materials in order to show a guideline for designing novel BiMeVOx-based electrolyte for low-temperature SOFCs. The prospects and challenges for the application of these materials as the electrolyte are discussed.

Mechanisms of methane decomposition and carbon species oxidation on the Pr0.42Sr0.6Co0.2Fe0.7Nb0.1O3−σ electrode with high catalytic activity

Carbon deposition on Pr0.42Sr0.6Co0.2Fe0.7Nb0.1O3−σ (PSCFN) and Ni–yttria stabilized zirconia (Ni–YSZ) due to thermal CH4 decomposition under dry CH4 has been investigated by using temperature-programmed reaction techniques. The morphologies of carbon formed are characterized by using scanning electron microscopy (SEM). It is found that carbon nanofibers are obviously formed on PSCFN while spherical carbons are formed on Ni–YSZ. Analyses of the results on CH4 temperature-programmed decomposition and O2 temperature-programmed oxidation reveal that the high catalytic activity for the cracking of CH4 and the easier oxidation of the generated carbon species on PSCFN could be the main reason why PSCFN shows high performance and good stability in direct CH4 fuel solid oxide fuel cells (SOFCs).

Superhydrophobic surface as a fluid enhancement material in engineering applications

In this study, a superhydrophobic surface and its relation to the enhancement of the droplet fluid dynamics to the surface of the object materials was investigated. As the comparison, hydrophilic and uncoated surface of an object also investigated. The investigations used height of impact at 89 mm. The high quality speed camera is employed to investigate the droplet dynamic on a copper foil and a calcium fluoride surfaces. Both of the materials are coated with superhydrophobic and hydrophilic surfaces separately. The droplet diameter was analyzed using the program PHANTOM. The droplet contact angle was analyzed by the Goniometry method. The water was dropped on the calcium fluoride and the copper foil using a syringe (sharp tip) with initial droplet diameter of 1.9 mm. To record the droplet fluid shape, the photo micro sensor was placed inside the trigger box below the syringe. The results showed that the superhydrophobic surface both on copper foil and calcium fluoride enhanced the mobility of a droplet compared to the hydrophilic and the uncoated surfaces. The results showed that the maximum droplet diameter on the copper foil coated by the superhydrophobic, the hydrophilic and the uncoated surfaces are 4.7, 5.0, 5.2 mm, respectively; and for the calcium fluoride are 4.5, 5.1 and 5.5 mm, respectively. Meanwhile, the results for the droplet contact angle on the copper foil coated by the superhydrophobic, the hydrophilic and the uncoated surfaces are 20°, 90°, 160°, respectively; and for the calcium fluoride are 25°, 95°, 165°, respectively.

Effect of CeO{sub 2} addition on the properties of FeAl based alloy produced by mechanical alloying technique

Iron aluminides based on FeAl is notable for their low materials cost, ease of fabrication and good corrosion, suffixation and oxidation resistance. However, the application based on these unique properties still require the development of Fe-Al based alloy since it shows some drawbacks such as a lack of high temperature strength and low ductility. To improve the mechanical properties of FeAl based alloy, ceria (CeO2) will be added to this compound. FeAl based alloy produced by the mechanical alloying (MA) technique. The developed specimens then assessed with respect to oxidation behaviour in high temperature, scale microstructure and hardness. The surface morphologies of the alloy evaluated and observed using scanning electron microscopy (SEM) with an energy dispersive X-ray spectroscopy (EDX). The phase structures of oxide scale formed on them were identified by X-ray diffraction (XRD). The results found that the FeAl intermetallic compound containing CeO2 0.5 wt.% is less pores and CeO2 1.0 wt.% is mor...