The objective of this study is"development of ultra thin film solid oxide fuel cell for low temperature application through improvement of ionic conducting property by control of nanostructure of electrolyte". We suggest an innovative process to deposit ultra thin metal alloy film on nanoporous substrate followed by oxidation to form dense electrolyte layer. And low-temperature ionic conduction mechanism through controlled nanostructure of electrolyte is also investigated.

○ CNTN : Solid oxide fuel cells have a limitation in their low-temperature application due to the low ionic conductivity of electrolyte materials and difficulties in thin film formation on porous gas diffusion layer. These problems can be cleared by improvement of ionic conductivity through controlled nanostructure of electrolyte and adopting nanoporous electrodes as substrates which have homogeneous submicron pore size and highly flattened surface. In this study, ultra-thin oxide films having submicron thickness without gas leakage is deposited on nanoporous substrates. By oxidation of metal thin films deposited onto nanoporous substrates with pore size of 20nm - 200nm using dc-magnetron sputtering at room temperature, ultra-thin and dense ionic conducting oxide films with thickness of about 30nm - 300nm is realized. The specific material properties of the thin films including gas permeation, grain/grain boundaries formation, change of crystalline structure/microstructure by phase transition are also investigated for optimization of ultra thin film deposition process and improvement of ionic conducting property of electrolyte. Development of high ionic conducting electrolyte is conducted through investigation of ionic diffusion mechanism in amorphous/nanocrystalline phase, which is easily controlled during oxidation of metal thin film, by in-situ measurement of electric properties. With the obtained results from optimized film deposition process and improved ionic conducting electrolyte, a prototype of low-temperature SOFC operating 200^oC - 500^oC is fabricated and its property is reported.

• Silica nanorods are of proven importance in such diverse fields as energy production and storage, flexible electronics, and biomedicine due to the unique characteristics that emerge from their mechanical properties. There have been a lot of previous studies on nanoporous silica, Especially in the field of drug delivery materials. The nanoporous silica has been reported that difference of bioactivity and biodegradability depend on porosity and the pore size; thus, the nanoporous silica can be controlled by porosity and pore size during manufacturing process. In addition, biodegradability nanoporous silica was taken drug to the internal and surface pores by capillarity. In this study, the biodegradable nanoporous silica nanorods are fabricated using capillary force of AAO template. The porosity of silica nanorods are deliberately controlled by changing water/alkoxide molar ratio of the precursor solution. Porosity of each acquired nanorod was checked using BET, and degradation properties of the nanorods are investigated are deliberately using SEM.

A Ni-Zr HMFC using a double layer consisting of a hydrogen permeable membrane of Ni-Zr (64/36) and a SiC + phosphoric acid electrolyte deposited on porous Ni substrate was successfully built and the FC performance was recorded at 200oC. Although there was a large loss of OCV (~0.6 V) and output due to the hydrogen leak due to the hydrogen film defect by the unoptimized process and the current collection problem, the operation of the Ni-Zr HMFC was confirmed for the first time.