- 學位論文
燃燒法一步驟合成GDC-NiO-C固態氧化物料電池陽極基材粉末
One-step Synthesis of GDC-NiO-C Anode for IT SOFC with GNP Method
摘要
CeO2 具有高的氧離子傳導率，在中溫（600~800℃），CeO2 仍然具有令人驚豔的氧離子傳導率，因此被視為新一代固態氧化物燃料電池研究之方向。本研究使用GNP法(Glycine nitrate process)來合成GDC（Gadolinia Doped Ceria）以解決利用固態合成法需要相當高的溫度與時間以及不易形成固溶體之問題。並利用Raman觀察Gd2O3固溶至CeO2中氧空位之振動模式，進而分辨GNP法與固態合成法是否形成GDC固溶體。實驗發現，利用GNP法合成之GDC於700℃煆燒1小時即可形成固溶體，大大降低合成之溫度與時間；並且將GDC固溶至40mol%可以發現，晶格常數將由5.4053 Å增加至5.4435 Å，證明燃燒法可以將GDC固溶至至少達到30 mol%。 另一方面，利用NiO與CeO2不易固溶之特性，使用GNP法一步驟合成均勻混合之GDC-NiO複合陽極粉末可避免傳統球磨混合所帶來之污染與時間，並利用TEM觀察GDC在加入NiO成分後結晶變化之情形。 在前驅物溶液中加入棉花纖維，於自燃過程中將棉花纖維燃燒後所形成之殘碳當作造孔劑，在經過單軸成型、煆燒、燒結以及還原即可成為均勻混合之多孔陽極，其孔隙率可達47%，並使用BEI觀察孔隙與元素分佈之情形，以及嘗試使用導電AFM來觀察整體陽極導電鎳連通之影像。 本實驗嘗試加入銅成分來減少含碳燃料所導致之積碳情形，發現於煆燒將產生由鎳催化之細小石墨管，並於還原過後形成銅鎳合金，如此不僅具有抑制積碳之能力，也大大增加整體陽極之導電度以及機械強度。
並列摘要
CeO2 becomes a new choice for the anode and electrolyte materials for intermediate-temperature SOFC thanks to its substantial oxygen ionic conductivity in the intermediate temperature range of 600~800℃. As it takes a very high temperature and a long time to form a solid solution of GDC (gadolinia doped ceria) with solid state method, GNP (glycine nitrate process) was used as the major approach to synthesize GDC in this study. Furthermore, the Raman spectra of the GDC from GNP method showed distinct vibration modes of oxygen vacancies which were absent in the case of solid state method, indicating that it is more efficient to form GDC solid solution with GNP method, which only requires calcinations at 700℃ for 60 minutes. Moreover, it was observed that the lattice parameter increased with linear stability from 5.4053 Å to 5.4366 Å as Gd2O3 was doped into CeO2 up to 30mol%. The lattice parameter continued to rise to 5.4435 Å as the doping moved up to 40mol% while the previous stability was interrupted. On the other hand, we can synthesize GDC-NiO with one step GNP method to diminish the pollution and time cost thanks to the fairly low solubility of NiO-CeO2 system. Moreover, transmission electron microscopy can be used to observe the crystallinity before and after the addition of NiO. After dry press, calcination, and sintering, well-mixed, porous, and nano-sized GDC-NiO-C anode was synthesized with 47vol% porosity by adding cotton fiber into the precursor before combustion. The study further used BEI (backscattered electron image) to observe the NiO, CeO2, Gd2O3, and pore distribution, and conductive AFM (atomic force microscope) was used to help confirm the connection within the reduced anode substrate. When CuO was added into the anode substrate to prevent the carbon deposition with GNP method, graphite tube was observed to appear around anode powders after calcinations. Subsequent reduction, on the other hand, turned CuO+NiO into CuNi alloy, helping increase the conductivity and strength of the anode.