本研究主旨在探討固態氧化物燃料電池(SOFC)用GC-9封裝玻璃陶瓷和金屬連接板不銹鋼(Crofer 22 H)與GC-9封裝玻璃陶瓷和陶瓷電極板(PEN)接合件之介面破裂阻抗及破壞模式。藉由製作三款三明治試片，經不同時效處理在不同溫度下(25 oC-800 oC)測試，藉以評估不同溫度與時效處理對接合件介面破裂阻抗的影響。 實驗結果顯示，經過100小時時效處理後之封裝玻璃陶瓷與金屬連接板之接合介面破裂阻抗與時效處理前在不同溫度下並無明顯之差異。至於經過1000小時時效處理後之介面破裂阻抗與經過100小時處理後試片在相同溫度下有些許差異，推測與封裝玻璃陶瓷經過較長時效處理後結晶相的增加及介面裂紋成長於不同氧化層之間有關，然而隨著溫度變化的趨勢並無明顯之差異。在室溫至700 oC間，介面破裂阻抗會隨著溫度增加而提高，且破裂阻抗最大值發生在700 oC ，此乃700 oC高於GC-9之玻璃轉化溫度，使GC-9有明顯的黏滯現象，致使裂縫跨橋效應發生；在700 oC至800 oC則會隨著溫度增加而下降，主要是因為跨橋效應影響下降且750 oC高於玻璃軟化溫度，玻璃流動性大增所致。關於封裝玻璃陶瓷與陶瓷電極板接合件之介面破裂阻抗，僅在室溫下測試，裂縫會沿著介面成長，然而在其他高溫下，裂縫皆直接穿過陶瓷電極板並未沿著介面成長。實驗結果顯示，在室溫下，介面破裂阻抗經過100小時時效處理後有明顯的提升。 由微結構及破斷面分析顯示，封裝玻璃陶瓷與金屬連接板介面有兩種破壞模式。第一，脫層現象發生在玻璃陶瓷基材與鉻酸鋇層之界面。第二，脫層現象發生於鉻酸鋇層之內。對於封裝玻璃陶瓷與陶瓷電極板介面，裂縫於陶瓷電極板與玻璃陶瓷基材之介面以及在玻璃陶瓷基材裡成長。 另外，藉由對一款SOFC電池堆進行具有介面裂縫之有限元素熱應力模擬分析，且將計算所得之圓形裂縫尖端在特定模態I及模態II比例角之應變能釋放率與實驗所得之介面破裂阻抗比對，發現該款SOFC電池堆所能容許最大的介面裂縫或缺陷尺寸為70 m。 The interfacial fracture energy of glass-ceramic (GC-9)/metallic interconnect (Crofer 22 H) and glass-ceramic/PEN joints for solid oxide fuel cell (SOFC) stack is investigated using a four-point bending test technique. The interfacial fracture energy is determined at room temperature, 650 oC, 700 oC, 750 oC, 800 oC by testing three types of sandwich-like specimens. The effects of temperature and aging treatment on the interfacial fracture energy are studied. A 100 h-aging treatment does not significantly influence the interfacial fracture energy of glass-ceramic/metallic interconnect joint. Compared with that of 100 h-aged condition, a difference is found for the 1000 h-aged interfacial fracture energy at each given temperature. It may result from change of crystalline phase content in a longer aging treatment and difference in fracture site. However, the variation trend of interfacial fracture energy with temperature is similar for all the given aged conditions. The interfacial fracture energy increases with temperature from room temperature to a peak value at 700 oC. As 700 oC is higher than the glass transition temperature (668 oC), a greater viscosity takes place and causes a crack bridging phenomenon. The interfacial fracture energy decreases at 750 oC due to a softening behavior of GC-9 as the temperature is higher than the softening temperature (745 oC). The interfacial fracture energy decreases further at 800 oC as a result of flowability of GC-9. For the glass-ceramic/PEN joint, interfacial cracking takes place only when the test is conducted at room temperature. At elevated temperatures, crack penetrates though PEN directly leading to specimen fracture without interfacial cracking. Comparison of the interfacial fracture energy for non-aged and 100 h-aged specimens indicates the interfacial fracture energy increases after a 100 h-aging treatment. Through analysis of interfacial microstructure, two types of fracture modes are identified for the glass-ceramic/metallic interconnect joint. Firstly, delamination takes place at the interface between the glass-ceramic substrate and chromate layer. Secondly, delamination occurs within the chromate layer. For the glass-ceramic/PEN joint, crack propagates along the interface between GC-9 and PEN and also kinks into the glass-ceramic layer. A simulation through finite element analysis is conducted to calculate the energy release rate at the crack front of an interfacial circular crack placed at the highly stressed region in a prototypical SOFC stack subjected to thermal stresses. Comparison of the simulation and experimental results at specific mixity angles between Mode I and Mode II indicates that the critical crack or defect size at the interface of the joint of GC-9 glass-ceramic sealant and Crofer 22 H interconnect in the given SOFC stack is 70 m.
