燃料電池透過電化學反應直接將化學能轉成電能，有著高能源使用效率、低汙染物排放及多樣燃料選擇性的優點，為相當被重視的替代能源之一。在已開發的燃料電池中，固態氧化物燃料電池（SOFC）屬於高發電效率的高溫型燃料電池，其系統的整體效率高於其它類型燃料電池。金屬支撐固態氧化物燃料電池（MS-SOFC），因具有較薄電池件、高導電率、高熱導性、良好延展性等優點，可有效降低電池工作溫度及縮短電池啟動運作時間，於快速啟動之發電系統或移動載具之輔助電力裝置等應用，極具潛力及前景，因此開發具有穩定及耐久性的MS-SOFC系統，是目前SOFC技術發展的新趨勢。由於工作溫度的降低，許多新開發的MS-SOFC系統逐漸採用金屬硬焊熔接封裝技術來接合其元件與電池堆，藉由金屬填料產生塑性變形的特性，達到緩衝及吸收熱應力和機械應力的效果，因此，關於MS-SOFC硬焊封裝技術的研究目前也受到相當重視。在MS-SOFC實際運作過程中，相關元件的接合件將會在高溫氧化及還原氣氛下工作，且會受到各元件熱不匹配所產生的熱應力作用，因此，評估MS-SOFC硬焊封裝接合件在高溫氧化及還原氣氛下的耐久機械性質，是發展一套可靠及耐久MS-SOFC系統不可或缺的研究課題。依此，本計畫將分三年有系統地探討適用於MS-SOFC電池堆之硬焊填料/金屬連接板材料接合件在不同氧化及還原氣氛下的高溫張力與剪力機械強度、潛變、熱機疲勞等機械性質，並建立其耐久壽命評估模式。第一年，探討硬焊填料合金成分、環境氣氛與溫度、熱時效處理、受力模式等條件對MS-SOFC硬焊填料/金屬連接板接合件張力及剪力機械強度的影響，並分析其微結構變化及破裂機制。第二年，探討環境氣氛、溫度、熱時效處理、受力模式等條件對MS-SOFC硬焊填料/金屬連接板接合件試片潛變性質的影響，分析潛變破損機制與接合界面微觀結構變化，並建立潛變壽命評估模式。第三年，對硬焊填料/金屬連接板接合件進行異相熱機疲勞試驗及熱機疲勞－潛變交互作用試驗，並結合熱機疲勞壽命數據與潛變壽命數據，尋求建立適用於MS-SOFC硬焊填料/金屬連接板封裝接合件之高溫耐久壽命評估模式。 ;Fuel cells which can directly convert the chemical energy into electricity have been developed for a while as they have higher energy conversion efficiencies and less air pollutants. Solid oxide fuel cells (SOFCs) have the highest efficiency among the fuel cells developed as they utilize solid ceramics as the anode, electrolyte, and cathode and operate at high temperatures. The working temperature and start-up time could be effectively reduced in metal-supported solid oxide fuel cells (MS-SOFCs) thanks to their thinner anode-electrolyte-cathode assembly, good electronic and thermal conductivity, and good ductility. MS-SOFCs with a short start-up time are considered for applications in mobile vehicles and auxiliary power systems such that they have received much more attention in recent development of SOFC technology. With a lower operation temperature in MS-SOFCs, braze seals have been practically applied in MS-SOFCs for sealing the anode-electrolyte-cathode assembly and metallic interconnects. Thermal stresses are generally generated in SOFC components due to thermal mismatch in the thermal cycling of SOFC operation. They can cause significant deformation and damage in the components and degrade the structural integrity and electrochemical performance of SOFC stacks under long-term operation. It is thus necessary to investigate the high-temperature mechanical durability of the braze seal/metallic interconnect joint so as to provide necessary information for design and development of highly efficient and reliable MS-SOFC stacks. The objective of this three-year study is to systematically characterize the high-temperature tensile and shear strength, creep, and thermo-mechanical fatigue properties of a braze seal/metallic interconnect joint in MS-SOFC stacks and to develop effective life assessment models. In the first year, the effects of content of braze seal, thermal aging treatment, and working environments (reducing and oxidizing atmospheres) on the tensile and shear joint strength will be investigated. In the second year, creep tests will be conducted in reducing and oxidizing atmospheres to investigate the creep properties of unaged and thermal-aged joint specimens of braze seal and metallic interconnect. In the third year, out-of-phase thermo-mechanical fatigue tests and thermo-mechanical fatigue-creep interaction tests will be conducted to study the mechanical durability of the given joints under MS-SOFC operating conditions. Based on the creep and thermo-mechanical fatigue testing results, it is intended to develop an effective mechanical life assessment model for braze seal/metallic interconnect joints in MS-SOFC stacks.
