| 摘要: | 燃料電池由於具有高能源效率、低環境污染、分散式電力來源等優點，是近年來各先進國家積極投入研發新替代能源的重點項目之一。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（工作溫度範圍在650-1000oC），其中平板式 SOFC 具有較簡單的結構設計與製作成本、較高能源效率、較低工作溫度（800oC 以下）等優點，成為目前全世界對SOFC 研發的重點。平板式SOFC 電池堆係由陽極、電解質及陰極三者合一燒結所形成的陶瓷固態電池片及金屬雙極連接板重複排列堆疊串聯而成，電池層及組件間則使用特殊的封裝接合劑接合而成。當SOFC 電池堆在運轉使用時，隨著工作溫度改變，由於不同組件間具有不同的熱膨脹係數值，加上工作溫度分佈的不均勻，因而會產生不可忽視的熱應力。雖然在某些情況下，此熱應力不致使SOFC 組件產生瞬間破損，然而在長時間高溫環境操作使用及定期開機、停機循環作動下，會使得由不銹鋼材質所製成的雙極連接板發生潛變及熱機疲勞現象而造成過度變形甚至斷裂，降低電池效率並縮短SOFC 電池堆使用壽命。因此，金屬連接板的潛變與熱機疲勞性質成為評估SOFC 電池堆結構耐久性能的重要考量因子之ㄧ，亦是選擇平板式SOFC 電池堆組件材料的參考依據。本研究計畫將分三年有系統地探討適用於平板式SOFC 電池堆連接板之Crofer 22 高鉻肥粒鐵型不銹鋼的高溫拉伸機械強度、潛變、應力鬆弛、熱機疲勞、微結構變化、破裂機制等性質並建立其耐久壽命評估模式。在第一年的計畫中，主要探討Crofer 22 APU 及Crofer 22 H 二款不銹鋼在不同高溫環境下之拉伸機械性質，以及不同溫度及應力組合下之高溫潛變性質。第二年計畫，以研究Crofer 22 APU 及Crofer 22 H 二款不銹鋼在不同溫度及應變組合條件下的應力鬆弛現象為重點，並建立合適之潛變壽命評估模式。第三年計畫，則將進行Crofer 22 APU 及Crofer 22 H 二款不銹鋼之異相熱機疲勞以及熱機疲勞與潛變交互作用之試驗，並利用相關潛變與熱機疲勞壽命評估模式分析所建立二款不銹鋼潛變與熱機疲勞壽命數據，尋求建立適用於SOFC 金屬連接板之高溫耐久壽命評估模式。 Various types of fuel cells are now being intensely developed around the world because they give higher energy conversion efficiencies, generate less pollutant emissions, and can serve as distributed electricity sources. The solid oxide fuel cell (SOFC) operates at a high-temperature range of 650 to 1000oC in a direct conversion process such that they have the highest efficiencies of all fuel cells. As planar SOFC systems have several advantages over tubular ones such as simple structural geometry, lower fabrication cost, higher energy efficiency, and lower operating temperature (below 800oC), most of the current research on SOFC is being focused on the planar type. A typical unit cell in a planar SOFC stack is composed of a ceramic anode-electrolyte-cathode assembly, a porous nickel mesh, two end bipolar interconnect plates, and gas seals. In practical applications of SOFC, multiple cells are assembled to form a stack and make a serial connection in the electric loop to generate a high voltage and power. The high-temperature operation, however, gives rise to significant thermal stresses due to mismatch of coefficient of thermal expansion between components and temperature gradients in the SOFC stack. Such thermal stresses can cause significant deformation and damages in the components and degrade the structural integrity and electrochemical performance of SOFC stacks under long-term operation. In particular, creep and thermo-mechanical fatigue could take place in the metallic interconnect plates leading to unpredictable, considerable deformation and rupture. Therefore, a comprehensive analysis of creep and thermo-mechanical fatigue properties for the SOFC interconnects is necessary for a success in design and operation of an SOFC system. The aim of this proposed three-year study is to systematically characterize the high-temperature tensile strength, creep, stress relaxation, and thermo-mechanical fatigue properties of Crofer 22 ferritic stainless steels for use in SOFC applications and to develop applicable life assessment models. In the first year, it is proposed to investigate the effects of environmental temperature on the tensile and creep properties of Crofer 22 APU and Crofer 22 H ferritic stainless steels. In the second year, stress relaxation tests will be conducted to investigate the effects of environmental temperature on the high-temperature viscous behavior of the given two stainless steels. It is also intended to develop suitable creep life assessment models for the given steels used in SOFC interconnects. In the third year, out-of-phase thermo-mechanical fatigue tests as well as thermo-mechanical fatigue-creep interaction tests will be conducted to study the long-term structural durability of the given two Crofer 22 stainless steels under SOFC operating conditions. In addition, based on the creep and thermo-mechanical fatigue testing results, it is intended to develop a mechanical life assessment model suitable for metallic interconnects used in planar SOFC stacks. Comprehensive comparisons between the given two Crofer 22 stainless steels will be made on the tensile strength, creep resistance, stress relaxation phenomenon, and thermo-mechanical fatigue damage so as to characterize the influence of addition of refractory elements and associated microstructure. 研究期間：9908 ~ 10007 |
