以旋轉電極法製備鐵鉻基燃料電池連接板高溫氧化性質之探討

Abstract

金屬連接板由於必須在高溫環境下運作，因此需要優異的抗高溫氧化性及良好的導電性。但目前的合金仍未完美達成上述要求，且成本仍然偏高。為了改善上述的缺點，本論文將利用粉末冶金法製成指定形狀之成品，如此便不必經過傳統製程後續的繁複加工，達到節省成本之目的 。 在成分的選擇上，由於鐵鉻錳合金是常見的金屬連接板材料，另外根據前人研究添加鈷可以大幅改善高溫氧化、高溫電阻及熱膨脹性質。故本論文將以鐵-鉻-錳-鈷為主要研究對象。 本論文使用旋轉電極法製造所需之合金粉末，再壓胚燒結直接製成指定形狀之成品。所得之合金再進行150小時不連續高溫氧化實驗、高溫電阻實驗、金相成分分析等後續之分析及性質檢定。 由於粉末冶金法製出之合金因孔洞過多使其高溫氧化性質不如預期，故另外嘗試在合金表面上鍍上一層LSM薄膜，以期堵住其孔洞，進而改善其高溫氧化性質。實驗結果發現鍍上LSM薄膜僅能小幅改善其抗高溫氧化性質，因為合金和鍍層之熱膨脹係數不夠匹配以及合金表面孔洞影響造成鍍膜有所破損，使其保護效果降低。

The SOFC metal interconnector must have excellent oxidation behavior in high temperature and good electrical conductivity, because it operates in high temperature surroundings, but the cost is still high currently. So the thesis use power metallurgy method to manufacture the products, which avoids complicate manufacture process and reduce the cost. The Fe-Cr-Mn alloy is the common SOFC metal interconnector material, and according to previous research, the addition of Co reinforces the high temperature oxidation behavior, electrical resistance, and thermal expansion. For these advantages, the thesis use Fe-Cr-Mn-Co for the composition of SOFC metal interconnector. The thesis manufactures alloy powders by REP method, and sinters it for products in next procedure. Finally the products is analyzed by non-continuous 150hr high temperature oxidation, high temperature electrical resistance, and metallographic analysis. Due to the porous surface, the high temperature oxidation behavior is weaker than expected. To reinforce it, the thesis tries coating LSM film on the surface of the product. The results show that LSM coating improves high temperature oxidation behavior slightly, due to the mismatch of thermal expansion coefficient(CTE) and the porosity of the alloy surface cause the LSM film damaged partly.