不同成分比例對中溫型固態氧化物燃料電池之Ga-Si-Sr-B系統玻璃密封材料的影響

Abstract

本研究主要以Ga-Si-B-Ca-Sr為參考，嘗試開創本實驗室對於SOFC系統封裝材料的開發，並藉由改變玻璃的Al/Si、La/Si、B/Si及Ga/Si的比例，分別合成出Al系列、La系列、B系列及Ga系列，探討其比例改變所造成封裝材料性質的影響。 在研究中發現，以硝酸物水溶液為前驅物，較容易使原料呈現共熔形式且能在高溫下均勻反應，生成透明產物。在Al系列中，Al2O3作為網絡修飾劑功用，使玻璃轉換溫度(Tg)、熔點(Tm)、結晶起始點(Tx)、結晶溫度(Tc)與軟化點(Ts)下降，熱膨脹係數(CTE)升高；La系列的鑭元素，受熱振動程度小、配位數高、半徑大，但La-O鍵能較弱，使Tg、Tm與CTE上升，Tx、Tc與Ts下降；B系列的硼元素使結構穩定度下降，且產生”硼酸鹽揮發”現象，使Tg、Tm與Ts下降，Tx、Tc與CTE上升；Ga系列的鎵元素，受熱振動程度小且因Ga/Si比例大於1而作為玻璃形成劑，使Tg、Tm、Tx、Tc與Ts上升，但Ga-O鍵能較弱，使CTE上升。 本研究所有的產物在850oC下皆能與LSGM片有良好的黏合，但是兩者成分中的鑭元素與矽元素會交互擴散，所造成的影響還有待研究。YP052(12Ga-10Si-2K-2Ca-4Sr-6B-2La-4Al)在本研究中最接近我們設立的溫度目標，在長時間操作溫度熱處理下不會產生結晶，且與LSGM有良好接合，若降低預先燒結溫度，可期待能減少結晶現象並達到好的氣密效果，而實際的漏氣程度還有待裝置建立後研究。

In this study, we took the Ga-Si-B-Ca-Sr system as a reference to understand the sealing materials for solid oxide fuel cell (SOFC). By changing the compositions ratios of Al/Si, La/Si, B/Si, and Ga/Si, different glass samples were synthesized. The effects of composition on the property of the sealing materials were discussed. It was found that nitrate precursors in aqueous solution were easier to make raw materials that created eutectic form and homogeneous reaction in high temperature region. In the Al series, Al2O3 as a network modifier, make the glass transition temperature (Tg), the melting temperature (Tm), the starting point of crystallization temperature (Tx), the crystallization temperature (Tc) and the softening point (Ts) decrease, the coefficient of thermal expansion (CTE) increase. The La series exhibited low thermal vibration, high coordination number, and large radius but weak bonding energy, which increased Tg, Tm and CTE and reduced Tx, Tc and Ts. For B series, the boron element makes structure unstable and cause “Borate Volatility”, which reduced Tg, Tm and Ts, whereas Tx, Tc and CTE were increased. In the Ga series, the, Tg, Tm, Tx, Tc and Ts were increased and CTE increased, which may due to their low thermal vibration, large Ga/Si ratio ( > 1), and weak Ga-O bonding energy. All products in this study exhibit good adhesion with LSGM film at 850oC, but it was found that La and Si may diffuse across the glass-SOFC interface. The effect of La and Si diffusion remains uncertain and will be further studied. In this study, YP052 (12Ga-10Si-2K-2Ca-4Sr-6B-2La-4Al) most reached our goal. It does not crystallize after a long time at the operating temperature and adhere with LSGM well. If we reduce the pre-sintering temperature, YP052 is expected to have less crystallization and better sealing ability. The leak rate could be measured and discussed after the leakage test system established.