- 學位論文
SA-Tyrannohex全纖維碳化矽複合材料於高溫離子輻照下空泡行為與晶粒尺寸之效應
The grain size effect and behavior of ion irradiation induced cavities in SA-Tyrannohex all fiber SiC composite under high temperature environments
摘要
碳化矽複合材料在高溫下之機械性質、化學性質穩定與抗輻照活性的特點被認為是相當具有潛力發展於核融合反應器第一面牆的材料，然而第一面牆之材料需承受高溫且高劑量的照射，而奈米晶粒材料(Nanocrystalline Material)應用於核能環境下之自癒效應(self-healing effect)，可能是改善承受高輻射劑量材料的新方向，近年來被大量討論，而本論文則是利用SA-Tyrannohex全纖維複合材料進行氦、矽單雙射束實驗，觀察空泡缺陷的生成行為，與單晶材料之結果做比較，探討晶界對空泡抑制的成效為何。 本論文利用SA-Tyrannohex全纖維碳化矽複合材料進行單射束矽離子、氦離子及氦、矽離子雙射束佈值，且佈值溫度皆為高溫(>1073K)環境。SA-Tyrannohex全纖維碳化矽複合材料在單射束矽離子輻照20dpa，1200 ℃下並未觀察到空孔(void)，而SA-Tyrannohex全纖維碳化矽複合材料，在低劑量(15000appm)單射束氦離子輻照未觀察到氦氣泡生成於材料中，然而在高劑量(45000appm)之佈值情況下可觀察到氣泡生成，對比單晶碳化矽於同低劑量下觀察到氦氣泡，且高劑量下所觀察到的氣泡密度高出多晶複合材料一個數量級。回顧過去文獻，比較CVD多晶碳化矽、CVI多晶碳化矽材料與Hi-Nicalon Types 纖維於本論文相符劑量下之氣泡尺寸密度，可觀察到晶粒尺寸越小(晶界面積越大)在高溫情況下有抑制空泡生成的趨勢。
並列摘要
Silicon carbide compoiste is a promising material for first wall and blanket components in fusion reactors due to the great strength and low radioactivity under high temperature environment. Besides, several studies have shown that nanocrystalline materials can enhance the irradiation tolerance by enhancing defects recovery via interfaces and grain boundaries. However, it is not for sure that the realationship of small grian size SiC can suppress the cavities formation or not. Furthermore, the detail of grain size effect on irradiation induced defects should be understood. In this work, SA-Tyrannohex all fiber SiC composite was irradiated by Si2+ single beam ,He+ single beam that the helium accmulation concentration up to 45000appm and Si/He dual beam condition. All of the iradiation condition were conducted at high temperature environment(>1073K).The microstructure evolution of irradiated SiC was examined by transmission electron microscopy. Cavities can be observed in dual beam irradiated SA-Tyrannohex SiC composite specimens and 45000appm He implanted specimens. Comparison to single crystal SiC, CVD polycrystalline SiC and CVI polyctstalline SiC irradiated in the same condition ,SA-Tyrannohex all fiber SiC appears to have excellent radiation tolerance under high temperature condition by suppressing the cavities formation.Besides, grain boundaries seems to hava a capability to enhance the point defects recombination.