• 作者： Tsai, Dah-Shyang; Wei, Yung-He
• 中文摘要： 以加熱分解甲醯氨提高溶膠pH值的方式,製備氧化鋯/氧化鋁膠體凝膠,燒結此膠體凝膠時所伴化的緻密化與相變為本研究之主旨,緻密化兩個主要的障礙分別為:氧化鋁.theta.-.alpha.相變所衍生之孔洞與氧化鋯的抑制晶粒成長作用,此抑制作用使相變衍生孔隙的移去倍加困難。緻密化障礙在氧化鋁相變後最為明顯,若無氧化鋯,氧化鈦燒結助劑的作用包括:(1)加速氧化鋁相變; (2)增進晶粒成長,因此降低孔洞的配位數,以利孔洞之移去; (3)氧化鋁相變後提高緻密化速率,氧化鋯的存在使氧化鋁晶粒成長受阻,連帶阻礙氧化鈦的助燒作用,加以大部分的氧化鈦溶於氧化鋯而非氧化鋁,更降低氧化鈦的助燒效用。1,275.degree.C以上燒結含氧化鈰與氧化鈦的凝膠,液相燒結促進緻密化速率與晶粒成長。相分析結果顯示氧化釔或氧化鈰均能幫助保有氧化鋯正方相,但氧化鈦不能。 1,500.degree.C燒結15vol% ZTA(摻雜2wt%氧化鈦,3mol%氧化釔)得到最細的顯微結構,氧化鋁晶粒平均粒徑1.29.mu.m,氧化鋯0.57.mu.m ,其中氧化鋯單斜相為 8vol%,此ZTA陶瓷破裂韌性5.7MPa m/sup (1/2)/。
• 英文摘要： ZrO/sub 2/-Al/sub 2/O/sub 3/ gels were prepared in this work by raising pH of colloidal sols from decomposing formamide. The densification and the associated phase change during pressureless sintering of these gels were investigated. Two major densification barriers were those pores generated by .theta.-.alpha. phase transformation of.gamma.-Al/sub 2/O/sub 3/ and the grain growth inhibition of ZrO /sub 2/ which caused pore elimination more difficult. The barriers became prominent especially right after the phase change of alumina. The effects of TiO/sub 2/ as sintering aid for .gamma.-Al/sub 2/ O/sub 3/ were (1) enhancing the phase transformation rate; (2) promoting grain growth and reducing the coordination number of pore, which would facilitate the pore elimination; and (3) elevating the densification rate after .gamma..arrr..alpha. transformation. The presence of ZrO/sub 2/ inhibited the grain growth of Al/sub 2/O/sub 3/, hence the TiO/sub 2/ effects were retarded. Additionally since most of TiO/sub 2/ was dissolved in ZrO/sub 2/ instead of Al/sub 2/ O/sub 3/, the TiO/sub 2/ effects were further reduced by ZrO/sub 2/. The liquid phase occurring in CeO/sub 2/- TiO/sub 2/-ZrO/sub 2 /-Al/sub 2/O/sub 3/ system above 1,275.degree.C enhanced densification rate and grain growth of both ZrO/sub 2/ and Al/sub 2/O/sub 3/ in sintering. The phase analysis indicated that Y/sub 2/O/sub 3/ and CeO/sub 2/ were effective in retaining tetragonal ZrO/sub 2/, and TiO/sub 2/ had little effect. The finest microstructure was obtained by sintering 15vol% ZTA doped with 2wt% TiO/sub 2/ and 3mol% Y/sub 2/O/sub 3/ at 1,500.degree.C. The average grain sizes were 1.29.mu.m for Al/sub 2/O/sub 3/ and 0.57.mu.m for ZrO/sub 2/. The monoclinic phase content in ZrO/sub 2/ was 8vol%. The fracture toughness was 5.7MPa m/sup (1/2)/.
• 中文關鍵字： 燒結; 氧化鋁; 氧化鋯; 凝膠; 相變態; 斷裂韌性; 晶粒生長; 晶粒粗化
• 英文關鍵字： Sintering; Alumina; Zirconium Oxide; Colloidal Gel; Phase Transformation; Fracture Toughness; Grain Growth; Grain Coarsening