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|標題:||Investigation on high strength Al2O3/B2O3/ Al2O3bonding|
Transient Liquid Phase Bonding
|摘要:||Due to the characteristics of excellent resistance against high temperature, corrosion, friction and the absorption of impurities, etc..., fine ceramics are now playing an important role in the evolution of modern engineering. However, in the case of manufacturing items with huge size or complicated structure, where the single-body forming is impossible, joining techniques must to be applied. Consequently, the most important course is updating the joining technique.
Alumina bulks coated with different thickness of layer of boron oxide were joined at various times in air. The microstructure and phases of the joint interface were investigated by scanning electron microscopy (SEM), and by low angle X-ray diffraction.
It is found that, the thickness of joint interlayer decreases with increasing joining time and doesn't change much with increasing thickness of initially coated boron oxide layer. It can also be found that needle-like structure of ceramic compounds form at the joint. The needle-like structure exist some relations with in creasing jointing time as follow: The needle-like compound is the thickest and less pin-hole is observed in joint when joining for 15 hours. While increasing to 24 hours, the compound adjacent alumina bulks branches. As the joining time is increased to 36 hours the dissolution of the needle-like structure happens. This study shows the sequence of appearance of compounds is 3Al2O3-B2O3, 2Al2O3-B2O3 and 9Al2O3-2B2O3, with increasing joining time, where the 3Al2O3-B2O3 is a metastable phase. Furthermore, the SEM showed the fracture surface occurred in the interlayer between compound and alumina. The best compactability of joining interlayer cross-section microstructure was reached as joining at 800℃ for 15hours under 15KPa and with 10.5μm thick layer. The average bending strength reaches the maximum value of 155MPa at this condition.|
精密陶瓷由於其耐高溫、耐磨耗、耐腐蝕、阻止外來異物的吸收等特性，再加上其他特殊物理功能，已成為近代工程最具發展潛力之材料。然而，對於較大尺寸或較複雜之構件，製作上往往無法一體成型，必須借由接合技術加以接合為成品，針對實質應用時，隨之面臨而來更重要的課題便是接合技術的提昇。 本研究將氧化鋁表面蒸鍍上不同厚度之氧化硼層，在空氣中以不同時間進行接合。其後，對接合後之界面進行微結構觀察、X-ray相組成鑑定及四點彎曲強度測試。 結果顯示，接合界面之厚度隨著接合時間的增加而減少，隨著膜厚的增加，不會有太大的改變。接合界面有針狀物產生，其結構由破斷面X-ray及SEM觀察，針狀物隨接合時間之增加，於15小時最粗，排列最緻密，到了24小時，尖端開始分叉，直到36小時，針狀物消失。並由3Al2O3-B2O3、2Al2O3-B2O3及9Al2O3-2B2O3三相共存；最後3Al2O3-B2O3消失，9Al2O3-2B2O3相增加。此外，由破斷面SEM中可發現，破斷的發生在氧化硼與氧化鋁基材接合處。在中間層膜厚10.5μm，接合條件溫度800℃、時間15小時及荷重15KPa有最大接合強度，平均為155MPa，此時接合界面之針狀物亦最為緻密。
|Appears in Collections:||材料科學與工程學系|
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