機械合金法製備奈米二氧化鈦顆粒/鋁複材之熱分析研究

Abstract

本研究係採用奈米級TiO2粉末及Al粉為原始材料，經過不同時間的機械合金球磨後，將球磨過粉末壓製成胚體，於高溫爐內進行內造反應生成Al2O3 + TiAl3 / Al複合材料。由DTA熱分析及X-ray繞射研究發現：在機械合金製程中隨著球磨時間的增加，由於混合的越均勻，使原子間的擴散更容易，而使反應越容易進行，反應溫度由混和0小時的981℃降至混和46小時的916 ℃。在46小時球磨後，由於機械合金中累積之應變能，於熱處理時釋放使得部分粉末得以克服活化能而產生反應。另外將試片壓胚包覆在石墨粉中於700℃進行熱處理，在此保護性氣氛下鋁粉表面氧化膜的增長受限，使得反應可以連續的進行而不受抑制，進而使Al及TiO2可以近乎完全反應形成Al2O3 + TiAl3 / Al複合材料。

In this study, Aluminum powder and TiO2 nanoparticles were used as the raw materials, and then mechanical alloyed under different milling time. It is shown from thermal analysis and x-ray diffraction: The temperature at which reaction form alumina and titanium aluminide decreases with milling time. These improvements due to milling were attributed to the enhanced mixing of the components leading to shorten diffusion paths. After 46 hours milling, the strain energy accumulated during mechanical alloying released in heat treatment makes partial powder to overcome the activation energy of the reaction and to react at lower temperature. The consolidated disc which immersed in graphite powder makes Al and TiO2 reaction to form Al2O3+Al3Ti/Al composite at 700℃. The reaction can proceed continuously without breaking result from surface oxide film covered with aluminum powders.