黃坤祥2006-07-252018-06-282006-07-252018-06-282002http://ntur.lib.ntu.edu.tw//handle/246246/12420儘管降低高熔點金屬(鎢、鉬等)之燒結溫度的活化燒結方法早在1960 年代就被發現，但對於活化燒結的機構今仍存在許多疑問。本實驗在鉬中加入微量的鎳，利用熱膨脹儀、歐傑電子能譜儀及高解析穿透式電子顯微鏡等儀器的分析，並加上擴散偶的實驗來更深入探討鉬之活化燒結現象。另外除了研究鉬之活化燒結外，本研究也對鎢加鎳之活化燒結作初步研究，目的在瞭解更為完整的高熔點金屬之活化燒結現象。實驗結果發現，鉬在活化燒結時鎳會在鉬粉表面擴散並與鉬反應形成一層厚度約2nm 的δ-NiMo 介金屬相，此相為一硬且脆的材料，因而造成沿晶的脆性破裂。另外，由於鉬在此相中之擴散係數極快，因此鉬可經由此介金屬層快速擴散至頸部來達到鉬在低溫的燒結緻密化。而在 對鎢的初步研究中，在鎢晶粒間會發現有團塊的富鎳相存在，此富鎳相之結構以及晶界上是否也有富鎳層或介金屬化合物則仍須進一步進行研究。Molybdenum and tungsten are known as refractory metals and need high sintering temperature to achieve high sintered densities. Previous literatures have shown that addition of a small amount of Ni can lower their sintering temperature, however, the sintering mechanism to explain the enhancement phenomenon is still not clear. The objective of this study was thus to investigate the cause of the activated sintering in Mo-Ni system in more detail. The dilatometer analysis in this study suggests that the solid-state activated sintering proceeds at the temperature below the peritetic point of 1362 ℃. No eutectic was formed at 1317 ℃ which suggests that no free nickel or nickel solution was present in the system. The field emission TEM and the scanning Auger analysis indicate that a ä-NiMo intermetallic film, about 2 nm thick, was present at the grain boundaries. This finding excludes the possibility that the activated sintering is caused by the amorphous layer at the grain boundaries. The experiment of the Mo/Ni-Mo diffusion couple shows that the diffusivity of Mo in the ä-NiMo layer is about 30,000 times of the self-diffusivity of Mo. This suggests that the thin ä-NiMo layer serves as a fast diffusion path and impart the activation effect for the sintering of Ni-doped molybdenum.application/pdf842731 bytesapplication/pdfzh-TW國立臺灣大學材料科學與工程學研究所活化燒結介金屬化合物擴散MolybdenumActivated sinteringδ-NiMo intermetallic compoundreporthttp://ntur.lib.ntu.edu.tw/bitstream/246246/12420/1/902216E002042.pdf