本計畫探討超音速粒子對衝型乾式奈米研粉技術，以因應高純度粉體材料，超硬材料粉體之奈米化需求。本技術以超音速粒子對衝式噴嘴，將製程材料以高速氣流加速至超音速，利用超音速粒子對衝機制，提高其粉碎能量，一舉突破傳統機械式粉碎法能量上的限制，以產生超微粒的奈米粉末。此技術由於利用超音速粒子對衝機制，故製程中沒有機械轉動件，而且粉體粒子由高速氣流所推動，沒有機會接觸傳統奈米研磨機的刀片，可以避免奈米粉體在製程中的污染。本研究先以數值方法進行噴嘴及對衝流場模擬，然後進行超音速噴嘴流場測試，再以碳酸鈣粉末進行系統可行性測試。接著以甲殼素粉末進行參數測試，尋找系統最佳化的參數設定。最後根據參數實驗的結果進行碳化矽粉末之研粉實驗。實驗結果顯示，粉末經過一次對衝即可產生5%以上體積比率之細粉含量，具有顯著之粉末微小化效果，可以運用於特殊材料之微小化應用。當氣體操作壓力愈大，以甲殼素粉末為例，所產生的微粉末中，10μm以下的小粒徑比例逐漸遞增。當氣體壓力為2.0 kg/cm2時，小於10μm的粉末所占體積從原粉末的8.46%增加至12.9%，體積增加率為52.5%；而當氣體壓力進一步增加到4.0 kg/cm2時，小於10μm的粉末所占體積增加至18.0%，體積增加率為113%。以碳化矽粉末為例，原粉末中粒徑皆大於4μm，當對衝氣體壓力為2.0 kg/cm2時，微粉末中開始出現小於4μm的粉末，其所占體積百分比為2.34%；而當氣體壓力增加到4.0 kg/cm2時，小於4μm的粉末所占體積百分比提高至5.04%。顯示經過超音速粒子對衝型乾式奈米研粉系統操作之後，粉末粒子互相碰撞會造成粒子的顯著破裂。將來若設計成連續式操作之量產型系統，使粒子能夠在腔體內連續重複對衝，可以產生更微小化的奈米粉末。

This research develops a supersonic nozzle for the pulverization on the powders with high purity and high hardness. Opposed jet mills offer various advantages such as the ability to produce particles with narrow size distribution, and less contaminations because of autogenous grinding. Numerical simulation of the opposed jet was performed in order to characterize the supersonic nozzle and system. The performance of the supersonic nozzle was then analyzed with compressed gas flow without particle loading. Feasibility analysis of the jet mill system was performed by using calcium carbonate (CaCO3) powder. Finally, optimization on system performance was performed on chitosan and silicon carbide (SiC) particles. Results shows that the differential volume percentage of the fine powder is significantly increased over five percent in one impinging process without particle reflow. It indicates this system can be employed to produce ultra-fine powder with high purity. The differential volume of smaller chitosan particles（<10μm） is enhanced as the operating gas pressure increased. The differential volume of the chitosan particles less than 10μm is increased from 8.46% to 12.9%（about 52.5% enhancement in differential volume percentage）with operating gas pressure 2.0 kg/cm2. As operating gas pressure being increased to 4.0 kg/cm2, the differential volume of the chitosan particles less than 10μm is increased to 18.0%（about 113% enhancement in differential volume percentage）.Furthermore, we performed experiment on silicon carbide powders, which have no particles smaller than 4μm before milling. Results show that the differential volume of silicon carbide powders less than 4μm increased from 0% to 2.34% and 0% to 5.04% with operating gas pressure 2.0 kg/cm2 and 4.0 kg/cm2, respectively. The production rate of the fine particles can be further increased as the system is designed for the continuous operation with reflow of the particles.

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