摘 要 本研究以矽粉為添加劑，在氮氣環境下進行熱解後稻殼灰分的碳熱還原反應，探討矽粉添加劑對反應產物的形態、反應速率等影響，並深入研究矽粉添加劑於反應中所扮演的角色。研究中使用直立式管狀高溫爐系統，由反應前後的重量變化求得稻殼灰分的轉化率，以探討各項操作變數對反應的影響。 而在操作變數方面包括：氮氣流率、矽粉添加量、樣品載量、顆粒大小及反應溫度等。研究中並做各種物性分析如：感應耦合電漿質譜分析儀 (ICP-MS)、元素分析儀 (EA)、比表面積測定儀 (BET)、X-射線繞射儀 (XRD)、掃描式電子顯微鏡 (LV-SEM) 等來提供各項實驗結果的佐證。 實驗結果顯示，稻殼經由水洗、酸洗及熱解前處理後，由EA分析得C/SiO2莫耳數比為3.72 。BET特性分析得其比表面積為235m2/g，並由等溫曲線中，了解稻殼灰分為一種多孔性物質的毛細管凝結現象。產物方面，利用XRD分析得知反應產物為氮化矽，且隨添加量的增加，特徵峰強度更強。增大氮氣流率下，可增加稻殼灰分的轉化率，但當氮氣流率大於400 ml/min時，對於轉化率影響較不明顯。添加矽粉後可以增加稻殼灰分的轉化率，添加1wt %以上則轉化率增加幅度變小。減小稻殼灰分粉粒直徑可增加其轉化率。反應溫度對提高轉化率影響甚為顯著。另由LV-SEM顯示產物氮化矽為鬚晶狀結構，且隨添加量的增加產物分布更為均勻。在化學反應控制區內，反應的活化能為478.5 kJ / mol。 Abstract The carbothermal reduction and nitridation of rice husk ash with silicon powder addition was investigated by weight change measurement. The reaction were carried out in a vertical reaction tube heated by a tubular furnace. In this study, the operating variables have been discussed included: nitrogen flow rate, amount of silicon powder addition in the reactant, grain size, sample weight and reaction temperature. The analysis of this experiment is conducted by element analysis (EA), inductively coupled plasma-mass spectrometer (ICP-MS), BET surface area, X-ray diffraction (XRD) and scanning electron microscope (SEM). The experimental results indicated that the conversion of rice husk ash is increased with an increasing nitrogen flow rate and the effect is not appreciable when the flow rate exceeds 400ml/min. The conversion of rice husk ash is increased with an increasing amount of silicon powder addition in the reactant. Reducing the grain size of rice husk would accelerate the reaction rate. Moreover, the reaction rate and the conversion of rice husk ash is significantly increased with higher reaction temperature. The reaction product is fibrous shape a-Si3N4 with silicon addition. In the chemical reaction controlled region, the activation energy of the reaction is 478.5 kJ/mol when silicon powder addition is 1wt %.
