本研究以氧化鐵粉為添加劑，並以氮氣作為反應氣體，進行二氧化矽碳熱還原反應，探討氧化鐵粉添加劑對反應後產物的轉化率、形態結構及反應速率等影響。實驗中使用直立式管狀高溫爐系統，由氮化反應前後的重量變化求得二氧化矽的轉化率，並探討各項操作變數對氮化反應的影響。 本實驗主要探討的操作變數包括：氮氣流率、氧化鐵粉的添加量、C/SiO2莫耳數比、樣品載量及反應溫度等。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)、比表面積測定儀(BET)、X-射線繞射儀(XRD)、掃描式電子顯微鏡(SEM)等來印證各種實驗結果。 實驗結果顯示，增大氮氣流率可增加二氧化矽的轉化率，當流率大於500 ml/min時，轉化率的影響就不太明顯。添加氧化鐵粉可以增加二氧化矽的轉化率。當C/SiO2莫耳數比大於5時，轉化率影響也不大。溫度升高則可以促進反應速率。整個氮化反應主要是以氣/固反應為主，添加氧化鐵粉後氮化反應主要產物為纖維狀碳化矽，並推測添加氧化鐵粉後造成Fe-Si液態合金的形成是碳化矽成長的重要機制。在化學反應控制區內，添加1wt%的氧化鐵粉，C/SiO2莫耳數比為6時，反應活化能為123.54kJ/mol。 The carbothermal reduction and nitridation of silicon dioxide with iron oxide powder addition was investigated by weight change measurement. The aim of this study is to know the effect of different operating variables on the degree of conversion of silicon oxide. In this study, the main operating variables have been discussed included: nitrogen flow rate, amount of iron oxide powder added in the reactant, silica /graphite molar ratio, sample weight, and reaction temperature. The analysis of this experiment is conducted by 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 silicon dioxide is increased with an increasing nitrogen flow rate, when the gas flow exceeded 500ml/min, the effect is not appreciable. The conversion of silicon dioxide is increased with an increasing amount of iron oxide powder added in the reactant. An excess of graphite is required to promote the degree of conversion of silicon oxide, however, the effect is not appreciable, when the molar ratio is above 5. Moreover, the higher the reaction temperature the faster the reaction rate. The reaction product is fibrous shape β- SiC with iron oxide addition. We conjectured that the formation of liquid Fe-Si alloy is an important way for β- SiC growth. In the chemical reaction controlled region, the activation energy of the reaction is 123.54 kJ /mol when iron oxide powder added is 1wt% and C/SiO2 molar ratio is
