炼镁用FeSi75高温空气气氛中氧化行为热力学分析

Thermodynamic Analysis of FeSi75 Oxidation Behavior in Magnesium Reduction at High Temperature Air Atmosphere

为探明硅热法炼镁过程中硅铁非正常损耗的本质,采用光学显微镜(OM)、扫描电子显微镜(SEM)、热重分析仪(TGA)、X-射线衍射仪(XRD)等研究了空气气氛中炼镁用FeSi75在镁还原温度范围内的氧化行为,基于热力学角度分析了25~1 200℃温度范围内Si-N-O系存在的化学反应及对应的ΔrGθ-T关系,判断还原温度条件下Si-N-O系凝聚相的稳定存在的温度区间,探索不同lg(PO2/Pθ)和lg(PN2/Pθ)组合下硅的存在形式。结果表明:FeSi75粉末中的单质硅和空气中的氧发生反应生成SiO_2,合金相FeSi75和空气中氧之间几乎不发生反应。在25~1 200℃温度范围内,随温度的升高,FeSi75和空气中的氧发生反应生成SiO_2,导致试样重量增加;在800~1 200℃温度区间,增重速率大,当温度升至1 200℃时,试样比初始状态增重5.49%。

In order to find out the nature of abnonnal loss of FeSi75 powder, utilized in magnesium reduction, its abnormal waste in high temperature air atmosphere has been studied by using optical microscopy （ OM）, scanning electron microscopy （ SEM ） , thermogravimetric analysis （TGA） and X - ray diffraction （ XRD ）, Furthermore,the thermodynamic analysis and experiments were adopted. The possible chemical reactions and their - T were analyzed in the magnesium reduction temperature range （from 25 to 1 200 ） , thenphase stability of Si - N - 0 system（1 200 ℃ ） was obtained,to estimate the existence form of Si under differ-ent combination of oxygen tension and nitrogen tension. The results are as follows：the elementfd silicon in the FeSi75 powder and oxygen in the air react to generate SiO2, while the alloy FeSi75 and oxygen in the air al-most no reaction. In the temperature range of 25 ~ 1 200 ℃ ,with the increase of temperature,FeSi75 reacts with oxygen in the air to produce Si02 ,which leads to the increase of the sample weight. In the temperature range of 800 ~ 1 200 ℃, the weight gain rate is high, and when the temperature rises to 1 200 ℃ , the sample increases by 5.49% over the initial state.