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硅粉常壓直接氮化過程的非催化氣固反應模型

Noncatalytic gas-solid reaction model for directly nitridizing silicon powder under atmospheric pressure

  • 摘要: 以平均粒徑2.2μm、純度99.99%的硅粉為原料,采用純度99.993%的高純氮氣作為反應氣體,在1350和1400℃下進行了氮化時間為10~30 min的氮化實驗,得出了不同溫度下硅粉轉化率隨反應時間的變化關系.將硅氮反應看成非催化氣固反應,建立了硅顆粒氮化動力學模型.通過對實驗數據的擬合,得出兩個模型參數:硅氮反應速率常數和氮氣在產物層中的擴散系數.假定反應速率常數和擴散系數均滿足阿倫尼烏斯公式,求得化學反應激活能和指前因子分別為2.71×104J·mol-1和3.07×10-5m·s-1,擴散激活能和指前因子分別為1.06×105J·mol-1和1.12×10-9m2·s-1.利用本文得出的氮化動力學模型對各溫度下不同粒徑硅粉的轉化曲線進行了預測,預測曲線與文獻中的實驗數據在趨勢上吻合較好.

     

    Abstract: In order to study the nitridation kinetics of silicon powder under atmospheric pressure, a set of nitrida- tion experiments were performed at 1350 and 1400 ℃ for 10 to 30 rain. Silicon powder of 2.2 ~m in average diameter and 99.99% in purity was adopted as the experimental materials, and nitrogen of 99.993% in purity was used as the reaction gas. At different temperatures, the conversion rate of silicon is obtained as a function of reaction time. Based on the noncatalytic gas-solid reaction model, a dynamic model of silicon nitridation under atmospheric pressure is introduced, which includes two key model parameters: reaction rate constant of silicon nitridation and diffusion coefficient of nitro- gen in silicon nitride, These model parameters are obtained by fitting the experimental data under different conditions. Assuming that reaction rate constant and the diffusion coefficient can both be expressed as the Arrhenius style, the activation energy and pre-exponential factor of the reaction are calculated as 2.71× 104 J·mol-1 and 3.07× 10-5 m·s-1, and the activation energy and pre-exponential factor of diffusion are calculated as 1.06×105 J·mol-1 and 1.12×10-9 m2·s-1, respectively. Then a series of conversion curves are predicted at different temperatures and powder sizes. On the trend, the predicted curves are in good agreement with experimental data in literatures.

     

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