粒径与加热速度对金属Al氮化过程的影响

在氮气流量为55 ml/min条件下,分别以5,10,15 ℃/min的加热速率对不同粒径(d_(50)为62,29,7.5μm)的金属Al粉进行了TG-DTA分析和反应活化能的研究.结果表明:在相同的实验条件下,随Al粉粒径的减小和加热速率的增大,生成AlN的反应活化能降低;在N_2流量55 ml/min和加热速率5 ℃/min条件下,d_(50)= 29 μm和d_(50) =7.5 μm Al粉生成AlN的主放热峰温比d_(50) =62 μm Al粉的分别可降低140和250 ℃.在N_2流量55 ml/min条件下,d_(50)= 7.5 μm Al粉以10和15 ℃/min为加热条件的氮化反应速率比5 ℃/min的提高0.9和1.7倍.Al粉反应生成AlN的全过程,主要由界面反应和内扩散反应交替完成,且整个反应过程应为扩散机制控制.

Effect of Grain Size and Heating Rate on Nitridation Reaction of Metallic Aluminium

In the case of nitrogen flow of 55 ml/min, the TG-DTA and reaction activation energy of powdered aluminium with various grain sizes (d_(50)=62 μm, 29 μm, and 7.5 μm) and at heating rate of 5 ℃/min, 10 ℃/min and 15 ℃/min, respectively were studied. The result of the experiment reveal that, under the same condition, the activation energy of nitridation decreases with reduction of grain size and increase of heating rate, and the main exothermic peaks to form AlN from powdered Al with d_(50)=29 μm and d_(50)=7.5 μm can be lower than that with d_(50)=62 μm by 140 ℃ and 250 ℃ when nitrogen flow is 55 ml/min and heating rate is 5 ℃/min. The nitridation reaction rates with heating rate at 10 ℃/min and 15 ℃/min get higher than that at 5 ℃/min by 0.9 and 1.7 times under the condition of N_2 flow of 55 ml/min and grain size of Al d_(50)=7.5 ìm. The process to form AlN from powdered Al alternates between interfacial reaction and internal diffusion reaction, and it is controlled by the latter.