盐浴法合成Cr_(2)AlC陶瓷粉体工艺研究

Research on Synthesis Process of Cr_(2)AlC Powders by Salt Bath Method

Cr_(2)AlC陶瓷因其高电导和良好的高温抗氧化能力可应用于高温微波吸收领域而备受关注。本文以Cr_(3)C_(2)粉、Al粉、Cr粉为原料,在BaCl_(2)、KCl和NaCl混合盐浴中合成了Cr_(2)AlC陶瓷粉体,并借助X射线衍射技术研究了原料组成、合成温度以及保温时间对合成粉体物相的影响。结果表明:铝含量的不足,会引起反应不充分,合成粉体中残留较多的Cr_(3)C_(2);当铝过量达到30wt%,原料中剩余的Al会氧化成Al_(2)O_(3);随着合成温度的升高,合成粉体中Al_(2)O_(3)和Cr_(3)C_(2)相的量减少,但合成温度过高,合成粉体中会出现Cr_(7)C_(3)相;保温时间不足,合成粉体中有较多的Al_(2)O_(3)和Cr_(3)C_(2)相,保温时间过长,合成粉体中也会出现了Cr_(7)C_(3)相。当铝过量20 at%,合成温度为970℃,保温2 h时,可批次稳定地得到高纯度Cr_(2)AlC陶瓷粉体。

Cr_(2)AlC is widely used in the field of high—temperature microwave absorption due to high electrical conductivity and good high-temperature oxidation resistance.In this paper,Cr_(2)AlC ceramic powder is synthesized in a mixed salt bath of BaCl_(2),KCl and NaCl using Cr_(3)C_(2),Al,and Cr powders as raw materials.The research results show that insufficient Al content will cause incomplete synthesis reaction,resulting in Cr_(3)C_(2) remaining in the synthetic powder.When the Al excess reaches 30 wt%,the remaining Al will be oxidized to Al_(2)O_(3).Al_(2)O_(3) and Cr_(3)C_(2) in the synthetic powder decreases as the synthesis temperature increasing.However,high synthesis temperature will cause Cr_(7)C_(3) to appear in the powder.Insufficient holding time will cause more Al_(2)O_(3) and Cr_(3)C_(2) in the synthetic powder.If the holding time is too long,Cr_(7)C_(3) will also appear in the synthetic powder.The best process for stable synthesis of high-purity Cr_(2)AlC ceramic powder:Al excess 20 at%,holding time 2 h at 970℃.