利用重力计, 比重仪, SEM, XRD, 碳素分析仪, XFS和氧氮分析仪检测了不同加热条件下碳热还原氮化法合成镁阿隆(MgAlON)的密度、微观结构、相组成以及Mg, Al, O, N和C含量, 讨论了碳热还原氮化法合成MgAlON的机理. 结果表明, 加热温度为1100℃时, 原料中所有的MgO反应生成镁铝尖晶石(MgAl2O4ss); 当加热温度高于1300℃时, 发生碳热还原氮化反应, N固溶于MgAl2O4ss生成MgAlON; 由于碳热还原氮化反应不断消耗Al2O3, 加热温度为1600℃时试样中Al2O3大颗粒的尺寸较加热温度为1500℃时的小; 随着石墨和Al2O3在反应过程被完全消耗, 在1650℃下加热获得了单相MgAlON. 另外, 碳热还原氮化反应中N原子向尖晶石结构MgAl2O4ss中固溶时导致晶格畸变而使原子间隙扩大, 从而Al在MgAlON的固溶量高于其在MgAl2O4ss中的固溶量. 由于碳热还原氮化反应过程产生气体及高温下Mg蒸汽分压较高, 即使加热温度提高至1800℃, 试样中仍然存在大量密闭气孔.
Gravimeter, pycnometer, SEM, XRD, carbon analyzer, XFS and oxygen-nitrogen analyzer were utilized to study the production of magnesium aluminium oxynitride (MgAlON) by carbothermal reduction and nitridation (CRN) under different temperatures and its formation mechanism was also discussed in the present paper. The results show that all of the raw MgO are completely consumed to form MgAl2O4ss at 1100℃. At sintered temperatures higher than 1300℃, the CRN reaction is taken place, and MgAlON is formed by solid solving N into MgAl2O4ss. The consumption of Al2O3 during CRN reaction causes the particle size of Al2O3 in the sample heated at 1600℃ to be smaller than that heated at 1500℃. Finally, the monophase MgAlON is obtained at 1650℃ when all the graphite and Al2O3 have been consumed. Moreover, because of the solid solution of N into MgAl2O4ss, the amount of defects in the lattice of MgAlON is raised leading to the solubility of Al in MgAlON being higher than that in MgAl2O4ss. Lots of closed pores are remained in grains even if the heating temperature has been raised to 1800℃ due to higher volatile Mg partial pressure and the gas phase product of CRN reaction at high temperature.
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