Al_4SiC_4陶瓷的高温氧化行为

High-Temperature Oxidation Behavior of Al_4SiC_4 Ceramics

从高温氧化动力学、组织的微观进化及高温氧化机理3部分对Al4SiC4陶瓷在1200℃-1700℃的高温氧化行为进行了系统的研究。研究结果表明，Al4SiC4陶瓷具有优异的高温抗氧化性能。氧化动力学符合抛物线规律，其氧化活化能经计算为220kJ／mol。XRD及SEM研究结果表明：Al4SiC4陶瓷在1200～1500℃的氧化表面物相为Al2O3和铝硅酸盐玻璃；而高温氧化表面（1600℃～1700℃）的物相由Al2O3，莫来石和铝硅酸盐玻璃构成。由氧化试样横截面观察得知氧化层按其特征的不同分为3个部分：具有较多细小尺寸孔洞的反应层；具有较大尺寸孔洞的中间层和致密的外氧化层。在高温抗氧化机理部分中首先从热力学上计算了氧化过程中各反应的生成焓和吉布斯自由能；然后对高温氧化过程进行了推理和分析；最后根据上述试验及推理结果建立了Al4SiC4陶瓷的高温抗氧化模型。

The oxidation behaviors of Al4SiC4 ceramics at 1200℃-1700℃ were investigated from three parts： the oxidation kinetics, the microstructure observation, the oxidation mechanism at high temperature, respectively. The results of the first part show that the Al4SiC4 ceramic has the excellent anti-oxidation property at high temperature, and the kinetics of oxidation obeys the parabolic law with an activation energy of 220 kJ.mol^-1. The results of XRD and SEM indicated that the oxide phase composition of the oxidation surface is composed of Al2O3 and aluminosilicate glass for the lower oxidation temperature （≤1500℃）, or Al2O3, mullite and aluminosilicate glass for the higher oxidation temperature （≥1600℃）. The oxide scales consist of an outer oxide layer, a middle oxide layer and a reaction layer over the temperature ranges. A number of pores exist in the middle oxide scale. The enthalpy and the Gibbs free energy of the possible reaction during the oxidation process were calculated. The next part is to infer and analysis the elevated oxidation process and established the elevated oxidation model of Al4SiC4 ceramics.