Mg-sialon/MgO复合材料中Mg-sialon片晶的形成和表征

Formation and characterization of Mg-sialon platelet grain in Mg-sialon/MgO composites

为研制新型镁质耐火材料,采用金属铝粉、硅粉和电熔镁砂细粉为原料,通过XRD、SEM及能谱分析(EDS)等检测手段,分别对在氧化性条件、还原性条件和氮气条件下经1 350℃和1 550℃保温2h烧后的MgO、Al和Si原料中生成的Mg-sialon多形体进行研究,并结合热力学分析解释在各气氛条件下煅烧时材料中Mg-sialon多形体的形成机制。实验结果表明,在三种气氛条件下烧成时,MgO、Al和Si原料中的Al和Si主要通过气-固/液反应原位生成Al_2O_3、AlN和SiO_2,这些生成物与原料中的MgO相互固溶形成Mg-sialon多形体。三种气氛条件下烧后Mg-sialon/MgO试样中生成的Mg-sialon多形体形貌均为板片状,生成位置分别为氧化性条件下烧后试样的封闭气孔中、还原性条件下烧后试样金属相熔融反应后形成的孔洞中和氮气条件下烧后的整个试样中。

In order to develop new type magnesia refractories,aluminum powder,silicon powder and fused magnesia powder were used as the raw matters,the polytypic Mg-sialon phase forming in the composite material of MgO,Al and Si sintered at 1350℃and 1550℃in oxidizing,reducing and nitrogen atmosphere were characterized by XRD,SEM and energy dispersion spectrum（EDS）respectively,and the formation mechanism of polytypic Mg-sialon phase were explained by thermodynamic analysis at the same time.The experiment result shows that after sintering in both oxidizing,reducing or nitrogen atmosphere,Al and Si in sintered composites mainly translate into Al2O3,AlN and SiO2 by gas-solid/liquid reaction,and then react with MgO to form polytypic Mg-sialon phase.The polytypic Mg-sialon phase in-situ synthesized in Mg-sialon/MgO composite of MgO,Al and Si sintered in three different atmospheres all show plate-like shape,and it is mainly forms in the closed pores of the specimen sintered in oxidizing atmosphere,holes left behind by the molten metal in the specimen sintered in reducing atmosphere and whole area of the specimen sintered in nitrogen atmosphere.