铁酸钙与TiO_(2)的扩散反应特征

Diffusion Reaction Characteristics of Calcium Ferrite and TiO_(2)

钒钛磁铁矿烧结过程中,TiO_(2)会与Fe_(2)O_(3)竞争CaO,抑制铁酸钙(C_(x)F)的形成,进而影响烧结矿品质.通过制备C_(x)F/TiO_(2)扩散偶的方法,直观地研究CaO-Fe_(2)O_(3)-TiO_(2)体系的扩散反应.运用电子探针和X射线衍射分析仪等手段对反应界面不同位置处的生成物进行分析和表征,研究了在扩散温度为900~1050℃,时间为1~4 h的条件下C_(x)F与TiO_(2)界面的反应特征;分析了温度及时间对生成相的种类、分布及形貌特征的影响.结果表明,从C_(x)F一侧到TiO_(2)一侧,主要的物相有C_(x)F,CF,Fe_(2)O_(3),CaTiO_(3),TiO_(2),其中钙钛矿(CaTiO_(3))是主要的生成产物.随温度从900℃升高至1050℃,CaTiO_(3)的厚度从8.1μm增大至90.2μm;随时间从1 h延长至4 h,CaTiO_(3)的厚度从47.4μm增大至121.4μm.同时,CaTiO_(3)的扩散厚度与扩散时间的平方根呈良好的线性关系,这表明CaTiO_(3)的生成受扩散过程控制.进一步地,使用空位扩散机理解释了CaTiO_(3)在CaO-Fe_(2)O_(3)-TiO_(2)体系的生成过程.

During sintering the vanadium titanomagnetite,TiO_(2)competes with Fe2O3 for CaO,which inhibits the formation of calcium ferrite(C_(x)F)and affects the sinter quality.In this paper,the diffusion reaction of CaO-Fe_(2)O_(3)-TiO_(2)system is intuitively studied by preparing C_(x)F/TiO_(2)diffusion couple.Electron probe and X-ray diffractometer are used to analyze and characterize the products at different positions of the reaction interface.The reaction characteristics of C_(x)F/TiO_(2)interface are studied at the diffusion temperature of 900~1050℃and the time of 1~4 h.The effects of temperature and time on the types,distribution and morphology of the generated phases are discussed.The results show that the main phases are C_(x)F,CaO·Fe_(2)O_(3)(CF),Fe_(2)O_(3),CaTiO_(3)and TiO_(2)from the C_(x)F-to TiO_(2)-layer,among which perovskite(CaTiO3)is the main product.The thickness of CaTiO_(3)increases from 8.1μm to 90.2μm with the temperature increasing from 900℃to 1050℃;it increases from 47.4μm to 121.4μm with the time increasing from 1 h to 4 h.Meanwhile,the diffusion thickness of CaTiO_(3)has a good linear relationship with the square root of diffusion time,which indicates that the formation of CaTiO_(3)is controlled by diffusion process.Furthermore,the formation process of CaTiO_(3)in CaO-Fe_(2)O_(3)-TiO_(2)system is explained by vacancy-mediated diffusion mechanism.