氟化碳酸镧铈煅烧过程的相态结构和颗粒特征变化

Variation of Phase Structures and Particle Properties during The Calcination Process of Fluorinated Carbonate Lanthanum Cerium

以碳酸镧铈为原料,通过氟化和煅烧来制备含氟稀土抛光粉。采用XRD、TGA-DTA、SEM、激光粒度分布仪、比表面积仪对煅烧过程中的相态结构和颗粒特征进行了表征。结果表明,氟化碳酸镧铈在煅烧过程中经历了三个主要过程,包括脱水、碳酸盐分解成氧化物、从氧化镧铈中形成氟氧化镧铈。不同煅烧温度下制得样品的XRD和粒度分析结果证明中温(650℃)和高温(1000℃)煅烧产物的不同点在于氟氧化镧铈的形成与否和颗粒的形貌和团聚程度。随着煅烧温度的升高,颗粒团聚程度增加,并在1040℃出现急剧增加,而团聚粒子与分散粒子相比,团聚粒子中因为固溶了更多的镧而使其结晶度更低。增加分散颗粒的比例和煅烧温度可以提高氟氧化镧的形成比例,提高抛光效果。据此,提出了两阶段煅烧法用于提高合成抛光粉的抛光效果。采用该法制得的样品具有更高的抛光速率和较好的抛光质量。

Fluorine -doped rare earth polishing abrasive has been prepared from carbonate lanthanum cerium as raw ma- terial through fluoridation and calcination method. The phase structure and particle property of the polishing abrasive have been characterized employing a combination of techniques including X - ray diffraction （ XRD）, TGA - DTA, SEM, laser scattering particle size distribution analysis （LSPSDA） and specific surface area （SSA）. The results indicated that the calci- nation of carbonate lanthanum cerium involves in three important processes： dehydration, carbonate decomposition and oxyflu- oride formation. The different properties of the calcination products between medium （650 ℃ ） and high （ 1000 ℃ ） tempera- ture are mainly reflected in the oxyfluoride formation, particle morphology and aggregation, which can be confirmed by the re- suits of XRD and LSPSDA analysis. The particles aggregation increased obviously with the increase of the calcination tempera- ture. Especially, there is a dramatic increase of aggregation at 1040 ℃. Compared with the dispersive particles, aggregated particles possess lower crystallinity because more lanthanum had been doped. The proportion of oxyfluoride could be optimized by increasing the calcination temperature and the particle dispersion, which would improve the polishing effects. Therefore, a basic method of two - step calcination was employed to prepare high performance abrasives. It is found that the prepared abra- sives were well balanced for both the removal rate and the surface roughness.