扫描俄歇微探针(SAM)对掺镧氨合成催化剂表面特征研究

STUDY OF THE SURFACE CHARACTERIZATION OF LANTHANUM DOPED AMMANIA SYNTHESIS CATALYST BY SAM

本文利用PHI595型扫描俄歇微探针(SAM)详细研究了新近研制的一种高活性掺镧氨合成催化剂的表面特征,由二次电子分布(SED)图,俄歇电子像,剖面线扫描以及深度分析的结果表明,催化剂是由大小不同的卵石形晶体和晶粒碎块堆积而成,表面形态凸凹不平,元素镧主要分布在催化剂球内部晶粒的表层,其厚度约800—1000A,镧和铁的分布相互制约,在镧分布浓度大的区域,无铁或浓度较小:反之铁浓度大的区域镧较少或无。在球表面还有少量钾,几乎未发现有铁和钙的存在.在晶粒的断裂处仅有铁和氧,说明助剂元素钾、钙和镧没有进入Fe_3O_4晶体内部.

This treatise presencs a d erailed study of the surface characterization of a newly developed lanthanum doped ammonia synthesis catalyst of high activity with the help of PHI 595 SAM. The results of the secondary electron distribution image, the auger electron image, profile scanning and depth analysis show that the catalyst is made up of pebbleshaped crystals of various sizes and crstal fragments which accumulate together. The surface is uneven and element lanthanum is mainly distributed on the catalyst surface and the surace layer of the crystal grains in the catalyst balls. The layer is approximately 800-1000A. the distributions of lanthanum and that of iron constrain each other. At areas where lanthanum concentraes greatly iron distribution is spares or none at all. And vice versa. On the catalyst ball surface, small amount of potassium can be found, but iron and calcium can hardly be found. On the fracture surface only iron and oxygen can be found. This indicates that cocatalyst potsium, calcium and lanthanum do not enter the inner part of the crystal grains of magneic iron oxides(Fe_3O_4)