HIGH-RESOLUTION ELECTRON-MICROSCOPY CHARACTERIZATION OF PARTIALLY CRYSTALLIZED FE78SI12B10 ALLOY AS A CATALYST

As a catalyst, partially crystallized Fe78Si12B10 alloy shows a three times higher activity than totally crystallized Fe78Si12B10 in the hyd rogenation of CO. High-resolution electron microscopy (HREM) reveals t hat the catalyst contains a great number of minute (less than 1 0 nm), highly dispersed alpha-Fe particles which act as the major active com ponent. Many tiny B and Si oxide clusters also exist in the amorphous matrix. After being rinsed by a NaOH solution, the catalyst exhibits a decreasing selectivity to methane due to the dissolution or aggregati on of B and Si species. After reaction, the sizes of the active partic les increase and an overlayer of B or Si species is found over the sur face of some alpha-Fe particles. This coverage is thought to be the pr imary origin of the deactivation of the catalyst.