Study of the thermal transformations of Co- and Fe-exchanged zeolites A and X by “in situ” XRD under reducing atmosphere
Abstract “In situ” high temperature X-ray diffraction under reducing atmosphere is used for the first time to study the thermal stability and transformations of Co- and Fe-exchanged A and X zeolites. TG-DTA and “ex situ” XRD characterization were also carried out. The temperature of incipient crystallization of metallic phase was found to be 700 °C in Fe-zeolites and 800 °C in Co-zeolites. Moreover, ex situ X-ray experiments, after thermal treatment both under inert and reducing atmosphere, revealed the formation of ceramic phases upon the thermal collapse of the zeolitic framework. Metal nanoparticles were obtained by reduction and the size of metal clusters was found to range between 24 and 40 nm.
1. ::: ::: In the course of the application of the enamel coating to 08sp steel, a diffusion redistribution of elements takes place accompanied by the formation in the metal surface layers of a diffusion zone which lost some manganese and gained silicon, boron, and titanium. ::: ::: ::: ::: ::: 2. ::: ::: The diffusion processes at the metal-enamel interface are accompanied by a change in the mechanical properties of surface layers of steel which can considerably affect its strength. ::: ::: ::: ::: ::: 3. ::: ::: The mechanical properties of surface layers of steel depend on the number of enamel firing cycles.