Electron Microscopy Study On Sodiumm Salt Corrosion of Sic
Sun Jing (Shanghai Institute of Ceramics,Chinese Academy of Sciences) Hu Rongming (Shanghai Institute of Testing Technology) N.J.Tighe (Microphase System Corporation,Frederick,U.S.A.)
Corrosion reactins on SiC ceramics under molten sodium carbonate have been studied by scanning electron mi-croscope and analytical electron microscope. The experimental results show that the corrosion reactions take place first in the graphite inclusions at triple junctions. The structural characteristic of the corrosion reaction under sodi-um carbonate shows that it is a kind of pin corrosion generally located at the grain boundaries or the particles which have been corroded away. Besides glassy sodium silicate other corrosion products including crystalline sodium silica-te, amorphous and crystallie silica and silicon monoxide have been found under the electron microscopy observation. Reaction steps of sodium carbonate to SiC at high temperature have been deduced according to the experimental re-sults. The method of preparing TEM samples of SiC with glassy corrosion products is described.