LAUSR

Abstract The reaction behavior of porous silicon nitride (Si 3 N 4 ) ceramics at initial stage when exposed to water vapor ranging from 5 to 20 vol% at 1200 °C was investigated using online thermogravimetric (TG) method. The effect of water vapor on the surface morphology and corrosion interface of porous Si 3 N 4 ceramics was characterized using scanning electron microscopy (SEM). The results show that water vapor can aggravate the reaction and the reaction rate accelerates with the water vapor content increasing. As for the morphological evolution, water vapor promotes the formation of interconnected pores, which is possibly caused by the breakage of amorphous SiO 2 by inner massive gas product and gas releasing through crystalline SiO 2 . Based on these, a gas-solid model is adopted to describe the effect of different water vapor partial pressure on the reaction kinetics and obtains a good agreement.