Abstract
Mechanical properties and chemical corrosion behavior of two kinds of polycrystalline MgO normally sintered without additives (MG-S) and with SiO2, CaO additives (MG-12) were studied. Effective fracture energy (γeff) measured by "Work of Fracture" technique increased from about 30 J/m2 at room temperature to about 60 J/m2 at 800°C for both MG-S and MG-12, and the values were nearly constant of 60J/m2 Up to 1450°C for MG-S. γeff decreased gradually, however, with increasing temperature to about 30 J/m2 at 1450°C for MG-12 showing the fractured surface change from transgranular to intergranular one, and also large internal friction with relaxation of Young's modulus measured by sonic resonance technique was observed at 900°C, which must have resulted from an elasticity of grain boundary glassy phase. On the other hand, MG-12 showed poor corrosion resistance as a result of static immersion test in K2CO3 molten salt. The microscopic observation after treatment at 1000°C showed the polycrystal affected at the grain boundary concentrically.
