China's Refractories

Abstract: Active lime was used to produce Ca(OH)2 fine powder. And then Ca(OH)₂ fine powder with analytically pure CeO₂ fine powder (0, 0.2%, 0.4%, 0.6%, 0.8% and 1.0% by mass, respectively) were mixed via wet mixing. After drying and ball milling, the specimens were pressed and fired at 1 450 ℃, 1 500 ℃, 1 550 ℃, 1 600 ℃and 1 650 ℃, respectively. The hydration resistance of the specimens was evaluated by measuring the mass gain after soaking the specimens in a chamber kept at 20 ℃ and 90% relative humidity. The influences of CeO₂ and calcination temperature on the hydration resistance of CaO aggregates were investigated by determination of bulk density, apparent porosity, and XRD, SEM and EDS analysis. The results show that: (1)the sintering of CaO aggregates is promoted by CeO₂ addition and the hydration resistance of CaO aggregates is improved; (2) CeO₂ mainly locates in CaO grain boundary, some CeO₂ is solved in the CaO grains which improves CaO sintering; (3) the appropriate calcination temperature is 1 550 ℃. When the calcination temperature is below 1 550 ℃, the specimens are sintered inadequately. The density and hydration resistance of CaO aggregates are nearly stable when the calcination temperature is above 1 550 ℃.

Key words: calcia aggregate, cerium oxide, calcination temperature, hydration resistance