Abstract
MgO-CaO refractories were prepared using analytical reagent chemicals of Ca(OH)2and Mg(OH)2as starting materials and CeO2as dopant, then sintered at 1650°C for 3 h. The effect of CeO2powders on the defect of MgO-CaO refractories was investigated. The sample characterizations were analyzed by the techniques of XRD and SEM. According to the results, with the addition of CeO2, the lattice constant of CaO increased, and the bulk density of the samples increased while apparent porosity decreased. The densification of MgO-CaO refractories was promoted obviously. In the sintering process, MgO grains grew faster than CaO, pores at the MgO-CaO grain boundaries decreased while pores in the MgO grains increased gradually, and no pores were observed in the CaO grains. The nature of the CeO2promoting densification lies in the substitution and solution with CaO. Ce4+approaches into CaO lattices, which enlarges the vacancy concentration of Ca2+and accelerates the diffusion of Ca2+.
Highlights
MgO-CaO refractories have been widely used in metallurgy industry [1] and cement rotary kilns [2] owing to their excellent properties such as high melting points, excellent thermal shock resistance, and slag corrosion resistance [3]
MgO-CaO refractories are beneficial to removing inclusions from molten steels; they have been considered to be one of the effective refractory types for processing clean steel products [5, 6]
The application of MgO-CaO refractories has been limited by their poor hydration resistance [9, 10]
Summary
MgO-CaO refractories have been widely used in metallurgy industry [1] and cement rotary kilns [2] owing to their excellent properties such as high melting points, excellent thermal shock resistance, and slag corrosion resistance [3]. They have been considered as one type of chromefree refractories that are suitable for substituting the MgOCr2O3 refractories [4]. The hydration resistance of free lime materials can be improved by treating them in a CO2 atmosphere [11] which leads to the formation of a dense maskant on the surface of CaO. The effect of CeO2 addition on the sintering and microstructure of the MgO-CaO refractories are investigated with an aim to delineate the effects of the lattice defects on improving the sintering and hydration resistance of MgO-CaO refractories
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