REACTION BEHAVIOR OF MAGNESIUM ORTHOTITANATE AND CALCIUM TITANATE WITH COMPOUNDS OF PORTLAND CEMENT AND THEIR USE IN A CHROME-FREE REFRACTORY

摘要

In this work magnesium orthotitanate (Mg_2TiO_4) and calcium titanate (CaTiO_3) were submitted individually to a reaction with CaO, Ca_2SiO_4, Ca_3SiO_5, Ca_3Al_2O_6 and Ca_4Al_2Fe_2O_(10) in an electric furnace at 1450℃ for 2.5 hours. The powder X-ray diffraction analysis revealed the formation of calcium titanate during the reaction of magnesium orthotitanate with most of the Portland cement phases. By other hand, calcium titanate was not affected when in contact with Portland cement phases. These results opened a great possibility in exploring both phases in a new chrome-free refractory. In a second step of this research, a magnesia-magnesium orthotitanate-calcium titanate refractory brick was produced and compared with a standard magnesia-spinel refractory brick. Both formulations were evaluated in thermal spalling resistance test, apparent porosity, bulk density, true specific gravity, water absorption, total porosity, chemical analysis, elastic modulus, thermal expansion coefficient and coating adherence test associated with scanning electronic microscopy. Refractories of magnesia-magnesium orthotitanate-calcium titanate system presented excellent coat adherence result maintaining the same level of thermal spalling resistance when compared with a standard magnesia-spinel refractory.