Microsilica or MgO grain size: Which one mostly affects the in situ spinel refractory castable expansion?

Synthesis and hydration kinetics of calcium aluminate cement with micro MgAl2O4 spinels

“…At the same time, the decreased particles size of MgO would also benefit the formation of MA and prohibit CA 2 formation. This result is consistent with the reports of [8,9,12]. The Rietveld analysis by XRD showed that the composition of the CMA sample calcined at 1300 C and 1500 C was 24 wt% CA (JCPDS Nos.…”

“…However, the synthesized spinel typically leads to high cost and inhomogeneous distribution in the castables [8]. The in-situ formation of spinel often requires free MgO, which produces large volume expansions and thus unstable physical properties at elevated temperatures [8,9]. Therefore, in recent years, calcium aluminate cement with MgAl 2 O 4 spinel (CMA) has been developed.…”

Reasons for crack propagation and strength loss in refractory castables based on changes in their chemical compositions and micromorphologies with heating: special focus on the large blocks

“…It should be noted in connection with mechanical strength that, as reported by some authors [34][35][36][37], castables containing finer magnesia (<45 μm) present better performance for all evaluated temperatures, than those containing coarser magnesia (<100 μm). Many refractory producers consider it as a major challenge to add fine magnesia particles to castables due to the major drawbacks related to the hydration of this component.…”

Influence of nano boehmite on solid state reaction of alumina and magnesia

“…However, a spinel layer forms on the magnesia grains when nano boehmite is added to the sample. This layer inhibits diffusion of Ca 2+ ions into the unreacted alumina, and, therefore, formation of CA 6 phases is suppressed [58][59][60]. Fig.…”