Sol–gel combustion synthesis. The preparation process was
shown in our formed study [15]. The molar ratio of Ca to Mg and
citric acid was shown in the latter section. The prepared sample
was finally calcined at 850 C for 10 min in N2 in a tube furnace
for fully decomposition of precursors before cyclic carbonation
tests.
The main difference between the wet mixing and sol–gel combustion
synthesis is that the amount of water was reduced and the
mixing duration was shortened by wet mixing combustion synthesis.
Moreover, a wider variety of calcium precursors (including soluble
and insoluble calcium precursors) can be used by this method.
But, in the sol–gel process, only soluble precursors are applicable.