Grain boundary diffusion effect on mineral transition of calcium sulpho-aluminate with sodium dopant

The mineral formation-transition mechanism, microstructure morphology evolution, pulverization property and chemical reactivity of calcium sulpho-aluminate with sodium dopant are systematically studied with the molar ratio of CaO to Al2O3 is 0.8, the molar ratio of CaO to SiO2 is 1.5, the mass ratio of Al2O3 to SiO2 is 2.0, and the SO3 accounts for 4%. The results show that sodium dopant could promote 3CaO.3Al2O3.CaSO4, CaO.2Al2O3 and 2CaO.Al2O3.SiO2 transform into 2CaO.SiO2, CaO.Al2O3, 12CaO.7Al2O3 and 2Na2O.3CaO.5Al2O3, and it also can decrease the decomposition temperature of reactive materials and the initial phases formation temperature significantly. Sodium diffusion can destroy the clear grain boundary of calcium aluminate and calcium silicate phases, change the macro-microstructure morphology, improve the crystalline degree of the samples, and then improve the pulverization and alumina leaching property. However, excessive sodium dopant can decrease the melting temperature, inhibit the transformation process of 2CaO.SiO2 from beta to gamma, and then deteriorate the pulverization property significantly again.

Automated summary

Sodium doping has a significant impact on the mineral transformation and crystalline degree of calcium sulpho-aluminate, ultimately affecting its pulverization and alumina leaching property. However, excessive sodium dopant can lower the melting temperature and hinder the phase transformation process, leading to a decrease in pulverization performance.