Synthesis, hydration and sintering of calcium aluminate nanopowder for advanced applications

Seven batches of calcium aluminate powder containing different ratios of alumina and calcium oxide were chemically prepared by thermal decomposition method. The produced powder was investigated in terms of phase composition and morphology by XRD pattern and scanning electron microscope (SEM). The hydration and sintering of the prepared powder were also studied. Phase composition, microstructure and mechanical properties of the hydrated and sintered bodies were tested. The results revealed that the batches containing high CaO/Al2O3 ratios i.e., batches 1, 2 and 3 composed mainly of CaO.Al2O3 (CA) and 12CaO.7Al2O3 (C12A7) phases while batches containing low CaO/Al2O3 ratios i.e., batches 4, 5, 6 and 7 composed of CA and CA2 (CaO.2Al2O3) phases. The amount of these phases affected the properties of hydrated as well as the sintered bodies. The hydration of batches No. 1, 2 and 3 achieved higher strength than batches containing low CaO/Al2O3 ratios due to the presence of CA and C12A7 as a major component, since they react rapidly with water. The presence of C12A7 phase in the batches containing higher CaO/Al2O3 ratios decreased the apparent porosity and consequently increased the mechanical properties of the sintered bodies. The obtained materials can be applied for different advanced applications. The bioactivity of the obtained materials will be studied and published as a second part of this article.