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Calcium oxide (CaO) is an important inorganic compound, which is used across various industries as catalyst, toxic-waste remediation agent, adsorbent, etc. CaO nanoparticles were obtained by the microwave irradiation technique, using Ca(NO₃)₂ ⋅ 4H₂O and NaOH as starting materials. The formation of monocrystalline CaO nanoparticles was confirmed by the XRD (X-ray diffraction) and TEM (transmission electron microscopy) as well as by SAED (selected area electron diffraction) analysis. The structure of the CaO nanocrystal was found to be cubic with particle size, 24 nm and surface area, 74 m²/g.

This work proposes the synthesis of nanocrystalline calcium oxide (CaO) pure and doped with different concentrations of lithium (Li${}^{2+}$) ions by sol–gel process. Calcium nitrate (Ca(NO${}_3{)}_2\cdot$4H₂O; 99.99%) and lithium nitrate (LiNO₃; 99.99%) were used as precursors. The synthesized powders were characterized by several techniques such as: UV-Vis transmission spectroscopy, Fourier Transform Infra-red spectroscopy (FT-IR) and X-ray diffraction (XRD). The main objective of this paper is to study the influence of lithium (Li${}^{2+}$ ratio) on the structural and optical properties of synthesized powders. The band gap values decreased with the increasing of Li${}^{2+}$ ions in CaO lattice; the slight change in the band gap was directly related to the energy transfer between the CaO excited states and the 2s levels of Li${}^{2+}$ ions. The influence of Li${}^{2+}$ doping on the physical properties of CaO nanocrystalline will be studied for the first time in this work; no literature has previously published this kind of impurities.

In this paper, orthogonal experiment was designed pragmatically by five factors and five levels and then considering the content of f-CaO and MgO to determine the process parameters. Carbonation depth, content of free-CaO and MgO were quantitatively analyzed by phenolphthalein indicator, benzoic acid - ethanol standard titration solution and EDTA titration respectively. The volume stability of mortar was measured by autoclave test. The results show that the content of free-CaO of carbonated steel slag aggregate are effected, in the order from influence degree, by moisture, carbonated pressure, carbonated time, carbonated temperature and molding pressure. Their optimal parameters are 12wt.%, 0.15MPa, 8h, 60°C and 9MPa respectively. The specimens with the f-CaO content of more than 3wt.% are all spalled, and though 5wt% of MgO is existed in carbonated aggregate, volume stability mortar is unaffected.