In this study, the carbonation of Portland cement by direct chemical interaction with graphene oxide (GO) and reduced graphene oxide (rGO) at 7 and 28 days was examined. During the carbonation reaction, the calcium-bearing phases (calcium hydroxide, calcium silicate hydrate, and ettringite) formed calcium carbonate polymorphs, along with amorphous silica gel, gypsum, and alumina gel. These reaction products were examined using XRD (X-ray diffraction), XPS (energy-dispersive spectrometry), and FTIR (Fourier transform infrared). XRD patterns showed that the intensities of the calcium hydroxide and calcium carbonate peaks in the hydrated cement mixed with GO and/or rGO are higher than the corresponding peaks in the hydrated cement without any additives. The morphology of the reaction products was also characterized by SEM (scanning electron microscopy) measurements, which showed that a needle-like phase of calcium carbonate develops on the hydrated cement. The obtained microstructure parameters enabled the development of a more precise carbonation model.

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The current work investigates the influence of seawater on morphological properties during the hydration process of tricalcium silicate (C3S) at 3, 7, 14, and 28 days to better understand the effect of salinity (highly soluble salts) of seawater on the microstructural evolution of hydration products. The mechanism of the chemical reaction of highly soluble salts, e.g., Na2SO4 and CaCl2, with hydrated C3S was also demonstrated. The presence of highly soluble salts in seawater accelerates the hydration of C3S significantly due to releasing a significant amount of Ca2+ ions from the hydrated C3S (as CH and CSH), which participated in the chemical reaction to produce a certain amount of gypsum crystals that was more than that in distilled water, which has been shown by SEM characterization. TEM analysis revealed the growth of sharp rod-like CaSO4·2H2O crystals together with some thin and tiny wrinkled CSH that formed. Seawater promotes the hydration of C3S, pointed out by the expedited heat flow and raised heat of hydration. FTIR spectroscopy has been used to characterize and observe the dynamics of variation in the formation of calcium silicate hydrate (CSH), portlandite (CH), and gypsum (Gy) throughout the hydration process of C3S with seawater in comparison with distilled water. XRD analysis revealed that the peak intensities of the portlandite and gypsum of the hydrated C3S in seawater are higher than the comparable peaks in distilled water.

The influence of anodization time with the electrochemical cell design on the fabrication process of porous silicon (PS) nanostructures based on two electrochemical anodization cells (designed single tank cell and double tank cell) with two anodization times (10 and 30 minutes) was studied. Atomic force Microscopy (AFM) characterization had revealed three types of pores, mesopores, mesopore fill of mesopores, and macropore fill of mesopores were obtained from designed single tank cell with (10 and 30 minutes) of anodization time, whilst for double tank cell has not revealed precise information about the size and type of pores. Pores formation have been further approved by current-voltage (I-V) measurement and photoluminescence emission by ultraviolet-lamp (254-366) nm for both electrochemical cells.

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