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In situ energy dispersive X-ray diffraction (EDXRD) has been used to monitor the crystallization of TiO2 nanoparticles from hydrothermal reactions of nitric acid (HNO3) peptized sol–gels at 210, 230, 250 and 270 °C. The EDXRD peaks revealed the formation of pure rutile phase TiO2 particles from all the hydrothermal reactions studied. The reaction kinetic data have been determined by monitoring changes in the integrated peak areas of the highest intensity diffraction peak (110). A kinetic and mechanistic analysis of the hydrothermal synthesis of TiO2 nanoparticles has been proposed based on the Avrami–Erofe'ev kinetic model. The Avrami exponent values obtained were within the range of around 0.5–1 for all the reactions studied, indicating that the hydrothermal crystallization of TiO2 nanoparticles involves a diffusion-controlled process mechanism. The as-synthesized TiO2 nanoparticles have been further characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD data are in good agreement with the EDXRD results and confirm the formation of pure rutile phase TiO2 particles. The TEM results showed that the TiO2 particles produced are below 100 nm in size and exhibit bi-modal size and morphology distribution. [ABSTRACT FROM AUTHOR]

In order to control the particle size and morphology, zinc carbonate hydroxide Zn 5 (CO 3 ) 2 (OH) 6 nanoparticles have been synthesized using a reverse microemulsion technique. The pseudo-ternary phase diagrams of the two microemulsion systems, prepared using CTAB/1-butanol/n-octane/aqueous phase system with the aqueous phase comprised of either zinc nitrate (Zn(NO 3 ) 2 ) or sodium carbonate (Na 2 CO 3 ), were experimentally constructed. The nanoparticles synthesized by mixing of the two emulsion systems were further characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The nanoparticles were further characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Several important experimental parameters have been investigated for the ability to control particle size and morphology as the function of water/surfactant molar ratio (ω), water/oil molar ratio ( S ) and the initial concentration of reactants in the aqueous phase. Results indicate that ω values have the ability to affect the particle size and levels of aggregation, while S values had no apparent effect. In addition, the initial concentration of reactants in the aqueous phase was considered to be an important parameter as raising its values from 0.1 M to 0.5 M produced an unknown phase of zinc carbonate, exhibiting larger particle size with a unique flake like morphology. [ABSTRACT FROM AUTHOR]