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We proposed a good calcinations condition of the ZnO disk to control the crystallography and nanoparticles in ZnO disk. The crystallography of precursor powder and disk powder were analyzed by the X-ray diffraction (XRD). The mean nanoparticles of ZnO disk was determinate by XRD results and observed by scanning electron microscope. The temperature ranges of 400℃ to 650℃ in air for 30 minutes were used calcinations ZnO disk. These temperature can be controlled the single phase, lattice parameters, unit cell volume, crystalline size, d-value, texture coefficient and bond lengths of Zn–Zn, Zn–O and O–O which correspond significantly the hexagonal crystal structure. The nanoparticles were small changed mean of 76.59 nm at the calcinations temperature range

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A comparative study of TiO 2 powders prepared by precipitation and sol-gel methods was conducted. Titanium tetrachloride and titanium tetraisopropoxide were used as the starting materials for the precipitation and sol-gel processes, respectively. The effects of the two different drying methods, freeze drying and normal drying at 100°C, of the precipitates on the properties of the prepared TiO 2 powders were also investigated. The effects of the synthesis methods on phase, surface area, crystallite size, and photodegradation of methylene blue were studied by XRD, SEM, TEM, BET, and UV/ Vis techniques. It was found that the major phase of the synthesized TiO 2 was anatase, but small amounts of the brookite phase (Ͻ10 %) were found in some samples. The synthesized anatase TiO 2 with no pretreatment was found to be stable up to 600°C for the samples prepared by the precipitation