Sharif Digital Repository

Nanocrystalline and nanostructured TiO2-Cr2O3 thin films and powders were prepared by a facile and straightforward aqueous particulate sol-gel route at low temperature of 400°C. The prepared sols showed a narrow particle size distribution with hydrodynamic diameter in the range of 17.7 nm to 19.0 nm. Moreover, the sols were stable over 4 months, with constant zeta potential measured during this period. The effect of the Cr:Ti molar ratio on the crystallization behavior of the products was studied. X-ray diffraction (XRD) analysis revealed that the powders crystallized at low temperature of 400°C, containing anatase-TiO2, rutile-TiO2, and Cr2O3 phases, depending on the annealing temperature... 

Nanostructured and nanoporous TiO2-Ga2O3 films and powders with various Ti:Ga atomic ratios and high specific surface area (SSA) have been prepared by a new straightforward particulate sol-gel route. Titanium isopropoxide and gallium (III) nitrate hydrate were used as precursors and hydroxypropyl cellulose (HPC) was used as a polymeric fugitive agent (PFA) in order to increase the SSA. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that powders contained both rhombohedral α-Ga2O3 and monoclinic β-Ga 2O3 phases, as well as anatase and rutile. It was observed that the Ga2O3 formed from the nitrate precursor retarded anatase-to-rutile transformation.... 

The morphological manipulation and structural characterisation of TiO 2-MgO binary system by an aqueous particulate sol-gel route were reported. Different crystal structures including pure MgTiO 3, mixtures of MgTiO 3 and TiO 2 and mixtures of MgTiO 3 and Mg 2TiO 4 were tailored by controlling Mg:Ti molar ratio and annealing temperatures as the processing parameters. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that all compounds crystallised at the low temperature of 500 °C. Furthermore, it was found that the average crystallite size of the compounds depends upon the Mg:Ti molar ratio as well as the annealing temperature, being in the range 3-5 nm at... 

Using a combined hydrothermal and sol-gel route, TiO 2 -capped ZnO nanoparticles with an average size of 60 nm were prepared. The titania shell was amorphous with a thickness of ∼10 nm. Formation of Zn 2TiO 4 phase at higher calcination temperature was noticed. Effects of Ti/Zn molar ratio and coating time on the thickness of TiO 2 shell and the photoactivity of the particles for decolorization of Methylene Blue (MB) under UV lamp irradiation (3 mW/cm 2) were investigated. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, fourier-transform infrared spectrometry (FTIR), diffuse reflectance spectroscopy (DLS), and atomic absorption spectroscopy.... 

Nanocrystalline TiO 2-Fe 2O 3 thin films and powders were prepared by a straightforward aqueous particulate sol-gel route at the low temperature of 300 °C. Titanium(IV) isopropoxide and iron(III) chloride were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powder crystallised at the low temperature of 300 °C, containing anatase-TiO 2 and hematite-Fe 2O 3 phases. Furthermore, it was found that Fe 2O 3 retarded the anatase-to-rutile transformation up to 500 °C. The activation energies for crystallite growth of TiO 2... 

The low temperature perovskite-type strontium titanate (SrTiO 3) thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route. The prepared sol had a narrow particle size distribution with hydrodynamic diameter of about 17 nm. X-ray diffraction (XRD) revealed that the synthesized powders had a perovskite-SrTiO 3 structure with preferable orientation growth along the (1 0 0) direction. TEM images showed that the average crystallite size of the powders annealed in the range 300-800°C was around 8 nm. FE-SEM analysis and AFM images revealed that the deposited thin films had mesoporous and nanocrystalline structure with the... 

A developed route to form TiO2 self cleaning coatings on polycarbonate substrates is reported. TiO2 coatings on plastics may find widespread application in auto and construction industries if possess desired photocatalytic and mechanical properties. A chemical surface treatment method was used to create hydrophilic groups on the surface. X-ray photoelectron spectroscopy showed the treatment led to the oxidation of surface groups. TiO2 deposition was based on wet coating using an anatase sol of TiO2 nanoparticles of 30 nm size. The sol was synthesized using a sol-gel route. A pre-coat of peroxotitanium complex was employed to improve adhesion and inhibit the substrate degradation. The coating... 

ZnO nanoparticles were fabricated via hydrothermal method and an amorphous TiO2 layer was then coated on the nanoparticles via sol-gel route. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed that the synthesized ZnO nanoparticles were hexagonal with wurtzite structure and an average particle size of 38 nm. The thickness of the titanium oxide layer was determined to be 20-40 nm. The photocatalytic decolorization of Methylene blue under UV irradiation indicated that as-prepared TiO 2-capped ZnO is inferior than ZnO particles. Nevertheless, calcinations of the particles at 350 °C for 24 h significantly improved the photo-activity of the ZnO/TiO2 core/shell... 

Perovskite-type barium strontium titanate (BST) thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route at room temperature. The prepared sol had a narrow particle size distribution of about 20 nm. X-ray diffraction (XRD) revealed that phase composition and preferable orientation growth of BST depended upon the annealing temperature. Transmission electron microscope (TEM) images showed that the crystallite size of the powders decreased with increasing annealing temperature from 8 nm at 25 °C down to 5 nm at 800 °C. Field emission scanning electron microscope (FE-SEM) analysis and atomic force microscope (AFM) images... 

Nanocrystalline nickel titanate (NiTiO3) thin films and powders with mesoporous structure were produced at the low temperature of 500 °C by a straightforward particulate sol-gel route. The sols were prepared in various Ni:Ti molar ratios. X-ray diffraction and Fourier transform infrared spectroscopy revealed that the powders contained mixtures of the NiTiO 3 and NiO phases, as well as the anatase-TiO2 and the rutile-TiO2 depending on the annealing temperature and Ni:Ti molar ratio. Moreover, it was found that Ni:Ti molar ratio influences the preferable orientation growth of the nickel titanate, being on (202) planes for the nickel dominant powders (Ni:Ti ≥ 75:25) and on (104) planes for the... 

Low temperature lithium titanate compounds (i.e., Li4Ti 5O12 and Li2TiO3) with nanocrystalline and mesoporous structure were prepared by a straightforward aqueous particulate sol-gel route. The effect of Li:Ti molar ratio was studied on crystallisation behaviour of lithium titanates. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powders were crystallised at the low temperature of 500 °C and the short annealing time of 1 h. Moreover, it was found that Li:Ti molar ratio and annealing temperature influence the preferable orientation growth of the lithium titanate compounds. Transmission electron microscope (TEM) images showed that the average... 

Nanocrystalline zinc titanate (ZnTiO3) thin films and powders with purity of 94% were produced at the low sintering temperature of 500 °C and the short sintering time of 1 h by a straightforward aqueous particulate sol-gel route. The effect of Zn:Ti molar ratio was studied on the crystallisation behaviour of zinc titanates. The prepared sols showed a narrow particle size distribution in the range 17-19 nm. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powders contained mixtures of the rhombohedral-ZnTiO3, cubic-ZnO, cubic-Zn2TiO4 phases, as well as the anatase-TiO2 and the rutile-TiO2 depending on the sintering temperature and Zn:Ti molar ratio.... 

Low-temperature perovskite-type cadmium titanate (CdTiO3) with a nanocrystalline and mesoporous structure was prepared at various Ti:Cd molar ratios by a straightforward particulate sol-gel route. The prepared sols had a narrow particle size distribution, in the range 23-26 nm. X-ray diffraction and Fourier transform infrared spectroscopy revealed that the powders contained a mixture of ilmenite-CdTiO3, perovskite-CdTiO3, anatase and rutile phases, depending on the annealing temperature and the Ti:Cd molar ratio. Perovskite-CdTiO3 was the major type obtained from cadmium-prominent powders at low temperature, whereas ilmenite-CdTiO3 was the major type obtained from titanium-prominent powders... 

Nanostructured TiO2-ZrO2 thin films and powders were prepared by a straightforward aqueous particulate sol-gel route. Titanium (IV) isopropoxide and zirconium (IV) acetate hydrate were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy revealed that the powder were crystallised at the low temperature of 500 °C, containing anatase-TiO 2 and tetragonal-ZrO2 phases. Furthermore, it was found that ZrO2 retarded the anatase-to-rutile transformation up to 900 °C. The activation energies for crystallite growth of TiO2 and ZrO2 components in... 

Nanostructured TiO2-CeO2 thin films and powders were prepared by a straightforward aqueous particulate sol-gel route. Titanium (IV) isopropoxide and cerium chloride were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. The effect of Ce:Ti molar ratio was studied on the crystallisation behaviour of the products. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powders crystallised at the low temperature of 500 °C, containing anatase-TiO2, rutile-TiO2 and cubic-CeO2 phases, as well as Ti 8O15, Ti3O5 and Ce 11O20 depending on annealing temperature and Ce:Ti molar... 

Nanocrystalline neodymium titanium oxide thin films and powders with different phase compositions with mesoporous structure were produced by a straightforward particulate sol-gel route. The sols were prepared in various Nd:Ti molar ratios and they showed a narrow particle size distribution in the range 20-26 nm. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powders contained mixtures of Nd4Ti9O24, Nd2Ti4O11, Nd3Ti4O12 for titanium dominant powders (Nd:Ti ≤ 45:60), mixtures of Nd2TiO5 and Nd2O3 for neodymium dominant powders (Nd:Ti ≥ 75:25) and pure Nd3Ti4O12 phase for equal molar ratio of Nd:Ti, depending on the annealing temperature and Nd:Ti... 

A systematic comparison of single and binary metal oxide TiO2, TiO2-Er2O3 and TiO2-Ta2O5 thin film gas sensors with nanocrystalline and mesoporous microstructure, prepared by sol-gel route, was conducted. The gas sensitivity was increased by secondary phase introduction into TiO2 film via two mechanisms, firstly due to the inhibition of anatase-to-rutile transformation, since the anatase phase accommodates larger amounts of adsorbed oxygen, and secondly due to the retardation of grain growth, since the higher surface area provides more active sites for gas molecule adsorption. The binary metal oxide gas sensors exhibited a remarkable response towards low concentrations of CO and NO2 gases at...