Papers by Keyword: Titania

Abstract: Thermal lens spectrometry (TLS) technique was used to obtain the thermal diffusivity of electrospun Titania nanofibers (TiO₂), with average diameter size of 50-80 nm, in water. TiO₂ nanofibers have been successfully prepared by sol-gel and electrospining techniques. TLS provides reliable alternative to measure the thermal diffusivities of semitransparent materials and low thermal diffusivities. The results show that the nanofluid thermal diffusivity increases with the presence of nanofibers. Complementary techniques: scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS) were employed to characterize the nanofibers morphology, average fiber diameter and chemical composition, respectively.

Abstract: 2D nanosheets/ nanoparticles based MoS₂/TiO₂ nanocomposites were prepared in different weight compositions which were further employed to investigate photocatalytic degradation of methylene blue. Anatase TiO₂ powder was prepared via sol-gel reflux method using titanium tetraisopropoxide as Ti precursor. MoS₂/TiO₂ nanocomposites were prepared by in situ addition of exfoliated MoS₂ (2D-nanosheets) in different weight ratios of 0.1%, 0.5%, 1%, 2% and 5% in TiO₂ sol. Surface morphology, phase analysis, optical properties were studied using SEM, XRD, UV-Vis spectroscopy respectively. SEM results showed that TiO₂ nanoparticles were completely adsorbed over the surface of MoS₂ sheets as reflux synthesis was employed. Efficient charge carrier separation was achieved which reduced recombination, and hence, enhanced photo-degradation of methylene blue was observed. The hetero-structures showed less operation time in sunlight for photodegradation of methylene blue and a highest rate constant was observed by 2 wt.% loading of MoS₂ on TiO₂. These composites can also be used commercially as they show promising results.

Abstract: The model explaining the occurrence of the electron concentration step front during oxidation of nitrogen-doped TiO_2-δ thin films is presented. This model is based on ambipolar chemical diffusion coefficient analysis, for which immobile and uniformly distributed nitrogen component is assumed. The diffusion species and oxygen activity (pressure) profiles are obtained by numerical and approximate analytical simulation of the chemical diffusion. The profiles indicate the presence of two separate singularities: the electron concentration step front, and the electron-hole recombination reaction front. The electron concentration step front relates to the singularity of the ambipolar diffusion of three types of charged species with essentially different diffusion coefficients.

Abstract: In the present work formation of active TiO₂ nanofibers in microwave-assisted synthesis and their modification with Au, Pt, Pd and Ag nanoparticles were studied. Anatase nanopowder and 10M KOH solution were used as raw materials. Microwave-assisted synthesis permitted to obtain TiO₂ nanofibers and nanowires with a diameter of 10nm and a specific surface area 158.5m²/g. Chemical deposition method were used to modify TiO₂ nanofibers with precious metal nanoparticles. After modification, specific surface area decreased and were in range 73.1 – 74.7m²/g. Photocatalytic activity was determined by degradation of the methylene blue (MB) solution under visible light irradiation. High intensity LED lamp was used as light source. The obtained samples showed higher photocatalytic activity with respect to pure TiO₂ nanofibers. The doped TiO₂ nanofibers were appropriate for degradation of harmful organic compounds as well as for hydrogen production by water splitting.

Abstract: The meso-porous TiO₂ and Sm-doped meso-porous TiO₂ were synthesized by a sol-gel method. Polyethylene glycol, with different added content, was added as a structure-directing agent. The prepared meso-porous TiO₂ was characterized by nitrogen adsorption, X-ray diffraction and ultraviolet-visible diffuse reflectance spectroscopy, and the photocatalytic performance was evaluated by the decomposition of methyl orange. The results revealed that PEG plays a key role in creating porous structure during the heat-treatment. The photocatalytic performance of TiO₂ is improved by adding proper content PEG, and Sm-doping can further promote the photocatalytic performance.

Abstract: This study was undertaken to compare chemically identical nanoparticles that have been synthesed by different methods. The methodology applied allows the identification of different characteristics in the structure and surface parameters of nanoparticles. The study shows that the structural parameters of nanoparticles are to a great extend related to the conditions in which nanoparticles are formed. This is demonstrated through the comparison of three oxides and their different methods of synthesis. The results show that the method of synthesis defines the structure of the nanoparticles; the surface and qualitative and quantitative parameters of the crystaline phases, energy shifts and changes in the internal electron levels. The examples of nanoliquids and the associated polymer strength identify that the interaction of nanoparticles with the environment is also depends on the synthesis method. It is proposed that a fractal dimension may be used as a basic parameter to classify nanoparticles and predict the properties in their interaction with various media.

Abstract: Titanium dioxide (TiO₂) is one of the most well known photocatalytic materials. However, TiO₂ is only photoactive to ultraviolet (UV) light, and the lifetime of the electron-hole pair recombination is too short. In this work, TiO₂ anatase nanotubes with an energy band gap of 3.01 eV and specific surface area of 112.46 m²/g were synthesized via hydrothermal method. The results showed that, by incorporating graphene oxide (XGO) and reduced graphene oxide (RGO), the photodegradation efficiency could be enhanced by increasing electron lifetime and charge carrier separation, as well as narrowing the energy band gap. The examination of photodegradation activity under UVC irradiation indicated that a maximum photodegradation efficiency was achieved with TiO₂-XGO nanocomposite due to its high specific surface area and strong hydrophilic property.

Abstract: In this research photocatalytic degradation of nanotitania synthesized via sol-gel method and coated on commercial unglazed ceramic tiles was investigated. The starting precursors were titanium (IV) tetraisopropoxide (Ti [OCH(CH₃)₂]₄; TIP), ethanol, hydrochloric acid and distilled water. Unglazed ceramic tiles were sintered at 900°C and 1100°C. The nanotitania based sols were applied on the tile surface using air-brush and calcined at 500°C for 3 h. The particle size of the synthesized TiO₂ varied in the range 8-20 nm. The photocatalysis of nanotitania was studied through the photodegradation of methylene blue solution under UVC irradiation using UV-Vis Spectrophotometer. The presence of nanotitania on unglazed ceramic tiles was confirmed by a scanning electron microscope equipped with energy dispersive X-ray spectrometer (EDS). Ceramic tiles sintered at 900°C gave higher % open porosity and hence higher amount of nanotitania embedded on the ceramic surface. The results showed that all unglazed ceramic tiles coated with nanotitania were able to show photodegradation of methylene blue.

Abstract: The Fe₃O₄/TiO₂-Ni composites have been prepared by incorporating magnetic particles with doped photoactive titania using sono-coprecipitation and sol-gel methods. The composite was characterised by Fourier Transform infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy with Energy Disperse X-Ray Spectroscopy (SEM-EDX), Vibrating Sample Magnetometry (VSM) and Specular Reflectance Ultraviolet-Visible light spectroscopy (SR-UV). The results indicated that the composite of Fe₃O₄/TiO₂-Ni had been synthesised. XRD and FTIR results showed that the composite had a good anatase phase. SEM-EDX result confirmed the atomic percentage of element presence in the synthesised product and VSM result proved that the composite has an excellent magnetisation moment of 8.76 emus. SR-UV result suggested that the composite had a good bandgap property compared to that of synthesised undoped titania.

Abstract: In this research, the effect of different hydrothermal treatment temperature (100, 150, and 200 °C) on the products obtained by hydrothermal method was studied. Various characterization techniques was carried out such as X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive of x-ray spectroscopy (EDX) and fourier transform infrared spectroscopy (FTIR). XRD analysis shows that titanate phase was formed at 150 and 200 °C hydrothermal treatment. On the other hand, at 100 °C anatase TiO₂ phase structured was gained which is similar with the TiO₂ precursor. Morphological study using FESEM revealed that nanofibers and nanorods samples obtained at 150 °C and 200 °C, respectively. At 100°C, irregular shaped particle was attained similar with TiO₂ precursors. FTIR spectra for the all studied sample displayed three main broad peaks at the range of 3700-2800, and 1800-1400 assigned to –OH stretching and deformation mode due to H₂O molecules and M-O stretching mode at 900-400 cm^-1 assigned to Ti-O bond.