Papers by Keyword: Anatase

Abstract: The anatase phase of titanium dioxide ceramic material plays important rule in heterogeneous photocatalysis, beside the global phase amount and powder morphology. Some of structural parameters are useful to predict several properties, including the crystallization process and mechanism of the irreversible anatase-to-rutile phase transition. The photocatalytic process is based on charge transference from electron-hole pair to material surface, starting some redox reactions in aqueous media. The stable positive defects harm the recombination event and improve the final properties of that material. Modifiers with lower oxidation state than titanium (IV) is applicable for this purpose, what idea becomes the objective of this work. The Sol-Gel method was used to prepare bare and zinc doped-titanium dioxide powder samples reaching good compositional homogeneity for both samples calcined at 500 oC for 4 hours. Rietveld refinement carried out from raw x-ray diffraction patterns was used to demonstrate the formation of solid solution between zinc and titanium oxides. Besides that result, the determination of bandgap energy and SEM images corroborated the structural changes caused by zinc insertion in anatase phase and important difference in powder morphology was observed for zinc doped powder samples in order to reduce the agglomeration degree for better performance for heterogeneous photocatalysis applications.

Abstract: Important changes in anatase crystal structure are responsible for the consequent anatase-to-rutile phase transition in titanium dioxide powders. In order to investigate several structural rearrangements occurring in anatase phase obtained by hydrolysis-based method such as Sol-Gel method the X-ray diffraction techniques followed by Rietveld method seems to better approach. Several alterations in anatase lattice parameters can occur by doping insertion and the investigation of isostructural zircon silicate can provide interesting ones. In the present paper, the monitoring of anatase structure reordering and the consequent anatase-to-rutile phase transition along the thermal treatment up to higher temperatures were monitored carrying out DSC and XRD characterizations. The insertion of 6 mol% of zircon silicate leads to the fully anatase stabilization up to 900 °C due the control of ordering process, even that a continuous increasing in anatase tetragonality is present during the entire process. We can conclude the reconstructive anatase-to-rutile phase transition is delayed to very higher temperatures can consequence of more stable cross-linked metal oxide bond in anatase phase.

Abstract: The nano-sized TiO₂ is an important material based on its application for solar cells. The low-cost synthesis of nano-sized TiO₂ is of high demand for commercial purposes. Synthesis of TiO₂ nanoparticles was achieved via the low-temperature Sol-gel method. Surface morphology was confirmed from SEM analysis, which showed that particle size is in the range of nanometer with no aggregation, The XRD results confirm the formation of anatase phase with high crystallinity. Furthermore, as prepared nano-sized TiO₂ particles were developed as sol-gel ink which was later deposited by spin coating on glass substrate with controlled spinning speed thereafter structural and optical properties were characterized by UV-vis spectroscopy, electrochemical impedance spectroscopy and DSC-TGA. The low-cost synthesis of TiO₂ nanoparticles with highly conductive thin films can be used as a potential material for future dye-sensitized solar cells

Abstract: Anatase-type titanium dioxide oxide layer was formed on the surface of titanium alloy by chemical oxidation. 0.9 um thick anatase was obtained by soaking in a mixed solution of a certain proportion of hydrogen peroxide and hydrochloric acid and then heat treatment. The surface morphology, phase structures and composition of oxide layers were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Thickness of titania coating was measured by the ball pit gauge. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to detect the change of Ca ion and P ion concentration in solution. The results showed that anatase layers deposited apatite within 4 days accompanying the decrease of pH when soaked in simulated human body fluid (SBF). Ion exchange between the negative ions and calcium ions in SBF is proposed as the mechanism operative to favor the deposition on apatite.

Abstract: Ag/TiO₂ thin films were prepared via sol-gel spin coating method. Structural, surface morphology and optical properties were investigated with the addition of two different amount of silver (Ag). X-ray diffraction pattern shows the sample with pure TiO₂, the only phase presence was brookite TiO₂. When the Ag content added into the solution, the phase existed for the samples with TiO₂ doped 0.5g Ag and TiO₂ doped 1.0g Ag were anatase TiO₂ with no peak corresponds to Ag phase. The surface morphology of film was characterized by scanning electron microscopy (SEM). The films were annealed at 450 °C and it shows non-uniform films. The films have a large flaky and cracks film which was attributed to surface tension between the film and the air during the drying process. When the solution of sol was added with Ag content, it shows the porous structure with flaky-crack films. With the increasing of the Ag content from 0.5g to 1.0g, the structure is more porous and it is good for the photocatalytic activity. The UV-Vis spectra shows that the film exhibits a low absorbance which was due to the substrate is inhomogeneously covered by the flaky-crack films.

Abstract: Dye sensitized solar cell (DSSC) is a well-known photovoltaic device that is used for low power application. One of the main components for DSSC is semiconductor material photoanode which will provide the pathway for electron transportation and thus determine the energy conversion efficiency of the DSSC. The most commonly used material for the semiconductor photoanode is titanium dioxide (TiO₂)_. TiO₂ is a semiconductor material with wide bandgap material that is existed in three crystalline phase; rutile, anatase and brookite. This paper emphasizes the best annealing temperature for commercialized TiO₂, 98% anatase powder where the temperature varies from 300 oC – 600 oC. Through this research, the best annealing temperature for anatase TiO₂ photoanode is at 420 °C (0.094%) with the crystallite size of 18.76 nm and particle size of 19 nm that is favorable for the dye attached and thus enhances the energy conversion efficiency of the DSSC.

Abstract: In this work two different hydrosols were used to impregnate a commercially available cotton fabric with anatase nanoparticles to give it photocatalytic activity. To increase the activity, different pre-treatment methods were applied. The nanoparticle size was determined using dynamic light scattering and x-ray diffraction and the fabrics were examined using scanning electron microscopy. Photocatalytic activity was measured using the degradation of methyl-orange while irradiating the samples with UV light. The synthesis method allowed to produce anatase with an average particle size of 32 to 37 nm depending on the synthesis method used.

Abstract: The titanium dioxide phase formation is dependent on the synthesis method, temperature of calcination and modifiers insertion. By using chemical methods, such as Polymeric Precursor Method, the organic impurities or extrinsic defects caused by doping play an important rule on the formation of precursor structure before the phase crystallization above 500 oC. Some dopants can change the decomposition mechanism of the precursor, which affects the anatase-rutile phase transition. In this work, the Polymeric Precursor Method was used to synthesize titanium dioxide powder samples in order to investigate the effects of iron (III) and vanadium (V) dopants on the phase formation. Through thermal analysis of polymeric precursors and X-ray diffractometry for calcined powder samples it was possible to show the existence of antagonistic effects for both investigated dopants. While the iron doping reduces the anatase phase tetragonality and delays the rutile phase conversion, the vanadium one changes the mechanism of decomposition of polymeric precursor and leads to more amount of rutile phase.

Abstract: Titanium carbide has been attractive for years an engineering ceramics due to its high hardness, high melting point, and good chemical stability. Similarly, titanium dioxide has excellent anti-microbial ceramic material by photon energy. In this study, the anatase type titanium dioxide layer prepared by oxidation of the titanium carbide powder by high temperature oxidation in air atmosphere was investigated in order to determine the possibility of its photocatalyst materials by radiant energy. TiC powder samples of different grain size were gained by ball mill. These samples were oxidized at room temperature to high temperature. The samples exhibited a steady mass gain with increasing oxidation temperature. Based on the results of the X-ray diffraction analysis, anatase type TiO₂ was detected on the titanium carbide samples. It is considered, the titanium carbide showed convension anatase type titanium dioxide layer produced by oxidation.

Abstract: This review focuses on the recent developments of high temperature stable anatase TiO₂ photocatalyst. Eventhough TiO₂ exists in different forms anatase, rutile and brookite, anatase phase stabilization is often the key to obtain the highest photocatalytic performance for TiO₂, particularly for the use as an antibacterial and self-cleaning coatings in high temperature processed ceramics. Different methods available for the anatase stabilization in literature are critically reviewed and emphasis is placed on relatively recent developments. Currently available methods of anatase stabilizations are classified in to four categories viz (i) doping with metal ions (ii) doping with non-metal ions (iii) co-doping with metal and non-metal ions and (iv) dopant free stabilization by oxygen richness. Further to this, the application of these high temperature stabilized anatase TiO₂ photocatalyst on various ceramics substrates such as tile, glass and sanitary wares as self-cleaning and antibacterial coatings are also been briefly discussed.