Density of some titanium-bearing silicate liquids and the compositional dependence of the partial molar volume of TiO2

The densities of thirteen silicate liquids along the Na2SiO3-TiO2 and CaSiO3-TiO2 joins and six other titanium-bearing silicate liquids of the general formula TiSiO5 (where X = Li, Na, K, Rb, Cs, Ca, Sr, Ba) have been measured in equilibrium with air using the double Pt bob Archimedean method. The Na2SiO3-TiO2 join was investigated from 10–50 mole% TiO2 in the temperature range 1000–1150°C whereas the CaSiO3-TiO2 join was investigated from 10–80 mole% TiO2 in the temperature range of 1400–1625°C. Density increases with TiO2 content along both joins. Partial molar volumes of the binary endmembers, Na2SiO3 and CaSiO3, and of TiO2 have been computed. The partial molar volume of Na2SiO3 agrees well with that determined by Bockris et al. (1955). The partial molar volume of CaSiO3 is in disagreement with that of Tomlinson et al. (1958). The partial molar volume of TiO2 derived from a linear fit to the Na2SiO3-TiO2 join is 27.6(3) cm3/mole at 1150°C. The partial molar volume of TiO2 derived from linear extrapolation of the CaSiO3-TiO2 data to TiO2 at 1600°C is 24.3(4) cm3/mole. Comparison of the partial molar volume data from these binary joins with TiO2 liquid density data (Dingwell, 1991) requires the existence of a large positive excess volume in the Na2SiO3-TiO2 system at 1150°C

AgandCuloadedonTiO2/graphite as a catalyst for �Escherichia coli- contaminated water disinfection

TiO2 film was synthesized by means of the chemical bath deposition (CBD) method from TiCl4 as a precursor and surfactant cetyl trimethyl ammonium bromide (CTAB) as a linking and assem- bling agent of the titanium hydroxide network on a graphite substrate. Ag and Cu were loaded on the TiO2 film by means of electrodeposition at various applied currents. Photoelectrochemical testing on the composite of Ag–TiO2/G and Cu–TiO2/G was used to define the composite for Escherichia coli-contaminated water disinfection. Disinfection efficiency and the rate of disinfection of E. coli-contaminated water with Ag–TiO2/G as a catalyst was higher than that observed for Cu–TiO2/G in all disinfection methods including photocatalysis (PC), electrocatalysis (EC), and photoelectrocatalysis (PEC). The highest rate constant was achieved by the PEC method using Ag–TiO2/G, k was 6.49 × 10−2 CFU mL−1 min−1 . Effective disinfection times of 24 h (EDT24) and 48 h (EDT48) were achieved in all methods except the EC method using Cu–TiO2/G. Keywords: Ag–TiO2/G, Cu–TiO2/G, Escherichia coli, disinfectio

TiO2 Nanocrystals Grown on Graphene as Advanced Photocatalytic Hybrid Materials

Graphene/TiO2 nanocrystals hybrid is successfully prepared by directly growing TiO2 nanocrystals on graphene oxide (GO) sheets. The direct growth of nanocrystals on GO sheets was achieved by a two-step method, in which TiO2 was coated on GO sheets by hydrolysis first and crystallized into anatase nanocrystals by hydrothermal treatment in second step. Slow hydrolysis reaction through the use of EtOH/H2O mixed solvents and addition of H2SO4 allows the selectively growing TiO2 on GO and suppressing free growth in solution. The method offers easy access to the GO/TiO2 nanocrystals hybrid with well controlled coating and strong interactions between TiO2 and the underlying GO sheets. The strong coupling could lead to advanced hybrid materials for various applications including photocatalysis. The prepared graphene/TiO2 nanocrystals hybrid has demonstrated superior photocatalytic activity in degradation of rhodamine B over other TiO2 materials, showing an impressive 3-fold photocatalytic enhancement over P25. It is expected that the hybrid material could also be promising for various other applications including lithium ion battery where strong electrical coupling to TiO2 nanoparticles is essential.Comment: Nano Research, in pres

Photocatalytic Decomposition of Phenol under Visible and UV Light Utilizing Titanium Dioxide Based Catalysts

Pollution in wastewater effluvia from phenol and phenolic compounds is a common occurrence in many industrial manufacturing plants. Phenol is toxic to human beings as well as a contaminant to the environment, meanwhile, it is difficult to remove from wastewater due to its non-biodegradable nature. To boost the rate of decomposition, various catalytic approaches have been developed. With the interest of decreasing operation cost, titanium dioxide (TiO2) based catalysts have emerged as good candidates for the photocatalytic process. In this honors project, a series of TiO2 based catalysts, including TiO2, N-TiO2, Cu-TiO2, and Cu-N-TiO2, were utilized to study the decomposition of phenol. Each catalyst was studied under the visible light (589nm) and UV light (385nm) conditions. The UV-Vis spectrophotometer was used to evaluate the catalytic performance. The results revealed that the addition of nitrogen improved the decomposition rate of phenol compared with that of TiO2 itself. Copper did not show improved photocatalysis and requires further investigation

Electronic structure and enhanced visible light absorption of N, B-codoped TiO2

We present the GGA+U calculations to investigate the electronic structure and visible light absorption of the N, B-codoped anatase TiO2. The NsBi (substitutional N, interstitial B) codoped TiO2 produces significant Ti 3d and N 2p mid-gap states when the distance of N and B atoms is far, and the NiBi (interstitial N and B) and NsBs (substitutional N and B) codoped TiO2 prefer to form localized p states at 0.3-1.2 eV above the valence band maximum. Further, the optical band edges of the three codoped systems shift slightly to the visible region, but only the far distance NsBi codoped TiO2 shows an obvious visible optical transition. These results indicate that the NsBi codoped TiO2 has a dominant contribution to the visible absorption of the N, B-codoped TiO2.Comment: 4 pages, 4 figures, 17 reference

Development of titanium dioxide nanoparticles/nanosolution for photocatalytic activity

Biological and chemical contaminants by man-made activities have been serious global issue. Exposure of these contaminants beyond the limits may result in serious environmental and health problem. Therefore, it is important to develop an effective solution that can be easily utilized by mankind. One of the effective ways to overcome this problem is by using titanium dioxide (TiO2). TiO2 is a well-known photocatalyst that widely used for environmental clean-up due to its ability to decompose organic pollutant and kill bacteria. Although it is proven TiO2 has an advantage to solve this concern, its usefulness unfortunately is limited only under UV light irradiation. Therefore, the aim of this work was to investigate the potential of TiO2 that can be activated under visible light by the incorporation of metal ions (Fe, Ag, Zr and Ag-Zr). In this study, sol-gel method was employed for the synthesis of metal ions incorporated TiO2. XRD analysis revealed that all samples content biphasic anatase-brookite TiO2 of size 3 nm to 5 nm. It was found that the incorporation of these metal ions did not change the morphology of TiO2 but the crystallinity and optical properties were affected. The crystallinity of anatase in the biphasic TiO2 was found to be decreased and favored brookite formation. PL analysis showed metal ions incorporation suppressed the recombination of electron-hole pairs while the band gap energy of TiO2 (3.2 eV) was decreased by the incorporation of Fe (2.46 eV) and Ag (2.86 eV). Among this incorporation, Ag-Zr incorporated TiO2 showed highest performance for methyl orange degradation (93%) under fluorescent xxv light irradiation for 10 h. This follows by Zr-TiO2 (82%), Fe-TiO2 (75%) and Ag�TiO2 (43%). Meanwhile, the highest antibacterial performance was exhibited by Ag�TiO2. TEM images showed that E.coli bacterium was killed within 12 h after treated with Ag-TiO2. The results obtained from the fieldwork study established that Ag-Zr incorporation have excellent performances for VOC removal and antibacterial test. The VOC content after treated with Ag-Zr-TiO2 fulfilled the Industry Code of Practice on Indoor Air Quality 2010 which is lower than 3 ppm. In addition, the percentage of microbes also found to be decrease around 45 % within 5 days of monitoring

The Density of Titanium(IV) Oxide Liquid

The density of TiO2 liquid in equilibrium with air has been measured at 1875° to 1925°C using an Ir double bob Archimedean method. The melt density data have been combined with data extrapolated from the CaSiO3─TiO2 join at 1600°C. A combined fit to these density data yields the following description of the density of liquid TiO2: ρ= 3.7611 - 0.00028T(°C), in the temperature range of 1600° to 1925°C. This expansivity value is consistent with those obtained on TiO2-rich melts using a Pt-based system at lower temperature and with multicomponent oxide data. The similarity between the volume of liquid TiO2 and that of crystalline rutile implies a dominantly octahedral coordination of Ti in the liquid state

The structural and electrical properties of thermally grown TiO2 thin films

We studied the structural and electrical properties of TiO2 thin films grown by thermal oxidation of e-beam evaporated Ti layers on Si substrates. Time of flight secondary ion mass spectroscopy (TOF-SIMS) was used to analyse the interfacial and chemical composition of the TiO2 thin films. Metal oxide semiconductor (MOS) capacitors with Pt or Al as the top electrode were fabricated to analyse electrical properties of the TiO2 thin films. We show that the reactivity of the Al top contact affects electrical properties of the oxide layers. The current transport mechanism in the TiO2 thin films is shown to be Poole–Frenkel (P–F) emission at room temperature. At 84 K, Fowler– Nordheim (F–N) tunnelling and trap-assisted tunnelling are observed. By comparing the electrical characteristics of thermally grown TiO2 thin films with the properties of those grown by other techniques reported in the literature, we suggest that, irrespective of the deposition technique, annealing of as-deposited TiO2 in O2 is a similar process to thermal oxidation of Ti thin films

A theoretical insight into the catalytic effect of a mixed-metal oxide at the nanometer level: The case of the highly active metal/CeOx/TiO2(110) catalysts

The structural and electronic properties of CeOx species supported on the rutile TiO2 110 surface have been examined by means of periodic density-functional calculations that use a generalized gradient approximation functional including a Hubbard-like type correction. Deposition of Ce atoms leads in a first step to Ce3+ ions bound to the surface through bridge and in-plane oxygen atoms, the released electrons occupying the Ti 3d empty orbitals. Further addition of Ce and molecular oxygen gives place to Ce2O3 dimers diagonally arranged on the surface, in agreement with the spots observed in the scanning tunnel microscope images. The formation process of CeOx nanoparticles NPs on the TiO2 surface is highly exothermic and our calculations show that the redox properties of the Ce III-Ce IV couple are significantly altered when it is supported on TiO2. In particular the reactivity against CO/O2 indicates that on the surface the presence of Ce III is favored over Ce IV species. Our results also indicate that the CeOx /TiO2 interface should be seen like a real mixed-metal oxide rather than a supported NP of ceria. Finally, in the context of the high catalytic activity of the M /CeOx /TiO2 M =Au,Cu,Pt systems in the water-gas shift reaction, we have examined the dissociation of water on the CeOx /TiO2 surface and estimated a barrier as small as 0.04 eV, i.e. 8 times smaller than that computed for a TiO2 oxygen vacancy. This result agrees with the experimental superior catalytic activity of the M /CeOx /TiO2 systems over M /TiO2.Gobierno de España. Ministerio Ciencia e Innovación (MICINN) MAT2005-01872 y CSD2008-0023Junta de Andalucía FQM-132Departamento de Energía de EE. UU. División de Subvención de Ciencias Químicas DE-AC02-98CH1088