Explore the vast range of titles available.

This book deals with the synthesis, properties and applications of titanium dioxide (TiO2) which is a naturally occurring oxide of the element titanium. In nature these oxides are found in well-known minerals such as Rutile, Anatase and Brookite. However, it is most commonly extracted from titanium tetrachloride by carbon reduction and re-oxidization. Alternatively, it may be processed from another oxide called ilmenite, which is subjected to reduction with sulphuric acid to achieve pure titanium dioxide.

The coupling behaviour of H.sup.+ and trace elements in rutile has been studied using in situ polarised Fourier transform infrared (FTIR) spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. H.sub.2 O contents in rutile can be precisely and accurately quantified from polarised FTIR measurements on single grains in situ. The benefits of this novel approach compared to traditional quantification methods are the preservation of textural context and heterogeneities of water in rutile. Rutile from six different geological environments shows H.sub.2 O contents varying between â¼ 50-2200 µg g.sup.-1, with large intra-grain variabilities for vein-related samples with H.sub.2 O contents between â¼ 500 and â¼ 2200 µg g.sup.-1 . From FTIR peak deconvolutions, six distinct OH absorption bands have been identified at â¼ 3280, â¼ 3295, â¼ 3324, â¼ 3345, â¼ 3370, and â¼ 3390 cm.sup.-1 that can be related to coupled substitutions with Ti.sup.3+, Fe.sup.3+, Al.sup.3+, Mg.sup.2+, Fe.sup.2+, and Cr.sup.2+, respectively. Rutile from eclogite samples displays the dominant exchange reactions of Ti.sup.4+ â Ti.sup.3+, Fe.sup.3+ + H.sup.+, whereas rutile in a whiteschist shows mainly Ti.sup.4+ â Al.sup.3+ + H.sup.+ . Trace-element-dependent H.sup.+ contents combined with LA-ICP-MS trace-element data reveal the significant importance of H.sup.+ for charge balance and trace-element coupling with trivalent cations. Trivalent cations are the most abundant impurities in rutile, and there is not enough H.sup.+ and pentavalent cations like Nb and Ta for a complete charge balance, indicating that additionally oxygen vacancies are needed for charge balancing trivalent cations. Valance states of multivalent trace elements can be inferred from deconvoluted FTIR spectra. Titanium occurs at 0.03 0/00-7.6 0/00 as Ti.sup.3+, Fe, and Cr are preferentially incorporated as Fe.sup.3+ and Cr.sup.3+ over Fe.sup.2+ and Cr.sup.2+, and V most likely occurs as V.sup.4+ . This opens the possibility of H.sup.+ in rutile as a potential indicator of oxygen fugacity of metamorphic and subduction-zone fluids, with the ratio between Ti.sup.3+ - and Fe.sup.3+ -related H.sup.+ contents being most promising.

The contiguous region between Guangxi, Guizhou, and Yunnan, commonly referred to as the Golden Triangle region in SW China, hosts many Carlin-type gold deposits. Previously, the ages of the gold mineralization in this region have not been well constrained due to the lack of suitable minerals for radiometric dating. This paper reports the first SIMS U–Pb age of hydrothermal rutile crystals for the Zhesang Carlin-type gold deposit in the region. The hydrothermal U-bearing rutile associated with gold-bearing sulfides in the deposit yields an U-Pb age of 213.6 ± 5.4 Ma, which is within the range of the previously reported arsenopyrite Re–Os isochron ages (204 ± 19 to 235 ± 33 Ma) for three other Carlin-type gold deposits in the region. Our new and more precise rutile U-Pb age confirms that the gold mineralization was contemporaneous with the Triassic W–Sn mineralization and associated granitic magmatism in the surrounding regions. Based on the temporal correlation, we postulate that coeval granitic plutons may be present at greater depths in the Golden Triangle region and that the formation of the Carlin-type gold deposits is probably linked to the coeval granitic magmatism in the region. This study clearly demonstrates that in situ rutile U–Pb dating is a robust tool for the geochronogical study of hydrothermal deposits that contain hydrothermal rutile.

Supports can widely affect or even dominate the catalytic activity, selectivity, and stability of metal nanoparticles through various metal-support interactions (MSIs). However, underlying principles have not been fully understood yet, because MSIs are influenced by the composition, size, and facet of both metals and supports. Using Ru/TiO 2 supported on rutile and anatase as model catalysts, we demonstrate that metal-support interfacial compatibility can critically control MSI modes and catalytic performances in CO 2 hydrogenation. Annealing Ru/rutile-TiO 2 in air can enhance CO 2 conversion to methane resulting from enhanced interfacial coupling driven by matched lattices of RuO x with rutile-TiO 2 ; annealing Ru/anatase-TiO 2 in air decreases CO 2 conversion and converts the product into CO owing to strong metal-support interaction (SMSI). Although rutile and anatase share the same chemical composition, we show that interfacial compatibility can basically modify metal-support coupling strength, catalyst morphology, surface atomic configuration, MSI mode, and catalytic performances of Ru/TiO 2 in heterogeneous catalysis. Supports can largely affect the catalytic performance of metal nanoparticles, but the underlying principles are not yet fully understood. Here the authors demonstrate that metal-support interfacial compatibility of Ru/TiO 2 can critically control the metal-support interaction modes and the catalytic performances in CO 2 hydrogenation.

New experiments to study titanium solubility in quartz were conducted at conditions not previously explored to extend and improve existing Ti-in-quartz solubility models for thermobarometric applications. Starting materials for experiments included silica glass, anatase, synthetic and natural rutile, Ti-enriched silica gel, Ti-enriched melts, zirconia, and HF and H 2 O fluids. Additional experimental data enabled us to characterize Ti-in-quartz solubility across much of the α- and β-quartz stability fields from 2 to 30 kbar and 550 to 1050 °C. Mutual occurrences of mineral inclusions in one another and Raman spectroscopy of mineral phases confirmed co-crystallization of quartz, rutile, and zircon. Electron microprobe measurements and cathodoluminescence images show that Ti concentrations in quartz crystals from all experiments are relatively uniform, and Ti concentrations of quartz crystals grown at the same experimental conditions using several Ti–rich starting materials and several different growth media are the same within experimental and analytical uncertainties. There are no significant differences in Ti concentrations of quartz across the α–β quartz transition. The Ti concentration in quartz crystals, X TiO 2 quartz , systematically increases with temperature, but the quantity R T ln X TiO 2 quartz is a constant at fixed pressure. The Ti concentration in quartz decreases non-linearly with pressure. To account for the observed P–T dependent changes to Ti in quartz, we developed the Ti-in-quartz solubility model: R T ln X TiO 2 quartz = - 55.287 - [ P kbar ∙ ( - 2.625 + 0.0403 P kbar ) ] + R T ln a TiO 2 rutile where R is the gas constant 0.0083145 kJ/K, T is temperature in Kelvin, P is the pressure in kbar, X TiO 2 quartz is the mole fraction of TiO 2 in quartz, and a TiO 2 rutile is the activity of TiO 2 in the growth media (e.g., fluid, melt) referenced to rutile at standard state conditions of 1 bar and 25 °C. Experiments that co-crystallized quartz, rutile, and zircon permitted us to cross-check thermobarometric results from our Ti-in-quartz solubility models against the widely accepted Zr-in-rutile solubility models. We further tested our Ti-in-quartz solubility models using experiments that co-crystallized quartz, wollastonite, and titanite to fix a TiO 2 rutile < 1. Concentrations of Ti in quartz crystallized from the sub-unity a TiO 2 rutile experiments in the α- and β-quartz fields predict activities that match those calculated using the mineral reaction equilibrium and available thermodynamic data. Demonstrated agreement between calculated and measured experimental P – T conditions using the Zr-in-rutile and Ti-in-quartz solubility models and the consistent reduction of Ti concentrations in systems with a TiO 2 rutile < 1 provide evidence that our experimental results accurately describe the equilibrium solubility of Ti in quartz.

The zirconium-in-rutile thermometer enjoys widespread use, but confidence in its accuracy is limited because experiments were conducted at higher temperatures than many rutile-bearing rocks and calibration uncertainties have not been quantitatively assessed. Refined calibrations were developed using bootstrap regression to minimize residuals in the natural logarithm of the equilibrium constant, based on experiments only ( = 32) and on a combined compilation of experiments and natural data ( = 94, total). Rearranging the regression to solve for , and expressing Zr concentration ( ) in parts per million (μg/g), the calibrations in the α-quartz stability field are:

Several studies have reported the P – T dependencies of Ti-in-quartz solubility, and there is close agreement among three of the four experimental calibrations. New experiments were conducted in the present study to identify potential experimental disequilibrium, and to determine which Ti-in-quartz solubility calibration is most accurate. Crystals of quartz, rutile and zircon were grown from SiO 2 -, TiO 2 -, and ZrSiO 4 -saturated aqueous fluids in an initial synthesis experiment at 925 °C and 10 kbar in a piston-cylinder apparatus. A range of quartz crystal sizes was produced in this experiment; both large and small examples were analyzed by electron microprobe to determine whether Ti concentrations are correlated with crystal size. Cathodoluminescence images and EPMA measurements show that intercrystalline and intracrystalline variations in Ti concentrations are remarkably small regardless of crystal size. The average Ti-in-quartz concentration from the synthesis experiment is 392 ± 1 ppmw Ti, which is within 95 % confidence interval of data from the 10 kbar isobar of Wark and Watson (Contrib Mineral Petrol 152:743–754, 2006 ) and Thomas et al. (Contrib Mineral Petrol 160:743–759, 2010 ). As a cross-check on the Ti-in-quartz calibration, we also measured the concentration of Zr in rutile from the synthesis experiment. The average Zr-in-rutile concentration is 4337 ± 32 ppmw Zr, which is also within the 95 % confidence interval of the Zr-in-rutile solubility calibration of Ferry and Watson (Contrib Mineral Petrol 154:429–437, 2007 ). The P – T dependencies of Ti solubility in quartz and Zr solubility in rutile were applied as a thermobarometer to the experimental sample. The average Ti-in-quartz isopleth calculated from the calibration of Thomas et al. (Contrib Mineral Petrol 160:743–759, 2010 ) and the average Zr-in-rutile isopleth calculated from the calibration of Tomkins et al. (J Metamorph Geol 25:703–713, 2007 ) cross at 9.5 kbar and 920 °C, which is in excellent agreement with the P – T conditions of the synthesis experiment. Separates of the high-Ti quartz from the initial synthesis experiment described above were used as starting material in subsequent experiments at 20 kbar, at which pressure the solubility of Ti in quartz is expected to be significantly lower in the recrystallized quartz. These recrystallization experiments were conducted under wet and dry conditions at 925 °C, and under wet conditions at 850 °C. Both wet and dry recrystallization experiments produced polycrystalline quartzites. Rutile occurs as inclusions in quartz, and as individual crystals dispersed along quartz grain boundaries. Quartz that grew during the recrystallization experiments has dark cathodoluminescence indicating substantially lower Ti concentrations. The average Ti concentrations in quartz from the recrystallization experiments are within the 95 % confidence interval of a linear fit to the 20 kbar data of Thomas et al. (Contrib Mineral Petrol 160:743–759, 2010 ). Collectively, the results from the synthesis and recrystallization experiments confirm that the Ti-in-quartz concentrations used to calibrate the P – T dependencies of Ti-in-quartz solubility in Thomas et al.’s (Contrib Mineral Petrol 160:743–759, 2010 ) calibration represent the equilibrium concentrations of Ti in quartz.

The adsorption of common anions found in water can have a considerable impact on the surface state and optical characteristics of titanium dioxide (TiO2), which has an important impact on the photocatalytic nitrogen reduction reaction (NRR). This work utilizes density functional theory (DFT) computations to examine the electronic and optical characteristics of the TiO2 (001) surface under various anion adsorptions in order to clarify their influence on the photocatalytic NRR of TiO2. The modifications in the structure, optical, and electronic properties of TiO2 before and after anion adsorption are investigated. In addition, the routes of Gibbs free energy for the NRR are also evaluated. The results indicate that the adsorption of anions modifies the surface characteristics of TiO2 to a certain degree, hence impacting the separating and recombining charge carriers by affecting the energy gap of TiO2. More importantly, the adsorption of anions can increase the energy barriers for the NRR, thereby exerting a detrimental effect on its photocatalytic activity. These findings provide a valuable theoretical contribution to understanding the photocatalytic reaction process of TiO2 and its potential application of NRR in the actual complex water phase.

Anatase/rutile mixed-phase TiO2 nanoparticles were synthesized through a simple sol-gel route with further calcination using inexpensive titanium tetrachloride as a titanium source, which effectively reduces the production cost. The structural and optical properties of the prepared materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis adsorption. The specific surface area was also analyzed by Brunauer–Emmett–Teller (BET) method. The anatase/rutile mixed-phase TiO2 nanocomposites containing of rod-like, cuboid, and some irregularly shaped anatase nanoparticles (exposed 101 facets) with sizes ranging from tens to more than 100 nanometers, and rod-like rutile nanoparticles (exposed 110 facets) with sizes ranging from tens to more than 100 nanometers. The photocatalytic activities of the obtained anatase/rutile mixed-phase TiO2 nanoparticles were investigated and compared by evaluating the degradation of hazardous dye methylene blue (MB) under ultraviolet light illumination. Compared to the commercial Degussa P25-TiO2, the mixed-phase TiO2 nanocomposites show better photocatalytic activity, which can be attributed to the optimal anatase to rutile ratio and the specific exposed crystal surface on the surface. The anatase/rutile TiO2 nanocomposites obtained at pH 1.0 (pH1.0-TiO2) show the best photocatalytic activity, which can be attributed to the optimal heterojunction structure, the smaller average particle size, and the presence of a specific exposed crystal surface. The enhanced photocatalytic activity makes the prepared anatase/rutile TiO2 photocatalysts a potential candidate in the removal of the organic dyes from colored wastewater.