Reduction Of Titanium Dioxide Research Articles

Effects of Dissolving Agents on Particle Size Reduction of Titanium Dioxide Synthesized by Solution Combustion Technique

High photocatalytic activity of nanoparticulate titanium dioxide has attracted worldwide attention. Synthesis techniques of the nanoparticles, however, often require high energy supply or costly initial reagents. Solution combustion technique is an energy-effective technique capable of synthesizing nanosized titanium powders. This research aimed at utilizing a less expensive initial reagent in synthesis of nanoparticulate titanium dioxide by the solution combustion technique. The research also examined effects of dissolving agents on chemical composition and particle sizes of the synthesized powders. A low-cost initial reagent, titanium dioxide with average particle size of 154 nanometers, was dissolved in sulfuric acid or dispersed in nitric acid prior to the combustion. Experimental results revealed that the pure anatase phase titanium dioxide was successfully obtained in powders prepared from both sulfuric acid and nitric acid. The average particle size of the powder prepared from sulfuric acid was 77 nanometers, while that of the powder prepared from nitric acid was 117 nanometers. The difference in particle sizes was attributed to solubility of the initial reagent in the acid. Complete solution of initial reagent in sulfuric acid was the main factor attributed to finer particle size.

Synthesis of titanium carbide–carbon nanofibers via carbothermal reduction of titania with carbon

Submicron scale titanium carbide–carbon (TiC–C) hybrid nanofibers have been synthesized from electrospinning of titania (TiO2) nanoparticle and polyacrylonitrile (PAN) in dimethyl formaldehyde (DMF) solution, followed by carbothermal reduction of TiO2 with carbon at high temperature. Scanning Electron Microscope (SEM) images of TiC–C nanofibers show the conservation of fiber morphology after the carbothermal reduction reaction. XRD study demonstrates that the thermal treatment of TiO2–carbon fibers results in the formation of titanium oxycarbide (TiCxOy) crystals and the reduction in the titania phase, and the oxygen content in TiCxOy and the fraction of titania phase decreases with increasing reaction temperature. Transmission Electron Microscope (TEM) images show the loss of the titania phase after the carbothermal reduction. The surface area of TiC–C nanofibers drastically decreases at high reaction temperatures. Finally, it is observed that the electrical conductivity of TiC–C nanofiber mats is higher than that of neat carbon nanofiber mats, and it increases with raising carbothermal reduction temperature.

Concentration and state of light elements in titanium carbide nanopowders

We have studied the effect of process parameters (temperature) in the reduction of titanium oxide with calcium hydride and calcium carbide on the concentrations and state of light elements (H, O, N, C, and S) in the reaction product and identified the oxygen-containing phases present in the titanium carbide (TiC) nanopowders obtained by reducing TiO2 with calcium hydride and calcium carbide. The oxygen present in the powders can be divided qualitatively and quantitatively into oxygen in adsorbed water, oxygen in organic compounds on the surface, and oxygen in the oxide layer on the surface of the carbide nanoparticle. We have performed fractional gas analysis for carbon in the titanium carbide nanopowders and assessed the effect of synthesis temperature on the average particle size and oxygen content of the nanopowders.

Solid–Solid Phase Transformation During the Reduction of Titanium Dioxide (Anatase) to Produce High‐Grade Titanium Powder

Production of titanium is challenging and expensive due to the energy energy‐intensive and time‐consuming processes used at present. Current commercial production method reduces titanium tetrachloride with magnesium or sodium to produce titanium metal. Several researchers have attempted electro‐deposition of titanium from ionic solutions but have faced difficulties in eliminating multivalent titanium ions and highly reactive dendrite products. In this paper, we report, for the first time, the solid–solid phase transformation of titanium dioxide with calcium metal, under suitable conditions, to form solid titanium metal powder (>98% pure) without any oxygen impurity. On phase characterisation, it was found that homogeneous α‐titanium was produced. The paper also includes the results and interpretations obtained using quantitative analysis, X‐ray diffraction (XRD), scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM–EDX) and phase diagram. The process is simple, green, rapid and cheap compared to the existing methods.

Effect of calcination conditions on porous reduced titanium oxides and oxynitrides via a preceramic polymer route.

A preceramic polymer route from Ti-based inorganic-organic hybrid networks provides electroconductive N-doped reduced titanium oxides (TinO2n-1) and titanium oxynitrides (TiOxNy) with a monolithic shape as well as well-defined porous structures. This methodology demonstrates an advantageously lower temperature of the crystal phase transition compared to the reduction of TiO2 by carbon or hydrogen. In this study, the effect of calcination conditions on various features of the products has been explored by adopting three different atmospheric conditions and varying the calcination temperature. The detailed crystallographic and elemental analyses disclose the distinguished difference in the phase transition behavior with respect to the calcination atmosphere. The correlation between the crystallization and nitridation behaviors, porous properties, and electric conductivities in the final products is discussed.

Redox of titanium oxides by methane and water for application to cyclic syngas and hydrogen production systems

Characteristics of TiO2 reduction by methane and re-oxidation by water were investigated at 1223 and 1273 K. The aim of this study was to evaluate the potential of TiO2 as a stable support material for other oxides, such as CeO2 and WO3, which could be used for cyclic production of hydrogen and syngas by methane reforming and water splitting. TiO2 was reduced successively to Ti4O7, Ti3O5, and Ti2O3. During the reduction, methane decomposition to hydrogen and solid carbon occurred slightly from the onset. When the extent of TiO2 reduction (EOR) reached approximately 20%, methane decomposition to hydrogen and solid carbon started to occur significantly. Re-oxidation of the reduced titanium oxides by water splitting was not complete, at 30–80%, and the solid carbon was difficult to remove by water. During repeated cyclic operations, both the EOR and the re-oxidation percentage decreased gradually; one main reason for this is due to the deposited solid carbon. Therefore, TiO2 possesses a great potential as a stable support for redox systems of CeO2 and WO3 that operate at lower temperatures and/or for shorter times.

Reduction of Titanium Oxide by Molten Silicon to Synthesize Titanium Silicide

Reduction of Titanium Oxide by Molten Silicon to Synthesize Titanium Silicide

Effect of exposure to light on the chemical properties of the surface of titania particles obtained by dispersing a rutile crystal in air

It has been found that during exposure to UV light, which is absorbed by titanium dioxide obtained by dispersing a rutile crystal in air, water effectively interacts with the lattice oxygen of the metal oxide with the subsequent release of oxygen into the gas phase in the dark and with the reduction of titanium dioxide.

Direct Electro-deoxidation of Ilmenite Concentrate to Prepare FeTi Alloy in CaCl2 Molten Salt

Abstract In order to prepare FeTi alloy using ilmenite concentrate in molten salt by electrolytic method, the electrochemical deoxidation process was studied by cyclic voltammetry and AC impedance spectroscopy. The electrolytic experiments at different time verified the electrochemical behavior. It is shown that the electrodeoxidation process for ilmenite concentrate mainly consists of two steps. Fe is reduced firstly from the ilmenite concentrate. The second step is the reduction of titanium dioxide with an intermediate product perovskite. At low voltage, the speed of electro-deoxidation process is mainly dependent on the electrochemical reaction. As the potential increases, the diffusion of ion becomes the main rate-controlling step for the electro-deoxidation of ilmenite concentrate.

Low temperature synthesis of reduced titanium oxide nanotube arrays: Crystal structure transformation and enhanced field emission

There are considerable interests in the synthesis of nanostructured reduced titanium oxides because of their attractive properties. In this study, a facile and low-temperature reduction strategy using NaBH4 to yield reduced titanium oxide nanotube arrays is proposed, which significantly lowers the requirements of instruments and costing compared to the conventional strategies. Moreover, this reduction strategy results in the homogeneous crystal structure transformation of parent tetragonal anatase TiO2 nanotube arrays (TNAs) to orthorhombic Ti2.5O3 nanotube arrays with retained morphology, which show sharply improved conductivity and decreased work function. Notably, compared to the pristine TNAs precursor, the obtained Ti2.5O3 nanotube arrays show greatly enhanced field emission (FE) properties including substantially decreased turn-on field from 15.76V/μm to 1.51V/μm, a high current density of 5.00mA/cm2 at an applied field of 4.03V/μm, and an excellent FE stability.

Hierarchically Porous Monoliths Based on N-Doped Reduced Titanium Oxides and Their Electric and Electrochemical Properties

In this report, we demonstrate a novel synthesis method to obtain reduced titanium oxides with monolithic shape and with a well-defined hierarchically porous structure from the titanium-based network bridged with ethylenediamine. The hierarchically porous monoliths are fabricated by the nonhydrolytic sol–gel reaction accompanied by phase separation. This method allows a low-temperature crystallization into Ti4O7 and Ti3O5 at 800 and 900 °C, respectively, with N-doped carbon. These reduced titanium oxides are well-doped with N atoms even under argon atmosphere without NH3, which accounts for the low-temperature reduction. The resultant monolithic materials possess controllable macropores and high specific surface area together with excellent electric conductivity up to 230 S cm–1, indicating promise as a conductive substrate that can substitute carbon electrodes.

Reducción Aluminotérmica del Óxido de Titanio (TiO2) por Plasma de Cátodo Hueco

The production of metallic titanium (Ti) through the reduction of titanium oxide (TiO2) by aluminothermic reduction technique, using hydrogen plasma to trigger the reaction has been investigated. Titanium oxide and aluminum powders were previously processed by high energy grinding during 4, 6 and 10h. Also, a thermal analysis study was done to know the temperature for the aluminothermic process in TiO2-Al mixtures. The product obtained was characterized by X-ray diffraction and scanning electron microscopy and Rietveld method was used in the microstructure refinement. The results show that is possible to obtain a titanium rich compound through the hollow cathode plasma technique.

SHS - Processes in the Carbonaceous Oxide System at High Nitrogen Pressure Values

<p>This paper contains study results of the nitride containing composites features formed in the compacted Al-TiO<sub>2</sub>-C-Si samples inside a high pressure reactor with various nitrogen pressure values. The nitriding and carbide-formation processes take place simultaneously with aluminothermic reduction of titanium oxide in the self-propagating high-temperature synthesis (SHS) mode. It has been found that the nitrogen pressure effect is manifested as insignificant reduction of the combustion temperature and increased durability of the synthesized composite. The SHS process in the nitric environment leads to practically complete reduction of titanium oxide, the free titanium being absent. The X-ray analysis has revealed that the basic SHS products are refractory compounds such as metal nitrides, carbides, and oxides. Increase in nitrogen pressure results in decrease of the specific electric resistance of the synthesized composites caused by growth of the electroconductive phases i.e. titanium carbides, nitrides, and silicides. Performed electron microscopic study including the energy dispersion analysis of the morphology and structure of the SHS products has revealed formation of the nano-sized titanium silicide crystals distributed between the complex carbonitride particles. The complex carbonitride composites synthesized in the high pressure reactor are of interest as highrefractory and abrasive materials considering their physical and chemical properties.</p>

Reduction of Ilmenite with Coal in the Presence of Nitrogen

In this study, the carbothermal reduction of ilmenite with coal was investigated in laboratory-scale experiments. Reactions were performed in nitrogen atmospheres in the temperature range of 1,225–1,325°C with a residence time of 6 h. The solid reaction products obtained in the investigation were characterised by ICP-EOS and LECO analysers, X-ray diffraction, and scanning electron microscope (SEM). The results show that temperature increase leads to an increase of reduction degree for constant bed depth but the reduction degree decreases with increase of bed depth. The reduction degree of 42.2% was obtained with a bed depth of 25 mm, at 1,350°C after 6 h of residence time. The reaction started with the reduction of ilmenite to titania, followed by the reduction of titania to suboxides. Titania was reduced to Ti3O5, which was later converted to titanium nitride or titanium oxycarbonitride depending on element reactivity and temperature. It was found that Ti2O3 does not appear as an intermediate reaction product due to its instability.

Topotactic Reduction Yielding Black Titanium Oxide Nanostructures as Metallic Electronic Conductors

Detailed analyses of reduced, single crystal, rutile-type TiO(2) via high-resolution transmission electron microscopy (TEM) are reported which reveal that the reduction proceeds topotactically via interstitial diffusion of Ti ions at low temperature, around 350 °C. This important finding encouraged the production of various nanostructured reduced titanium oxides from TiO(2) precursors with morphology retention, and in the process, the synthesis of black titanium oxide nanorods using TiO(2) nanorods was demonstrated. Interestingly, as opposed to the semiconductive behavior of Ti(2)O(3) synthesized at high temperature, topotactically synthesized Ti(2)O(3) exhibits metallic electrical resistance, and the value at room temperature is quite low (<6 μΩ m, comparable to graphite). These unique properties are probably due to the lattice strains generally observed for topotactically synthesized Ti(2)O(3). This work shows that topotactically reduced titanium oxides can have fascinating properties as well as nanostructures.

Analysis of titanium reduction in a blast furnace

By combined study of heat-transfer and reduction processes, the factors that determine the blastfurnace reduction of titanium oxides are analyzed.

Facile synthesis of nanostructured reduced titanium oxides using borohydride toward the creation of oxide-based fuel cell electrodes

A facile, low-temperature reduction method using sodium borohydride to yield corundum-type Ti(2)O(3) nanorods from rutile-type TiO(2) nanorods with morphology retention is proposed. The electrochemical analyses confirmed their promising performance as electrodes and excellent stability to the environment of interest for fuel cell operation.

Microwave Synthesis of Nano-Titanium Carbide

A new synthesis technology of titanium carbide with microwave is introduced in this article. Microwave synthesis technology is a fast and relatively low temperature of synthesis method. Nano-titanium carbide powders were synthesized by carbothermal reduction of titanium dioxide and carbon black with the microwave synthesis method at 1100°C-1400°C in argon gas atmosphere. Nano-TiO2powder and carbon black were used as raw materials. The TiC powders were characterized with the XRD and TEM. The experimental results show that the synthesis rate is quick, even at relatively low synthesis temperature. The average particle size of the TiC powders synthesized by the microwave synthesis technology under low temperature (&lt;1300°C) is less than 50nm, and the average particle size augments with increasing the microwave synthesis temperature and time.

Synthesis of Nanostructured Reduced Titanium Oxide: Crystal Structure Transformation Maintaining Nanomorphology

There is an increasing need for the synthesis of nanostructured reduced oxides because of their attractive properties; for example, compared with titanium dioxide (TiO2), reduced titanium oxides are attractive for photovoltaics, photocatalysts, and fuel cells owing to their narrow band gap enabling absorption of visible light, chemical stability, and relatively high electrical conductivity, comparable to that of graphite. Generally, reduced titanium oxides have been synthesized by 1) thermal reduction of TiO2 at about 1000 8C with H2 gas or Ti powder, 2) photochemical reduction of TiO2 with UV laser irradiation, or 3) direct synthesis from unique precursors or using laser ablation techniques. These reductive techniques in turn cause particle growth or compositional inhomogeneity, making it difficult to obtain high-quality nanostructures. Ti4O7 and Ti8O15 nanowires were synthesized by annealing H2Ti3O7 nanowires in a hydrogen atmosphere. [2] These nanostructures seem the most sophisticated reported so far; however, particle growth is inevitable and the method seems to be inapplicable to other nanostructures. Since nanostructures are of significant importance for exploiting reduced titanium oxides, development of novel techniques for synthesizing them on the nanoscale is needed. Herein we report a novel method for synthesizing nanostructured reduced titanium oxides by reducing nanostructured TiO2 with a strong reducing agent at much lower temperatures than in conventional techniques. Interestingly, nanostructured reduced titanium oxide with the same morphology as its precursor was obtained, though its crystal structure was transformed from the tetragonal to the hexagonal system. The synthesis is applicable to other nanostructured titanium dioxides, and thus opens up fascinating possibilities for designing nanostructures of reduced titanium oxides for a wide range of applications. We chose TiO2 nanoparticles with rutile structure (tetragonal, P42/mnm), which is a high-temperature phase obtained above about 800 8C and irreversibly stable at room temperature, as precursor. The as-received TiO2 nanoparticles were thoroughly mixed with a fourfold molar excess of CaH2 powder, and then heated at 350 8C for 15 d. Low-temperature reduction with binary metal hydrides was first demonstrated by Hayward et al., who used solid NaH as a reducing agent to topotactically synthesize infinite-layer LaNiO2 from perovskite LaNiO3. [11] Since then, alkali and alkaline earth metal hydrides such as CaH2 and LiH have been employed by Hayward et al. and others to obtain unprecedented reduced phases inaccessible by conventional reduction techniques. The powerful reducing activity even at low temperatures of such binary metal hydrides was expected to enable us to synthesize nanostructured reduced titanium oxides from nanostructured TiO2. The final product was a black powder (see Figure 3), which is typical for reduced titanium oxides. Figure 1 compares the synchrotron powder X-ray diffraction (SXRD) patterns of the rutile TiO2 precursor and the reduced product. After reduction, SXRD patterns significantly changed; all major peaks of the product were readily

Characterization of Pt–Au and Ni–Au Clusters on TiO2(110)

The surface composition and properties of Pt–Au and Ni–Au clusters on TiO2(110) have been studied by scanning tunneling microscopy (STM), low energy ion scattering (LEIS) and soft X-ray photoelectron spectroscopy (sXPS). STM studies show that bimetallic clusters are formed during sequential deposition of the two metals, regardless of the order of deposition. At the 2 ML of Au/2 ML of Pt or Ni coverages studied here, the second metal contributes to the growth of existing clusters rather than forming new pure metal clusters. LEIS experiments demonstrate that the surfaces of the bimetallic clusters are almost 100% Au when 2 ML of Au is deposited on top of 2 ML of Pt or Ni. However, a much larger fraction of Pt or Ni (50 and 20%, respectively) remains at the surface when 2 ML of Pt or Ni is deposited on 2 ML of Au, most likely due to limited diffusion of atoms within the clusters at room temperature. According to sXPS investigations, the binding energies of the metals in the bimetallic clusters are shifted from those observed for pure metal clusters; the Pt(4f7/2) and Ni(3p3/2) peaks are shifted to lower binding energies while the position of the Au(4f7/2) peak is dominated by surface core level shifts. Pure Pt clusters as well as 0.4 ML of Au on 2 ML of Pt clusters reduce the titania support upon encapsulation after annealing to 800 K, whereas 2 ML of Au on 2 ML of Pt clusters do not reduce titania, presumably because there is no Pt at the surface of the clusters. Pure Ni clusters are also known to become encapsulated upon heating, but the reduction of titania is much less extensive compared to that of pure Pt clusters.