Vanadium Titanium Research Articles

Strain aging of titanium–vanadium ultralow carbon strip steels

Laboratory casts of titanium stabilised and titanium–vanadium dual stabilised ultralow carbon (ULC) steel have been assessed to determine their strain aging properties. A retarding effect on strain aging resulting from vanadium microalloying addition in Ti–V ULC strip steels is identified, and the activation energies for strain aging in Ti stabilised and Ti–V stabilised ULC steels are shown to differ.

Synthesis of doubly functional nanowhiskers from a colloid solution including a V–Ti complex precursor

In this study, we synthesized vanadium (V) nanoparticles precursor (NH4)5[(VO)6(CO3)4(OH)9]·10H2O a two-phase system of toluene and water. Colloid solution including titanium(IV) isopropoxide and polyvinylpyrrolidone (PVP) was subsequently deposited onto the nanoparticles to form urchin-like structures in a toluene solution as the vanadium–titanium (V–Ti) complex precursor. Calcining the urchin-like precursor at 700 °C generated nanowhiskers of the Ti/V oxide complex after annealing process. These nanowhiskers were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron microscopy (XPS). Films of the Ti/V oxide nanowhisker structure exhibited good visible transparency and a large change in transmittance at near-infrared (NIR) wavelengths before and after the metal–insulator phase transition. For a 44-nm-thick single-layer nanowhisker thin film, the transmittances at 700 nm in the metallic (M) and semiconductive (S) states were 75 and 72.2 %, respectively; the NIR switching efficiency (ΔT2000) increased from 17 to 21.3 % at 2000 nm under UV light irradiation. In addition, the nanowhisker thin film of the Ti/V oxide complex significantly enhanced the photodecomposition of methylene blue under UV irradiation, relative to that of the unmodified TiO2. The dual functions of this material—thermochromicity and photocatalytic behavior—suggest that it might have interesting applications in energy-saving smart windows.

Template-Free One-Pot Synthesis of Porous Binary and Ternary Metal Nitride@N-Doped Carbon Composites from Ionic Liquids

Herein we present a straightforward synthesis approach toward composites of titanium, vanadium, and titanium–vanadium nitride nanoparticles embedded in nitrogen-doped carbon. These materials can be easily prepared via the heat treatment of mixtures of the corresponding metal precursors TiCl4 or VOCl3 dissolved in the ionic liquid 1-butyl-3-methyl-pyridinium dicyanamide (Bmp-dca) as the nitrogen/carbon source. WAXS diffractograms and TEM pictures of the resulting materials reveal the presence of highly crystalline metal nitride nanoparticles with an average diameter of 5 nm embedded in a graphitic carbon matrix. XPS measurements show that the carbon network is heavily doped with nitrogen; that is, it can be described as a nitrogen-doped carbon. Nitrogen sorption measurements show type I isotherms indicative of mainly microporous composites. The specific BET surface area increases with increasing amount of the metal precursor, and it is also dependent on the respective metal ion used. Under similar syntheti...

Influence of TiO2 and basicity on viscosity of Ti bearing slag

The viscosities of CaO–SiO2–7MgO–TiO2–12Al2O3 (wt-%) slags (CaO/SiO2 = 0·5–0·9, wt-% TiO2 = 15–30) were investigated to promote understanding of the effect of TiO2 and basicity (CaO/SiO2) on the viscous behaviour of slags containing TiO2. In practice, these experimental results are significant for the blast furnace (BF) processing of vanadium–titanium magnetite ore and for controlling the selective crystallisation of Ti bearing BF slags. The slag viscosity was found to decrease with increasing TiO2 content at a fixed basicity. The degree of viscosity decrease with increasing TiO2 content diminishes in the slag with higher basicity or higher TiO2 content. An increase in the basicity lowers the viscosity of slags. The apparent activation energy of viscous flow of slags decreased with additions of TiO2 and increasing basicity. The Urbain model was empirically modified based on the present experimental data, which can be used to predict not only quinary Ti bearing slags but also quaternary and low Ti bearing slags.

Topology of silica supported vanadium–titanium oxide catalysts for oxidative dehydrogenation of propane

Two-dimensional vanadia and titania surface clusters were hosted on the walls of the hierarchical pore system of mesoporous silica SBA-15. The topology of the catalyst surface was varied by sequential grafting of vanadium and titanium alkoxides generating an extended library of mixed (VOx)n–(TiOx)n/SBA-15 catalysts. The surface of the catalysts was analyzed by FTIR, UV-vis, Raman, and NEXAFS spectroscopy. Electron microscopy, X-ray fluorescence, X-ray diffraction, and nitrogen adsorption have been applied to characterize chemical composition, micro- and meso-structure of the materials. Segregation of nano-crystalline vanadia and titania particles was excluded by UV-vis, Raman and NEXAFS spectroscopy. Monolayer coverage of titanium oxide surface species has been achieved in the range between 17 and 19 wt% Ti loading corresponding to 6–8 Ti atoms per nmcat2 and Si/Ti ratios between 3.3 and 2.8. Up to a critical total metal loading, vanadia is grafted on both the silica surface and surface titania species yielding tetrahedrally coordinated vanadium oxo-species characterized by low nuclearity and moderate catalytic activity. A volcano-type dependency with respect to the propylene space-time yield has been observed in the oxidative dehydrogenation of propane. The maximum in productivity of propylene is attributed to a particular surface topology that is characterized by (VOx)n islands embedded in a matrix of dispersed titania species forming an almost complete combined vanadia–titania monolayer on the silica surface.

Kinetic study of the reaction of vanadium and vanadium–titanium oxide cluster anions with SO2

The reactivity of mass-selected V(4)O(10)(-) cluster anions towards sulphur dioxide is investigated in an ion trap under multi-collision conditions. Gas phase reaction kinetics are studied as a function of temperature (T(R) = 150-275 K). The binding energy of SO(2) to V(4)O(10)(-) is obtained by analyzing the experimental low pressure rate constants, employing the Lindemann energy transfer model for association reactions in conjunction with statistical RRKM theory. In addition, infrared multiple photon dissociation spectroscopy is used in conjunction with density functional theory for the structural assignment of the [V(4)O(10)(-), SO(2)] complex, revealing a square pyramidal structure with the SO(2) molecule incorporated in the vanadium oxide framework. Energy profiles are calculated for the reaction between V(4)O(10)(-) and V(6)O(15)(-) with SO(2). Whereas the transition structures along the reaction pathway of V(4)O(10)(-) with SO(2) have energies below those of the separated partners, the reaction of V(6)O(15)(-) with SO(2) proceeds via a transition structure with energy higher than the educts. The role of cluster size and composition is investigated by studying the reaction kinetics of larger (V(6)O(15)(-) and V(8)O(20)(-)) and titanium doped (V(3)TiO(10)(-) and V(2)Ti(2)O(10)(-)) vanadium oxide clusters with SO(2). The observed cluster size and composition dependencies are discussed.

Electro-catalytic oxidative cleavage of lignin in a protic ionic liquid

Lignin is a component of lignocellulosic biomass and a promising matrix for recovering important renewable aromatic compounds. We present a new approach of electro-oxidative cleavage of lignin, dissolved in a special protic ionic liquid, using an anode with particular electro-catalytic activity. As appropriate ionic liquid triethylammonium methanesulfonate was identified, synthesised, explored for dissolution of alkali-lignin and used for electrolysis of 5 wt.% lignin solutions. As appropriate anode material, oxidation-stable ruthenium-vanadium-titanium mixed oxide electrodes were prepared and explored for their electro-catalytic activity. The electrolysis was performed at several potentials in the range from 1.0 V to 1.5 V (vs. an Ag pseudo reference electrode). A wide range of aromatic fragments was identified as cleavage products by means of GC-MS and HPLC measurements.

A HYSCORE investigation of bimetallic titanium–vanadium microporous catalysts: elucidating the nature of the active sites

Vanadium and titanium bimetallic AlPO-5 molecular sieves have been synthesized and characterized by means of Electron Spin Echo detected EPR and Hyperfine Sublevel Correlation (HYSCORE) spectroscopy. Direct evidence for framework substitution of redox-active Ti ions and VO(2+) units at Al sites is provided through the detection of large (31)P hyperfine couplings.

The reactivity of titanium–vanadium containing groups in the synthesis of two-component monolayers on silica surfaces

The coating of silica surfaces with two-component VOCl 3 and TiCl 4 monolayers was studied with respect to the composition of the products and the kinetics of interaction. The titanium and vanadium-containing groups were found to be able to replace each other equivalently. Surface sites were found to determine reactivity, as were lateral interactions in the monolayer. The results found the presence of two kinds of active center; with the estimated ratio of such groups correlating with data from chemical analyses of the concentrations of groups covalently linked to the surface by different numbers of bonds.

Characterisation of ternary Ti xV 1− xN y nitride prepared by mechanosynthesis

In the present manuscript the authors have systematically investigated the composition and microstructure of a series of ternary nitrides (Ti x V 1− x N y ) (0.0 ≤ x ≤ 1.0) prepared by mechanosynthesis, using XRD, SEM, EELS, XAS and TGA. The ternary titanium–vanadium nitride (Ti x V 1− x N y ) has been obtained in all range of compositions by the mechanical treatment of the two metals under nitrogen pressure in a planetary mill with a maximum milling time of 3 h and without any post-heating treatment. The materials’ microhardnesses were measured after sinterisation and compared to those reported in the literature for these types of materials. When compared with the previously reported data for bulk samples, these values are similar or higher for compositions within the range x = 0.5 to x = 0.77 (Ti x V 1− x N).

Photocatalytic activity of predominantly rutile mixed phase Ag/TiV oxide nanoparticles under visible light irradiation

Nanoscale synthesis of silver sensitized titanium vanadium mixed-metal (Ag/TiV) oxides was done employing sol–gel technique. The physico–chemical properties of the material were examined using XRD (X-ray diffraction), SEM (Scanning Electron Microscopy), EDAX (Energy Dispersive X-ray Spectroscopy), HR-TEM (High Resolution Transmission Electron Microscopy), XPS (X-ray Photoelectron Spectroscopy), UV-DRS and Photoluminescence analysis (PL). The results indicated the presence of predominantly rutile mixed phase particles of 20–30 nm grain size. Identically prepared TiV as well as Ag/TiV oxide catalyst showed enhanced and extended visible light absorption with an absorption upper limit, λ ≥ 550 nm. The visible light photocatalytic activity of Ag/TiV oxide showed an increase of about three and seven times compared to TiV oxide and Degussa P25 respectively, in the rate of degradation of phenol. The reason for the enhanced visible light activity of Ag/TiV oxide may be ascribed to elevated and extended absorption due to combined effect of dopant induced band gap reduction and visible light induced surface plasmon resonance of the Ag nanoparticles. The photocatalytic activity is complemented by localized charge traps and Ag assisted charge separation in the system as well.

Enhanced visible light photocatalytic disinfection of gram negative, pathogenic Escherichia coli bacteria with Ag/TiV oxide nanoparticles

Silver sensitized titanium vanadium mixed Ag/TiV oxide photocatalyst was synthesized using sol-gel technique. The catalyst was characterized using XRD, SEM, EDAX, HRTEM, UV-DRS, XPS, and PL analysis which reveal the formation of a predominantly rutile mixed phase nanoparticles of 25-30 nm crystallite size. The catalyst showed a marked red-shift in the absorption spectrum compared to Degussa P25. It exhibited a remarkable enhancement in the visible light photocatalytic activity in inactivating Escherichia coli, a gram-negative pathogenic bacterium, too. The conclusions are supported by a comparison with an identically synthesized TiV oxide sample. A microbicidal photonic efficiency (MPE) has been defined and a method for its determination has been proposed to facilitate quantification of the performance of the photocatalyst and the disinfection system taking into account the response of the catalyst to the radiation intensity.

An electrochemical and theoretical comparison of ionic transport through a polystyrene based titanium–vanadium (1:2) phosphate membrane

Ionic potentials were measured across polystyrene based titanium–vanadium (1:2) phosphate membranes with 1:1 electrolytes at different concentrations. These observed values are found to compare well with membrane potentials calculated from theoretical equations derived by Teorell–Meyer–Sievers (TMS). Membrane parameters have been used to examine the validity of the theory utilized. The observed values of membrane potentials have been found to decrease with an increase of electrolyte concentration and follow the sequence Li + > Na + > K + and are potentials all positive. This shows that the membrane is cation-selective. The ion mobilities of electrolytes are significantly affected by groups of fixed charge in the membrane. The distribution coefficient values were observed to diminish with increasing electrolyte concentration and follow the sequence KCl > NaCl > LiCl. The values of fixed charge density and charge effectiveness obtained by this simple method are in good agreement with those reported in literature. The charge effectiveness values are found to increase with the hydration radii of the electrolytes.

Synthesis and magnetic properties of M0.08Ti0.91V0.09O2 + δ · nH2O (M = Cr, Mn, Fe, Co, Ni) nanopowders

Using sol-gel synthesis and ion exchange, we have prepared titanium vanadium oxide nanopowders doped with transition-metal ions: M0.08Ti0.91V0.09O2 + δ · nH2O with M = Cr, Mn, Fe, Co, and Ni. The valence state of the ions in the nanopowders and their morphology and structure have been studied by scanning electron microscopy, X-ray diffraction, IR spectroscopy, and X-ray photoelectron spectroscopy. The MxTi0.91V0.09O2 + δ · nH2O oxides dried in air or calcined at 400°C in air are shown to be paramagnets. Vacuum annealing of Co0.08Ti0.91V0.09O2 + δ · nH2O at 700°C gives rise to a significant ferromagnetic contribution.

A Carbon/Titanium Vanadium Nitride Composite for Lithium Storage

Lithium-ion batteries: Improved performance of lithium storage using titanium vanadium nitride and carbon hybrid composites (see TEM images of solid-solution composites) as anode materials for lithium batteries, is demonstrated. These prove to be desirable candidates for the next-generation lithium batteries and supercapacitors.

Visible active silver sensitized vanadium titanium mixed metal oxide photocatalyst nanoparticles through sol–gel technique

Silver sensitized titanium vanadium mixed metal (Ag/TiV) oxides were prepared by nanoscale synthesis route employing the sol–gel technique. It led to the development of 5–20 nm particles with predominantly anatase phase. The physicochemical characterization of the particles was done by X-ray diffractrometry (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence spectroscopy (PL). The reflectance spectrum shows a red shift in the optical response of the catalyst with its band gap absorption upper limit covering a large portion of the visible spectrum, i.e. λ abs ≥700 nm. The performance of the materials was examined under laboratory visible light and solar radiation exposure. The rate of degradation of methylene blue (MB) and phenol exhibited an increase of about six and four times, respectively, in visible light compared to Degussa P-25. This may be attributed to the increased absorption due to Ti–V mixed metal oxides, favorable electron transfer in the anatase–rutile mixed phase coupled with silver’s scavenging action and reduced electron–hole recombination thereon.

Geotectonic setting and metallogeny of the northern São Francisco craton, Bahia, Brazil

Abstract This paper aims at establishing a tectonic and temporal framework to characterize the metallogenic processes that contributed to the origin of the mineral provinces in the northern Sao Francisco Craton. Many Archean mineralizations (eg. massive sulfide zinc, lead, zinc and copper, besides magnesite–talc, iron–titanium–vanadium, iron, chromite and manganese) were generated before the assembly of the Craton. Deposits of chromite, nickel, gold and emerald were produced during the Paleoproterozoic orogenic cycle, when the Craton was amalgamated into the Atlantica paleocontinent. An extension event is recorded in the Neoproterozoic, during the breakup of Rodinia, associated with deposits of phosphorite and uranium. Kimberlite diamond and gold mineralization were generated during the Brasiliano orogenic cycle, coeval with the amalgamation of West Gondwana. A long-lasting and rather uniform crustal stress is recorded in the area during the Cambrian period. Resetting of the isotopic and magnetic systems that affected the Neoproterozoic sediments of the Irece Basin at about 520 Ma was attributed to the regional-scale fluid migration and mineralization in the aftermath of the Brasiliano orogenic cycle.

On the origin of electrical relaxation in tellurite glasses

The dielectric properties of ternary silver vanadium tellurite and titanium vanadium tellurite glasses of the form [0.5[xAg2O-(1−x)V2O5]–0.5TeO2, x=0.1–0.8mol] and [0.5[xTiO2-(1−x)V2O5]–0.5TeO2, x=0.1–0.6mol] are investigated as a function of frequency (10Hz–1MHz) and temperature (70–425K). Electrical relaxation is analyzed in terms of dielectric modulus and Kohlrausch–Williams–Watts (KWW) stretched exponential distribution function. The composition dependence of the stretched exponential parameter (β) is explained according to the variation of activation energy for dc conductivity and inter-charge separation in the two glass series. From the transition of polaronic to ionic conduction in silver vanadium tellurite glass series, it is established that ion–ion correlations are more effective in slowing down the electrical relaxation than the interactions between electronic charge carriers.

The decolorization of Acid Orange II in non-homogeneous Fenton reaction catalyzed by natural vanadium–titanium magnetite

The catalytic activity of natural vanadium–titanium magnetite was investigated in the decolorization of Acid Orange II by non-homogeneous Fenton process. The natural catalysts purified by magnetic separation were characterized using X-ray diffraction (XRD), polarizing microscope, X-ray absorption fine structure (XAFS) analysis and Mössbauer spectroscopy. The obtained results show that the natural samples after magnetic separation mainly contain titanomagnetite, with a small amount of ilmenite and chlorite. Titanomagnetite is doped with vanadium, whose the valency is mainly +3 and occupies the octahedral site. Batch decolorization studies were performed to evaluate the influences of various experimental parameters like initial pH, the amount of catalyst and initial concentration of hydrogen peroxide on the decolorization efficiency of Acid Orange II. The decolorization of the dye mainly relied on degradation. The degradation efficiency was strongly dependent on pH of the medium where it increased as the pH decreased in acid range. The increase of catalyst and hydrogen peroxide could accelerate the degradation. The catalytic property of natural vanadium–titanium magnetite in the degradation of Acid Orange II was stronger than that of synthetic magnetite (Fe 3O 4). The catalytic activity of the natural samples was greatly related to the titanomagnetite content. The degradation process was dominated by heterogeneous Fenton reaction, complying with pseudo-first-order rate law. The natural catalyst has a good catalytic stability.

Hydrogen-Induced Cracking in GMA Welds of Vanadium–Titanium Microalloyed High Strength Steel

High strength low alloy (HSLA) steels are developed to provide better strength, toughness, and improved weldability. These steels are often used as better alternatives for quenched and tempered steels due to the excellent combination of these properties. The beneficial properties in these steels are achieved by careful control of composition and by adopting suitably controlled thermomechanical processing (TMCP). Improved weldability is achieved by maintaining carbon at lower level. To compensate the effect of carbon, small amounts of alloying elements, such as niobium, vanadium, titanium, aluminium, and nitrogen are added. Though these steels have good weldability, they suffer from hydrogen induced cracking especially at high strength levels. In the present study, hydrogen induced cracking susceptibility of a newly developed indigenous vanadium–titanium microalloyed high strength steel was evaluated by means of implant cracking test. Welding was carried out using the GMAW process at different heat input levels. It was found that the coarse-grained heat affected zone (CGHAZ) of the steel is prone for hydrogen induced cracking at lower heat inputs. The implant test results indicated that the critical stress level increases with increasing heat inputs. The results were correlated with the microstructural modifications that occur in the CGHAZ at different welding conditions. The microhardness variations in that region were in good agreement with the observed results.