Oxidation State Of Titanium Research Articles

Controlled potential coulometric method to determine the average titanium oxidation state of titanium chlorides in sodium chloride

A controlled potential coulometric method based on an Fe 2+ /Fe 3+ couple has been developed which, when coupled with the total Ti content determined by a separate analysis, is useful for calculating the average Ti oxidation state in a sodified NaCl sample

A 2MoTiO 7− x (Arare earth or Y): a new series of oxide pyrochlores prepared by topochemical reduction of A 2MoTiO 8 scheelites

A series of anion-deficient pyrochlore oxides of the formula A 2MoTiO 7− x ( x⩽0.5), where ASm, Gd, Tb, Dy, Ho, Er, Lu and Y, has been prepared by reduction of A 2MoTiO 8 scheelites. The scheelite-to-pyrochlore conversion is reversible, indicating that the reaction is likely to be topochemical. The oxidation states of molybdenum and titanium are most probably Mo (III) and Ti (IV) for the limiting composition of the pyrochlores A 2MoTiO 6.5. The new pyrochlores are non-metallic and paramagnetic as expected.

Oxide properties of a γ-TiAl: a surface science study

The surface properties of oxides grown on a γ-TiAl (2 at.% Nb) have been examined using X-ray photoelectron spectroscopy and secondary ion mass spectroscopy. An oxide formed on the sample during air exposure at room temperature was thermally destabilized in ultrahigh vacuum. The heating largely decomposed the advanced titanium oxidation states to give a dominant +2 valence configuration at 600 °C, while the aluminum oxide was somewhat enhanced for the same treatment. Growth of a post chemisorption oxide for various temperatures and exposure times at or below a pressure of 10 −6 Torr oxygen revealed the progressive development of titanium and aluminum oxide. At a temperature of 600 °C the titanium component was greatly enhanced relative to the aluminum content in the surface region. This separation of titanium from aluminum was clearly visible in SIMS measurements. The development and thermal stability of these oxides is in agreement with the heats of formation and available valence states for the two majority components in the material.

Mixed oxidation states of titanium at the metal-oxide interface.

A theoretical model has been developed to explain the XPS data for the mixed oxidation states of Ti (Ti 2+, Ti 3+, Ti 4+) observed in the Ti-O 2, Ti-CO and Ti-NO interactions. The Ti/TiO hetero-junction, as well as the mixed overlayers TiO/Ti 2O 3/TiO 2 have been found to be thermodynamically stable, in comparison to TiO 2, accounting for the absence of the Ti 4+ species at the metal interface. For the Ti-NO and Ti-CO systems, kinetic arguments have been shown to account for the titanium oxidation states across the oxide layer.

High activity magnesium chloride supported catalysts for olefin polymerization. XXIX. Molecular basis of hydrogen activation of magnesium chloride supported Ziegler–Natta catalysts

AbstractHydrogen (pH2 = 72 torr) increases the rate of propylene polymerization by a MgCl2/ethyl benzoate/p‐cresol/AlEt3/TiCl4‐AlEt3/methyl‐p‐toluate catalyst (CW‐catalyst) by two‐to three‐fold which corresponds closely with the increase in the number of active sites as counted by radiolabeling with tritiated methanol. The oxidation states of titanium in decene polymerizations by the CW‐catalyst were determined as a function of time of polymerization (tp). In the absence of H2, all [Ti+n] for n = 2, 3, 4 remain constant during a batch polymerization. In the presence of H2 and within 5 min of tp, [Ti+2] decreases by an amount, corresponding to 15% of the total titanium and [Ti+3] increases by the same amount, while [Ti+4] is not changed. Therefore, three‐fourths of the H2 activation result from oxidative addition processes. The remaining one‐fourth of the H2 activation may be attributed to the activation of previously deactivated Ti+3 ions by hydrogenolysis. Monomer converts some of the EPR silent Ti+3 sites to EPR observable species resulting in their activation.

Monomer‐isomerization polymerization, 27. Monomer‐isomerization in competition with polymerization of α‐olefins with Ziegler‐Natta catalysts

AbstractThe monomer‐isomerization was studied in the polymerization of α‐olefins with the catalytic systems TiCl3/(C2H5)3Al and Ti(OC4H9)4/(C2H5)3Al. The isomerization to the corresponding olefins with internal double bond was found to occur during the polymerization. With the system TiCl3/(C2H5)3Al only a small amount of isomerized olefin was produced as result of the rapid polymerization of the α‐olefins. Significant isomerization was observed to take place with a poor polymerization catalyst such as Ti(OC4H9)4/(C2H5)3Al. Isomerization and polymerization of α‐olefins with Ziegler‐Natta catalysts were found to depend on the oxidation state of titanium.

Dissociative chemisorption and localized oxidation states at titanium surfaces

Dissociative chemisorption of carbon monoxide and nitric oxide is shown to result in the formation of discrete localised oxidation states of titanium; Ti 2+ with CO and Ti 2+ and Ti 3+ with NO. The results are compared with dioxygen (Ti 2+, Ti 3+ and Ti 4+). A correlation is shown to exist between the extent of dissociative chemisorption i.e. overlayer growth and the emergence in a step-wise manner of Ti 2+, Ti 3+ and Ti 4+. Attention is drawn to the significance of the Madelung energy in determining the oxidation states generated within the overlayer by this molecule-specific process.

Intercalation in 3D-Skeleton Structures : Ionic and Electronic Features

AbstractThe voltage of an electrochemical cell, i.e. the difference between the chemical potentials of the two electrodes, may play the role of a sensor which allows to display the structural modifications and the physical properties. The electrochemical processes involved in an alkali metal (A) intercalation electrode emphasize the influence of the ionic and/or electronic features. The A+-lattice and A+-A+ interactions as well as electronic band-filling may lead to phase transitions or even limit the intercalation reaction.The shape of the cell voltage vs. intercalation rate curve depends on the number of vacant sites available for intercalation, the number and the oxidation state of the reducible cations, the band structure of the material and the covalency of the framework.Alkali ion intercalation in 3D-structures related to perovskite (Ln⅓ NbO3), hexagonal tungsten bronze (LiW3O9F) and Nasicon-type (AM2 (PO4)3) is discussed from that point of view.In Ln⅓NBO3 (Ln = La, Nd) (i.e. ▭ ½Ln⅓ ▭, ⅙NbO3) L1+-intercalation in various sites is related to the rare earth size.Two extra lithium atoms can be introduced into LiW3O9F in which four sites are available, but only one out of two is occupied in order to reduce the electrostatic interactions. Moreover the change in the discharge curves can be associated to the modifications with intercalation rate of the Li+-lattice interactions.Within the Nasicon derived structures of ATi2 (PO4)3 and Fe2 (MoO4)3 the intercalation process is limited by the lowest stable oxidation state of titanium or iron. In both systems the strong electronic localization leads to formation of large two phase-domains.The relevance of using 3D-intercalation electrodes in electrochemical power batteries will be discussed as far factors such as electrical behavior or absence of significant unit cell modifications of the positive electrodes during the intercalation process are essential for many cycle utilizations.

Magnesium chloride supported catalysts for olefin polymerization. XIX. Titanium oxidation states, catalyst deactivation, and active site structure

AbstractA precise method for the determinations of Ti+2, Ti+3 and Ti+4 was developed. The CW‐procatalyst before activation contains mostly Ti+4 ions with 6% Ti+3 and 4% Ti+2 ions. Activation with AlEt3 alone at room temperature reduced all the titaniums to lower valence states consisting of 71% Ti+3 and 29% Ti+2. Reduction is incomplete when methyl‐p‐toluate was present as external Lewis base during activation: at 25°C the distribution of Ti+4 : Ti+3 : Ti+2 is 36% : 25% : 38%; the distribution at 50°C is 37% : 22% : 40%. Aging of the activated catalyst caused little or no changes in the distribution of [Ti+n]; whereas the catalytic activity decays rapidly with aging. The aged catalysts have polymerization activity comparable to the decreased activity of the catalyst during a polymerization. The [Ti+n] was determined for the CW‐catalyst during the course of a decene polymerization; they were found to be Ti+4 : Ti+3 : Ti+2 = 30% : 27% : 43%, which did not change with polymerization time. These results suggest that the reducibility of Ti+4 species by AlEt3 or 3AlEt3/MPT to different valence states is predicated by their structures. These species do not undergo further changes in their oxidation states during either aging or polymerization. Their decays probably involve nonreductive metathesis reactions like those known for zirconium alkyls. Possible structures for the stereospecific and nonspecific sites are proposed.

K 2− xTi 2(PO 4) 3 with 0 ≤ x ≤ 0.5: A mixed-valence nonstoichiometric titanophosphate with the langbeinite structure

A new nonstoichiometric titanophosphate, K 2− x Ti 2(PO 4) 3, has been isolated for 0 ≤ x ≤ 0.5. This compound which belongs to the Langbeinite structure is characterized by a mixed valence of titanium Ti III Ti IV . The structures of two compositions x = 0 and x = 0.25 have been determined from a single-crystal X-ray diffraction study. This cubic phase ( a = 9.8559 Å for x = 0.25, a = 9.8688 Å for x = 0; space group P2 13) is compared to Nasicon Na x Ti 2(PO 4) 3. The evolution of the TiO distances and calculations of the mean oxidation state of titanium allow a distribution of the Ti III and Ti IV ions on the two types of site to be proposed. The possibility of extending this structure to other univalent cations has been demonstrated with the synthesis of the isotypic compounds Rb 2Ti 2(PO 4) 3 and Tl 2Ti 2(PO 4) 3.

Reactive evaporation of titanium oxide films with controlled Ti/O ratio

Oxidation state selected titanium oxide thin films (TinO2n−1; n=1–∞) were deposited by a combination of a pulsed molecular beam source and an electron beam metal source. The oxidation state of titanium was controlled solely by the number of gas pulses and the temperature of a substrate. The conditions for depositing crystalline TinO2n−1 thin films were determined.

Local structure investigation of the ion sputtered oxide substrates

Effect of substrate pretreatment by ion sputtering on adhesion has been studied for the case of thin Ti films deposited on two different oxide substrates, namely, fused silica and sapphire. Peel test measurements showed that the peel strength of Ti on the oxide substrates was enhanced as the ion sputter time was increased at a constant ion flux. In situ x-ray photoelectron spectroscopy was used to investigate the chemical interaction of Ti with the sputtered substrate. Intermediate oxidation state of titanium, i.e., a TiOx-like (1<x<1.5) state, was formed at the interaction sites on both treated and untreated substrate surfaces. Comparison of the x-ray induced O(KVV) Auger spectra evolved at different Ti coverages on these substrates suggested that ion sputtering created additional interaction sites on the substrate surface. Surface extended electron energy-loss fine structure above the oxygen K edge was used to investigate the local structure of the ion sputtered substrates. The bond length determined by this technique for the sputtered surface is consistent with the scenario that ion sputtering creates defects in the top monolayers of the substrate, which provide the increased interaction sites.

Divalent titanium chemistry. Synthesis, reactivity, and x-ray and neutron diffraction studies of Ti(BH4)2(dmpe)2 and Ti(CH3)2(dmpe)2

Low valent organotitanium complexes have been implicated as Ziegler-Natta olefin polymerization catalysts and as stoichiometric reagents in organic synthesis. However, very few low-valent alkyls of titanium have been reported, and, in particular, the divalent oxidation state of titanium is virtually unexplored. The authors now report the synthesis and characterization of the unusual divalent tetrahydroborate complex Ti(BH/sub 4/)/sub 2/(dmpe)/sub 2/, 1, and its conversion to the methyl compound Ti(CH/sub 3/)/sub 2/(dmpe)/sub 2/, 2. Complex 2 is unique among octahedral complexes of the 3d metals in being low-spin within the t/sub 2g/ manifold and exhibits very unusual NMR features for the titanium methyl group.

Electron spin resonance, titanium oxidation state, and ethylene polymerization studies of a model supported Ziegler-Natta catalyst. Spectroscopic detection of titanium tetrachloride

Amorceur prepare par depot de butylate d'alkylmagnesium et de TiCl 4 sur un support de silice

Interaction of Ti with fused silica and sapphire during metallization

X-ray photoelectron spectroscopy has been used to investigate the chemical interaction of Ti with fused silica and sapphire by sequential evaporation of Ti onto these substrates. In both cases, the intermediate oxidation state of titanium, i.e., a TiOx-like (1≤x≤1.5) state, is formed at the interface at low Ti coverages (<1 monolayer). Chemical bonds appear to have developed between the Ti 3d electron and the 2p electron of oxygen at the interaction sites on the substrate surface. Comparison of the x-ray induced O(KVV) Auger spectra evolved at different Ti coverages on silica and sapphire suggests that both surfaces have the same chemical reactivity with titanium.

X-ray photoelectron spectroscopic investigations of the activation of FeTi for hydrogen uptake

Abstract Activation of FeTi alloy could either give rise to surface segregation and subsequent oxidation of titanium and the formation of iron clusters or the formation of metastable TiFeO, suboxide. The validity of either of the postulates could be gauged by monitoring the nature and concentration of each of the oxidation states of iron and titanium by depth profile analysis by XPS. These studies showed that fresh samples contained multiple oxidation states of iron and titanium though the concentrations of lower valent oxides are usually small. Sputtering studies showed that this oxide layer is of considerable depth and during activation, iron oxides are easily reduced to the metallic state as compared to the oxides of titanium. The chemical reaction induced, segregation may be the contributing factor for the enhanced concentration of titanium on the surface of these alloys.

ChemInform Abstract: Oxidation State of Titanium in the Complex Ti(bpy)3.

Chemischer InformationsdienstVolume 17, Issue 21 Organoelement Compounds ChemInform Abstract: Oxidation State of Titanium in the Complex Ti(bpy)3. A. FLAMINI, Search for more papers by this authorA. M. GIULIANI, Search for more papers by this author A. FLAMINI, Search for more papers by this authorA. M. GIULIANI, Search for more papers by this author First published: May 27, 1986 https://doi.org/10.1002/chin.198621248Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue21May 27, 1986 RelatedInformation

On the oxidation state of titanium in the complex Ti(bpy) 3

On the oxidation state of titanium in the complex Ti(bpy) 3

Coloring of iron surface controlled by Ti +[sbnd]O + double-ion implantations

Ti +O + double-ion implantations in pure iron have been performed with 1 × 10 17 Ti +/cm 2 at 150 keV and with 1 × 10 17 and 2×10 17 O +/cm 2 at 50 or 35 keV at room temperature. Oxidation state of pre-implanted titanium was investigated by means of X-ray photoelectron spectroscopy. Colored surfaces were produced by the double-ion implantations combined with an electrochemical oxidation of the specimens. Colors such as deep blue, purple, and brown appeared after the electrochemical oxidation with cyclic voltammetry in a 0.5 mol/dm 3 acetate buffer solution of pH 5. The mechanism of the coloring is discussed from analysis of the oxidation state of pre-implanted titanium and concentration-depth profiles of the titanium before and after the anodic oxidation of specimen electrodes. These results showed that double-ion implantations are a useful technique to achieve the coloring with corrosion inhibition of iron surfaces.

Stoichiometry and thickness of the initial oxide formed on clean titanium surfaces determined by quantitative Auger electron spectroscopy, electron energy loss spectroscopy, and microgravimetry

The initial oxidation of a clean polycrystalline titanium film was studied by Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS), while simultaneously monitoring the total oxygen uptake using the quartz crystal microbalance (QCM). Quantitation of the O KLL and Ti LMM AES intensities reveals that the surface stoichiometry at the initial stages of oxidation (<100 L O2 at 1×10−5 Torr) corresponds to that expected for Ti2O3, and the ELS results also suggest the presence of the lower oxidation states of titanium (+2,+3) on the surface. The microgravimetric results indicate that the oxidation is not confined to the region sampled by the electron spectroscopic methods, and a surface layer of Ti2O3 whose thickness is ∼40 Å is consistent with the observed combination of results.