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At high temperature, coarse-grained (bulk) rutile is well established as the stable phase of Ti[O.sub.2], and nanophase anatase, thermodynamically stable relative to nanophase rutile, transforms irreversibly to rutile as it coarsens. The lack of experimental heat-capacity data for bulk anatase below 52 K lends uncertainty to its standard entropy and leaves open a slight possibility that anatase may have a thermodynamic stability field at low temperature, as suggested by some theoretical calculations. In the present study, the molar heat capacities of rutile and anatase were measured from 0.5 K to about 380 K. These data were combined with previously measured high-temperature heat capacities, and fits of the resulting data set were used to generate [C.sup.o.sub.P,m],[[DELTA].sup.T.sub.0][S.sup.o.sub.m], [[DELTA].sup.T.sub.0][H.sup.o.sub.m], and [[DELTA].sup.T.sub.0][G.sup.o.sub.m] values at smoothed temperatures between 0.5 and 1300 K for anatase and 0.5 and 1800 K for futile. Using these new data and the enthalpy of transformation between anatase and rutile at 298 K, the change in Gibbs free energy for the transition between anatase and futile from 0 to 1300 K was calculated. These calculations reveal that the transformation from bulk anatase to bulk rutile is thermodynamically favorable at all temperatures between 0 and 1300 K, confirming that bulk anatase does not have a thermodynamic stability field. Implications for the natural occurrence of these two minerals in terrestrial, lunar, and planetary settings are discussed. In particular, anatase requires low-temperature aqueous conditions for its formation and may be a reliable indicator of such conditions in both terrestrial and extraterrestrial settings. Keywords: Rutile, anatase, Ti[O.sub.2], heat capacity, thermodynamics, phase transformation

The two-step thermal decomposition method from barium titanyl oxalate nanoparticles were used to prepare barium titanate (BaTi[O.sub.3]) nanoparticles from 27 to 192 nm. The newly obtained dense BaTi[O.sub.3] nanoparticle sphere arrays were used to measure a size dependence of temperature versus crystal structure and size dependence of temperature versus dielectric constant.

Albite patches in coarsely mesoperthitic alkali feldspars from the Klokken syenite have oscillatory zoning seen at blue wavelengths using cathodoluminescence. Using a five-spectrometer, high-resolution elemental mapping technique in an electron probe, we show a close correspondence between CL emission intensity and Ti, present at levels up to ~200 ppm. Albite patches were analyzed for major and 16 trace elements by laser-ablation inductively coupled-plasma mass spectrometry. SEM elemental maps acquired simultaneously with the CL showed that a similar zoning pattern is exhibited by Ca, but there is no correlation between CL intensity and Ca concentration. None of the trace elements analyzed correlate with Ti. We conclude that tetrahedral [Ti.sup.4+] is the most likely activator of blue luminescence in these albitic alkali feldspars possibly because of a defect associated with Al-O-Ti bridges. Keywords: Cathodoluminescence, alkali feldspar, perthite

Scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) was applied to investigate the grain boundaries on ASTM grade-7 titanium (Ti-7) with a freshly polished surface, and the results showed that the alloying element, Pd, and the impurity, Fe, cosegregated to grain boundaries. Scanning electrochemical microscopy (SECM) was used to study the variations in reactivity on Ti-7 exposed to an aerated neutral solution of 0.1 M NaCl. Locations that possessed an enhanced reactivity compared to the oxide-covered (Ti[O.sub.2]) surface of the grains on SECM images were proposed to be the boundaries. These areas were further activated by the application of a cathodic bias, and interconnection of the active locations allowed the construction of 'grain boundary maps'. Variations in surface reactivity were quantitatively analyzed by fitting probe approach curves (PACs) to curves simulated with a model based on finite element analyses using the platform of COMSOL multiphysics software. The difference in reactivity between active grain boundaries and oxide-covered grains was up to a factor of 100 on freshly polished surfaces. This difference decreased to a factor of 10-15 after longer-term exposure of the Ti-7 to the aerated solution, indicating partial passivation of the Pd/Fe-stabilized [beta]-phase in the grain boundaries. PAC analyses of oxide-covered grains showed that the reactivity increased logarithmically as the bias potential to the Ti-7 was decreased, consistent with reduction of the insulating Ti[O.sub.2] layer to a more conductive TiOOH layer.

An investigation on the alkenylsilanes of varying chain lengths is presented. Results reveal that alkenylsilanes are versatile single-site comonomers having both the kinetic competence to efficiently effect silanolytic chain transfer in a variety of environments.

A neutral octatitanium citrato oxo-complex assembles as an insoluble crystalline material from aqueous solutions of titanium citrates. The octanuclear core features a unique geometry, where planar Ti4 layers are linked by linear Ti-O bridges.

Bis(pyrrolide-imine) titanium complexes in conjunction with methylalumoxane (MAO) were found to work as efficient catalysts for the copolymerization of ethylene and norbornene to afford unique copolymers via an addition-type polymerization mechanism. The transmission electron microscopy (TEM) indicated that the PE-b-poly(ethylene-co-norbornene) possesses high potential as a new material consisting of crystalline and amorphous segments, which are chemically linked.

A study is conducted to investigate the structural aspects of the products isolated from the reactions of series of titanium alkoxides with rubidium alkoxides. The resultant double alkoxides are determined by single crystal X-ray diffraction to be [Rb (Mu- ONep)(sub 4)(py) Ti (ONep)](sub 2) (6), [Rb (Mu-DMP) Ti (DMP) (sub 4)] infinity, and [Rb (Mu-DMP)(sub 2)(Mu-ONep)(sub 2) Ti (OMNep)] infinity.

The Raman and infrared (IR) study of various layered zirconium and titanium acid phosphates of alpha- and gamma-type, alpha-M[O3POH](sub 2).H2O and gamma-M[PO4][O2P(OH)(sub 2)].2H2O, is described. A simple theoretical model, based on the interaction between the [PO4] unit and four Li(super +) in similar geometrical arrangement found in the structures of the layered phosphates, explains about the high-energy shift observed in the layered phosphates.

The potential-time curves for the anodic oxidation of titanium are analyzed. An ion-hopping conduction model is used for this purpose.

The results of theoretical calculations obtained at the B3LYP/6-31G* level on the structural, electronic, and energetic properties of Ti-sillicalites are discussed. An open surface structure with one OH group and a closed-bulk structure with no bonded OH group at the Ti site are responsible for the observed UV-vis properties of Ti-sillicalite materials.

The study of the active species present on the TS-1-H2O2/H2O catalytic system and elucidation of the mechanisms of formation and interconversion of these species is discussed. It is demonstrated that gentle drying of the TS-1-H2O2/H2O system leads to the transformation of the yellow peroxo groups into noncolored species, still located at Ti centers.

The formation and properties of silica and titania nanorods encapsulated with a thin gold shell is presented. The results suggest that the formation of general class of oxide-metal core-shell systems should be possible, giving 4 degrees of freedom in tuning the optical properties; core material, core diameter, shell material, and shell thickness.

Calculations have been carried out to investigate the insertion of the ethylene monomer into the Ti--alkyl bond for the systems CpNC[(t-Bu).sub.2]RTi-[mu]-Me-B[([C.sub.6][F.sub.5]).sub.3] (R = Me and Pr), using density functional theory. A validated QM/MM model was used to represent the counterion. The tertiary butyl groups in the ligands were modeled with QM/MM, with hydrogens being used as the capping atoms. Solvent effects were incorporated with single point solvent calculations done with cyclohexane ([epsilon]= 2.023) as the solvent. With R = Me (the initiation step), approach of the ethylene cis and trans to the [mu]-Me bridge was considered. Insertion was found to be endothermic, with [DELTA][[H].sub.tot] being 12.7 kcal/mol (cis) and 15.5 kcal/mol (trans). The propagation step was then studied for the contact ion pair CpNC(t-Bu).sub.2]PrTi-[mu]-Me-B[([C.sub.6] [F.sub.5]).sub.3] (4). Different conformations of the propyl chain in 4 were considered by altering [theta], the dihedral angle formed between the [C.sub.[beta]]-[C.sub.[alpha]]-Ti and the Ca-Ti-[mu]C planes. The resting states were found to be at [theta] = -69[degrees] (4a), 177[degrees] (4b), and 53[degrees] (4c). A maxima was found near [theta] = 0[degrees] (4(1). The cis and trans approaches of the ethylene monomer were considered for each of the four cases. The cis approach towards 4a and trans approach towards 4d led to insertion, with displacement of the counterion from the metal centre. The insertion barriers were found to be 17.8 kcal/mol, for the cis approach towards 4b and 16.4 kcal/mol for the trans approach towards 4d. The cis approaches towards conformers 4a and 4c showed common characteristics, with uptake barriers being higher than the subsequent insertion barriers in the two cases. Uptake barriers were 13.6 kcal/mol {TS(4a-Ta)} and 10.7 kcal/mol {TS(4c-8a)}. The corresponding insertion barriers were 11.8 kcal/mol {TS(Ta-13a)} and 8.4 kcal/mol {TS(8a-13a)}. The trans approaches towards conformers 4a and 4c led to insertion barriers of about 15.1 kcal/mol (lower than for the 4b and 4d cases). The cis approach towards 4d and trans approach towards 4b were found to lead to hydrogen transfer from the propyl chain to monomer, terminating the chain. Termination barriers were high--greater than 19.0 kcal/mol. This suggested that ethylene insertion would be favoured over termination during the propagation step. Key words: homogeneous catalysis, counterion, initiation, propagation, termination.

The rates of dehydrogenation of the sodium alanates NaAIH4 and Na3AIH6 doped with 2 mol percent titanium (Ti) or zirconium (Zr) are measured over the temperature range 363-423 K. NaAIH4 and Na3AIH6 undergo dehydrogenation at equal rates upon direct doping with titanium.

The microstructures of the nanorod arrays are investigated using field-emission scanning electron microscopy and transmission electron microscopy. The chemical states of the titanium and ruthenium elements in the nanorods are analyzed and structural characteristics are studied.

Molecular junctions were fabricated consisting of 3.7 nm thick layer of nitroazobenzene (NAB) molecules between a pyrolyzed photoresist substrate (PPF) and a titanium top contact that was protected from oxidation by a layer of gold. The current/voltage behavior of the PPF/NAB(3.7)/Ti junctions showed strong and reproducible rectification, with the current at +2 V exceeding that at -2 V by a factor of 600.

Ab initio DFT molecular dynamics simulations are combined with quantum dynamics calculations of electronic relaxation to investigate the interfacial electron transfer in catechol/TiO2-anatase nanostructures under vacuum conditions. The results are relevant to the understanding of surface charge separation in efficient mechanisms of molecule-based photovoltaic devices.

A present study revealed that photocatalytic activity is highly dependent on the electronic band structure as well as on the bulk structure of photocatalyst material. The shift of the Ln 4f level in Ln (sub 2) Ti (sub 2) O (sub 7) made it possible for the band-gap energy of both Pr (sub 2) Ti (sub 2) O (sub 7) and Nd (sub 2) Ti (sub 2) O (sub 7) to decrease.

The detailed catalytic behavior of Ti complexes with fluorine-containing phenoxy-imine celate ligands for the polymerization of propylene is reported. The steric bulk of the substituent ortho to the phenoxy oxygen plays a decisive role in achieving high syndioselectivity for the chain-end controlled polymerization.

The study shows that molecular oxygen reacts with bridging OH (OH(sub br)) groups formed as a result of water dissociation on the surface of rutile TiO2(110). The results suggest the negative influence of high water concentrations in gas-phase.

The effects of nanosized platinum deposits, dioxygen and electron donors on the kinetics and mechanism of trichloroacetate degradation in UV-illuminated TiO2 suspensions are discussed. It is suggested that the platinum surface stabilized the reactive intermediates and subsequently changed the mechanistic pathway of TCA degradation.

A study is conducted to examine the photoinduced charge separation between a photosensitizer, 5, 10, 15, 20-tetrakis-21H, 23Hporphyrin cation and an electron acceptor, methyl viologen, intercalated in the different layer sheets of titanoniobate. The stacked lamella structure of the thin films consisting of TiNbO5 hybrids with TMPyP(super 4+) and MV(super 2+) is examined.

The photocatalytic reactions and photoelectrochemical properties of the oxysulfide, Sm2Ti2S2O5, are described. The reactions confirm the fact that the oxysulfide, which is Ti(super 4+)- based, is a stable visible light-driven photocatalyst for the oxidation of water to O2 or the reduction of H(super +) to H2 without the oxidation of S(super 2-) or the decomposition of the structure.

Results of temporal changes in the potential of TiO2 films (supported on Au substrates) are presented that were monitored under ultraviolet irradiation in aqueous media. A simple model, based on initial photocharging of the TiO2 film/solution interface and subsequent carrier trapping/detrapping events, is presented to account for the observed trends in the measured [E(sub ph)-t] profiles.

A series of potassium-promoted molybdenum catalysts (alkali/Mo molar ratio < 1) are characterized by probing the surface molybdenum species and the physical-chemical properties of the Si/Ti support to examine the effect of the alkali level on the surface characteristics of the support. The results revealed that with the addition of low levels of potassium distorted MoOx units, experiencing decreased Lewis acidity, could be more reactive towards electronegative Si-O(super -) support ligands on the Si/Ti 1:1 support.

Use of Ti cap layer in removing the interfacial oxides on the Si surface is demonstrated. If the Ti cap were too thin, it would be ineffective in lowering the silicidation temperature.

It is found that incorporation of SnO2 and Sb2O5 into IrOx not only saved the precious content significantly but also generated a synergic effect to make Ti/IrOx-Sb2O5-SnO2 much more stable. Ternary IrOx-Sb2O5-SnO2 is a promising electocatalyst for O2 evolution.

Treatment of the hydrosulfido-bridged titanium-ruthenium heterobimetallic complex with an excess of triethylamine followed by addition of [RuCl(sub 2)(PPh)(sub 3)(sub 3)] and [{(cod0M}(sub 2)-(mu2-Cl)(sub 2) led to the formation of the TiRu(sub 2) and TiRuM mixed-metal sulfido clusters.

Detection, quantification and magnetic field dependence of solid-state (super 17)O NMR of X-O-Y, where X,Y represent (Silicon (Si) and titanium (Ti) linkages, changes in the local structure with functionalization of the silicon alkoxide and the modification of the titanium precursor by acetylacetone is investigated. The Si-O-Ti formation is promoted by the modification of the titanium precursor by acetylacetone.

The photocatalytic oxidation of formate in ~ 10nm TiO2 nanoparticle suspensions under periodic illumination behaves kinetically as a homogenous photochemical system. Absence of competing intermediates and at the slow rates typical of most photocatalytic studies, quantum yields under periodic illumination do not exceed those attained by continuous operation at equivalent average photon absorption rates.

Studies done on the adsorption of dimethyl methylphosphonate (DMMP) and its decomposition on a powdered TiO2 surface by using transmission infrared spectroscopy for different temperature domains are reported. Results reveal that transmission infrared spectroscopy is a powerful method, able to separate surface diffusion, adsorption and dissociation processes for this molecule on TiO2.

The first direct evidence of non random siting of Ti and Fe in TS-1 and FeS-1, nanoporous metallosilicate selective oxidation catalysts of MFI topology are presented. Findings of nonrandom siting of Fe and Ti in MFI demonstrate that there may be a relationship between the location of heteroatoms in the framework and the kinetically favorable pathways driven by the organic SDA.

The unique cage structures of P4O12(super 4-) are detailed. The reaction of P4O12(super 4-) with [Cp*TiCl3](Cp*=n5-C5Me5) gives [(Cp*Ti)2(P4O12)2](super 2-) where the P4O12 ligands adopt a saddle conformation, while that with [(Cp*TiCl)3(u-O3] leads to [(Cp*Ti)3(u-O)3(P4P12)](super -) containing a crown from P4O12 ligand, both products feature their unique cage structures.

The neutron diffraction analysis on Zr and Ti substituted 2:14:1 compounds is discussed. The lattice expands in the Ti-containing melt spun alloy of (NdPr)FeB and Ti is present on the j1, j2 sites that are normally occupied by Fe.

Solvent-free synthesis of a series of alkylthio-substituted titanyl phthalocyanine (TiOPc) derivatives starting from the corresponding phthalonitriles (Pn) is reported. The process eliminated the formation of the unmetalated phthalocyanine ([H.sub.2]Pc), a side product that makes purification difficult and the alkylthio groups in the obtained derivatives enhance solubility in common organic solvents and shift the absorption to the near-IR region.

Multiwalled carbon nanotubes decorated with Ti[O.sub.2] nanoparticles is examined. The attached Ti[O.sub.2] nanoparticles have affected the thermal properties of the resulting hybrid nanostructure, as disclosed by differentiated reactions to laser heating.

The seven step total synthesis of the bridge-fused Aspidosperma indole alkaloid ([plusmn])-subincanadine F is presented. The synthetic application of a titanium-mediated intramolecular nucleophilic acyl substitution (INAS) reaction for the construction of the bridge-fused ring system is demonstrated.

The remarkable migratory insertion reactions of 2,2-disubstituted-1-alkenes, intramolecular 1,5-[sigma] bond metathesis via [epsi]-agostic interactions, and a rare example of a [beta]-agostic alkyltitanocene are discussed. The observed titanocene-based chemistry contrasted starkly to that of the analogous zirconium system, in which the unusual but well-characterized cationic methyl alkene complex [[Cp.sub.2]ZrMe(DMP)](+) does not undergo migratory insertion and subsequent reactions.

The combination of an aldehyde, an allylic bromide, and tert-butanesulfinamide in the presence of indium and titanium tetraethoxide has provided access to homoallylamine derivative. The synthetic utility of the enantioenriched homoallylamine derived from n-decanal is shown in a concise synthesis of (+)-isosolenopsin and similar homoallylamines are used by other groups in the preparation of naturally occurring alkaloids.

A study was conducted to demonstrate the efficiency of titanocene(III) aqua complexes as a unique class of hydrogen-atom donor (HAT) reagents based on two key features such as excellent binding capabilities of water toward titanocene(III) complexes and a low activation energy for the HAT step. The results provide insight into the remarkable hydrogen-atom donor characteristics of water in [Ti.sup.III]-mediated free-radical chemistry.