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Abstract Copolymers of propylene/1-octene and propylene/1-hexene were synthesized in slurry phase polymerization using Mg[Cl.sub.2]/Ti[Cl.sub.4]/Diester based catalyst system. The Al/Do (co-catalyst/external donor), Al/Ti (co-catalyst/catalyst) mole ratio variations were investigated for effect [...]

NASA's Artemis program aims to return to the moon in search of scientific discoveries and establish a habitat using in-situ resource utilization. However, the past lunar explorations presented challenges, such [...]

Composite coatings containing manganese sulphide as lubricating addition and enhanced with hard carbide particles (TIC, WC) were synthesized on a plain steel substrate using the plasma transferred arc technique. The coatings are well bonded to the substrate, have a thickness of about 1 mm, and are free of any visual defects. They consist mainly of a martensitic or ferritic matrix enhanced with titanium or tungsten carbides and a dispersion of MnS particles. The tribological properties of the composites are assessed using a pin-on-disk device. Both composites possess self lubricating properties, due to the formation of a thin layer of manganese sulphide on their wear tracks. The corresponding .friction coefficients vary between 0.25 and 0.28, compared with 0.50-0.60 obtained from similar hard coatings without MnS addition. The wear rates are of the order of [10.sup.-5] [mm.sup.3]/m N and are two orders of magnitude lower than those obtained from the substrate material with MnS addition, but without the presence of hard enhancing particles. The wear regime is mild abrasion due to the combined action of both lubricating (MnS) and hard (TiC or WC) particles. [DOI: 10.1115/1.4001649] Keywords: plasma transferred arc (PTA), manganese sulphide (MnS), titanium carbide (TIC), tungsten carbide (WC), self lubricating coating

Synthesis and characterization of composite polymer electrolytes based on lithium bis(oxalato)borate (LiBOB) and a host matrix of nanoparticulate anatase dispersed in phase-separated poly(vinylidenefluoride) (PVdF)-poly(vinylchloride) (PVC) are described. Ethylene carbonate (EC) and diethyl carbonate (DEC) were used as plasticizers in the membranes, and nanoparticulate [TiO.sub.2] (anatase) was used as the filler. The membranes were characterized by SEM, XRD, and a.c. impedance measurements. A membrane with 2.5 wt% filler exhibited a conductivity of 5.43 x [10.sup.-4] [S.cm.sup.-1] at ambient temperature. Filler levels above 2.5 wt% increased the crystallinity of the membranes, rendering them less conducting. Activation energy and coherent length of the composite polymer electrolytes have also been calculated. POLYM. ENG. SCI., 49:2109-2115, 2009. [C] 2009 Society of Plastics Engineers, INTRODUCTION As lithium-ion batteries continue to conquer a niche market especially those related to portable gadgets such as notebook computers, camcorders, and telecommunication equipment, there is intense parallel R&D effort [...]

Ti[O.sub.2] microparticles (TMs) and nanoparticles (TNs), prepared by hydrolysis of Ti butoxide and maintained in aqueous solution, were evaluated as matrixes for the detection of small molecules. With aqueous suspensions of TMs, positive-ion spectra collected for phospholipids (PLs) extracted from soybeans showed high sensitivity and no matrix interferences. Negative-ion traces had a suitable signal-to-noise ratio (S/N) but showed high levels of phosphatidic acid caused by the loss of the headgroup in other PLs. The hydrolysis was more pronounced when TNs were used. In aim studies performed by applying TM suspensions directly onto 50-[micro]m thick soybean slices did not yield satisfactory results as TMs formed a crusty layer that precluded desorption/ionization. When a TN suspension was used instead, PLs and triacylglycerols were detected. Only minor PL hydrolysis was observed. TNs also enabled the coverage of rose petals and the detection of different levels of flavonols/anthocyanins and their glycosides as the color changed from yellow to orangered. Although the hydrolysis of PLs limits the use of TMs or TNs for in vitro PL analysis, TNs offer a suitable alternative for the analysis of other molecules of low molecular weight, and their small size (average of ~200 nm) facilitates their penetration into tissue for in situ imaging.

The feasible integration of [Ba.sub.x][Sr.sub.1-x]Ti[O.sub.3] (BST) films into Si wafer as microwave interdigital capacitor (IDC) tunable devices with a Ti[O.sub.2] thin film buffer layer is examined. Findings reveal the observation of enhanced tunability values of 40 percent at the bias 5Kv/cm in BST/Ti[O.sub.2]/HR-Si IDC.

The pore structure formation in bentonite, pillared with a mixed sol of silicon and titanium hydroxides and treated subsequently with quaternary ammonium surfactants is investigated. It was found that titanium in these samples is highly dispersed in the silica matrix rather than existing in the form of small particles of pure titania.

The electron injection from the transition metal complex Ru(dcbpy)2(NCS)2 (dcbpy = 4,4'-dicarboxy-2,2'-bipyridine ) into a titanium dioxide nanocrystalline film occurs on the femto- and picosecond time scales. The dominating part of the electron transfer proceeds extremely rapidly from the initially populated, vibronically nonthermalized, single excited state, prior to electronic and nuclear relaxation of the molecule.

It has been demonstrated that through amorphization obstacles to laser thermal processing for the fabrication of salicide on CMOS devices can be overcome. It has also been demonstrated that laser thermal processing inherently provides the ability to fabricate thicker salicides over the gate regions which help significantly in overcoming the phase transformation.

A reinvestigation of the ketone hydrosilylation reaction using (R,R)-ethylenebis(tetrahydroindenyl) titanium difluoride as a precatalyst was conducted. Improved turnover numbers and high enantioselectivities were realized by using a protocol that involves the slow addition of a primary alcohol to the titanocene-catalyzed asymmetric hydrosilylation reaction of ketones. The utilization of the new activation protocol obviates the need to use alkyllithium reagents for catalyst activation.

Radical cyclization reactions of substituted alpha-(prop-2-ynyloxy) epoxides with bis(cyclopentadienyl)titanium(III) chloride as the radical source produced polysubstituted tetrahydrofurans. Titanium(III) species were produced in situ from commercially available titanocene dichloride and zinc dust in tetrahydrofuran. The radical cyclization reactions were stereo- and regioselective in nature.

Titanium Lewis acid Ti-TADDOLates are used as chiral in the enantioselective isopropyl hemiester formation from cyclic meso-anhydrides through a ring opening reaction. Highly enantioselective isopropyl hemiesters can be generated from a range of structurally diverse anhydrides. The reaction proceeds either by desymmetrization through enantiotopic carbonyl compound differentiation or racemic compound kinetic resolution.

We describe the design of a continuously tunable Ti:sapphire regenerative amplifier that is capable of sustaining amplification over a wavelength range from 730 nm to more than 800 nm. The amplifier cavity is tuned with a prism pair in combination with a spherical mirror. It sustains an oscillation bandwidth of 5 nm and produces a chirped output pulse energy of 1.2 mJ compressible to a duration of 140 fs at 745 nm. We present a calculation of the theoretical bandwidth.

The lateral deformation of a substrate during a stick/slip event was quantitatively investigated using atomic force microscopy. A description of an arbitrary cantilever-tip-surface configuration to analyze strain-dependent stiffness was made. The close correspondence between the predicted and the measured values for the local lateral stiffness of TiS2 and NaCl surface areas indicated that the deformation encountered was due to strong stick/slip friction on the layered substrates.

The gas-phase kinetics of the spontaneous reaction between tetrakis(dimethylamido)titanium, Ti(NMe2)4, and ammonia to produce HNMe2 shows that kinetically controlled conditions are favorable for chemical vapor deposition of titanium nitride, TiN. The reaction is reversible when an excess of HNMe2 is added to the gas flow. The rate constant, k = (1.2 plus or minus 0.2) into 10(super minus 16) cm cube per molecule per second depends upon the transamination reaction, which is the rate determining step.

A new process that uses bis(trimethylphosphine)titanocene as a catalyst in the reductive cyclization of enones to cyclopentanols is introduced. The catalyst, which is sensitive to both air and moisture, is regenerated by the cleavage of the titanium-oxygen bond in a metallacyclic intermediate by a silane. Besides regenerating the catalyst, the reaction affords a titanocene alkyl hydride that, in turn, reduces to a silyl-protected cyclopentanol. Subsequent hydrolysis affords the end product.

A study used a titanium complex generated in situ from a titanium alkoxide and a chiral binaphthol, to efficiently catalyze the asymmetric oxidation of sulfides to chiral sulfoxides in moderate yield, with tert-butyl hydroperoxide. The production of an efficient catalyst for the extremely enantioselective oxidation, and the sustenance of the catalytic activity of the titanium-binaphthol complex for an extended period needed water. The oxidation needed the presence of over 1.0 mol equivalent of water relative to sulfide. The kinetic resolution of the sulfoxide takes place after the initial asymmetric oxidation to the chiral sulfoxide.

A new gram-scale synthetic route to octafluoro(2.2)paracyclophane involves the use of a low-valent titanium (Ti*) complex to reductively debrominate dibromotetrafluoroxylene. The Ti* complex is obtained by treating titanium tetrachloride with an equimolar amount of lithium aluminum hydride in tetrahydrofuran. Under high dilution, the tetrafluoroxylylene intermediate dimerizes into the paracyclophane. Raising the concentration increases the yield of the trimer byproduct and reduces that of the paracyclophane.

O-protected aryl thioglycolates undergo highly diastereoselective titanium- catalyzed aldol condensation to form alpha, beta-dihydroxy esters in excellent yields. Benzyloxy thioesters yield anti-diols (with up to 98% purity), irrespective of the aldehyde used, via intramolecular Ti-chelation between the carbonyl and the benzyloxy oxygens. Bulky sily- and sulfur-protected thioesters, on the other hand, yield anti-diols (up to 90% purity), this time due to steric hindrance against Ti-coordination that drives the enolate towards the Z configuration.

The synthesis of dibenzyldiamino-2-propanol and three isomers of dibenzyldiaminobutane-2,3-diol provides the materials for the preparation of A-77003, a potential aspartic protease inhibitor. The alcohol is obtained by sequential epoxidation/ring-opening of a phenylalanine-derived trans olefin, followed by azide reduction. The diols are more efficiently prepared by a metal-catalyzed intermolecular pinacol coupling of protected phenylalaninal. The (3R,4R,5R,6S) and (3S,4R,5S,6S) diol isomers may be interconverted via two intramolecular hydroxyl inversion routes.

The use of chiral imines and enolate precursors allows allows the mild, one- pot synthesis of optically active beta-lactams. The enolates derived from ethyl 3-hydroxybutyrate and the imines obtained from optically pure p-methoxyphenyl aldehydes exhibit highly efficient diastereoselectivity in their condensation reaction, as borne out by spectroscopic monitoring. To demonstrate the utility of the method, advanced precursors of (+)-PS-5, (+)-PS-6, thienamycin and 1-beta-methylthienamycin are prepared.

Chiral titanium complexes can mediate the addition of carbon nucleophiles to carbonyls via two mechanisms. For d(sup 1)-nucleophiles, the favored path involves a six-center transition, with a third mediator molecule from the d(sup 1)-reagent (usually a methyltitanium) serving as catalyst. The second path passes throough a bimolecular six-center cyclic transition for d(sup 3)- nucleophiles, using allyltitaniums or titanium enolates. The reagents are obtained by substituting protic ligands for Ti-boundchlorides or by transesterification of titanium alkoxides with a free alcohol. The various synthetic strategies and uses of the reagents are discussed.

The use of titanium(III) in a carefully pH-controlled reaction environment allows the simultaneous reduction of azetidinone and oxime N-O bonds and the formation of tricarbonyls from alpha-oximido-beto-keto esters. The buffered aqueous solution, with acetone as a cosolvent, is maintained at pH5. Using this methodology, tert-butyl 5-(1-hydroxy-2-oxo-4-azetidinyl)-2-oximido-3-oxopentanoate is converted to Wasserman's semifunctionalized carbocephem in 20% yield.

Dibenzyltitanocene serves as a synthetically useful reagent for the thermal olefination of carbonyl compounds. The reagent is prepared from titanocene dichloride and benzylmagnesium chloride. The reactions are carried out in toluene at 45-55 degrees C, using 3-4 equivalents of the reagent. While some aldehydes and alpha,beta-unsaturated ketones are only mildly reactive, the olefination proceeds efficiently with saturated ketones (75-86% yields), esters (35-84%) and lactones (70%). Substitution on the phenyl ring enhances the reactions and opens new synthetic routes to trisubstituted olefins.

The direct one-step conversion of tetrahydropyranyl ethers to acetates in a mild way is described. This transformation is achieved with 20 mol percent of TiCl4 and 1.2 equivalent of Ac2O and the procedure substitutes the acid-labile protective group with the base-labile protected group.

A novel method for the photooxidation of benzyl phenyl sulfide, 4-methoxy-benzyl phenyl sulfide and phenethyl phenyl sulfide was developed based on the TiO2-catalyzed reactions in the presence of Ag2SO4. The synthetic process was characterized by the formation of sulfoxides from the TiO2-induced photochemical oxidation of sulfides. Furthermore, the oxidation process involved the interaction of the oxygenated centers with the sulfur atom of the adsorbed radical cation.

An analysis of the organometallic oxidation of sulfides to sulfoxides reveals that optically pure sulfoxides in reasonable chemical yields result under mild conditions from the catalysis of the kinetic resolution of racemic sulfoxides, by a chiral titanium-binaphthol complex. This discovery enables the most efficient and easy manner of deriving optically pure sulfoxides.

The 'arc-ion-plating process' used to deposit hard wear resistant coatings onto tools is described in detail, such as: * the essence of the arc deposition technology, * the microdroplets and potential ways of their elimination, * the arc evaporation sources and vacuum coating systems, and * the benefit of hard coatings for cutting tools.

The synthesis of 2-hydroperfluoro acid derivatives is described. The process involves thioacetalizing perfluoropropanol hydrate with ethanethiol in the presence of titanium tetrachloride, followed by phase transfer catalyzed (PTC: tetrabutylammonium bromide) elimination of hydrogen fluoride with aqueous potassium hydroxide. Acidic hydrolysis yields S-alkyl thioesters and alkyl esters which, on transesterification with titanium tetraisopropoxide, produce the corresponding O-esters in 60% isolated yield.

Phenolic Schiff base-anchored titanium(IV) alkoxide-peptide/alpha-amino acid complexes catalyze the asymmetric epoxidation of allylic alcohols with hydroperoxides. The 31-90% epoxy alcohol yields are obtained with up to 72% enantiomeric purity. Both the product and selectivity levels are highly dependent on the catalyst mix and the oxidant. Only the Dbs-R-Val system causes an inversion in facial selectivity. Bulky oxidants increase the selectivity while benzylic hydroxyperoxides enhance the product yield.

A titanocene complex, prepared by combining titanocene dichloride with ethyl Grignard, serves as an effective reagent in the reductive cyclization of enynes. Compared to analogous zirconium reagents, the titanocene complex tolerates esters in the substrate. The metallacycles formed may be converted in good yields into cyclopentenones without isolating air sensitive components. A related transition metal-mediated synthesis of iminocyclopentenes is also discussed.

The total synthesis of (-)-mirabazole C, an antitumor alkaloid, involves the sequential self-coupling of S- and N-protected (R)-2-methylcysteine, its putative biosynthetic precursor. Acylation and treatment of the amino acid with p-tosyl chloride and S-(benzylamino)ethanethiol yields the tetrapeptide. The tetracysteine chain is then cyclized into the tetrathiazoline skeleton with titanium tetrachloride in dichloromethane. Oxidation of the terminal thiazoline ring with nickel peroxidegives (-)-mirabazole C in 10% overall yield.

The first-ever use of titanocene 1,1'-binaphth-2,2'-diolate, a transition metal catalyst, allows the high-yielding asymmetric hydrogenation of ketimines to amines. The active catalyst, titanium(III)hydride, is generated by treating the diester with butyllithium and phenylsilane. The hydrogenation is carrried out at 65 degrees C under a 2000-psig H2 pressure. N-benzyl imines and cyclic imines produce good(58-85%) and excellent (97-98%) optical yields, respectively, with their product yields ranging from 66-93%. The mechanism of conversion is discussed.

An air-stable titanium/silane catalyst system allows the conversion of esters to primary alcohols. The process involves mixing the ester with 2.5-3.0 equivalents of triethoxysilane and 5 mol % of titanium isopropoxide at 40-55 degrees C to yield the corresponding silyl ethers. Subsequent aqueous alkaline hydrolysis forms the primary alcohols in 70-95% yields. Besides its stability, the catalyst system for the hydrosilylation is self-priming, requires no solvent, and may be regenerated. It is highly tolerant of other functional groups.