Showing papers on "Titanium published in 1994"
TL;DR: The use of the templating approach to synthesize mesoporous silica-based molecular sieves partly substituted with titanium—large-pore analogues of titanium silicalite find that these materials show selective catalytic activity towards the oxidation of 2,6-ditert-butyl phenol to the corresponding quinone and the conversion of benzene to phenol.
Abstract: Titanium silicalite is an effective molecular-sieve catalyst for the selective oxidation of alkanes, the hydroxylation of phenol and the epoxidation of alkenes in the presence of H2O2 (refs 1-3). The range of organic compounds that can be oxidized is greatly limited, however, by the relatively small pore size (about 0.6 nm) of the host framework. Large-pore (mesoporous) silica-based molecular sieves have been prepared recently by Kresge et al. and Kuroda et al.; the former used a templating approach in which the formation of an inorganic mesoporous structure is assisted by self-organization of surfactants, and the latter involved topochemical rearrangement of a layered silica precursor. Here we describe the use of the templating approach to synthesize mesoporous silica-based molecular sieves partly substituted with titanium--large-pore analogues of titanium silicalite. We find that these materials show selective catalytic activity towards the oxidation of 2,6-di-tert-butyl phenol to the corresponding quinone and the conversion of benzene to phenol.
1,672 citations
TL;DR: An ultralarge pore titanium silicate with MCM-41 structure has been prepared by direct hydrothermal synthesis; this material gives rise to useful catalysts for the selective oxidation of small and large organic compounds.
Abstract: An ultralarge pore titanium silicate with MCM-41 structure has been prepared by direct hydrothermal synthesis; this material gives rise to useful catalysts for the selective oxidation of small and large organic compounds.
629 citations
TL;DR: The class of titanium alloys generically referred to as the beta alloys is arguably the most versatile in the titanium family as mentioned in this paper, however, except for one very successful application (Ti-13V-11Cr-3Al on the SR-71), they have remained a very small segment of the industry.
Abstract: The class of titanium alloys generically referred to as the beta alloys is arguably the most versatile in the titanium family. Since these alloys offer the highest strength-to-weight ratios and deepest hardenability of all titanium alloys, one might expect them to compete favorably for a variety of aerospace applications. To the contrary, however, except for one very successful application (Ti-13V-11Cr-3Al on the SR-71), the beta alloys have remained a very small segment of the industry. As a perspective on this situation, this article reviews some past and present applications of titanium alloys. It also descibes some unique new alloys and applications that promise to reverse historical trends.
286 citations
TL;DR: In this article, the catalytic activity of the Ti-Beta catalyst for selective oxidation by H 2 O 2 of alkanes and alkenes with different molecular sizes was measured and compared with that of TS-1 under the same experimental conditions.
283 citations
TL;DR: These studies show that a high degree of bone contact and bone formation can be achieved with titanium implants which are modified with respect to oxide thickness and surface topography, and it appears that a reduction of surface roughness may influence the rate of bone formation in rabbit cortical bone.
275 citations
TL;DR: The use of tetraalkylammonium hydrotriorganoborates as reducing agents leads to colloidal transition metals in organic phases as discussed by the authors, which serve as sources for heterogeneous metal catalysts.
262 citations
Patent•
28 Sep 1994TL;DR: A solar cell has a chalcopyrite absorber layer applied on the substrate by means of an adhesive layer made of chromium, titanium, tantalum or titanium nitride.
Abstract: A solar cell has a chalcopyrite absorber layer applied on the substrate by means of an adhesive layer made of chromium, titanium, tantalum or titanium nitride.
259 citations
TL;DR: Radiofrequency magnetron sputtering was used as an alternative method to deposit thin films of hydroxylapatite on titanium substrates and it was demonstrated that the sputtered layer was crystalline with a preferred (001) crystallographic orientation with the C-axis perpendicular to the substrate surface.
Abstract: Plasma-sprayed hydroxylapatite coatings on metals such as titanium have been investigated for many years and have shown a good biocompatibility when implanted in bony tissues. Radiofrequency magnetron sputtering was used as an alternative method to deposit thin films of hydroxylapatite on titanium substrates. X-ray diffraction demonstrated that the sputtered layer was crystalline with a preferred (001) crystallographic orientation with the C-axis perpendicular to the substrate surface. Scanning electron microscopy showed that the deposited films had a uniform and dense structure. The calcium phosphate ratio varied between 1.5 and 2.0, as determined by energy-dispersive X-ray analysis. The in vitro dissolution appeared to be determined by the degree of the coating's crystallinity. © 1994 John Wiley & Sons, Inc.
230 citations
TL;DR: To varying degrees, all titanium surfaces indicated activation of the intrinsic pathway of coagulation as determined by their kallikrein formation in plasma.
208 citations
TL;DR: Results suggest that titanium dioxide particles under UV light irradiation produced photogenerated holes on the surface yielding hydroxyl radicals and hydrogen peroxide inside or outside the cells and the cells were then killed by the action of these highly oxidising molecules.
Abstract: A photoexcited titanium dioxide surface has a strong ability to decompose water into hydrogen and oxygen. We have studied this effect in order to use it to kill cancer cells in vitro and in vivo. A distinct cell killing effect was observed on cultured T-24 human bladder cancer cells treated with titanium dioxide particles and 300-400 nm UV light irradiation. Titanium dioxide plus UV light also dramatically suppressed the tumour growth of T-24 cells that were implanted in nude mice. Cells cultured on the titanium dioxide electrode were also killed under UV irradiation when the electrode was anodically polarised, suggesting that photogenerated holes are involved in the cell killing. The cell killing effect caused by titanium dioxide particles plus UV light irradiation was significantly hampered in the presence of L-cysteine and catalase, scavengers of hydroxyl radicals and hydrogen peroxide respectively. Transmission electron microscopic observations showed the titanium dioxide particles to be distributed on the cell surface and inside the cells. These results suggest that titanium dioxide particles under UV light irradiation produced photogenerated holes on the surface yielding hydroxyl radicals and hydrogen peroxide inside or outside the cells and the cells were then killed by the action of these highly oxidising molecules. The possible application of photoexcited titanium dioxide particles to cancer treatment as a new anti-cancer modality is discussed.
201 citations
TL;DR: An ion beam dynamic mixing (IBDM) method was used to produce thin hydroxyapatite coatings on titanium substrates, indicating the high tensile bond strengths from the as-coated films.
TL;DR: Radio frequency glow discharge-treated Ti had the highest critical surface tension, followed by the passivated and heat-sterilized conditions, and Titanium with no surface treatment had the lowestcritical surface tension.
Abstract: Osteointegration is dependent on a variety of biomechanical and biochemical factors. One factor is the wettability of an implant surface that is directly influenced by its surface energy. This investigation used the Zisman plot to determine critical surface tension as one representative measurement of surface energy. The effects of surface treatment, bulk grain size, and surface roughness on the critical surface tension of unalloyed titanium (Ti) were examined. Radio frequency glow discharge-treated Ti had the highest critical surface tension, followed by the passivated and heat-sterilized conditions. Titanium with no surface treatment had the lowest critical surface tension. The surface energy of Ti with an average grain size of 23 microns was not significantly different from that with a grain size of 70 microns. Surface roughness was shown to cause significant difference in measurements and definitely should be considered in studies of this kind.
TL;DR: Those stems treated thermally were found to have significantly lower metal ion release and improved dissolution behaviour, associated with a change in the surface oxide structure from mixed titanium oxides to a more stable rutile structure.
TL;DR: In this article, the authors investigated the deposition of TiO2 thin films on stainless steel, titanium, barium borosilicate glass and alumina substrates, using titanium tetraisopropoxide as a precursor.
TL;DR: The deposition of titanium in regional lymph nodes was studied after insertion of endosseous, plasma-spray-coated titanium screw implants in a total of 19 beagle dogs, suggesting that the fine particles may be transported by phagocytes to the regional lymph node, where they could be found without any signs of inflammation or foreign-body reaction.
TL;DR: The results indicate that the passive film formed in the PBS solution--with and without addition of H2O2--may be described with a two-layer structure model.
Abstract: Electrochemical measurements, x-ray photoelectron spectroscopy, and scanning tunneling microscopy have been used to study the effect of hydrogen peroxide on the passivity of titanium in a phosphate-buffered saline (PBS) solution. The results indicate that the passive film formed in the PBS solution--with and without addition of H2O2--may be described with a two-layer structure model. The inner layer has a structure close to TiO2 whereas the outer layer consists of hydroxylated compounds. The introduction of H2O2 in the PBS solution broadens the hydroxylate-rich region, probably due to the formation of a Ti(IV)-H2O2 complex. Furthermore, the presence of H2O2 results in enhanced dissolution of titanium and a rougher surface on a microscopic scale. Finally, a dark pigmentation (blue color) is observed when titanium has been exposed--for several weeks--to PBS with additions of H2O2.
TL;DR: In this article, the effects of mass transport, corrosion products and biofilm formation on corrosion kinetics of five copper alloys, four stainless steels and titanium grade 2 exposed to natural and artificial seawater were determined.
TL;DR: In this paper, a special effort is made to analyse the Ti-induced wetting of ceramics in terms of the chemical reactivity and interface microchemistry. And the importance of interactions between the interfacially active element (Ti) and other alloying elements in the metallic melts is elucidated with numerous experimental results.
TL;DR: In this paper, the UHV diffusion energy of bicrystals was determined as a measure of their bond strength, and it was assumed that both these properties are associated with interfacially active elements in the system.
Abstract: In both the practical and theoretical aspects of joining metals to ceramics the influence of impurities on the interfacial bond strength is not fully understood. In the present paper the authors describe part of a study in which the interface of niobium-sapphire bicrystals was contaminated under defined conditions and the interfacial fracture energy of these UHV diffusion bonded bicrystals was determined as a measure of their bond strength. The model combination niobium-sapphire shows at high temperatures a simple reaction in which alumina dissolves in niobium without forming an interlayer. Furthermore, niobium and sapphire are characterized by nearly the same expansion behavior which minimizes the development of thermal stresses during cooling down from the bonding temperature. The authors report on experiments in which silver or titanium atoms have been chosen as interfacial impurity elements. Silver is practically insoluble in niobium and sapphire whereas titanium possesses a highly negative free enthalpy of oxide formation. It is assumed that both these properties are associated with interfacially active elements in the system niobium-sapphire.
TL;DR: In this article, a system for the efficient one-pot generation of phosphonium salts using triethoxysilane, or more conveniently polymethylhydrosiloxane, and catalytic titanium (IV) isopropoxide is presented.
TL;DR: The effect of boundaries on pattern formation was studied for the catalytic oxidation of carbon monoxide on platinum surfaces to create microscopic reacting domains on polycrystalline foils and single-crystal platinum surfaces with inert titanium overlayers.
Abstract: The effect of boundaries on pattern formation was studied for the catalytic oxidation of carbon monoxide on platinum surfaces. Photolithography was used to create microscopic reacting domains on polycrystalline foils and single-crystal platinum (110) surfaces with inert titanium overlayers. Certain domain geometries give rise to patterns that have not been observed on the untreated catalyst and bring to light surface mechanisms that have no analog in homogeneous reaction-diffusion systems.
TL;DR: Application of the mixed-potential theory shows that titanium in coupling with the alloys studied will be under either cathodic or anodic control.
TL;DR: Clinically, ultrasonic cleaning of sandblasted and tribochemically silica coated titanium should improve resin bonding as loose surface particles are removed without relevant changes in composition.
TL;DR: In this article, the influence of local order around the titanium site on Ti 2p X-ray absorption spectra is studied for rutile, anatase, and brookite.
Abstract: The influence of local order around the titanium site on Ti 2p X-ray absorption spectra is studied for rutile, anatase and brookite. This is done by a configuration interaction based calculation of Ti L2,3 X-ray absorption edge shapes, explicitly taking into account the exact first-neighbour surroundings of the cation acting through crystal field splitting and hopping terms. The evolution of the peak splittings and intensities from rutile to anatase is well reproduced for the L2 edge and can be attributed to the small changes in the cation site symmetry. In contrast the splitting of the second peak of the L3 edge cannot be attributed to differences in the first coordination shell of the cation between the titanium oxides.
TL;DR: In this paper, a pre-heat-treated HA powder was pre-treated at 1200 °C for 120 min (the XRD pattern showing no decomposition) and then mechanically mixed with titanium and titanium dioxide powders.
Abstract: Titanium (Ti) implants coated with hydroxyapatite (HA), combining the ability of HA to bond with natural bone and excellent mechanical properties of titanium, have been successfully used in clinics. To improve the crystallinity of the coatings, post-heattreatment was applied on the HA coating-titanium system. Several groups [1-4] have post-heat-treated plasma-sprayed and sputtered HA coatings, to increase their crystallinity and lower their solubility compared with the as-received coatings. Ducheyne et al. [5] employed a vacuum heat treatment on electrophoretically deposited HA coatings to investigate the induced changes on their structures. Besides the benefits produced by heat treatment, there also exist some negative side-effects. Ducheyne et al. [5] found that the heat treated layers contain distinctively different compositions from the as-received coatings. The present authors [3] also reported that the plasma-sprayed HA coatings began to decompose at 800 °C during vacuum heat treatment. It is well known that the HA structure is thermally stable up to 1250 °C in air [6] and to 1050 °C in vacuum [7]. So it is hypothesized that the destruction of HA structure in H A T i or HA-TiO: systems at lower temperatures than 1000°C is completely related to the titanium and its dioxide. In the present study, HA powder was pre-heat-treated at 1200 °C for 120 min (the XRD pattern showing no decomposition) and then mechanically mixed with titanium and titanium dioxide powders. The mixtures were pressed into circular plates and sintered for 30 rain in vacuum and for 60 min in air, separately, at different temperatures. The stability of the starting H A powder was also proved by heating it in vacuum (<1.333 x 10 -3 Pa) at 1000 °C for 30 min, showing the same reflection patterns as those of the standard HA structure. The XRD patterns were determined on a RIGAKU diffractometer (D/max-y A) with Cu-Ko~ radiation at 45-50 kV and 140160 mA. The XRD patterns in Fig. 1 exhibit phase compositions of the mixture of HA and titanium sintered at different temperatures in vacuum. The decomposition of HA induced by titanium begins at 800 °C with the appearance of traces of o: tricalcium phosphate (oL-TCP) and tetracalcium phosphate (TCPM). With the increase of temperature, this process becomes more extensive and no other phase is produced besides cr-TCP and TCPM. The results are identical with our previous reports [3] concerning the thermal
TL;DR: In this article, secondary and secondary alcohols are oxidised by H2O2 in the presence of titanium silicalite-1 to carbonylic compounds, and the reaction pattern is consistent with a process taking place essentially inside the zeolite channels.
TL;DR: It was shown that as the thickness of the titanium oxide layers increased, blood compatibility of these layers was obviously improved, and it was identified that the Titanium oxide layers had rutile structure.
Abstract: Structure characteristics of titanium oxide layer on titanium matrix were investigated by Rutherford Backscattering Spectroscopy (RBS), Auger Electron Spectroscopy (AES) and X-ray diffraction. It has been identified that the titanium oxide layers had rutile structure. The blood compatibility of the titanium oxide layers of different thickness was studied by blood clotting time measurement. It was shown that as the thickness of the titanium oxide layers increased, blood compatibility of these layers was obviously improved.
TL;DR: The use of a bonding agent improves the bond strength of porcelain-fused-to-milled titanium and cast high palladium/conventional porcelains.
TL;DR: In this article, thin electrically insulating films of titanium oxide on titanium have been investigated as adhesion layers between gold and a wide variety of insulators, showing that sputter-deposited titanium films grow by an island growth (Volmer-Weber) mechanism.
TL;DR: The aim of the present work was to produce HA coatings without the shortcomings of those produced by plasma spraying, and hot isostatic pressing at 850 degrees C and 1000 bar with no holding time was applied for this purpose.
Abstract: Plasma spraying is a technique currently used in the production of HA-coated titanium implants. These coatings have been shown to be porous; they dissolve and have a weak bond to the substrate. The long-term interface strength has been questioned in particular. The aim of the present work was to produce HA coatings without the shortcomings of those produced by plasma spraying. Hot isostatic pressing (HIP) at 850 degrees C and 1000 bar with no holding time was applied for this purpose. Initially, the HA powder was mixed with water and air sprayed on the Ti substrate. The Ti specimens were then cold-pressed, enclosed by a protective Pt foil, and encapsulated in an evacuated glass ampulla. Subsequent to HIP, the glass and the Pt foil were removed. These coatings were denser than those produced by plasma spraying. The bonding was measured to be > 62 MPa, which is considered to be satisfactory. The structure of the coating was checked by X-ray diffraction and IR spectroscopy, and was found to correspond to that of HA. Some cracks were observed in the coating running predominantly vertical to the surface. Whether these are acceptable has to be verified by in vivo experiments.