Showing papers on "Titanium published in 1996"

An overview on the use of titanium in the aerospace industry

Abstract: Titanium and titanium alloys are excellent candidates for aerospace applications owing to their high strength to weight ratio and excellent corrosion resistance. Titanium usage is, however, strongly limited by its higher cost relative to competing materials, primarily aluminum alloys and steels. Hence the advantages of using titanium must be balanced against this added cost. The titanium alloys used for aerospace applications, some of the characteristics of these alloys, the rationale for utilizing them, and some specific applications of different types of actual usage, and constraints, are discussed as an expansion of previous reviews of β alloy applications. [1,2]

Preparation of bioactive Ti and its alloys via simple chemical surface treatment.

Abstract: A simple chemical method was established for inducing bioactivity of Ti and its alloys. When pure Ti, Ti-6A1-4V, Ti-6A1-2Nb-Ta, and Ti-15Mo-5Zr-3A1 substrates were treated with 10M NaOH aqueous solution and subsequently heat-treated at 600 degrees C, a thin sodium titanate layer was formed on their surfaces. Thus, treated substrates formed a dense and uniform bonelike apatite layer on their surfaces in simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. This indicates that the alkali- and heat-treated metals bond to living bone through the bonelike apatite layer formed on their surfaces in the body. The apatite formation on the surfaces of Ti and its alloys was assumed to be induced by a hydrated titania which was formed by an ion exchange of the alkali ion in the alkali titanate layer and the hydronium ion in SBF. The resultant surface structure changed gradually from the outermost apatite layer to the inner Ti and its alloys through a hydrated titania and titanium oxide layers. This provides not only the strong bonding of the apatite layer to the substrates but also a uniform gradient of stress transfer from bone to the implants. The present chemical surface modification is therefore expected to allow the use the bioactive Ti and its alloys as artificial bones even under load-bearing conditions.

The use of titanium for medical applications in the USA

Abstract: The Ti-6Al-4V ELI alloy is still the main titanium alloy used for medical applications to date. To address the potential safety concerns over vanadium and aluminum, and the possible advantage of using a low modulus material to reduce stress shielding, the development of a low modulus biocompatible implant material was initiated in the United States in 1986. Five beta titanium alloys (TMZFTM, Ti-13Nb-13Zr, TIMETAL® 21SRx, Tiadyne 1610 and Ti-15Mo) are being proposed for surgical implant applications in the United States. Based on published data, the comparative mechanical property data of these beta titanium alloys are presented.

Microporous Crystalline Titanium Silicates

Abstract: Publisher Summary This chapter focuses on the microporous crystalline titanium silicates. Titanium containing materials have been investigated for various reactions, but selective oxidations with H2O2 as the oxidant have attracted the most interest. For these reactions, the formation of surface titanium peroxo compounds with H2O2 and the subsequent transfer of the peroxidic oxygen to the organic reactants have been proposed to explain the mechanism by which titanium participates in the catalytic cycle. H2O2 has the advantage of giving environmentally benign water as its by-product. Furthermore, H2O2 ranks first in terms of available oxygen in the list of oxygen donors.The unusual properties of titanium silicalites have been attributed to the presence of TiIV in framework positions of the SiO2 lattice. It is important to realize that there is a limit to the extent of substitution; the exact value is still under discussion, but is certainly not more than a few percent. Very likely, the structure of crystalline silica is not stable at higher degrees of substitution. The discovery of the new titanium silicates and of their catalytic properties in H2O2 oxidation reactions has had a major impact in catalytic science and its industrial applications.

Room temperature operation of a single electron transistor made by the scanning tunneling microscope nanooxidation process for the TiOx/Ti system

Abstract: The single electron transistor (SET) is fabricated using the scanning tunneling microscope (STM) as a fabrication process, and the fabricated SET operates at room temperature. Using the STM tip as a cathode, the surface of the titanium metal can be oxidized, and the few tens of nanometer wide oxidized titanium line can be made. The small island region of the SET of ∼30×∼35 nm2 is formed by the oxidized titanium line. The Coulomb staircase of 150 mV period is observed in the current–voltage characteristics of the SET at room temperature.

Influence of materials for fixation implants on local infection an experimental study of steel versus titanium dcp in rabbits

Abstract: Resistance to infection may be influenced by foreign bodies such as devices for fracture fixation. It is known that stainless steel and commercially-pure titanium have different biocompatibilities. We have investigated susceptibility to infection after a local bacterial challenge using standard 2.0 dynamic compression plates of either stainless steel or titanium in rabbit tibiae. After the wounds had been closed, various concentrations of a strain of Staphylococcus aureus were inoculated percutaneously. Under otherwise identical experimental conditions the rate of infection for steel plates (75%) was significantly higher than that for titanium plates (35%) (p < 0.05).

TiO2 by XPS

Abstract: The surfaces of titanium oxide belong to the most-studied oxide systems in the surface science literature. This is in part because TiO2 surfaces and interfaces play a major role in several technological applications, e.g., as promoters in catalysis, as photocatalysts, and as gas sensors. TiO2 is a reducible oxide, i.e., several phases with different stoichiometries exist. Because Ti is highly reactive towards oxygen, titanium oxides are formed readily when Ti is exposed to an atmosphere containing water or oxygen. The oxidation behavior of the metal is of interest for the properties of protective coatings. Although accurate knowledge of the XPS binding energies of different oxidation states is necessary for XPS investigations of titanium oxides, a recent review of the 16 literature data of the binding energy of Ti 2p3/2 from Ti4+ showed wide scatter of the reported values with a mean of 458.7 eV and a standard deviation of 1.3 eV [J. Mayer, E. Garfunkel, T. E. Madey, and U. Diebold, J. Electron Spectrosc....

Photocatalytic decomposition of no at 275 k on titanium oxides included within y-zeolite cavities : the structure and role of the active sites

Abstract: Titanium oxide species anchored in the Y-zeolite cavities by an ion-exchange method exhibits a high and unique photocatalytic reactivity for the direct decomposition of NO into N2, O2, and N2O at 275 K with a high selectivity for the formation of N2. The in situ photoluminescence and XAFS (XANES and FT-EXAFS) investigations indicate that the titanium oxide species are highly dispersed in the zeolite cavities and exist in a tetrahedral coordination. The charge-transfer excited state of the titanium oxide species plays a significant role in the direct decomposition of NO with a high selectivity for the formation of N2, while the catalysts involving the aggregated octahedrally coordinated titanium oxide species show a high selectivity to produce N2O, being similar to reactions on the powdered TiO2 catalysts.

Titanosilicate Mesoporous Molecular Sieve MCM-41: Synthesis and Characterization

Abstract: The location and coordination of titanium in the titanosilicate mesoporous molecular sieve MCM-41 prepared from Ti(IV) ethoxide as the source of titanium was studied by XRD, IR spectroscopy, 29Si MAS NMR, and XANES. The results are interpreted on the basis of isomorphous substitution of Ti for Si. XANES shows that titanium is 4-coordinate and that Ti(IV) does not form a regular TiO4 tetrahedron. This is caused by the larger size of the Ti(IV) atom in comparison with Si(IV), resulting in a distortion in the silica matrix, and/or by the presence of H2O in the coordination sphere of titanium. Such distortion is consistent with the line broadening observed in the 29Si MAS NMR spectra, brought about by the wider distribution of the Si−O−Si angles in SiO4 tetrahedra as titanium is progressively incorporated in the silica matrix, and with the changes in the vibrational lattice infrared bands.

Cathodic Electrodeposition of Nanocrystalline Titanium Dioxide Thin Films

Abstract: A new technique for depositing nanocrystalline titanium dioxide thin films on electronically conducting glass was developed. This technique is a two-stage process: (i) cathodic electrodeposition of titanium oxyhydroxide gel film from aqueous solution containing a Ti precursor and (ii) subsequent heat-treatment of this gel film results in the formation of titanium dioxide film. The deposition potential may have a considerable effect on the formation of nanocrystalline film. The nanocrystalline titanium dioxide film shows reversible electrochromism in lithium-ion-containing organic electrolyte. The coloration and bleaching throughout the visible and near-IR range can be switched on and off within a few seconds.

Titanium(IV)Oxide Thin Films Prepared from Aqueous Solution

Abstract: Titanium oxide thin film could be prepared from (NH4)2TiF6 aqueous solution with addition of boric acid by Liquid Phase Deposition (LPD) process. The aspect and chemical composition of the deposited films were different according to the concentration range of (NH4)2TiF6 and H3BO3 in the treatment solution. The deposition rate of transparent TiO2 film increased with increasing concentration of added H3BO3.

Sol−Gel-Processed SiO2/TiO2/Poly(vinylpyrrolidone) Composite Materials for Optical Waveguides

Abstract: SiO2/TiO2/poly(vinylpyrrolidone) (PVP) composite materials processed by the sol−gel technique were studied for optical waveguide applications. Change of refractive index through the range 1.39−1.65 at 633 nm (optical wavelength) was achieved by varying the ratio between the SiO2 and TiO2 concentrations. To produce low optical propagation loss in the waveguide, it was necessary to avoid the precipitation of TiO2 particles caused by the fast hydrolysis reaction of titanium alkoxide. By using titanium ethylhexoxide as a titanium alkoxide together with acetic acid and 2-propanol as the solvent, the precipitation of TiO2 was avoided in the TiO2 concentration range of up to 30 wt %, resulting in low optical propagation losses in the slab waveguide configuration. In the higher TiO2 concentration range, an additional measure, peptization was necessary. With this method, we could produce optical waveguides possessing optical propagation losses of 0.62 dB/cm or lower at 633 nm. Low optical propagation loss in all t...

A pilot study on the percutaneous absorption of microfine titanium dioxide from sunscreens

Abstract: Many Australians are being advised to apply microfine titanium dioxide sunscreen daily from the cradle to the grave. However, there is a surprising lack of data on the percutaneous absorption of microfine titanium dioxide. A prospective pilot study was conducted to analyse the percutaneous absorption of microfine titanium dioxide from sunscreens. Selected patients scheduled to have skin surgery, applied titanium dioxide sunscreen to the skin daily for 2-6 weeks prior to their operation. After excision, the stratum corneum of the sample was stripped and the titanium concentration of the remaining epidermis and dermis was measured by inductively coupled plasma-mass spectrometry. The results from this pilot study showed that levels of titanium in the epidermis and dermis of subjects who applied microfine titanium dioxide to their skin were higher than the levels of titanium found in controls. Studies with larger cohorts are necessary to establish if this absorption is statistically significant.

The oxidation and protection of gamma titanium aluminides

Abstract: The excellent density-specific properties of the gamma class of titanium aluminides make them attractive for intermediate-temperature (600–850 °C) aerospace applications. The oxidation and embrittlement resistance of these alloys is superior to that of the α2 and orthorhombic classes of titanium aluminides. However, since gamma alloys form an intermixed Al2O3TiO2 scale in air rather than the desired continuous Al2O3 scale, oxidation resistance is inadequate at the high end of this temperature range (i.e., greater than 750–800°C). For applications at such temperatures, an oxidation-resistant coating will be needed; however, a major drawback of the oxidation-resistant coatings currently available is severe degradation in fatigue life by the coating. A new class of oxidation-resistant coatings based in the Ti-Al-Cr system offers the potential for improved fatigue life.

Metal implants and surface reactions

Abstract: A metal in living tissue is prone to corrosion. The interaction of the foreign body with the tissue involves the redox reaction (an electron exchange) at the interface, the hydrolysis (a proton exchange) of oxidehydrates as products of corrosion, and the formation of metal-organic complexes in the electrolyte. Denatured tissue in contact with the foreign body is the consequence. But behaviour of metals is variable; gold, stainless steel and most other metals react as described while few others like titanium and tantalum do not. The absence of a foreign body effect of a chemical kind is, without doubt, favorable in terms of tissue susceptibility to infection in the presence of titanium.

METALLIC GLASS ALLOYS OF Zr, Ti, Cu AND Ni

Abstract: At least quaternary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 103 K/s. One group of such alloys comprise titanium from 19 to 41 atomic percent, an early transition metal (ETM) from 4 to 21 atomic percent and copper plus a late transition metal (LTM) from 49 to 64 atomic percent. The ETM comprises zirconium and/or hafnium. The LTM comprises cobalt and/or nickel. The composition is further constrained such that the product of the copper plus LTM times the atomic proportion of LTM relative to the copper is from 2 to 14. The atomic percentage of ETM is less than 10 when the atomic percentage of titanium is as high as 41, and may be as large as 21 when the atomic percentage of titanium is as low as 24. Furthermore, when the total of copper and LTM are low, the amount of LTM present must be further limited. Another group of glass forming alloys has the formula: (ETM?1-x?Tix)aCub(Ni1-yCoy)c, wherein x is from 0.1 to 0.3, y?.?c is from 0 to 18, a is from 47 to 67, b is from 8 to 42, and c is from 4 to 37. This definition of the alloys has additional constraints on the range of copper content.

Hydrogen peroxide toward enhanced oxide growth on titanium in PBS solution: blue coloration and clinical relevance.

Abstract: Oxide films formed on titanium exposed to a phosphate-buffered saline solution with and without hydrogen peroxide (H2O2) addition were investigated by means of electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The oxide growth at the titanium/electrolyte interface was monitored in situ by daily EIS measurements during periods of several weeks. The results suggest that the oxide film can be described by a two-layer model with a barrier inner layer and a porous outer layer. H2O2 addition results in an increased dissolution/oxidation rate that leads to an enhanced oxide growth of the porous outer layer. As a result, the total oxide film can reach a thickness corresponding to an interference blue color. Based on XPS results, H2O2 addition furthermore seems to facilitate the incorporation of phosphate ions into the thicker porous layer. This observation may be related to the so-called osseointegration properties of titanium. © 1996 John Wiley & Sons, Inc.

Synthesis and structure of a layered titanosilicate catalyst with five-coordinate titanium

Abstract: TITANIUM occurs widely in the Earth's crust, traces of it being present in most rocks, soils and clays. It is estimated that titanosilicate minerals alone number more than 100; but, remarkably, in only one of these does the Ti(IV) ion take up fivefold coordination. This is in fresnoite1 (Ba2TiSi2O8), which contains square-pyramidal TiO5 polyhedra. In the course of a programme2–11 to produce new microporous and mesoporous solid catalysts, we have discovered an unusual non-centrosymmetric, tetragonal layered solid (Na4Ti2Si8O22·4H2O), designated JDF-L1, which promises to have interesting applications in materials chemistry. This material contains five-coordinate Ti(IV) ions in the form of TiO5 square pyramids in which each of the vertices of the base is linked to SiO4 tetrahedra [TiO·O4(SiO3)4] to form continuous sheets. The structure was solved by applying ab initio methods to data obtained by X-ray absorption spectroscopy and powder X-ray diffraction. The interlamellar Na+ ions of JDF-L1 are replaceable by protonated amines, and after treatment with a mixture of dilute acid and hydrogen peroxide the parent solid selectively oxidizes phenol to quinone. These results indicate that the material should have useful catalytic, intercalation and ion-exchange properties analogous to those of aluminosilicate clays.

Titania Coatings on Monodisperse Silica Spheres (Characterization Using 2-Propanol Dehydration and TEM)

Abstract: Titania coatings ranging from sub-monolayer to ≈7 nm thick have been deposited on silica by hydrolysis of titanium alkoxide precursors. Nonporous model silica particles of spherical shape were used as the support for titania. The ratio of titanium alkoxide to water and the dilution of the reactant mixture in ethanol control the nature of the coating. If the alkoxide concentration is too high, precipitation of second-phase titania particles occurs rather than a uniform coating. On the other hand, higher water concentrations led to aggregated spheres being connected with titania necks. Isolated silica spheres with uniform coatings of titania are obtained when the alkoxide concentration is kept low. The samples were studied using transmission and scanning electron microscopy. 2-Propanol dehydration was used as a probe reaction, since it was found that reactivity for propene formation is directly correlated with anatase surface area. Using this correlation, the effective titania surface area of each sample co...

Environment purifying material

Abstract: The present invention is directed to a sheet-form environment purifying material comprising particles of metal and/or metal oxide consisting essentially of at least one member being selected from the group consisting of manganese, copper, zinc, iron, vanadium, nickel, titanium, palladium, platinum, manganese oxide, copper oxide, zinc oxide, iron oxide, vanadium oxide, nickel oxide, titanium oxide, palladium oxide, and platinum oxide, adsorbent particles consisting essentially of at least one member selected from the group consisting of activated carbon, zeolite, silica gel, sepiolite, activated alumina and activated clay, thermoplastic resin particles being selected from ultrahigh-molecular weight polyethylene, polyethylene, polycarbonate, polyamide acrylonitrile-butadiene-styrene resins, polyimide, polyvinyl chloride, cellulose acetate, polysulfone, polystyrene phthalate and polypropylene, and an air-permeable sheet of fibrous. The metal and/or metal oxide particles and the adsorbent particles are respectively bound to the thermoplastic resin particles while retaining their inherent surface areas and performances without being covered by the thermoplastic resin layers, and the thermoplastic resin particles are joined to the fibrous substrate. The present invention is also directed to a process for making the environment purifying material which comprises the steps of mixing all the particles and heating the mixture at a temperature not lower than the melting point of the thermoplastic resin and not higher than the thermal decomposition temperature thereof. The environment purifying material of the present invention is useful as deodorizers and harmful gas removers.