Showing papers on "Titanium published in 1989"

Spectroscopic Characterization of Silicalite and Titanium-Silicalite

Abstract: Surface characterization of silicalite and titanium-silicalite is made by combined use of IR and UV-Vis reflectance spectroscopy. The nature of the IR modes and of the electronic transitions associated with framework titanium is discussed in detail. The perturbation caused by the adsorption of small polar molecules (H 2 O, NH 3 , CH 3 OH) on both the IR and UV-Vis spectra is discussed in terms of the formation of six-coordinated complexes by ligand insertion in the Ti(IV) coordination sphere. All the Ti(IV) is accessible to the interaction with the molecules.

Reduction of oxides of iron, cobalt, titanium and niobium by low-energy ion bombardment

Abstract: Ion-beam bombardment of solid surfaces with rare gas ions is used extensively in conjunction with XPS and AES for surface cleaning and depth profiling. It is sometimes not appreciated that the process can give rise to extensive chemical changes in the surface to be examined. The purpose of this investigation is to study this ion-induced chemical damage. As a vehicle for this, changes in the elemental chemical states associated with some transition metal oxides have been examined using XPS, when the oxides were subjected to progressive periods of argon ion bombardment. Chemical reduction of all oxides investigated has been observed and the data have been compared with theoretical predictions from a current model for preferential oxygen removal. Measurements of the core electron energy levels in oxides and some hydroxides of iron, cobalt, titanium and niobium have been made and the results are tabulated.

Electron energy loss and X-ray absorption spectroscopy of rutile and anatase: a test of structural sensitivity

Abstract: The electron energy loss and X-ray absorption spectra of two phases of titanium dioxide-rutile and anatase-are reported. Although the nearest-neighbour environments of titanium and oxygen in both these structures are very similar, noticeable differences are observed between the electron energy loss and the X-ray absorption spectra. Attempts to model these differences using real-space multiple-scattering calculations are reasonably successful at the Ti K and O K edges. The authors propose an interpretation of the Ti L2.3 edge, notably for the presence of a previously unobserved splitting on the L3 edge.

Titanium gel made from metallic titanium and hydrogen peroxide

Abstract: Various titanium-peroxo intermediates may be formed in the Ti-H2O2 redox process. In a catalytically decomposed Ti-H2O2 system, an oxidizing transparent yellow-green gel with a final pH between 3 and 4 is typically formed within 48 h without addition of chelating agents. The redox potential of the gel is larger than that of the Fe(II)/Fe(III) system. The total Ti concentration in the studied gel was spectro-photometrically determined to be about 45 mM. The oxidizing component was determined to be about 15 mM with the use of iodometric titration. A model for the catalytic H2O2 decomposition is discussed, and an explanation for the existence of an ESR-active radical component in the gel is suggested. The possible relation of the gel formation to the known biocompatibility of titanium is speculated on.

Titanium dioxide dielectric films formed by rapid thermal oxidation

Abstract: High dielectric constant titanium dioxide thin films have been formed on silicon substrates by the rapid thermal oxidation of evaporated titanium. Oxidation of titanium at temperatures between 450 and 800 °C for periods of 1–60 s has been studied. Rutile polycrystalline layers of 800–2000 A thickness were formed. Dielectric constants were in the range of 58–77 for titanium dioxide on silicon. High oxidization temperatures gave leakage currents of 10−7 A at 0.3 MV cm−1 for a 1500‐A‐thick layer, and potential is seen for improved results with thinner layers.

Mechanisms of inclusion formation in Al−Ti−Si−Mn deoxidized steel weld metals

Abstract: The present investigation is concerned with basic studies of the mechanisms of inclusion formation in submerged arc (SA), gas metal arc (GMA), and flux cored arc (FCA) steel weld metals. Theoretical models of deoxidation have been developed to establish a basis for quantitative predictions of important inclusion characteristics, such as volume fraction, size, and chemical composition from knowledge of weld metal chemistry and operating parameters. The relevance of these models has been tested against extensive inclusion data obtained from scanning electron microscope (SEM) and scanning transmission electron microscope (STEM) examinations of a large number of experimental welds containing various contents of aluminum, titanium, silicon, manganese, and oxygen.

Coated glazing material

Abstract: A substrate of glazing material carries a multi-layer coating which comprises a reflective layer of silver sandwiched between a transparent undercoat and a transparent overcoat. The undercoat for the silver layer comprises at least one layer of a metal oxide selected from tin oxide, titanium dioxide, aluminium oxide, bismuth oxide and a mixture of two or more thereof, over which is deposited a layer of zinc oxide having a thickness not greater than 15 nm. The overcoat for the silver layer comprises a layer of an oxide of a sacrificial metal selected from the group consisting of titanium, aluminium, stainless steel, bismuth, tin and mixtures of two or more thereof, which is formed by initial deposition of the sacrificial metal and its conversion to oxide. For forming a low emissivity coating with good light transmission, the silver layer is 8 to 12 nm thick. A specific multi-layer low emissivity coating is formed by depositing the following layers, starting from the substrate surface: Undercoat 3 nm titanium dioxide 20 nm tin oxide (SnO2) 13 nm zinc oxide Reflective layer 10 nm silver Overcoat 3.5 nm titanium for conversion to titanium dioxide 22 nm tin oxide 12 nm titanium dioxide.

Preparation of small-pored crystalline titanium molecular sieve zeolites

Abstract: A process for producing new crystalline titanium molecular sieve zeolite compositions having a pore size of about 3-5 Angstrom Units is disclosed.

The in vivo auto-oxidation of polyether polyurethane by metal ions

Abstract: The first large scale use of polyether polyurethane elastomers in long term human implants was as insulation for cardiac and neurologic pacing leads. While the performance of these polymers has generally been very good over a 14-year period, several failure mechanisms have been discovered that involve interactions between the devices, materials and the body. One of these is auto-oxidation of soft segment ether through the intermediate action of certain transition metal ions, derived from conductor wires by corrosion processes. Biologically produced oxidants appear to be an accelerating factor. In this study, Pellethane 2363-80A tubing containing conductor coils or mandrels of various metals or controls were implanted in rabbits. Explants were analyzed as a function of implant time by optical and scanning electron microscopy, electron dispersive analysis by X-ray, stress-strain, FTIR, GPC and AA spectrophotometry. Only cobalt produced bulk oxidative degradation while surface damage was found in the presence of cobalt bearing alloys. No evidence of significant auto-oxidation was found in the presence of silver, nickel, chromium, molybdenum, iron, titanium, platinum, 304 stainless steel, glass or empty tubing. The combination of polyether polyurethane and metals (especially those containing cobalt) in an implantable device must be carefully evaluated for biostability prior to human use.

Kinetics of Layer Growth and Multiphase Diffusion in Ion-Nitrided Titanium

Abstract: Pure titanium specimens were ion nitrided in a nitrogen plasma in the temperature range of 800 ‡C to 1080 ‡C at various nitrogen partial pressures. During ion nitriding, titanium nitrides TiN and Tiin2N and nitrogen solid solution layers (α and Β) were formed consistent with the equilibrium phase diagram. The kinetics of growth of these layers were studied as a function temperature and ion-nitriding parameters. An analytical diffusion model for multiphase diffusion was used to calculate the diffusion coefficients of nitrogen in the phases of the Ti-TiN system from layer growth experiments. Using the layer growth data, the temperature dependence of nitrogen diffusion in TiN (δ), Ti2N (e), and α titanium was found to obey the following relations: Dinδ=4.4±1.62 × 10su-5 exp-36,500±1400/RT Dine=2.7±1.05 ×10su-3 exp-35,760±2500/RT Dinα=0.96±0.08 × exp-51,280-505/RT

Ziegler-Natta catalyst

Abstract: A process of the Ziegler-Natta type is prepared using a preactivated support containing (A) from 80 to 95 mol % of magnesium chloride and (B) 5 to 20 mol % of at least one electron donor compound which contains no labile hydrogen and no ester function; the preactivated support consisting of spherical particles having a mass average diameter, Dm of 10 to 100 microns and a particle size distribution Dm/Dn of less than 2. The catalyst is prepared by (i) treating the preactivated support with at least one electron donor compound containing labile hydrogen, (ii) treating the resulting activated support with at least one ester of an aromatic acid, (iii) impregnating the treated support with titanium tetrachloride and (iv) after washing the impregnated catalyst activating it with titanium tetrachloride. The catalyst has a high titanium content and a high activity when used to polymerize olefins.

Multiple metal coated superabrasive grit and methods for their manufacture

Abstract: Multiple metal coated diamond grit for improved retention in a tool matrix comprises a first layer coating of a metal carbide of a strong carbide former, preferably chromium, titanium or zirconium, chemically bonded to the diamond and a second metal coating of an oxidation resistant carbide former, preferably tungsten or tantalum, chemically bonded to the first metal layer. A third metal layer coating of an alloying metal, preferably nickel, can also be added. In accordance with the method of the present invention, the first layer metal can be applied by metal vapor deposition. The second layer metal can be applied by chemical vapor deposition. The third layer of an alloying metal can be applied by electroless or electrolytic plating.

Titanium mesh and acrylic cranioplasty

Abstract: Since June 1985 100 cranioplasties have been carried out using titanium mesh and acrylic. There have been no complications and no infections. Titanium mesh is virtually radiolucent. Titanium is nonmagnetic and is the most biocompatible metal known.

Process for making CMOS device with both P+ and N+ gates including refractory metal silicide and nitride interconnects

Abstract: A process for making CMOS device wherein the N-channel devices have n+ gates, and the P-channel devices have p+ gates. A TiN local interconnect system is used to connect the two types of gates, as well as providing connections to moat. A titanium nitride layer may be formed by depositing titanium metal everywhere, and then heating the integrated circuit structure in a nitrogen atmosphere. This process may also be used with other refractory metal nitride interconnect layers. In addition to titanium based thin film compositions, other metals can be substituted and used for direct-react silicidation and simultaneous formation of a conductive nitride to form local interconnects, including molybdenum, tungsten, vanadium, cobalt, and others.

Preparation of polycrystalline thin films of CuInSe2 by electrodeposition

Abstract: CuInSe2 thin films with the chalcopyrite structure were electrodeposited on titanium substrates from an acidic sulphate solution containing citrate ions as a complexing agent. These layers were characterized by X-ray diffraction, SEM, X-ray energy dispersive analysis and spectrophotometry of reflected light. The best deposits were obtained atE=−0.97V vs SSE, in a solution adjusted to pH 3.3. The deposition of the binary alloys was also investigated. It was shown that the formation of smooth layers of crystalline definite compounds is correlated with a slow surface process which induces a plateau on the polarization curves.

Catalytic process for the manufacture of oximes

Abstract: The invention concerns a catalytic process for the manufacture of oximes by ammoximation of the corresponding carbonyl compounds, characterized in that the catalyst is a solid composition consisting of silicon, titanium and oxygen, chemically combined with each other, and in that the titanium amount, expressed as Ti02, ranges from 1 to 95% by weight, the XR diffractogam of said composition being a smooth-trend line (halo), typical of the amorphous solids.