Showing papers on "Titanium published in 1973"

Anodic oxidation of titanium and its alloys

Abstract: This review deals with the procedures used in the anodic oxidation of titanium and its alloys, the nature and properties of the oxide films, their uses, and the trends in research and development.

Changes in nonosseous tissue adjacent to titanium implants

Abstract: A combined histological, metallurgical, and clinical study has been made in 19 instances where a surgical operation had been performed to remove a titanium implant used in the treatment of disease or trauma in man. All the implants were static devices such as pins, plates and rods. Histological examination of nonosseous tissue excised from adjacent to the implant was supplemented by estimation of its titanium content by neutron activation analysis. The results indicate that in some patients titanium can be liberated into tissue adjacent to titanium implants. The phenomenon can occur in the absence of corrosion or fracture of the implant, and is unrelated to the possible liberation of wear particles from an artificial articular surface. There is variation from individual to individual in the amount, if any, of titanium released. In the case of those implants showing titanium release, the results suggest that local release of the metal, or its subsequent accumulation in the tissue, is a patchy process at the implant site. The histological features of the local reaction of nonosseous tissue to titanium release are described. No conclusions have been drawn concerning possible effects on the osteogenic response to the insertion of the implants and on the overall state of the bone at the time of their removal. From study of the clinical records it is apparent that considerable caution is needed before concluding that release of titanium can cause clinically significant local effects. Although such effects may have occurred in a minority of patients, this possibility is by no means proven. A distinction must be drawn between a “metal reaction” in the histological sense and a “metal reaction” in the clinical sense.

Characteristics of aluminum-titanium electrical contacts on silicon

Abstract: An aluminum‐titanium metallization scheme for use in silicon integrated circuits is described. This metallization can produce high‐conductance electrical contacts with negligible dissolutions of silicon. The desirable contact is lost, however, if a TiAl3 reaction product is allowed to consume the entire Ti layer. The TiAl3 forms during the postmetallization heat treatment used to stabilize the electrical characteristics of the contact. The Ti layer is found to be consumed in this reaction at a rate proportional to t1/2, where the rate constant is determined to be d=d0 exp(−Ea/kT), where d0 ≈ 0.15 cm2/sec and Ea ≈ 1.85 eV. This rate constant can be used to determine the thickness of titanium layer necessary to produce the desirable electrical contact.

Olefin polymerization catalyst

Abstract: A method for preparing a composition of matter comprising silica and titanium, convertible to a catalyst suitable for olefin polymerization by the addition of chromium and the process performable therewith, the preparation involving adding an alkali metal silicate to an acid containing a titanium compound, and recovering a dry gel for use as a polymerization catalyst upon the addition of chromium.

The wetting of carbon and carbides by copper alloys

Abstract: In a previous paper (J. Mater. Sci.5 (1970) 149) a model was developed to predict the wetting behaviour between carbon and copper alloys containing 1 at. % of a carbide forming element. In the present paper it is shown that the model can be applied successfully to alloys containing as little as 0.15 at. % chromium or vanadium and as much as 13 at. % titanium. A further development of the model is its use to predict carbide surface energies, the values derived being in good agreement with literature data.

Diffusion of hydrogen in titanium alloys due to composition, temperature, and stress gradients

Abstract: A theoretical and experimental study was conducted to determine the combined effects on interstitial diffusion in metals of gradients in interstitial concentration, in solvent composition, in stress, and in temperature. The theory consolidates relationships, some of which have been previously published. It is based on macroscopic irreversible thermodynamics, and is applicable to anisotropic or Isotropic materials. Experiments were conducted and literature analyzed to determine the numerical quantities required to predict the change in hydrogen distribution with time for pure and alloy titanium, where the solvent gradient, stress gradient, and temperature gradient are constant with time. The diffusion driving forces for solute gradient, solvent gradient, and stress gradient are related to the effect of each factor on hydrogen activity. In addition, the material property which determines the diffusion driving force of a stress gradient for anisotropic material is a matter tensor analogous to the scalar partial molal volume used for isotropic material. The experiments, conducted with commercially pure titanium and titanium alloy, 6A1-4V, consist of measuring the effect of alloy additions and stress on the hydrogen activity in solid solution and the dilatation effect of hydrogen. Stress states tested were tension, compression, and torsion. The measurements were made by exposing titanium and the alloy to hydrogen at temperatures from 600° to 800° C, and measuring the equilibrium hydrogen gas pressure at various solid solution hydrogen contents. Both materials were tested with and without stress. Tension decreased the activity, compression increased it, and torsion had no effect. This is consistent with the stress effect theory of Li, Oriani, and Darken. The stress effect corresponds to an apparent partial molal volume of 1.7 to 2.2 cm3/mol, depending on the alloy and hydrogen content.

Reactivity and interface characteristics of titanium-alumina composites

Abstract: The reaction kinetics between α-Ti alloys and single crystal sapphire, the phase composition and morphology of the reaction-zone, and the phase compatibility in the system Ti-Al-O were investigated as part of a study to determine the feasibility of fabricating useful Al2O3-reinforced titanium matrix composites. In the temperature range 650 to 1000° C titanium reduces Al2O3 to form a complex reaction layer consisting of two distinct zones; an inner zone adjacent to the Al2O3 of a TiO phase containing isolated particles of (Ti, Al)2O3, presumably, and an outer zone of a Ti3Al phase adjacent to the Ti matrix. The isothermal growth of the reaction layer follows a parabolic rate law. The temperature dependence of the rate constants fits an Arrhenius equation yielding activation energies of 50 to 52 kcal/mol. The high Al alloys, except Ti-6Al-2Sn-4Mo-2Zr, reacted more rapidly than pure Ti indicating that Al diffusion through the reaction zone may be the rate-limiting step.

Diamond particle having a composite coating of titanium and a metal layer

Abstract: A diamond particle of the MD or the SD type having a composite coating comprising a thin continuous layer of titanium adjacent the diamond surface and a metal layer on the titanium layer, the metal of the metal layer being capable of forming an alloy with titanium under the influence of heat and the titanium/diamond interface being essentially free of chemical bond formation. The invention further provides a method of making a metal bonded abrasive device which includes the steps mixing the above described particles with a suitable metal matrix, heating the mixture to a temperature exceeding 500*C, maintaining the mixture at the elevated temperature for a period of from 10 to 30 minutes, and allowing the mixture to return to ambient conditions.

Relationship between deformation twinning and the stress-strain behavior of polycrystalline titanium and zirconium at 77 K

Abstract: The 77 K stress-strain curves of high purity Zr, commercial purity Zr, high purity Ti and commercial purity Ti, which are all significantly different, were analyzed by the Crussard and Jaoul method. The evolution of the mechanical twin structure in these specimens was also studied using quantitative optical microscopy. It was generally observed that changes in the nature of the twin structure development correlated with changes in the C-J deformation stages. Constant work hardening rate stages tend to appear at higher strains if the rate of increases of the twin volume fraction is large.

Synthesis of bis-π-benzene-titanium and -molybdenum using metal vapours

Abstract: Bis-π-benzene-titanium and -molybdenum are formed by co-condensation of benzene vapour with the metal vapours at 77K.

Orientation dependent slip in polycrystalline titanium

Abstract: The factors determining the active slip systems in cold-rolled polycrystalline titanium sheet were investigated. The texture of such a sheet has an important role in determining the active slip systems. Equi-Schmid factor lines for different slip modes were calculated, and transmission electron microscopy proved that pile ups of dislocations of the predicted systems are formed. The active primary slip system was found to be the prismatic a type slip {1¯100} 〈11¯20〉 while the secondary system is either prismatic or pyramidal type I {10¯11}. Basal slip of a dislocations could in certain orientations of load direction be the primary slip systems. Dislocations of the (c + a) type play no significant role in the plastic deformation of polycrystalline titanium sheet.

Decomposition of the α-phase in titanium-rich Ti-Al alloys

Abstract: Decomposition of the α-phase in Ti-Al alloys in the range 6.8 to 19.2 at. pct Al was investi-gated using electrical resistivity measurements and transmission electron microscopy. The solvus line between the α and α+ α2 regions was found to be somewhat higher than that re-ported by Blackburn. Short range ordering both above and below the solvus in 6.8 and 10.0 pct Al alloys was indicated by the resistivity measurements. In alloys containing 14.2 to 19.2 pet Al the precipitation process follows a C-curve behavior with a maximum rate at about 600°C.

Silylmethyl and related complexes. Part I. Kinetically stable alkyls of titanium(IV), zirconium(IV), and hafnium(IV)

Abstract: Complexes of the type Cp2M(CH2M′Me3)2(Cp =π-C5H5; M = Ti, Zr, or Hf; M′= Si or Ge) have been prepared from Me3M′CH2Li, or less satisfactorily from the Grignard reagent, and Cp2MCl2 in ether. Cp2Zr(Cl)CH2SiMe3 was prepared via Me3SiCH2MgCl in ether–methylene chloride. Isoleptic complexes (RnMe3 –nSiCH2)4M (M = Ti, Zr, or Hf; n= 0–2; R = Ph or PhCH2) have been prepared by the reaction of MCl4 with Me3SiCH2Li in ether or hexane, RnMe3 –nSiCH2MgCl in ether, or (RnMe3 –nSiCH2)2Mg in hexane. The complexes are thermally more stable than their methyl analogues; oxidative stabilities of the isoleptic compounds correlate with the degree of steric shielding at the metal centre. Spectroscopic data are provided, and the reactions of the isoleptic compounds with water, iodine, and acetylacetone are described.

Point Defects and Extended Defects in Niobium Oxides

Abstract: THE part played by true point defects—isolated vacancies and interstitial atoms—in defect solid solutions and in mixed valence non-stoichiometric phases is not clear. In many ionic or quasi-ionic structures there is some structural reorganization and at least incipient ordering of defect clusters. In some oxides—notably those of titanium, vanadium, molybdenum and tungsten, in which the covalent component of the bonding is probably strong—slight reduction, with a change in the ratio of oxygen to metal, is accommodated largely by crystallographic shear. A complete sheet of anion sites is eliminated from the structure, forming an extended defect and greatly diminishing the extent to which a deficit of oxygen must be compensated by anion vacancies or interstitial cations. Thus Hyde and Bursill1 found that, in slightly reduced rutile, TiO1.9986, the point defect concentration could hardly exceed 10−4. In more extensively reduced rutile, changes in stoichiometry involve only changes in the spacing between crystallographic shear planes, without detectable concentrations of localized defects.

Large‐angle L x‐ray production by electrons

Abstract: Experimental values are given for the yields and spectral energy purities of K x‐ray beams emitted at 120° and 180° from various targets when bombared by 0.01‐ to 3.0‐MeV electron beams. Yields and purities are determined for beryllium, carbon, aluminum, titanium, copper, silver, and gold targets as a function of the target thickness and target inclination angle.

Polymerization of ethylene

Abstract: Ethylene polymers are made by bringing ethylene under polymerization conditions at low pressures into contact with a catalyst comprising a titanium halide, a vanadium halide and an organoaluminum compound. Molecular weight distribution of the polymers is controlled by reacting the titanium halide, the vanadium halide and the organoaluminum compound in such proportions that the Al/(Ti+V) ratio is between about 0.1 and 0.5 and admixing the resulting catalyst complex with a mixture of an alkylaluminum sesquiethoxide and a trialkylaluminum prior to contacting of ethylene therewith.

Method of anodizing titanium to promote adhesion

Abstract: Porous, adhesion-promoting oxide coatings are formed on titanium by anodizing in an aqueous solution containing fluoride ion and one or more oxidizing electrolytes at current densities of from 0.25 to 5 amp./ft. 2 .