Showing papers on "Titanium published in 1988"

Titanium: A Technical Guide

Abstract: Designed to support the need of engineering, management, and other professionals for information on titanium by providing an overview of the major topics, this book provides a concise summary of the most useful information required to understand titanium and its alloys The author provides a review of the significant features of the metallurgy and application of titanium and its alloys All technical aspects of the use of titanium are covered, with sufficient metals property data for most users Because of its unique density, corrosion resistance, and relative strength advantages over competing materials such as aluminum, steels, and superalloys, titanium has found a niche in many industries Much of this use has occurred through military research, and subsequent applications in aircraft, of gas turbine engines, although more recent use features replacement joints, golf clubs, and bicycles Contents include: A primer on titanium and its alloys, Introduction to selection of titanium alloys, Understanding titanium's metallurgy and mill products, Forging and forming, Castings, Powder metallurgy, Heat treating, Joining technology and practice, Machining, Cleaning and finishing, Structure/processing/property relationships, Corrosion resistance, Advanced alloys and future directions, Appendices: Summary table of titanium alloys, Titanium alloy datasheets, Cross-reference to titanium alloys, Listing of selected specification and standardization organizations, Selected manufacturers, suppliers, services, Corrosion data, Machining data

Hydroxyapatite-coated titanium for orthopedic implant applications.

Abstract: The interface mechanical characteristics and histology of commercially pure (CP) titanium- and hydroxyapatite- (HA) coated Ti-6Al-4V alloy were investigated. Interface shear strength was determined using a transcortical push-out model in dogs after periods of three, five, six, ten, and 32 weeks. Undecalcified histologic techniques with implants in situ were used to interpret differences in mechanical response. The HA-coated titanium alloy implants developed five to seven times the mean interface strength of the uncoated, beadblasted CP titanium implants. The mean values for interface shear strength increased up to 7.27 megaPascals (MPa) for the HA-coated implants after ten weeks of implantation, and the maximum mean value of interface shear strength for the uncoated CP titanium implants was 1.54 MPa. For both implant types there was a slight decrease in mean shear strength from the maximum value to that obtained after the longest implantation period (32 weeks). Histologic evaluations in all cases revealed mineralization of interface bone directly onto the HA-coated implant surface, with no fibrous tissue layer interposed between the bone and HA visible at the light microscopic level. The uncoated titanium implants had projections of bone to the implant surface with apparent direct bone-implant apposition observed in some locations. Measurements of the HA coating material made from histologic sections showed no evidence of significant HA resorption in vivo after periods of up to 32 weeks.

Synthesis and Catalytic Properties of Titanium Containing Zeolites

Abstract: The synthesis of titanium containing zeolites and their catalytic properties when used in oxidations of organic substrates with H 2 O 2 are described. The special cases of phenol to hydroquinone/catechol mixture and of propylene to propylene oxide are discussed. It is assumed that Ti IV enters the silicalite structure at random during synthesis: each Ti IV is surrounded by Si IV and isolated from other Ti IV by long Si-O-Si-O sequences. It is proposed that isolated Ti IV have properties different from those of Ti IV having other Ti IV as near neighbours, in particular that isolated Ti ,v have a reduced rate for H 2 O 2 decomposition; this, together with “restricted transition state selectivity” typical of medium pore zeolites gives rise to high yields of useful oxidation products. Analogies and differences with catalysts consisting of TiO 2 deposited on high surface area SiO 2 are discussed.

Hydroxyapatite-coated porous titanium for use as an orthopedic biologic attachment system.

Abstract: The biologic attachment characteristics of hydroxyapatite (HA)-coated porous titanium and uncoated porous titanium implants were investigated. The implants were placed transcortically in the femora of adult mongrel dogs and evaluated after periods of three, six, and 12 weeks. The HA coating was applied using a modified plasma spray process to samples with pore volume and pore size of the porous coating expanded to equal the pore morphology of uncoated porous specimens. Mechanical push-out testing revealed that the bone-porous material interface shear strength increased with time in situ for both the uncoated and HA-coated implants. The use of the HA coating on porous titanium, however, did not significantly increase attachment strength. Histologic and micro radiographic sections yielded similar qualitative results in the amount of bone grown into each system. After three weeks, both systems displayed primarily woven bone occupying approximately 50% of the available porous structure. Six and 12 weeks postimplantation, each system displayed more extensive bone in growth, organization, and mineralization, with only limited areas of immature bone. Histologically, differences were noted at the ingrown bone-porous material interface between the two implant types. The HA coating supported mineralization directly onto its surface, and a thin osseous layer was found lining all HA-coated surfaces. An extremely thin fibrous layer was observed separating the uncoated titanium particle surface from ingrown bone. There was no extensive direct apposition or lining of the ingrown bone to the uncoated porous titanium particle surfaces.

Titanium-carbonitride-based hard alloys for cutting tools

Abstract: The methods of preparation and some intrinsic properties of titanium carbonitrides TiC1−xNx are described. Their thermodynamic stability as a function of temperature and nitrogen pressure has been studied; this is of great importance because of its influence on the sintering process. The fabrication of hard alloys TiC1−xNx-(NiMo) and (Ti, Mo) (C1−xNx) (NiMo) is described as well as the properties of these materials. Cutting tests of these alloys were performed and compared with corresponding tests on classical tungsten-carbide-based hard alloys, showing that carbonitride grades can easily compete with these classical cemented carbides.

Large-pored crystalline titanium molecular sieve zeolites

Abstract: New crystalline titanium molecular sieve zeolite compositions having a pore size of about 8 Angstrom Units are disclosed together with methods for preparing the same and organic compound conversions.

Role of Particle Substructure in the Sintering of Monosized Titania

Abstract: Monosized titania particles (∼0.35-μ diameter) prepared by controlled hydrolysis of titanium tetraethoxide in ethanol were found to be porous agglomerates of ∼6-nm primary particles. The sintering behavior of compacts constituted of monodispersed agglomerates was evaluated, and changes in macroscopic dimensions were correlated with changes in particle microstructure and chemistry. The total volume shrinkage during sintering was ≥87%. Five contributions to the total shrinkage and the temperature ranges for the associated processes were identified: removal of chemisorbed water (from ambient to 250°C), crystallization to anatase (between 250° to 425°C), intra-agglomerate densification (425° to 800°C), conversion of anatase to rutile (600° to 800°C), and inter-agglomerate densification (>800°C). Approximately one-half the compact shrinkage was the result of agglomerate substructure changes. Studies of the agglomerate structural evolution indicated the intra-agglomerate densification and crystallite growth rates are the secondary factors, after compact packing, that influenced microstructure development.

Stability and open circuit breakdown passive oxide film on titanium of the

Abstract: Titanium electrodes that have been passivated by forming an anodic oxide film in acid solution are known to undergo a spontaneous passive-active transition at open circuit after a delay period that depends on the experimental conditions In the present work, the reactivation of the electrode has been investigated, and it has been shown that it arim as the result of uniform chemical dissolution of the oxide film The rate of dissolution, and hence the stability of the oxide, was found to depend on the rate at which the oxide film had been formed as well as on solution composition and temperature The rate of film dissolution in sulphuric acid showed a first order dependence on proton concentration, but high dissolution rates were also measured in alkaline solution (pH 14) The activation energy for film dissolution in 30 mol dm-' H,SOI was found to be 63 kJ mol-' The reduction of the film under galvanostatic conditions was also investigated, and it was established that simultaneous chemical and electrochemical dis8ohItion occurred uniformly across the electrode surface

The effect of plasma‐sprayed calcium phosphate ceramic coatings on the metal ion release from porous titanium and cobalt‐chromium alloys

Abstract: Bone tissue ingrowth in porous materials is enhanced by the deposition of bioactive calcium phosphate ceramic linings onto the pore walls. These bioactive coatings can be deposited using several methods which yield a variety of coating efficiencies and thereby influence the mechanisms and kinetics of ion release from the metal. We analyzed the effect of plasma-spraying hydroxyapatite onto titanium and cobalt-chromium alloys by measuring the release of Ti, Al, V, Co, and Cr in vitro. Plasma-sprayed coatings significantly reduced the Ti and Al release from titanium-based alloy specimens. The tendencies of release from the cobalt-based specimens are less pronounced. The data substantiate that neither localized enhanced passive dissolution of metal ions nor ceramic shielding of the metal occurs. The Scanning Auger Electron Microprobe Spectroscopic data suggest that the dissipation of thermal and kinetic energy of the ceramic particle at the time of impact can produce compositional and structural changes in the metal surfaces. The resulting effects are significant for the titanium alloy but less significant for the Co-Cr alloy system.

The stable and metastable Ti-Nb phase diagrams

Abstract: The phase transformations which occur in the Ti-Nb binary alloy system have been discussed in two recent papers. The phase relationships were investigated by varying alloy composition and thermal history. In this paper, these results are summarized in complete and thermodynamically consistent calculations of the stable and metastable phase diagrams. The calculations of the metastable equilibria are relevant to the Ti-V and Ti-Mo systems, as well as to several other titanium and zirconium-based transition metal alloy systems.

A new method for the preparation of titanium-silicalite (TS-1)

Abstract: Titanium-silicalite can be prepared by subsequent dealumination of ZSM-5 with hydrochloric acid and reaction with titaniumtetrachloride vapour at elevated temperatures. The titanium atoms are probably inserted into lattice vacancies which were formed upon acid leaching.

Literature Survey on Diffusivities of Oxygen, Aluminum, and Vanadium in Alpha Titanium, Beta Titanium, and in Rutile

Abstract: A survey of diffusion data of interstitial oxygen and of the substitutional elements aluminum and vanadium is presented for alpha and beta titanium. It is based on a survey of literature. Oxygen is an important interstitial element in titanium alloys. Oxygen’s large chemical affinity to titanium is indicated by Ti—O bond energy of 2.12 eV,1 comparable to the Ti—Ti bond energy of 2.56 eV.2 Oxygen is difficult to eliminate completely from titanium, and commercial titanium alloys usually contain from 0.10 to 0.20 wt pct oxygen. Oxygen significantly affects the mechanical properties of titanium alloys1,3 and is sometimes used as an alloying element. The effects of oxygen on phase transformation ,4,5,6 Youngs modulus,7,8 hardness,9,10 fracture toughness,11 and other mechanical properties12 have been amply documented. Aluminum and vanadium are the most frequently used substitutional alloying elements. Aluminum is an alpha stabilizer and vanadium is a beta stabilizer.

Laser welding of titanium in dentistry

Abstract: Unalloyed titanium of the quality used for osseointegrated implants by the method of Branemark is also sometimes used for the metallic part of the prosthetic superstructure placed on the fixtures and for crowns and bridges of conventional type. Forty bars of titanium, 8 of ASTM B 348 grade-1 quality and 32 of ASTM B 348 grade-2 quality, were laser-welded, using dissimilar laser joint variables. Tensile strength, 0.2% proof stress, and percentage elongation of the welded bars were measured and compared with the corresponding values for the titanium bars as delivered and with those of brazed type-3 gold alloy bars of similar dimensions. The type of fracture was evaluated from fractographs. The results showed that the use of certain defined laser joint variables during welding produced values for the mechanical properties studied which were more favorable than those obtained from the brazed gold bars. The fracture of the titanium specimens was ductile, with dimples occurring at the fracture surfaces.

Structure property behavior of polydimethylsiloxane and poly(tetramethylene oxide) modified TEOS based sol-gel materials V. Effect of titaniumisopropoxide incorporation

Abstract: Titanium has been successfully incorporated into polydimethylsiloxane and poly(tetramethylene oxide) modified TEOS based materials using sol-gel chemistry. Incorporation of titanium into the oligomer modified TEOS based materials altered the physical properties, however, the gross structural features remained the same.

Method for etching titanium nitride local interconnects

Abstract: A process for the etching of titanium containing film which utilizes both in situ and remote plasmas, and a gas mixture for the plasmas which comprises a halogen gas at low pressure and moderate temperature to produce an etch which is both selective to selected materials, for example, titanium silicide etc., and anisotropic.

Ignition mechanism of the titanium–boron pyrotechnic mixture

Abstract: Titanium–boron pyrotechnic reactions are essentially gasless, are very exothermic, and are known to initiate only at extremely high temperatures. The reactants are stable in normal laboratory environments and require no special sample handling, such as inert storage. These factors make the titanium–boron mixture ideal for one-shot thermal heat source applications. Mound has been investigating energetic material ignition properties for a number of years. Pyrotechnic mixtures of TiHx/KClO4 have revealed that the surface composition of the titanium fuel was TiO2 and its presence on the fuel's surface controls the TiHx + KClO4 reaction. In the present study the surface chemistry of titanium and of boron have been examined before ignition. To understand the effect of temperature on the reactants and the mixture, titanium powder, boron powder, and blends were analyzed at ambient and elevated temperatures. XPS, TG and DTA results presented will show that the oxide on boron is the controlling factor in the ignition mechanism of the titanium–boron pyrotechnic reaction.

Ohmic contacts to semiconducting diamond

Abstract: A solid-state reaction process for producing ohmic contacts to polished natural semiconducting diamond surfaces is discussed The approach attempts to systematically characterize the processes which occur when metallic films of known thickness are deposited on a smooth diamond surface and annealed in the solid state under controlled conditions Annealed tantalum/gold and titanium/gold deposits on

Titanium diffusion in silicon

Abstract: Titanium diffusion profiles in silicon were determined in the 950–1200 °C temperature range, with experimental conditions avoiding any oxygen or nitrogen contamination, which could perturb the boundary condition at the TiSi2/Si interface. Thus diffusivity values in the range 5×10−10–10−8 cm2 s−1 are obtained, and are about two orders of magnitude higher than previously reported.

Processing of anatase prepared from hydrothermally treated alkoxy-derived hydrous titania

Abstract: Spherical, submicrometre, amorphous hydrous titania powder synthesized by controlled hydrolysis and polymerization from titanium tetraethoxide solutions was hydrothermally converted to spherical polycrystalline anatase particles by autoclaving or refluxing. Green compacts produced with either autoclaved or refluxed powder via a colloid filtration route had a high density and were crack-free; processing with untreated hydrous titania resulted in cracked green compacts. Compacts of the hydrothermally treated powders could be sintered to 98% theoretical density at temperatures as low as 900° C. A compact of commercial powder produced in the same fashion was not observed to densify at such temperatures. Using various firing techniques, compacts of the hydrothermally treated powder could be sintered to 98% theoretical density or greater while controlling the titania phase assemblage as (1) anatase, (2) rutile, or (3) a mixture of anatase and rutile. By scaling the phase transformation and sintering kinetics, the grain size of the sintered microstructure can be controlled from a submicrometre to a micrometre scale.

High strength, low modulus, ductile, biopcompatible titanium alloy

Abstract: A high strength, low modulus, ductile, biocompatible titanium base alloy containing one or more isomorphous beta stabilizers, eutectoid beta stabilizers and optional alpha stabilizers, characterized by a modulus of elasticity not exceeding 100 GPa; a method for the preparation of said alloy and prostheses made from said alloy.