Showing papers on "Titanium published in 1979"
TL;DR: It is shown that titanium and Ti-6Al-4V should withstand exposure to physiological chloride solutions at body temperature indefinitely and is proposed that the needless can be broken off or dissolved in vivo.
Abstract: The excellent corrosion resistance of titanium and its alloys to physiological chloride solutions is well documented. Occasionally, however, titanium compounds have been found in tissue adjacent to titanium implants. These findings were reported to be unrelated to wear processes, suggesting that either the metal or its passive film was dissolving. The unpredictability of these findings further suggests that preimplantation surface treatments and/or variations in the physiological environment may be factors. To determine a mechanism by which titanium can be released from an implant a study was initiated which employed electrochemical techniques, Auger electron spectroscopy (AES), and replica transmission electron microscopy (RTEM). Specifically, the purpose was to characterize the passive film on titanium and Ti-6Al-4V, and to determine if there is dissolution of the film or metal in a static unstressed state. Passive film behavior of commercially pure titanium, Ti-6Al-4V and nitrided Ti-6Al-4V was studied by anodic polarization and pulse potentiostatic capacitance techniques in Ringer's solution at 37°C with and without physiological additions of several amino acids. Solution Po2, pH, and specimen surface finish were varied to include all probable in vivo conditions. In all tests, potentiostatic anodic polarization of each material yielded potential-current density curves which showed passivity over the entire experimental range. This range greatly exceeded the oxygen-reduction reversible electrode potential. No breakdown potentials were observed. The passive current density was not significantly affected by varying the experimental parameters. AES as well as charge and capacitance measurements showed that the electrochemical reaction which occurred was growth of the passive film. The data indicated that the effective electrochemical area of each specimen was less than its geometrical area, and was dependent on both pH and surface finish. The findings of this study showed that, under static conditions, titanium and Ti-6Al-4V should withstand exposure to physiological chloride solutions at body temperature indefinitely. Furthermore, the findings are consistent with a model of the implant surface inwhich the naturla air oxide that initially forms on an abraded implant surface is comprised of microscopic oxide needles. It is proposed that (i) the needless canbe broken off or dissolved in vivo, providing the source of the titanium sometimes found in tissue adjacent to an implant, and (ii) use of certain pretreatments may remove the needles prior to surgery, resulting in the more common case in which titanium is nto found in the tissue.
187 citations
172 citations
Patent•
10 Dec 1979
TL;DR: A process for polymerizing or copolymerizing olefins in the presence of a catalyst composed of a solid titanium catalyst component obtained by reacting (i) a titanium composition composed essentially of tetravalent titanium, magnesium, halogen and an electron donor or electron donor residue selected from the group consisting of organic acid esters, alkoxy groups, and aryloxy groups as mentioned in this paper.
Abstract: A process for polymerizing or copolymerizing olefins, which comprises polymerizing or copolymerizing olefins in the presence of a catalyst composed of (A) a solid titanium catalyst component obtained by reacting (i) a titanium composition composed essentially of tetravalent titanium, magnesium, halogen and an electron donor or electron donor residue selected from the group consisting of organic acid esters, alkoxy groups and aryloxy groups with (ii) an organic silicon compound having an Si--O--C bond in the molecule in the presence of (iii) an organoaluminum compound, or by first treating the titanium composition (i) with the organoaluminum compound (iii) and then reacting it with the organic silicon compound (ii), until the amount of the electron donor or electron donor residue in the titanium composition (i) decreases from that before the reaction, thus including a part of the silicon compound in the titanium composition, and; (B) an organoaluminum compound.
137 citations
TL;DR: In this article, a falling film generator was used to obtain spherical titanium dioxide particles with modal diameters ranging between 0.06 and 0.6 μm, which were then hydrolyzed in specially designed chambers kept at different temperatures.
131 citations
TL;DR: A beta titanium alloy was evaluated for use in orthodontic appliances and resulted in titanium springs with 1.8 times the extension of comparable stainless steel springs, and a 2.2 fold reduction in force per unit displacement.
Abstract: A beta titanium alloy was evaluated for use in orthodontic appliances. Standard mechanical tests and a specially designed spring test were used. Two particular thermo-mechanical treatments resulted in titanium springs with 1.8 times the extension of comparable stainless steel springs, and a 2.2 fold reduction in force per unit displacement.
111 citations
Patent•
11 Jun 1979TL;DR: The high pressure reaction cell has a special design which prevents the entrance of impurities into the sample as discussed by the authors, and is used to prevent the entry of impurity in the sample.
Abstract: Cubic boron nitride has been made from powdered hexagonal boron nitride by a process which comprises vacuum firing of the HBN and conversion by high pressure-high temperature processing at 55-80 kilobars and 1600° C. to the reconversion temperature. The high pressure reaction cell has a special design which prevents the entrance of impurities into the sample. This cell, referring to FIG. 2, comprises, for example, a carbon tube (8) enclosing concentric titanium sleeve (9). Within the cylinder defined by the tube and sleeve are: the HBN sample (4), carbon filler (3), shielding tantalum foil discs (2) and carbon end plugs (10). The vacuum firing is done at pressures of 10 -5 --10 -10 mm Hg, 1400°-1900° C., for 5 minutes--4 hours, and is believed to form a thin, free-boron coating on the HBN particles. The process works on both pyrolytic (turbostratic) and graphitic hexagonal boron nitride. Grinding grits formed by milling cubic boron nitride chunks recovered from the high pressure-high temperature process have resulted in higher grinding ratios than commercially available CBN.
97 citations
Patent•
25 Jul 1979
TL;DR: Cast and forged titanium alloys suited for use at temperatures over 600° C. are based on TiAl gamma phase structure and have about 1.5% or greater tensile ductility at temperatures of 260° C and below, respectively.
Abstract: Cast and forged titanium alloys suited for use at temperatures over 600° C. are based on TiAl gamma phase structure. Useful alloys have about 1.5% or greater tensile ductility at temperatures of 260° C. and below, thereby making them fabricable and suited for engineering applications. Disclosed are alloys having weight percent compositions of 31-36 aluminum, 0-4 vanadium, balance titanium (in atomic percent, about: 45-50Al, 0-3V, bal Ti). The inclusion of about 0.1 weight percent carbon improves creep rupture strength. To obtain high tensile strength, the alloys are forged at about 1025° C. and aged at about 900° C.; to obtain higher creep rupture strength and tensile ductility, a solution anneal at about 1150° C. is interposed before aging.
90 citations
TL;DR: Despite the apparent complexity of the linear oxidation of titanium or titanium nitride resulting from the formation of a layered structure of the rutile scale formed, the uniqueness of the mechanism is proven.
Abstract: Despite the apparent complexity of the linear oxidation of titanium or titanium nitride resulting from the formation of a layered structure of the rutile scale formed, the uniqueness of the mechanism is proven. The limiting step appeared to be the predominant short-circuit diffusion of oxygen (E∼ 44 kcal · mole−1) through a rutile lamella of variable thickness growing at the nitride-oxide boundary and fracturing periodically to form a detached porous layer through which molecular oxygen can penetrate. The pressure dependence of the diffusion process in the case of the nitride was associated with the outward migration of nitrogen, while the undulations of the kinetics under certain conditions were caused by the growth of a sintered, recrystallized outer zone of oxide. The periodic exfoliation of the oxide was related to its poor adherence to the substrate, certainly due to the presence at the nitride-oxide interface of a thin gray film probably composed of intermediate phases between TiNx (or Ti) and TiO2.
76 citations
TL;DR: In this paper, steady state, potential step and impedance measurements were used to investigate the influence of fluoride ions on the passive dissolution of Ti in 4.5 M H 2 SO 4 solution.
73 citations
69 citations
TL;DR: In this article, the authors discuss the approaches to reactive d.c. sputtering and a criterion for the conditions which allow both the sputtering of metal at the target and the oxidation of the growing film on the substrate.
TL;DR: Methods are described for the unequivocal identification of mineral deposits in lung tissues obtained during the autopsy of a titanium dioxide-exposed worker who died of an undifferentiated malignant tumor, lending support to the supposition that the rutile crystal modification of titanium dioxide is biologically inert.
Abstract: Methods are described for the unequivocal identification of mineral deposits in lung tissues obtained during the autopsy of a titanium dioxide-exposed worker who died of an undifferentiated malignant tumor. The methods included scanning and transmission electron microscopy, electron and X-ray diffractometry, and atomic absorption spectroscopy. The presence of considerable amounts of rutile was revealed. Despite this heavy loading, no lung tissue reaction was evident. Within the limits imposed by the period since the first exposure (6 years), this finding lends support to the supposition that the rutile crystal modification of titanium dioxide is biologically inert.
TL;DR: In this paper, the data on the wear behavior of 304 stainless steel, commercial grade titanium and commercial grade aluminium without and with different surface treatments, namely ion implantation of boron and nitrogen and overlay coatings of titanium carbide and nitride.
TL;DR: In this paper, the influence of process variables, such as evaporation rate, N 2 partial pressure and deposition temperature, on the phases present, their morphology and hardness, was studied using X-ray diffraction, scanning electron microscopy and transmission electron microscope.
TL;DR: Ion implantation is a technique for modifying surface-sensitive and life-limiting properties of metals including resistance to wear and fatigue as discussed by the authors, which is a process of accelerating ions to high velocities and directing them into the near-surface regions of materials (e.g. alloys) to produce a different material (alloy) in the near surface region.
TL;DR: In this paper, it was shown that the rate of chlorine evolution was independent of both the roughness factor and the oxide loading of these anodes, the discharge apparently occurring at the external surface of these microporous electrodes.
TL;DR: In this article, the extraction of titanium(IV), iron(III) and iron(II) by di-2-ethyl hexyl phosphoric acid in benzene has been studied as a function of contact time, the concentration of the extractant in the organic phase, the temperature, etc.
TL;DR: In this article, the conditions under which cathodically impressed or galvanically induced currents can cause hydriding of titanium were discussed, and the oxide film that normally covers the surface of the titanium was discussed.
Abstract: This paper discusses the conditions under which cathodically impressed or galvanically induced currents can cause hydriding of titanium. The oxide film that normally covers the surface of ...
TL;DR: In this article, a modified Hopkinson bar was used to compress specimens of commercially-pure titanium, IMI 125 and titanium alloys, AMS 4911B and AMS4916B, at natural strain rates of between 3 × 10 3 s −1 and 3× 10 4 s − 1, and the results for the 4916B alloy at higher strain rates were too scattered to give a definite trend.
TL;DR: In this article, the problem of pitting corrosion of M50 alloy steel bearings used in turbojet engines has been found to be a severe problem and ion implantation was applied to this problem because it was shown to be able to maintain both the dimensional stability and the contact fatigue lifetime of the M50 bearings.
Journal Article•
TL;DR: The performance of titanium and its alloys in surgical implant applications is examined with respect to the materials' biocompatibility and ability to withstand the corrosive fluids of the human body as discussed by the authors.
Abstract: The performance of titanium and its alloys in surgical implant applications is examined with respect to the materials' biocompatibility and ability to withstand the corrosive fluids of the human body. Both in-vitro and in-vivo experimentation is reviewed, as well as the reported clinical results. For comparative purposes, other commonly used implant alloys are discussed. Since the corrosion resistance of titanium and its alloys is due to a passive film which covers the metal, a portion of the paper is devoted to the nature of the passive film. Studies dealing with formation, compositions, and structures of titanium passive films, as well as environmental effects on these films are examined. In-vitro studies have been carried out in numerous physiological solutions using various electrochemical techniques. Among the parameters studied were pH, pO 2 , surface finish, surface treatments, crevice corrosion, galvanic coupling, stress, fatigue, and fretting corrosion. In every study titanium and its alloys compared favorably with the other materials tested. In-vivo studies as early as 1940 showed that titanium is as well tolerated biologically as is stainless steel and Vitallium. More recent animal studies confirmed the early conclusions, and, in fact, it appears that titanium and some of its alloys may be actually better tolerated than stainless steel and the cobalt-chromium alloys. Clinical findings have been consistent with the results of in-vitro and in-vivo studies; not a single corrosion-related failure of a titanium or titanium-alloy implant could be found in the clinical literature. In summary, the available information indicates that titanium and some of its alloys may be the most biocompatible and corrosion-resistant metallic implant materials in present use.
TL;DR: In this paper, the authors compared the precipitation behavior under neutron irradiation with behavior during 4 MeV Ni ion irradiation for AISI 316 stainless steel and a related stainless steel containing additions of titanium and silicon, and showed that the partitioning of elements into various phases during irradiation is not sufficient for the initiation of swelling in stainless steels modified with silicon and titanium.
TL;DR: In this paper, a backscattering technique was used to study the reaction of titanium thin films with silicon and with SiO 2 in the temperature range 500-600°C.
TL;DR: An X-ray diffraction study of μ-dinitrogenbis [p-tolyldicyclopentadienyltitanium(III)], [(C5H5)2Ti(p-CH3C6H4)]2N2, showed that the two titanium atoms in the molecule are linked by the dinitrogen ligand in an essentially linear manner as discussed by the authors.
Patent•
30 Apr 1979TL;DR: In this article, a process for patterning regions on a semiconductor structure comprises the steps of forming a first layer of an alloy of tungsten and titanium on the semiconductor, forming a conductive layer of aluminum or chemically similar material on the surface of the Tungsten-titanium alloy, removing the undesired portions of the conductive layers by etching with a plasma and removing the thereby exposed portion of the tengsten-to-itanium Alloy layer by chemical etching.
Abstract: A process for patterning regions on a semiconductor structure comprises the steps of forming a first layer of an alloy of tungsten and titanium on the semiconductor structure, forming a conductive layer of aluminum or chemically similar material on the surface of the tungsten-titanium alloy, removing the undesired portions of the conductive layer by etching with a plasma and removing the thereby exposed portions of the tungsten-titanium alloy layer by chemical etching.
TL;DR: In this paper, the authors studied the hydrolysis of titanium(IV) in 2.0 mol dm −3 aqueous (Na,H)Cl solution at 25 °C by means of e.m.f. measurements of a cell containing 0.019 3−0.048 2 mol −0.
Abstract: Hydrolysis of titanium(IV) has been studied in 2.0 mol dm–3 aqueous (Na,H)Cl solution at 25 °C by means of e.m.f. measurements of a cell containing 0.019 3–0.048 2 mol dm–3 titanium(IV). Titanium(IV), which is present in the form of titanyl ion, [TiO]2+, is partially hydrolyzed to form a polynuclear cationic complex, [(TiO)8(OH)12]4+(log β8,12=–1.68± 0.10).