Showing papers on "Titanium published in 1993"

An IR and NMR study of the chemisorption of titanium tetrachloride on silica

Abstract: The atomic layer epitaxy (ALE) reactions, i.e., the saturating gas-solid reactions of TiCl 4 at 175 and 450 o C with silica preheated at 200-820 o C, were studied by nuclear magnetic resonance and Fourier transform infrared spectroscopy, while etching experiments with sulfuric acid were carried out to determine the amount of amorphous titanium species. At 175 o C TiCl 4 reacted directly with the OH groups of silica either monofunctionally or bifunctionally depending on the preheat temperature of silica

Infrared spectroscopic investigation of titanium in zeolites. A new assignment of the 960 cm–1 band

Abstract: The formation of Si–O–defect groups due to the incorporation of Ti in the framework of zeolites is evidenced by means of solid-state tetraethylammonium (TEA) cation exchange; a new assignment for the infrared (IR) band in both β-Ti and TS-1 is presented.

Surface hardened biocompatible metallic medical implants

Abstract: This invention provides surface hardened, abrasion resistant high strength, biocompatible metal medical implants, in particular, titanium alloy implants which do not include any elements which have been shown or suggested as having short term or long term potential adverse effect from a standpoint of biocompatibility. Further, the invention provides methods of strengthening and hardening the surfaces of other titanium, zirconium, and cobalt-based alloy implants with small concentrations of a metal solute such as zirconium, yttrium, tantalum, aluminum, silicon, chromium, or thorium via internal oxidation or nitridation. Alternatively, nitrogen, oxygen, or carbon can be diffused directly into the surface of the implants by interstitial hardening to further increase the surface abrasion resistance of these internally oxidized or internally nitridized implant metal or metal alloys.

Ultrasmall Metal Oxide Particles: Preparation, Photophysical Characterization, and Photocatalytic Properties

Abstract: This paper gives an overview of the author's activities in the research of extremely small metal oxide particles in recent years. In particular, the synthesis of transparent colloidal solutions of extremely small zinc oxide, titanium dioxide, hematite, and titanium/iron mixed oxide particles (2 nm < d 20 nm) in water, ethanol, and 2-propanol is described. Quantum (Q)-size effects are observed during particle growth and at me final stages of synthesis. A simple molecular orbital (MO) picture is presented for the qualitative interpretation of these effects, while quantitative calculations have been carried out using a quantum mechanical model developed by Brus. The photophysical properties of the particles have also been investigated extensively. Fluorescence spectra of the ZnO sols suggest that adsorbed electron relays are necessary to shuttle electrons from the conduction band to lower-lying traps. Excess negative charge on the particles, resulting from either deprotonated surface hydroxyl groups or from photogenerated or externally injected charge carriers, causes a blue-shift in the electronic absorption spectrum, which is explained by electrostatic and MO models. The zero point of charge (pHzpc) of the aqueous colloidal suspensions has been determined by several independent methods. While zinc oxide, titanium dioxide, and titanium/iron mixed oxide particles exhibit considerable photocatalytic activity (as illustrated for the reduction of molecular oxygen and the oxidation of various halogenated carboxyl acids), hematite particles are only found to oxidize S(IV) under bandgap illumination to a reasonable extent (ϕ < 0.3). A mechanism involving surface-bound molecules and free radical intermediates is presented to explain these differences in reactivity.

Metal Organic Resin Derived Barium Titanate: I, Formation of Barium Titanium Oxycarbonate Intermediate

Abstract: Crystallization of BaTiO[sub 3] from an X-ray amorphous, metal organic precursor was investigated by comparing samples heated in O[sub 2], air, argon, and CO[sub 2]. It is evident that an intermediate barium titanium oxycarbonate phase forms between 500 and 620C and that BaTiO[sub 3] forms directly by the endothermic decomposition of this phase between 635 and 700C. From thermodynamic calculations, thermal analysis, X-ray diffraction, and Raman spectroscopy, it is concluded that the intermediate oxycarbonate is a highly disordered, metastable, and weakly crystalline phase with a stoichiometry close to Ba[sub 2]Ti[sub 2]O[sub 5]Co[sub 3].

Process for forming copper interconnect structure

Abstract: A copper metallization structure and process for the formation of electrical interconnections fabricated with pure copper metal is provided. The metallization structure includes an interface layer (22) intermediate to a dielectric layer (12), and a copper interconnect (30). The interface layer (22) functions to adhere the copper interconnect (30) to a device substrate (10) and to prevent the diffusion of copper into underlying dielectric layers. The interconnect layer (22) is fabricated by depositing a first titanium layer (16) followed by the sequential deposition of a titanium nitride layer (18), and a second titanium layer (20). A copper layer (24) is deposited to overlie the second titanium layer (20) and an annealing step is carried out to form a copper-titanium intermetallic layer (26). The titanium nitride layer (18) functions as a diffusion barrier preventing the diffusion of copper into the underlying dielectric layer (12), and the copper titanium intermetallic layer (26) provides an adhesive material, which adheres the copper layer (24) to the device substrate ( 10). Following the formation of the intermetallic layer (26), the device surface is planarized to form a planar surface (28), and to form an inlaid copper interconnect (30).

Metal release from titanium fixtures during placement in the mandible: an experimental study.

Abstract: Titanium screw taps and titanium fixtures were investigated by SEM before and after experimental use. Peri-implant bone surfaces were examined immediately after surgery and 5 months after implantation by SEM using the SE mode, backscattered electron imaging, and EDX analysis to detect titanium contamination of the bone specimens. The Ti content of the livers, kidneys, and lungs of six Gottingen minipigs, which had received two screw implants each, was determined using flameless atomic absorption spectroscopy and compared to a control group with no implants. Results showed that Ti particles were abraded and deposited on the bone surface during the preparation of implant beds. Five months after placement, particles were no longer observed on the bone surface next to the implants. Determination of the Ti concentration of the inner organs showed that the lungs contained the highest amount of titanium. The Ti content of the kidneys and livers was much lower. All values differed significantly from those of the control group (P < .01).

In vitro evaluation of amorphous calcium phosphate and poorly crystallized hydroxyapatite coatings on titanium implants

Abstract: Studies of various apatite coatings on metal orthopaedic prostheses suggest that coating dissolution may promote enhanced bone bonding. Little is known concerning the effects of crystallinity and the underlying roughness on calcium phosphate (Ca/P) coating dissolution rate. To address these issues, the surface chemistry of amorphous Ca/P and poorly crystallized hydroxyapatite (HA) coatings on "smooth" and "rough" titanium (Ti) alloy (Ti-6A1-4V) implants was studied following immersion in Hank's physiologic solution at pH 7.2 and 5.2 for 0-, 4-, and 12-week periods. Changes in Calcium (Ca) ion concentrations in the solutions, coating chemistry, and surface morphology were studied by ion selective electrode, x-ray diffraction (XRD), and scanning electron microscopy (SEM) respectively. The amount of Ca dissolved from Ca/P-coated implants was strongly dependent on the chemistry of the coating and less dependent on pH or time of incubation. The effect of the underlying surface (smooth vs. rough) was not significant. The poorly crystallized HA coating underwent the most degradation, greatest crystallographic alteration, and greatest surface film formation. The amorphous coating was more stable in the saline environment, and may be more suitable in vivo if coating longevity is desired. These results suggest that this in vitro method is an effective way of determining differences in HA coating integrity.

Electrochemical Deoxidation of Titanium.

Abstract: Removal of oxygen in titanium using an electrochemical technique was examined at temperatures around 1223 K with the purpose of obtaining nearly oxygen-free titanium. Titanium and carbon electrodes, immersed in molten CaCl2, served as cathode and anode, respectively, with an external DC source. CaCl2 was employed to produce the deoxidant calcium and to facilitate the reaction by decreasing the activity of the by-product CaO. By applying about 3 V between the electrodes, the calcium potential in CaCl2 was increased at the titanium cathode surface and titanium samples of the cathode could be deoxidized by the electrolytically produced deoxidant calcium or by calcium of high activity in the CaCl2 flux. Resulting O2− species, mainly present as the deoxidation product CaO in the flux, reacted at the carbon anode to form CO (or CO2) gas which was removed from the system. Titanium wires containing 1400 mass ppm oxygen were deoxidized to less than 100 mass ppm, whereas the carbon concentration increased by about 50 mass ppm. In some cases, the oxygen concentration in titanium samples was lowered to a level less than 10 mass ppm that could be determined by conventional inert gas fusion analysis. The behavior of contaminants, such as carbon and nitrogen, is also discussed.

Architectural Material Using Metal Oxide Exhibiting Photocatalytic Activity

Abstract: A metal-oxide layer exhibiting a photocatalytic activity function is formed on the surface of an inorganic architectural material, such as external wall material, roofing material, internal wall material, flooring material, and ceiling material, including glass, tile, concrete, stone, metal, and the like, so as to provide the property of deodorizing a space coming in contact with the architectural material, and antimold, antisoiling properties, and ultraviolet-ray absorbency of the surface of the architectural material, as well as the long-term maintenance of these properties. Preferably, the metal-oxide layer is formed by fixing a metal-oxide thin film on the surface of the architectural material. Alternatively, the metal-oxide layer is formed as an architectural material in which the surface thereof and its vicinity are mainly formed of a metal mixture including a metal oxide, such as titanium oxide, and palladium for improving photocatalytic activity, or a metal mixture including a metal constituting the metal oxide, such as titanium, and a composite of a second metal, while its inner portion is substantially formed of a metal mixture including titanium or a composite of titanium and palladium, the surface and its vicinity as well as the inner portion being formed continuously. As a method of manufacturing the latter architectural material, a metal mixture, i.e., an alloy, of titanium and a metal for improving photocatalytic activity, such as palladium, is fabricated, and after the alloy is processed into a desired shape, the processed alloy is subjected to oxidation treatment.

Preparation of Barium Titanates from Oxalates

Abstract: The decomposition of mixed barium titanium oxalates was studied by means of various thermochemical as well as spectroscopic methods. Infrared (IR) spectra of the mixed oxalates indicate the existence of an octahedral complex with Ti chelated by oxalate groups. In general, the results of both IR and the thermochemical analyses suggest that the oxalates are first converted to unidentate carbonate, then to ionic carbonate, and finally to mixed oxides of perovskite structure. The decomposition processes were found to depend upon the atmosphere. In the presence of oxygen the stoichiometrically mixed oxalates decompose by forming TiO2 and BaCO3 as intermediates. Under vacuum, two routes of decomposition occur in parallel. In one route, TiO2 and BaCO3 are formed as intermediates; in the other, partially reduced TiOx(x < 2) is formed, which further reacts with BaCO3 to produce also BaTiO3, CO2 and CO.

Point defects in silicon carbide

Abstract: A review is given on recent progress made in a microscopic understanding of point defects in silicon carbide (SiC). Defect structures to be discussed include shallow nitrogen donors, group-III acceptors, the transition metal impurities vanadium and titanium and radiation induced defects, like the silicon vacancy in SiC.

Enantioselective hydrophosphonylation of aromatic aldehydes catalyzed by chiral titanium alkoxides

Abstract: The enantioselective hydrophosphonylation of aromatic aldehydes with silylphosphite ( 1 ) or diethyl phosphonate ( 5a ) assisted by chiral titanium alkoxides as catalyst is examined. Titanium alkoxide ( 7 ), derived from L -tratrate and Ti(O-iPr) 4 , was found to be an effective catalyst and induce modest enantioselectivity in the reaction.

Sol-gel processing of titanium-containing thin coatings

Abstract: Using tetrabutylorthotitanate as a precursor, titanate coatings with and without modifiers such as SnO2 and Fe2O3 have been successfully obtained. The hydrolysis and polycondensation mechanism is discussed in relation to the sol-gel transition. The gel-formation region was obtained as well as stable-layer formation and phase-separation regions in the Ti(OBun)4-C2H5OH-H2O system. Coatings deposited on glass substrates exhibited a strong tendency to aggregate and with increasing temperature to crystallize in anatase or rutile phases (500 and 1000 °C, respectively). Structural characteristics of the gel products were investigated by SEM, X-ray and electron diffraction measurements, as well as by small-angle X-ray scattering. It was established that after thermal treatment at 500 °C for 10 min, spherical aggregates were formed in the coatings, having an average radius of approximately 5.1 nm.

Effect of aluminium addition on the combustion reaction of titanium and carbon to form TiC

Abstract: Aluminium was incorporated into the reactant mixture with a molar ratio of Ti/C of 1.0 to study the effect of its addition on the combustion reaction between titanium and carbon to form TiC. Thermal analysis of the reactant mixture and component analysis of the reaction product suggest that the combustion reaction of the Ti-C-Al system proceeds in such a way that aluminium initially reacts with titanium to form titanium aluminide compounds of TiAl3, Ti2Al, and TiAl with heat evolution, and then the reaction between titanium and carbon and the decomposition of titanium aluminide to titanium and aluminium is subsequently followed. As the amount of aluminium incorporated was increased over the range of 0 to 40 wt%, the grain size of TiC decreased from approximately 15 μm to 0.4 μm. It was also observed that most of the aluminium in the TiC-Al composite was distributed on the surface of the spherical TiC grain.

Implant and method of making the same

Abstract: An implant comprises and implant base body, at least a surface of which is composed of titanium or titanium alloy, and an anodic oxidation film formed on the surface, the film containing Ca and P. The implant may further comprise a calcium phosphate compound such as hydroxyapatite precipitated on the anodic oxidation film. The implant may be prepared by subjecting the base body to anodic oxidation in an electrolyte containing Ca compound and P compound, thereby forming an anodic oxidation film containing Ca and P. In addition, the film may be subjected to a hydrothermal treatment, thereby forming a film of a calcium phosphate compound such as hydroxyapatite on the anodic oxide film.

Preparation of barium titanate films at 55 C by an electrochemical method

Abstract: Work by previous investigators has shown that BaTiO[sub 3] films can be synthesized from solution over temperature ranges from 80 C to greater than 200 C. In the present work, electrically insulating crystalline films of BaTiO[sub 3] have been electrochemically deposited on titanium substrates at temperatures as low as 55 C. Auger spectroscopic analyses with depth profiling indicate that a titanium oxide layer whose thickness is governed by current density acts as a precursor to BaTiO[sub 3]. Formation of BaTiO[sub 3] is found to be favored only in highly alkaline solutions. This is consistent with the phase stability reported for the Ba-Ti-CO[sub 2]-H[sub 2]O system at 25 C. Lower processing temperatures (55 C) favor the formation of thick, electrically resistive, and well-crystallized BaTiO[sub 3] films, apparently due to increased oxygen solubility in the electrolyte solution. Films produced at 100 C are much thinner and are electrically conductive due to fissures and pores in their microstructure. Initial studies on the effect of current density indicate the formation of thinner and porous films with thicker titanium oxide intermediate layers.

Structure and integrity of a plasma sprayed hydroxylapatite coating on titanium

Abstract: Plasma sprayed hydroxylapatite (HA) coatings on titanium substrates were analyzed for process-induced compositional and structural changes. The HA starting powder and the resulting HA coatings were characterized using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The integrity of the ceramic-to-substrate bond strength was also determined, by subjecting plasma sprayed HA coatings to shear/cantilever bond testing. The ceramic coatings retained the basic apatitic crystal structure of the starting powder; however, a considerable amount of amorphous material was created during the plasma spray process. FTIR and Raman spectroscopy revealed that the resulting coatings were partially dehydroxylated. Both XRD and FTIR spectroscopy results also suggested that amorphous material, as well as additional calcium phosphate phases such as alpha-tricalcium phosphate (TCP) not in the starting powder, were present in the HA coating. Average bond strengths of the HA coatings to Ti were determined to be 14.8 MPa +/- 3.5, with fracture occurring at the interface and within the coating itself.