Showing papers on "Titanium published in 2000"
TL;DR: An electrochemical method for the direct reduction of solid TiO2 is reported, in which the oxygen is ionized, dissolved in a molten salt and discharged at the anode, leaving pure titanium at the cathode.
Abstract: Many reactive metals are difficult to prepare in pure form without complicated and expensive procedures Although titanium has many desirable properties (it is light, strong and corrosion-resistant), its use has been restricted because of its high processing cost In the current pyrometallurgical process--the Kroll process--the titanium minerals rutile and ilmenite are carbochlorinated to remove oxygen, iron and other impurities, producing a TiCl4 vapour This is then reduced to titanium metal by magnesium metal; the by-product MgCl2 is removed by vacuum distillation The prediction that this process would be replaced by an electrochemical route has not been fulfilled; attempts involving the electro-deposition of titanium from ionic solutions have been hampered by difficulties in eliminating the redox cycling of multivalent titanium ions and in handling very reactive dendritic products Here we report an electrochemical method for the direct reduction of solid TiO2, in which the oxygen is ionized, dissolved in a molten salt and discharged at the anode, leaving pure titanium at the cathode The simplicity and rapidity of this process compared to conventional routes should result in reduced production costs and the approach should be applicable to a wide range of metal oxides
1,193 citations
TL;DR: In this article, a double layer HA-TiO 2 coating on titanium alloys with HA as the top layer and a dense TiO 2 film as the inner layer was used to improve implant biocompatibility and durability by applying a hybrid treatment of micro-arc discharge oxidation and electrophoretic deposition.
Abstract: Titanium alloys have been used with some success in several bioimplant applications. However, they can suffer certain disadvantages, such as poor osteoinductive properties and low corrosive-wear resistance. Attempts to overcome the first of these drawbacks have involved coating the metal with the bioceramic material hydroxyapatite (HA), a primary component of bone and a very good osteoinductor. Since TiO 2 coatings are also known to be effective as chemical barriers against the in-vivo release of metal ions from the implants, a double layer HA–TiO 2 coating on titanium alloys with HA as the top layer and a dense TiO 2 film as the inner layer should possess a very good combination of bioactivity, chemical stability and mechanical integrity. This paper describes efforts to improve implant biocompatibility and durability by applying a hybrid treatment of micro-arc discharge oxidation (MDO) and electrophoretic deposition. The most common structural titanium alloy (Ti-6Al-4V) was used as the substrate material. A phosphate salt solution and an HA powder aqueous suspension were used as the electrolyte for micro-arc oxidation and the solution for HA electrophoretic deposition, respectively. It is shown that a relatively thick and hard TiO 2 coating can be produced by anodic micro-arc oxidation of titanium, and an HA coating incorporated on top of the TiO 2 layer can simultaneously be formed using a combination of plasma electrolysis and electrophoresis, with the suspension held at high values of pH. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) have been used to investigate the microstructure and morphology of the coatings. The adhesive strength between the coating and substrate has been assessed using scratch adhesion testing. The corrosion resistance of the specimens was examined using potentiodynamic tests in a buffered physiological solution. The results indicate that a hybrid combination of micro-arc oxidation and electrophoretic deposition can provide a phase-pure HA top layer and anticorrosive TiO 2 interlayer, which should show good mechanical and biochemical stability in the corrosive environment of the human body.
403 citations
352 citations
TL;DR: In this paper, the authors examine more closely these strengthening processes in order to assess their potential for extending the service range of the titanium aluminides towards higher temperatures, with particular emphasis on processing routes acceptable for these materials.
339 citations
TL;DR: In this article, the authors evaluated different bipolar plate materials, and present long-term fuel cell data for Poco® graphite, titanium, 316 and 310 stainless steel, and found that the properties of the passive film on the surface of 316 and 304 stainless steel are markedly different.
Abstract: The interfacial ohmic losses between the bipolar plate and the MEA can significantly reduce the overall power output from a SPFC. For graphitic bipolar plate materials, these losses are insignificant relative to stainless steel, where the existence of a passive film on the surface greatly reduces electrical conductivity. In this paper we have evaluated different bipolar plate materials, and present long-term fuel cell data for Poco® graphite, titanium, 316 and 310 stainless steel. The properties of the passive film on the surface of 316 and 310 stainless steel are markedly different. Although both were adequately corrosion resistant in a fuel cell environment, 310 tended to produce higher fuel cell performance and like 316, no degradation was observed after 1400 h testing. Analysis of the passive film indicated that this increased performance was related to the decreased thickness of the oxide film.
328 citations
TL;DR: The passive film formed by electrochemical oxidation on TiAlV alloy in physiological solution was studied using X-ray photoelectron spectroscopy and EIS to characterise electronic properties of passive films over seven decades of frequency and a link between electronic, electrochemical and physiochemical properties was established.
314 citations
TL;DR: In this article, the introduction of titanium centers to cubic MCM-48 and SBA-15 mesoporous silica by hydrothermal and postsynthetic grafting techniques is described.
Abstract: We describe the introduction of titanium centers to cubic MCM-48 and SBA-15 mesoporous silica by hydrothermal and postsynthetic grafting techniques. MCM-48 was hydrothermally prepared with a gemini surfactant that favors the cubic phase and leads to a high degree of long-range pore ordering. This phase was chosen due to its high surface area (1100−1300 m2/g) and its three-dimensional, bicontinuous pore array. SBA-15, synthesized with a block copolymer template under acidic conditions, has a surface area from 600 to 900 m2/g and an average pore diameter of 69 A, compared to 24−27 A for MCM-48. Alkoxide precursors of titanium were used to prepare samples of Ti-MCM-48 and Ti-SBA-15. We have detailed the bulk and molecular structure of both the silica framework and the local bonding environment of the titanium ions within each matrix. X-ray powder diffraction and nitrogen adsorption shows the pore structure is maintained despite some shrinkage of the pore diameter at high Ti loadings by grafting methods. UV−v...
307 citations
Patent•
16 Feb 2000TL;DR: In this paper, a tungsten slurry was proposed for the chemical mechanical polishing of thin films used in integrated circuit manufacturing, which can be used in a chemical mechanical planarization process to polish back a blanket-depletioned Tungsten film to form plugs or vias.
Abstract: Novel slurries for the chemical mechanical polishing of thin films used in integrated circuit manufacturing. A tungsten slurry of the present invention comprises an oxidizing agent, such as potassium ferricyanide, an abrasive such as silica, and has a pH between two and four. The tungsten slurry of the present invention can be used in a chemical mechanical planarization process to polish back a blanket deposited tungsten film to form plugs or vias. The tungsten slurry can also be used to polish copper, tungsten silicide, and titanium nitride. A second slurry, which is a 9:1 dilution of the tungsten slurry is ideal for chemical mechanical polishing of titanium nitride films. A third slurry of the present invention comprises a fluoride salt, an abrasive such as silica and has a pH≦8. The third slurry can be used to polish titanium films.
291 citations
TL;DR: In this paper, a new space holder method uses carbamide (urea) and ammonium hydrogen carbonate to produce samples with porosities between 60 and 80 % depending on the shape and size distribution of the space holder, spherical and angular pores in the range of 0.1-2.5 mm were obtained.
Abstract: The production of highly porous parts from titanium, stainless steel, and nickel-based superalloys is of increasing interest in lightweight constructions. A new space-holder method uses carbamide (urea) and ammonium hydrogen carbonate to produce samples with porosities between 60 and 80 %. Depending on the shape and size distribution of the space holder, spherical and angular pores in the range of 0.1-2.5 mm were obtained.
251 citations
TL;DR: In this paper, thin films of titanium carbide and amorphous hydrogenated carbon at various compositions have been deposited by unbalanced reactive magnetron sputtering from a metallic titanium target in the presence of argon and acetylene.
Abstract: Thin films of titanium carbide and amorphous hydrogenated carbon at various compositions have been deposited by unbalanced reactive magnetron sputtering from a metallic titanium target in the presence of argon and acetylene. XRD probed the presence of nanocrystalline TiC and, at high titanium concentrations, of metallic titanium. The XPS examinations allowed one to determine the amount of TiC produced at any concentration of titanium. Raman spectroscopy proved the presence of a-C:H up to 38 at.% of titanium. The coatings have a pronounced hardness maximum of 35 GPa at a composition of approximately 80% TiC and 20% a-C:H. The hardness at 60% TiC and 40% a-C:H as well as that of 100% TiC does not exceed 18 GPa. The mean separation of the crystallites, whose diameter is approximately 4 nm, amounts to a few atomic distances. At the maximum hardness a coefficient of friction of 0.25–0.3 is obtained. The coatings thus provide, at the optimum composition, high hardness at low friction.
249 citations
TL;DR: In this article, a well-characterized polycrystalline titanium surface with oxygen and water molecules at 150-850 K was studied in UHV by X-ray photoelectron spectroscopy (XPS), TDS, and Fourier transform reflectance-absorption infrared (FT-RAIRS).
TL;DR: In this paper, a highly efficient synthesis of esomeprazole via asymmetric oxidation of prochiral sulphide 1 is described, which is achieved by titanium-mediated oxidation with cumene hydroperoxide (CHP) in the presence of (S, S )-diethyl tartrate [(S, S)-DET].
Abstract: A highly efficient synthesis of esomeprazole—the ( S )-enantiomer of omeprazole—via asymmetric oxidation of prochiral sulphide 1 is described. The asymmetric oxidation was achieved by titanium-mediated oxidation with cumene hydroperoxide (CHP) in the presence of ( S , S )-diethyl tartrate [( S , S )-DET]. The enantioselectivity was provided by preparing the titanium complex in the presence of 1 at an elevated temperature and/or during a prolonged preparation time and by performing the oxidation of 1 in the presence of an amine. An enantioselectivity of >94% ee was obtained using this method.
TL;DR: A high pressure phase of titanium dioxide with an alpha-PbO(2)-type structure has been identified in garnet of diamondiferous quartzofeldspathic rocks from the Saxonian Erzgebirge, Germany as discussed by the authors.
Abstract: A high-pressure phase of titanium dioxide (TiO(2)) with an alpha-PbO(2)-type structure has been identified in garnet of diamondiferous quartzofeldspathic rocks from the Saxonian Erzgebirge, Germany. Analytical electron microscopy indicates that this alpha-PbO(2)-type TiO(2) occurred as an epitaxial nanometer-thick slab between twinned rutile bicrystals. Given a V-shaped curve for the equilibrium phase boundary of alpha-PbO(2)-type TiO(2) to rutile, the stabilization pressure of alpha-PbO(2)-type TiO(2) should be 4 to 5 gigapascals at 900 degrees to 1000 degrees C. This suggests a burial of continental crustal rocks to depths of at least 130 kilometers. The alpha-PbO(2)-type TiO(2) may be a useful pressure and temperature indicator in the diamond stability field.
TL;DR: The properties and clinical performance of c.p. titanium are discussed and compared to those of implant stainless steel and titanium alloys, and issues are addressed which arise from frequent inquiries from clinics.
Abstract: Commercially pure (cp) titanium has proven its suitability as an implant material in bone surgery over many years in the fields of osteosynthesis, oral implantology, and in certain applications in joint prosthetics Excellent biocompatibility and corrosion resistance are outstanding features Furthermore, cp titanium is known for not causing allergic reactions The different grades of cp titanium and their minimum mechanical properties are specified in ISO and ASTM standards for implant materials Typical mechanical properties are given for AO ASIF implant applications The properties and clinical performance of cp titanium are discussed and compared to those of implant stainless steel and titanium alloys In brief some specific features relating to cp titanium implant material are treated, including biocompatibility and soft tissue and bone response and taking into account the effects of implant surface configurations at the same time In addition, issues are addressed which arise from frequent inquiries from clinics
TL;DR: A brief survey of precursors used for the chemical vapour deposition of the dioxides of titanium, zirconium and hafnium is presented in this article.
Abstract: A brief survey of the precursors used for the chemical vapour deposition of the dioxides of titanium, zirconium and hafnium is presented. The review covers precursors used for the closely related process known as atomic layer chemical vapour deposition (ALCVD or ALD). Precursors delivered by standard carrier gas transport and by direct liquid injection (DLI) methods are included. The complexes fall into four classes based upon the ligands: halides, alkoxides, acetylacetonates (acac) and nitrates. Compounds bearing a mixture of ligand types have also found application in this area. The impact of the ligand on the microstructure of the metal oxide film is greatest at lower temperatures where the deposition rate is limited by the surface reactivity. The first use of anhydrous hafnium nitrate, Hf(NO3)4, to deposit films of hafnium oxide on silicon is reported. The films are characterized by Rutherford backscattering and X-ray photoelectron spectroscopy, X-ray diffraction and transmission electron microscopy. Copyright © 2000 John Wiley & Sons, Ltd.
TL;DR: In this article, the response of steadystate photoconductivity to changes in oxygen partial pressure (10{sup {minus}3} to 1 atm) has been quantitatively studied in thin-film polycrystalline TiO{sub 2}:Nb and ZnO at 80--120 C.
Abstract: Response of steady-state photoconductivity to changes in oxygen partial pressure (10{sup {minus}3} to 1 atm) has been quantitatively studied in thin-film polycrystalline TiO{sub 2}:Nb and ZnO at 80--120 C. The magnitude of photoconductivity varied as a square root of illumination intensity regardless of oxygen pressure. Both materials showed fast response to oxygen, although in different pressure ranges. Zinc oxide was more sensitive to lower oxygen pressures while titanium dioxide worked better at pressures close to 1 atm.
TL;DR: Titanium dioxide is a common food additive of increasing interest in dietary intake studies and dietary exclusion studies and a method was developed for its rapid determination in foods using acid digestion and inductively coupled plasma optical emission spectrometry (ICPOES).
Abstract: Titanium dioxide is a common food additive of increasing interest in dietary intake studies and dietary exclusion studies. Food labelling for titanium dioxide is imprecise so a method was developed for its rapid determination in foods using acid digestion and inductively coupled plasma optical emission spectrometry (ICPOES). Twenty-five foods thought to contain titanium dioxide were obtained. Based on preliminary digestion studies, samples (500 mg) were digested in 18 mol l-1 H2SO4 at 250 degrees C for 1 h and then diluted to 5.9 mol l-1 H2SO4 before determination of titanium by ICPOES at 336.121 nm. Emission intensity was suppressed by H2SO4 so standards were matched for acid concentration. Titanium dioxide embedded in gelatine was used to assess accuracy. A standard reference material of known titanium concentration and six foods of known titanium dioxide content were used as external reference materials. Limits of detection were 2-7.5 ppb, depending on spectral integration times, and the signal was linear up to 5 ppm. Results for all control samples were in good agreement with the expected values. Twelve of the foods contained detectable titanium, ranging from 0.001 to 0.782% by weight, but only eight indicated this on their labels, four being exempt under food labelling regulations. Based on food portion sizes, an individual's daily intake of titanium dioxide could exceed 200 mg from just one of these products. This method may facilitate future studies on titanium dioxide intake, given the present limitations of food labelling.
01 Jan 2000
TL;DR: In this paper, in situ reflection high-energy electron diffraction (RHEED) was used for the stoichiometric deposition of SrTiO3 (1 0 0) from independent strontium and titanium sources.
Abstract: The growth of high quality multicomponent oxide thin films by reactive molecular beam epitaxy (MBE) requires precise composition control. We report the use of in situ reflection high-energy electron diffraction (RHEED) for the stoichiometric deposition of SrTiO3 (1 0 0) from independent strontium and titanium sources. By monitoring changes in the RHEED intensity oscillations as monolayer doses of strontium and titanium are sequentially deposited, the Sr:Ti ratio can be adjusted to within 1% of stoichiometry. Furthermore, the presence of a beat frequency in the intensity oscillation envelope allows the adjustment of the strontium and titanium fluxes so that a full monolayer of coverage is obtained with each shuttered dose of strontium or titanium. RHEED oscillations have also been employed to determine the doping concentration in barium- and lanthanum-doped SrTiO3 films.
TL;DR: The optimal surface structure with the least contamination was found for the laser-treated titanium surface and an optimal structure was also achieved by the titanium plasma spray method, however, at the cost of surface purity.
TL;DR: In this paper, the (101) and (001) surfaces of anatase TiO2 were studied for the first time by secondary-electron imaging and low-energy electron diffraction.
31 Mar 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a new oxygen boost diffusion technique has been developed for deep case hardening of titanium and its alloys, which essentially consists of thermal oxidation in air followed by diffusion in vacuum.
Abstract: In order to withstand the high stresses encountered in such general engineering components as bearings and gears, deep case hardening is necessary. In the present investigation, oxygen boost diffusion of titanium alloys has been explored and a new oxygen boost diffusion technique has been developed for deep case hardening of titanium and its alloys. The oxygen boost diffusion process essentially consists of thermal oxidation in air followed by diffusion in vacuum. A total hardened case of about 300 μm can be successfully achieved following the oxygen boost diffusion treatment. It has also showed that the oxygen boost diffusion treated titanium alloys exhibited significantly improved abrasive wear resistance. Based on the experimental results, the boost diffusion and hardening mechanisms are discussed.
TL;DR: In this article, a mesoporous TS-1 catalyst was shown to be active in epoxidation of oct-1-ene and significantly more active in cyclohexene than conventional TS1.
TL;DR: The primary objective of this study was to investigate the conformation of human plasma fibrinogen (HPF) adsorbed on titanium oxide surfaces and a method for preparing ultraflat titanium substrates was developed.
Abstract: Conformational changes of proteins adsorbing on biomaterial surfaces affect biocompatibility. Titanium is among the most successful biomaterials; however, the mechanisms leading to its biocompatibility are not yet understood. The primary objective of this study was to investigate the conformation of human plasma fibrinogen (HPF) adsorbed on titanium oxide surfaces. A method for preparing ultraflat titanium substrates was developed. This allowed high-resolution investigation of both the titanium oxide surfaces and the adsorbed state of HPF. The titanium oxide surfaces were first imaged with an atomic force microscope in air and subsequently incubated in a solution of HPF in phosphate buffer and imaged in fluid with tapping mode AFM. The titanium oxide surfaces exhibited a root-mean-squared (RMS) roughness of (0.29 ± 0.03) nm over (1.00 × 1.00) μm2 areas. Different degrees of molecular order were found on the titanium oxide surface. In crystalline surface areas square lattices with parameters a0 = b0 ≈ 0.5 ...
TL;DR: In this article, the microstructure and compressive mechanical properties of the in-situ titanium matrix composites are examined using four reactive systems, namely Ti-B, Ti-TiB{sub 2}, Ti-Bi{sub 4}C and Ti-BN, and the objective of this work is to assess which system can produce in-Situ titanium composites with a higher mechanical strength.
TL;DR: Elimination of peroxide radicals from the titania gel and formation of anatase upon subsequent heating are considered to be responsible for the enhanced ability of apatite deposition.
Abstract: Commercially pure titanium was treated with a H2 O2/3mM TaCl5 solution at 80°C for various periods and a titania gel layer was formed on the surface. This gel remained amorphous when heating for 1 h below 200°C and transformed to anatase after heating between 300° and 600°C. The anatase titania gel layers were found to be bioactive as to deposit carbonate ion-incorporated apatite within 1 day of immersion in the Kokubo solution, whereas the amorphous layers did not deposit apatite within 7 days. The apatite particles were found to nucleate preferentially inside the cracks prevailing in the thicker gel layers of 1-h chemically treated specimens. After immersing for 2 days, the titanium specimens were almost completely covered by apatite. Elimination of peroxide radicals from the titania gel and formation of anatase upon subsequent heating are considered to be responsible for the enhanced ability of apatite deposition. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 52, 171–176, 2000.
TL;DR: In this article, X-ray diffraction, transmission electron microscopy and Raman spectroscopy revealed that microcrystalline brookite-type titanium(IV) oxide (TiO2) having an average size of 14 × 67nm was formed and that this brookites sample was not contaminated with other TiO2 phases such as anatase and rutile.
Abstract: Thermal treatment of oxobis(2,4-pentanedionato-O,O′)titanium (TiO(acac)2) in ethylene glycol (EG) in the presence of sodium laurate and a small amount of water at 300 °C was examined. X-Ray diffraction, transmission electron microscopy and Raman spectroscopy revealed that microcrystalline brookite-type titanium(IV) oxide (TiO2) having an average size of 14 × 67 nm was formed and that this brookite sample was not contaminated with other TiO2 phases such as anatase and rutile. Sodium salts, water and TiO(acac)2 as the titanium source were indispensable for the formation of brookite crystals and the use of EG as the reaction medium was essential to avoid contamination by other phases. This brookite TiO2 began to directly transform to the rutile phase on calcination at around 700 °C and completely converted at 900 °C.
TL;DR: It was concluded that the diode laser (980 nm) does not damage titanium surfaces, which should be of value when uncovering submerged implants and treating peri-implantitis.
Abstract: Background: Dental lasers have been recommended for uncovering submerged implants as well as decontaminating implant surfaces when treating peri-implantitis. The aim of this study was to show the possible alterations in titanium disc surfaces using an Nd:YAG or a diode laser. Methods: Three different titanium discs were used (sandblasted, titanium plasma-sprayed [TPS], and hydroxyapatite [HA] coated) to determine the effects of laser irradiation on these surfaces using a scanning electron microscope (SEM). The discs were either irradiated with a pulsed Nd:YAG laser with a contact handpiece and power settings of 2.0, 4.0, and 6.0W or with a diode laser at 5.0, 10.0, and 15.0W power settings and continuous wave (cw) in the contact handpiece. Irradiated areas were compared with control titanium sites which were not lased. The specimens were prepared for SEM examination after the disc irradiation. Results: The SEM examination demonstrated extensive melting in all of the Nd:YAG laser irradiated areas. Damage w...
TL;DR: A bioactive macroporous layer on an implant is expected not only to enhance bony ingrowth into the porous structure, but also to provide a chemical integration with bone via apatite formation on its surface in the body.
Abstract: A macroporous titanium surface layer is often formed on titanium and titanium alloy implants for morphological fixation of the implants to bone via bony ingrowth into the porous structure. The surface of titanium metal was recently shown to become highly bioactive by being subjected to 5.0 M-NaOH treatment at 60°C for 24 h and subsequent heat treatment at 600°C for 1 h. In the present study, the NaOH and heat treatments were applied to a macroporous titanium surface layer formed on titanium substrate by a plasma spraying method. The NaOH and heat treatments produced an uniform amorphous sodium titanate layer on the surface of the porous titanium. The sodium titanate induced a bonelike apatite formation in simulated body fluid at an early soaking period, whereby the apatite layer grew uniformly along the surface and cross-sectional macrotextures of the porous titanium. This indicates that the NaOH and heat treatments lead to a bioactive macroporous titanium surface layer on titanium substrate. Such a bioactive macroporous layer on an implant is expected not only to enhance bony ingrowth into the porous structure, but also to provide a chemical integration with bone via apatite formation on its surface in the body. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 52, 553–557, 2000.
Patent•
07 Jul 2000TL;DR: The quaternary nickel-zirconium-titanium-phosphorus alloy compositions have a superior amorphous phase-forming ability to produce the bulk amorphized alloy having a thickness of 1 mm by general casting methods as mentioned in this paper.
Abstract: Disclosed are nickel-based amorphous alloy compositions, and particularly quaternary nickel-based amorphous alloy compositions containing nickel, zirconium and titanium as main constituent elements and additive Si or P, the quaternary nickel-zirconium-titanium-silicon alloy compositions comprising nickel in the range of 45 to 63 atomic %, zirconium plus titanium in the range of 32 to 48 atomic % and silicon in the range of 1 to 11 atomic %, and being represented by the general formula: Ni a (Zr 1−x Ti x ) b Si c . Also, at least one kind of element selected from the group consisting of V, Cr, Mn, Cu, Co, W, Sn, Mo, Y, C, B, P, Al can be added to the alloy compositions in the range of content of 2 to 15 atomic %. The quaternary nickel-zirconium-titanium-phosphorus alloy compositions comprising nickel in the range of 50 to 62 atomic %, zirconium plus titanium in the range of 33 to 46 atomic % and phosphorus in the range of 3 to 8 atomic %, and being represented by the general formula: Ni d (Zr 1−y Ti y ) e P f . The nickel-based amorphous alloy compositions have a superior amorphous phase-forming ability to produce the bulk amorphous alloy having a thickness of 1 mm by general casting methods.