Showing papers on "Titanium published in 2001"
TL;DR: Film and powders of TiO2-x Nx have revealed an improvement over titanium dioxide (TiO2) under visible light in optical absorption and photocatalytic activity such as photodegradations of methylene blue and gaseous acetaldehyde and hydrophilicity of the film surface.
Abstract: To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Films and powders of TiO 2- x N x have revealed an improvement over titanium dioxide (TiO 2 ) under visible light (wavelength 2 has proven to be indispensable for band-gap narrowing and photocatalytic activity, as assessed by first-principles calculations and x-ray photoemission spectroscopy.
11,402 citations
TL;DR: The observation of transparent ferromagnetism in cobalt-doped anatase thin films with the concentration of cobalt between 0 and 8% is reported, indicating the existence of ferromagnetic long-range ordering.
Abstract: Dilute magnetic semiconductors and wide gap oxide semiconductors are appealing materials for magnetooptical devices. From a combinatorial screening approach looking at the solid solubility of transition metals in titanium dioxides and of their magnetic properties, we report on the observation of transparent ferromagnetism in cobalt-doped anatase thin films with the concentration of cobalt between 0 and 8%. Magnetic microscopy images reveal a magnetic domain structure in the films, indicating the existence of ferromagnetic long-range ordering. The materials remain ferromagnetic above room temperature with a magnetic moment of 0.32 Bohr magnetons per cobalt atom. The film is conductive and exhibits a positive magnetoresistance of 60% at 2 kelvin.
2,302 citations
TL;DR: In this article, the average tube diameter, ranging in size from 25 to 65 nm, was found to increase with increasing anodizing voltage, while the length of the tube was found independent of anodization time.
Abstract: Titanium oxide nanotubes were fabricated by anodic oxidation of a pure titanium sheet in an aqueous solution containing 0.5 to 3.5 wt% hydrofluoric acid. These tubes are well aligned and organized into high-density uniform arrays. While the tops of the tubes are open, the bottoms of the tubes are closed, forming a barrier layer structure similar to that of porous alumina. The average tube diameter, ranging in size from 25 to 65 nm, was found to increase with increasing anodizing voltage, while the length of the tube was found independent of anodization time. A possible growth mechanism is presented.
1,975 citations
TL;DR: Results indicate that titanium, hafnium, niobium, tantalum and rhenium have good biocompatibility and osteoconductivity.
699 citations
TL;DR: In this paper, a review focusing on precipitation in creep resistant austenitic stainless steels, in particular wrought heat resistant grades containing niobium and titanium additions, is presented.
Abstract: Austenitic stainless steels have for some time been used as superheater tubes in the electricity generation industries in harsh environments with temperatures as high as 650°C at pressures of some 200 atm; they are expected to provide reliable service for 30 years or more. Their detailed mechanical properties are dependent on the stability of the microstructure, particularly the formation, dissolution, and coarsening of precipitates. Although the precipitation processes have been studied extensively, there remain important discrepancies. It is known that small changes in the chemical composition or thermomechanical processing can profoundly influence the evolution of the microstructure. This review focuses on precipitation in creep resistant austenitic stainless steels, in particular wrought heat resistant grades containing niobium and titanium additions. Conventional alloys such as 18–8 and 16–10 are included together with the new NF709 (20–25) and other recent variants. Precipitates forming in a...
583 citations
TL;DR: In this paper, the atomic structure of the synthesized tubular material is imaged by high-resolution transmission electron microscopy (HRTEM), and the composition of individual tubular structures is determined using selected area energy dispersive X-ray spectroscopy (EDX).
Abstract: Well crystallized nanoscale tubular materials have been synthesized via the reaction of TiO2 crystals of either anatase or rutile phase and NaOH aqueous solution. The atomic structure of the synthesized tubular material is imaged by high-resolution transmission electron microscopy (HRTEM), and the composition of individual tubular structures is determined using selected area energy dispersive X-ray spectroscopy (EDX). Our results show that the tubular materials are well crystallized tubes with an average diameter of about 9 nm and little dispersion, and are composed of mainly titanium and oxygen. The atomic ratio of O/Ti is found, however, to vary from tube to tube. Detailed electron and x-ray diffraction studies show that the structure of our titanium oxide nanotubes do not agree with those made of TiO2 crystals with either anatase or rutile phase. HRTEM observations revealed that the titanium oxide nanotubes usually have multiple shells, in analogy with multiwalled carbon nanotubes, but the shell spacin...
540 citations
TL;DR: It was demonstrated that the interference colours were useful to identify the thickness of titanium oxide and the anodic forming voltages with slope in acid electrolytes were higher than in alkaline electrolytes, and the effects of electrolyte concentration, electrolyte temperature, and agitation speed were explained on the basis of the model of the electrical double layer.
514 citations
TL;DR: In this article, a model for the determination of relative grain size is developed based on the assumption that nucleant substrates are activated by constitutional undercooling generated by growth of an adjacent grain.
460 citations
TL;DR: In this paper, the weldability of the non-weldable alloys by use of powder filler is explained for aerospace applications and an example of increased process stability during laser beam welding of aluminium is presented.
428 citations
TL;DR: Various methods of surface treatment including traditional treatments such as acid etch, anodisation, novel plasma spray and laser treatments for both polymer composites and titanium will be discussed.
327 citations
TL;DR: In this paper, a titanosilicate with MWW topology, Ti-MWW, has been prepared by an acid treatment on a corresponding lamellar precursor which is hydrothermally synthesized with the coexistence of boron and titanium using piperidine (PI) or hexamethyleneimine (HM) as a structure-directing agent.
Abstract: A novel titanosilicate with MWW topology, Ti-MWW, has been prepared by an acid treatment on a corresponding lamellar precursor which is hydrothermally synthesized with the coexistence of boron and titanium using piperidine (PI) or hexamethyleneimine (HM) as a structure-directing agent. The MWW precursor can be synthesized to have a Si/Ti ratio as low as 10 when the Si/B ratio of the gel is maintained at 0.75. Both the materials synthesized using PI and HM exhibit the crystal form of thin platelets, while the latter shows a larger crystal size. Besides the tetrahedral Ti species, the precursor always contains the octahedral Ti species showing a UV−vis band at 260 nm, regardless of the Ti content. Calcination of the precursor results in a partial condensation of the octahedral Ti species to form the anatase phase, which is hardly removed by the acid treatment. MWW-type titanosilicate nearly free of both anatase and boron, however, is successively prepared by a cyclic treatment on the lamellar precursor, tha...
TL;DR: In this article, the mechanical properties of commercially pure (CP) Ti at room temperature were investigated and the decreasing grain size in CP Ti leads to significant increases in its hardness and/or strength.
TL;DR: The initial formation of the amorphous calcium titanate is proposed to be a consequence of the electrostatic interaction of negatively charged units of titania, which are dissociated from the Ti-OH groups, with the positively charged calcium ions in the fluid.
Abstract: Bioactive titanium metal, which forms a bonelike apatite layer on its surface in the body and bonds to the bone through the apatite layer, can be prepared by NaOH and heat treatments to form an amorphous sodium titanate layer on the metal. In the present study, the mechanism of apatite formation on the bioactive titanium metal has been investigated in vitro. The metal surface was examined using transmission electron microscopy and energy dispersive X-ray spectrometry as a function of the soaking time in a simulated body fluid (SBF) and complemented with atomic emission spectroscopy analysis of the fluid. It was found that, immediately after immersion in the SBF, the metal exchanged Na(+) ions from the surface sodium titanate with H(3)O(+) ions in the fluid to form Ti-OH groups on its surface. The Ti-OH groups, immediately after they were formed, incorporated the calcium ions in the fluid to form an amorphous calcium titanate. After a long soaking time, the amorphous calcium titanate incorporated the phosphate ions in the fluid to form an amorphous calcium phosphate with a low Ca/P atomic ratio of 1.40. The amorphous calcium phosphate thereafter converted into bonelike crystalline apatite with a Ca/P ratio of 1.65, which is equal to the value of bone mineral. The initial formation of the amorphous calcium titanate is proposed to be a consequence of the electrostatic interaction of negatively charged units of titania, which are dissociated from the Ti-OH groups, with the positively charged calcium ions in the fluid. The amorphous calcium titanate is speculated to gain a positive charge and to interact with the negatively charged phosphate ions in the fluid to form the amorphous calcium phosphate, which eventually stabilizes into bonelike crystalline apatite.
TL;DR: In this article, polycrystalline aluminum nitride thin films were deposited onto platinum, aluminum, and titanium electrodes by reactive magnetron sputtering in the pulsed direct current mode.
Abstract: Polycrystalline aluminum nitride thin films were deposited onto platinum, aluminum, and titanium electrodes by reactive magnetron sputtering in the pulsed direct current mode. The films exhibited all a columnar microstructure and a c-axis texture. The built-in stress and the piezoelectric properties of these films were studied as a function of both the processing conditions and the electrode material. Stress was found to be very much dependent on the growth conditions, and values ranging from strong compression to high tension were observed. The piezoelectric d33,f coefficient was shown to rely on substrate quality and ionic bombardment: The nucleation surface must be stable with regard to the nitrogen plasma and present a hexagonal symmetry and, on the other hand, enough energy must be delivered to the growing film through ionic bombardment.
TL;DR: The findings indicate that surface modification by means of a dry process is useful in providing antibacterial activity of oral bacteria to titanium implants exposed to the oral cavity.
TL;DR: The discovery of a cotunnite-structured titanium oxide which represents the hardest oxide known is reported, which is one of the least compressible and hardest polycrystalline materials to be described.
Abstract: A material as hard as diamond or cubic boron nitride has yet to be identified1,2,3,4,5,6, but here we report the discovery of a cotunnite-structured titanium oxide which represents the hardest oxide known. This is a new polymorph of titanium dioxide, where titanium is nine-coordinated to oxygen in the cotunnite (PbCl2) structure. The phase is synthesized at pressures above 60 gigapascals (GPa) and temperatures above 1,000 K and is one of the least compressible and hardest polycrystalline materials to be described.
TL;DR: In this paper, an experimental study on drilling of graphite/bismaleimide (Gr/Bi) titanium (Ti) stacks was conducted by using different cutter materials with a standard geometry to understand and characterize the process.
TL;DR: Alkanephosphonic acids assemble from solution on the native oxide surface of titanium to form alkane chain ordered films which can resist removal by solvent washing or simple mechanical peel testing as mentioned in this paper.
Abstract: Alkanephosphonic acids assemble from solution on the native oxide surface of titanium to form alkane chain ordered films which, however, are easily removed by solvent rinse. In contrast, assembling the alkanephosphonic acid from solution on the native oxide surface of titanium followed by gentle heating gives an alkane chain ordered film of the acid which is strongly surface-bound; this film resists removal by solvent washing or simple mechanical peel testing. Surface imaging by atomic force microscopy shows comprehensive surface coverage by aggregated islands, with elevations of each consistent with monolayer formation. ω-Carboxyalkanephosphonic acids are also easily bound to the native oxide surface of Ti through self-assembly/heating. Infrared analysis is consistent with surface attachment through the phosphonate headgroup.
TL;DR: In this article, uncoated cemented carbide tools were used for the turning of Ti-6Al-2Sn-4Zr-6Mo, and the experiments were carried out under dry cutting condition.
01 Jan 2001
TL;DR: In this article, the composition, microstructure and physico-chemical properties of thin oxide films on titanium and titanium alloys are discussed, with a focus on thin layers in the sense of natural oxide films grown at ambient or higher temperatures.
Abstract: This chapter covers information on the composition, microstructure and physico-chemical properties of thin oxide films on titanium and titanium alloys. The focus is on thin layers in the sense of ‘natural’ oxide films grown at ambient or higher temperatures with emphasis on titanium oxide, with some selected additional information on oxides related to metals commonly used as alloying elements in titanium alloys for biomedical applications. This chapter does not, however, include thicker oxide films such as those produced by electrochemical or plasma techniques, which are covered in Chap. 8.
TL;DR: In this article, a mesoporous SBA-15 molecular sieve has been successfully prepared at 373 K by direct synthesis under microwave−hydrothermal conditions within about 2 h.
Abstract: Titanium-substituted mesoporous SBA-15 molecular sieve has been successfully prepared at 373 K by direct synthesis under microwave−hydrothermal conditions within about 2 h. By means of X-ray diffraction, nitrogen adsorption, infrared, UV−vis diffuse reflectance, and Raman spectroscopies, a successful isomorphous substitution of titanium in the silica framework of SBA-15 samples with Si/Ti ratios of 20, 30, and 40 has been reported. The substitution of Ti for Si did not change the textural properties. The higher titanium loading leads to the formation of extraframework titanium species. These results show that microwave-assisted synthesis is an ideal approach to prepare Ti-substituted SBA-15, which is expected to be useful as a selective oxidation catalyst for reactions involving large molecules.
TL;DR: In this article, the average crystallite size of the various phases, lattice cell parameters, phase concentrations, and titanium cationic defects in the crystalline structures of different samples were quantitatively determined.
Abstract: Iron-doped titania photocatalysts with different iron contents were prepared by using a sol−gel method in acidic media. The crystalline structures of the various phases calcined at temperatures ranging from 70 to 800 °C were studied by using the Rietveld technique in combination with XRD experiments. The average crystallite size of the phases, lattice cell parameters, phase concentrations, and titanium cationic defects in the crystalline structures of different samples were quantitatively determined. Both iron content and calcination temperature strongly affected phase transformation and solid-state reaction mechanism. Below 400 °C of calcination, all the samples had some brookite and a majority of anatase phase. Iron ions were uniformly distributed in the interstices of titania crystals to form a titanium−iron solid solution when the samples were calcined at 80, 200, and 400 °C. However, when the temperature was 800 °C, Fe2TiO5 was produced in the sample containing 5 wt % Fe by a reaction between interst...
TL;DR: Anodic oxidation and oxide films of titanium in the new electrolyte of calcium glycerophosphate (Ca-GP) and calcium acetate (CA) were investigated by galvanostatic mode, SEM, XRD and EPMA and displayed porosity, intermediate roughness, and high crystallinity.
Patent•
30 Mar 2001
TL;DR: In this article, a group III nitride compound semiconductor layer is formed on a substrate with a titanium layer and a titanium nitride layer is removed in the condition that a sufficient film thickness is given to the titanium layer.
Abstract: A titanium layer and a titanium nitride layer are successively laminated on a substrate and a group III nitride compound semiconductor layer is further formed thereon. When the titanium layer is removed in the condition that a sufficient film thickness is given to the titanium nitride layer, a device having the titanium nitride layer as a substrate is obtained.
TL;DR: In this article, anatase and rutile thick films generated from the same source of titania were found to exhibit different types of conductivity upon exposure to CO and CH 4 at 600°C in a background of 5% O 2 /95% N 2.
Abstract: Anatase and rutile thick films generated from the same source of titania were found to exhibit different types of conductivity upon exposure to CO and CH 4 at 600°C in a background of 5% O 2 /95% N 2 . Anatase behaved as a n-type semiconductor, with a decrease in resistance with reducing gas, whereas rutile exhibited p-type conductivity. The morphology of the particles were different, with anatase consisting of spherical particles of 100–200 nm dimensions, whereas rutile appeared as elongated rods of ∼1 μm lengths. The n-type behavior of anatase can be explained based on the oxygen vacancies. For explanation of the p-type behavior of rutile, impurities in the sample have to be taken into account. The impurity contents in both samples were similar, and doping of the lower valent impurities into the TiO 2 lattice should lead to creation of interstitial titanium defects. During anatase to rutile conversion at temperatures of 1000°C, the titanium interstitials can help incorporate excess oxygen, leading to formation of holes and p-type conductivity in the rutile phase. Resistance changes upon interaction of reducing gas with composites of anatase–rutile was also studied. It was found that samples with 4 followed a similar pattern. However, since the overall response of CH 4 was smaller than that of CO, the 75% rutile sample showed no change upon exposure to CH 4 , while exhibiting an n-type response to CO, indicative of a selective CO sensor at temperatures of 600°C. A polychromatic percolation model was developed to explain the electrical data. Two independent, parallel pathways involving the n-type anatase and p-type rutile were considered to be important in the conductivity. Using experimental data related to the extent of sintering, and appropriate particle sizes, the model predicted that n–n percolation would occur from 0 up to 94.5% rutile and p–p percolation would begin at 75.1% rutile. In between 75.1 and 94.5% rutile, both n- and p-pathways would percolate, resulting in the observed diminished changes in resistance.
TL;DR: In this paper, several catalysts were tested and it was established that their activity gradually decreases from TiCl4 to Fe in the series TiCl 4>Al3Ti≫Al22Fe3Ti8>Al 3Ti>Fe>Fe.
TL;DR: The research results suggest that PIRAC nitriding procedure could improve the in vivo performance of NiTi alloys implanted into the human body.
TL;DR: Physical modification of titanium implant surfaces such as coating with TiN or ZrN may reduce bacterial adherence and hence improve clinical results.
Abstract: Bacterial adhesion on titanium implant surfaces has a strong influence on healing and long-term outcome of dental implants. Parameters like surface roughness and chemical composition of the implant surface were found to have a significant impact on plaque formation. The purpose of this study was to evaluate the influence of two physical hard coatings on bacterial adhesion in comparison with control surfaces of equivalent roughness. Two members of the oral microflora, Streptococcus mutans and Streptococcus sanguis were used. Commercially pure titanium discs were modified using four different surface treatments: physical vapour deposition (PVD) with either titanium nitride (TiN) or zirconium nitride (ZrN), thermal oxidation and structuring with laser radiation. Polished titanium surfaces were used as controls. Surface topography was examined by SEM and estimation of surface roughness was done using a contact stylus profilometer. Contact angle measurements were carried out to calculate surface energy. Titanium discs were incubated in the respective bacterial cell suspension for one hour and single colonies formed by adhering bacteria were counted by fluorescence microscopy. Contact angle measurements showed no significant differences between the surface modifications. The surface roughness (Ra) of all surfaces examined was between 0.14 and 1.00 microm. A significant reduction of the number of adherent bacteria was observed on inherently stable titanium hard materials such as TiN and ZrN and thermically oxidated titanium surfaces compared to polished titanium. In conclusion, physical modification of titanium implant surfaces such as coating with TiN or ZrN may reduce bacterial adherence and hence improve clinical results.
TL;DR: The early and strong bonding to bone of alkali- and heat-treated titanium and its alloys without intervening fibrous tissue may be useful in establishing cementless stable fixation of orthopedic implants.
TL;DR: In situ toughened TiB 2 -TiC x composites were fabricated using reaction synthesis of B 4 C and Ti powders at high temperatures as discussed by the authors. The resulting materials possessed very high relative densities and well developed TiB2 plate-like grains, leading to a rather high fracture toughness, up to 12.2 MPa⋅m 1/2.