Narrow Results

The material composition and surface structure of dental and orthopaedic implants have important effects on integration of the implants with the surrounding bone, and at the same time, the release of the constituent elements of the implants into the surrounding tissues. It is the aim of this paper to study the degree of release of Ti in relation to the surface roughness of the implants. For this purpose, screw shaped implants were prepared with two different surface topographies; one group was left as-machined, i.e. as machine-turned surface, and the second group was blasted with 25 µm Al₂O₃ particles. The surface topography was measured with a confocal laser scanning profilometer and the surface roughness was characterized using height and spatial descriptive parameters. The as-machined surfaces had an average surface roughness (S_a) of 0.96 µm and the blasted surfaces had an S_a value of 1.16 µm. The implants were inserted into rabbit bone for 1 year. Six samples (three of each type) were prepared for PIXE analysis. The PIXE analysis was done using proton beams from a tandem type accelerator. with an energy of 2 MeV. The results show that at distances of about 2 mm from implant surface, titanium release into hard tissues was found at similar amounts for the as-machined and the blasted implants inserted in the tibia.

A thin passive titanium dioxide, in its stoichiometric form, has a very high corrosion resistance, but the same conclusion can not be made on corrosion resistance of a surface which is not stoichiometrically titanium dioxide, or even a surface which is a composition of various elements and oxides. In practice, the implants available on the market have an oxide surface contaminated with other elements. The aim of this paper is to correlate clinical observations that show the deterioration of Ti made implants after certain period of insertion in the patients, and in vitro corrosion resistance of Ti implants with surface passive oxide layer. For this purpose, surface analysis of the retrieved failed implants were performed and in vivo animal experiments with relation to ion release from implants were done. Finally, on the basis of the clinical observation, in vivo animal test, and in vitro electrochemical corrosion test, a model is proposed to explain the corrosion and ion release from the Ti implant.

High-orderly nanotubes of titania were fabricated by anodic oxidation of pure titanium substrate in different electrolytes containing fluoride. Different morphological nanotubes of titania were obtained through controlling the different pH value of inorganic electrolytes, and it was found that nanotubes of titanium oxide would not formed when pH value was above 6. The morphological and structural properties of nanotublar products were characterized by SEM. The synthesized nanotubes of titania in organic electrolytic solutions containing fluoride was of 60 μm in length. The experiments demonstrated the length and orderliness of nanotubes of titanium oxide in organic solutions were much better than those in inorganic solutions.

Microscopic hardness on free surface of polycrystalline metal during plastic deformation is closely related to the inhomogeneous deformation in respective grains. Uniaxial tensile tests were carried out on annealed pure aluminum sheet specimens with different averaged grain size and also on annealed pure titanium sheet specimen. The microscopic hardness was measured with the Vickers type micro-hardness testing machine. The increase in micro-hardness is larger at the grain boundary area than the central area of grains. The increase in the hardness is dependent on the averaged grain size of polycrystalline metals. The experimental results are discussed in relation to Hall-Petch relation concerning the grain size dependence of the yield stress or the flow stress.

The electronic band structure, density of states, structural phase transition, superconducting transition and Fermi surface cross section of titanium (Ti) under normal and high pressures are reported. The high pressure band structure exhibits significant deviations from the normal pressure band structure due to s → d transition. On the basis of band structure and total energy results obtained using tight-binding linear muffin-tin orbital method (TB LMTO), we predict a phase transformation sequence of α(hcp) → ω (hexagonal) → γ(distorted hcp) → β(bcc) in titanium under pressure. From our analysis, we predict a δ (distorted bcc) phase which is not stable at any high pressures. At ambient pressure, the superconducting transition occurs at 0.354 K. When the pressure is increased, it is predicted that, T_c increases at a rate of 3.123 K/Mbar in hcp–Ti. On further increase of pressure, T_c begins to decrease at a rate of 1.464 K/Mbar. The highest value of T_c(P) estimated is 5.043 K for hcp–Ti, 4.538 K for ω–Ti and 4.85 K for bcc–Ti. From this, it is inferred that the maximum value of T_c(P) is rather insensitive to the crystal structure of Ti. The nonlinearities in T_c(P) is explained by considering the destruction and creation of new parts of Fermi surface at high pressure. At normal pressure, the hardness of Ti is in the following order: ω-Ti > hcp-Ti > bcc-Ti > γ-Ti.

Alloys in the dilute Ti-Al-Mn system, which are considered to be near-α alloys, possess an attractive combination of strength and ductility, with the room temperature properties being intermediate between CP Ti and Ti-6Al-4V. Low levels of Fe are often tolerated in such alloys, but rarely introduced as deliberate alloying additions (with the exception of CP Ti grades), and from a processing perspective, it may indeed be desirable to have higher tolerances for Fe as it is often a common contaminant which must be controlled. In this presentation, the effect of 0.3wt.%Fe on the microstructure and behavior of a Ti-0.75wt.%Al-0.75wt.%Mn is reported. It was found that annealing in the (α+β) phase field can lead to an increase in the ductility of the alloy without having a detrimental effect on the tensile strength.

The objective of this work was to study the influence of titanium variations on the API 5L-X70 steel weld metal properties. The relationship between microstructure and toughness of the weld deposit was studied by means of full metallographic, longitudinal tensile and Charpy-V notch tests on the specimens cut transversely to the weld beads. The best combination of microstructure and impact properties was obtained in the range of 0.02-0.05% titanium. By further increasing of titanium content, the microstructure was changed from a mixture of acicular ferrite, grain-boundary ferrite, Widmanstätten ferrite to a mixture of acicular ferrite, grain-boundary ferrite, bainite and ferrite with M/A microconstituent. Therefore, the mode of fracture also changed from dimpled ductile to quasi-cleavage. Titanium-base inclusions improve impact toughness by increasing the formation of acicular ferrite in the microstructure. The amount of manganese in inclusions was decreased with addition of titanium to the weld metal.

In contrast to their exceptional mechanical properties, titanium and its alloys possess poor friction and wear characteristics. Nanocrystalline diamond (NCD) films appear to be a promising solution for their tribological problem due to their smooth surfaces and small grain size. However, the synthesis of a well adherent NCD film on titanium and its alloys is always complicated due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density. In this work NCD thin films have been deposited on pure Ti substrates in a microwave plasma chemical vapor deposition (MWPCVD) reactor under fixed pressure and methane concentration in hydrogen but over a wide temperature range. The effects of depositing temperatures on the adhesion of films are evaluated using Rockwell indentation tests. It is found that by increasing the deposition temperature the films bonding deteriorates. The films synthesized are characterized by field emission scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and X-ray diffraction.

With a first-principles method based on density functional theory, the effect of the alloying element titanium (Ti) on the thermodynamic stability and electronic structure of hydrogen (H) in pure vanadium (V) is investigated. The interactions between H and the vacancy and the defect solution energies in a dilute V–Ti binary alloy are calculated. The results show that: (i) a single H atom prefers to reside in a tetrahedral interstitial site in dilute V–Ti binary alloy systems; (ii) H atoms tend to bond at the vacancy sites; a mono-vacancy is shown to be capable of trapping three H atoms; and (iii) the presence of Ti in pure V can increase the H trapping energy and reduce the H trapping capability of the vacancy defects. This indicates that doping with Ti to form dilute V–Ti binary alloys can inhibit the solution for H, and thus suppress the retention of H. These results provide useful insight into V-based alloys as a candidate structural material in fusion reactors.

For film deposition, the substrate sheath properties, such as the plasma density, ion-to-atom ratios around the substrate, are more important for the film structure. In this paper, titanium thin films were deposited on grounded substrates by high-power pulsed magnetron sputtering (HPPMS) with the peak current in the range of 113–185 A. A simple and new equivalent circuit model of the sheath was established to study the plasma density around the substrate sheath. The Ti ion-to-atom ratios near substrate were studied by optical emission spectroscopy (OES), and the film structure was detected by transmission electron microscopy (TEM). The results showed that the calculated plasma density was from 0.8 × 10${}^{17}$ to 1.4 × 10${}^{17}$ m${}^{-3}$ at different peak current. These were consistent with the results measured by a modified one-grid ion collector using saturation current probe method, which proved our proposed equivalent circuit model was correct. The Ti ion-to-atom ratios around the substrate were estimated at about 24%–62%. The plasma density and ion to atom ratio around the substrate increased with the peak current, and this could lead to a higher film crystallization and preference growth on Ti (101) and (100).

Titanium (Ti) thin films with (002) or (100) texture are favored for many applications. In this paper, Ti thin films were prepared by high-power pulsed magnetron sputtering, and the texture of Ti thin films was successfully tailored by adjusting the pulse width, substrate bias and magnetic field strength. It is found that the peak power and average power of the Ti target are increased by increasing sputtering pulse width and decreasing magnetic field strength, which raise the Ti plasma flux and ion/atom ratio of Ti ions in front of the substrate simultaneously. Ti thin films with a highly (002) out-of-plane texture can be obtained with higher pulse width and lower magnetic field strength. The Ti thin films with highly (100) out-of-plane texture can be achieved with shorter pulse width, lower magnetic field strength and substrate bias.

Boron nitride (BN) and Titanium nitrides (TiNs) have been successfully researched recently. In order to analyze the relationship among the Boron, Nitrogen and Titanium, the ternary compounds with an orthorhombic structure Immm- are studied. We further researched on the mechanical, electronic and optical properties of new Immm-B${}_x$Ti${}_{3-x}$N₂ ($x=1,2$). The structures of BTi₂N₂ and B₂TiN₂ are mechanically stable at 0, 50 and 100 GPa. The BTi₂N₂ has the higher cutting resistance and better ductility than the B₂TiN₂. The higher Young’s modulus of B₂TiN₂ indicates the B₂TiN₂ is stiffer than BTi₂N₂. The BTi₂N₂ is harder to compress in the $Y$ direction and the B₂TiN₂ is harder in $Z$ direction. Immm-BTi₂N₂ and B₂TiN₂ have good metallicity at 0 and 100 GPa. Immm-BTi₂N₂ has the higher dielectric function than B₂TiN₂ and the plasma frequency of B₂TiN₂ is bigger than that of BTi₂N₂. We hope our work will provide some help to the experimental work about the technology of the material.

In this paper, selective laser sintering (SLS) was applied to join two materials by printing Ti–6Al–4V powder on a Ti substrate without any support parts. The characteristics of the interface between the as-built Ti–6Al–4V sample and the substrate were investigated. The analysis indicates that a heat-affected zone (HAZ) and the fish-scale type were formed at the joining area. The combination of smaller grains, acicular ${\alpha }^{\prime }$ martensite, and lamellar $(\alpha +\beta )$ structures was observed inside the interface zone. The hardness value at the interface area was measured by about 320 HV which is higher than 280 HV of the substrate and smaller than 369 HV of the as-built sample. The results predict that the SLS process is a promising method for manufacturing of hybrid materials.

A Sr-incorporated Na–Ti–O nano-network with a lateral pore size of 20–300 nm was developed on titanium (Ti) substrate using one-step alkali etching in a mixed solution of NaOH and Sr(OH)₂. The pore size of coating increases with Sr content, implying the proper amount of Sr in the electrolyte accelerates nanowire aggregation. The Sr(OH)₂ particle precipitation has no significant effect on the coating morphology. Moreover, biological experiments suggest the prepared coating exhibits good cytocompatibility, and the amount of Sr under 0.7 at.% has no noticeable promoting effect on the cytocompatibility.

The effects of the electrical bias conditions on oxide film during titanium MAO (microarc oxidation) were investigated. Since DC voltage showed very low stabilized currents but produced oxide films with poor quality, the magnitude of applied voltages, duty cycles, and frequencies were modulated to control the quality of the oxide film. Pulsed voltage showed increased stabilized currents but produced better oxide films. The change in the stabilized currents was attributed to the change of the resistances of the film and local electrolyte adjacent to the anode. Analysis of the film thickness and the resistances of the film calculated from the experiments led to conclusion that the resistance of the electrolyte adjacent to the anode was increased if the negative ions attracted towards the anode were not reacted as fast as the positive ions at the cathode. The increase in resistance was attributed to the excess negative ions repelling other negative ions. In order to relax the negative ions, it appeared that a pulsed voltage source was essential. However, higher off-duty cycle was not the best choice to produce good oxide films indicating that the electrical bias condition depended on the experimental configuration.

This paper describes the fabrication of a Cu-coating on pure titanium via plasma surface alloying technology. The surface morphology, cross-sectional microstructure and elemental distributions of the coating were analyzed by scanning electron microscope (SEM) and glow discharge optical emission spectroscope (GDOES). The antibacterial property of the Cu-coating was assessed via in vitro bacterial adhesion test. The results showed that the Cu-coating was continuous and compact. The Cu-coating endowed pure titanium with a promising antibacterial property.

The technique of X-ray photoelectron spectroscopy has been used to investigate the chemical reactivity at the metal/CuO interfaces. Thin films of the metallic overlayer (0.5 nm, 1.0 nm and 2.0 nm thickness) were deposited on copper oxide substrates at room temperature. In situ characterization of the interfaces has been performed. The 2p core level regions of the metals have been investigated. The spectral features show considerable reactivity at the interfaces. The core level peaks of the metal are observed to be shifted to the high BE energy side with the appearance of satellites. The spectral data confirm the formation of the metallic oxide at the interface. The satellite structure in the copper region is observed to disappear and the spectral features are found to approach those of elemental copper. The room temperature deposition of the metal on copper oxide therefore results in the reduction of copper oxide to elemental copper followed by the oxidation of the metal. The interface is found to consist of a mixture of metal oxide and elemental copper. The 2.0 nm samples were annealed. These samples show the diffusion of copper oxide through the overlayer. The metal reacts with this diffusing oxide to form metallic oxide. The interface is found to consist of a mixture of unreacted metal, the metal oxide, and elemental copper. The amount of the unreacted metal varied between 0% and 40% and can be controlled by the processing conditions. The investigation shows room temperature chemical reactivity at the metal/CuO interface and provides a new method of preparing sub-nano-oxide films.

Laser welding has the benefit of hardly causing welding deformation as it requires less heat input than existing welding methods. The heat input is determined by the laser output and welding speed, and the penetration depth, bead width, joining length, and bead shape are varied depending on these two welding parameters. In this study, bead and lap welding were performed on a thin pure titanium plate with a thickness of 0.5 mm using a disk laser with a maximum output of 3.3 kW. Weldability was evaluated by observing the penetration depth, bead width, joining length, and bead shape for different laser outputs and welding speeds. Results show that a weld zone with excellent joining length can be obtained for an output of 1.1 kW and speed of 2.5 m/min, as well as for an output of 1.3 kW and speed of 3.5 m/min in lap welding. Tensile-shear test was conducted with the specimens under these two conditions to investigate their mechanical characteristics.

The mechanism of plastic deformation under tensile and compressive loading of hexagonal close-packed (HCP)/face-centered cubic (FCC) biphasic titanium (Ti) nanopillars at different temperatures (70 K, 150 K, 300 K and 400 K) and different FCC phase sizes (2 nm, 4 nm, 6 nm and 8 nm) was investigated by molecular dynamics (MD). The plastic deformation is mainly concentrated in the FCC phase during compression loading. The HCP/FCC interface is the main source of $\frac{1}{6}〈\bar{1}\bar{2}1〉$ Shockley partial dislocations. As the temperature increases, the dislocation nucleation rate increases and the surface dislocation source is activated. During tensile loading, it is more likely that the Shockley partial dislocations react with each other in the FCC phase to form Lomer–Cottrell sessile dislocations and stacking fault (SF) nets. When the temperature is reduced to 70 K, tensile twins are formed at the phase interface. The plastic deformation is dominated by twins and $〈\mathrm{\text{c}}+\mathrm{\text{a}}〉$ dislocation slip occurs in the HCP phase. The effect of the FCC phase size on the plastic deformation mechanism of the nanopillar is strong. The FCC phase is transformed into the HCP phase when the FCC phase size in the nanopillar is reduced to 4 nm under compressive loading. However, twin deformation occurs at the HCP/FCC interface when the FCC phase size is reduced to 2 nm under tensile loading.

In powder-mixed electrical discharge machining (PMEDM), the application of low-frequency vibrations to a workpiece is considered beneficial to the machining quality. This study evaluates the average surface roughness (Ra) of SKD61 steel workpieces subjected to low-frequency vibrations during PMEDM using a Cu electrode and titanium powder. Specifically, Taguchi’s L25 experimental design method is used to evaluate the influence of the following process parameters: current, pulse-on time, concentration, push pressure, frequency, and amplitude. The analysis of variance technique is used to determine the minimum Ra (Ra${}_{min}$) value. The results show that Ra is most and least strongly influenced by $I$ and $A$, respectively. Further, Ra${}_{min}$ is found to be 1.03 $\mu$m.