Crystal Titanium Research Articles

Molecular dynamics simulations of the nanoindentation process of titanium crystal

We present the results of the large-scale molecular dynamics simulations of nanoindentation of a titanium crystal. By considering three different types of the indenter, namely of square, conical and spherical shapes, we observe the dependence of deformations of the crystalline structure on the type of the indenter. Various load-displacement curves are observed for different intender types. For each case study we perform molecular dynamics simulation of a full indentation cycle, which includes the loading and unloading stages. On the basis of such simulations we evaluate elastic properties of the material, namely we calculate the hardness and Young’s modulus. We observe the dependence of the obtained values of hardness and Young’s modulus on the type of the indenter and discuss the origin of this dependence.

Computer simulation of diffusion process at interfaces of nickel and titanium crystals

We present results of classical molecular dynamics simulations of the diffusion processes occurring at the nickel and titanium surfaces. The interaction between metal atoms is treated using Finnis–Sinclair potential. In particular, we study the diffusion process at the interface of pure nickel and titanium crystals and derive the diffusion coefficient for Ni and Ti atoms in the temperature range 500−700K. Assuming exponential dependence of the diffusion coefficient on temperature we predict its value at room temperature. We study also the diffusion of Ni55 cluster on the titanium surface in the presence of water environment. We analyze the dynamics of nickel atoms in the cluster, describe structural rearrangements occurring in the cluster due to the interaction with titanium surface and derive diffusion coefficient for Ni atoms.

Microstructure Evolution of Titanium Nitride Film during Vacuum Kinetic Spraying

Single crystal titanium nitride powder was used to fabricate titanium nitride films using a vacuum kinetic spray (VKS) process. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (FETEM) were used to investigate the microstructure of the as‐fabricated films under different process conditions. Plastic deformation features (i.e., amorphization, rotated grain, slip bands, and distorted lattices in the transition structure) revealed an elastic‐to‐inelastic transition of titanium nitride particles at high strain rate and high pressure induced by hypervelocity impact, which was considered vital for grain refinement and film growth during the process.

Study of Tension Process of Single Crystal Titanium Nano-Rod Based on the Molecular Dynamics

In this paper, the axial tensile process of single crystal titanium nano-rod is simulated based on the Finnis-Sinclair embedded atom potential by molecular dynamics. The mechanical properties of the titanium nano-rod with different cross-section dimension along three orientations ([0001]、[-12-10]、[10-10]) are analyzed. The results show as follows: 1) The tension process of titanium nano-rod along three orientations all includes four stages which are elastic deformation, uniform plastic deformation, localized necking and fault stage. 2) The larger the cross-section is, the smaller the yield stress is. 3) Along the [0001] orientation the yield stress and elastic modulus of titanium nano-rod is the largest, but fracture strain is the smallest; along the [-12-10] orientation the yield stress and elastic modulus is the smallest, but the fracture strain is the largest; along the [10-10] orientation the tension mechanical properties is in the middle of the other two orientations.

Defect-driven synthesis of self-assembled single crystal titanium nanowires via electrochemistry

One-dimensional single crystal nanostructures have garnered much attention, from their low-dimensional physics to their technological uses, due to their unique properties and potential applications, from sensors to interconnects. There is an increasing interest in metallic titanium nanowires, yet their single crystal form has not been actualized. Vapor–liquid–solid (VLS) and template-assisted top-down methods are common means for nanowire synthesis; however, each has limitations with respect to nanowire composition and crystallinity. Here we show a simple electrochemical method to generate single crystal titanium nanowires on monocrystalline NiTi substrates. This work is a significant advance in addressing the challenge of growing single crystal titanium nanowires, which had been precluded by titanium’s reactivity. Nanowires grew non-parallel to the surface and in a periodic arrangement along specific substrate directions; this behavior is attributed to a defect-driven mechanism. This synthesis technique ushers in new and rapid routes for single crystal metallic nanostructures, which have considerable implications for nanoscale electronics.

The hybrid photocatalyst of TiO2–SiO2 thin film prepared from rice husk silica

The TiO2–SiO2 thin film was prepared by self-assembly method by mixing SiO2 precursor with titanium precursor solution and aged to obtain a co-precipitation of silica and titanium crystals. Dip coating method was applied for thin film preparation on glass slide. The X-ray diffraction (XRD) of the self-assembly thin film had no characteristic property of SiO2 and even anatase TiO2 but indicated new crystal structure which was determined from the Fourier Transform Infrared Spectrophotometer (FTIR) as a hybridized Ti–O–Si bonding. The surface area and surface volume of the self-assembly sample were increased when SiO2 was incorporated into the film. The self-assembly TiO2–SiO2 thin film exhibited the enhanced photocatalytic decolorization of methylene blue (MB) dye. The advantages of SiO2 are; (1) to increase the adsorbability of the film and (2) to provide the hydroxyl radical to promote the photocatalytic reaction. The self-assembly thin film with the optimum molar ratio (SiO2:TiO2) as 20:80 gave the best performance for photocatalytic decolorization of MB dye with the overall efficiency of 81%.

Low-Temperature Preparation of Single Crystal Titanium Carbide Nanofibers in Molten Salts

The synthesis of single crystal titanium carbide (TiC) nanofibers has been investigated by the reaction of carbon sources of various sizes and microstructures with an equimolar mixture of titanium dioxide (TiO2) and titanium metal powders, in a molten salt medium. The carbon sources included carbon lamp black, thermal carbon black, pyrolytic carbon black, and multiwalled carbon nanotubes (MWCNTs). The reaction of titanium with TiO2 in molten salt to form titanium monoxide and the absence of reaction of titanium oxides with carbon nanotubes in molten salt is also reported. A reasonable yield of single crystal TiC nanofibers can only be achieved with the pyrolytic carbon black and MWCNT carbon sources. The product needs purification in hydrofluoric acid to remove TiO2 surface contamination. Four-point electrical measurement of a purified nanofiber in a dual scanning electron microscope–scanning tunneling microscope (SEM–STM) nanoprober confirms the stoichiometry TiCx to be x = 0.95. The results suggest that...

Optical Energy Gap of Ti:Al2O3 Single Crystals

The optical absorption spectra of single crystals of titanium doped sapphire (Ti:A1203) with two different doping concentration (0.1% wt. and 0.25% wt.) have been recorded in the UV-visible spectroscopy at room temperature. It was observed that both crystals start to show strong absorptions around 325 run. From this spectrum attempt was made to estimate the values of energy gap and the type of transition occurs in Ti:A1203o From the analysis it show that the optical energy gap are 5.57 eV for 0.1% wt. Ti and 5.94 eV for 0.25 wt.% Ti and it a direct band gap transition.

Influence of hydrogen on hot deformation behavior and microstructure of pure titanium

The influence of hydrogen on the hot deformation behavior and the microstructure after deformation of pure titanium crystal was investigated. The results show that hydrogen in pure titanium crystal can reduce the flow stress of hot deformation; The flow stress peak is decreased best by 60% in a Ti-H crystal specimen deformed at 600–800°C and the peak flow stresses exhibit a trough behavior with the hydrogen concentration, that is, there is a minimum of peak flow stress at a certain hydrogen concentration. Through the analysis of microstructure, the great amounts of needle-like martensite and the small number of dislocations within the sub-grains in Ti-H crystal after hot deformation. These indicate that the hydrogen can increase the volume of β phase and can promote the dynamic recovery in the deformation process at high temperature, as a result, it decreases the flow stresses effectively.

Mg5TiO4(BO3)2

Single crystals of pentamagnesium titanium(IV) tetraoxide bis(borate), Mg(5)TiO(4)(BO(3))(2), were prepared by slow cooling of the melt from 1623 K in air. The crystal is isostructural with the mineral ludwigite (Mg(2)FeO(2)BO(3)). The Mg and Ti atoms are coordinated by six O atoms and the B atom is coordinated by three O atoms. There are three Mg sites and one mixed site statistically occupied by Mg and Ti atoms. Atoms are at the following special positions: 2a (0, 0, 0) and 2d (0, 1/2, 1/2) for two Mg atoms, 4g (x, y, 0) for the mixed Ti/Mg site and the BO(3) group, and 4h (x, y, 1/2) for a third Mg and two oxide O atoms. MgO(6) and (Ti/Mg)O(6) octahedra are connected by sharing of edges to form zigzag folding layers along the c axis. Triangular prismatic tunnels are formed between the folding layers by sharing apical O atoms of the MgO(6) and (Ti/Mg)O(6) octahedra.

Electro-migration effect of titanium structure under high magnetic field

It is well known topic that electro-migration accompanies the transport of atoms, ions and holes in a material. Then we can say that both electro-migration and strong magnetic field have potential to control crystal alignment. In this study, an electric current and/or a static magnetic field were applied to a titanium sample parallel to each other to investigate the effects of the electric current and the static magnetic field on crystal alignment in the titanium. Using XRD analysis, it was understood that titanium crystals having a c-axis perpendicular to the electric current direction increased under the imposition of only the electric current and under the simultaneous imposition of the electric current and the magnetic field. On the other hand, titanium crystals having a c-axis parallel to the magnetic field direction increased under the imposition of only the magnetic field. The aligned result can be explained from the viewpoint of anisotropy of the Joule loss and the magnetization energy.

Molecular dynamics simulation of helium cluster growth in titanium

The growth of helium cluster in titanium crystals at room temperature has been simulated detailedly by means of molecular dynamics. The mechanism of helium cluster growth in metal materials has been investigated from the viewpoint of energy. It is found that, as the helium cluster grows, dislocation loops are formed around the cluster and the binding energy of each additional helium atom to these clusters tends to decrease. However, at certain point in the growth process, the defects escape rapidly and the binding energy increases, helping the further growth of the helium cluster. As more helium atoms are introduced, the shape of the helium cluster is transformed gradually to a prismatic morphology from the irregular morphology and its thickness is always observed to be about 1.2 nm, without any obvious variation with degree of helium filling.

Mechanism of Hydrophilicity by Radiation-Induced Surface Activation

When a metal oxide is irradiated by gamma rays, the irradiated surface becomes hydrophilic. This surface phenomenon is called as radiation-induced surface activation (RISA) hydrophilicity. In order to investigate gamma ray-induced and photoinduced hydrophilicity, the contact angles of water droplets on a titanium dioxide surface were measured in terms of irradiation intensity and time for gamma rays of cobalt-60 and for ultraviolet rays. Reciprocals of the contact angles increased in proportion to the irradiation time before the contact angles reached its super-hydrophilic state. The irradiation time dependency is equal to each other qualitatively. In addition, an effect of ambient gas was investigated. In pure argon gas, the contact angle remains the same against the irradiation time. This clearly indicates that certain humidity is required in ambient gas to take place of RISA hydrophilicity. A single crystal titanium dioxide (100) surface was analyzed by X-ray photoelectron spectrometry (XPS). After irradiation with gamma rays, a peak was found in the O1s spectrum, which indicates the adsorption of dissociative water to a surface 5-fold coordinate titanium site, and the formation of a surface hydroxyl group. We conclude that the RISA hydrophilicity is caused by chemisorption of the hydroxyl group on the surface.

A convenient, general synthesis of carbide nanofibres via templated reactions on carbon nanotubes in molten salt media

Carbide nanofibres were synthesized by reaction of various transition metals with carbon nanotubes using a molten LiCl–KCl–KF salt system as a reaction medium. Metal sources included titanium, zirconium, hafnium, vanadium, niobium and tantalum powders. Multi-walled carbon nanotubes were used both as a carbon source and also as a template for the preparation of titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide and tantalum carbide nanofibres. Generally, the carbide products were characterized by scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction and electron energy loss spectroscopy. The polycrystalline carbide nanofibres produced in these reactions have a similar morphology to that of their multi-walled carbon nanotube precursors. However, when using titanium mixed with titanium dioxide as a titanium source, both polycrystalline and straight, single crystal titanium carbide nanofibres are formed.

Structure of crystals of iodide titanium obtained by a solid-state reaction using α → β → α phase transitions

Results of metallographic and electron-microscopic studies of a structure observed on the surface of crystals of iodide α-Ti that are produced by thermal cycling in a textured matrix are presented. It is shown that the structure in the form of slip and twin traces, which is formed under the effect of a phase transition and thermal stresses, is oriented with respect to the rolling direction of the textured matrix. The results of electronmicroscopic analysis have demonstrated that the character of the dislocation structure of weakly deformed α-titanium crystals does not depend on the crystallographic orientation.

Coalescence of helium clusters in titanium crystals: Molecular dynamics simulation

In this paper, the helium behavior in titanium crystals has been simulated by molecular dynamics method. The coalescence of helium clusters has been investigated in great detail in a range from 300 to 800K. It was found that increasing temperature contributes to the coalescence of helium clusters. However, the helium cluster resulting from coalescence assumes its three-dimensional configuration in this temperature range for the time scale of simulation. The simulation results also indicate that, at room temperature, the attractive force between helium clusters plays a key role in helium cluster coalescence.

Defect behavior induced by helium cluster growth in titanium crystals

The growth of helium cluster in titanium crystals is simulated in great detailed approach using molecular dynamics. We observe that, as the helium cluster grows, defects around the cluster are formed and the local pressure increases. However, at certain point in the growth process, the defects are found to rapidly escape as a whole from the helium cluster, accompanied by the relief of local high pressure and the recovery of Ti crystal structure around the helium cluster.

Apatite formation and cellular response of a novel bioactive titanium

The modification of titanium and titanium alloy surface properties by chemical and electrochemical techniques has opened new possibilities to improve the bioactivity and, in general, the biological performance of the implants once in vivo. One of the main aims is the achievement of a surface oxide layer that stimulates hydroxylapatite mineralization and, also, shows osteoconductive properties once in the host. In the present study, two different bioactive surfaces have been prepared following the method purposed by the group of Kokubo and a new method, BioSpark, involving high voltage anodic polarisation and alkali etching both on surface mineralization potential. The aim of the present work was to evaluate and compare the mineralization capability and the early cell response of titanium modified with a new bioactive method and with a well-known and widely tested biomimetic treatment, both compared to non treated titanium. Physical and chemical (energy dispersion spectroscopy, thin film X-ray diffractometry) and morphological (scanning electron microscopy) characterisation of the novel surface features has been performed. Also the effect of the novel surface properties on both hydroxyapatite precipitation and early cellular response has been investigated using in vitro models. The results have shown that both treatments produce an active outer layer on titanium but do not impair cells activity and support osteoblasts processes. BioSpark showed high bioactivity and good mineral phase deposition even after early incubation time, these properties were found in Kokubo's surface as previously published. Mineralisation mechanisms of the two materials were different, and while this mechanisms was well characterised and reported for Kokubo's surface, it was still unclear for BioSpark. In this paper an explanation was given and catalytic properties of the latter surface was bound to both well known crystal titanium oxide exhibiting anatase lattice and a certain level of calcium and phosphorus doping, which promoted chemical and physical variation in anatase properties. At the same time early osteoblasts response to Kokubo's and BioSpark's surface was characterised and, no significant differences was found.

Crystal Alignment of Titanium under Simultaneous Imposition of Electric Current and Magnetic Field

It is well known that the transport of atoms, ions and holes in a material is induced by electromigration. This implies that electromigaration can control the structure of a material. In this study, an electric current was applied to a titanium sample that was subjected to a static magnetic field to investigate the effects of the electric current and the static magnetic field on crystal alignment in titanium. An intensity ratio of (002) peak to (100) peak in XRD analysis was introduced as a crystal alignment index. Because the magnetic susceptibility of titanium in the c-axis is larger than what it is in the a-axis, titanium crystals having a c-axis parallel to the magnetic field are stable from the viewpoint of magnetization energy. However, the numbers of these crystals decreased after the experiment. On the other hand, the c-axis of the titanium crystals aligned themselves itself to become perpendicular to the direction of flow of the electric current to reduce the Joule loss in the sample, because the specific resistance in the c-axis was larger than that in the a-axis. This agrees with the experimental result. Therefore, in this experiment the titanium crystals in the sample aligned themselves to reduce the Joule loss even though the magnetic energy was larger than the thermal fluctuation in this experiment.

A crystal structure of mixed-metal dianionic phosphate Cs 3.70Mg 0.60Ti 2.78(TiO) 3(P 2O 7) 4(PO 4) 2

The single crystals of caesium magnesium titanium (IV) tri-oxo-tetrakis-diphosphate bis-monophosphate, Cs 3.70Mg 0.60Ti 2.78(TiO) 3(P 2O 7) 4(PO 4) 2, crystallize in sp. gr. P-1 (No. 2) with cell parameters a=6.3245(4), b=9.5470(4), c=15.1892(9) Å, α=72.760(4), β=85.689(5), γ=73.717(4), z=1. The titled compound possesses a three-dimensional tunnel structure built by the corner-sharing of distorted [TiO 6] octahedra, [Ti 2O 11] bioctahedra, [PO 4] monophosphate and [P 2O 7] pyrophosphate groups. The Cs + cations are located in the tunnels. The partial substitution of Ti positions with Mg atoms is observed. The negative charge of the framework is balanced by Cs cations and Mg atoms leading to pronounced concurrency and orientation disorder in the [P 2O 7] groups, which coordinate both.