Crystal Titanium Research Articles

Crack Propagation Behavior in Nano Size HCP Crystals by Molecular Dynamic Simulation

A crack propagation behavior of hcp crystal has been simulated by molecular dynamics method using Lennard-Jones type potential. A notch was introduced to model crystals with free surfaces. The size of the model was 13nm×24nm×4.6nm and about 80000 atoms were included in the model. A crack propagated by applying tensile strain on top and bottom layer of the model crystal. A definite dependence of crystallographic orientation on crack propagation behavior was obtained. In a model crystal with initial notch plane and direction were (101 0), [1 210], the crack propagated parallel to notch plane and two sets of prismatic slips were occurred at the crack. Therefore, the crack in this crystal is deduced to extend by alternating shear on two intersecting {101 0}, <1 210> prismatic slip systems. In a model crystal with (0001), [101 0] initial crack, {101 1} first order pyramidal slip occurred at crack tip and following {101 2} twin was also observed. In a model crystal with (10 1 0), [0001] initial crack, the crack propagates parallel to initial crack plane. Crack propagation rate of the crack near surface is faster than the crack in interior of the model. In this case, two prismatic slips were occurred in front of the crack. This result explains a mechanism of forming ‘Herring-born pattern’ which was observed in the titanium single crystal. Results obtained by these three models are well described the fatigue crack propagation behavior in hcp titanium crystals.

Dislocation study of prismatic slip systems and their interactions in hexagonal close packed metals: application to zirconium

Simulations of dislocation dynamics in single crystals of hcp zirconium are presented with emphasis on the hardening associated with prismatic slip at low temperature. Two original aspects of the simulation method are discussed, the treatment of the hcp lattice by an orthorhombic representation and the use of periodic boundary conditions. The mobility of screw and non-screw segments are defined in a phenomenological manner. Different investigations on the interactions between dislocations gliding in different prismatic planes show that no junction is formed between intersecting screw dislocations, which results in a rather small forest hardening at low temperature. This explains experimental observations of an initial deformation stage with a low strain hardening coefficient in zirconium or titanium crystals at low temperature.

Detergency of oily soil from cotton by photo-catalytic action with single crystal titanium dioxide using black light lamp

Detergency of oily soil from cotton by photo-catalytic action with single crystal titanium dioxide using black light lamp

Synthesis and characterization of nanosized titanium particles by gas-phase combustion

Abstract Nanosized titanium particles are produced by gas-phase combustion under low-temperature. Combustion behavior of a TiCl4–Na mixture in a flow of argon was investigated by coflow flame method depending on the processing parameters such as burner shape, argon pressure and temperature. The nanosized titanium particles of 20–100 nm covered by a thin layer of NaCl were obtained at the flame temperatures of 510–585 °C. The optimal condition of nanosized titanium particles synthesis was found. It was established that the titanium particles are well distributed in the range of 50–80 nm sizes after the NaCl was removed by sublimation in vacuum. The formation mechanism of titanium crystal with the salt by coflow method is described.

Electronic Structure and Chemical Bonding in Crystal and Molecular Titanium Carbides

Electronic Structure and Chemical Bonding in Crystal and Molecular Titanium Carbides

The Electronic Structure of Mixed Metcars Ti7MC12 (M = Y, Zr, Nb,..., Ag)

The electronic structures of a series of mixed metallocarbohedrenes (metcars) Ti7MC12formed as a result of replacement of the titanium atom in the Ti8C12metcar by 4dtransition metal ions (M = Y, Zr, Nb, ..., Ag) are established using the ab initioelectron density functional method in the discrete-variational scheme. The dependences of electronic structure, charge distributions, and chemical bonds in the Ti7MC12metcars on the cluster symmetry (Thor Td) and position of the 4datom in a molecular cage are discussed. The electronic states of 4datoms in molecular titanium carbide (Ti8C12metcar) are compared with those in crystal titanium carbide (cubic TiC phase with rock salt structure). The effect of doping of the Ti8C12metcar with 4datoms on its reactivity is studied.

Single titanium crystals encapsulated in carbon nanocages obtained by laser vaporization of sponge titanium in benzene vapor

A technique, laser vaporization by ablating at a solid target in the vapor phase, is developed to produce encapsulated titanium nanocrystals. By vaporizing sponge titanium in benzene vapor, the single titanium crystals encapsulated in carbon nanocages have been synthesized in good yields. The sizes of the encapsulated crystals are around 5–15 nm and the numbers of the wrapped graphitic layers are on the order of 3–10 layers. Characteristic lattice spacings and angles observed by high-resolution transmission electron microscopy identify two phases of the nanocrystals inside the carbon onion cavities as α-Ti and β-Ti. The latter has never been stable below 850 °C until the experiment. The encapsulated titanium crystals adsorbed a large amount of hydrogen released in the synthesis.

Titanium compounds as coatings on polystyrene latices and as hollow spheres

Sub-micron-sized anionic polystyrene latices have been coated with uniform layers of amorphous titanium dioxide by hydrolysis of titanium tetrabutoxide in ethanolic solutions containing the polymer cores. The thickness of the coating layer could be altered by adjusting the concentration of titanium tetrabutoxide and the amount of polymer latex added to the system. Hollow colloidal spheres of crystal titanium dioxide were obtained by calcination of the so-coated polystyrene latices at an elevated temperature.

Study on antiwear and reducing friction additive of nanometer titanium oxide

Nanometer crystal titanium oxide with a particle size of about 20 nm was prepared using ethanol supercritical fluid drying technique. Tribology properties of 500 SN oil with the nanometer particles were measured using four-ball and block-on-ring tribotester. Results indicated that wear resistance and load carrying capacity of 500 SN base oil were improved and friction coefficient was decreased by an addition of the nanometer particles. There was an optimal content of titanium oxide in the oil, which gave the highest maximum nonseized load. Nanometer titanium oxide took effect by its deposition on rubbing surface.

Study on antiwear and reducing friction additive of nanometer titanium borate

Crystal titanium borate with a particle size of 10–70 nm was prepared using Ethanol Supercritical Fluid Drying technique. Tribology properties of 500 SN base oil containing so-prepared nanometer titanium borate were evaluated. Results indicate that wear resistance and load carrying capacity of the oil were improved and the friction coefficient of the oil was decreased. The improvement of tribological properties of the oil under low load resulted from the deposition of the nanometer titanium borate. The deposition and tribochemical reaction produced some diboron trioxide on the wear scar.

Cyclic deformation behavior of high-purity titanium single crystals: Part I. Orientation dependence of stress-strain response

Randomly oriented single crystals of high-purity titanium were prepared by strain annealing and were subjected to multiple-step fatigue testing under strain-controlled conditions, in order to determine their cyclic stress-strain curves (CSSCs). These were found to fall into three groups, depending on orientation and the extent of slip and twinning. For those crystals oriented for single prismatic slip, a plateau was observed in the CSSCs, persistent slip bands (PSBs) occurred, and the plateau stress was 38 MPa. In a second group, oriented for prismatic slip but for which cross-slip and twinning was favored, the plateau was suppressed and the flow stresses were higher. In a third group, connected with orientations on the borders of the unit triangle, extensive hardening occurred, the CSSCs were steep, and there were multiple cases of slip and twinning. The results are interpreted in terms of maps in the stereographic projection recording the Schmid factors for the various deformation modes.

Cyclic deformation behavior of high-purity titanium single crystals: Part II. Microstructure and mechanism

Strain-controlled cyclic tests have been conducted on high-purity titanium single crystals with different orientations. The fatigue mechanisms of the titanium crystals were studied by means of a scanning electron microscope (SEM) and a transmission electron microscope (TEM). It was found that single slip lines, wavy slip lines, double slip lines, twins, and associated slip lines occurred in differently oriented single crystals. A new type of fractographic morphology, parallel traces, was observed. Dislocation patterns and cyclic twins, as well as the mechanical response, were analyzed. The dependence of the deformation mechanisms on the orientations of the single crystals is discussed.

Stress‐Induced Phase Transformation in Single Crystal Titanium Carbide

Single‐crystal ingots of TiC were cut into wafer substrates for heteroepitaxial growth of SiC films. During wafer sectioning by abrasive machining, a subsurface damage zone was created. TEM observations of the damage zone revealed a stress‐induced martensitic transformation from cubic TiC to rhombohedral and hexagonal structures, both involving an 8.0% contraction normal to the {111} habit plane and a shear along . It is proposed that the transformed structure is governed by the Ti sublattice, and that carbon atoms remain in octahedral coordination. The transformed phase coarsened to form a lamellar structure consisting of periodic quadlayer twins. The twins imparted hexagonal symmetry, and the lamellar phase was designated 8H. A strain gradient tensor was employed to describe the mapping of atom coordinates between the two phases. The present account constitutes the first report of this transformation in TiC.

Effects of ball milling intensity on structural changes in mixed 50Ni–50Ti powders during mechanical alloying process

Mixed 50Ni–50Ti powders were milled in an attritor high energy ball mill and the structural evolution of the milled powders characterised by X-ray diffraction analysis. The microstrain, crystallite size, and lattice parameters of the nickel and titanium crystals were measured. The results show that increases in the rotational velocity and the total ball volume/tank volume ratio leads to a decrease in the crystallite size and rapid changes in the microstrain and lattice parameters, which enhance the amorphisation rate, thereby reducing the time required to obtain afully amorphous phase.MST/2079

Improved X-ray and electron diffraction methods for twin determination in hexagonal crystals

Two improved methods of characterizing twin orientations in deformed crystals have been developed and compared; the back-scattered Kikuchi electron diffraction method in a standard scanning electron microscope and a new high-resolution X-ray pole-figure technique. Comparative tests on titanium and magnesium crystals deformed in plane strain compression up to high strains demonstrate their complementary features. The back-scattered Kikuchi diffraction technique, which combines imaging and microdiffraction, is well adapted to localized twin-orientation studies in both single and polycrystals after careful surface preparation. The high-resolution X-ray pole figures can be used for more quantitative studies of twinned volume fractions, including very fine twins, in crystallographically oriented samples such as deformed single crystals or large-grained polycrystals.

Decomposition of hexafluoroacetylacetonate Cu(I) vinyltrimethylsilane on, and diffusion of Cu into single crystal and polycrystalline titanium nitride

Decomposition of hexafluoroacetylacetonate Cu(I) vinyltrimethylsilane on, and diffusion of Cu into single crystal and polycrystalline titanium nitride

Computer Simulation of Tensile Deformation of Titanium Small Single Crystals with Stacking Faults

AbstractSmall single crystals of titanium with and without stacking faults have been pulled by use of the molecular dynamics method. The tensile axis was [0001] and the stacking fault was introduced on (0001) pianes. The yield stress was higher in the crystal with stacking faults. The deformation was complicated in the crystal with stacking fault. Dislocations were created near the tip of a crack and moved on (1122).

The growth of titanium, chromium and molybdenum disilicide crystals from high-temperature solutions

The possibility of preparing TiSi 2, CrSi 2 and MoSi 2 single crystals by crystallization from solution in molten metals has been investigated. The applicability of the different metals from the IB group to the VB group of the periodic table as high-temperature solvents is analysed, and on this basis tin is chosen as a solvent. Crystals of the three disilicides are grown from solutions in tin using the slow-cooling technique with different rates and different Sn:M′ ( M′ = Ti, Cr or Mo) ratios.

Crystal growth and optical properties of LaMgAl 11O 19: Ti 3+

Single crystals of titanium doped lanthanum-magnesium hexaluminate LaMgAl 11−xTi xO 19 have been pulled through the Czochralski method up to diameters 25 mm and length 70 mm. The broad emission band lies from 640 to 1100 nm.

Dislocations and twins in pure β titanium crystals characterized by synchrotron x-ray topography

Little is known about pure ..beta.. titanium crystals because of the difficulties encountered in observing them above the phase transformation point (..cap alpha..Ti (h.c.p.) in equilibrium ..beta..Ti (b.c.c.) at 870-885/sup 0/C) and in retaining the ..beta..-structure during cooling from the high temperature phase to room temperature. The main published results about these crystals concern the crystallographic relations they have with the ..cap alpha.. crystals and their thermal and mechanical properties. Little has been reported on their crystalline quality. This paper analyzes the defects which may exist in these crystals. Thus an ''in situ'' and real time synchrotron X-ray topographic study of crystals grown by recrystallization in the ..beta.. phase, has been carried out. Long dislocations and annealing twins have been observed and characterized and the different possibilities of their origin are discussed.