Surface Layer Of Titanium Research Articles

Ультразвуковая ударная обработка поверхностного слоя титана ВТ1-0 в субмикрокристаллическом состоянии

Ультразвуковая ударная обработка поверхностного слоя титана ВТ1-0 в субмикрокристаллическом состоянии

Modification of the structure of surface layers of commercial titanium in the process of treatment by low-energy high-current electron beams

Methods of optical, atomic-force, and transmission and scanning electron microscopy, as well as X-ray diffraction analysis have been used to study the effect of electron-beam treatment on the surface morphology and structure of titanium of grade VT1-0. It has been shown that irradiation by three electron pulses with an energy density in the beam of W = 12–24 J/cm2 and a pulse duration of 50 μs leads to the formation of VT1-0 samples of a multilayer structure in the surface layers that consist of fine particles of the α phase, which have a subgrain structure, and of the underlying coarse grains, which contain α’ martensitic phase. The influence of the density of energy of the electron beam on the hardness and the magnitude of microand macrostresses that develop in the modified surface layer has been demonstrated. The results of calculating the thermal fields that appear in the process of treatment by electron beam are presented.

Effect of hybrid oxidation on the titanium oxide layer's properties investigated by spectroscopic methods

In this work the study of hybrid Ti Grade 2 during oxidation using FADT – fluidized bed atmospheric diffusive treatment and PVD – magnetron sputtering have been investigated. Additionally, the influence of the oxidation method on the change in the mechanism of oxygen transport to the substrate have been discussed (phenomenon responsible for the improvement of bioactivity). Presented method consists in forming the titanium surface layer saturated with oxygen due to the diffusion and deposition of a thin homogeneous oxide coating on the Ti surface. Discussed processes diminish the surface roughness and increase bio-compatibility of the surface, which results in easier hydroxyapatite cluster deposition. The diffusion process was conducted on Al2O3 fluidized bed, with air as the fluidizing factor at 913 K for 8 h. The deposition of the oxide coatings were carried out with magnetron sputtering, with the use of a TiO2 target at a pressure of 3 × 10−2 mbars and power of 350 W. To evaluate the effects of hybrid oxidation and to determine the mechanism of oxygen transport, the following research methods have been applied: spectroscopy (GDOS, SIMS, RS), microscopic methods (SEM-EDS, SEM-EBSD, TEM-EFTEM), X-ray tests (μ-XRD, GID). Obtained test results were used to identify the type of oxide coatings, to assess the thickness of the layers and to study the influence of crystallographic orientation on oxygen transport and concentration in the surface layer and in the oxide coating. It has been found that the formation of oxide coatings created by using the hybrid method (FADT + PVD leads to a change in oxygen concentration in the substrate due to introduced defects. This phenomenon is in opposition to the conventional methods such as: electrochemical or laser oxidation. In contrast, forming a tight homogeneous oxide coating on Ti surface improves the biocompatibility, which is particularly important in the context of biomedical applications.

Preparation of anatase surface layers via carbon implantation into titanium

The conversion of the surface layer of a titanium containing sample into anatase has been tried many times by oxygen implantation and simultaneous or subsequent heating. The result, however, was in most cases the titanium dioxide modification rutile or, especially for titanium alloys, a mixture of anatase and rutile. Here a method is presented to manufacture a titanium dioxide surface layer with an initial implantation of carbon into the surface. A subsequent heating in air removes most of the carbon and replaces it with oxygen, thus generating the anatase modification.

Analysis of Structure Formed in a Titanium Surface Layer Alloyed with Yttrium

Modification of a titanium surface layer with yttrium is performed by a combined method providing electroexplosive alloying and subsequent treatment by a high-intensity electron beam. Alloyed layer elemental and phase composition, defect substructure, mechanical and tribological properties are determined. Saturation of a titanium surface layer with atoms of yttrium, oxygen, and carbon is revealed, which leads to the formation of a cermet layer strengthened with titanium and yttrium oxides and carbides and facilitates a multi-fold increase in microhardness and a reduction in modified layer friction coefficient and wear rate.

Ca/P rich nanostructured titania surface layer produced by anodic oxidation of titanium

Ca/P rich nanostructured titania surface layer produced by anodic oxidation of titanium

Структура, фазовый состав и свойства поверхностных слоёв титана после электровзрывного легирования иттрием и электронно-пучковой обработки

Структура, фазовый состав и свойства поверхностных слоёв титана после электровзрывного легирования иттрием и электронно-пучковой обработки

Structure and phase composition of Nb/Ti system subjected to compression plasma flow impact

The results of structure, phase composition and mechanical properties of titanium alloyed with niobium atoms by means of compression plasma flow (CPF) impact on the “Nb coating (2.5μm)/Ti substrate” system are presented. The CPF treatment with the pulse duration of 100μs was carried out at the absorbed energy density of 13J/cm2 which is sufficient for melting of both niobium coating and some part of titanium substrate. The cross-section analysis by means of scanning electron microscopy revealed the formation of the alloyed layer with the thickness of 14μm and relatively uniform distribution of Nb along the depth (Nb concentration obtained by means of the EDX analysis was about 17at.%). Alloying of titanium with Nb atoms resulted in stabilization of a high-temperature β-Ti phase as a β-Ti(Nb) solid solution. In the near surface layer the niobium interacted with impurity atoms (N and C) providing carbonitride (Nb(C,N) and carbide and Nb2C) possible formation. Phase transformation in the surface layer of titanium led to microhardness increase up to 4.7GPa.

Structure and properties of titanium surface layers after electron beam alloying with powder mixtures containing carbon

The structure and tribological properties of commercially pure titanium (cp-Ti) samples after non-vacuum electron beam surface alloying with carbon were studied. Two types of powders were used to introduce carbon in surface layer of cp-Ti: titanium carbide (TiC) and mixture of pure titanium and graphite (“Ti+C”). Single layer and multilayer coatings were studied. Application of electron beam for alloying provided cladding rate of 4.5m2/h. The thickness of the clad coatings was 1.6–2.0mm. The main phases received after “Ti+C” powder cladding were α-titanium, TiC, and retained graphite. In the samples obtained by cladding of TiC, graphite was not observed. A factor determining the microhardness and tribological properties of the cladded layer was the volume fraction of TiC. Maximum coating microhardness of 8GPa was obtained by cladding of single layer of TiC powder or two layers of the “Ti+C” mixture. Two types of tests were carried out to evaluate the wear resistance of the samples. In friction tests against loose abrasive particles, the wear rate of the best samples was 9.3 times lower than that of cp-Ti. In wear tests using fixed abrasive particles, the relative wear resistance of the best samples was 2.3 times higher than that of cp-Ti.

STRUCTURE AND MICROHARDNESS OF TITANIUM ALLOYS AFTER ELECTROMECHANICAL TREATMENT AND ULTRASONIC SURFACE ALLOYING

The authors proposed the complex technology of surface hardening of titanium alloys based on a combination of surface alloying with boron and carbon, electromechanical treatment (EMT) and non-abrasive ultrasonic fi nishing (NUF). The results of the study of microhardness and features of the structural-phase state of the surface layer of 5V titanium pseudo-α-type alloy were presented after various combinations of treatments (EMT, NUF, surface alloying). It was shown that for a variety of schemes hardening was achieved by increasing the surface microhardness of the treated material to 30 – 40 %. The greatest effect can be observed when using alloying agent during EMT + NUF (graphite cast powder in combination with an organic binder). Increase in microhardness was provided due to the hardening by severe plastic deformation of the metal, grain size refi nement (from 50 to 1 μm) during phase transitions, as well as the formation of fi ne reinforcing borides and carbides of titanium (whose content in the surface layer increased up to 1.88 and 0.46 %, respectively).

Influences of the pH on the adsorption properties of an antimicrobial peptide on titanium surfaces

The adsorption behavior of the Tet-124 antimicrobial peptide and the Tet-124 peptide modified at the C- and N-terminus with the sequence glycine-3,4-dihydroxyphenylalanine-glycine (G-DOPA-G) on titanium surfaces was studied using quartz crystal micro balance with dissipation (QCM-D). At a low pH level (4.75) Tet-124 and Tet-124-G-DOPA-G form rigid layers. This is attributed to the electrostatic interactions of the positively charged lysine and arginine residues in the peptide sequence with the negatively charged titanium oxide layer. At an elevated pH level (6.9) Tet-124 shows a lower mass adsorption at the surface than Tet-124-G-DOPA-G. This is attributed to the interaction of the catechol due to the formation of complexes with the titanium oxide and titanium surface layer. The C terminal and N terminal modification with the sequence G-DOPA-G shows similar adsorption rate and mass adsorption coverage at saturation; however it is presented a more loosely layers on the G-DOPA-G-TeT-124. Fibroblast adhesion and the biocompatibility test of both the surfaces following modification with Tet-124-G-DOPA-G and the titanium alloy control showed similar results. In addition, no changes in the adhesion of E. coli bacteria due to the modification of the surface were detected.

Formation of a microcomposite structure in the surface layer of yttrium-doped titanium

Surface layers containing oxides and carbides of titanium and yttrium are prepared by the electroexplosive doping of titanium with yttrium. The subsequent electron-beam irradiation leads to dispersion of the structure to a nano- and submicron state. The formation of two types of eutectics is revealed using scanning electron microscopy. The eutectics enriched in titanium and yttrium have a globular and plate-like shape, respectively. The formation of a modified surface layer (enriched in yttrium, carbides and oxides of titanium and yttrium) leads to a threefold increase in the microhardness of the titanium, a more than twofold decrease in the friction coefficient of the doped layer, and a more than 2.8-fold decrease in the wear rate.

Modification of the Titanium Surface Layer by the Yttrium

Modification of a titanium surface layer with yttrium using the combined technique of electroexplosive doping and the subsequent irradiation by a high-intensity electron beam is carried out. The studies on the structure, the element and the phase composition, mechanical and tribological properties of the doped layer are carried out. Formation of a multiphase submicron-nanocrystalline eutectic is revealed. A multifold increase in the microhardness, a decrease in the friction coefficient and the wear rate of the modified layer is established.

Porous titania surfaces on titanium with hierarchical macro- and mesoporosities for enhancing cell adhesion, proliferation and mineralization.

Titanium received a macroporous titania surface layer by anodization, which contains open pores with average pore diameter around 5 μm. An additional mesoporous titania top layer following the contour of the macropores, of 100-200 nm thickness and with a pore diameter of 10nm, was formed by using the evaporation-induced self-assembly (EISA) method with titanium (IV) tetraethoxide as the precursor. A coherent laminar titania surface layer was thus obtained, creating a hierarchical macro- and mesoporous surface that was characterized by high-resolution electron microscopy. The interfacial bonding between the surface layers and the titanium matrix was characterized by the scratch test that confirmed a stable and strong bonding of titania surface layers on titanium. The wettability to water and the effects on the osteosarcoma cell line (SaOS-2) proliferation and mineralization of the formed titania surface layers were studied systematically by cell culture and scanning electron microscopy. The results proved that the porous titania surface with hierarchical macro- and mesoporosities was hydrophilic that significantly promoted cell attachment and spreading. A synergistic role of the hierarchical macro- and mesoporosities was revealed in terms of enhancing cell adhesion, proliferation and mineralization, compared with the titania surface with solo scale topography.

Combined electron-ion-plasma doping of a titanium surface with yttrium: Analyzing structure and properties

A titanium surface layer is modified with yttrium by combining electroexplosive doping and high-intensity electron-beam irradiation. The element and phase content, defect substructure, and mechanical and tribological characteristics are investigated for the doped layer. Saturating the surface titanium layer with yttrium, oxygen, and carbon atoms is shown to produce a metalloceramic layer reinforced with oxides and titanium and yttrium carbides that results in a multifold increase in microhardness and reduces the friction coefficient and wear rate in the modified layer.

Structure and properties of surface layers obtained due to titanium-surface alloying by yttrium via combined electron-ion-plasma treatment

The surface layer of titanium is modified via a combined method involving electroexplosive alloying by yttrium and subsequent high-intensity electron-beam irradiation. The elemental and phase composition, defect substructure, and mechanical and tribological characteristics of the alloyed layers are investigated. The titanium-surface layer is revealed to be saturated with yttrium, oxygen, and hydrogen atoms, which give rise to the formation of a metal-ceramic layer hardened with titanium and yttrium oxides and carbides and stimulate a manifold increase in the microhardness and a decrease in the friction coefficient and wear rate of the modified layer.

Structure and Properties of Surface Alloys in Ti-Y System

The doping of the surface layer of titanium by the yttrium, oxygen and carbon was implemented. Irradiation of the doped layer by intense electron beam leads to the formation of the multiphase structure and the nanosubmicron range having a high microhardness (at 3-fold higher than the hardness of the original structure) and a low coefficient of friction (6 times lower than the friction coefficient of the starting material).

Effect of severe plastic deformation on the structure, microhardness, and wear resistance of the surface layer of titanium subjected to gas nitriding

The effect of severe plastic deformation under dry sliding friction on the structure, microhardness, and wear rate of the VT1-0 titanium subjected to gas nitriding has been studied. It has been shown that this deformation leads to the formation of a nanocrystalline structure with an α-crystal size of 10–100 nm and a microhardness of ∼3.1 GPa in a surface layer up to 10 μm thick. The presence of this structure intensifies the saturation of the surface of the titanium with nitrogen in the course of subsequent gas nitriding at temperatures of 650–750°C. The formation of the nitride nanocrystalline TiN phase in the deformed titanium occurs at a relatively low nitriding temperature (700°C) and a short-term holding (2 h). The volume fraction of the nitride phase, which is formed in the layer up to 10 μm thick, reaches a few tens of percent, which leads to an increase in the microhardness of the nitrided surface of the titanium deformed by friction. Preliminary severe plastic deformation has a negative effect on the fatigue wear resistance of the nitrided titanium due to an increased brittleness of the deformed and subsequently nitrided surface layer of this material.

Kinetics of the Diffusion Saturation of VT1-0 Titanium Alloy with Nitrogen and Oxygen at a Temperature of 950°С

We analytically describe the roles of nitrogen and oxygen as α-stabilizers in the formation of a three-layer diffusion zone (on the base of α-, (α + β)-, and β-phases) in VT1-0 titanium alloy. The constants of growth of these layers (at T = 950°С) are calculated, which enables us to predict the kinetics of changes in their thickness and the distribution of an interstitial elements (nitrogen or oxygen) in the diffusion zone. The evolution of microstructure of the surface layer of titanium after nitriding is experimentally recorded (after holding for 1 and 5 h).

Water Adsorption at the Tetrahedral Titania Surface Layer of SrTiO3(110)-(4 × 1).

The interaction of water with oxide surfaces is of great interest for both fundamental science and applications. We present a combined theoretical (density functional theory (DFT)) and experimental (scanning tunneling microscopy (STM) and photoemission spectroscopy (PES)) study of water interaction with the two-dimensional titania overlayer that terminates the SrTiO3(110)-(4 × 1) surface and consists of TiO4 tetrahedra. STM and core-level and valence band PES show that H2O neither adsorbs nor dissociates on the stoichiometric surface at room temperature, whereas it does dissociate at oxygen vacancies. This is in agreement with DFT calculations, which show that the energy barriers for water dissociation on the stoichiometric and reduced surfaces are 1.7 and 0.9 eV, respectively. We propose that water weakly adsorbs on two-dimensional, tetrahedrally coordinated overlayers.