Ternary Ti Si Research Articles

Prediction of thermodynamic and surface properties of ternary Ti–Si–Fe liquid alloy

Thermodynamic and surface properties of the ternary Ti–Si–Fe liquid alloy have been assessed at temperatures 1873 K, 1973 K, 2073 K and 2173 K. For this purpose, the optimized linear temperature dependent coefficients of Redlich–Kister (R–K) polynomials for excess free energy of mixing for sub-binary systems Ti–Si, Fe–Si and Ti–Fe have been computed considering available experimental and literature data. The thermodynamic properties of ternary liquid alloy, such as activity have been studied using general solution model (GSM) and excess free energy of mixing has been studied using GSM, Kohler and Toop models. In surface properties, surface concentration has been computed using Butler’s equation and surface tension of the liquid alloy has been studied using all the four above mentioned models feeding the database of liquid Fe–Si, Si–Ti and Ti–Fe sub-binary systems. The values of surface tension computed using GSM and Toop model are in well agreement with each other at all concentrations. Moreover, the computed values of excess free energy of mixing and surface tension decrease at elevated temperatures from all corners and at all considered cross-sections indicating the decrease in ordering tendency of the alloy.

Effect of High-Temperature Deformation on the Physical and Mechanical Properties of In Situ Titanium Composites with Silicide–Boride Reinforcement

The efficiency of thermomechanical processing was studied to optimize the mechanical properties of cast ternary and multicomponent hypoeutectic titanium-based alloys with silicide–boride reinforcement, produced by electron-beam crucible-skull melting. All the alloys studied exhibit low plasticity in cast state. High-temperature deformation, such as forging of samples heated to 1050°C in air, can significantly enhance the properties of the alloys: the plasticity of ternary Ti–Si–B alloys increases by four to six times (from 0.5 to 2–3%) and their fracture toughness increases by three times (from 11 to 36 MPa ∙ m0.5). The plasticity of the alloys with Zr, Al, and Sn additions increases by one order of magnitude (to 0.2–0.3%) and their fracture toughness by almost twice. The greatest high-temperature creep-rupture resistance at a fracture toughness of 26 MPa ∙ m0.5 is shown by the Ti80Zr1.2Al5.5Sn2.1Si8.7B2.5 alloy: 1038, 887, and 572 MPa at 600, 700, and 800°C, respectively.

Morphological changes of the PVD coatings after isothermal annealing

The main of this work is to investigate the impact of the isothermal annealing on the structure and morphological changes on the PVD hard coatings. Three different coatings based on the AlTiN system were deposited onto cemented carbide substrates containing 6 wt% of Co. Two coatings AlTiN/TiAlN and AlTiN/TiN with an initial thickness of 3 μm has a coarse-grained columnar structure with a chemically graded nanomultilayering consisting of alternating Ti-rich and Al-rich layers. In the case of the AlTiN/TiAlN coating, a total of 20 layers were applied. Ten layers had a thickness of 200 nm (AlTiN) and 10 layers with the thickness of 100 nm (TiAlN). The same number of nanolayers was also retained for the AlTiN/TiN multilayer coating. The TiN layers were 100 nm thick. The third coating was a nanocomposite sandwich coating formed by a TiSiN adhesive layer (50nm), a functional nanocomposite AlTiSiN layer (2 μm) and a top functional TiSiN layer with a thickness of 1 μm. The coatings were prepared by cathodic arc evaporation using the LARC® technology. After deposition, the samples were annealed at high temperatures (700 °C, 800 °C, 900 °C, 1000 °C) for one hour in air. With X-ray diffraction and scanning electron microscopy, the morphology, structure and phase composition of coatings and oxide layers after annealing were evaluated.After the heat-treatment at 800 °C, cross-sectional and surface morphology images revealed, that an oxide layer has grown on top of the all coatings. EDS analysis showed that the oxide layers on the multilayers coatings had a layered structure, which was found to be the consequence of the high diffusion rate of Al. The interface with the coatings was very rough. It was depleted of Al, which diffused to the upper surface of the oxide. The oxidation process of nanocomposite AlTiSiN/TiSiN coating started by forming an oxide layer of ternary Ti–Si–O at the interface. This system segregated into two phases of TiO2 and SiO2. The nanocomposite coating remained stable even after annealing at 1000 °C. The surface of the multilayers was accompanied by a network of cracks at this temperature. An interesting phenomenon was also observed on the substrates itself during the annealing. As a result of oxidation, unprotected sides of the substrates expanded. Globular oxides based on tungsten and cobalt were also formed on the surface of the samples at the places where the coating was peeled off. The reasons for the differences are discussed.

Microstructures and mechanical properties of ternary Ti–Si–Sn alloys

Titanium based alloys are one of the important structural materials with applications ranging from aerospace to biomedical industries. Several ternary Ti–Si–Sn alloys were explored in this study to design the microstructure comprising of binary and ternary eutectics corresponding to Ti–Si, Ti–Sn and Ti–Si–Sn system. The microstructural evolution in these alloys was studied using a combination of characterization techniques and thermodynamic calculations. The predicted solidification path from thermodynamic calculations well supported the experimental microstructural data. In addition, mechanical property and microstructure relationship were determined by performing hardness measurements and evaluating stress-strain curves under compression.

Ternary Ti–Si–C alloy film formation on GaN and contact properties

Ternary Ti–Si–C alloy films were deposited on GaN substrates (n-type and p-type) by the radio- frequency magnetron sputtering method. The electrical properties of contact films with various chemical compositions were investigated. The microstructures were examined by X-ray diffractometry and transmission electron microscopy. The electrical properties of the contact films were improved after annealing at 873 K for 60 s. Ohmic contact characteristics were obtained for n-type GaN. The TiN phase plays an important role in obtaining the ohmic contact. The effect of deposition and annealing on the electrical properties between Ti–Si–C film and GaN are discussed based on the experimental results.

Vascular endothelial cell compatibility of superhard ternary Ti–Si–N coatings with different Si contents

Superhard ternary Ti–Si–N coatings with different Si atomic concentrations are deposited on titanium alloy substrates by arc-enhanced magnetron sputtering (AEMS) and the vascular endothelial cell compatibility is studied. In vitro studies show that the surface hydrophilicity and hemolysis are about the same as those of the titanium alloy control and platelet adhesion and protein adsorption tests suggest a close relationship between the surface energy and blood compatibility. Endothelial cells cultures reveal better proliferation and anti-platelet adhesion on the coatings compared to the titanium alloy control and the Ti–Si–N coating with 20 at% Si exhibits excellent endothelialization.

Microstructure and mechanical properties of Ti–Si–C–N coatings deposited by hybrid arc enhanced magnetron sputtering

Quaternary Ti–Si–C–N coatings have been deposited on high speed steel substrates using a new hybrid arc enhanced magnetron sputtering (AEMS) technique conducted at low temperature. The microstructure and mechanical properties of the deposited Ti–Si–C–N coatings are investigated and the results show that the Ti–Si–C–N coatings have a nanocomposite microstructure consisting of nanosized TiN and TiC crystallites embedded in an amorphous phase of Si3N4/C. The hardness of the Ti–Si–C–N coatings increases linearly from 20 to 35 GPa with carbon incorporation up to 35 at.-% and the friction coefficient is below 0·25 which is smaller than that of ternary Ti–Si–N nanocomposite coatings.

High-temperature property of carbon/carbon composite joints bonded with ternary Ti–Si–C compound

Carbon/carbon composites were joined using Ti–Si–C compound as interlayer and high-temperature shear strength and thermal shock resistance of these joints were investigated in this paper. In order to improve thermal shock resistance of the joints, a SiC transition layer was introduced between carbon/carbon substrates and interlayer. Microstructures and phase composition of the as-received joints were characterized by electron backscattered diffraction and X-ray diffraction. Mechanical strength and thermal shock resistance of the joints were measured by high-temperature shear test and thermal cycle test, respectively. The shear test results show that, with test temperature increasing from 273 K to 1673 K, shear strength of joints gradually increases to a maximum value of 46 MPa at 1473 K, then drops suddenly at higher temperature. Joints with SiC transition layer exhibit better thermal shock resistance than the ones without SiC transition layer and strength retention can be kept up to 85%, even after 30 thermal cycles from 1673 K to room temperature.

On the spinodal nature of the phase segregation and formation of stable nanostructure in the Ti–Si–N system

The free energy of the mixed Ti–Si–N system is calculated according to a semi-empirical thermodynamic formula based on the sub-lattice model for different activities of nitrogen. The results show that the phase segregation in the ternary Ti–Si–N systems is of chemically spinodal nature at a nitrogen pressure and deposition temperature typically used for the deposition of the superhard nc-TiN/a-Si 3N 4 nanocomposites, i.e. p N 2 ≥ 10 − 3 mbar and T dep 550–600 °C, respectively. Only at much lower nitrogen pressure and much higher temperature, can the chemically spinodal decomposition be restrained. A simple estimate of the interfacial strain energy for a semi-coherent interface, as expected for this system, shows that this contribution is unlikely to hinder the system being also coherently spinodal. It is further shown that kinetic constraints, such as T dep ≤ 300 °C and low p N 2 , although within the range where the stoichiometric nitrides should be fully spinodally segregated, will kinetically hinder the system to reach the thermodynamically driven equilibrium.

Copper diffusion in Ti–Si–N layers formed by inductively coupled plasma implantation

Ternary Ti–Si–N refractory barrier films of 15nm thick was prepared by low frequency, high density, inductively coupled plasma implantation of N into TixSiy substrate. This leads to the formation of Ti–N and Si–N compounds in the ternary film. Diffusion of copper in the barrier layer after annealing treatment at various temperatures was investigated using time-of-flight secondary ion mass spectrometer (ToF-SIMS) depth profiling, X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and sheet resistance measurement. The current study found that barrier failure did not occur until 650°C annealing for 30min. The failure occurs by the diffusion of copper into the Ti–Si–N film to form Cu–Ti and Cu–N compounds. FESEM surface morphology and EDX show that copper compounds were formed on the ridge areas of the Ti–Si–N film. The sheet resistance verifies the diffusion of Cu into the Ti–Si–N film; there is a sudden drop in the resistance with Cu compound formation. This finding provides a simple and effective method of monitoring Cu diffusion in TiN-based diffusion barriers.

Effects of Si content and free Si on oxidation behavior of Ti–Si–N coating layers

In this work, various Ti–Si–N coating layers, composites of TiN crystallites and amorphous Si 3N 4, where free Si existed depending on the amount of total Si content in Ti–Si–N film, were prepared on Si substrates by a d.c. reactive magnetron sputtering method in order to systematically investigate the effects of Si contents and free Si on the oxidation behavior. The oxidation process at 800 °C started by forming thin oxide layer of ternary Ti–Si–O at the interface, and the ternary Ti–Si–O layer was segregated into two phases of TiO 2 and SiO 2. Oxidation resistance of Ti–Si–N coating layers was significantly improved with increasing Si contents, which resulted in the increase of SiO 2 amount acting as an oxygen diffusion barrier. Free Si was diffused and segregated toward surface region, while Si bonded to nitrogen in Si 3N 4 could not. The free Si in Ti–Si–N coating layers was believed to partly contribute to the much enhanced oxidation resistance.

Low temperature metal-organic chemical vapor deposition of advanced barrier layers for the microelectronics industry

Metal-organic chemical vapor deposition (MOCVD) of TiN thin films at low temperatures and low pressures using tetrakis(diethylamino) Ti (TDEAT) and NH 3 is described. Conformal TiN films, having layer resistivities of less than 200 μΩcm, densities close to those in sputtered films and low impurity contents can be obtained with this chemistry. These TiN films can be applied as adhesion layers for chemically vapor-deposited W, or as barrier layers between Si and Al. Many papers describe deposition of TiN using tetrakis (dimethylamino) Ti (TDMAT) and NH 3 to form TiN, presumably because of the conveniently higher vapor pressure of TDMAT compared with TDEAT. A direct liquid injection system is used here to enable reproducible introduction of both amines in the reactor. A direct comparison between the TDMATNH 3 and TDEATNH 3 chemistries and the properties of the resulting films is made. It is found that the more reactive TDMATNH 3 chemistry produces non-conformal films having a higher resistivity (>1200 micro ohm cm) and lower density. finally, MOCVD of advanced amorphous barrier materials, comprising a ternary TiSiN alloy, is described. Such amorphous ternary barriers are candidates for application in future Cu metallization schemes.