Carbide Ti Research Articles

Effects of titanium addition on microstructure and wear resistance of hypereutectic high chromium cast iron Fe–25wt.%Cr–4wt.%C

A finer microstructure generally helps to increase the wear resistance of materials. It was reported that Ti could act as an inoculant to generate fine microstructure for white cast iron, one of widely used in industrial materials. To confirm this, we investigated influences of Ti addition (up to 6 wt.%) on microstructure of a hypereutectic high chromium cast iron (Fe–25wt.%Cr–4wt.%C). Ingot samples were prepared using an arc furnace by melting pieces of the cast iron with titanium powder. Microstructures of the samples were examined by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray diffraction. It was demonstrated that the added titanium did not act as an inoculant to reduce the size of coarse primary carbides. Instead, as the titanium amount was increased, the cast iron changed from a hypereutectic microstructure to a hypoeutectic one due to the depletion of carbon that was consumed by Ti to form titanium carbides. When 2 wt.% Ti was added, the finest microstructure was achieved, which corresponded to the eutectic structure with mixed chromium carbides and titanium carbides. The eutectic structure exhibited the highest wear resistance and hardness due to the refined microstructure as well as the fact that an amount of chromium carbides were replaced by Ti carbides, which are harder than the former.

Corrosion Behavior of Layered Ternary Carbide Ti<SUB>2</SUB>AlC in Acidic Solution

Corrosion Behavior of Layered Ternary Carbide Ti<SUB>2</SUB>AlC in Acidic Solution

Reaction synthesis of layered ternary Ti 2AlC ceramic

Reactive sintering of 8Ti:Al 4C 3:C powder mixtures to form the ternary carbide Ti 2AlC is studied in the temperature range 570–1400 °C. After sintering at 1400 °C for 1 h, only the MAX phase Ti 2AlC and some TiC are produced. A series of intermediate phases, such as TiC, Ti 3Al, Ti 3AlC are detected during the reactive sintering process. From X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterizations, a reaction path is proposed for the intermediate phases and Ti 2AlC formation. Results show that reaction kinetics may play an important role in the understanding of the reaction mechanisms.

Low-temperature synthesis of high-purity Ti 3AlC 2 by MA-SPS technique

Ternary carbide Ti 3AlC 2 was synthesized by mechanical alloying (MA) and spark plasma sintering (SPS) from elemental powder mixtures of Ti, Al and C, and the effect of Al content on formation of Ti 3AlC 2 during both processes was investigated. The results showed that adding proper Al content in the staring materials significantly increased the phase purity of Ti 3AlC 2 in the synthesized samples. Dense and high-purity Ti 3AlC 2 with <1 wt.% TiC could be successfully obtained by spark plasma sintering of powders mechanically alloyed for 9.5 h from a starting powder mixtures of 3Ti/1.1Al/2C at a lower sintering temperature of 1050 °C for 10–20 min.

Effects of using Al 4C 3 as a reactant on formation of Ti 3AlC 2 by combustion synthesis in SHS mode

Preparation of the ternary carbide Ti 3AlC 2 was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) from both the elemental powder compacts of Ti:Al:C = 3:1:2 and the Al 4C 3-containing samples compressed from the powder mixtures of Ti/Al/C/Al 4C 3 with Al 4C 3 content ranging from 1.85 to 5.56 mol%. The reactant compact with 5.56 mol% Al 4C 3 represents a composition of 3Ti + 1.25C + 0.25Al 4C 3, within which Al 4C 3 serves as the only source of Al. Effects of the Al 4C 3 addition and sample green density were studied on the combustion characteristics and product compositions. Due to formation of liquid Ti–Al melt and growth of the Ti 3AlC 2 grains, the powder compact was subjected to substantial deformation during the SHS process. With an increase in the Al 4C 3 content, the reaction temperature and flame-front propagation velocity were reduced, but the degree of Ti 3AlC 2 formation was improved. In addition to Ti 3AlC 2 formed as the dominant phase, the XRD analysis identified two secondary phases TiC and Ti 2AlC in the synthesized products. Formation of Ti 3AlC 2 was also enhanced by increasing the sample green density. For the elemental powder compacts, the content of Ti 3AlC 2 yielded in the products increased from 50.5 to 73.2 wt% with increasing sample density from 45 to 65% TMD. It was found that under a constant compaction density of 60% TMD, the product composed of 75.3 wt% Ti 3AlC 2 was produced from the 5.56 mol% Al 4C 3-containing sample, in comparison with only 61 wt% Ti 3AlC 2 from the elemental reactant. Moreover, as the sample density further increased to 70% TMD, the yield of Ti 3AlC 2 approaching 80 wt% was obtained.

Synthesis of Ti 3AlC 2 by spark plasma sintering of mechanically milled 3Ti/ xAl/2C powder mixtures

Elemental powders of Ti, Al and C were mechanically milled as starting materials for the fabrication of ternary carbide Ti 3AlC 2 by spark plasma sintering (SPS) technique. The effect of Al content in the starting materials on the Ti 3AlC 2 synthesis was investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to determine the phase identification and observe the microstructure of the synthesized samples. With increasing proper Al content, it was found that the purity of Ti 3AlC 2 increased and the sintering temperature reduced. The dense and high-purity Ti 3AlC 2 could be successfully fabricated from 3Ti/1.2Al/2C powders at a lower sintering temperature of 1050 °C, holding for 10 min. In addition, the reaction path for the formation of Ti 3AlC 2 in the present study was proposed.

Formation and stability of di-transition-metal carbides Ti xZr 1−xC, Ti xHf 1−xC and Hf xZr 1−xC

We have carried out the first-principles total energy calculations, using the pseudopotential plane-waves approach based on density functional theory, within the generalized gradient approximation (GGA) for the exchange and correlation potential, to investigate the formation and stability of di-transition-metal carbides. We report total energy calculations for Ti x Zr 1− x C, Ti x Hf 1− x C, and Hf x Zr 1− x C crystal structure over a range of composition x and we present a description of formation energies, stability and elastic properties. Our results for elastic stiffness coefficients and equilibrium volume as well as their dependence on composition were compared with experimental data and previous calculations.

Effects of TiC and Al4C3 addition on combustion synthesis of Ti2AlC

Preparation of the ternary carbide Ti 2 AlC was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) from the elemental powder compacts of Ti:Al:C = 2:1:1, TiC-containing samples with TiC of 6.67–14.3 mol%, and Al 4 C 3 -containing samples with Al 4 C 3 of 1.96–10 mol%. Effects of TiC and Al 4 C 3 addition were studied on combustion characteristics and the degree of phase conversion. Due to the growth of laminated Ti 2 AlC grains, the reactant compact was subjected to an axial elongation during the SHS process. Because the addition of TiC and Al 4 C 3 led to a decrease in the reaction temperature, the flame-front propagation velocity was correspondingly reduced for the TiC- and Al 4 C 3 -containing samples when compared with the elemental reactants. Based upon the XRD analysis, formation of Ti 2 AlC along with a secondary phase TiC was identified in the synthesized products. The grains of Ti 2 AlC are typically plate-like with a size of 10–20 μm and several laminated Ti 2 AlC grains form a layered structure. The content of Ti 2 AlC yielded from the elemental powder compacts is about 85 wt%. The addition of TiC was found to facilitate the formation mechanism and therefore to enhance the extent of Ti 2 AlC conversion approaching 90 wt%. As a result of the reduced exothermicity of the reaction, however, the content of Ti 2 AlC decreased slightly in the products synthesized from the Al 4 C 3 -added samples.

The Influence of Temperature on Cr-Ti Coating in Carbon Steel

It is considered that Ti-Cr coatings can improve strength, hardness, wear resistance and corrosion resistance of base control alloys as these coatings combine the advantages of both Ti coating and Cr coating. In this study, the Ti-Cr coatings were deposited by diffusion method. The effects of deposition temperatures on the compositions and microstructures of the Ti-Cr coatings on 45# carbon steel were investigated. The coatings formed consisted of three layers. The outer layer contained Ti and Cr carbides beneath which a diffusion layer was developed. The inner layer was enriched in Ti and Cr. At low temperature (800°C) the outer layer of Ti-Cr coatings was dominated by TiC. Increasing deposition temperature led to the enhanced diffusion of Cr and a Cr7C3 and Cr23C6-dominated outer layer was identified. The growth process of Ti-Cr coating was analyzed and simulated.

Synthesis of Ti 3AlC 2 ceramic by high-energy ball milling of elemental powders of Ti, Al and C

Synthesis of the ternary carbide Ti 3AlC 2 by high-energy ball milling of elemental Ti, Al and C powders with a stoichiometric composition was tentatively investigated. The results show that high content Ti 3AlC 2 was successfully obtained after ball milling of powder mixture only for 3 h. The milled products consist of powder and a coarse granule with 8 mm in diameter, and both are mainly composed of Ti 3AlC 2 with TiC as impurity based on X-ray diffractometer (XRD) and energy-dispersive spectroscopy (EDS) characterization. It is believed that a mechanically induced self-propagating reaction (MSR) was triggered to form Ti 3AlC 2 and TiC during high-energy ball milling process.

Oxide and Carbide Formation at Titanium/Organic Monolayer Interfaces

X-ray photoelectron spectra (XPS) are reported from a series of buried titanium/organic monolayer interfaces accessed through sample delamination in ultrahigh vacuum (UHV). Conventional characterization of such buried interfaces requires ion-mill depth profiling, an energetic process that frequently destroys bonding information by chemically reducing the milled material. In contrast, we show that delaminating the samples at the metal/organic interface in vacuum yields sharp, nonreduced spectra that allow quantitative analysis of the buried interface chemistry. Using this UHV delamination XPS, we examine titanium vapor deposited onto a C18 cadmium stearate Langmuir-Blodgett monolayer supported on Au, SiO2, or PtO2 substrates. Titanium is widely used as an adhesion layer in organic thick film metallization as well as a top metal contact for molecular monolayer junctions, where it has been assumed to form a few-atoms-thick Ti carbide overlayer. We establish here that under many conditions the titanium instead forms a few-nanometers-thick Ti oxide overlayer. Both TiO2 and reduced TiOx species exist, with the relative proportion depending on oxygen availability. Oxygen is gettered during deposition from the ambient, from the organic film, and remarkably, from the substrate itself, producing substrate-dependent amounts of Ti oxide and Ti carbide "damage". On Au substrates, up to 20% of the molecular-monolayer carbon formed titanium carbide, SiO2 substrates approximately 15%, and PtO2 substrates <5%. Titanium oxide formation is also strongly dependent on the deposition rate and chamber pressure.

Combustion synthesis of Ti3AlC2 from Ti/Al/C/TiC powder compacts

Abstract Preparation of the ternary carbide Ti 3 AlC 2 was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) from both the elemental powder compacts of Ti:Al:C = 3:1:2 and the TiC-containing samples compressed from the powder mixtures of Ti/Al/C/TiC with TiC content ranging from 4.35 to 26.3 mol%. The effect of TiC addition was studied on combustion characteristics and the degree of phase conversion. For the elemental reactants, the powder compact experiences substantial deformation during the SHS process, including axial elongation and radial contraction. Because the addition of TiC lowered the reaction temperature, the extent of sample deformation and flame-front propagation velocity were considerably reduced for the TiC-containing samples. Based upon the XRD analysis, formation of Ti 3 AlC 2 along with two secondary phases TiC and Ti 2 AlC was identified in the synthesized products. The grains of Ti 3 AlC 2 are typically plate-like with a size of 5–10 μm. The content of Ti 3 AlC 2 yielded increases with sample green density for the elemental powder compacts, resulting in the mass fraction of Ti 3 AlC 2 increasing from 50.5 to 73.2% in the products with respect to the increase of relative density of the sample from 45 to 65%. The improvement in formation of Ti 3 AlC 2 was also made by properly adding TiC in the reactant compact. An optimal conversion yielding a product with mole fractions of 84.6% Ti 3 AlC 2 , 9.8% TiC, and 5.6% Ti 2 AlC was achieved by the sample composed initially of 20 mol% TiC. However, further increase of the TiC amount led to a decrease in the Ti 3 AlC 2 content, because of reduced exothermicity of the reaction.

Effect of Reheating and End Cooling Temperature on Microstructure Refinement in a Low Carbon High Strength Nb-Ti Microalloyed Dual Phase Steel

In this study, a TMCP was attempted to obtain a low carbon high strength Nb-Ti microalloyed dual phase with low yield ratio at Baosteel. Optical and scanning electron microscopy was utilized to analyze microstructures. A mixed fine microstructures consisting of acicular ferrite and martensite/austenite was observed. The austenite maintained a small grain size during reheating in the temperatures ranging from 1100°C to 1250°C. The growth of austenite was strongly retarded by Nb and Ti nitride and carbide. The higher end cooling temperature (650°C) had much influence on the refinement of microstructures, especially the length of ferrite packets, whereas the lower temperatures (600-500°C) had little effect on the microstructure refinement.

Improvement of the Reverse Characteristics of Ti/4H-SiC Schottky Barrier Diodes by Thermal Treatments

Ti/4H-SiC Schottky barrier diodes were fabricated under 500, 750, 1000 °C thermal treatment conditions. After the heat treatment at 750 °C, formation of TiC(111) and Ti5Si3(210) phases was confirmed by XRD analysis. Formation of Ti carbide and silicide phase increased breakdown voltage VB from 545 V to 830 V. An improvement of breakdown voltage (VB) was observed in case of the thermal treatment in nitrogen ambient at 750 °C for 2 min. Ideality factor (n), specific on resistance (Ron), and Schottky barrier height (Φb) were 1.04, 2.7 m-cm2, 1.33 eV respectively.

Tin–Transition Metal–Carbon Systems for Lithium-Ion Battery Negative Electrodes

Magnetron cosputter deposited ternary libraries of (, V and Co) ( and ) have been studied structurally and electrochemically using combinatorial and high-throughput methods. Each of the sputtered binary systems shows an amorphous composition range where the specific capacity for lithium decreases with M content. Adding carbon to the amorphous binaries, to make ternaries, causes the precipitation of crystalline Sn in the cases when or V, but not when . We believe this is because stable carbides of Ti and V exist but stable Co carbides do not. The sputtered system was found to have a large amorphous range and the initial amorphous atomic arrangement in certain compositions are stable over at least 27 charge-discharge cycles of . Crystalline Sn was found to precipitate in composition ranges having competitive specific capacity in the and libraries causing rearrangement of the atoms during cycling leading to poor capacity retention.

Fabrication of high-purity ternary carbide Ti 3AlC 2 by spark plasma sintering (SPS) technique

The effect of silicon on synthesis of Ti 3AlC 2 by spark plasma sintering (SPS) from TiC/Ti/Al powders was investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for phase identification and microstructure evaluation. The results showed that addition of silicon can considerably accelerate the synthesis reaction of Ti 3AlC 2 and fully dense, essentially single-phase polycrystalline Ti 3AlC 2 could be successfully obtained by sintering 2TiC/1Ti/1Al/0.2Si powders at 1200–1250 °C under a pressure of 30 MPa. SEM micrographs showed the obtained Ti 3AlC 2 samples to be about 2–5 μm thick and 10–25 μm long platelets. The fracture toughness and flexural strength of Ti 3AlC 2 were 7.0 ± 0.2 MPa m 1/2 and 450 ± 10 MPa, respectively.

Characterization of activated non-evaporable porous Ti and Ti–Zr–V getter films by synchrotron radiation photoemission spectroscopy

Highly porous Ti and TiZrV film getters on (100) silicon substrates, grown by the glancing angle deposition of dc magnetron sputtering method, were used to study the activation process. The effect of activation temperature on the reducing degree of the porous Ti and TiZrV films were investigated by synchrotron radiation photoemission spectroscopy (SRPES). Elemental carbon absorbed on the surface of the Ti film, exposed in air, will be transformed to a Ti carbide phase, however, that which is on the surface of the TiZrV film will be completely removed by heat at 250 °C or above. The oxidized Ti in a porous TiZrV film is more easily reduced than that in the porous Ti films. The breakdown of V–O and Ti–O bonds on the TiZrV film surface is easier than that of the Zr–O bond. We suggest that the decrease of reducing temperature of oxidized TiZrV, comparing with that of oxidized Ti, is caused by the displacement reaction of Zr on oxidized Ti or oxidized V.

Surface cleaning of a commercially pure Ti, Ti6Al4V and Ti3Al8V6Cr4Zr4Mo alloys by linear heating

AbstractThe surfaces of Ti and its alloys are always contaminated by O and C due to the continual uptake of the background gases, even in an ultra high vacuum (UHV) chamber. The surfaces of Ti and its alloys (Ti6Al4V and Ti3Al8V6Cr4Zr4Mo) were cleaned by annealing the sample linearly to a temperature higher than 600 °C and then cooled. The segregation of S was only observed after the samples were heated to temperatures above 550 °C. The segregation of S was only measured after most of surface adsorbate elements were removed from the surface. The three samples' surfaces (Ti, Ti6Al4V and Ti3Al8V6Cr4Zr4Mo) were all almost clean or free of contamination in the temperature range 600–650 °C. The addition of the alloying elements impacts the retention of O and C on the surfaces. The linear least square (LLS) fit method was used to determine the contributions of pure Ti, Ti oxide and Ti carbide from the measured Auger peak to peak heights (APPHs). AES peak fitting was done and confirmed the formation of TiC and TiO on the surface at temperatures between 100 °C and 500 °C. The segregation of Al in the Ti6Al4V and Ti3Al8V6Cr4Zr4Mo samples was measured at higher temperatures. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Tribological behavior of Ti 2SnC particulate reinforced copper matrix composites

The layered ternary carbide Ti 2SnC has outstanding mechanical and electrical properties. Therefore, the Cu matrix composite reinforced by Ti 2SnC expects combined merits of both materials. In this article, we synthesized the copper matrix composites reinforced by Ti 2SnC ceramic particles using hot-pressing method. The tribological behaviors of pure copper and composites reinforced with Ti 2SnC were studied on a block-on-ring tester. The blocks were slid against 52100 steel rings under dry ambient conditions. It showed that the friction coefficient and wear rate of Cu matrix composites decreased significantly by incorporation of Ti 2SnC particles. The wear rate of pure copper was about eight times that of the Cu–10 vol.% Ti 2SnC composite under a sliding velocity of 20 m min −1 and a normal load of 30 N. The satisfied low friction coefficient and wear resistance prove that Ti 2SnC is a promising reinforcement material for Cu matrix composite. In addition, the effects of sliding velocity and normal load on wear behavior were investigated for pure copper and Cu–Ti 2SnC composites.

Synthesis of Ti 3SiC 2 from powder blend of Ti, Si and TiC

Titanium silicon carbide Ti 3SiC 2 was synthesized from a powder blend of Ti, Si and TiC at a molar ratio of Ti:Si:TiC = 2:2:3. The powder blend was pressed and shaped into a cylinder and then sintered at various temperatures in vacuum. X-ray diffraction analysis was conducted on the cylinders sintered at various temperatures. Results of the XRD analysis revealed that Ti 5Si 3, the most thermodynamically stable phase in Ti–Si system, was preferentially formed by the reaction between Ti and Si powders followed by the formation of TiSi 2 from remaining Ti and Si powders in a relatively low temperature range. These silicides reacted with TiC to form Ti 3SiC 2 at higher temperatures. The final phases in the cylinders sintered at temperatures over 1729 K were Ti 3SiC 2 and Ti 5Si 3, which well agrees with those estimated by a Ti–Si–C phase diagram. On the other hand, final phases in disks sintered under pressures of 14 MPa or more by using a carbon mold were found to be Ti 3SiC 2 and TiC, which suggests the equilibrium changes with the pressure.