Titanium Atoms Research Articles

Phase compatibility in (WC-W2C)/AlFeCoNiCrTi composite produced by spark plasma sintering

Thermodynamic, kinetic as well as thermal compatibilities of the phases of (WC-W2C)/10 wt% AlFeCoNiCrTi composite were studied. The thermodynamic compatibility of the composite constituents was evaluated by spark plasma sintering at different temperatures (1200–1500 °С). It was found that the diffusion layer of (Fe, Co, Ni, Cr)xWyCz phase formed after sintering at 1200–1300 °С, while at temperatures of 1400–1500 °С, the complex carbide is additionally saturated with titanium atoms forming (Fe, Co, Ni, Cr, Ti)xWyCz phase. The controlled processes of kinetic interaction between composite phases occur during the annealing of the samples at 1100 °C for 30, 60, and 120 min. The limited solubility and time-controlled diffusion processes indicate the thermodynamic and kinetic compatibilities of the phases in (WC-W2C)/10 wt% AlFeCoNiCrTi composite. Whereas, uncontrolled chemical interactions occur at the interfaces during the liquid phase sintering at temperatures higher than 1300 °C, indicating unsatisfactory thermodynamic compatibility between the components. The thermal compatibility was evaluated by measuring the CTE of AlFeCoNiCrTi and WC-W2C, which was found to be 12 × 10−6 K−1 and ~ 9.5 × 10−6 K−1, respectively.

Langmuir-Blodgett monolayer of electrochemically synthesized PANI-TiO2 nanocomposites for MSG biosensor

Nanocomposites of polyaniline titanium oxide (PANI-TiO2) have been synthesized by employing the electrochemical technique and their monolayers were prepared on a pre-chemical treated indium tin oxide (ITO) surface through Langmuir-Blodgett (LB) process. The TEM images show the well dispersion of an average ∼ 5 nm diameter TiO2 particles in the film of PANI-TiO2 with ∼ 0.35 nm interatomic spacing of titanium atoms in the anatase crystalline plane (101). X-ray photoelectron (XPS) spectra of LB film of PANI-TiO2 also confirmed the presence of Ti atoms as a similar observation was also confirmed in energy dispersive X-ray analysis (EDX) analysis of the film surface. Electrochemical conductivity of the PANI-TiO2 LB films showed enhancement in peak current, and subsequent immobilization of monoclonal antibodies specific to l-glutamic acid was achieved. Differential pulse voltammetry (DPV) measurements showed a linear response in the peak current with MSG concentration varying from 1 nM to 500 µM and 1 µM to 250 µM in the electrolyte and tomato sauce, respectively. The detection sensitivity of the immunosensor was ∼ 37 mA/nM.

Remarkable Structural Modifications of Tialite Solid Solutions Obtained by Different Methods.

The structural changes occurring in tialite due to the formation of magnesium-titanate–aluminum-titanate solid solutions were determined. For this purpose, a DFT simulation of the structural changes was performed. The simulation proposed a number of possible atomic substitutions occurring in the elementary cells of the tialite, along with calculations of the lattice parameter changes in this material. Next, the actual changes occurring in the structure of the tialite due to the formation of solid solutions, obtained in different ways, were investigated. After comparing the obtained results, it was possible to confirm the mechanism of the formation of tialite solid solutions, through which one magnesium atom and one titanium atom substituted two aluminum atoms simultaneously. The results of this experimental work were confirmed by theoretical calculations (the differences in the values of the lattice parameters, measured in the experiment and calculated in the simulation, were less than 0.5%), through which changes in the lattice parameters with Mg and Ti substitution were observed.

Molecular Adsorption of H2O on TiO2 and TiO2:Y Surfaces

In this work, using theoretical calculations within the framework of the density functional theory, taking into account the dispersive VDW interaction, the processes of adsorption and interaction of a water molecule with a TiO2 surface in various configurations are investigated. At the atomic / molecular level, the interactions of a water molecule with a TiO2 surface have been studied for various orientations. The results of calculations within the framework of DFT + VDW show that the adsorption energies of single water molecules in different initial positions on the substrate surface vary from -0.72 to -0.84 eV, and the most stable adsorbate structure is the TiO2 + H2O system upon adsorption of a molecule of water, parallel to the Y axis, because during the adsorption of H2O parallel to the Y axis, some favorable effects are observed in the band structure of titanium dioxide. On the one hand, the band gap decreases to 2.59 eV, and on the other hand, a new energy state appears in the band gap with an energy contribution of 0.17 eV, when water is physisorbed and interacts with a titanium atom at a distance of 2.12 Å and occupies a perpendicular position relative to the surface. Doi: 10.28991/HEF-2022-03-02-07 Full Text: PDF

Novel insights on the near atomic scale spatial distributions of substitutional alloying and interstitial impurity elements in Ti-6Al-4V alloy

The present study explores the near atomic scale spatial distributions of substitutional alloying elements (aluminium and vanadium) and interstitial impurities (oxygen and carbon) in the microstructures of Ti-6Al-4V and its boron modified counterpart (Ti-6Al-4V-0.1B) alloys using transmission electron microscopy (TEM) and atom probe tomography (APT) techniques. The latter alloy possesses zero solubility of boron in α-Ti and high oxygen concentration around TiB particles. The results suggest that aluminium and vanadium atoms enrich α and β phases, respectively due to strong elemental partitioning between these phases, to an extent that the atomic scale concentrations of various elements considerably differ from the bulk compositions of the two alloys. Furthermore, oxygen atoms are preferentially distributed within the α phase where other interstitial impurities (carbon) also segregate. Substitutional aluminium atoms share an inverse interrelation with interstitial oxygen atoms while vanadium atoms reside besides the impurity-rich regions for both the alloys. The size differences for these elements (substitutional vs. interstitial) with host titanium atoms and related lattice distortion is (partially) held responsible for the atomic scale elemental distributions and the observed interrelations within the α phase. These arguments are further substantiated from DFT results previously obtained for Ti-6Al-4V alloy.

Crystallization properties and structural evolution of amorphous Ti-doped Sn20Sb80 thin layers induced by heating and irradiating

Sb-rich Sn20Sb80 thin layers with different titanium components were comprehensively investigated in terms of the crystallization properties and structural characterization. The phase transition behaviors induced by heating and irradiating were obtained from in situ resistance and reflectivity measurement. After doping the titanium element, the phase transformation temperature and resistance enhance remarkably, meaning the better thermal stability and lower energy consumption of the Sn20Sb80 material. The structural analyses were characterized by x-ray diffraction, transmission electron microscopy, and Raman spectroscopy, respectively, proving that the foreign titanium atoms can block the crystallization process and reduce the grain size. All the results illustrate that doping suitable titanium will be a desirable technique to regulate the crystallization properties of the Sn20Sb80 material.

Influence of the carbon incorporation on the mechanical properties of TiB2 thin films prepared by HiPIMS

Nanostructured TiB2 and TiBC thin films with carbon contents up to 11 at. % were prepared by physical vapor deposition using high power impulse magnetron sputtering (HiPIMS) technology. The influence of carbon incorporation during the deposition of TiB2 coatings was investigated on the chemical composition, microstructure and mechanical properties by means of scanning electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), nanoindentation, scratch test, calotest and adhesion Daimler-Benz test. The results indicated that small additions of carbon up to 3 at. % improved the mechanical behavior and increased the adhesion of the TiB2 thin films. Hardnesses up to 37 GPa were reached and the adhesion of the coating to AISI D2 steel substrates increased from 11 to 18 N. XRD and XPS results showed that the carbon atoms are either occupying interstitial sites within the hexagonal structure of the TiB2 or forming bonds with titanium and boron atoms. The preferred orientation of the films determined by XRD also changed with the increasing carbon content in the (001) crystalline plane.

Computational and structural study of titanium/carbon nanotube nanocomposite

In this study, the electronic structure and thermodynamic parameters of titanium doping at different locations of carbon nanotubes (6-6) have been investigated using density functional theory computational methods. The Ti prefers to be located near to vertex of the nanotube sidewall and at the central axis and leads to better structural stability and thermodynamic parameters than other sites. Then, the most stable and active structure for carbon monoxide adsorption was examined from two directions of oxygen and carbon atom, which is accompanied by hybridization and spatial repulsion. The results obtained from the energy level of the highest occupied HOMO orbital and the lowest occupied LUMO one and also NBO analysis indicated that the electron-accepting titanium metal (Mulliken charge for titanium atom above 0.5) has an empty orbital. Carbon monoxide gas is a donor of electron pairs. The adsorption of carbon monoxide from the oxygen atom side in the vertical state (IVA) on the surface of the nanotube doped with titanium was found to be the best.

Nanoporous TiCN with High Specific Surface Area for Enhanced Hydrogen Evolution Reaction

Transition-metal nitrides have attracted significant attention because of their unique electronic and surface properties and superior chemical and mechanical stability. Although various metal nitrides nanostructures have been realized, it remains challenging to introduce porosity and the high specific surface in these nanostructures, but they are required to expand the application possibility of these materials in energy storage and conversion. Here, we report the preparation of nanoporous titanium carbonitride using a high-nitrogen-containing mesoporous carbon nitride, C3N6 (MCN-4), as a reactive template and titanium tetrachloride as the titanium source. Nitrogen adsorption and microscopic results reveal that the prepared samples are highly nanoporous in nature, and the optimized sample exhibits a specific surface area of 700 m2/g and a high specific pore volume of 1.3 cm3/g. With the slight variation of the amount of MCN-4 in the synthesis mixture, the composition and the crystal structure of the nanoporous titanium carbonitride can be finely controlled. Near-edge X-ray absorption fine structure and Raman spectroscopic analyses of these samples confirm that the titanium atoms are strongly bonded with both carbon and nitrogen. The electrochemical hydrogen evolution reaction measurements of the optimized nanoporous titanium carbonitride loaded with 5 wt % of platinum in acidic medium reveal a high electrocatalytic performance with the overpotential of 27 mV at the current density of 10 mA cm–2, which is similar to that of commercially available Pt/C which contains 20 wt % of Pt. The combination of nanoporous structure together with the highly conducting carbon matrix in these metal carbonitride samples really helps to enhance the electrocatalytic activity. This research reveals a great opportunity for the design of porous metal nitride-based nanostructures with different composition and the potential for these materials to be used in energy storage and conversion technologies.

Low-lying isomers of (TiO2)n (n=2−8) clusters

Although there are diverse bond features of Ti and O atoms, so far only several isomers have been reported for each (TiO2)n cluster. Instead of the widely used global optimization, in this work, we search for the low-lying isomers of (TiO2)n (n=2−8) clusters with up to 10000 random sampling initial structures. These structures were optimized by the PM6 method, followed by density functional theory calculations. With this strategy, we have located many more low-lying isomers than those reported previously. The number of isomers increases dramatically with the size of the cluster, and about 50 isomers were found for (TiO2)7 and (TiO2)8 with the energy within 30 kcal/mol. Furthermore, new lowest isomers have been located for (TiO2)5 and (TiO2)8, and isomers with three terminal oxygen atoms, five coordinated oxygen atoms as well as six coordinated titanium atoms have been located. Our work highlights the diverse structural features and a large number of isomers of small TiO2 clusters.

Tribological Behaviors of Super-Hard TiAlN Coatings Deposited by Filtered Cathode Vacuum Arc Deposition.

High hardness improves the material’s load-bearing capacity, resulting in the enhancement of tribological properties. However, the high hardness is difficult to achieve for TiAlN coating due to the transformation of the close-packed structure from cubic to hexagonal and the increase in the grain size when the Al content is high. In the present study, the ultrahard TiAlN coatings (hardness > 40 GPa) are successfully developed by filtered cathodic vacuum arc technology to study the effect of nitrogen flux rate on tribological behaviors. The highest hardness of 46.39 GPa is obtained by tuning the nitrogen flux rate to achieve the regulation of Al content and the formation of nanocrystalline. The stable fcc TiAlN phase is formed via the solid-phase reaction under a high nitrogen concentration, and more aluminum atoms replace the titanium atoms in the (Ti, Al)N solid solution. The high Al content of the Ti0.35Al0.65N coating has a nanocrystalline structure and the average crystalline size is 16.52 nm. The TiAlN coating deposited at a nitrogen flux rate of 60 sccm exhibits the best properties of a combination of microhardness = 2972.91 Hv0.5, H = 46.39 GPa, E = 499.4 Gpa, ratio H/E* = 0.093 and ratio H3/E*2 = 0.403. Meanwhile, the TiAlN coating deposited at 60 sccm shows the lowest average friction coefficient of 0.43 and wear rate of 1.3 × 10−7 mm3 N−1 m−1 due to the best mechanical properties.

Interaction of Oxygen with the Stable Ti5Si3 Surface

The atomic structure and surface energies of several low-index surfaces (0001), (11¯00) and (112¯0) of Ti5Si3 in dependence on their termination were calculated by the projector augmented-wave method within the density functional theory. It was revealed that the mixed TiSi-terminated (0001) surface is stable within the wide range of change in the Ti chemical potential. However, the Ti-terminated Ti5Si3(0001) surface is slightly lower in energy in the Ti-rich limit. The oxygen adsorption on the stable Ti5Si3(0001) surface with TiSi termination was also studied. It was shown that the three-fold coordinated F1 position in the center of the triangle formed by surface titanium atoms is the most preferred for oxygen adsorption on the surface. The appearance of silicon as neighbors of oxygen in other considered F-positions leads to a decrease in the adsorption energy. The factors responsible for the increase/decrease in the oxygen adsorption energy in the considered positions on the titanium silicide surface are discussed.

Electronic structure properties of boron–doped and carbon–boron–codoped TiO2(B) for photocatalytic applications

A path to enhance the efficiency of photocatalytic devices is by doping the active semiconductor in order to maximize the light absorption. However, impurities could increase the recombination of photoinduced charge carriers, in order that a careful analysis on the effects of those impurities it is necessary. On this research, density functional theory calculations were applied to analyze the structure and electronic characteristics of B–doped and C+B–codoped TiO2(B) considering the lowest formation energy of substitutional impurities. Our calculations suggest that the swapping of a boron or carbon atom for an oxygen atom (B@O or C@O) is energetically more favorable than the replacement of titanium atoms. The obtained results seem to indicate that the boron substitution into O2C and O3C1 sites leads to its migration towards interstitial sites in both mono and codoping, thus causing a great geometrical distortion compared to pure TiO2(B). Furthermore, impurity states in the band gap were obtained after B@O doping and C+B–codoping, producing an improvement of the optical properties, so it can be assumed that this nanomaterial might act as a photoelectrode after an adequate design optimization that facilitates the charge carrier separation.

Molecular Emissions from Stretched Excitation Pulse in Nanosecond Phase-Selective Laser-Induced Breakdown Spectroscopy of TiO2 Nanoaerosols.

In phase-selective laser-induced breakdown spectroscopy (PS-LIBS), gas-borne nanoparticles are irradiated with laser pulses (∼2.4GW/cm2) resulting in breakdown of the nanoparticle phase but not the surrounding gas phase. In this work, the effect of excitation laser-pulse duration and energy on the intensity and duration of TiO2-nanoparticle PS-LIBS emission signal is investigated. Laser pulses from a frequency-doubled neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (532nm) are stretched from 8ns (full width at half maximum, FWHM) up to ∼30ns at fixed pulse energy using combinations of two optical cavities. The intensity of the titanium atomic emissions at around 500nm wavelength increases by ∼60%, with the stretched pulse and emissions at around 482nm, attributed to TiO, enhanced over 10 times. While the atomic emissions rise with the stretched laser pulse and decay around 20ns after the end of the laser pulse, the TiO emissions reach their peak intensity at about 20ns later and last longer. At low laser energy (i.e., 1mJ/pulse, or 80MW/cm2), the TiO emissions dominate, but their increase with laser energy is lower compared to the atomic emissions. The origin of the 482nm emission is explored by examining several different aerosol setups, including Ti-O, Ti-N, and Ti-O-N from a spark particle generator and Ti-O-N-C-H aerosol from flame synthesis. The 482nm emissions are attributed to electronically excited TiO, likely resulting from the reaction of excited titanium atoms with surrounding oxidizing (carbonaceous and/or radical) species. The effects of pulse length are attributed to the shift of absorption from the initial interaction with the particle to the prolonged interaction with the plasma through inverse bremsstrahlung.

Effect of plume dynamics on surface contamination during interaction of millisecond infrared fiber laser with titanium

Dynamics of the plume produced due to the interaction of millisecond infrared fiber lasers having different spectral profiles with titanium is investigated by high-speed imaging (HSI) and optical emission spectroscopy (OES) at different ambient atmospheres and pressures. The surface quality is associated with different plume dynamics that depends on the processing conditions. Reabsorption of the laser pulse by the neutral titanium atoms due to overlap of laser spectral profile with corresponding transition energies causes deposition of nanoparticles on the surface around the spot produced by the laser, which results in surface contamination and darkness around the spot. Increasing confinement of plume in Ar ambient than Ar/He leads to more darkness around the spot due to more availability of Ti species in a smaller volume for reabsorption. In vacuum/at low pressures, larger size of the expanding plume causes a smaller number of Ti species to interact with the laser pulse that produces clean surface around the spot. The surface contamination is prevented irrespective of the processing conditions by using the laser with customized spectral profile, which does not overlap with any neutral titanium atomic transitions (Ti I).

Characterization of Electronic Properties of Titanium Atom in Heterogeneous Ziegler-Natta Catalyst Analyzed by Soft X-ray Emission Spectrometry (SXES)

Abstract An advanced spectroscopic analysis by Soft X-ray Emission Spectrometry (SXES) was applied for the first time to the characterization of a heterogeneous Ziegler-Natta catalyst, which comprised TiCl4 and dibutylphthalate (DBP) supported on MgCl2. The high energy resolution capability of SXES made it possible to quantitatively detect outermost shell orbit signals of Lα at 452 eV and Lβ at 458 eV of Ti atom. These were assigned to Ti species interacting with DBP and MgCl2, respectively. From the correlation between the signal intensity ratios and the catalytic performances, it was presumed that Ti species interacting with MgCl2 should work as active sites for propylene polymerization.

Synthesis, Structure and Properties of Barium Ferrites BaFe<sub>11</sub>M<sub>1</sub>O19 (M= Al, Ti and Mn) Ceramics

The article shows the results of a research in which barium hexaferrite samples of the BaFe11M1O19 (M= Al, Ti and Mn) composition were obtained by solid-state synthesis. Samples substituted with titanium, aluminum, and manganese were obtained in a tubular furnace at an exposure time of 5 hours at a temperature of 1350°C, the sample, substituted with manganese, it was obtained at a temperature of 1250°C. The chemical composition was controlled using electron microscopy the samples obtained correspond to the initial composition with sufficient accuracy. Hexagonal plates represent the structure of all the obtained samples. According to X-ray phase analysis, all samples are monophasic and have the structure of barium hexaferrite. Using the data of powder X-rays, the parameters of the unit cell of the studied samples were calculated, when iron atoms are substituted by titanium or aluminum or manganese atoms, the crystal lattice is distorted, while its change is not the same for different crystallographic directions. During the doping of barium hexaferrite with titanium, aluminum or manganese atoms, the Curie temperature decreases. This is due to a decrease in the exchange interaction forces during the modification of the barium hexaferrite matrix. The aim of this study was to study the structure and change of the lattice parameters, the Curie temperature, depending on the substitution element.

Effect of aluminum substitution on structural, electronic and dielectric properties of cubic CaCu3Ti4O12 ceramics: A first-principles study

The paper sheds light on the effect of Al substitution on structural, electronic and dielectric properties of cubic CaCu3Ti4O12 ceramics based on first principles method. The CaCu3Ti4-xAlxO12 (x = 0, 0.5, 1, 1.5 and 2) ceramics still keeps a cubic lattice, and the lattice constant decreases with Al concentration enhanced. Phonon dispersion curves show that the structures of CaCu3Ti4-xAlxO12 ceramics are thermodynamically stable at x ≤ 1. The CaCu3Ti4-xAlxO12 ceramics have magnetic semiconductor properties and the band gaps corresponding to the high symmetry point G increases with increasing Al concentration. It can be concluded that doping Al can increase the dielectric constant and electronic transition intensity of cubic CaCu3Ti4O12 ceramics, and reduce its energy loss. In the low energy region, the dielectric constant of CaCu3Ti3.5Al0.5O12 ceramics is about ten times that of cubic CaCu3Ti4O12 ceramics. The ratio of aluminum atoms to titanium atoms of 1:7 May be the best ratio. It can also be concluded that when A13+ replaces Ti4+ ions, A1 also acts as an electron acceptor to reduce the electron concentration of Ti4+ ions, leading to the generation of oxygen vacancies. These results will provide a theoretical basis for the design of high dielectric constant materials.

Synthesis of transition metal carbides and high-entropy carbide TiZrNbHfTaC5 in self-shielding DC arc discharge plasma

The paper shows the feasibility of synthesizing micro- and nano-sized particles of binary metal carbides (Me–C) and high-entropy carbide (HEC) TiZrNbHfTaC5 by vacuum-free electric arc method. The method is based on the effect of self-shielding of the reaction volume from atmospheric oxygen by carbon monoxide CO, which is generated during arcing in air. The synthesis results in a solid solution with a NaCl-type carbide with a cubic lattice, which simultaneously contains atoms of titanium, zirconium, niobium, hafnium, tantalum, and carbon. The lattice parameter of the HEC TiZrNbHfTaC5 phase is ∼4.532 Å that is in line with the known data on this compound. The synthesis product contains micro-sized particle agglomerates of transition metal carbides. The synthesis products also contain nano-sized particles with a shell-core structure, in which the core can consist of metal carbide (TiC, ZrC, NbC, HfC, TaC) or HEC TiZrNbHfTaC5, and the shell is a graphite phase.

High-temperature tribological behavior of Ti containing diamond-like carbon coatings with emphasis on running-in coefficient of friction

Diamond-like carbon (DLC) coatings show a low coefficient of friction (COF) and high wear resistance against aluminum at elevated temperatures, yet they exhibit a high running-in COF (μ R ) prior to reaching a low and stable steady-state COF (μ s ). This study shows that incorporating titanium (Ti) atoms into the DLC structure would reduce the μ R . During pin-on-disk tests conducted on Ti incorporating hydrogenated-DLC (Ti-H-DLC) with 6.2 at.% Ti subjected to dry sliding against 319 Al (Al-6.5% Si), μ s values decreased from 0.27 at 25 °C to 0.11 at 200 °C. The specific wear rate of Ti-H-DLC decreased from 2.44 × 10 −5 mm 3 /Nm at 25 °C to 0.71 × 10 −5 m 3 /Nm at 200 °C. A typical DLC with 40 at.% H (H-DLC) tested at 200 °C showed a low μ s of 0.08 and a wear rate of 1.11 × 10 −5 mm 3 /Nm. However, at 200 °C, Ti-H-DLC showed a lower μ R of 0.16 compared to μ R = 0.78 of H-DLC, and the duration of the running-in period for Ti-H-DLC, t R = 3 revolutions, was shorter than H-DLC with t R of 200 revolutions. Comparisons made with other DLCs, including, NH-DLC, W-DLC, ta-C, and Si-O-H-DLC, in addition to H-DLC, all tested using the same method, revealed that, in the temperature range of 100–250 °C, Ti-H-DLC showed a better running-in behavior making Ti-H-DLC a suitable tool coating for manufacturing processes where high-temperature running-in sliding friction is important, including warm forming and (single-point) turning of aluminum alloys . • High-temperature tribological behavior of Ti-H-DLC against 319 Al was studied. • Low running-in COF and short running-in duration were recorded at 100 and 200 °C. • Compared to other DLC coatings, the lowest μ R and t R were obtained using Ti-H-DLC. • Ti-H-DLC tool coatings are useful for Al warm forming, machining operations ~200 °C.