Ti Reaction Research Articles

An Approach for Modeling and Quantifying Traffic-Induced Processes and Changes in Forest Road Aggregate Particle-Size Distributions

Forest road aggregate changes due to traffic. The physical processes that cause these aggregate changes need to be understood for more effective road management that can help reduce maintenance costs and efforts, and negative environmental impacts of forest roads. This study modeled three processes that could change the particle size distribution (PSD) of forest road aggregate: crushing (breaking down the surfacing material), subgrade mixing (moving upward of fine-grained, roadbed sediment), and sweeping (migration of loose aggregate particles to the shoulder and roadside by tire action). There are two types of sweeping: sweeping-out (dislodging large-size particles from tire tracks) and sweeping-in (accumulating large-size particles near the roadside and shoulder). Our study modeled the expected traffic-induced processes based on theoretical concepts and literature to examine how these processes change forest road aggregate PSD. Then the modeled results were compared with the observed PSDs from cross-sectional locations where traffic-induced processes likely occurred. Based on these comparisons, we enhanced the modeling and inferred how much the crushing, subgrade mixing, and sweeping-in processes changed the PSDs, but could not infer the sweeping-out process due to the difficulty in separating the sweeping-out from crushing. This study demonstrates that the traffic-induced processes could be modeled and quantified using the following assumptions: crushing was estimated by assuming a half logarithmic normal distribution with a mean of the crushed particle diameter and higher crushing rates for large-size particles; subgrade mixing was estimated by assuming the move-in of fine-grained subgrade soils from the road bed; and sweeping-in was estimated by assuming the move-in of large-size particles with a logarithmic normal distribution. Our modeling approach can offer insights on how traffic-induced processes affect road aggregate under various road and traffic conditions. This information can be useful in developing cost-effective road maintenance strategies and implementation plans.

Intermetallics evolution and fracture behavior of Nb interlayer inserted Si3N4/Ti joints brazed with AgCuTi filler

Robust Si3N4/Ti joints with Nb interlayer brazed using 68.8Ag26.7Cu4.5Ti (mass%) filler alloy (TICUSIL®) were developed. Interfacial microstructural evolution and mechanical behavior with respect to various brazing temperatures (1093–1153 K) and holding times (5–120 min) were mainly governed by reaction kinetics of dissolved Ti. Depending on the relative distribution of Ti atoms, types of Cu–Ti intermetallics formed differ across the interfaces. At Ti/Nb interface, multi–layered compounds consisted of Ag–solid solution sandwiched between Cu–Ti intermetallics were formed for all brazing conditions. At Nb/Si3N4 interface, competing Ti reactions occurred when brazed at 1093 K for 5 min. With rising brazing temperature, increasing preferential reactivity of Ti for Si3N4 instead of Cu minimized the formation of Cu–Ti intermetallics. Besides functioning as a residual stress reliever, Nb inhibited migration of ejected Ti from the substrate toward Si3N4, minimizing intermetallics formation at Nb/Si3N4 interface. All joints fractured at Nb/Si3N4 interface due to residual stress when tested at room temperature. Brazing at 1153 K for 10 min produced the highest average bending strength of 181 MPa. Quantitative analysis of relative residual stress caused by intermetallics is presented based on the fracture heights of Si3N4.

Evaluated the level density for proton induced nuclear resonances in (P+48Ti) reaction using different models

The experimental proton resonance data for the reaction P+48Ti have been used to calculate and evaluate the level density by employed the Gaussian Orthogonal Ensemble, GOE version of RMT, Constant Temperature, CT and Back Shifted Fermi Gas, BSFG models at certain spin-parity and at different proton energies. The results of GOE model are found in agreement with other, while the level density calculated using the BSFG Model showed less values with spin dependence more than parity, due the limitation in the parameters (level density parameter, a, Energy shift parameter, E1and spin cut off parameter, σc). Also, in the CT Model the level density results depend mainly on two parameters (T and ground state back shift energy, E0), which are approximately constant in their behavior with the proton energy compared with GOE model. The RMT estimation used to calculate the corrections of the incompleteness proton resonance measurement data by using two methods; the conventional analysis method, which depends on the resonance widths and the updated, developed, tested and applied a new analysis method, which depends mainly on the resonance spacings. The spacing analysis method is found much less sensitive to non-statistical phenomena than is the width analysis method. Where the analysis of a given data set via these two independent analysis methods indicated the increasing in the reliability of the determination of the missing fraction of levels, the observed fraction f between 0.87+0.13−0.11 – 0.68+0.12−0.12 for different spin-parity of this reaction and then the distinguishability in the level density calculations can be achieved. The modified Porter Thomas distribution along with the maximum likelihood function have been used to get the missing levels corrections for 5 proton resonance sequences in the present reaction. To estimate the present long-range correlations for pure sequence of levels the mean square of the deviation of the cumulative number of levels from a fitted straight line represented by the Dyson and Mehta Δ3 statistic has been employed for spin parity 12+, and calculated the <Δ3> against the cumulative number of proton levels.

Effect of TiC Nanoparticles Supported by Ti Powders on the Solidification Behavior and Microstructure of Pure Aluminum

A novel grain refiner consisting of TiC nanoparticles (NPs) supported by Ti powders (abbr. TiC/Ti refiner) was prepared by high-energy milling. The addition of 0.5 wt% TiC/Ti refiner converted the structure of pure Al from coarse dendrites to fine equiaxed grains with the average grain size of 114.7 μm, and it also increased the nucleation temperature of α(Al) from 656.7 to 664.4 °C. When TiC/Ti refiner was introduced into Al melt, the heat released from the Al–Ti reaction promoted the uniform dispersion of TiC NPs. The dissolution of the reaction product TiAl3 released Ti atoms into the melt and thus formed a “Ti-rich transition region” around TiC NPs. The dispersive TiC NPs could act as the heterogeneous nuclei for α(Al) and the “Ti-rich transition region” further improved the lattice orientation relationship between Al ( $$\bar{1}1\bar{1}$$ ) and TiC ( $$11\bar{1}$$ ) planes, which eventually resulted in the refining of α(Al).

Effects of Ti Sheet Insert on Microstructure and Properties of Graded Composites of TiB2-based Ceramic and Ti-6Al-4V Alloy

By inserting Ti sheet between ceramic powder and Ti alloy steel, (TiC-TiB2)/Ti-6Al-4V graded composites were rapidly prepared by SHS centrifugal-casting process with different Ti sheet thickness from 0.5 to 1.5 mm. XRD, FESEM and EDS results show that there is no significant change in phase composition of the ceramic matrix after inserting Ti sheet, but the inserting promotes the microstructure refinement of the reaction products with the thickness increasing. Meanwhile, the introduction of Ti sheet not only enhances the thickness of the gradient interface, but also decreases the thermal infected zone of interface. Moreover, fusion bonding and atomic interdiffusion between liquid TiC-TiB2 and excessive Ti liquid in thermal vacuum circumstances are considered to initiate peritectic reaction of TiB2(s) + Ti(l) → 2TiB(s), direct growth of TiB solids from liquid Ti and eutectic reaction of TiB solids and liquid Ti at the final stage of joint solidification, so that consumption of TiB2 solids and increase of TiB crystal relieve the interface residual stress, and the joint of the ceramic to Ti alloy is achieved in multilevel and multi-scale microstructure. The joint represents a transitional change in Vickers hardness and gets a high shear strength of (316±25) MPa between the ceramic and Ti alloy.

Double and Triple Si-H-M Bridge Bonds: Matrix Infrared Spectra and Theoretical Calculations for Reaction Products of Silane with Ti, Zr, and Hf Atoms.

Infrared spectra of matrix isolated dibridged Si(μ-H)2MH2 and tribridged Si(μ-H)3MH molecules (M = Zr and Hf) were observed following the laser-ablated metal atom reactions with SiH4 during condensation in excess argon and neon, but only the latter species was observed with titanium. Assignments of the major vibrational modes, which included terminal MH, MH2 and hydrogen bridge Si-H-M stretching modes, were confirmed by the appropriate SiD4 isotopic shifts and density functional vibrational frequency calculations (B3LYP and BPW91). The Si-H-M hydrogen bridge bond is calculated as weak covalent interaction and compared with the C-H···M agostic interaction in terms of electron localization function (ELF) analysis and noncovalent interaction index (NCI) calculations. Furthermore, the different products of Ti, Zr, and Hf reactions with SiH4 are discussed in detail.

Effects of Ta2O5 on mechanical properties and elements diffusion of Ti/Al2O3 composites prepared via hot pressing sintering

Homogeneous Ti/Al2O3 composites with different volume percentages of Ta2O5 addition were prepared at different temperatures via hot pressing sintering. Laminated Ti/Al2O3 composites with different volume percentages of Ta2O5 added were prepared. The effects of Ta2O5 on the composition, microstructure, mechanical properties and elements diffusion of the composites were characterized and investigated. Ta2O5 inhibited the production of TiAl and Ti3Al by forming solid solution with Ti or new reaction product of Al. This solid solution melted and filled the void of Al2O3 phase to increase the density of Ti/Al2O3 composites at high temperature. Mechanical properties had also been improved by this phenomenon. Because Al element couldn’t diffuse in Ta or react with it, Al couldn’t diffuse through the Ta-enriched area at the interface of Ti and Al2O3.

Implementation of DSC analysis in reaction kinetics during heating of Ti–50 at.%Al powder mixture

In this study, the reactions in Ti–50 at.%Al powder mixture upon heating at constant heating rates were studied using DSC analysis. Heating up the mixture resulted in melting of aluminum at temperatures close to its melting temperature, which was manifested as an endothermic peak in DSC curves. The melting of aluminum was the onset of an intense exothermic reaction, so-called combustion synthesis reaction which results in the formation of titanium aluminide. The shift in exothermic peak temperature in various linear heating rates was used to calculate the apparent activation energy according to Kissinger-type model-free methods. Heating rates of 10, 20, 30, 40, and 50 K min−1 were used to estimate the activation energy based on DSC data. In order to study the effect of ball-milling on reaction behavior, the starting powder mixture was ball-milled for different times, and a comparison was made between non-ball-milled and ball-milled DSC curves. The results showed that ball-milling tends to diminish the endothermic peak of melting of aluminum and shift the exothermic reaction temperature to lower temperatures, apparently altering the mechanism from a solid–liquid to an almost solid–solid one. The activation energy of the process in the non-ball-milled state was found to be close to the activation energy of diffusion of aluminum in TiAl (220 kJ mol−1). However, the application of same model-free methods to the ball-milled samples showed unexpectedly increased values for activation energy. It would be appropriate to check other methods as well as for calculation of activation energy in the ball-milled systems.

Influence of Sintering Temperature on the Microstructure and Mechanical Properties of In Situ Reinforced Titanium Composites by Inductive Hot Pressing.

This research is focused on the influence of processing temperature on titanium matrix composites reinforced through Ti, Al, and B4C reactions. In order to investigate the effect of Ti-Al based intermetallic compounds on the properties of the composites, aluminum powder was incorporated into the starting materials. In this way, in situ TixAly were expected to form as well as TiB and TiC. The specimens were fabricated by the powder metallurgy technique known as inductive hot pressing (iHP), using a temperature range between 900 °C and 1400 °C, at 40 MPa for 5 min. Raising the inductive hot pressing temperature may affect the microstructure and properties of the composites. Consequently, the variations of the reinforcing phases were investigated. X-ray diffraction, microstructural analysis, and mechanical properties (Young’s modulus and hardness) of the specimens were carried out to evaluate and determine the significant influence of the processing temperature on the behavior of the composites.

Analysis of 4He+40Ca and 4He+44Ti scattering using different optical model potentials

Elastic scattering of 4He+40Ca and 4He+44Ti reactions at backward angles has been analyzed using two differentmodels, microscopic and semimicroscopic folding potentials. The derived real potentials supplemented with phenomenological Woods–Saxon imaginary potentials, provide good agreement with the experimental data at energy Ec.m. = 21.8 MeV without need to renormalize the potentials. Coupledchannels calculations are used to extract the inelastic scattering cross section to the low-lying state 2+ (1.083 MeV) of 44Ti. The deformation length is obtained and compared with the electromagnetic measurement values as well as those obtained from previous studies.

Combustion of cylindrical Ti + 0.5C compacts: Influence of mechanical activation, thermovacuum degassing, and ambient pressure

We explored the influence of mechanical activation (MA), thermovacuum degassing (TVD), and ambient pressure on burning velocity and sample shrinkage/elongation for SHS reactions in cylindrical Ti + 0.5C powder compacts. Thermovacuum degassing of Ti + 0.5C mixtures was found to increase the burning velocity (2-fold) and sample shrinkage. Mechanical alloying decreased the burning velocity and gave large (3-fold) sample elongation. The results can be readily rationalized in terms of conduction-convection combustion theory.

Troubles in the Systematic Prediction of Transition Metal Thermochemistry with Contemporary Out-of-the-Box Methods.

The recently developed DLPNO-CCSD(T) method and seven popular DFT functionals (B3LYP, M06, M06L, PBE, PBE0, TPSS, and TPSSh) with and without an empirical dispersion term have been tested to reproduce 111 gas phase reaction enthalpies involving 11 different transition metals. Our calculations, corrected for both relativistic effects and basis set incompleteness, indicate that most of the methods applied with default settings perform with acceptable accuracy on average. Nevertheless, our calculations also evidenced unexpected and nonsystematic large deviations for specific cases. For group 12 metals (Zn, Cd, Hg), most of the methods provided mean unsigned errors (MUE) less than 5.0 kcal/mol, with DLPNO-CCSD(T) and PBE methods performing excellently (MUE lower 2.0 kcal/mol). Problems started with group 4 metals (Ti and Zr). The best performer for Zr complexes with MUE of 1.8 kcal/mol, PBE0-D3, provides MUE larger than 8 kcal/mol for Ti. DLPNO-CCSD(T) provides a reasonable MUE of 3.3 kcal/mol for Ti reactions but gives MUE a larger than 14.4 kcal/mol for Zr complexes, with all the larger deviations for reactions involving ZrF4. Large and nonsystematic errors have been obtained for group 6 metals (Mo and W), for eight reactions containing Fe, Cu, Nb, and Re complexes. Finally, for the whole set of 111 reactions, the DLPNO-CCSD(T), B3LYP-D3, and PBE0-D3 methods turned out to be the best performers, all providing MUE below 5.0 kcal/mol. Since DFT results cannot be systematically improved and large nonsystematic deviations of 20-30 kcal/mol were obtained even for best performers, our results indicate that current DFT methods are still unable to provide robust predictions in transition metal thermochemistry, at least for the functionals explored in this work. The same conclusion holds for both DLPNO-CCSD(T) and canonical CCSD(T) methods when used entirely as out-of-the-box. However, if careful investigation of core correlation is performed, relativistic effects are properly included and the quality of the reference wave function is properly checked, CCSD(T) methods can still provide good quality results that might even be used to validate DFT methods due to paucity of accurate thermodynamic data for realistic-sized transition metal complexes.

Analysis of the normal optical, Michel and molecular potentials on the 40Ca(6Li, d)44 Ti reaction

Full finite-range (FFR) distorted-wave Born approximation (DWBA) method has been applied to analyse the angular distributions of cross-sections of the 40Ca(6Li, d) 44Ti reaction at 28 MeV incident energy for the 22 transitions involving both the bound and unbound states of 44Ti by using the normal optical, Michel and molecular potentials. The extracted spectroscopic factors for the three optical potentials are compared with those of some previous studies of zero-range (ZR) calculations of the 40Ca(6Li, d) 44Ti reaction using the normal optical potential. The χ 2 values of all the levels are obtained for the three optical potentials to estimate the quality of the fits. Molecular and Michel potentials have been used for the first time to analyse the four-nucleon transfer reaction and it seems that the molecular potential fits the experimental data more satisfactorily for some of the states than the normal optical and Michel potentials.

The role of CaH2 in preventing oxidation for the production of single-phase NiTi alloy in solid state

Single-phase NiTi synthesized from Ni and TiH2 powders was successfully formed in a solid-state reducing environment of CaH2. A comparison was done with a specimen synthesized in an environment without CaH2. An in-depth investigation on the surface of the specimen sintered without CaH2 revealed a thick layer of oxide with a thickness of 94 μm, whereas the specimen sintered in the reducing environment showed a significant reduction in oxide formation. The decomposition of CaH2 liberates Ca, which effectively reacts with oxygen at 930 °C and consumes available oxygen in the system, thus minimizing oxygen to react with Ti to form TiO2. A significant reduction of this oxidation creates a balanced composition between Ni and Ti. An oxygen-free environment allows unhindered Ni–Ti reaction, which leads to the formation of single-phase NiTi, which is mostly found formed in the middle volume of the specimen. The optimum enthalpy change was observed to occur at the middle of the specimen with ΔHA–M = 26 J/g on cooling and ΔHM–A = 25.5 J/g on heating, and the enthalpy was found to decrease towards the edge of the specimen due to the decreasing volume of transforming B2-NiTi.

Microstructural Studies on Ti–Y2O3 Interface Reaction Products

Ti and Y2O3 reaction products find application in flash memory drives, in ODS steels as dispersion strengthening constituent and in Ti castings. The solid state reaction between Ti and Y2O3, was studied using a suitable experimental setup. The reaction product was investigated by a variety of electron microscopy techniques including SEM, TEM and EBSD. Surface characterisation revealed islands of the reaction product and step like structure for the un-reacted Ti matrix, typical of thermal etching. The reaction product was identified as Y2TiO5 by analysis of selected area electron diffraction pattern.

Titanium (IV) complexes stabilized by 2,6-bis-(α,α′-diphenyl(hydroxy)methyl)-pyridine: Catalytic activity in olefin polymerization and impact of lithium and magnesium chlorides

A series of mono- and bi-nuclear complexes were synthesized by combining 2,6-bis-(α,α′-diphenyl(hydroxy)methyl)-pyridine and halide or alkoxide Ti(IV) derivatives. Crystal structures of synthesized products were determined. It was demonstrated that individual complexes 2–5 are active in ethylene and 1-hexene polymerization only in the presence of Et2AlCl/Bu2Mg binary co-catalyst. The systems formed from the lithium or magnesium salts of 2,6-bis(α,α′-diphenyl(hydroxy)methyl)-pyridine and TiCl4, containing respective Ti complexes and reaction byproducts (LiCl or MgCl2), are able to catalyze ethylene polymerization when activated by methylalumoxane or trimethylaluminum (TMA). The highest efficiency of catalysis was observed in the presence of binary co-catalysts Et2AlCl/Bu2Mg. The results of this study show the unique ability of Li and Mg chlorides to improve the catalytic ability of post-metallocene pre-catalysts.

Effect of Bonding Temperature on the Microstructures and Strengths of C/C Composite/GH3044 Alloy Joints by Partial Transient Liquid-Phase (PTLP) Bonding with Multiple Interlayers

With the use of Ti/Ni/Cu/Ni multiple foils as interlayer, carbon/carbon (C/C) composite was bonded to Ni-based superalloy GH3044 by partial transient liquid-phase bonding technique. The effect of bonding temperature on the microstructures and strengths of the joints was investigated. The results showed that gradient structural multiple interlayers composed of “C–Ti reaction layer/Ti–Ni intermetallic compound layer/Ni–Cu sosoloid/residual Cu layer/Ni-GH3044 diffusion layer” were formed between C/C composite and GH3044. The shear strength of the C/C composite/GH3044 joint reached the highest value of 26.1 MPa when the bonding temperature was 1,030 °C. In addition, the fracture morphology showed that the fracture mode changed with the increase of bonding temperature.

Interfacial reactions in Ti–Fe particles reinforced hydroxyapatite matrix composites

A very important factor that influences the properties of a composite is related to the interfacial reaction. In present study, the hydroxyapatite (HA) materials reinforced by Ti–Fe particles were fabricated, and then the interfacial reactions between the HA and Ti–Fe were investigated. The results showed that the desirable Ti phase remained in the matrix after sintering since the introduction of Fe suppressed both the decomposition of HA and interaction between HA and Ti. Furthermore, it was found that a certain amount of small pores near/in interface was beneficial for obtaining an appropriate interfacial bonding between reinforcing Ti–Fe particles and HA matrix.

Strength of theEp=1.842MeV resonance in the40Ca(p,γ)41Sc reaction reexamined

The strength of the $E_{\rm p} = 1.842$ MeV resonance in the $^{40}$Ca(p,$\gamma$)$^{41}$Sc reaction is determined with two different methods: First, by an absolute strength measurement using calcium hydroxide targets, and second, relative to the well-determined strength of the resonance triplet at $E_\alpha$ = 4.5 MeV in the $^{40}$Ca($\alpha$,$\gamma$)$^{44}$Ti reaction. The present new value of $\omega\gamma=(0.192\pm0.017)$ eV is 37% (equivalent to $3.5\sigma$) higher than the evaluated literature value. In addition, the ratio of the strengths of the 1.842 MeV $^{40}$Ca(p,$\gamma$)$^{41}$Sc and 4.5 MeV $^{40}$Ca($\alpha$,$\gamma$)$^{44}$Ti resonances has been determined to be $0.0229\pm0.0018$. The newly corrected strength of the 1.842-MeV resonance can be used in the future as a normalization point for experiments with calcium targets.

Microstructures and mechanical properties of Cf/SiC composite and TC4 alloy joints brazed with (Ti–Zr–Cu–Ni)+W composite filler materials

Abstract In this study, carbon fiber reinforced SiC (Cf/SiC) composite was joined to TC4 alloy using (Ti–Zr–Cu–Ni)+W mixed powders as composite filler material at proper process parameters. The interfacial microstructures and evolution mechanism of Cf/SiC composite/(Ti–Zr–Cu–Ni)+W/TC4 alloy joints were investigated based on scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). The mechanical properties of the brazed joints were measured by the mechanical testing machine. The results showed that Ti and Zr elements in the interlayer can react with the brazed material, the brazed joint mainly consisted of Ti3SiC2, Ti5Si3, (Ti, Zr)C, Ti2Cu, Cu10Zr7, Ti(Cu, Ni) and Ti(s,s) reaction products. The diffusion–reaction layer was formed between the interlayer and TC4 alloy due to the element interdiffusion. The brazing parameters had a distinct effect on the interfacial reaction between Cf/SiC composite and filler material, which affected the shear strength of the brazed joints. Adding the appropriate W powder was beneficial for relaxing the residual thermal stress and reinforcing the brazed joints. The maximum shear strength of the brazed joints was 166 MPa at room temperature and 96 MPa at 800 °C high temperature acquired at 930 °C for 20 min using (Ti–Zr–Cu–Ni)+15 vol.%W composite filler material.