Transition Ti Research Articles

Photocatalytic degradation of 2,4-dichlorophenoxyacetic acid by electrospun TiO2 nanofibres synthesised from two different titanium molecular precursors.

The evaluation of the photocatalytic properties of electrospun TiO2 nanofibres (TiO2-NFs) synthesised in the same experimental conditions using two distinct precursors, tetraisopropyl orthotitanate (TTIP) and tetrabutyl orthotitanate (TNBT), with morphology and crystalline structure controlled by annealing at 460°C for 3h is presented. The presence of circular-shaped TiO2-NFs was corroborated by scanning electron microscopy (SEM). By using X-ray photoelectron spectroscopy (XPS), the chemical binding energies and their interactions of the TiO2 with the different incorporated impurities were determined; the most intense photoelectronic transitions of Ti 2p3/2 (458.39eV), O 1s (529.65eV) and C 1s (284.51eV) were detected for TTIP and slightly blue-shifted for TNBT. By using energy-dispersive X-ray spectroscopy (EDS), the chemical element percentages in TiO2 were determined. Using X-ray diffraction, it was found that the annealed electrospun TiO2-NFs presented the anatase crystalline phase and confirmed by Raman scattering. Bandgap energies were determined by diffuse reflectance spectroscopy at room temperature. The photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide under exposure to ultraviolet light was studied using the TiO2-NFs obtained with the two molecular precursors. The results showed that the catalyst, prepared with the TTIP precursor, turned out to be the one that presented the highest photocatalytic activity with a half-life time (t1/2) of 28min and a degradation percentage of 93%. The total organic carbon (TOC) in the solutions resulting from the 2,4-D degradation by the TiO2-NFs was measured, which showed a TOC removal of 50.67% for the TTIP sample and 36.14% for the TNBT sample. Finally, by using FTIR spectroscopy, the final chemical compounds of the degradation were identified as H2O and CO2.

Femtosecond laser welding of sapphire-copper using a thin film titanium interlayer

The ability to weld metals and sapphire is widely required in aerospace, micro-electro-mechanical systems and microwave energy delivery devices. The experiments of femtosecond laser welding between sapphire and copper (Cu) were conducted under non-optical contact conditions. And the effect of pre-fabricating a Ti film on the sapphire surface using femtosecond laser on the bonding strength of ssapphire/Cu joint was investigated. The interface of the sapphire/Cu directly welded by femtosecond laser contains a mixture of sapphire and copper, and the shear strength of the sapphire/Cu interface was approximately 46.4 MPa. The results indicated that the laser-induced molten state of sapphire and the laser-ablated copper mixed together at the interface, filling the gaps and forming an effective metallurgical bond. And then, in the case that the Ti film was prepared on the sapphire surface through femtosecond laser-induced backward transfer (LIBT), a Ti transition layer between sapphire and cooper was observed on the bonding interface of the joint, and the shear strength of the joint increased to approximately 115.5 MPa. A mixture of sapphire, copper, titanium, and titanium oxide was observed at the interface of the joint. The Ti layer between sapphire and copper may effectively alleviated residual stresses at the interface and promoted bonding between copper and sapphire, thereby improving the strength of the joint. The methods and results of this study have reference value for the ultrafast laser bonding between other transparent brittle materials and metals.

An ab initio guided study on the shear-induced fcc-hcp transition: A case study of (Ti,Al)N/ZrN multilayers

The cubic-wurtzite phase transition of (Ti,Al)N-based thin films at high temperatures is the chief determing factor for their thermal stability. Nevertheless, its mechanism of atomic shear is not yet well explored theoretically. Here, we correlate the coherent interfaces with wurtzite formation within (Ti,Al)N/ZrN multilayers by a combined ab initio and experimental study. Compared to (Ti,Al)N, the multilayer exhibits a delayed formation of hexagonal close-packed (hcp) wurtzite-type AlN phase, which is encapsulated by face-centered cubic (fcc-)(Ti,Zr)N and fcc-(Zr,Ti)N layers when annealed at 1200 °C. Based on the orientation relationships of (200)fcc//(0001)hcp and (220)fcc//(01-10)hcp among hcp-AlN and neighboring fcc-(Ti,Zr)N as well as fcc-(Zr,Ti)N by the solid-state nudged elastic band (SS-NEB) method, two mechanisms for atomic shear during fcc-hcp transition are proposed. The introduction of ZrN layers effectively suppresses the fcc-hcp transition, due to higher activation energies induced by the coherent interfaces.

Enhancing the bond strength of magnetron-sputtered copper layers on polyimide and polyether ether ketone surfaces through surface modification

This study explores the fabrication of composites involving polyimide (PI) and polyether ether ketone (PEEK) resins with Cu using chemical treatment and sandblasting, followed by plasma cleaning in a vacuum environment charged with Ar. To enhance the bonding strength of Cu to PI and PEEK, vacuum magnetron sputtering was used to deposit an intermediate transition layer of titanium and a plated seed layer of Cu onto the resin. For PI/copper composites, the copper layer’s highest bonding strength was achieved through sandblasting and plasma cleaning for 150 s at a bias voltage of 100 V. For PEEK/Cu composites, the optimal bonding strength of the copper layer was observed after 80 s of plasma cleaning. Surface roughness is important in the bonding strength of the copper layer. Additionally, the Ti transition layer strengthens bonding forces between Cu and both PI and PEEK. X-ray photoelectron spectroscopy revealed Ti–O bond formation with oxygen in the resins and Ti–C bonds within the carbon, indicating chemical interactions that bolstered Cu adhesion to resins. Adjusting the bias voltage had varying effects on the bonding strength of resin/Cu. For PI/Cu, the bonding force decreased with increasing bias voltage (20–150 V) owing to excessive bias voltage causing surface defects on the plated Cu layer, which reduced the density of the plated Cu layer. Conversely, the PEEK/Cu bonding force initially increased with increasing bias voltage due to enhanced surface bombardment. Beyond an optimal point, the bonding force in PEEK/Cu decreased due to unfavorable effects on layer density.

Effect of d-block metals (M = Ti, Zr, Hf) decorated fullerenes M@C60 as sensor nanostructured materials for volatile organic compounds (VOCs): Approach from computational study

Volatile organic compounds (VOCs) are organic substances that readily evaporate into the atmosphere at room temperature, posing a regular exposure risk to humans. These compounds are associated with various environmental issues, including stratospheric ozone layer depletion, ground-level smog formation, climate change, sick building syndrome, plant decay, atmospheric toxicity, and potential carcinogenic effects on human health. In this study, we utilized ab-initio calculations based on density functional theory (DFT) at the B3LYP-GD3(BJ)/Def2-SVP method to examine how the functionalization of C60 fullerene with Ti, Hf, and Zr transition metals affects its sensing capabilities for volatile organic compounds, specifically methylcyclopentane (MCP), propanone (PPN), and benzene (BZN). The maximum adsorption energy of the transition metal decorated nanocages was recorded at 73.689 kcal/mol corresponding to PPN_Zr@C60 in tandem with the least energy gaps indicating higher conductivity of the PPN_Zr@C60 nanocage with the short bond distance of 1.929 Å for (Zr – O) interaction. The adsorption energy value proposes the adsorption of the volatile organic compound on the Ti, Hf, and Zr transition metal decorated C60 fullerene following the order BZN_Hf@C60 < BZN_Ti@C60 < PPN_Zr@C60. The studied systems possess a relatively high desorption time and they follow the increasing trend – BZN_Hf@C60 < MCP_Hf@C60 < MCP_Zr@C60 < MCP_Ti@C60 < PPN_Hf@C60 < BZN_Zr@C60 < BZN_Ti@C60 < PPN_Ti@C60 < PPN_Zr@C60. The results account that Zr@C60 possesses the highest desorption time and adsorption energy, hence more apposite for detecting the studied VOCs. It also divulges in Hf@C60 contains the least desorption time and least adsorption energy, therefore is not suitable for the detection as it basically portrays the least affinity for the adsorbed VOCs molecule. These results indicate that the VOC transition metal functionalized Ti@C60 and the Zr@C60 are excellent sensors for the effective detection and adsorption of volatile organic compounds which may be useful for environmental protection and the safeguard of human health.

Effect of Zn and Ti transition foil on the microstructure and mechanical properties of hot rolling bonded Al/Mg composite plates

The issue of interface failure, which stems from the hard and brittle nature of the intermetallic compound (IMCs) in Al/Mg composite sheets, has raised concerns. To alleviate this problem, this study proposes to incorporating foil transition materials at the interface of the hot rolling bonded Al/Mg composites. The Al/Mg composite plates are prepared through multiple pass rolling and annealing processes, and the effects of the foil transition material on the microstructure, mechanical properties, and formability of the Al/Mg composite plates are investigated. The results demonstrate that the continuous distribution of Zn foil at the interface can effectively hinder the continual formation of Al–Mg IMCs at the interface. The interface of the Al/Mg composite plate with Ti foil implantation consists of alternating Ti foil and Al–Mg IMC layers, effectively reducing the proportion of Al–Mg IMCs at the interface. The addition of Zn foils decreases the shear bond strength, tensile strength, and bending resistance of the composite plate. In contrast, the incorporation of Ti foil significantly enhances the interfacial shear bonding strength, while the tensile strength remains mostly unchanged. Furthermore, the implantation of Ti foil substantially improves the Erichsen value of the Al/Mg composite plate. Therefore, this study offers valuable insights into the preparation and enhancement of the mechanical and formability properties of rolled Al/Mg composite plates containing transition materials.

Exploring the hydrogen storage possibility of the pristine, defected and metals decorated o-B2N2 monolayers: Insights from DFT simulations

To explore the possibility of hydrogen storage, we conducted dispersion-corrected density functional theory (DFT-D3) simulations on pristine, defected and metals (including Na and K alkali metals, Be, Mg and Ca alkaline-earth metals and Sc, Ti, Y and Zr transition metals) decorated orthorhombic diboron dinitride (o-B2N2) monolayers. The results suggest that the pristine, defected and metals (Na, K, Be, Mg, Ca, Sc, Y and Zr) decorated o-B2N2 monolayers are not desirable medium for storage of hydrogen. However, the Ti decorated o-B2N2 monolayer showed promising potential for hydrogen storage medium. The Ti atom displayed a significant binding energy (Eb) of −2.79 eV with the o-B2N2 monolayer, causing a reduced band gap and increased conductivity. In the case of Ti decorated o-B2N2 monolayer, the adsorption energy (Ead) for first hydrogen adsorption is −0.47 eV, meeting the department of energy (DoE)'s criteria. In addition, a charge donation from the Ti metal to o-B2N2 monolayer has been observed through PDOS, Löwdin charge transfer and charge density difference. The two Ti decorated o-B2N2 monolayer can bind a total of thirty-four hydrogen molecules within the DoE's limit, with Ead of −0.31 eV/H2 and 396 K of desorption temperature. The calculated gravimetric storage capacity is 11.21 %, which is remarkably higher than the DoE's specified range. Ab initio molecular dynamics calculations predict a favourable thermal stability of two Ti decorated o-B2N2 monolayer at 396 K. As a summary, this research highlights the promising prospects of the Ti decorated o-B2N2 monolayer as an efficient medium for high-capacity hydrogen storage.

Combined High-Throughput DFT and ML Screening of Transition Metal Nitrides for Electrochemical CO2 Reduction

The electrochemical reduction of CO2 (CO2RR) using renewable electricity has the potential to reduce atmospheric CO2 levels while producing valuable chemicals and fuels. However, the practical implementation of this technology is limited by the activity, selectivity, and stability of catalyst materials. In this study, we employ high-throughput density functional theory (DFT) calculations to screen ∼800 transition metal nitrides and identify potential catalysts for CO2RR. The stability and activity of the screened materials were thoroughly evaluated via thermodynamic analysis, revealing Co, Cr, and Ti transition metal nitrides as the most promising candidates. Additionally, we conduct a feature importance analysis using machine learning (ML) regression models for binding energy prediction and determine the primary factors influencing the stability of catalysts. We show that the group number of metals has a significant impact on the binding energy of *OH and thus on the stability of the catalysts. We anticipate that this combined approach of high-throughput DFT screening and design strategy derived from ML regression analysis could effectively lead to the discovery of improved energy materials.

Comparison of lithium borate fusion and four-acid digestions for the determination of whole-rock chemistry – implications for lithogeochemistry and mineral exploration

Mining and exploration companies routinely use four-acid digestion (4AD), inductively coupled plasma, atomic emission spectra/mass spectrometry methods from commercial assay laboratories for analysing drill and rock samples for lithogeochemical assessment and resource reporting. This method is also known to exhibit lower recovery of elements hosted by resistate minerals. To assess the impact of lower recoveries on lithogeochemical interpretation, a suite of commonly used elements for lithogeochemical analysis (high-field-strength elements Zr, Hf, Nb, Ta, Ti and Eu and transition elements V and Sc) was analysed by 4AD and alkali fusion/acid digestion (AFAD). Lower recoveries in the 4AD relative to the AFAD were recorded for Zr, Hf, Nb, Ta, Ti and Eu; Sc and V reported similar concentrations for both decomposition methods. Despite the lower recoveries for Nb, Ta and Ti, element ratios were largely preserved with the 4AD method due to the recoveries covarying at a 1:1 ratio. A plot of Ti/Nb against V/Sc was found to be largely unaffected by decomposition method, producing similar compositional classifications between the two digestion methods. Use of the Eu anomaly (Eu/Eu*) to determine plagioclase fractionation was also found to be unaffected by decomposition method. In contrast, a standard Zr/Ti v. Nb/Y discrimination plot produced incorrect classifications with 4AD producing more mafic and alkaline classifications relative to the AFAD method. Magmatic fertility interpretations utilizing Zr/Hf were also found to be affected in the 4AD results due to the lower recovery of Zr relative to Hf. This resulted in a bias in the 4AD results and produced false-positive anomalism in fertility assessments. Multiple decomposition methods including combinations of acid and fusion methods are recommended for lithogeochemical analysis utilizing large regions of the periodic table. However, if only 4AD data are available, plots such as Ti/Nb v. V/Sc and Nb/Ta, which preserve their ratios, can be used for lithogeochemical classification. Supplementary material: Wholerock geochemical data and detailed methods are available at https://doi.org/10.6084/m9.figshare.c.6444444

Investigation of Solid–Solid Transition in Ti and Zr at High Pressure by Electrical Resistivity

The group IV metals Ti and Zr are isoelectronic and crystallize in a hexagonal closed packed structure at ambient conditions. Herein, the electrical resistivity of Ti and Zr at room temperature with increasing pressure up to 20 GPa is reported using a 4‐wire resistivity method. The slope of their resistivity against pressure changes value at various pressures. At 10 GPa, resistivity of Ti increases with pressure whereas Zr resistivity decreases with pressure. The opposite behavior is interpreted to be due to incoherent scattering in Ti versus coherent scattering in Zr, as both undergo solid α → ω transition. By comparing the Zr result with a previous study that combined in situ X‐ray synchrotron with compressional and shear wave velocity measurement, the boundaries of the region of α → ω phase coexistence are constrained in Zr to be 4–8 GPa. The Ti result will be valuable for constraining its boundary when such in situ velocity measurement becomes available for Ti as well.

Filtered cathodic vacuum arc deposition of tetrahedral amorphous carbon thin films on surgical blades and its corrosion resistance in phosphate buffer solution (PBS) at pH 7.4

Surgical blades are prone to corrosion in a body fluid environment, increasing the risk of surgical infection and inflammation. In this paper, the ta-C thin films was deposited on surgical blades by filtered cathode vacuum arc (FCVA) method. Modern analytical methods such as SEM, Raman, surface profiler and electrochemical corrosion were used for the test and analysis. The results show that the corrosion potential and corrosion current density of uncoated surgical blades are −507 mV and 2.43 μA/cm2 during surgery operation in a simulated human environment (pH 7.4 PBS solution), and the corrosion potential of the ta-C thin films surgical blades immersed in 0.25 h, 0.5 h and 1 h are −395 mV, −431 mV, −445 mV, and the corrosion current density are 1.11 μA/cm2, 1.46 μA/cm2, 1.58 μA/ cm2. The results show that the ta-C thin films surgical blades are excellent corrosion resistance during surgery operation in a simulated human environment. SEM shows that the ta-C thin films surgical blades have a smooth surface with a compact and uniform films structure, and the thicknesses of the ta-C thin films and Ti transition layer are 2.2 µm and 2.4 µm respectively. The surface profiler shows that the average roughness of the surgical blades and the ta-C thin films surgical blades are 295.979 nm and 477.417 nm. Raman shows that ta-C thin films is of high purity, without any impurity phase, and does not cause other adverse reactions during surgery operation.

The Structure and Mechanical Properties of the Aging Shape-Memory Ti49Ni51 Alloy after Thermomechanical Treatment

The effect of thermomechanical treatment on the structure and phase transitions of the aging shape-memory Ti–51 at % Ni alloy has been studied. Mechanical tensile tests were performed in combina-tion with optical and electron microscopic and X-ray diffraction studies. An ultrafine grained (UFG) struc-ture was created in the alloy by multipass-rolling plastic deformation and further annealing. It was established for the alloy to have a high level of mechanical properties (ultimate tensile strength up to 1550 MPa at a rela-tive elongation of more than 20%) owing to a highly disperse phase of precipitation with the formation of an UFG structure due to recrystallization.

Densification mechanism of Ti-Al-Nb alloys pressurelessly sintered from Al-Nb master alloy powder for cost-effective manufacturing

Pressureless sintering is a cost-effective method to fabricate shaped Ti-Al-Nb alloy components in the aerospace industry. However, the sintering pores in the Ti-Al-Nb alloys led to inferior mechanical properties when using elemental Al powder as the raw material. By completely replacing the Al powder with the Al-Nb master alloy powder, the pores were substantially reduced in the pressurelessly sintered Ti-22Al-17.5Nb (at%) alloy, accompanied by the improvement of the tensile strength. We investigated the densification mechanisms by implementing the isothermal quenching experiments at 500–1200 °C. In the Ti/Al/Nb compact, the pores originated from the melting of Al and the Kirkendall effect at the interfaces of the Ti3Al and Nb particles. The transitions of Ti + 3Al → TiAl3 and α2 → B2 determined the porosity of the sintered alloy. In the Ti/Al-Nb/Nb compact, the Kirkendall pores at the Ti/Al3Nb interfaces were reduced since the diffusion of Al in Ti was retarded. The accelerated diffusion of Nb in Ti3Al suppressed the Kirkendall effect at the Nb/Ti3Al interfaces and promoted the formation of the B2 phase. The ripening of the B2 grains further contributed to the densification of the sintered alloy.

Influence of Heating and Cooling on the Isothermal β → ω Transition in Ti–22Nb–6Zr Alloy

Influence of Heating and Cooling on the Isothermal β → ω Transition in Ti–22Nb–6Zr Alloy

Strain induced structural phase transition and compositional dependent magnetic phase transition in Ti doped Bi0.80Ba0.20FeO3 ceramics

Bi0.80Ba0.20Fe1-xTixO3 (0≤x≤0.10) samples are prepared using solid state reaction technique. Bi3+ site is replaced with 20 % Ba2+ which induced structural modification from rhombohedral to pseudo cubic accompanied by the creation of oxygen vacancies owing to the charge reimbursement. Fe3+ site is replaced with different concentrations of Ti4+ keeping Ba content fixed. All the samples exhibited similar morphology and no significant variation in grain size is observed by substituting Ti at Fe site. All of the samples exhibited ferromagnetic behavior, which is ascribed to the destruction of spiral spin structures and changes in super-exchange interaction strength caused by variations in bond lengths of Fe–O and Fe–O–Fe. The decrease in magnetization with increasing Ti concentration is due to magnetic moment dilution caused by non-magnetic Ti4+. An anomalous trend in magnetization is observed for magnetic measurements at low temperature (77 K) where structural transformation from ferromagnetic to diamagnetic behavior was noted for 10% Ti content. Further, because of the incorporation of Ti4+, an improved dielectric property was observed due to increase in resistivity and decrease in the defect concentration (oxygen vacancies). In the present study, it was concluded that optimum concentration of Ba2+ (20%) and Ti4+ co-doped BiFeO3 systems have shown enhanced multiferroic properties at room temperature.

Electronic Nature Transition and Magnetism Creation in Vacancy-Defected Ti2CO2 MXene under Biaxial Strain: A DFTB + U Study.

The structural, electronic, and magnetic properties of vacancy defect in Ti2CO2 MXene and the effect of strain have been investigated using the density functional tight-binding (DFTB) approach including spin-polarization with Hubbard onsite correction (DFTB + U). The band gap of pure Ti2CO2 is ∼1.3 eV, which decreases to ∼0.4 and ∼1.1 eV in the case of C- and O-vacancies, respectively, i.e., the semiconducting behavior is retained. In contrast, Ti2CO2 undergoes semiconductor-to-metal transition by the introduction of a single Ti-vacancy. This transition is the result of introduced localized states in the vicinity of the Fermi level by the vacancy. Both Ti- and O-vacancies have zero net magnetic moments. Interestingly, the nonmagnetic (NM) ground state of semiconducting Ti2CO2 turns into a magnetic semiconductor by introducing a C-vacancy with a magnetization of ∼2 μB/cell. Furthermore, we studied the effect of strain on the electronic structure and magnetic properties of Ti-, C-, and O-vacant Ti2CO2. The nature of the band gap in the presence of single O-vacancy remains indirect in both compression and tensile strain, and the size of the band gap decreases. Compression strain on Ti-vacant Ti2CO2 changes metal into a direct semiconductor, and the metallic character remains under tensile biaxial strain. In opposition, a semiconductor-to-metal transition occurs by applying a compressive biaxial strain on C-vacant Ti2CO2. We also find that the magnetism is preserved under tensile strain and suppressed under compression strain on VC-Ti2CO2. Moreover, we show that double C-vacancies maintain magnetism. Our findings provide important characteristics for the application of the most frequent MXene material and should motivate further investigations because experimentally achieved MXenes always contain point defects.

Influence of heating and cooling routes on the isothermal β → ω transition in Ti–22Nb–6Zr alloy

The influence of heating and cooling routes prior to the Ti–22Nb–6Zr (at.%) shape memory alloy ageing on the intensity of the isothermal ωiso phase formation in the temperature range from 250 to 350 °C for 1 and 3 h was studied by X-ray diffraction. It was shown that for intensive ωiso phase formation, the most efficient scheme for entering the ageing interval includes rapid water cooling to the room temperature from the annealing temperature of 600 °C and subsequent rapid heating to the ageing temperature of 300 °C. All other schemes used for entering the aging interval including slow cooling and/or heating do not lead to the formation of any X-ray identifiable ωiso phase amount. Whereas, the β → ωiso transition in the temperature range from 250 to 350 °C has a pronounced C-shaped kinetics with a maximum at 300 °C. When aged in the entire range of t = 250÷350 °С, the alloy features higher durability and hardness compared to the initial state. Moreover, the hardness gradually increases with an increase in the ageing temperature from 250 to 300 °C and remains constant in the temperature range of t = 300÷350 °С. The β phase lattice parameter of the Ti–22Nb–6Zr alloy remains unchanged over the entire aging temperature range of 250–350 °C, which indicates the absence of noticeable diffusion element redistribution in the solid solution during the ωiso phase formation. The ωiso phase formed during the Ti–22Nb–6Zr alloy ageing over the entire temperature range of t = 250÷350 °С has the ratio сω /аω = 0.613 ± 0.002, which is similar to the сω /аω ratio for the shear-type athermal ωath phase, which in turn further emphasizes the identity of these two phase varieties.

Observation of a large magnetocaloric effect and suppressed transition in Ti doped Ni-Co-Mn-Sn ribbons upon annealing

We report the presence of austenite and its magnetostructural transition to martensite resulting in a large magnetocaloric effect in Ti doped Ni-Co-Mn-Sn textured ribbons. The evolution of the microstructure, micro-texture and the dynamics of the magnetostructural transition were studied for the as-spun and annealed Ni41.5Ti0.5Co9Mn39Sn10 ribbons. The as-spun ribbons revealed the evolution of a cubic superstructure of B2 ordering at room temperature, which is the characteristic of the austenite phase. The as-spun ribbons possess a strong preferred orientation at room temperature wherein, the< 100 > ║ND fiber texture is the dominant contribution at 90.2%. The austenite is ferromagnetic in nature and undergoes a magnetostructural transformation to weak magnetic martensite at 283.4 K. A large value of the isothermal entropy change of 6.62 J/kg/K, relative cooling power of 114.52 J/kg and an adiabatic temperature change of – 2.6 K have been calculated for a relatively low magnetic field change of 2 T. The annealing and quenching of the ribbons led to the grain growth as well as an overall suppression of the magnetostructural transformation. The austenite phase showed an overall enhancement in its magnetization when field cooled down to low temperatures of 4 K. The presence of strain glass clusters generated in the B2 lattice during the quenching process could be accounted for the observed behavior.

Study on Surface Properties of Unalloyed Copper Implanted with Different Transition Metal ions

Copper is widely used in Integrated Circuits and electronic components. Its corrosion performance and service performance have been paid much attention. We implanted Ti, Cr, Fe, Ni, Zn and other fourth period transition metal ions into unalloyed copper. After that, zeta potential test, electrochemical test and density functional theory calculation were used to study the surface properties of the implanted samples. We found that for copper samples, the zeta potential of implanted samples is related to the type of implanted transition metal ions, that is, the charge state at the solid-liquid interface is related to the type of implanted ions. We use density functional theory calculations to explain this change in surface properties of metal samples before and after ion implantation. We find that the d-band center of the transition metal has a similar trend to zeta potential.

Vibrational Entropy of Crystalline Solids from Covariance of Atomic Displacements.

The vibrational entropy of a solid at finite temperature is investigated from the perspective of information theory. Ab initio molecular dynamics (AIMD) simulations generate ensembles of atomic configurations at finite temperature from which we obtain the N-body distribution of atomic displacements, . We calculate the information-theoretic entropy from the expectation value of . At a first level of approximation, treating individual atomic displacements independently, our method may be applied using Debye–Waller B-factors, allowing diffraction experiments to obtain an upper bound on the thermodynamic entropy. At the next level of approximation we correct the overestimation through inclusion of displacement covariances. We apply this approach to elemental body-centered cubic sodium and face-centered cubic aluminum, showing good agreement with experimental values above the Debye temperatures of the metals. Below the Debye temperatures, we extract an effective vibrational density of states from eigenvalues of the covariance matrix, and then evaluate the entropy quantum mechanically, again yielding good agreement with experiment down to low temperatures. Our method readily generalizes to complex solids, as we demonstrate for a high entropy alloy. Further, our method applies in cases where the quasiharmonic approximation fails, as we demonstrate by calculating the HCP/BCC transition in Ti.