Ti Metal Research Articles

Atomic catalysis meets heterostructure synergy: Unveiling the trifunctional efficacy of transition Metal@WS2/ReSe2

Integrating and advancing renewable energy storage and conversion technologies such as water splitting and rechargeable air-based batteries face significant challenges in finding appropriate catalysts that offer both high activity and low cost. This paper successfully designed efficient, cost-effective, and eco-friendly catalysts that meet the requirements for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) catalytic activity by employing two-dimensional (2D) transition metal dichalcogenides (TMDs) interface engineering combined with a single-atom doping strategy. First, the heterostructure was constructed, and its optimal layer spacing (3.13 Å) was determined by calculating the most negative binding energy. These materials were theoretically evaluated using density functional theory (DFT), demonstrating that transition metal (TM) can all be firmly attached to the S1 site of the WS2/ReSe2 Z-scheme heterostructure with favorable binding energies and excellent electronic properties. By comparing the catalysts doped with different metals (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn), the three functional catalysts with the best performance were finally selected: Mn@WS2/ReSe2, Ni@WS2/ReSe2, and Cu@WS2/ReSe2. In particular, Mn@WS2/ReSe2 exhibited exceptional promise as multifunctional catalysts, with overpotentials for the HER/OER/ORR of 0.05/0.29/0.35 V, respectively. The superior catalytic performance of this WS2/ReSe2 Z-scheme heterostructure was attributed to the introduction of TM atoms and the synergistic interaction between rhenium and the TM atoms. This interaction facilitated more efficient electron transfer between the catalyst and the reactants, enhancing the overall catalytic activity. This research is a successful attempt to combine interface engineering with single-atom catalysis (SACs). It provided valuable insights into the design of next-generation multifunctional electrocatalysts, offering a novel approach to address the growing energy demands in an environmentally benign and economically viable way.

Optimized Design of Quinary High-Entropy Transition Metal Carbide Ceramics Based on First Principles

In this paper, we developed models for 21 quinary high-entropy transition metal carbide ceramics (HETMCCs), composed of carbon and the transition metals Ti, Zr, Mo, V, Nb, W, and Ta, employing the Special Quasirandom Structures (SQS) method. We investigated how the transition metal elements influence lattice distortion, mixing enthalpy, Gibbs free energy of mixing, and the electronic structure of the systems through first-principles calculations. The calculations show that 21 systems can form a stable single phase, among which (TiMoVNbTa)C5, (ZrMoNbWTa)C5, and (MoVNbWTa)C5 exhibit superior stability. The formation energy and migration energy of carbon vacancies in systems with strong single-phase stability were calculated to predict their radiation resistance. The formation energy of carbon vacancies is closely related to the types of surrounding transition metal elements, with values ranging between the maximum and minimum formation energies observed in binary transition metal carbides (TMCs). The range of migration energy for carbon vacancies is wider than that observed in TMCs, which can hinder their long-range migration and enhance the radiation resistance of the materials.

Theoretical Study of Gas Sensing toward Acetone by a Single-Atom Transition Metal (Sc, Ti, V, and Cr)-Doped InP3 Monolayer

Theoretical Study of Gas Sensing toward Acetone by a Single-Atom Transition Metal (Sc, Ti, V, and Cr)-Doped InP₃ Monolayer

Solid-Solution MXenes: Synthesis, Properties, and Applications.

ConspectusMXenes, among other two-dimensional (2D) materials such as graphene, hexagonal BN, transition metal dichalcogenides (TMDs), 2D metal-organic frameworks (MOFs), and covalent organic frameworks (COFs), are the fastest growing class discovered thus far. The general formula of MXenes is Mn+1XnTx, where M, X, and Tx represent an early transition metal (Ti, V, Nb, Mo, etc.), C and/or N, and the surface functional groups (typically, O, OH, F, Cl), respectively, and n can be between 1 and 4. MXenes as a class of materials have extraordinary properties, such as high electrical conductivity, nonlinear optical properties, solution processability, scalability and ease of synthesis, redox capability, and tunable surface properties, among others; the specific properties, however, depend on their chemistry. Since the initial report of the first MXene in 2011, the research community has primarily focused on Ti3C2Tx, and the amount of research work to investigate its synthesis and properties has increased exponentially over the years. In materials science, alloying is a useful way of synthesizing new materials to improve the properties of a class of materials. Advancement of steel and synthesis of inorganic semiconductors can be regarded as some of the major historical advancements in the concept of alloying. Thus, just one year after the initial report of MXenes, the first solid-solution MXene, (TiNb)2CTx, was reported, which demonstrates the inherent chemical tunability of this class of materials.MXenes have two sites for compositional variation: elemental substitution on both the metal (M) and carbon/nitrogen (X) sites, presenting promising routes for tailoring their properties. X-site solid-solutions include carbonitride MXenes and are the least studied class of MXenes to date. Comparatively, multi-M MXenes have acquired significant attention, leading to the extreme example of high-entropy solid-solution MXenes. By using multiple M elements, a significant expansion of the structural and chemical diversity is possible, giving rise to novel chemical, magnetic, electronic, and optical properties that cannot be accessed by single-M MXenes. Solid-solution MXenes represent the largest and most tunable class of MXenes; solid-solution MXenes are those that have multiple metals that are randomly distributed on their M sites with no distinct chemical ordering. Using multiple M elements in MXenes, it is possible to synthesize novel MXene structures that cannot be produced otherwise, such as M5X4Tx MXenes. Based on their chemistry, it is possible to rationally control the electronic, optical, mechanical, and chemical properties in a way that no other class of MXenes can. In some cases, the resultant property is linearly related to the chemistry, such as the electrical conductivity, while in other cases the properties are nonlinear or emergent: optical properties, enabling these MXenes to fulfill roles that no other MXene, or 2D material, can.In this Account, we discuss the recent progress in the synthesis, properties, applications, and outlook of solid-solution MXenes. Importantly, we demonstrate how multi-M solid-solutions can be used to tailor properties for specific applications easily.

Spatial Distribution of Critical Metals and Chemostratigraphy in Co‐Rich Ferromanganese Nodules in the Northwestern Pacific Ocean

AbstractFerromanganese nodules are important marine storehouses for critical metals and windows for changing oceans. Although advanced in situ analytical techniques have been applied to visualize the elemental distribution in the nodule cross‐sections, their spatial distribution remains largely uncertain. This study addresses this gap by employing micro X‐ray fluorescence mapping of parallel nodule cross‐sections to delineate the spatial distributions of critical metals (Mn, Fe, Co, Ti, Ni, and Cu) in three Co‐rich ferromanganese nodules from the northwestern Pacific Ocean. The 10‐layer Os isotopic compositions of one nodule closely align with the well‐documented marine Os isotope evolution of seawater, providing a chronological framework and a maximum age of ∼36 Ma for these nodules. Three concentric chemostratigraphic layers, labeled L1, L2, and L3, were identified from the inside out, based on microscopic structures and the distributions of critical metals. The early growth stage was marked by Mn‐rich, Si‐rich, and high Mn/Fe ratios, suggesting a diagenetic‐driven process attributed to high paleoproductivity conditions because of the low latitude of the study area at that time. The subsequent growth stages are all hydrogenetic in origin to be rich in Fe, Co, and Ti with low Mn/Fe ratios. The apparent detritus present during the second growth stage of the nodules may correspond to the stronger bottom currents in the early Miocene. The final mineralization stage indicates a more stable environment with diminished bottom current activity, leading to the formation of a dense, laminar hydrogenetic layer.

Direct Synthesis of Ti-Al Compound Powders by Electrolysis in Molten LiCl-KCl

The deposition potential difference between Ti and Al is only 70 mV. The deposition reaction of Ti-Al compound happens at the potentials slightly higher than that of metallic Ti and Al. Through galvanostatic electrolysis of mixture solution of Al and Ti ions, all kinds of titanium aluminides can be directly synthesized. The composition of the product compound can be selected through adjusting the combination of Ti and Al ions in the electrolyte.

Novel Synthesis Route of Plasmonic CuS Quantum Dots as Efficient Co-Catalysts to TiO2/Ti for Light-Assisted Water Splitting.

Self-doped CuS nanoparticles (NPs) were successfully synthesized via microwave-assisted polyol process to act as co-catalysts to TiO2 nanofiber (NF)-based photoanodes to achieve higher photocurrents on visible light-assisted water electrolysis. The strategy adopted to perform the copper cation sulfidation in polyol allowed us to overcome the challenges associated with the copper cation reactivity and particle size control. The impregnation of the CuS NPs on TiO2 NFs synthesized via hydrothermal corrosion of a metallic Ti support resulted in composites with increased visible and near-infrared light absorption compared to the pristine support. This allows an improved overall efficiency of water oxidation (and consequently hydrogen generation at the Pt counter electrode) in passive electrolyte (pH = 7) even at 0 V bias. These low-cost and easy-to-achieve composite materials represent a promising alternative to those involving highly toxic co-catalysts.

Enhanced adhesion and corrosion resistance through the modulation of a metallic Ti underlayer thickness

In this investigation, TiCN/TiN thin solid film was selected as a protective coating and deposited onto AZ31 alloy through reactive magnetron sputtering. To mitigate the potential failure resulting from the significant physical disparity between the ceramic film and the metal substrate, a Ti thin film was employed as a base layer. Following the deposition process, an analysis was conducted on the structural features, residual stress, fracture morphology, adhesion strength, and corrosion characteristics of the film/substrate system utilizing X-ray diffraction, scanning electron microscopy, scratch testing, and electrochemical workstation. The findings indicate that the incorporation of a Ti metallic underlayer significantly improves the adhesion and corrosion resistance of the TiCN film. However, when the thickness of the Ti layer surpasses 0.37 μm (deposition of 15 min), it leads to the formation of a distinct columnar crystal microstructure, increased residual stress, and diminished adhesion and corrosion resistance. Additionally, this study delves into the corrosion failure mechanisms in a chloride environment and explains the principles of residual stress measurement through XRD.

In-situ synthesis of 3D TiO2 microspheres on Ti mesh to enhance photoelectrochemical water splitting

Much attention has been focused on the fabrication of TiO2 microspheres due to their excellent properties and attractive potential in many fields. Here, undoped 3D hierarchical TiO2 microspheres (TMS) were synthesized in situ on Ti mesh using a hydrothermal method by varying NaOH concentration, reaction time and temperature. The 3D TMS grown along the surface of the woven wires of the Ti meshes, using the metal Ti meshes as a substrate, which resulted in improved conductivity. Meanwhile, the original Ti mesh with the macroporosity (due to the 15 % open area of the mesh) can act as fast proton mass diffusion. As a result, the flexible TMS-Ti photoelectrodes exhibit an excellent current density of 1.63 mA/cm2 at a potential of 1.23 V (vs Ag/AgCl). Therefore, the in situ synthesis of TiO2 microspheres on Ti mesh is highly desirable for flexible devices.

Strategies and Mechanisms of First-Row Transition Metal-Regulated Radical C-H Functionalization.

Radical C-H functionalization represents a useful means of streamlining synthetic routes by avoiding substrate preactivation and allowing access to target molecules in fewer steps. The first-row transition metals (Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) are Earth-abundant and can be employed to regulate radical C-H functionalization. The use of such metals is desirable because of the diverse interaction modes between first-row transition metal complexes and radical species including radical addition to the metal center, radical addition to the ligand of metal complexes, radical substitution of the metal complexes, single-electron transfer between radicals and metal complexes, hydrogen atom transfer between radicals and metal complexes, and noncovalent interaction between the radicals and metal complexes. Such interactions could improve the reactivity, diversity, and selectivity of radical transformations to allow for more challenging radical C-H functionalization reactions. This review examines the achievements in this promising area over the past decade, with a focus on the state-of-the-art while also discussing existing limitations and the enormous potential of high-value radical C-H functionalization regulated by these metals. The aim is to provide the reader with a detailed account of the strategies and mechanisms associated with such functionalization.

Carbochlorination of YOCl for Synthesis of YCl3

AbstractAs the production of high-quality titanium (Ti) metal increases significantly, the generation of low-quality Ti scraps increases and exceeds the demand for current cascade recycling in ferrous metallurgy. Therefore, the development of an upgrading recycling technology, in which scraps are refined and reutilized, is required. The magnesium (Mg) deoxidation assisted by the formation of oxychlorides of rare earth metals is currently considered a promising process for upgrading recycling technology, during which YOCl is formed as a byproduct. In this study, we investigate the synthesis and separation of YCl3 from YOCl via carbochlorination at 973 and 1073 K and confirmed that YCl3 can be regenerated from YOCl at a high conversion rate (82.7 pct at maximum). YCl3 was also formed even in the presence of MgCl2; however, MgCl2 decreased the conversion rate (49.8 pct at minimum). The conversion rate in the temperature region where YCl3 is a liquid (1073 K) was lower than that in the temperature region where YCl3 is a solid (973 K). Therefore, an operation with temperature cycling, in which YCl3 is formed at a temperature where YCl3 is a solid and then the temperature is increased to a temperature where YCl3 is a liquid to drain the molten mixed salt, is efficient.

Influence of sources and atmospheric processes on metal solubility in PM2.5 in urban Guangzhou, South China

Water-soluble metals exert a significant influence on human and ecosystem health. In this study, a comprehensive investigation was undertaken to elucidate the solubilities of metals in PM2.5 and potential influencing factors during the dry season of 2019–2020 in urban Guangzhou, South China. The observed average solubility was <20 % for Al, Fe, Sn, and Ti; 20–40 % for V, Cr, Sb, Pb, and Ni; 40–60 % for Ba and Cu; and 60–80 % for Zn, As, Se, Cd, and Mn. Metals (Al, Ti, and Fe) originated from crustal sources (e.g., soil dust) have much lower solubilities than those (Mn, Zn, As, Se, Cd, and Ba) from fossil fuel combustion sources (e.g., traffic emission, coal combustion), suggesting the dominant role the metal sources played on solubility. Enhanced solubilities of Cu, As, Se, Cd, Sn, Sb, and Pb were associated with aerosol acidity, while those of V, Cr, Mn, Ni, Zn, and Ba were linked to organic acid complexation. For the three crustal metals, the solubilities of Al and Ti primarily depended on aerosol acidity, whereas the solubility of Fe depended on both aerosol acidity under pH < 2 conditions and organic acid complexation under pH > 2 conditions. These findings underscore the primary influence of inherent properties of the metals on their solubility and reveal the varying impacts of atmospheric physicochemical processes, with changes in their solubilities being <10 % for Cd, Sn, Sb, and Pb, 10–20 % for Cu, Cr, Mn, Ni, and Ba, and 20–30 % for As, Se, and Zn.

Molten salt synthesis of Ti-Si-C coating on SiC particles and hot pressing of the prepared powders

SiC particles coated with Ti-Si-C layer were prepared by the molten salt synthesis method using NaCl-KCl eutectic mixture as the reaction medium and Ti metal powder as the Ti source. The synthesis was conducted under static argon atmosphere at 900 °C for 1–3 h. The post-synthesis treatment included dissolution of salts in hot water, followed by ultrasonic dispersion and sedimentation procedures. The thickness of the Ti-Si-C layer varied from 0.1 to 0.9 μm as the ratio of Ti to SiC components in the starting mixture changed from 0.05 to 0.4. The layer contained mainly nanocrystalline Ti5Si3, minor phases were TiC and Ti3SiC2. The as-prepared powders were hot pressed under 30 MPa at 1700 °C. The densification behavior of the samples during hot pressing as well as changes both in phase composition and in microstructure were studied. The flexural strength of the hot-pressed samples increased with an increase in the Ti:SiC molar ratio, giving the value as high as 213 ± 20 MPa for the sample with Ti/SiC = 0.4.

Microplastic assessment in aquaculture feeds: Analyzing polymer variability across commercial fishfeeds from three continents

This study analysed ten widely used commercial fishfeeds in aquaculture from six countries spanning three continents to assess microplastic (MP) contamination. MPs with an average abundance of 1130 ± 259.07 particles/kg and an average length of 2.64 ± 0.62 mm ( ± SE) were found in aquaculture feeds, with fibres (85 %) and fragments (15 %). The majority of these MPs were black. The abundance of MPs varied among the samples, with the highest in feed SP (26 %), followed by IF, GA, ELS, NT, EW, TB, GR, VR, and the least in HCF (3 %). Polymers identified consisted of Polyethylene terephthalates (PET, 20 %), Polyamide (PA, 30 %), Polymethyl methacrylate (PMMA), Polyurethane (PU), and Polystyrene (PS) with 15 % each, and Polypropylene (PP, 5 %). SEM-EDX analysis of fibres showed flakes, cracks, and pits and the presence of heavy metals Ni, Cu, Zn, Cr, Au, Hg, Cd, Ti, and Pb. Additionally, some fragments contained Nb (Niobium) alongside the naturally occurring elements. The Polymer Hazard Index (PHI) for the polymers in ten feeds was calculated, and nine were in the highly hazardous category (IV and V) with PHI values ranging from 400–394825. The work showcases the graveness of MPs in fishfeeds and advocates control measures to curtail MPs in fishfeeds for sustainable aquaculture production.

First-principles study on the adsorption of gas molecules on Fe, Ti-Doped silicene

In this study, we employ first-principles calculations to investigate the geometric and electronic properties of intrinsic silicene and silicene doped with metal elements Fe and Ti. We analyze the adsorption performance of five gas molecules (CO, SO2, H2S, CH4 and H2CO) on the surfaces of these two materials. For each gas molecule, we determine the optimal adsorption site and calculate parameters such as adsorption distance, adsorption energy, charge transfer, recovery time, and density of states to understand the adsorption mechanism. Our study reveals that the adsorption affinity of the selected gas molecules on intrinsic silicene is relatively weak. The distance between the gas molecules and the intrinsic silicene surface is relatively large, and no stable chemical bonds are formed between them. In contrast, Fe and Ti-doped silicene exhibit relatively higher stability, with the adsorption energies of the gas molecules on their surfaces increasing obviously. The Titanium doping exerts a considerable influence on increasing the band gap and the adsorption energy of silicene compared with the intrinsic one, thus the whole structure is able to reveal semiconductors’ properties. In Ti-doped silicene structures, the band gap opens, exhibiting semiconductor properties, and the adsorption energies increase relative to intrinsic silicene. These results indicate that the doping of Fe and Ti atoms enhances the adsorption performance of silicene materials, providing theoretical reference for the gas sensing performance of Fe and Ti-doped silicene materials and the semiconductor performance of Ti-doped silicene.

Constructing and Investigating a Ceria-Based Electro-Chemo-Resistivity Switch

Coupling between an electrochemical reaction and a functional material property has been termed electro-chemo-X, or EC-X, where X can refer to mechanical, optical, magnetic, or thermal properties. Recently, our group has demonstrated a two-terminal electro-chemo-mechanical (ECM) membrane actuator operating under ambient conditions and containing a Ce0.8Gd0.2O1.9 (20GDC) solid electrolyte (SE) layer sandwiched between two Ti oxide/Ce0.8Gd0.2O1.9 (Ti-GDC) nanocomposite thin films. Reducing one nanocomposite film while oxidizing the other was observed to produce reversible volume change thereby driving actuator operation. Here, we use the same electrolyte and nanocomposite layers to further explore the EC-X effect: we present, as proof-of-concept, a functioning, three-terminal, thin film based EC-electrical switching device operating at room temperature.The stacked lamellar structure which comprises the device (Figure 1) was fabricated by first depositing, using magnetron sputtering, a ~200nm thick layer of Ti metal on a sapphire substrate. This was followed by patterning with photolithography and etching, using a commercial, buffered oxide etch solution, thereby creating a 1mm wide channel. The resulting bottom electrode pair ("source" and "drain"), which could be temporarily shorted together when necessary, were subsequently covered by the WB/SE/RV stack, where the same co-sputtered, ~200nm thick Ti-GDC nanocomposite (<40nm grain size; 39at% Ti) was used for both the working body (lower: WB) and the reservoir (upper: RV) layers; a ~400nm thick 20GDC layer served as the SE. Upon WB deposition, the 1mm channel between the source and drain electrodes was filled with the nanocomposite material. The upper electrical contact, a ~200nm Ti layer, covered the RV, and using the same photolithography and etching process already described, the top "gate" electrode was defined. To avoid oxidation of the ion reservoir (RV) surface by atmospheric oxygen during device operation, a ~500 nm thick Ta-oxide layer was deposited by reactive magnetron sputtering and patterned by lift-off techniques.We find that following two hours application of -/+ 6V bias between the "gate" and (temporarily shorted) "source" / "drain" electrodes under ambient conditions, the average change in ohmic resistance of the WB in the 1mm channel upon reversal of electrode bias was determined, by cyclic voltammetry between the source and drain electrodes, to be 6.5 ±1.8Gohm with statistical uncertainty based on at least 3 cycles, 5 samples. Negative "gate" bias produced the lower resistance values. The low resistance state decayed during approx. 24 hours, as monitored by cyclic voltammetry. Raising the temperature above ambient (333K) further reduced resistance. We interpret these observations as follows: Negative bias voltage application to the "gate" produces a gradient of the chemical potential of diffusing oxygen ions at the SE-WB interface. This gradient leads to the injection of ions into the WB, thereby promoting an electrochemical oxidation reaction. The nanocomposite in the 1mm channel decays from the more highly conductive state during approximately twenty-four hours. Reversing the bias polarity extracts ions from the WB, with the opposite results. To complement the findings of the E-field promoted oxidation, we performed annealing at 633K for 23 hours in air of a device which lacked the SE/RV/"gate" electrode/Ta-oxide layers, i.e. the WB was uncovered. We observed an increase of two orders of magnitude in the conductivity of the nanocomposite in the 1mm channel, which then relaxes with time. As a control, the same thermal treatment was conducted under vacuum. In this case no change was observed in channel conductivity.A possible explanation for how oxidation increases the Ti-GDC nanocomposite conductivity may be found in a suitable variant of the space charge model [1, 2]. We note that nanocrystallinity introduces such a high density of interfaces/grain boundaries that total conductivity may become interfacially controlled. Grain boundaries in doped ceria lack long range order and are relatively rich in oxygen vacancies (VO) and Ce3+, which, along with a space charge zone which forms for charge neutrality, produce a blocking effect for ion conduction. Oxidation of Ce3+ => Ce4+ leads to a lowering of total real charge, causing the spatial extent of the space charge zone to shrink as well. Finally, this succeeds in lowering the potential barrier for ion diffusion across the grain boundary, which increases the overall conductivity. Reduction of the Ti-GDC nanocomposite produces the opposite effect.[1] S. K. Kim, S. Khodorov, I. Lubomirsky, S. Kim, Phys Chem Chem Phys 2014, 16, 14961, https://doi.org/10.1039/c4cp01254b[2] S. Kim, J. Maier, J. Elecrochem. Soc. 2002, 149, J73, https://doi.org/10.1149/1.1507597 Figure 1

Timed Thermodynamic Process Model Applied to Submerged Arc Welding Modified by Aluminium-Assisted Metal Powder Alloying

An EERZ (effective equilibrium reaction zone) model was applied to the modified SAW (submerged arc welding) process to simulate the SAW process metallurgy in the gas-slag-metal reaction system. The SAW process was modified by adding Al as a de-oxidizer with alloying metal powders of Cr, Cu, and Ti. The static gas-slag-metal equilibrium model can accurately calculate the weld metal oxygen content (ppm O) for conventional SAW but not for the modified SAW process. The static equilibrium model overpredicts the reaction of Al. EERZ model runs were made for 2000–2500°C because this is the reported temperature range in the SAW arc cavity. The weld metal composition was adequately calculated, especially the weld metal ppm O, at the following effective equilibrium temperatures: 2400°C for Al-Cr additions, 2200°C for Al-Cr-Cu additions, and 2000°C for Al-Cr-Cu-Ti additions. Model results show that Ti metal powder can serve a de-oxidizer role in the presence of Al, resulting in Ti loss to the slag. Ti is also lost to the gas phase as TiF3(g) and TiF2(g) compared to little loss of Cr to the gas phase as Cr(g) and CrO to the slag phase.

Experimental study of thermal transport across metal/h-BN interfaces: Comparison with metal/graphite interfaces

The continuing miniaturization of layered material electronics highlights the increasingly significant role of interfacial thermal conductance (G) in the efficient nanoscale heat dissipation in these electronics. Despite its importance, the mechanisms of thermal transport across the interfaces of layered materials and the underlying substrate remain unclear. In this work, we comprehensively investigate the interfacial thermal and phonon transport across layered-material interfaces through our ultrafast pump-probe measurements and detailed calculations on G for the interfaces of hexagonal boron nitride (h-BN), one of the most promising layered materials. We first experimentally measure Gc for interfaces between four different metals (Al, Pd, Au and Ti) and h-BN along c-axis using time-domain thermoreflectance (TDTR) from 80 to 300 K. We successfully achieve high accuracy of our measurements with uncertainty <10 % through using the carefully chosen high modulation frequency (15.6 MHz) and relatively large laser spot size (22.5 μm). We find that the measured Gc for interfaces between metals (except Al) and (100) plane of h-BN is lower than that of metal/graphite interfaces, while Gc of Al/h-BN is comparable to that of Al/graphite interfaces. Furthermore, together with our proposed anisotropic model and the diffuse mismatch model (DMM), we determine the transmission probability for the various metal/h-BN interfaces and find that the strong bonding strength enhances the phonon transmission across Ti/h-BN or Ti/graphite interfaces. Finally, we predict the orientation-dependent thermal conductance (i.e., the different interfacial thermal transport along c-axis (Gc) and in-plane (Gab) crystallographic orientations) for both metal/h-BN and metal/graphite. We find Gab between metals and (001) plane is up to 2–3 times higher than Gc. This can be attributed to the highly anisotropic elastic properties in the h-BN and graphite. This work provides important insight into the phonon transmission mechanisms across metal/h-BN interfaces, and thus contributes significantly to the thermal management of layered material electronics.

Base Metals Induced Oxygen Migration and Adjustable Performance in Multifunctional Oxide Heterojunction Devices

AbstractThe chemical and electronic interactions at metal/oxide heterojunctions is pivotal in determining the electronic properties of oxide devices utilized in microelectronics, catalysis, and photovoltaic systems. In this study, interfacial oxidation migrations within a model heterostructure system, consisting of a La0.7Sr0.3MnO3 film overlaid by various metallic (Ti, Al, Cu, Ag, and Au) ultrathin layers are systematically investigated. It is experimentally demonstrated that at elevated deposition temperature, the oxygen‐active ultrathin overlayers of base metals such as Ti and Al significantly derive oxygen from the underlying La0.7Sr0.3MnO3 film, inducing a perovskite to brownmillerite phase transition in the underlying functional oxide film. Conversely, no structural transitions are observed for La0.7Sr0.3MnO3 film when it is capped by noble metals (Au, Ag), which possess relative high oxidation formation energy. These observations are crucial for the development of novel crystalline and electronic architectures in metal/oxide heterostructures, offering a refined approach to modulate interfacial reactivity without compromising the functionality of oxide‐based heterojunction devices.

Growth of brookite TiO2 nanorods by thermal oxidation of Ti metal in air

Growth of brookite TiO2 nanorods by thermal oxidation of Ti metal in air