Transition Layer Research Articles

Enhancing electrical and thermal property of diamond-based Ta2N films through introducing a Ta transition layer

Diamond, renowned for its exceptional heat dissipation properties, stands out as an optimal substrate for tantalum nitride (Ta2N) film resistors. To fully exploit the high thermal conductivity of diamond, we introduce a thin tantalum (Ta) interlayer between the TaN thin film and the polished diamond substrate, aiming to strengthen their bond and enhance the interfacial thermal conductance. Comprehensive morphological and structural analyses, utilizing advanced techniques such as grazing incident X-ray diffraction (GI-XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS), were employed. Electrical properties were measured using a four-point probe, and thermal boundary conductance (TBC) between Ta2N and diamond was assessed through time-domain thermoreflection (TDTR), comparing scenarios with and without the Ta interlayer. Results demonstrate that the Ta interlayer facilitates tantalum carbide (TaxC) formation, improving adhesion and resulting in a remarkable 70 % increase in overall interface TBC. Moreover, the thin Ta interlayer positively influences the overall temperature coefficient of resistance (TCR) of the Ta2N film. Our strategic approach showcases enhanced adhesion and thermal performance, opening promising avenues for elevated functionality and reliability of Ta2N film resistors in high-temperature applications.

Nickel‐Manganese‐Based Layered Oxide for Sodium Ion Battery Cathode Materials

Sodium‐ion batteries (SIBs) have demonstrated significant potential as alternatives to conventional lithium‐ion batteries (LIBs) for modern grid and mobile energy storage applications, due to the abundant natural resources and low cost of sodium. Layered transition metal oxides (LTMOs) have attracted focused research attentions due to their high specific capacities, energy densities as well as the compatible preparation processes with those of LIBs cathode materials. Among these, Ni/Mn‐based LTMOs (NMLOs) are particularly noteworthy for their cost‐effectiveness and superior electrochemical performance, such as excellent capacity retention, voltage stability, high operating voltage and rate capability. In this review, we briefly introduce the synthesis methods of NMLOs, discuss the challenges, and summarize the solutions. The insights presented may contribute to the development of NMLOs based SIBs.

Heterogeneous microstructure of γ-irradiated pre-oxidized PAN fiber revealed by microfocus SR-SAXS reconstruction and molecular simulation.

The microstructure plays a crucial role in the manufacturing and application of polyacrylonitrile fibers, which serve as precursors for carbon fibers. Synchrotron radiation small angle x-ray scattering (SR-SAXS) is a non-destructive and precise technique for analyzing fiber structures. This study employed one-dimensional SR-SAXS mapping to extract key structural parameters such as periodicity, lamellae thickness, and the extent of amorphous regions, as well as the directional orientation in γ-irradiated, pre-oxidized polyacrylonitrile fibers. The analysis revealed a three-layered structure comprising a surface skin, a transitional layer, and a central core. Notably, the lamellar thickness exhibits a "U"-shaped distribution, while the long-period structures, amorphous regions, and orientational properties demonstrate a "wave-like" pattern. Within this structure, the skin exhibits a higher level of orientation, with the orientation decreasing progressively from the skin toward the core layer. The structure of the layered crystal was further corroborated by the morphological analysis. In addition, molecular simulations were performed to propose the mechanisms underlying the formation of this layered structure. This comprehensive investigation using SR-SAXS and one-dimensional mapping provides detailed insights into the microstructural and morphological characteristics of polyacrylonitrile fibers, which can inform future advancements in material processing and refinement techniques for the production of advanced fibers.

Pt thin-film resistance thermo detectors with stable interfaces for potential integration in SiC high-temperature pressure sensors

Due to the excellent mechanical, chemical, and electrical properties of third-generation semiconductor silicon carbide (SiC), pressure sensors utilizing this material might be able to operate in extreme environments with temperatures exceeding 300 °C. However, the significant output drift at elevated temperatures challenges the precision and stability of measurements. Real-time in situ temperature monitoring of the pressure sensor chip is highly important for the accurate compensation of the pressure sensor. In this study, we fabricate platinum (Pt) thin-film resistance temperature detectors (RTDs) on a SiC substrate by incorporating aluminum oxide (Al2O3) as the transition layer and utilizing aluminum nitride (AlN) grooves for alignment through microfabrication techniques. The composite layers strongly adhere to the substrate at temperatures reaching 950 °C, and the interface of the Al2O3/Pt bilayer remains stable at elevated temperatures of approximately 950 °C. This stability contributes to the excellent high-temperature electrical performance of the Pt RTD, enabling it to endure temperatures exceeding 850 °C with good linearity. These characteristics establish a basis for the future integration of Pt RTD in SiC pressure sensors. Furthermore, tests and analyses are conducted on the interfacial diffusion, surface morphological, microstructural, and electrical properties of the Pt films at various annealing temperatures. It can be inferred that the tensile stress and self-diffusion of Pt films lead to the formation of hillocks, ultimately reducing the electrical performance of the Pt thin-film RTD. To increase the upper temperature threshold, steps should be taken to prevent the agglomeration of Pt films.

Self-organization of the tribosystem under non-stationary conditions of friction from the standpoint of deformation-wave representations

Mechanisms of structural adaptation of contact surfaces and lubricating materials during friction with the dominance of deformation processes in tribocontact have been analyzed. The purpose of the work was to model the elastic-plastic properties of dissipative structures taking into account the anisotropic properties of the surface layers of the friction pairs and the boundary layers of the lubricating material. The modeling took into account the structural state of the latter formed due to heating and saturation with wear products, along with the physical and mechanical interaction of this layer with the outer surface of the part. An algorithm for determining the distributed tangent force along the length of the boundary layer of the lubricating material adjacent to the part has been developed based on the hypothesis of the wave-like state of the surface layer of the lubricating material on an absolutely flat (non-deformed) rough surface. Herein, under the action of tangent forces, the strip of lubricant is subject to horizontal compression and transverse movement. The distributed tangent stress along the length of the adjacency of the layer of densified lubricant to the part causes micro-slipping of the layer. Amplitude horizontal displacements of the boundary of the lubricant layer are determined when the beam-film is loaded with longitudinal stresses, which leads to partial disorientation of the film and loss of its originally rectilinear structured form, the transition of the lubricant layer to the state of the wave surface of a sinusoid shape. Also, a procedure for calculation of tangent forces causing the loss of elastic stability of the lubricant boundary layers resulting in the direct mechanical destruction of the lubricant boundary layer in the slipping zone of the contact surface is proposed based on the elastic-frictional interaction of this layer with the near-surface layer of the metal

Ca/Li Synergetic-Doped Na0.67Ni0.33Mn0.67O2 to Realize P2-O2 Phase Transition Suppression for High-Performance Sodium-Ion Batteries.

P2-type layered transition metal oxide Na0.67Ni0.33Mn0.67O2 is considered as a promising cathode for advanced sodium-ion batteries due to its high theoretical specific capacity. However, the P2-type cathode suffers severe P2-O2 phase transition during cycling process, resulting unsatisfactory cyclic stability and rate capability. Herein, a Ca/Li co-doped P2-type Na0.62Ca0.05Ni0.33Mn0.57Li0.10O2 (NCNMLO) cathode material was synthesized through a simple sol-gel method. With the synergistic effect of Ca-doping at Na sites and Li substitution at transition metal (TM) sites, the cathode achieves an excellent electrochemical performance due to the inhibited P2-O2 phase transition and improved ion diffusion with Na+/vacancy disordering arrangement. The NCNMLO cathode exhibits a good cyclic stability with 70.8% of capacity retention at 1 C after 200 cycles and excellent rate capability with 40.1 mAh g-1 at 20 C. The dual sites doping strategy provides an effective and simple approach for designing high-performance layered oxide cathode materials for sodium-ion batteries.

Impact of surface hydrophilicity on the ordering and transport properties of bicontinuous microemulsions.

Microemulsions (MEs) have many industrial applications, where recent developments have shown that MEs can be utilized for electrochemical applications, including potentially in redox flow batteries. However, understanding the structure and dynamics of these systems, including at a surface, is needed to direct and rationally control their electrochemical behavior. While bulk solution measurements have provided insight into their structure, their assembly at an interface also impacts the electron (to the electrode) and ion (across the surfactant) charge transfer processes in the system. To address this shortcoming, neutron reflectivity experiments and molecular simulations have been completed that document the near surface structure of a series of deuterated water (D2O)/polysorbate-20/toluene MEs on hydrophilic and amphiphilic surfaces. These results show that the microemulsions form complex layered structures near a hard electrode surface, where most layers are not purely one component. Decreasing the D2O concentration in the ME increases the number of and purity of the layers established on the solid surface. These lamellar-type layers transition from the surface to the bulk microemulsion as a series of mixed layers (i.e., containing oil, water, and surfactant) that are consistent with perforated lamellae. Additionally, these mixed lamellae appear to become more perforated with oil and water pathways on an amphiphilic surface. The purity and thickness of these layers will influence the accessibility of an electrode by redox active species, as well as ion transport required to satisfy the electroneutrality condition.

Topological Surface State Evolution in Bi2Se3 via Surface Etching.

Topological insulators are materials that have an insulating bulk interior while maintaining gapless boundary states against back scattering. Bi2Se3 is a prototypical topological insulator with a Dirac-cone surface state around Γ. Here, we present a controlled methodology to gradually remove Se atoms from the surface Se-Bi-Se-Bi-Se quintuple layers, eventually forming bilayer-Bi on top of the quintuple bulk. Our method allows us to track the topological surface state and confirm its robustness throughout the surface modification. Importantly, we report a relocation of the topological Dirac cone in both real space and momentum space as the top surface layer transitions from quintuple Se-Bi-Se-Bi-Se to bilayer-Bi. Additionally, charge transfer among the different surface layers is identified. Our study provides a precise method to manipulate surface configurations, allowing for the fine-tuning of the topological surface states in Bi2Se3, which represents a significant advancement toward nanoengineering of topological states.

Study of the microhardness ensuring the contact endurance of structural materials

The strength of the working surfaces of gears depends on the mechanical properties of the material and the quality of parts. We present the results of studying the strength of materials and working surfaces of a gear mechanism due to structural changes attributed to chemical and thermal treatment. The surface strength of the gears of gas turbine engines was studied. Nitrocementation and ion nitriding were used for chemical and thermal treatment of the contacting surfaces of steel samples under study (20Kh3MVF-Sh, 16Kh3NVFMB-Sh, 18Kh2H4MA, and 12Kh2H4A). Changes in the microhardness of the component layers (diffusion, transition and basic) of the toothed crown were analyzed. Metallographic analysis of the structure of materials was carried out to describe the factors determining the surface strength of working surfaces. Systematized data on the change in the microhardness of materials obtained experimentally in conditions of mass production are presented. Presented experimental results on changes in the mechanical properties of materials are based on data on the microhardness and structural state of the surface layers of the working profiles of gears. A comparative assessment of the surface strength of the studied samples during contact interaction was performed. The dependence of the surface strength on the multifactorial volumetric structure and structure formation of the material in the process of operation is determined. It is shown that the method of surface saturation forms the structure of a material with different mechanical properties accompanied with the formation of a transition zone having characteristic distinctive values of the hardness. The results obtained can be used in the design of gears, taking into account changes in the mechanical properties and structure of materials to ensure the necessary operational requirements.

Research on a Method for Identification of Peanut Pests and Diseases Based on a Lightweight LSCDNet Model.

Timely and accurate identification of peanut pests and diseases, coupled with effective countermeasures, is pivotal for ensuring high-quality and efficient peanut production. Despite the prevalence of pests and diseases in peanut cultivation, challenges such as minute disease spots, the elusive nature of pests, and intricate environmental conditions often lead to diminished identification accuracy and efficiency. Moreover, continuous monitoring of peanut health in real-world agricultural settings demands solutions that are computationally efficient. Traditional deep learning models often require substantial computational resources, limiting their practical applicability. In response to these challenges, we introduce LSCDNet (Lightweight Sandglass and Coordinate Attention Network), a streamlined model derived from DenseNet. LSCDNet preserves only the transition layers to reduce feature map dimensionality, simplifying the model's complexity. The inclusion of a sandglass block bolsters features extraction capabilities, mitigating potential information loss due to dimensionality reduction. Additionally, the incorporation of coordinate attention addresses issues related to positional information loss during feature extraction. Experimental results showcase that LSCDNet achieved impressive metrics with accuracy, precision, recall, and Fl score of 96.67, 98.05, 95.56, and 96.79%, respectively, while maintaining a compact parameter count of merely 0.59 million. When compared with established models such as MobileNetV1, MobileNetV2, NASNetMobile, DenseNet-121, InceptionV3, and X-ception, LSCDNet outperformed with accuracy gains of 2.65, 4.87, 8.71, 5.04, 6.32, and 8.2%, respectively, accompanied by substantially fewer parameters. Lastly, we deployed the LSCDNet model on Raspberry Pi for practical testing and application and achieved an average recognition accuracy of 85.36%, thereby meeting real-world operational requirements.

Influence of silicon interlayers on the structural and reflective X-ray characteristics of Ni/Ti multilayer mirrors

The influence of Si interlayers on the microstructure of the films and boundaries and on the reflective characteristics of Ti/Ni multilayer mirrors has been studied using X-ray reflectometry and diffractometry. We established that these Si interlayers perform different functions at different interfaces. An Si interlayer at an Ni-on-Ti interface acts as a diffusion barrier. An Si interlayer at a Ti-on-Ni interface mainly acts as a smoothing layer with a slight diffusion barrier effect. The largest increase in the reflectance, from 62 to 65.7%, at a wavelength of 1.54 Å, is observed when Si interlayers are deposited on both boundaries. The reason for the increase in reflectivity is the decrease in the widths of the transition layers from 6.5 Å on Ni and 7.5 Å on Ti, to 6.0 Å on Ni and 5.0 Å on Ti, respectively. Here, we explain this through the `barrier' effect of Si interlayers, which results in less mixing of film materials at the interfaces. Data on the reflectance of Ni/Ti multilayer mirrors in the spectral range of the `water window' at a wavelength of 27.4 Å are presented for the first time. The maximum reflectivity for an Ni/Ti multilayer mirror at a grazing angle of 7.2° was about 56%.

Hydrophobic and positively charged magnetic nanoparticles for enhanced oil recovery from concentrated emulsion wastewaters

With the development of petroleum industry, a large amount of oil-in-water (O/W) emulsion wastewaters were produced, resulting in serious environmental pollution and resource waste. Up till now, magnetic nanoparticles (MNPs) were frequently reported in emulsion wastewater treatment and mainly focused on the water purification, but little effort was devoted to the facile recovery of oil resource. In the present work, a class of hydrophobic and positively charged MNPs, namely dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DOTAC)-coated MNPs (M−DOTAC), was carefully synthesized by regulating DOTAC anchoring density on Fe3O4@SiO2, and then employed to treat the concentrated emulsion wastewaters stabilized by anionic sodium dodecyl benzene sulfonate (SDBS) or nonionic Tween-80. M−DOTAC with relatively high DOTAC density (M−DOTAC 1.8) exhibited higher positive charge density and hydrophobicity, and hence could significantly promote the oil droplet coalescence and mergence via the electrostatic attraction and hydrophobic adsorption bridging as well as the hydrophilic-lipophilic transition of interfacial adsorption layer. Accordingly, with addition of moderate dosage of M−DOTAC 1.8, the emulsion was broken and divided into three layers: (1) a continuous oil layer was formed in the upper layer which could be directly recycled; (2) the middle layer was composed of MNPs-tagged oil droplets/flocs; (3) the bottom layer was the clearer water phase. The optimal recovery rate of oil resource reached ∼ 60 % in SDBS stabilized system, and further increased to ∼ 98 % in Tween-80 stabilized system. However, the oil recovery rate was declined at an excessive dosage of M−DOTAC 1.8 due the formation of double emulsion. Besides, M−DOTAC 1.8 exhibited good reusability. These results indicated the fabricated M−DOTAC had great application prospect in treating emulsion wastewaters containing high oil content.

Internal oxidation behavior and its effect on the surface crack formation in a Fe-Mn-Al-C high Mn steel

The correlation between internal oxidation and surface crack was investigated in high Mn steel. Time- and temperature-dependent internal oxidation behaviors are examined in the temperature ranges of 1000– 1250 °C, revealing faster and deeper oxidation along grain boundaries than in grain. Oxides at the internal oxidation layer are confirmed to be MnO and MnAl2O4. The grain boundary penetration depths of the internal oxide increase from 13 to 34 μm as the temperature increases. The tensile crack on the surface of the specimen was evaluated after 5 % straining with 10−3/s strain. Temperature-dependent crack formation probability (LAC/LT) increases also from 0.4 to 1.6 % as the temperature increases. The evolution of the internal oxidation layer during the hot compression test was investigated to clarify its role in surface crack formation. The transition of the internal oxide layer to the external oxide layer was observed. Exfoliation of the external oxidation layer was also confirmed by further compression. Driving force calculation on the internal and external oxides reveals that the abundant oxygen supply originating from the cracking of oxide and thickness reduction of the internal oxide layer transforms the internal oxide layer to scale during the compression. High-resolution analysis of the grain boundary crack reveals the cracking of grain boundary MnAl2O4. The comparison between the grain boundary oxides’ penetration depth and the crack formation behavior clarifies the grain boundary internal oxide’s crucial role in the surface crack formation in a high Mn steel. This study provides vital insights into the surface crack formation mechanism in a Fe-Mn-Al-C-based high Mn steel during hot-rolling processes, highlighting the significance of grain boundary internal oxidation in production.

Solidified characteristic and enhanced properties of Al0.5MnFeNiCu0.5/Al–Ni functionally gradient coating fabricated by laser cladding on AZ91HP

To ensure the high entropy effect of the coating, it is necessary to control the dilution of Mg during laser cladding process. Therefore, Al0.5MnFeNiCu0.5/Al–Ni functionally gradient coating was proposed in this work. More remarkable, the design of Al–Ni transition layer effectively prevented the dilution of Mg into Al0.5MnFeNiCu0.5 layer, and relieved physical and chemical differences between Al0.5MnFeNiCu0.5 layer and Mg alloy. Al0.5MnFeNiCu0.5 layer exhibited flower-like grain consisted of BCC phase. Al–Ni remelting layer crystallized as the fine snowflake-like grain. Al–Ni layer presented coarse needle-like grain morphology. Microhardness of Al0.5MnFeNiCu0.5 layer was about 8.2 times more than that of the substrate. Specifically, compared with Mg alloy and Al–Ni layer, the wear volume of Al0.5MnFeNiCu0.5 layer were decreased by 87.83% and 50.38%, respectively. The results of Polarization curve, Nyquist curve and Bode plot indicated that Al0.5MnFeNiCu0.5 layer displayed better corrosion resistance than Al–Ni layer and Mg alloy.

Influencing Factors of Spatial Ability for Architecture and Interior Design Students: A Fuzzy DEMATEL and Interpretive Structural Model

Spatial ability is not just a skill but a crucial element for architecture and interior design students, significantly impacting their proficiency in tasks involving 2D drawings, 3D components, and artistic expression. Despite extensive research in this area, a gap remains in the understanding of how to effectively cultivate spatial ability through educational interventions. This study, with its unique approach of identifying key influencing factors and their interrelationships within the fuzzy decision-making laboratory analysis method (Fuzzy-DEMATEL) and the interpretative structural model (ISM), fills this gap. The method visualizes cause-and-effect relationships within a structural model and captures the interdependencies between influencing factors. In a collaborative effort between nine universities in 2023–2024, 17 experts selected through purposeful sampling contributed to the development of a comprehensive list of potential influencing factors. After refinement through filtering, comparison with the existing literature, and expert consensus, seven influencing factors of spatial ability for architecture and interior design students from personal traits and STEAM disciplines were identified, which are sketching and hand drawing skills, mathematical skills, video game practice, descriptive geometry skills, augmented reality practice, spatial talk, and gesturing while talking. Sketching and hand drawing skills, mathematical skills, and video game practice come under cause factors of spatial ability, whereas the rest are effect factors. Proceeding with ISM analysis revealed that sketching and hand drawing skills and mathematical skills are located in the input layer and have a continuous impact on spatial ability. Descriptive geometry skills lie in the transition layer, which are considered as deep influencing factors, the rest of the factors lie in the effect layer. This study delves into the theoretical and practical implications of these findings, offering valuable insights for educational policy and practice.

Preparation and characterisation of gradient HA/TiN/Ti coatings for biomedical applications

A gradient transition HA/TiN/Ti composite coating was deposited on the surface of medical Ti6Al4V alloy using the reactive magnetron sputtering technique. The influence of deposition parameters on the microstructure, mechanical properties, corrosion resistance, and in vitro mineralisation of the coating were systematically investigated. The results demonstrated that deposition parameters such as sputtering power, bias voltage, and sputtering pressure had a significant impact on the microstructure and morphology of HA/TiN/Ti composite coatings. The gradient TiN/Ti transition layer remarkably enhanced the adhesion strength, increasing the critical load from 7.5 N (HA monolayer) to over 40 N (HA/TiN/Ti multilayer). Moreover, compared to single TiN/Ti and HA coatings, the HA/TiN/Ti composite coatings exhibited better corrosion resistance and metal ion shielding ability while also demonstrating excellent capability for inducing bone-like apatite formation, thereby greatly ensuring the exceptional stability of the surface bioactive coatings.

Effects of irradiation on interfacial strength and microstructure of double-layer mullite and alumina coating on SiC

Silicon carbide (SiC) ceramics hold great potential for use in nuclear-reactor components due to characteristics such as high-temperature strength and low activation. Despite their resistance against corrosion in harsh environments, they suffer elevated corrosion rates under particle irradiation. Thin anti-corrosion coatings, such as mullite bond layers and alumina top layers, are essential to enhance the irradiation stability of SiC. The objective of this study was to evaluate the irradiation stability of a double-layer coating developed to enhance the corrosion resistance of SiC in nuclear applications. The coating, which comprised a mullite bond layer and an alumina top layer, was applied to a SiC substrate using laser chemical vapor deposition. Irradiation experiments were conducted at 300 °C with 5.1-MeV Si ions up to 10 displacements per atom. To assess the interfacial strength, a novel testing method, called the double-notch shear compression testing method, was developed based on ASTM standards and was implemented using a nanoindenter. This approach enabled precise measurements of the mechanical integrity at the interfaces of the coating under irradiation. The results showed an increase in the interfacial strength at the SiC/mullite and alumina/mullite interfaces with irradiation. Microstructural analysis of the fracture surface through scanning electron microscopy–energy-dispersive X-ray spectroscopy revealed that cracks propagated within the mullite layer, indicating the presence of mullite on the fracture surface. Transmission electron microscopy (TEM) images indicated that a 2-µm-thick transition layer existed at the SiC/mullite interface but not at the alumina/mullite interface. The TEM–electron energy loss spectroscopy suggested that the Al-O bonding structures in the transition layer were changed from tetrahedral (AlO4) to octahedral (AlO6) through irradiation, and this structural transition may directly affect the strength.

Microstructure and mechanical properties of laminated ferrous medium-entropy alloys fabricated by direct energy deposition and post-rolling annealing treatment

Laminated ferrous medium entropy alloy (Fe-MEAs), Fe75(CoCrNi)25/Fe60(CoCrNi)40, was successfully fabricated by direct energy deposition (DED). Due to the component mixing during DED process, a transition layer with face-centered cubic (FCC) and body-centered cubic (BCC) dual-phase was obtained in the Fe60(CoCrNi)40 layer after rolling and annealing. This dual-phase exhibits higher strength compared to a single FCC phase, thereby enhancing the overall strength of the material. During the deformation process of the laminated material, interface constraint will lead to high yield strength, resulting in performance superior to that predicted by the rule of mixtures. Moreover, the transition layer plays an important role in strain transferring and shows greater strain-hardening ability than the other two layers, enhancing the overall ductility of the laminated alloy.

Research on the microstructure and mechanical properties of functional gradient materials of TC4/TC11 titanium alloys for wire arc additive manufacturing with different transitional forms

Functional gradient materials (FGMs) have garnered increasing interest for their potential in material and structural design. Additive manufacturing, as a kind of free manufacturing and near-net shaping technology with in-situ controllability of materials, is the dominant technology for fabricating FGMs. While numerous studies have been conducted on titanium alloy FGMs, there is still a lack of research on the structure and properties of the material with the number of transitional layers. This study employs double-wire arc additive manufacturing to fabricate FGMs composed of TC4 and TC11 alloys. The study examines the utilization of direct and continuous transition forms in conjunction with stress relieving and solution aging heat treatment processes. The composition, grain morphology, microstructure, and mechanical properties of FGMs are analyzed. Results indicate that in samples employing direct transition, higher heat treatment temperatures and durations lead to a more uniform composition and microstructure. Additionally, the interface morphology becomes increasingly indistinct, and transversal elongation at the interface is enhanced by the strain compensation of the two materials. In continuous transitional samples, an increase in the number of transitional layers results in a more uniform microstructure near the interface, leading to a reduction in interface morphology and an enhancement of mechanical properties. The fracture position tends to shift closer to the TC4 side, with both process forms exhibiting ductile fractures. The plasticity of the TC4 part is superior, and the ductile fracture morphology is more pronounced. This study offers a valuable experimental foundation for investigating the direct and continuous transition of titanium alloy FGMs.

Solvent-mediated oxide hydrogenation in layered cathodes.

Self-discharge and chemically induced mechanical effects degrade calendar and cycle life in intercalation-based electrochromic and electrochemical energy storage devices. In rechargeable lithium-ion batteries, self-discharge in cathodes causes voltage and capacity loss over time. The prevailing self-discharge model centers on the diffusion of lithium ions from the electrolyte into the cathode. We demonstrate an alternative pathway, where hydrogenation of layered transition metal oxide cathodes induces self-discharge through hydrogen transfer from carbonate solvents to delithiated oxides. In self-discharged cathodes, we further observe opposing proton and lithium ion concentration gradients, which contribute to chemical and structural heterogeneities within delithiated cathodes, accelerating degradation. Hydrogenation occurring in delithiated cathodes may affect the chemo-mechanical coupling of layered cathodes as well as the calendar life of lithium-ion batteries.