Solid-phase Diffusion Research Articles

Analysis of pore formation and carburizing mechanism of magnetite reduction by CO

To investigate the porosity and expansion mechanism of CO-reduced magnetite, the reduced microstructures of magnetite under conventional heating and microwave heating were compared. The microstructure characteristics of magnetite with various reduction degrees were examined in a 60%CO-Ar reduction atmosphere, and the formation and evolution mechanism of the structure were analyzed in conjunction with the reduction effect. The results indicate that the reduction product of CO reduced magnetite possesses a porous structure. Nevertheless, when the gas diffusion is restricted, the reduction process is sluggish and the porous structure is not readily formed. Microwave heating enhances the gas-phase diffusion capacity, thermodynamic carburizing capacity, and solid-phase carbon-oxygen diffusion capacity, resulting in a higher oxygen loss rate than that of conventional heating. Under the experimental conditions, the lattice shrinkage during the Fe3O4 → Fe0.88O transformation and the rapid expansion of Fe0.88O → Fe0.94O are the causes of the crack. Microwaves facilitate the formation of pores and cracks in the product. This study offers a novel concept for the development of foam steel.

Evolution of microstructure and mechanical properties in TiBw/Ti65 composites during vacuum solid-phase diffusion bonding

This paper examines the solid-phase diffusion bonding (DB) of TiBw/Ti65 composites, focusing on the effects of processing parameters such as temperature, time, pressure, and interlayer thickness. The findings show that lower processing conditions resulted in slower atomic diffusion and more defects, whereas higher conditions reduced pores but led to grain growth. Optimal bonding was achieved at 950°C, 10MPa, and 60minutes, yielding a shear strength of 686MPa, which is 81.86% of the base material's strength. The introduction of pure titanium interlayer results in a concentration gradient, which serves as an additional driving force for atomic diffusion, thereby enhancing the quality of diffusion bonding. Shear strength varied with interlayer thickness, peaking at 668MPa for a 5 μm interlayer. Microplastic deformation, dynamic recrystallization (DRX), and grain boundary (GB) migration affected the microstructure and mechanical properties of the bonding interface. TiB whiskers (TiBw) near the bonding interface significantly influenced DRX and GB migration during the DB process.

Oxygen-containing groups assist in enhancing Li+/K+ storage: Balancing adsorption and intercalation mechanisms

Porous carbon nanosheets were prepared using a high-temperature solid-phase method and subsequently modified through oxidative acid treatment to introduce oxygen-containing groups. The application and performance of these nanosheets as anodes in lithium-ion and potassium-ion batteries were investigated. The results indicated that the oxidative acid treatment successfully enhanced the porous carbon nanosheets' capacity for storing Li+/K+. Electrochemical analysis revealed that the oxygen-containing groups balanced intercalation and surface storage behaviors, optimizing the nanosheets' storage performance. These modified porous carbon nanosheets (termed SN@PCNs) demonstrated significantly boosted reversible Li+ and K+ storage capacities, achieving 1038.1 mAh⋅g−1 and 371.7 mAh⋅g−1 at 0.1 A g−1, respectively, while maintaining capacities of 443.3 mAh⋅g−1 for Li+ and 153.9 mAh⋅g−1 for K+ at 5.0 A g−1. Furthermore, the study emphasized the significance of a balanced surface capacitance and solid-phase diffusion storage mechanism in attaining high storage capacity and cycle stability. Moderate oxidation and the introduction of oxygen-containing groups were identified as crucial factors in optimizing performance. Additionally, potassium adsorption storage exhibited an advantage over lithium adsorption storage, and the impact of oxygen-containing groups on potassium storage performance was even more pronounced.

Simplified Physics-Based Battery Model for Stationary Energy-Storage Applications

To perform safe battery operation and avoid unnecessary degradation, battery models are needed. How complex, or close to reality the model should be, depends on the purpose of the model and the computational power available. The possibility for accurate parameterization before model implementation is another crucial aspect for the validity. Physics-based models have the advantage to solve for internal battery states, which includes important information to avoid accelerated degradation and to evaluate state of health. But the parameterization effort can be extensive and the computational cost too high to solve for in real time. Identifying the most essential processes and if possible, simplify the model is therefore motivated.Parameter sensitivity is a powerful tool to investigate how much certain parameters and the related processes effect the output signal, i.e. battery voltage. Under normal operating conditions the cells are rarely completely discharged, and as a result the diffusion processes show low sensitivity during operation [1]. In this work we therefore explore the utilization of a physics-based model solving for the electrolyte dynamics, rather than the solid phase diffusion commonly applied in the so-called single particle model. By neglecting the diffusion processes, the second dimension in the pseudo-two-dimensional (P2D) model can be ignored and the computational complexity simplified. The parameterization strategy and validation of the model is further discussed.We evaluate our model by comparing simulations with experimental data from batteries subjected to stationary energy storage applications. The cells are commercial 18650-type NMC/Graphite cells with 2.6 Ah capacity. Different service cycles have different needs in terms of current and voltage, see examples in Figure 1. Capturing these behaviours with a physics-based model might pose different challenges and will further affect the degradation of the cells [2]. A wide range of models exist in literature to capture degradation mechanisms during battery operation [3]. To keep the computational and parameterization effort as low as possible, our methodology is not to include more physics, but instead update the parameters to the processes already included in the model [4]. We explore this strategy comparing the behaviour from different types of services, as well as batteries where the application changes, to see the model response and analyse the battery state of health, see Figure 2. Electrochemical techniques such as differential voltage analysis and electrochemical impedance spectroscopy is included to support our conclusions.Our results highlight the value of application considerations when designing battery models, rather than only focusing on physical extreme points. We present an alternative physics-based model with the ability to capture crucial degradation phenomena and validate it against operational data. We believe our findings can be of value for smarter battery operating strategies and a greater understanding of application dependant lithium-ion battery degradation.Figure 1. Some of the application duty cycles part of the experimental study. a) Current profile peak shaving b) Current profile frequency regulation c) Voltage response peak shaving d) Voltage response frequency regulation.Figure 2. Degradation trends from the experimental study. Purple cell initially performing PS following application change to FR_high cycling a) Capacity evolution of the cycled cells b) tortuosity parameter evolution obtained from model parameter fitting c) Measured impedance response during cell reference performance tests d) Calculated charge transfer resistance from measured impedance data.

Reconstructing the Pseudo-2-Dimensional (p2D) Model in Comsol Multiphysics Using Mathematical Interfaces

The classic ‘pseudo-2-dimensional’ (p2D) model of Newman and co-workers (also known as the DFN model), with its different efficient implementations, is the state-of-the-art physics-based electrochemical model for lithium-ion batteries. COMSOL Multiphysics (COMSOL) is a popular modeling software for multiphysics simulations, and its Battery Design Module for Li-ion batteries is widely used in the battery modeling community. This work presents a step-wise model development for reconstructing the detailed p2D model equations. This includes variable model parameters and weak-form implementation for the solid-phase diffusion, eliminating the need for non-local couplings and approximations for modeling the pseudo radial-dimension in the solid-phase.To model and understand the effect of capacity degradation on lithium-ion cells, the battery models in COMSOL need to incorporate additional degradation mechanisms. In this work, we have followed the approach of equation-based modeling in COMSOL, which enables us to formulate the p2D model using the mathematical PDE interfaces. This approach provides us with a lot of flexibility in terms of battery degradation model formulation and helps develop a clearer understanding of the p2D model equation in light of the assumptions involved.The steps in the model development involved writing the conservation equations in the generic mathematics interfaces coupled with the additional equations for the degradation mechanisms. The efforts were centered on developing cycling simulations based on Events for practically relevant operating conditions. This custom model was validated against the results from COMSOL’s Battery Interface, in-house codes, and baseline cycle data from the experiments and further developed as a physicochemical degradation model for automotive, large-format Lithium-ion batteries.This equation-based COMSOL model with cycling works without the requirement for Battery Design Module, LiveLink and Application Builder and can be adopted for a variety of electrochemical modeling applications by the electrochemical modeling community.

High-purity La3-xTe4 Material with Superior Thermoelectric Performance Synthesized via Te-vapor Transport and Solid-State Diffusion.

La3-xTe4 is a very promising high-temperature candidate applied in next-generation Radioisotope Thermoelectric Generators (RTGs). Conventional synthesis of such materials is based on the mechanochemical method, which makes the sample difficult to purify due to the high-energy ball milling. In this report, a novel synthetic method is developed, which utilizes Te-vapor transport and solid-phase diffusion to efficiently produce the RE3-xTe4 phases (RE = La, Ce, Pr, Nd). Notably, this method obviates the requirement for high-energy ball-milling instruments, conventionally indispensable in the mechanochemical syntheses. For as-synthesized La2.74Te4 material, a high figure of merit of 1.5 is achieved at 1073K, owning to the reduced electronic thermal conductivity with metal impurities well eliminated.

Diffusion-Equation-Based Electrical Modeling for High-Power Lithium Titanium Oxide Batteries

Lithium titanium oxide (LTO) batteries offer superior performance compared to graphite-based anodes in terms of rapid charge/discharge capability and chemical stability, making them promising candidates for fast-charging and power-assist vehicle applications. However, commonly used battery models often struggle to accurately describe the current–voltage characteristics of LTO batteries, particularly before the charge/discharge cutoff conditions. In this work, a novel electrical model based on the solid-phase diffusion equation is proposed to capture the unique electrochemical phenomena arising from the diffusion mismatch between the positive and negative electrodes in high-power LTO batteries. The robustness of the proposed model is evaluated under various loading conditions, including constant current and dynamic current tests, and the results are compared against experimental data. The experimental results for LTO batteries exhibit remarkable alignment with the model estimation, demonstrating a maximum voltage error below 3%.

The sensitive detection of the early-stage internal short circuit triggered by lithium plating through the simplified electrochemical model at various working conditions

The internal short circuit (ISC) is one of the main causes of thermal runaway in batteries. Facing the current fast charging scenario of batteries, this paper aims to explore the sensitivity of solid-phase diffusion coefficient to ISC during high current charging. The voltage and current data of the real ISC is input into the simplified pseudo-two-dimensions model to identify the intrinsic parameters. The results indicate that the positive solid-phase diffusion coefficient (Ds,p) has higher sensitivity and stability than the negative solid-phase diffusion coefficient (Ds,n). For real ISC, the sensitivity of the solid-state diffusion coefficient increases as the charging current increases. This is consistent with the trends in ISC that we have derived from our low-temperature ISC extension experiment. For #1 ISC battery at 25 °C (SOC = 0.3–0.85), Ds,p changes by 56 % (3C) and 96 % (5C), and Ds,n changes by 6.87 × 10−14m2/s (166 %) (3C), 8.38 × 10−14m2/s (670 %) (5C). Moreover, the sensitivity of the solid-state diffusion coefficient to ISC decreases after battery aging, but it still has sufficient ability to diagnose ISC. High temperature will reduce the sensitivity of the solid phase diffusion coefficient.

Growth behavior of cristobalite SiO2 coating on 4H–SiC surface via high-temperature oxidation

When SiO2 films undergo oxidation on 4H–SiC, a distinctive crystalline phase, cristobalite, emerges at elevated temperatures. We deeply explored the growth mechanism of the crystallite, focusing on its dependence on the silicon sublimation process (SSO). Activation energy calculations confirmed that the oxidation after SSO above 1350 °C exhibits a lower activation energy. The reduced activation energy suggests the elimination of the solid-phase diffusion process during oxidation. We devised a controllable growth process for the quartz phase to achieve a seamless transition from 0 to 100 % in the area proportion of cristobalite in SiO2. This strategic approach facilitates the precise preparation of oxide layers and holds potential applications in semiconductor device manufacturing.

Extending a Multiphysics Li-Ion Battery Model from Normal Operation to Short Circuit and Venting

Mitigation of Li-ion battery system fires consists of reliable fault detection and proactive, fast discharge control. Both require modeling of failure modes due to high temperatures and currents between normal operation and thermal runaway. In this work, we present a control-oriented, reduced-order, multiphysics model that captures the electrochemical, thermal, gas generation, mechanical expansion, and venting behavior of NMC pouch cells undergoing an external short circuit (ESC) from different initial state-of-charge (SOC). The model is parameterized through experiments by fitting the solid-electrolyte interphase (SEI) decomposition rate, the cell’s thermal parameters, and the particle solid-phase diffusion parameters to capture the first venting timing, peak temperature, and diffusion-limited electrical behavior at high currents. Using a single parameter set, the multiphysics model can capture behavior during an ESC to predict whether a cell will generate gas and vent, predict the vent timing within 10 seconds of it occurring in the experiment, and maximum cell expansion pressure within 10 kPa for cells that did not vent. The model can also predict the SOC trajectory for cells with a high initial SOC within 6% SOC for the 15-minute discharge or until the cell vents.

Synthesis of equiaxed Si3N4 from Si(NH)2 by adding seeds formed by in situ nitridation of silicon

High-quality Si3N4 powder is a prerequisite for the preparation of high-performance Si3N4 ceramics. In this paper, Si3N4 powders with regular morphology were successfully prepared by pyrolysis of Si(NH)2 using silicon as a nucleation inducing agent. The mechanism of the silicon in regulating the morphology and particle size of Si3N4 powders was investigated. The results show that when Si(NH)2 is pyrolyzed directly at 1500 °C under N2 atmosphere, the products are mainly whiskers accompanied by some particles with irregular shape. In the presence of silicon, the powder particles exhibit a regular hexagonal prismatic morphology. With the increase of silicon content, the whisker content decreases obviously, and the whisker disappears completely when the silicon content exceeds 10 %. Furthermore, the particle size of Si3N4 powder decreases with the increase of silicon content, and the particle size is the smallest when the silicon content is 15 wt%, which is about 802 nm. The nucleation and growth process of Si3N4 powder particles can be divided into three stages. Firstly, silicon reacts with N2 to form Si3N4 nuclei. Then, amorphous Si3N4 partially decomposes to form Si(g) and SiO(g) and grows on the formed Si3N4 nuclei as the temperature increased. Finally, undecomposed amorphous Si3N4 spontaneously nucleates and grows of the solid-phase diffusion mechanism. Ultimately, all the powders show equiaxial regular morphology. Preferential nitridation of silicon to form Si3N4 nuclei provides nucleation sites for vapor-phase products, which is the key to inhibiting whisker formation and regulating the particle size of Si3N4 powders.

Manufacturing high-strength and corrosion-resistant 6063Al joints by an ultrasonic-assisted liquid and solid phase diffusion technology

High corrosion-resistance aluminum alloy joint obtained by filler metal containing Sn at relatively low temperatures is a longstanding goal for electronic products. In this research, 6063Al alloys was joined by a novel ultrasonic-assisted diffusion bonding via liquid phase and solid phase synergistic diffusion. It was performed via a hypereutectic interlayer of Zn-30Sn at 360 ℃ to joining 6063Al, obtaining a Zn-Al eutectoid structures joint. By the ultrasonic vibrating, the breaking of oxide film, the diffusing of liquid and solid state had been occurring in sequence during the joining process. It resulted in a series of diffusing phase transitions from “η-Zn phases + Sn-Zn eutectic structures” to “Zn-Al eutectoid structures + η-Zn phases”, and finally to “full Zn-Al eutectoid structures”, which were driven by the grain boundary penetration and chemical potential, respectively. The joints possessed a higher strength than the base metal. The joints with Zn-Al eutectoids have a better corrosion resistance that the tensile strength reduced 37.3% after a corroding of 72 h in 3.5 wt% NaCl solution in comparison with the soldered joints. Finally, the mechanism of ultrasonic accelerated diffusion, joint formation process and mechanism of improving corrosion resistance were discussed in detail.

Absorption of volatile organic compounds (VOCs) by polymer tubing: implications for indoor air and use as a simple gas-phase volatility separation technique

Abstract. Previous studies have demonstrated volatility-dependent absorption of gas-phase volatile organic compounds (VOCs) to Teflon and other polymers. Polymer–VOC interactions are relevant for atmospheric chemistry sampling, as gas–wall partitioning in polymer tubing can cause delays and biases during measurements. They are also relevant to the study of indoor chemistry, where polymer-based materials are abundant (e.g., carpets and paints). In this work, we quantify the absorptive capacities of multiple tubing materials, including four nonconductive polymers (important for gas sampling and indoor air quality), four electrically conductive polymers and two commercial steel coatings (for gas and particle sampling). We compare their performance to previously characterized materials. To quantify the absorptive capacities, we expose the tubing to a series of ketones in the volatility range 104–109 µg m−3 and monitor transmission. For slow-diffusion polymers (e.g., perfluoroalkoxy alkane (PFA) Teflon and nylon), absorption is limited to a thin surface layer, and a single-layer absorption model can fit the data well. For fast-diffusion polymers (e.g., polyethylene and conductive silicone), a larger depth of the polymer is available for diffusion, and a multilayer absorption model is needed. The multilayer model allows fitting solid-phase diffusion coefficients for different materials, which range from 4×10-9 to 4×10-7 cm2 s−1. These diffusion coefficients are ∼ 8 orders of magnitude larger than literature values for fluorinated ethylene propylene (FEP) Teflon film. This enormous difference explains the differences in VOC absorption measured here. We fit an equivalent absorptive mass (CW, µg m−3) for each absorptive material. We found PFA to be the least absorptive, with CW ∼ 105 µg m−3, and conductive silicone to be the most absorptive, with CW ∼ 1013 µg m−3. PFA transmits VOCs easily and intermediate-volatility species (IVOCs) with quantifiable delays. In contrast, conductive silicone tubing transmits only the most volatile VOCs, denuding all lower-volatility species. Semi-volatile species (SVOCs) are very difficult to sample quantitatively through any tubing material. We demonstrate a system combining several slow- and fast-diffusion tubing materials that can be used to separate a mixture of VOCs into volatility classes. New conductive silicone tubing contaminated the gas stream with siloxanes, but this effect was reduced 10 000-fold for aged tubing, while maintaining the same absorptive properties. SilcoNert (tested in this work) and Silonite (tested in previous work) steel coatings showed gas transmission that was almost as good as PFA, but since they undergo adsorption, their delay times may be humidity- and concentration-dependent.

KINETICS OF CATHODIC HYDROGEN EVOLUTION ON MOLYBDENUM DISILICIDE IN ACID SULPHATE MEDIA

The kinetics and mechanism of hydrogen evolution on the MoSi2 electrode in x M H2SO4 + (0.5 - x) M Na2SO4 (x = 0.50; 0.35; 0.20) solutions have been studied. The cathodic polarization curves of MoSi2 in the studied solutions are characterized by Tafel region with a slope of (-0.070)±0.002 V. The reaction order of the cathodic process with respect to hydrogen ions at the potentials of Tafel region is ~1.0; the derivative of the electrode potential with a change in electrolyte acidity is ~0.072 V. The impedance spectra of the MoSi2 electrode in the studied potential range have the shape of a semicircle located in the capacitive half-plane, with the centre in the region of positive values of the imaginary impedance component; in the region of the highest frequencies, a short straight section is recorded on the impedance plots, indicating the presence of pores in the surface layer of the electrode. To describe the hydrogen evolution reaction on MoSi2, we used an equivalent electrical circuit, the Faraday impedance of which consists of series-connected charge transfer resistance (R1) and a parallel R2C2Zd-chain responsible for the adsorption of atomic hydrogen on the surface and its diffusion into the depth of the electrode material. The equivalent circuit also includes the solution resistance (Rs) and the double layer capacitance impedance, which is modeled by the constant phase element CPE1. It is shown that the hydrogen evolution reaction on molybdenum disilicide in a sulphuric acid electrolyte proceeds along the discharge - recombination route with a quasi-equilibrium discharge stage when the Temkin logarithmic isotherm for adsorbed atomic hydrogen is fulfilled. The hydrogen evolution reaction is complicated by hydrogen absorption proceeding in the mode of solid-phase diffusion kinetics.

Robust state-of-charge estimation for LiFePO4 batteries under wide varying temperature environments

During the driving process of electric vehicles, the ambient temperature exhibits diverse variations with regional characteristics. To achieve robust state of charge (SOC) estimation for lithium-ion batteries under various varying temperature environments, this paper proposes an enhanced model-based closed-loop SOC estimation approach. First, beginning with a mechanistic analysis of batteries, the traditional second-order equivalent circuit model is enhanced by incorporating critical solid-phase diffusion effects during battery operation. Furthermore, utilizing data collected from multiple constant temperature environments, the complete enhanced battery model that accounts for the influence of current rates across a wide temperature range is constructed. Subsequently, under environments of different varying temperature settings, we design a series of complex operation experiments to verify the accuracy and generalizability of the established battery model. Meanwhile, a high-performance adaptive diagonalization of matrix cubature Kalman filter is introduced to address the challenge of fluctuating sampling noises in battery operation. Finally, the robustness and generalization of the proposed SOC estimation method are verified in multiple complex operating experiments under varying temperatures with non-Gaussian noise interferences and with non-full charging schemes. Remarkably, the proposed approach consistently delivers high-precision SOC estimation results across all scenarios, maintaining root mean square error and mean absolute error below 1.5%.

Low-Temperature and High-Performance Vanadium-Based Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries have attracted attention due to their low cost and high safety. Unfortunately, dendrite growth, hydrogen evolution reactions, cathodic dissolution, and other problems are more serious; not only that, but also the cathodic and anodic materials' lattices contract when the temperature drops, and charge transfer and solid phase diffusion become slow, seriously aggravating dendrite growth. At present, there are few studies on the low-temperature system, and studies on retaining high specific capacity are even more rare. Herein, ethylene glycol (EG) and manganese sulfate (MSO) are selected as additives, and the manganese vanadate (MVO) cathode is used to find a high-performance solution at low temperature. MVO can provide higher specific capacity and better structural stability than MnO2 to adapt to a low-temperature environment. At the same time, Mn2+ in MSO can produce a cationic shield covering the initial zinc tip at an appropriate concentration to avoid the tip effect and inhibit the dissolution of MVO. EG can not only reduce the freezing point of the electrolyte but also promote the desolvation of [Zn(H2O)6]2+. The synergistic effect of the three elements prevents the dissolution equilibrium of Mn2+ in MVO from fluctuating greatly due to the change of temperature. Therefore, when we use EG@0.2 M MnSO4 + 2 M ZnSO4 (EG + 0.2Mn/2ZSO) electrolyte at -30 °C, the Zn||Zn batteries which used this type of electrolyte can remain 350 h at 1 mA cm-2 without failure. The Zn||Cu batteries can retain 100% Coulombic efficiency after more than 2000 cycles at 0.2 mA cm-2. The Zn||MVO battery can reach 231.13 mA h g-1 at its first cycle, and the capacity retention rate is still above 85% after 1000 cycles, which is higher than that of the existing low-temperature research system.

Stable and accurate representation of species diffusion in multilayer composite electrodes using physics-informed neural networks

Stable and accurate reconstruction of species diffusion in Li-ion cell electrodes is a crucial problem, especially in modeling emerging composite electrode materials. Lithium-ion batteries are typically modeled using electrode theory coupled with various transport mechanisms that the solid-phase diffusion equation represents the main computational burden. In this paper, a computationally efficient representation for species transport in multilayer electrode is proposed based on the physics-informed neural networks (PINNs). A multi-objective loss function is constructed to obtain an accurate representation of field variables. It consists of the residual of solid-phase diffusion equation, associated initial/boundary conditions together with interface conditions. To deal with the problem of distinct material properties, the whole computational domain is divided into several subdomains where different neural networks for PINN are adopted. By using continuity conditions at interfaces, a whole network is established by combining subnetworks. By this way, the field variables can be obtained accurately by training and learning the neural networks. Li-ion concentrations in electrodes with single-layer and multilayer plate under the galvanostatic, potentiostatic, time-dependent flux, as well as time-dependent concentration charging are analyzed, and the results are validated against solutions obtained from finite element and analytical analysis. In terms of practical application, the galvanostatic voltage profiles of bi-layer (graphite-Si/SiOx) and tri-layer (graphite-Si/SiOx-graphite) electrodes are obtained using the Butler–Volmer kinetic equation and the performance is validated through good agreement with past experimental data. This study demonstrates for the first time the usefulness of the PINN to an electrochemical energy problem for designing multilayer electrode materials.

Inhibition effect of covalent carbon nanosheets on mechanochemical wear of diamond

Diamond tools experience severe chemical wear when machining ferrous metals, which hinders their practical applications. In order to improve the wear resistance of diamond cutting tools, in the diamond-graphite strong covalent structure prepared by laser induced solid-phase diffusion, carbon nanosheets (CNS) can be obtained by electrochemical stripping of the graphite layer onto the diamond matrix, which provides a new way to improve the limitations of diamond tools in application. After 14,400 cycles of reciprocating sliding against the GCr15 ball at a normal load of 2–8 N, friction was reduced by 45.9 %–65.6 % with high durability. The oxygen content is reduced by an order of magnitude during this process, suggesting that the CNS can prevent oxidation behavior at the sliding interface. The bare diamond had a relative wear rate of 4.1–15.4 times that of the CNS. It showed competitive inhibition of mechanochemical wear. Our work provides a convenient and green method of preparing in-situ CNS covalently bonded on a diamond surface, extending the way for the prospect of carbon materials.

Oxidation behaviors of electrodeposited MoSi2 coating in a wide temperature range from 773 K to 1673 K

In this study, a MoSi2 coating was prepared on the surface of a molybdenum (Mo) substrate using the molten salt electrodeposition method, and the oxidation behavior of the coating over a wide temperature range from 773 K to 1673 K was studied in detail. The phase composition, surface and cross-sectional morphologies of the MoSi2 coatings after oxidation at various temperatures were characterized, and the evolution of the phase and microstructure were analyzed to elucidate the oxidation mechanism. The experimental results showed that the MoSi2 coating exhibited excellent oxidation resistance at lower temperatures (773 K) and did not experience the pesting phenomenon. When exposed to medium and high temperatures, a continuous and dense SiO2 layer was formed on the surface of the MoSi2 coating, which effectively prevented further oxidation inside the coating, thereby protecting the Mo substrate. Meanwhile, at higher temperatures, especially at 1473 K and 1673 K, the solid-phase diffusion of Si towards the substrate gradually transformed the MoSi2 into Mo5Si3 with a lower Si content. Notably, the thickness of the Mo5Si3 layer that was distributed between the original MoSi2 coating and the Mo substrate increased with the oxidation time and temperature. At 1673 K, a Mo3Si layer with a low Si content was formed beneath the Mo5Si3 layer. Thus, the diffusion of Si was an important factor restricting the service life of MoSi2 coating.

Sustainable recovery of LiCoO2 from spent lithium-ion batteries: Simplicity, scalability, and superior electrochemical performance

In light of the ecological ramifications and material consumption stemming from exhausted lithium-ion batteries, an exigent requirement persists for efficient and expansible recycling techniques. Herein, we investigate an innovative expedited method to directly regenerate and enhance spent LiCoO2 (SLCO). The profoundly discharged SLCO powders, featuring an unimpaired crystal lattice, are isolated. These powders are then amalgamated with Li, Ni, and Mn precursors. Subsequent heating at elevated temperatures yields LNMO-SLCO, effecting the direct regeneration of LCO, accompanied by a synergistic re-lithiation process and the application of a LiNi0.5Mn1.5O4 (LNMO) coating, all achieved in a single step. The homogeneously thin spinel LNMO coating layer (10–15 nm) bestows upon LNMO-SLCO an enhanced cycling performance and charge–discharge rate capacity when benchmarked against SLCO and commercial LiCoO2 (CLCO). Evidently, at 0.1C, 0.5C, and 2C rates, LNMO-SLCO delivers discharge capacities of 214.4 mAh g−1, 187.4 mAh g−1, and 144.1 mAh g−1, respectively. Notably, it sustains 77.68 % of its original capacity following 100 cycles at 0.5 C. The merits of LNMO-SLCO are corroborated through cyclic voltammetry and electrochemical impedance spectroscopy, affirming its reduced charge transfer resistance and augmented lithium-ion solid phase diffusion coefficient. This endeavor stands as the foremost documented instance of a direct approach to SLCO reconstruction involving LNMO coating, culminating in the formation of LNMO-SLCO, characterized by sustained high-voltage cycling performance. The outlined re-lithiation and LNMO coating stratagem proffer valuable insights for the scalable, high-value recycling of SLCO, while remaining transposable to other spent cathode materials.