Graphite Materials Research Articles

Relationship between particle shape and fast-charging capability of a dry-processed graphite electrode in lithium-ion batteries

Improving lithium-ion transport in electrodes by controlling electrode microstructure is a promising option for enhancing the fast-charging capability of graphite anodes in lithium-ion batteries. Dry processing of electrodes based on a polytetrafluoroethylene binder has attracted considerable attention as an alternative to solvent-based wet processing. The morphology of graphite particles has a significant impact on electrode microstructure, but few reports have been published on dry-processed graphite anodes. In this work, we found that the morphology of graphite particles is a key factor to determine the fast-charging capability of the dry-processed graphite electrode as well as the microstructure of the dry-processed graphite electrode. X-ray microscopy combined with mercury porosimetry and symmetrical cell electrochemical impedance spectroscopy reveal that the difference in porosity between the top and bottom layers of a dry electrode with spherical graphite particles is greater than that of flake-shaped graphite particles, resulting in enhanced lithium-ion transport in the electrode and improved fast-charging capability at a high charging rate of 5C (17.5 mA cm−2). These findings supply insights into the effective design of dry-processed graphite anodes with an emphasis on fast-charging capability as well as the development of graphite anode materials for dry-processing based lithium-ion batteries.

Adsorption of antiretroviral drugs, abacavir, nevirapine, and efavirenz from river water and wastewater using exfoliated graphite: Isotherm and kinetic studies

In this work, exfoliated graphite was used to adsorb antiretroviral drugs from river water and wastewater. The exfoliated graphite was prepared from natural graphite by intercalating it with the acids and exfoliating it at 800 °C. It was characterized using Fourier Transform Infrared Spectroscopy which showed phenolic, alcoholic, and carboxylic functional groups between 1000 cm-1 and 1700 cm-1. Energy-dispersive X-ray spectroscopy results showed carbon as the main element with splashes of oxygen. The Scanning Electron Microscopy images showed increased c-axis distance between graphene layers after intercalation, which further increased after the exfoliation. The exfoliation resulted in elongated distorted cylinders, which were confirmed by the lower density (0.0068 g/mL) of exfoliated graphite material compared to the natural graphite (0.54 g/mL). The X-ray diffraction pattern showed the characteristics of hexagonal phase graphitic structure by the diffraction plane (002) at 26.74°. Raman spectroscopy results showed the natural graphite, graphite intercalated, and exfoliated graphite contained the D, G, D′, and G′ peaks at about 1350 cm-1, 1570 cm-1, 2440 cm-1, and 2720 cm-1, respectively indicating that the material's crystallinity was not affected by the modification. The highest antiretroviral drugs removal (95–99%), from the water was achieved with a solution pH of 7, an adsorbent mass of 30 mg, and an adsorption time of 30 min. The kinetic model and adsorption isotherm studies showed that the experimental data fit well in pseudo-second-order kinetics and is well explained by Freundlich's adsorption isotherm. The maximum adsorption capacity of the exfoliated graphite for antiretroviral drugs ranges between 1.660 and 197.0, 1.660–232.5, and 1.650–237.7 mg/g for abacavir, nevirapine, and efavirenz, respectively. The obtained removal percentages were 100% in river water, 63–100% in influent and 70–100% in effluent wastewater unspiked samples.

Experimental Investigation on the Impact of Graphite Electrodes Grain Size on Technological Parameters and Surface Texture of Hastelloy C-22 after Electrical Discharge Machining with Negative Polarity.

Electrical discharge machining (EDM) is a rapidly evolving method in modern industry that manufactures highly complex components. The physical properties of a tool electrode material are significant factors in determining the effectiveness of the process, as well as the characteristics of the machined surfaces. The current trend of implementing graphite tool electrodes in manufacturing processes is observed. Innovative material engineering solutions enable graphite production with miniaturized grain size. However, the correlation between the graphite electrode grain size and the mechanism of the process removal in the EDM is a challenge for its widespread implementation in the industry. This research introduces a new method to evaluate the impact of the graphite electrode grain size and machining parameters on the material removal effectiveness, relative tool wear rate, and surface roughness (Ra) of Hastelloy C-22 following EDM with negative polarity. The study utilized new graphite materials with a grain size of 1 µm (POCO AF-5) and 10 µm (POCO EDM-180). An assessment of the impact of the EDM process parameters on the technological parameters and the development of the surface roughness was carried out. Electrical discharge machining with fine-grained graphite electrodes increases process efficiency and reduces tool wear. Graphite grains detached from the tool electrode affect the stability of electrical discharges and the efficiency of the process. Based on the experimental results, mathematical models were developed, enabling the prediction of machining effects to advance state-of-the-art manufacturing processes. The obtained mathematical models can be implemented in modern industrial EDM machines as guidelines for selecting adequate machining parameters depending on the desired process efficiency, tool wear rate, and surface roughness for advanced materials.

Factors affecting the energy harvesting efficiency of graphite thermoelectric materials

Thermoelectric materials have attracted significant attention for their ability to utilize waste heat for power generation whereas natural flake graphite holds great potential as a thermoelectric material. In this work, a pressure-assisted molding process was employed to fabricate graphite bulks using natural flake graphite with different purities and particle sizes. The effect of structure on the properties of the samples was analyzed. It was found that increasing the purity of graphite is beneficial for its electrical and thermal conductivity. Notably, the thermoelectric performance of graphite initially improves and then decreases with increasing purity. The decrease of flake graphite particle size is advantageous for enhancing the Seebeck coefficient of the samples but detrimental to their electrical and thermal conductivity. It is verified that changing the forming pressure can alter the arrangement orientation of flake graphite in the sample. However, the ordered arrangement of flake graphite is not conducive to the thermoelectric properties of the sample. Ultimately, an optimized process for preparing thermoelectric materials containing graphite was obtained, namely minimizing the orientation of flake graphite in the sample, and selecting graphite with a purity of about 99 % and a particle size of nearly 50 μm.

Preparation of a graphite / SiC composite casting material and study of its performance

The inferior mechanical properties and thermal conductivity of carbon graphite materials are attributed to the presence of pores and cracks. The integration of graphite with ceramics has been proposed as a method to enhance these properties; however, graphite/ceramic composites fabricated through pressureless sintering often exhibit inadequate integration. In this paper, a diffuse-continuous network dual-reinforced graphite/silicon carbide(SiC) ceramic composite was prepared by integrating the graphite powder micro-thermal press forming technology with the fused deposition modelling(FDM) technology and combining the pressureless sintering and vacuum pressure impregnation processes. It was found that the addition of high purity silicon powder to the material formulation reacts with the resin carbon to form silicon carbide particles (SiC-p), which can play a role in diffusion enhancement. However, the addition of excessive silicon powder can have a detrimental effect, and the performance of diffusion enhanced graphite/silicon carbide composites is positively correlated with the density of billet formation, and the effect of diffusion continuous network dual enhancement is more obvious, and the performance of the composites is better compared to that of single diffusion enhancement. The compressive and flexural strengths of the graphite/SiC composites finally obtained reached 59.47 MPa and 44.25 MPa, respectively, and the thermal conductivity was 43.62 W/m·K, and the porosity and open porosity were 29.62 % and 20.48 %, respectively, which are comparable to those of manmade graphite castings, and have better gas permeability, which is expected to be applied in the casting field.

Constructing lithium-ion fast pathways via ZnO surface modification to enhance rate capability of graphite anode materials

Graphite materials have attracted widespread attention and application as anodes in lithium-ion batteries due to their abundant raw materials and environmental friendliness. However, poor rate performance is one of the most challenging issues for graphite anodes. In this work, a novel zinc oxide-graphite composite material has been fabricated, which effectively reduces the diffusion resistance of lithium ions during the charge-discharge process. Based on the analysis of the DFT calculations, the introduction of zinc oxide would be an effective way to improve the rate properties of graphite anode materials, owing to the higher lithium-ion diffusion kinetics. The concentration of zinc oxide has been optimized for the electrochemical performances of the composite electrode. Particularly, the 1%ZnO-graphite composite electrode demonstrates significant electrochemical performance with a discharge specific capacity of 337.6 mAh g−1 after 300 cycles at 1C (pure graphite is 300.6 mAh g−1) and excellent rate performance with 190 mAh g−1 at 5C (pure graphite is only 66 mAh g−1). These results pave a new direction for preparing the high rate and long cycle graphite anode materials.

Experimental study on the temperature control characteristics of graphite foam-based composite phase change materials

Thermal management systems are crucial for ensuring the reliable operation of electronic devices. Heat dissipation using phase change materials (PCMs) is an effective, lightweight method for devices experiencing transient high heat flow. Graphite foam (GF), known for its high thermal conductivity and low density, significantly increases thermal conductivity when combined with PCMs. However, research on the heat transfer characteristics of composite PCMs is limited. This study experimentally investigates the heat dissipation characteristics of a graphite foam-PCM (GF-PCM) composite cooling structure. It explores the impact of factors like the shell's tilt angle, acceleration, and the position of cavities (voids) between the PCM and the shell structure on the transient melting heat transfer of the cooling device under varying thermal source heat flux densities. Results show that using a pure paraffin phase change module, the temperature rise of the heat source increases with the tilt angle, and horizontal placement offers the best heat dissipation and temperature control. The position of the cavity influences heat dissipation; at 30W heating power, a cavity between the heat source and paraffin increases the temperature rise of the heat source by 19.2 %. Furthermore, cavity position is affected by acceleration; at 50W heating power and 3.6g acceleration, the cavity shifts from the top of the module to near the heat source side, increasing its final temperature by 3.7 °C. Acceleration also enhances liquid paraffin convection, significantly affecting paraffin's later melting stage. Adding graphite foam speeds up paraffin melting, reducing the temperature rise of the heat source by 42.8 %, 42.9 %, and 28.3 % at 30W, 40W, and 50W heating powers, respectively. This improvement mitigates the adverse effects of tilt angle, cavities, and uncertainties introduced by acceleration.

Optimizing Ultrathin 2D Transistors for Monolithic 3D Integration: A Study on Directly Grown Nanocrystalline Interconnects and Buried Contacts.

The potential of monolithic 3D integration technology is largely dependent on the enhancement of interconnect characteristics which can lead to thinner stacks, better heat dissipation, and reduced signal delays. Carbon materials such as graphene, characterized by sp2 hybridized carbons, are promising candidates for future interconnects due to their exceptional electrical, thermal conductivity and resistance to electromigration. However, a significant challenge lies in achieving low contact resistance between extremely thin semiconductor channels and graphitic materials. To address this issue, an innovative wafer-scale synthesis approach is proposed that enables low contact resistance between dry-transferred 2D semiconductors and the as-grown nanocrystalline graphitic interconnects. A hybrid graphitic interconnect with metal doping reduces the sheet resistance by 84% compared to an equivalent thickness metal film. Furthermore, the introduction of a buried graphitic contact results in a contact resistance that is 17 times lower than that of bulk metal contacts (>40nm). Transistors with this optimal structure are used to successfully demonstrate a simple logic function. The thickness of active layer is maintained within sub-7nm range, encompassing both channels and contacts. The ultrathin transistor and interconnect stack developed here, characterized by a readily etchable interlayer and low parasitic resistance, leads to heterogeneous integration of future 3D integrated circuits (ICs).

Numerical modelling and experimental validation on the discharging performance of paraffin/graphite matrix composite with various configurations of bulk density and wall temperature

Graphite material in the form of expanded has proven to be an effective material to remedy the low thermal conductivity of paraffin storage medium. The present work focuses on the solidification performance of carbon-based approach via graphite matrix composite with phase change to eliminate the bottleneck of low thermal conductivity issue of phase change materials for thermal energy storage applications beyond the current literature. Paraffin/graphite matrix composites with various bulk density values of 0 kg/m3 (Case 1), 23 kg/m3 (Case 2), 50 kg/m3 (Case 3), 100 kg/m3 (Case 4), and 143 kg/m3 (Case 5) under various operating conditions of wall temperature (Twall: 15 °C, 25 °C, 35 °C, and 45 °C), which mimic real applications' fluid temperature, are performed numerically in detail. The numerical model was validated with experimental outputs performed by the authors. Numerical results show that paraffin/graphite matrix composites have a great potential for the solidification/discharging process to recover the heat stored in the charging/melting period. Uniform and rapid solidification behaviour is achieved with the paraffin/graphite matrix composite in terms of conduction-dominated heat transfer via abundant thermal bridges compared to the pure paraffin case. Higher bulk density values and lower cold surface temperatures present superior performance in solidification rate and thermal energy recovery rate. However, the effect of the bulk density is slowed down with the beyond of certain value of bulk density (100 kg/m3). For 100 kg/m3 (Case 4) at Twall = 15 °C, the heat recovery rate is enhanced by 31.17 times and 3.84 times compared to the 0 kg/m3 and 23 kg/m3. The heat recovery rate of 100 kg/m3 is improved by 350.8 % for Twall = 15 °C in comparison with Twall = 45 °C. The total solidification rate (t = 17.5 min) increased by 90.94 % and 62.94 % for 100 kg/m3 at Twall = 35 °C compared to 0 kg/m3 and 23 kg/m3, respectively.

Growth and properties of tantalum carbide coatings on graphite by TRD technique

The tantalum carbide-coated graphite material exhibits remarkable chemical stability, corrosion resistance, and heat shock resistance, enabling it to demonstrate excellent stability during the growth of wide bandgap semiconductors. Its application significantly enhances the quality of third-generation semiconductor crystals. Nevertheless, the high cost of this material hinders its widespread utilization in the field of wide bandgap semiconductors. To address this challenge, this study employs the Thermo-reaction deposition and diffusion (TRD) technique to successfully fabricate a tantalum carbide coating on the surface of graphite. Through thermodynamic analysis, this article validate the thermodynamic feasibility of preparing tantalum carbide coatings using the TRD process. To achieve a dense and uniform TaC coating on the graphite surface, we systematically investigate the effects of reducing agent content, reaction temperature, and reaction time on the microstructure of the coating. Experimental research has found that a molar ratio of B4C to Ta2O5 of 1:0.64 optimizes the coating uniformity. Deviations from this ratio, either higher or lower, can lead to coating inhomogeneity or even failure in coating formation. Additionally, this article determine that a reaction temperature range of 1200–1400 °C, coupled with a reaction time not exceeding 6 h, represents the most suitable conditions for preparing TaC coatings on the graphite surface. Finally, to evaluate the practical performance of the coated graphite, this article simulate the corrosive environment encountered during the physical vapor transport method for growing aluminum nitride single crystals. The results demonstrate a significant improvement in the corrosion resistance of the coated graphite. This enhancement is primarily attributed to the formation of a dense TaC coating on the graphite surface, which exhibits remarkable stability at elevated temperatures.

Biomimetic construction and preparation of high-strength carbon‑carbon composites reinforced with highly disordered nanocrystalline graphite and reduced graphene oxide

With the wide application of graphite products, the low strength has become a key influencing factor hindering the application of the functionalized graphite. Taking inspiration from the phenomenon of the pericarp preventing fruit cracking in nature, we proposed a biomimetic structure based on the pomegranate, and successfully fabricated a pomegranate-like carbon‑carbon composite (PL-C/rGO-1700) at 1700 °C by spark plasma sintering (SPS), using nanodiamonds and graphene oxide (GO) as precursors, respectively. The disordered nanocrystalline graphite derived from nanodiamonds and the reduced graphene oxide (rGO) can be considered as “pomegranate seeds” and “membrane”, respectively. The addition of rGO effectively deflected the crack extension path to enhance the flexural strength of the samples. Moreover, nanodiamond-derived disordered stacked nanocrystalline graphite improved the hardness, Young's modulus, and indentation elastic recovery of graphite bulk materials. The obtained PL-C/rGO-1700 exhibited a microhardness, flexural strength, indentation elastic recovery rate, and compressive strength of 2.7 GPa, 78.1 MPa, 81.0%, and 259.0 MPa. Therefore, our work provided a simple and rapid method for the preparation of high-strength carbon‑carbon composites.

Experimental study of flake graphite large-area explosion electron emission cathode performance based on particle size discrepancy

Graphite is the most commonly used large-area cathode material in the high-power vacuum electron device for its long life and good repetitive-frequency performance, but its particle size selection scheme has not been elucidated. Therefore, in the present work, the explosive electron emission properties of flake graphite large area explosive electron emission cathodes with varied particle sizes are studied. The 320 mesh flake graphite has a current delay reduction of 0.2–0.9 ns compared to other samples at the same peak voltage. According to the Murphy–Good equation, the emission performance of each sample during the priming stage was calculated, and the threshold characteristics of 320 mesh flake graphite were significantly better than the other samples. After the space charge limited current is formed, the plasma expansion rate of all samples is 1.2±0.2cm/μs with a difference not exceeding 4% between samples. Our research provides a strong basis for the selection of raw materials for graphite based large area explosive electron emission cathodes and contributes to the development of cross-field high-power vacuum devices.

Facile Synthesis and Li-Electroactivity of Cobalt Oxide Based on Resources Recovered from Waste Lithium-Ion Batteries

In this study, cobalt oxide (Co3O4) powder was prepared by simple precipitation and heat-treatment process of cobalt sulfate that is recovered from waste lithium-ion batteries (LIBs), and the effect of heat-treatment on surface properties of as-synthesized Co(OH)2 powder was systematically investigated. With different heat-treatment conditions, a phase of Co(OH)2 is transformed into CoOOH and Co3O4. The result showed that the porous and large BET surface area (ca. 116 m2/g) of Co3O4 powder was prepared at 200°C for 12 h. In addition, the lithium electroactivity of Co3O4 powder was investigated. When evaluated as an anode material for LIB, it exhibited good electrochemical performance with a specific capacity of about 500 mAh g–1 at a current density of C/5 after 50 cycles, which indicates better than those of commercial graphite anode material.

A graded structure of silicon/carbon composite powder for highly stable lithium ion battery anode

Silicon has much higher theoretical specific capacity than traditional graphite materials (3579 mAh g−1vs. Graphite: 372mAh g−1). However huge volumetric expansion (∼300%) of silicon seriously reduces its cyclic stability as anode in lithium-ion batteries. Though reduce the size of silicon based composites to nanoscale and tuning their porosity have been extensively studied, above strategies reduce the vibration density of the anode material unsurprisingly, which is not conducive to the advantage of high volumetric capacity anode. In this work, we design a unique graded silicon/carbon powder to maintain excellent energy storage performance at high vibration density. The composite of graded structure is constructed by first particles and second particles. The construction strategy is proved to be adoptable to achieve cost effective production of high performance silicon/carbon composite anode for development of advanced lithium-ion battery. Under the premise of industrial powder materials’ production technologies, a graded structure silicon/carbon composite with optimized synthetic condition shows high-reversible capacity of 827.4 mAh g−1 at 200 mAh g−1 (equal to 1464.5 Ah L−1) and it capacity remains at 715.0 mAh g−1 after 800 cycles, with a capacity retention rate of 86.37%, which shows high cycle life.

Experimental study of friction coefficient of graphite for high-temperature gas-cooled reactors

High-temperature gas-cooled reactors, as highly regarded fourth-generation reactors, extensively utilize graphite materials. It is necessary to perform a study of the characteristics of the graphite materials aiming at optimizing the structural design and neutron physics calculation for the reactor. Thus, the investigation of the graphite friction coefficient is a crucial aspect of the research. This paper presents experiments on the graphite friction coefficient conducted using a specially designed experimental device that closely replicates the operational conditions of high-temperature gas-cooled reactors. The experimental data on the graphite friction coefficients under various atmospheric and temperature conditions are obtained. The graphite friction coefficient under a helium atmosphere demonstrates an initial increase followed by a decrease with rising temperature, reaching a maximum value of 0.17 at 200 °C. However, beyond 400 °C, the friction coefficient stabilizes gradually and fluctuates within the range of 0.03 to 0.06. Under a nitrogen atmosphere, the graphite friction coefficient exhibits the same temperature-dependent pattern as observed in helium. The peak value likewise occurs at 200 °C, measuring 0.23. At temperatures below 400 °C, the graphite friction coefficients in a nitrogen atmosphere surpass those in helium. While beyond 400 °C, the friction coefficients in a nitrogen atmosphere likewise fluctuate within the range of 0.03 to 0.06.

Recent progress in graphitic carbon nitride-based materials for antibacterial applications: synthesis, mechanistic insights, and utilization

Recent breakthroughs in graphitic carbon nitride (g-C3N4)-based materials have catalyzed the development of highly effective antibacterial strategies. This comprehensive review delves into the synthesis, mechanistic insights, and applications of g-C3N4 in the realm of antibacterial research. The introduction first highlights the importance of antibacterial materials, emphasizing the urgent need for innovative solutions in the face of bacterial infections and the escalating challenges posed by antibiotic resistance. Continuing, the structural attributes and distinctive characteristics of g-C3N4 are examined in detail, elucidating its inherent properties that make it a compelling candidate for antibacterial applications. Subsequently, we meticulously dissect various methods used in the synthesis of g-C3N4, encompassing both top-down and bottom-up approaches, offering valuable insights into the production of this promising nanomaterial. Furthermore, it delves deeper into the sterilization mechanisms of g-C3N4-based nanomaterials, encompassing a spectrum of strategies, including physical structure sterilization, photocatalytic antibacterial effects, enzymatic antibacterial processes, and the synergetic benefits that emerge from the fusion of these mechanisms. Then, it comprehensively examines the practical applications of g-C3N4-based nanomaterials in antibacterial endeavors, encompassing their pivotal roles in water purification, air purification, treatment of bacterial infections, and the development of antibacterial layers in diverse settings. In conclusion, we encapsulate the crux of our findings and provide a forward-looking perspective on the potential challenges and opportunities in the arena of g-C3N4-based materials for antibacterial applications. This review aspires to galvanize further exploration and innovation in the design of high-performance g-C3N4-based materials, thereby contributing to the progression of antibacterial solutions.

In Situ Chemical Modulation of Graphitization Degree of Carbon Fibers and Its Potassium Storage Mechanism.

Graphite is considered to be the most auspicious anode candidate for potassium ion batteries. However, the inferior rate performances and cycling stability restrict its practical applications. Few studies have investigated the modulating the graphitization degree of graphitic materials. Herein, a nitrogen-doped carbon-coated carbon fiber composite with tunable graphitization (CNF@NC) through etching growth, in-situ oxidative polymerization, and subsequent carbonization process is reported. The prepared CNF@NC with abundant electrochemical active sites and a rapid K+/electron transfer pathway, can effectively shorten the K+ transfer distance and promote the rapid insertion/removal of K+. Amorphous domains and short-range curved graphite layers can provide ample mitigation spaces for K+ storage, alleviating the volume expansion of the highly graphitized CNF during repeated K+ insertion/de-intercalation. As expected, the CNF@NC-5 electrode presents a high initial coulombic efficiency (ICE) of 69.3%, an unprecedented reversible volumetric capacity of 510.2 mA h cm-3 at 0.1 A g-1 after 100 cycles with the mass-capacity of 294.9 mA h g-1. The K+ storage mechanism and reaction kinetic analysis are studied by combining in-situ analysis and first-principles calculation. It manifests that the K+ storage mechanism in CNF@NC-5 is an adsorption-insertion-insertion mechanism (i.e., the "1+2" model). The solid electrolyte interphase (SEI) film forming is also detected.

In-situ synthesis and oxidation behaviors of Ti-xAl coatings by high-frequency induction heated combustion

Ti-xAl coatings (x=25, 33.3, 50, 66.7, and 75 at%) were fabricated in situ using high-frequency induction heating synthesis (HFIHCS). The process parameters for preparing Ti-Al coatings via HFIHCS were orthogonally optimized employing the finite element method. The effect of the aluminum content on the microstructures and phase compositions of Ti-Al coatings fabricated by HFIHCS, as well as their oxidation behaviors at 900℃ for 100 h was investigated. The results showed that the distribution of interfacial temperature difference was influenced by induced current (62.11%), relative density of compact (9.86%), and indenter material (28.03%). The minimum interfacial temperature difference was achieved with an induced current of 300 A, a graphite indenter material, and a compact density of 82.9%. The Ti-xAl coatings exhibited a core (Ti)-shell (TixAly) ring structure. The rise in aluminum content in the Ti-xAl coatings led to a gradual reduction in the titanium-rich phase, accompanied by a progressive increase in the aluminum-rich phase and the interface thickness of zones Ⅰ and Ⅱ. The porosities of Ti-xAl coatings containing over 50 at% aluminum exhibited an order of magnitude higher than those of Ti-xAl coatings with 50% aluminum or lower. The mechanisms of reaction, pore-forming, and interfacial diffusion for Ti-xAl coatings were predominantly controlled by dissolution-precipitation, thermal expansion of intrinsic pores within the cold-pressed compact and voids formed after molten aluminum flow, and liquid-solid co-diffusion, respectively. The increase in aluminum content in the Ti-xAl coatings led to in a gradual decrease in its oxidative weight gain, a shift in the oxidation kinetics from a linear-parabolic to a parabolic law, and an enhancement in preservation of internal core-shell characteristics and the likelihood of forming a protective layer of thin Al2O3. The oxidation behaviors of Ti-xAl coatings with a core-shell structure were co-controlled by the aluminum content and the porosity affected by the aluminum content.

Laser-Induced Copper/Carbon Nanocomposite from Anodically Electrodeposited Chitosan for H2O2 Sensing

This work presents anodically electrodeposited copper (Cu)/chitosan gel as a novel precursor for synthesizing a Cu/carbon nanocomposite through laser-induced carbonization. Metal/carbon nanocomposites offering advantageous properties compared to their individual counterparts stand out in various applications, particularly in those involving electrochemical phenomena. However, their synthesis often suffers from complicated and time-consuming synthesis procedures. Here, we integrate anodic electrodeposition and laser-induced carbonization to yield a rapid, simple, and inexpensive procedure for synthesizing metal/carbon nanocomposite. A precursor composite involving Cu-coordinated chitosan film is achieved through anodic electrodeposition on a copper anode. Irradiation by an infrared laser with optimized parameters results in the thermochemical decomposition of the Cu/chitosan composite, rapidly forming a nanocomposite material featuring highly graphitized and porous carbon materials. Elemental mapping confirms the formation of the nanocomposite, although no crystalline phases of copper are observed during X-ray diffraction. This can be attributed to the rapid nature of the laser-carbonization process. The nanocomposite material is further demonstrated for electrochemical sensing of hydrogen peroxide (H2O2), exhibiting a sensitivity of 2.65 mM−1 for concentrations ranging from 0.01 mM to 0.1 mM H2O2, and 0.01 ± 0.01 mM−1 for concentrations from 0.1 to 10 mM H2O2. These sensitivities are comparable to other non-enzymatic H2O2 biosensors. The finding of this work signifies a rapid and facile method for synthesizing metal/carbon nanocomposites with strong implications for the field of biosensors.

Multicomponent Reductive Coupling for Selective Access to Functional γ-Lactams by a Single-Atom Cobalt Catalyst.

Despite their significant importance to numerous fields, the difficulties in direct and diverse synthesis of α-hydroxy-γ-lactams pose substantial obstacles to their practical applications. Here, we designed a nitrogen and TiO2 co-doped graphitic carbon-supported material with atomically dispersed cobalt sites (CoSA-N/NC-TiO2), which was successfully applied as a multifunctional catalyst to establish a general method for direct construction of α-hydroxy-γ-lactams from cheap and abundant nitro(hetero)arenes, aldehydes, and H2O with alkynoates. The striking features of operational simplicity, broad substrate and functionality compatibility (>100 examples), high step and atom efficiency, good selectivity, and exceptional catalyst reusability highlight the practicality of this new catalytic transformation. Mechanistic studies reveal that the active CoN4 species and the dopants exhibit a synergistic effect on the formation of key acid-masked nitrones; their subsequent nucleophilic addition to the alkynoates followed by successive reduction, alkenyl hydration, and intramolecular ester ammonolysis delivers the desired products. In this work, the concept of reduction interruption leading to new reaction route will open a door to further develop useful transformations by rational catalyst design.