Thin Carbon Research Articles

In-situ observation on the δ to γ transformation behavior of carbon steels

In recent in-situ observations on the solidification of thin carbon steel experiments, the primary δ-phase appears to be highly undercooled into the single γ phase region of the phase diagram, where the massive δ to γ transformation occurred without the intervention of the liquid phase following a typical peritectic reaction. Whether such a massive transformation is the main mode, even in bulk steel alloys, is of prime importance because it would drastically change our view on the defect generation mechanism during steel solidification in continuous casting. In this research, the in-situ imaging technique using synchrotron white X-ray beam was conducted to investigate the effects of carbon content and the specimen thickness on the δ to γ transformation behaviors in the carbon steel. The moment of δ to γ transformation is identified through synchronized recording of Laue diffraction patterns and in-situ images. The relative average brightness (RAB) change during solidification was evaluated to analyze the transformation. The results revealed that hypo-peritectic steel grades predominantly underwent a massive transformation, while hyper-peritectic steel grades showed a combination of massive and diffusional transformations. The sudden drop in liquid fraction after massive transformation was detected, while diffusional transformation exhibited a gradual decrease in the present study. The findings demonstrated that specimen thickness influenced the transformation mode in hyper-peritectic steel grades. The study provides insights into the behavior of δ to γ transformation and its implications for carbon steel solidification processes.

Construction of layered SnS2 and g-C3N4 nanoarchitectonics towards pollution degradation and H2 generation

Two dimensional (2D)/2D heterostructures with much interface is advantage to improve the transfer of photogenerated carriers. In this paper, SnS2 nanosheets were horizontally grown on superior thin graphic carbon nitride (g-C3N4) nanosheets to construct 2D/2D heterostructures with enhanced photocatalytic performance. The g-C3N4 nanosheets (CN) were obtained by a two-step thermal polymerization at 600 and 700 °C. the growth of SnS2 nanosheets was then carried out using a solvothermal synthesis. Preparation parameters including temperature, reaction time, and precursor components were tested to get optimized SnS2/g-C3N4 composite sample 8SnS2-CN. A Z-scheme mechanism was proposed for the discussion of photocatalytic process. The degradation test of Rhodamine B (Rh B) indicated that the degradation rate of Rh B using sample 8SnS2-CN was twice quick compared with g-C3N4 nanosheets, in which Rh B degradation was completed within 15 min. The photocatalytic hydrogen production rate of sample 8SnS2-CN was about 6 times that that of sample CN, which is 1818.75 μmol g−1 L−1. Enhanced photocatalytic performance is ascribed to SnS2 deposited to form well-developed interface which improved the separation and transfer of photogenerated carriers. In addition, the growth of SnS2 was also expended the photo adsorption.

Electrochemical performance of hybrid supercapacitor device based on Mn-doped LiFePO4/C and imidazolium ionic liquid electrolyte

The electrochemical performance of lithium-ion hybrid supercapacitors (Li-HSCs) build with nanostructured LiMnxFe1-xPO4/C in an ionic liquid electrolyte system was analyzed to determine the effects of Mn doping on olivine structure. The construction of hybrid cells using ionic liquids is strategic due to their low vapor pressure, which inhibits the evolution of gas and leakage in the cell, and non-flammability. The Li-HSCs cells were assembled using as electrolyte an ionic liquid system consisting of lithium bis(trifluorosulfonyl)imide (LiTFSI) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonamide) (EMITFSI) at a concentration of 1 mol L−1; a carbon with mesopore structure (MESO) as capacitive electrode; and Mn-doped LiFePO4 olivines, i.e., LiMnxFe1-xPO4 (x = 0.01 ≤ x ≤ 0.10), as positive electrodes. The olivines were synthesized using a solvothermal method, resulting in pure nanostructured materials. Subsequently, a thin carbon layer was added from a carbon source and calcinated at 550 °C, as confirmed by XRD, FTIR, EDS, and TEM. The electrochemical characterization of LiMnxFe1-xPO4 active materials was performed using a standard lithium cell (3-electrode cell). The LiMn0.05Fe0.95PO4 presented the best properties. The electrochemical performance of Li-HSCs constructed using all LiMnxFe1-xPO4 (x = 0.01 ≤ x ≤ 0.10) based cathodes was then evaluated. The Li-HSC built with LiMn0.05Fe0.95PO4 showed the highest capacitance, power, and energy densities among all the evaluated cells, as also verified by the electrochemical characterization of the standard lithium cells. This cell was able to deliver an energy density of 43.1 W h kg−1 at 25.9 W kg−1 (power density), which was higher than the device constructed with the un-doped olivine, LiFePO4, which delivers 35.9 W h kg−1 at 23.2 W kg−1, as well as higher than other LiMnxFe1-xPO4 based cells. Additionally, the Li-HSC constructed with LiMn0.05Fe0.95PO4 showed 67 % of energy retention after 1000 cycles, a superior performance compared to Li-HSC prepared with the un-doped olivine, which retained 54 % of its initial energy after the same cycling process.

Hollow Nitrogen-Doped Carbon Spheres with Presiding Graphitic Nitrogen for Oxygen Reduction Reaction

Hollow nitrogen-doped carbons, a class of metal free electrocatalysts, offer a wide range of modifications due to their tunable diameter and carbon wall thickness. Herein, hollow nitrogen-doped carbon spheres (HNCS-1000) with numerous structural defects, thin carbon wall of about 8 nm, high (sp2-sp3)/sp3 bond ratio of 3.11 and graphitic-N proportion of 71.4% are prepared using a double pyrolysis strategy. When employed as ORR catalyst in O2-saturated 0.1 M KOH solution, HNCS-1000 retains high onset and halfwave potentials of 1.03 V and 0.88 V, respectively. In addition, it also demonstrates excellent stability/durability with 90.25% current density retention after 84000 s continuous chronoamperometric operation and only 33 mV loss in halfwave potential after 7000 CV cycles. Overall, the ORR performance of HNCS-1000 surpasses most of the previously reported nitrogen-doped carbon catalysts, and it is among the best catalysts for ORR in alkaline environment.

Selective hydrogenation of benzoic acid over bimetallic NiCo embedded in N‐doped carbon

AbstractThe selective hydrogenation of biomass‐derived benzoic acid (BA) to cyclohexane carboxylic acid (CCA) is vital to producing fine chemicals from renewable sources. Herein, a novel nitrogen‐doped carbon supported bimetallic catalyst (Ni1Co1/NC) was synthesized via a PVP‐assisted method to catalyze the selective hydrogenation of BA to CCA. Compared with the non‐doped Ni1Co1/C and single counterparts, Ni1Co1/NC exhibited a substantially enhanced activity, with 98.1% yield of CCA. The excellent performance was attributed to the NiCo synergistic effect and N‐doped thin carbon layer, which could increase the total proportion of Ni0 and Co0 species via donating electrons to Co and thus improve the H2 adsorption capacity, the hydrogenation activity of aromatic rings in BA and the stability. This work demonstrates a synergetic effect between NiCo bimetal and N‐doped thin carbon layer. This would pave the way for the rational design and synthesis of high‐performance non‐noble catalysts used in BA hydrogenation.

Fabrication and electrochemical performance of pseudocapacitive ABO2-type AgFeO2@C||K0.4MnO2. xH2O battery-type supercapacitive asymmetric cell for large-scale energy storage applications

To make effective utilization of renewable energy sources, a highly efficient large-scale energy storage solution is needed that can fill the gap between the batteries (high energy density) and the capacitors (high power density). Supercapacitors are being a bridge between batteries and capacitors, suffer from low energy density, and need to be further upgradation for utilization as a grid-level energy storage solution. A higher energy density can be achieved by constructing an asymmetric cell (ASC) in which both, the electrodes (positive and negative) are worked in a separate potential window. Pseudocapacitive ABO2-type electrode in the form of an asymmetric cell (ASC), AgFeO2@C//K0.4MnO2. xH2O is envisaged here as high high-performing battery-type supercapacitor cell to develop large-scale energy storage solutions. Herein, crystallites of K0.4MnO2. xH2O were successfully grown via a facile chemical flux method that gives a birnessite-type layered structure having a lateral dimension in the range of 2–5 μm. Thus, the incorporation of birnessite- K0.4MnO2. xH2O as a positive electrode (cathode), and the thin carbon layer coated AgFeO2 as a negative electrode (anode) in aqueous 1 M Na2SO4 electrolyte in the form of ASC exhibited high energy density as well as power density with excellent cycle life up to cell voltages close to 1.8 V. The presented battery-type supercapacitor cell can deliver a maximum energy density equivalent to 61.51 Wh kg−1 and a power density of 450 W kg−1 at a current density of 0.5 A g−1, which is substantially larger than the previously reported aqueous electrolyte-based asymmetric supercapacitor devices. The newly developed high-voltage aqueous asymmetric battery-type supercapacitors device has a low-cost and enviro-friendly, that can replace currently market-available hazardous lead-acid batteries for fast energy storage applications.

High-temperature adaptive through-silicon via with pyrolyzed carbon via-sealing plates for packaging 3D carbon nanostructure-based devices fabricated using C-MEMS

Through-silicon via (TSV) is a key packaging technology that facilitates the 2.5D/3D integration of microelectromechanical system (MEMS) devices. Among various MEMS technologies, C-MEMS enables micro/nanoscale 3D carbon structure manufacturing using high-temperature (600–1200 °C) pyrolysis. These high-temperature conditions limit the application of conventional TSV technologies to C-MEMS devices. This study presents a novel TSV with carbon via-sealing plates that are adaptable to C-MEMS device packaging. Via holes are drilled before integrating the MEMS device to protect the delicate micro/nanoscale structures. Moreover, the topside via inlet is sealed with a thin conductive pyrolyzed carbon plate to prevent the contamination of the via interior during the C-MEMS process and ensure an electrical connection between the devices and the vias. After integrating the C-MEMS devices, TSV fabrication is completed by coating the via inside with a metal layer from the wafer's bottom side, achieving a conductance per unit area of approximately 327 S/mm2 (via diameter = 33 μm, length = 100 μm). The applicability of the proposed wafer-level TSV technology to C-MEMS devices is then verified through the implementation of a suspended carbon nanowire-based gas sensor integrated with the developed TSV, which exhibits excellent signal transmission. Furthermore, the proposed TSV packaging technology can be applied to various micro/nanofabrication technologies because of its high-temperature/wet-process compatibility and cost-effective fabrication.

Measuring the interlaminar fracture toughness of thin carbon fiber/polyamide6 composites using adhesively bonded stiffeners

The present work investigates the interlaminar fracture toughness of a thin unidirectional carbon fiber-reinforced/polyamide6 (CF/PA6) composite laminate. Aluminum (Al) stiffening beams are adhesively bonded on both sides of the thin laminate to avoid undesirable large deformations during the subsequent double cantilever beam tests. Experimentation with various surface treatment techniques and different adhesives is presented, from which it is concluded that the mode I fracture toughness of the CF/PA6 laminate is always higher than the fracture toughness of the adhesives used. Consequently, the crack initiates at the Al–composite interface. A finite element (FE) model is proposed, and quantitative results for the fracture toughness of the laminate are provided (e.g., GIc,ini=2.1N/mm). Overall, the study highlights the challenges in the adhesive joining of stiffening beams to CF/PA6 surfaces, ways to improve adhesion, and the FE simulation as an alternative to determining the interlaminar fracture toughness of such thin laminates.

Synthesis of size-controlled SiOC ceramic materials by silicone oil-based emulsion method for anodes in lithium-ion batteries

A submicron spherical silicon oxycarbide (SiOC) material for lithium-ion battery anodes was successfully synthesized by employing a facile synthetic strategy that used economical silicone oil as a starting material, an emulsion method, and the subsequent pyrolysis of silicone oil emulsion at 900 °C. Although most previous studies concerning silicone-oil-based SiOC exhibited irregular and uncontrollable size after synthesis, the developed emulsion-driven SiOC preparation achieved regular submicron spherical particles. Furthermore, the emulsifier used herein formed a thin carbon coating layer after the synthesis procedure and contributed to the electrochemical performance during battery operation. The spherical submicron size-controlled SiOC material had superior capacity retention compared to pristine SiOC obtained without the emulsion method, owing to the suppressed micro-cracks induced by accumulation of mechanical stress during repeated cycles and prevention of direct contact with the electrolyte by the thin carbon-coating layer.

Dressing the manganese dioxide cathode with close-fitting thin carbon film to suppress the dissolution and expansion

Dressing the manganese dioxide cathode with close-fitting thin carbon film to suppress the dissolution and expansion

Deposition and Morphology Control of Carbon Film through Electrochemical Reduction of Carbonate Ions in Molten LiCl

Synthesis of a compact, uniform and thick carbon film on nickel substrate were conducted by electrochemical reduction of carbonate ions in LiCl-Li2CO3 molten salt. It was found that the carbon is consistently formed into structure of wire and sphere particle. The uniformity and compactness of the carbon film were found to be dependent on the applied current density, electricity, and the electrolysis method. At lower current densities, the carbon tended to grow locally, resulting in larger-sized wires and particles. At higher current density, a relatively uniform and thin carbon film can be synthesized at the beginning but soon changed to a cluster-like structure. The contradiction between current density and carbonate ions‘ diffusion limit make it is impossible to obtain a compact and uniform film by using constant current electrolysis. By applying pulsed current electrolysis with an average current density of 10 mA cm−2 and a peak current density of 200 mA cm−2, a compact and uniform carbon film with a thickness of approximately 10 μm was successfully prepared.

Cryo‐TEM Study of High‐Performance Iron Difluoride Cathode Enabled by Low Temperature CVD Carbon Coating

AbstractMetal fluorides (MFs) are regarded as high‐capacity conversion cathode materials for next‐generation lithium‐ion batteries with high energy density. However, these cathodes suffer from poor electronic conductivity, sluggish reaction kinetics, and deleterious cathode solid electrolyte interface (CEI) formation, which may cause rapid cell degradation upon cycling. Herein, a low temperature chemical vapor deposition (CVD) carbon coating technology is successfully achieved to coat MFs‐FeF2 with a thin amorphous carbon layer, which promotes the formation of a stable CEI with improved electronic and ionic transport property. Consequently, a discharge capacity higher than 450 mAh g−1 of the CVD coated FeF2 is achieved with a capacity retention at about 75% after 2500 cycles in a saturated electrolyte. Moreover, an unprecedented cycling performance with the discharge capacity of 350 mAh g−1 after 500 cycles in a super diluted electrolyte is also achieved. Advanced cryo‐electron microscopy reveals that the carbon coating significantly suppresses the undesirable CEI formation and promotes the formation of a thin CEI with excellent chemo‐mechanical property. This work provides a feasible technology to stabilize the important interface on MFs and offers a new strategy to accelerate the commercial adoption of such cathodes.

Fabrication of nitrogen-doped carbon on NiCoP electrocatalyst with flower-like structure for efficient hydrogen evolution reaction in alkaline solution

The development of hydrogen evolution catalysts with low cost, high activity, and outstanding stability has become an urgent need. Herein, we reported a novel and effective strategy for the in situ growth of NiCoP nanoparticles encapsulated in ultrathin nitrogen-doped porous carbon on nickel foam (NiCoP@NC/NF). Compared with NiCoP/NF, the NiCoP@NC/NF presented a much larger electrochemically active surface area (ECSA) (1402.9 cm2 mg−1), more abundant intrinsic HER active sites and lower charge-transfer resistance, leading to superior catalytic activity. The as-prepared NiCoP@NC/NF electrode exhibited extremely low overpotential η10 (77 mV) and Tafel slope (62.1 mV dec−1) for HER in 1.0 M KOH as the electrolyte. Importantly, due to the thin nitrogen-doped carbon layer, NiCoP@NC/NF showed considerably enhanced stability under the harsh conditions of long-term reaction. Density functional theory (DFT) calculations have indicated that the nitrogen-doped carbon of NiCoP@NC/NF permitted moderate trapping of hydrogen atoms and easy desorption of the resulting H2. Such impressive HER performance of the hybrid electrocatalyst is mainly attributed to the collective effects of elemental doping engineering between NC and NiCoP, the enlarged surface area/exposed catalytic active sites, and the lower transfer resistance due to the nitrogen-doping carbon. The present work proposed a controllable and feasible strategy for synthesizing bimetallic phosphides with unique morphology and high HER performance.

Hybrid tungsten–carbon 2D nanostructures via in situ gasification of carbon substrates driven by ebeam irradiation of WO2.9 microparticles

Since the transmission electron microscope (TEM) has the capacity to observe the atomic structure of materials, in situ TEM synthesis methods are uniquely suited to advance our fundamental understanding of the bottom-up dynamics that drive the formation of nanostructures. E-beam induced fragmentation (potentially identified as a manifestation of Coulomb explosion) and electron stimulated desorption are phenomena that have received attention because they trigger chemical and physical reactions that can lead to the production of various nanostructures. Here we report a simple TEM protocol implemented on WO2.9 microparticles supported on thin amorphous carbon substrates. The method produces various nanostructures such as WC nanoparticles, WC supported films and others. Nevertheless, we focus on the gradual graphitization and gasification of the C substrate as it interacts with the material expelled from the WO2.9 microparticles. The progressive gasification transforms the substrate from amorphous C down to hybrid graphitic nanoribbons incorporating W nanoparticles. We think these observations open interesting possibilities for the synthesis of 2D nanomaterials in the TEM.

Analysis of Thin Carbon Reinforced Concrete Structures through Microtomography and Machine Learning

This study focuses on the development of novel evaluation methods for the analysis of thin carbon reinforced concrete (CRC) structures. CRC allows for the exploration of slender components and innovative construction techniques due to its high tensile strength. In this contribution, the authors have extended the analysis of CRC shells from existing research. The internal structure of CRC specimens was explored using microtomography. The rovings within the samples were segmented from the three-dimensional tomographic reconstructions using a 3D convolutional neural network with enhanced 3D data augmentation strategies and further analyzed using image-based techniques. The main contribution is the evaluation of the manufacturing precision and the simulation of the structural behavior by measuring the carbon grid positions inside the concrete. From the segmentations, surface point clouds were generated and then integrated into a multiscale framework using a parameterized representative volume element that captures the characteristic properties of the textile reinforcement. The procedure is presented using an example covering all necessary design steps from computed tomography to multiscale analysis. The framework is able to effectively evaluate novel construction methods and analyze the linear-elastic behavior of CRC shells.

Activating and stabilizing Co sites in CoP for triggering oxygen electrocatalysis in zinc-air battery

Catalysts with high activity and corrosion-resistance are desirable for oxygen reduction and evolution reactions (ORR/OER) in rechargeable zinc-air batteries (ZABs). Herein, via an etching-phosphating-annealing strategy, CoP is in situ formed in hollow carbon-nanobox, both of which are wrapped by a thin nitrogen-doped carbon layer (CoP/HNBs@NCL). Tannic acid etches ZIF-67 nanobox to release Co2+ and 2-methylimidazole to generate hollow structure. As-marked CoP/HNBs@NCL-2 (271.9 m2 g−1) exhibits robust activities towards ORR (half-wave potential of 0.88 V) and OER (overpotential of 0.36 V), which outperforms many non-precious metal catalysts due to the strong interactions between CoP and N-species and the smooth mass transfer via the porous hollow structure. Even at high potentials (OER), HNBs@NCL framework can still relieve the leaching of Co species (leaching ratio of 15.5 % after 6 h) to obtain high corrosion resistance and stability. Theoretical calculations reveal that N atoms enhance the electron delocalization degree of Co sites in CoP to lower energy barriers and balance adsorption free-energies of O-intermediates to enhance oxygen electrocatalysis. Notably, ZAB with CoP/HNBs@NCL-2 air-electrode exhibits high peak power density (139.8 mW cm−2) and charge–discharge cycling stability (132 h). This work presents a reliable protocol to design hollow electrocatalysts with desirable bifunctional activity and stability for ZABs.

Nitrogen-doped hollow mesoporous carbon spheres for efficient oxygen reduction

Extensive investigations have been devoted to nitrogen-doped carbon materials as catalysts for the oxygen reduction reaction (ORR) in various conversion technologies. In this study, we introduce nitrogen-doped carbon materials with hollow spherical structures. These materials demonstrate significant potential in ORR activity within alkaline media, showing a half-wave potential of 0.87 V versus the reversible hydrogen electrode (RHE). Nitrogen-doped hollow carbon spheres (N-CHS) exhibit unique characteristics such as a thin carbon shell layer, hollow structure, large surface area, and distinct pore features. These features collectively create an optimal environment for facilitating the diffusion of reactants, thereby enhancing the exposure of active sites and improving catalytic performance. Building upon the promising qualities of N-CHS as a catalyst support, we employ heme chloride (1 wt%) as the source of iron for Fe doping. Through the carbonization process, Fe-N active sites are effectively formed, displaying a half-wave potential of 0.9 V versus RHE. Notably, when implemented as a cathode catalyst in zinc-air batteries, this catalyst exhibits an impressive power density of 162.6 mW cm−2.

Damage Propagation and Residual Strength of Simple Block-Loaded CFRP Plates with Circular Holes under Tension–Tension Fatigue Conditions

Holes and their effects on the fatigue behavior and damage propagation of thin-walled structural components remain objects of research. In this paper, the previously untreated effect of round holes in thin plain-woven carbon fiber-reinforced plastic plates subjected to simple block loading is examined, and the implication on both damage propagation and residual tensile strength is investigated. Using three-dimensional digital image correlation, the damage propagation in the performed experimental tests is acquired, and the damage size is quantified. The evaluations reveal a relationship between the damage propagation and applied load level, for which an empirical model has been previously established by the authors. As the number of cycles increases, a saturation behavior is found. Once the increased load is imposed on the plate, damage propagation resumes, leading to further damage propagation that can be described with the same empirical model as the initial damage propagation, including renewed saturation behavior. The subsequent experimental tests to determine the residual tensile strength reveal a positive effect of the existing damage size, as the ultimate load significantly exceeds the ultimate load of the non-damaged plate.

Effects of Zn-ZnO Core-Shell Nanoparticles on Antimicrobial Mechanisms and Immune Cell Activation.

The deposition of zinc-zinc oxide nanoparticles (Zn-ZnO NPs) onto porous Ta2O5 surfaces enriched with calcium phosphate by DC magnetron sputtering was investigated to improve the surface antimicrobial activity without triggering an inflammatory response. Different sizes and amounts of Zn NPs obtained by two optimized different depositions and an additional thin carbon (C) layer deposited over the NPs were explored. The deposition of the Zn NPs and the C layer mitigates the surface porosity, increasing the surface hydrophobicity and decreasing the surface roughness. The possible antimicrobial effect and immune system activation of Zn-ZnO NPs were investigated in Candida albicans and macrophage cells, respectively. It was found that the developed surfaces displayed a fungistatic behavior, as they impair the growth of C. albicans between 5 and 24 h of culture. This behavior was more evident on the surfaces with bigger NPs and the highest amounts of Zn. The same trend was observed in both reactive oxygen species (ROS) generation and loss of C. albicans' membrane integrity. After 24 h of culture, cell toxicity was also dependent on the amount of the NPs. Cell toxicity was observed in surfaces with the highest amount of Zn NPs and with the C layer, while cells were able to grow without any signs of cytotoxicity in the porous surfaces with the lowest amount of NPs. The same Zn-dose-dependent behavior was noticed in the TNF-α production. The Zn-containing surfaces show a vastly inferior cytokine secretion than the lipopolysaccharide (LPS)-stimulated cells, indicating that the modified surfaces do not induce an inflammatory response from macrophage cells. This study provides insights for understanding the Zn amount threshold that allows a simultaneous inhibition of the fungi growth with no toxic effect and the main antimicrobial mechanisms of Zn-ZnO NPs, contributing to future clinical applications.

Magnetron sputtering process for deposition of multilayered thin diamond-like carbon films with silver nanoparticles for anti-reflective coatings and refractometric sensing

Multilayered film stacks serving optical applications usually require multiple target sources for deposition. In this work, we present a convenient method for the deposition of single- and multilayered thin films with varying diamond-like carbon (DLC) and silver content employing a single magnetron in the deposition system. For this, a reactive magnetron sputtering system was utilized and the silver target was poisoned based on desired structure: clean target and argon gas resulted in a pure silver film, completely poisoned target and acetylene and argon gas resulted in a DLC film, and anything in between resulted in a nanocomposite DLC:Ag film. The films were deposited on fused quartz, crystalline silicon, and porous anodized aluminum oxide substrates. We investigated the optical properties of these films and showed their applications for anti-reflective, black-appearing coatings and refractometric sensors, both experimentally and by simulation methods.