Carbon Phase Research Articles

Spectroscopic Signatures of Ultra-Thin Amorphous Carbon with the Tuned Disorder Directly Grown on a Dielectric Substrate.

The reduced structural complexity of atomically thin amorphous carbons makes it suitable for semiconductor technology. Inherent challenges arise from transfer processes subsequent to growth on metallic substrates, posing significant challenges to the accurate characterization of amorphous materials, thereby compromising the reliability of spectroscopic analysis. Here this work presents a novel approach: direct growth of ultra-thin amorphous carbon with tuned disorder on a dielectric substrate (SiO2/Si) using photochemical reaction and thermal annealing process with a solid precursor. This work characterizes the amorphous carbon films' disorder using spectroscopic techniques, such as X-ray photoelectron spectroscopy, Electron energy loss spectroscopy, and Raman spectroscopy, which offer greater convenience compared to microscopy-based studies. This method, rooted in comprehensive spectroscopic characterization, elucidates characteristic signatures inherent to the amorphous carbon films. These findings reveal that Raman spectroscopy is particularly effective in identifying the amorphous phase of atomically-thin carbon. Additionally, I-V characterization and high-frequency dielectric measurements showcase the potential application of directly grown amorphous carbon films in the semiconductor industry, where nanometer-level thin conductors and dielectrics are commonly utilized. This transfer-free characterization method provides a useful tool to find the correlation between atomic structure and electrical/optical properties, giving valuable insights into comprehensive crystallographic fundamental research.

High-efficiency photocatalyst C@TiO2 with the synergy effect of carbon doping and phase transformation

High-efficiency photocatalyst C@TiO2 with the synergy effect of carbon doping and phase transformation

Improving properties of Portland cement-blast furnace slag blended paste through sodium bicarbonate-induced carbonation

The addition of NaHCO3 has the potential to enhance properties of concrete by facilitating internal carbonation. This study investigates the effects of the incorporation of NaHCO3 into ordinary Portland cement-blast furnace slag paste. The results show that the addition of NaHCO3 had an impact on the hydration process and increased the heat of hydration on all the slag samples. NaHCO3 caused internal carbonation and facilitated the formation of calcium carbonate and different carbon-based AFm phases, such as monocarbonate. The incorporation of NaHCO3 improved the pore structure of the paste and enhanced resistance against chloride penetration. The chloride migration coefficient of the Portland cement paste sample was reduced up to 96.5% with the incorporation of 2% NaHCO3 at 70% slag replacement. The compressive strength of the samples also showed an improvement with 1% NaHCO3 addition increasing the early age strength and 2% NaHCO3 addition increasing the matured age strength.

Structural regulation and sodium storage mechanism of high-performance non-graphitic carbon derived from semi coke

Non-graphitic carbon (NGC) is considered as one of the most promising anodes for sodium-ion batteries (SIBs) because of its low cost and abundant reserves. Nevertheless, there is significant debate regarding the contribution mechanism of sloping and plateau capacity. Herein, a series of NGC with adjustable defect concentration, carbon phases and pore structure are synthesized with semi-coke as precursor to explore the sodium storage mechanism and an “adsorption-insertion-filling” model is proposed based on the in-depth analysis of microstructure and electrochemical behaviors. The very attraction about this work is that the entire discharge curve is divided into three regions for analysis, and the corresponding cause for each region is traced. To be specific, the defects and disordered structure contribute to the surface-controlled absorption behavior in the sloping region >0.1 V, the pseudo-graphitic structure shows diffusion-controlled insertion behavior in the plateau region between 0.1 and 0.05 V, and the closed pores formed by curved graphite-like structure provide plateau capacity (<0.05 V) through the filling of quasi-metallic sodium. This study provides theoretical education for the optimization of NGC anode structure and a novel approach for the excessive value-added utilization of semi coke.

Hydration mechanism of cement in natural gas hydrate layer regulated by dodecanol @ spherulite-type calcium carbonate phase change composite materials

Hydration mechanism of cement in natural gas hydrate layer regulated by dodecanol @ spherulite-type calcium carbonate phase change composite materials

An oxycarbide-derived-carbon supported nickel ferrite/copper tungstate ternary composite for enhanced electrocatalytic activity towards the oxygen evolution reaction.

This work integrates a unique porous carbon with a binary heterostructured NiFe2O4/CuWO4 composite to enhance electrocatalytic activity towards the oxygen evolution reaction. The NiFe2O4/CuWO4 binary heterostructure was prepared through the conventional co-precipitation method. The porous carbon with turbostratic order was obtained by the selective etching of SiO2 nanodomains from preceramic polymer-derived SiOC. Finally, an optimum ternary NiFe2O4/CuWO4/C composite was prepared through hydrothermal treatment. Microstructural findings reveal that NiFe2O4/CuWO4 nanocomposite particulates are distributed homogeneously within the porous carbon matrix. Electrochemical findings reveal that the optimum composite with uniform carbon distribution requires an overpotential of 360 mV to attain a current density of 10 mA cm-2 with the lowest Tafel slope of 43 mV dec-1 as opposed to 450 mV and 55 mV dec-1, respectively, for the composites without carbon. The ternary composite demonstrated a stable potential over a prolonged period of 24 hours with enhanced mass activity. The improved electrocatalytic efficiency of the material is attributed to the presence of graphitic carbon and ample porosity within the additive carbon phase, which enhances the catalyst-electrolyte interaction interface area and electronic conductivity.

Carbon Nanotubes-Titanium Diboride/Copper (CNTs-TiB2/Cu) Laser Cladding Layer with Enhanced Tribo-Electrical Property on Wind Turbine Pitch Slip Ring

Wind turbine pitch slip ring requires excellent tribo-electrical properties, including low friction and wear, high current transmission efficiency, low power loss, and contact resistance. To improve the tribo-electrical property, a carbon nanotubes-titanium diboride/copper (CNTs-TiB2/Cu) coating was prepared on slip ring surface by laser cladding. Microstructure, dilution rate, microhardness, tribo-electrical property, and power transmission property of cladding layer were analyzed. Optimal metallurgical bonding was achieved at a laser power of 900 W, resulting in a dilution rate of 14.5%. Elemental Ti diffused from the substrate into the coating, forming a hard titanium carbon (TiC) phase that significantly improved both friction reduction and wear resistance. Additionally, the formation of Cu3Ti increased the electrical conductivity of the cladding layer. The contact resistance was reduced by 30% to below 0.06 Ω, while the current transmission efficiency improved by 25%, exceeding 90%.

Novel Q-Carbon Anodes for Sodium-Ion Batteries

The lack of a standard anode for sodium-ion batteries (SIBs) has greatly hindered their applications. Herein, we show that a novel phase of carbon, namely Q-carbon, is an effective anode material for sodium-ion batteries. The Q-carbon, which is a metastable phase of carbon consisting of about 80% sp3- and 20% sp2-bonded carbon, is synthesized by nonequilibrium pulsed laser annealing and arc-discharge methods. Two types of Q-carbons, Q1 and Q2, were evaluated as anode material for SIBs. Q1 had a slow quench and was used as the control, whereas Q2 was Q-carbon with a rapid quenching. Q1 exhibits a high initial columbic efficiency of 81% and a low-capacity retention of less than 60%, whereas Q2 has a low initial columbic efficiency of 58% and a high-capacity retention of 81%. Q2 exhibits a stable capacity of 168 mAh·g−1 at a cycling rate of C/3 (124 mA·g−1), which is comparable to other hard carbon anodes reported in the literature. This unique synthesis method opens a pathway for the further tuning of Q-carbon with higher trapping/charging of Na+ ions in improved SIBs.

Anomalous Thermal Transport in Compressed Carbon Phases

Anomalous Thermal Transport in Compressed Carbon Phases

Investigating the Timing of Carbonate Precipitations and Their Potential Impact on Fossil Preservation in the Hell Creek Formation

Because fossilized skeletal remains and enclosing sedimentary rocks experience similar diagenetic conditions (i.e., temperature, pressure, and pore fluid interaction,) enclosing sedimentary rocks may provide insight into bone diagenesis. A fossil assemblage, including in situ dinosaur fossils, was discovered in Makoshika State Park near Glendive, MT. Fossil-bearing sandstone is a crevasse splay deposit, and fossils show no sorting or preferred orientation. Bone-bearing sandstone exhibits evidence for intense diagenesis, suggesting a maximum temperature of ~90 °C. Concretion associated with fossils includes two distinctive matrices: dark- and light-colored matrices. Another concretion was found in channel sandstone near the base of the outcrop. These carbonate phases have distinctive isotopic compositions; δ13C values for dark-colored matrices, light-colored matrices, and spheroidal concretion are −7.5, 2.1, and −22.4‰ (VPDB), respectively, and their δ18O values are 16.4, 25.9, and 17.8‰ (VSMOW), respectively. In contrast, fossilized bone δ13C and δ18O values were −4.4‰ (VPDB) and 20.6‰ (VSMOW), respectively, suggesting fractionation with pore fluid was limited. Early carbonate precipitation evidenced by grain coating may have reduced interaction between pore fluids and fossils. Although concretion formation and permineralization do not appear to directly aid in fossil preservation, concretions preserve valuable evidence for diagenetic history.

Biocompatibility and Antibacterial Potential of Tetrahedral Amorphous Carbon (ta-C) Coatings on CoCrMo Alloy for Articulating Implant Surfaces.

Premature implant failure, a critical concern in biomedical applications, is often attributed to poor biocompatibility and vulnerability to bacterial colonization. These issues are addressed by creating an endoprosthetic material with natural biocompatibility and antibacterial properties. In this invitro study, the relaxed and unrelaxed tetrahedral amorphous carbon (ta-C) coatings were examined, both fabricated by the improved patented Pulsed Laser Deposition (PLD) technology. The chemical composition, surface roughness, hardness, topography, and wettability were analyzed. The ta-C surfaces were incubated by MM6 cells, E. coli and S. capitis bacteria for 24 h. PCR assessed the inflammatory response in MM6 cells, while fluorescence microscopy quantified adhering bacteria, and scanning electron microscopy examined local adhesion behavior. The results demonstrate comparable carbon phase composition, wettability properties, and hardness for both relaxed and unrelaxed ta-C. However, relaxed ta-C coating exhibited significantly fewer defects in terms of both quantity and quality, along with an antibacterial effect against E. coli. This suggests that the relaxed ta-C coating could contribute to the development of an endoprosthesis, preventing adverse biological reactions and implant-related infections, thus improving the longevity of the prosthesis.

Research on the fabrication of high-quality patterned diamond using femtosecond laser

Diamond, known for its exceptional thermal, electrical, and mechanical properties, is widely used in precision machining tools, MEMS, and electronic devices. However, because of its extreme hardness and chemical inertness, diamond machining is highly challenging. Femtosecond laser technology, with its high instantaneous energy and minimal heat-affected zone, has emerged as an effective method for the precision machining of diamond. This study explores the application of 1026 nm and 513 nm femtosecond lasers in diamond grooving. The experimental results indicate that with increasing laser energy density, both groove width and depth increase, accompanied by a rise in amorphous carbon and graphite contents, resulting in increased tensile stress and decreased crystallinity in the machined region. Notably, the 513 nm laser demonstrates higher precision, achieving narrower grooves suitable for fine machining of diamond. Molecular dynamics simulations and experimental data reveal that the formation of amorphous carbon and graphite phases is the primary mechanism for deep ablation, and no significant anisotropy is observed during the process, allowing for the uniform fabrication of micro-nanostructures. TEM analysis confirms the presence of amorphous carbon and nanocrystalline diamond at the groove bottom, indicating phase transformation and also the formation of nanoscale diamond particles in regions of concentrated femtosecond laser energy. This study provides experimental and theoretical support for the high-quality fabrication of micro-nano structures on diamond, with significant implications for its advanced applications.

Machine learning enabled discovery of superhard and ultrahard carbon polymorphs

The demand for multifunctional materials has motivated the move from near-equilibrium materials to metastablei.e.out-of-equilibrium phases that can meet several desired target properties. The search for such metastable phases with exotic properties is non-trivial and often serendipitous. Inverse design approaches based on evolutionary search have been powerful tools, but such traditional searches have focused on identifying primarily stable and metastable materials with the lowest enthalpy. The inverse design of materials, with a focus on a desired property such as, for example, hardness is a challenging task because of the expensive computational cost involved in sampling multiple structures. The recent advances in machine learning have brought new powerful AI techniques to the forefront which can potentially revolutionize the inverse design and discovery of materials, especially metastable phases capable of meeting multifunctionality.In this work, we develop and apply an automated reinforcement learning workflow for inverse design that integrates first principles physics and atomistic simulations with machine learning (ML), and high-performance computing to allow rapid exploration of the superhard and ultrahard metastable phases of Carbon. We demonstrate an automatic machine learning based inverse design workflow to map new undiscovered metastable states ranging from near equilibrium to those far-from-equilibrium that satisfy multiple property objectives, specifically bulk moduli, shear moduli and hardness. We create a comprehensive library of carbon stable and metastable phases with varying hardness and subsequently shortlist 10 top performing candidate carbon structures, including two newly reported phases, based on their hardness and characterize their temperature dependent mechanical properties.A neural network model is built using featurization of allotropes of carbon to predict the quasi-harmonic Gibbs free energies. The Gibbs free energies of the top performing phases are analyzed to get an estimate of the experimental synthesizability of these superhard and ultrahard carbon phases.In general,we show using machine learning based inverse design approaches how hitherto inaccessible metastable states can be identified and potentially synthesized to meet the demand for multifunctional materials.

Achieving superior wear and corrosion resistance in FeCoNiCrNC films via nitrogen and carbon dual anions incorporation

Developing film materials thatcombine toughness, wear resistance, and corrosion resistance is a major challenge in the field of surface protection. Doping non-metallic elements such as nitrogen and carbon into high-entropy alloy films is expected to improve their overall performance. In this study, we successfully prepared nitrogen and carbon co-doped FeCoNiCrNCx high-entropy composite films using reactive magnetron sputtering. We systematically investigated the effects of different carbon concentrations on the structure, mechanical properties, friction, and corrosion resistance of the films. The results show that compared to carbon-free films, FeCoNiCrNCx high-entropy composite films with low carbon content (1.2 at.%) have remarkable characteristics, including high hardness (15.1 GPa), good toughness, excellent wear resistance (2.19 × 10-7 mm3N-1m−1), and corrosion resistance. As the carbon content increasing further, the precipitation of the amorphous carbon phase decreases hardness and toughness, reducing wear and corrosion resistance. The exceptional wear and corrosion resistance of low-carbon films make them highly promising for marine equipment protection and similar applications.

Seed-Assisted Hydrothermal Synthesis of Monodispersed Au@C Core–Shell Nanostructures for Enhancing Thermal Diffusivity of Water-Based Nanofluids

Au@C core–shell nanostructures (Au@C-NS) were synthesized through a low-temperature seed-assisted hydrothermal approach using glucose as carbon source. The material characterization and chemical analysis confirm that the synthesis method allows to obtain uniform core–shell nanostructures constituted by a crystalline metal core and an amorphous carbon shell. Depending on the synthesis conditions, their average size ranges from 146 nm to 342 nm with relative standard deviation as low as 7 %. It is proposed that the characteristic monodispersity results due to a high nucleation rate of the carbon phase at the liquid–solid interface. The obtained monodisperse Au@C-NS were used to prepare water-based nanofluids with superior heat transport properties. The thermal lens analysis shows that the thermal diffusivity of Au@C nanofluids is 9.5 % and 31.3 % higher than their Au nanofluids counterparts and pure water, respectively, at particle concentration of 285 × 1011 ml−1. Phonon-related interactions at the metal cores and carbon shells interfaces are proposed as the heat transport mechanism behind the thermal diffusivity enhancement of the Au@C water-based nanofluids.

Structural evolution and magnetic, optical, and optoelectronic properties changes in annealed Co0.5Sr0.5Fe2O4 nanoparticles: A comprehensive study

A sample of Co0.5Sr0.5Fe2O4 nanoparticles was synthesized by the coprecipitation technique to explore the effect of annealing on the structure and some physical properties of the produced material. The coprecipitated sample consists of an orthorhombic strontium carbonate phase and the required cubic Co0.5Sr0.5Fe2O4. Annealing at elevated temperatures (900 °C) leads to the formation of cubic and hexagonal phases. This crystal structure was confirmed by X-ray diffraction analysis (XRD). The accuracy of the cation distribution of the cubic phase determined from the Rietveld analysis of XRD patterns is demonstrated by matching the experimental and theoretical lattice constants. There are several noticeable changes in aspects as the annealing temperature goes up. The transmission electron microscopy (TEM) images indicated that heating substantially affects the growth and densification of the smaller nanoparticles. There is a drop in the longitudinal and transverse wave velocities, bulk, rigidity, Young's moduli, Poisson ratio (σ), and Debye temperature (θD) with annealing and grain growth. The saturation magnetization and coercive field are enhanced with annealing. The particle size distribution calculated from TEM is confirmed and supported by the switching field distribution. The indirect optical bandgap energy (Eg) decreased with annealing. The present study concentrated on the thermal treatment impacts on various optical parameters, such as the refractive index and extinction coefficient. The optoelectrical parameters, such as the dielectric constant, dielectric loss, and optical and electrical conductivity, were extensively investigated, giving valuable insights, and their results were interpreted. These findings suggest potential applications in magnetic storage, sensors, and optoelectronics fields.

Moringa Oil and Carbon Phases of Different Shapes as Additives for Lubrication

Vegetable oils in the lubricant field are largely studied. Their efficiency depends on their viscosity parameters and their fatty acid composition. The actions of moringa oil used as a lubricant base and as a lubricant additive have been shown in this work. Graphite, carbon nanofibers, and carbon nanodots are carbon phases of different shapes used as solid additives. The tribological performances of lubricant blends composed of between 0.5 and 1 wt.% of particles have been evaluated using a ball-on-plane tribometer under an ambient atmosphere. No additional surfactant was used. The positive and important actions of a small amount of moringa oil added in the lubricant formulas are demonstrated. The results obtained allow us to point out the influence of the type and shape of particles. Physicochemical investigations allow us to propose a synergistic effect between the particles and moringa oil as additives in dodecane.

Experimental enhancement study of thermophysical properties of ternary carbonate phase change material with multi-dimensional nanoparticles

Carbonates have great application potential as heat transfer and thermal energy storage media in the development of future phase change materials. This paper gives thermophysical properties enhancement study on ternary carbonates in liquid state by adding aluminum oxide nanoparticles, multi-walled carbon nanotubes, graphene nanosheets, and experimentally evaluate the performance strengthen ability of multi-dimensional nanoparticles. The thermal diffusivities and specific heats of the prepared samples by the water solution method are determined using the laser flash technique and the differential scanning calorimetry at liquid state, respectively. A thermogravimetric analyzer is deployed for evaluate the high-temperature thermal stability of the composite ternary carbonates. Scanning electron microscopy and Fourier transform infrared spectroscopy techniques are utilized to examine the surface morphologies and chemical structures of the samples. The results indicate that there is a cooperative reinforcement impact on the thermophysical properties of ternary carbonate by utilizing zero-dimensional Al2O3 nanoparticles and two-dimensional graphene nanosheets, with a maximum improvement of 56.7 % for thermal conductivity, and 10.3 % for specific heat, which is apparently larger than adding any single nanoparticle. The composites exhibit superior thermal cycling stability after low-high temperature experiment, and samples can maintain thermal stability until 700 °C in the thermogravimetric analysis.

Hydrogen-Rich Syngas Production in a Ce0.9Zr0.05Y0.05O2−δ/Ag and Molten Carbonates Membrane Reactor

This study proposes a new dense membrane for selectively separating CO2 and O2 at high temperatures and simultaneously producing syngas. The membrane consists of a cermet-type material infiltrated with a ternary carbonate phase. Initially, the co-doped ceria of composition Ce0.9Zr0.05Y0.05O2−δ (CZY) was synthesized by using the conventional solid-state reaction method. Then, the ceramic was mixed with commercial silver powders using a ball milling process and subsequently uniaxially pressed and sintered to form the disk-shaped cermet. The dense membrane was finally formed via the infiltration of molten salts into the porous cermet supports. At high temperatures (700–850 °C), the membranes exhibit CO2/N2 and O2/N2 permselectivity and a high permeation flux under different CO2 concentrations in the feed and sweeping gas flow rates. The observed permeation properties make its use viable for CO2 valorization via the oxy-CO2 reforming of methane, wherein both CO2 and O2 permeated gases were effectively utilized to produce hydrogen-rich syngas (H2 + CO) through a catalytic membrane reactor arrangement at different temperatures ranging from 700 to 850 °C. The effect of the ceramic filler in the cermet is discussed, and continuous permeation testing, up to 115 h, demonstrated the membrane’s superior chemical and thermal stability by confirming the absence of any chemical interaction between the material and the carbonates as well as the absence of significant sintering concerns with the pure silver.

Mechanistic Insights into the Evolution of Graphitic Carbon from Sulfur Containing Polar Aromatic Feedstock.

In the realm of carbon fiber research, a variety of structural configurations is noted, comprising crystalline, noncrystalline, and semicrystalline forms. Recent investigations into this domain have revealed an array of intriguing phases of carbon, among which amorphous graphite is the most notable for its unique mechanical, thermal, and electrical properties that arise from its inherent topological disorders. In this study, we utilized the ReaxFF molecular dynamics (MD) simulations to investigate the carbonization and graphitization processes involved in the production of amorphous graphite from benzothiophene, a sulfur-containing polar aromatic precursor. We developed C/H/S ReaxFF force field parameters to describe the high-temperature chemistry of benzothiophene. Our investigation reveals the reaction mechanisms, providing critical insights into the underlying chemical processes toward the formation of amorphous graphite and the structural characteristics of the end products. The formation of volatile gaseous molecules and their continuous elimination led to the development of noncontinuous layered graphite structures analogous to amorphous graphite consisting of pentagons, hexagons, and heptagons. These findings offer unprecedented insights into the carbonization and graphitization processes of sulfur-containing heavy-end aromatic feedstock. This knowledge lays the groundwork for advancing synthesis methods and developing amorphous graphite materials with specific properties.