Carbon Phase Research Articles

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-nanostructures on diamond, with significant implications for its advanced 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.

A Sequential Leaching Protocol for δ11B and Trace Element Analyses of Multi‐Phase Carbonate Rocks

AbstractBoron geochemistry from biogenic carbonates offer valuable information about ocean pH and CO2 chemistry. However, application to geological carbonate deposits suffers from analytical difficulties in obtaining geochemical signals exclusively from the carbonate phase. Sequential leaching with reagents and acids has the potential to overcome such an issue. There is, however, little systematic investigation about the efficiency of sequential leaching in isolating carbonate‐associated boron from siliciclastic matrix. Here, we developed a sequential leaching protocol and applied it to methane‐derived‐authigenic‐carbonate samples. Using the leachate δ11B signatures, elemental composition, and mineral composition of residues, we show that the sequential leaching is able to improve the separation of boron from different phases. Buffered hydrogen peroxide removes organic matter and also some silicate phases resulting low δ11B values. Leaching with NH4Ac removes adsorbed boron though may also partially leach some carbonate phases. The first few leaching steps with diluted acetic acid dissolve carbonate phases. Depending on the sample type, these may also capture some remaining adsorbed boron from the preceding NH4Ac leaching. Once the adsorbed boron is completely removed, as indicated by the progressively higher δ11B values during the following acid leaching steps, representative carbonate composition can be derived. The accuracy of this protocol is demonstrated with leaching experiments using artificial deep sea coral carbonate and clay mixtures that give the representative carbonate‐associated δ11B within error of the pure coral value. Our results provide insights into characteristic signatures derived from silicates and organic matter that need to be considered in boron isotope analyses of impure marine carbonates.

Effect of boron on phase, nanostructure, and thermal stability of polycarbosilane-derived SiC ceramics

The current study explores the formation, evolution, and thermal stability of polymer-derived SiBC at high temperatures. It focuses on the phase evolution of SiBC ceramics derived from the doping of boron in an allyl-containing polycarbosilane preceramic polymer after 1200 °C to 1600 °C pyrolysis. Different SiBC ceramic monoliths have been obtained. Boron is incorporated into the carbon phase at lower pyrolysis temperatures but into both the carbon phase and the SiC lattice structure at high pyrolysis temperatures. B–C bonds form in SiBC and hinder the growth of graphitic carbon and SiC. Boron improves the densification and thermal stability of the SiBC ceramics. This work provides an improved understanding of boron effects in polymer-derived SiC nanostructures at high temperatures.

Construction of ZrC@SiC shell-core structure in SiBCN aerogel for enhanced thermal stability and thermal insulation

SiBCN aerogels have drawn increased attention as thermal insulation material, but they still suffer from precipitation and phase transition causing the microstructural collapse and performance deterioration under high-temperature environments. Here, ZrC/SiBCN aerogels were prepared using zirconium (IV) butoxide modified polyborosilazane as precursor through solvothermal reaction, frozen casting followed by frozen drying and pyrolysis. Benefiting from its unique hierarchical cellular structure, ZrC/SiBCN aerogel exhibits super-low density (0.042 g/cm3), high specific surface area (287.9 m2/g) as well as low thermal conductivity (24 mW/(m·K)). Shell-core ZrC@SiC nanocrystals are in-situ formed in amorphous SiBCN matrix through step-by-step carbothermal reduction of oxygen-containing phases and free carbon phase during the pyrolysis process, which effectively inhibits the crystallization and growth of SiC crystals, further enhancing the thermal stability under high-temperature environments. It could maintain a high specific surface area (163 m2/g) and low thermal conductivity (29 mW/(m·K)) after thermal treatment at 1800 °C for 2 h. The excellent structural and performance stability of the SiBCN-based aerogels will expand their applications under high-temperature extreme environments.

Structure and Magnetic Properties of Fe<sub>3</sub>O<sub>4</sub>/C Composites Synthesized from Wheat Straw

The porous structure and magnetic properties of nanostructured Fe3O4/C composites based on wheat straw were investigated in this work. The synthesis was carried out by a one- and two-step method using FeCl3 and ZnCl2 as activating agents. X-ray diffraction methods have shown the presence of an additional phase of magnetite Fe3O4 in both synthesized composites, along with the amorphous carbon phase. Magnetic measurements have shown that the composite synthesized in one step has better magnetic properties, in particular, a higher specific saturation magnetisation. However, the samples of the composite synthesized in two steps are characterised by a higher content of micropores and mesopores, which causes an increase in the specific surface area to 884 m2/g compared to 405 m2/g for the samples synthesized in one step. Based on the dependence of the coercive force on the particle diameter in Fe3O4 dispersions, it was found that the average size of the magnetite particles is ~25 nm for both synthesized magnetoresponsive composites.

Control of Thermochemical Transformations of Components of Coal-Based Binders

The possibility of considering coal pitch as a material suitable for research modeling the processes of thermochemical transformations of the plastic mass of coal carbonization and their interaction with the solid carbon phase is analyzed. The possibilities of controlling the properties of coal pitch and blast furnace coke during its production with the help of aprotic acid additives in the presence of a co-catalyst are shown.

Thermal transformations of graphite and anthracite in the presence of lithium carbonate

The method of differential scanning calorimetry was used to study mixtures of graphite and anthracite with lithium carbonate in an argon atmosphere and in air. It was found that in the temperature range of 100–500°C, a stronger mass loss occurs in argon than in air. This phenomenon is caused by the removal of oxygen compounds with carbon. Competing processes take place in the air – the formation of oxygen compounds with carbon, coal and desorption of oxygen-containing substances. A comparison of thermal effects on the curves of DSC and gravimetry for graphite–lithium carbonate systems in argon, in air is carried out. It was found that up to 700°C in the reaction products, the molar ratio of carbon oxides (IV; II) can be estimated at 10 : 1. Endothermic effects of lithium carbonate melting in an argon atmosphere for mixtures of graphite and anthracite with lithium carbonate were observed at 732°C and 727°C, respectively. In air, the peaks of endothermic effects do not correspond to the heat absorption curves in argon. The most probable explanations of the observed effects are given – the presence of phases of carbonate and lithium oxide; the manifestation of the stretched nature of the pre-transition region of lithium carbonate. By the method of powder X-ray diffractometry, it was found that the burnout of the carbon phase at 500°C in graphite, anthracite does not lead to a significant change in the interplane distances in lithium carbonate.

Modulation of Free Carbon Structures in Polysiloxane-Derived Ceramics for Anode Materials in Lithium-Ion Batteries.

Polymer-derived silicon oxycarbide (SiOC) ceramics have garnered significant attention as novel silicon-based anode materials. However, the low conductivity of SiOC ceramics is a limiting factor, reducing both their rate capability and cycling stability. Therefore, controlling the free carbon content and its degree of graphitization within SiOC is crucial for determining battery performance. In this study, we regulated the free carbon content using divinylbenzene (DVB) and controlled the graphitization of free carbon with the transition metal iron (Fe). Through a simple pyrolysis process, we synthesized SiOC ceramic materials (CF) and investigated the impact of Fe-induced changes in the carbon phase and the amorphous SiOC phase on the comprehensive electrochemical performance. The results demonstrated that increasing the DVB content in the SiOC precursor enhanced the free carbon content, while the addition of Fe promoted the graphitization of free carbon and induced the formation of carbon nanotubes (CNTs). The electrochemical performance results showed that the CF electrode material exhibited a high reversible capacity of approximately 1154.05 mAh g-1 at a low current density of 100 mA g-1 and maintained good rate capability and cycling stability after 1000 cycles at a high current density of 2000 mA g-1.

Solar-driven purification: Removing pharmaceutical contaminants from water using carbon-doped NASICON photocatalyst

Pharmaceutical contaminants in water pose significant risks to aquatic ecosystems and human health. This work synthesized a novel NASICON@C composite (sodium super ionic conductor embedded with carbon) as a visible-light-driven photocatalyst for eliminating paracetamol from water. Characterization confirmed a well-dispersed composite with hexagonal morphology, surface porosity, and strong visible light absorption. The carbon phase enabled visible light harvesting while the NASICON facilitated charge transfer and redox reactions. Photocatalytic testing showed dramatic paracetamol degradation within 30 min under visible irradiation using NASICON@C. 99.7 % of the initial 100 mg L−1 paracetamol was eliminated in neutral pH conditions. The ion-conducting NASICON framework promoted efficient charge carrier separation and transfer to enable the oxidation reactions. The NASICON@C catalyst displayed excellent stability over five reuse cycles. The synergistic integration of carbon and NASICON phases in this composite photocatalyst makes it a promising and sustainable platform for visible light-driven pharmaceutical contaminant removal from water sources.

Phase evolution and microstructure changes induced by accelerated carbonation in natural hydraulic lime paste with GGBFS addition

Carbonation is a primary factor driving the continuous improvement of the long-term performance of natural hydraulic lime (NHL). This research systematically examines the impact of accelerated carbonation (3 % CO2) on the carbonation depth, phase composition, microstructure, and compressive strength of hardened natural hydraulic lime (NHL) pastes mixed with different amounts of ground granulated blast furnace slag (GGBFS), termed as S-NHL. The findings show that the hydration reaction products of GGBFS and Ca(OH)2 (CH), such as C3AH10, C4AĈH11, and C-S-H, densify the microstructure of S-NHL, resulting in a decrease in carbonation depth with increasing GGBFS content. Accelerated carbonation (AC) promotes the rapid transformation of a significant quantity of CH into calcite in S-NHL, with the carbonation of CH occurring more readily than the carbonation of hydration reaction products. Throughout the AC process, NHL contains only calcite-type calcium carbonate. In contrast, after 28 days of AC, the carbonation of hydration reaction products such as C3AH10 and C-S-H in S-NHL produces a minor amount of aragonite and vaterite. AC continuously reduces the total pore volume and porosity of S-NHL, but the average pore diameter and most probable pore diameter initially decrease and then slightly increase. AC significantly reduces the large pores in S-NHL, ultimately resulting in pores predominantly composed of capillary pores (50–1000 nm). AC facilitates the development of compressive strength in S-NHL paste, with the increase in compressive strength being positively correlated with its CH content.

Physical properties of industrially produced carbon nanotube yarns for use in structural nanocomposites

Industrially-produced carbon nanotube (CNT) networks are a promising base for high-performance, continuous CNT nanocomposites, motivating widespread use in research and application development. Floating catalyst chemical vapor deposition (FCCVD) is a scalable, widely-adopted approach for synthesis of CNT networks; however, FCCVD can yield networks with organic impurities which complicate their characterization and processing. Herein, we analyze two varieties of FCCVD-synthesized commercial CNT yarn to explore the effects of densification and purification as they relate to forming infiltrated polymer composites. First, the fluid permeabilities and porosities of neat roving and chemically-stretched CNT yarns (CSYs) are estimated and compared to gas adsorption studies, which suggest high-tenacity CSYs are largely impermeable, leading to dry-core composites when polymer infiltration is attempted. Next, the presence and effects of oxygen-rich amorphous carbon impurities in the CSYs are identified and found to exist at the scale of CNT bundles, wherein the amorphous carbon behaves like a hygroscopic polymer matrix in a composite. Removal of the amorphous carbon phase in a 130%-increase in specific surface area, as quantified by BET analysis, and a statistically significant reduction in tensile properties. We discuss challenges in estimating yarn alignment and crystallinity resulting from these factors, and place our results in context of past studies analyzing intrinsic organic coatings in FCCVD-synthesized CNT networks.