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Aluminum electrolysis spent cathode carbon (SCC), as typical solid hazardous waste, poses significant environmental risks. Harmless treatment of SCC and recycling of its carbon component are important research areas. In this study, SCC was subjected to microwave hydrothermal acid leaching to remove harmful components, followed by the production of high-quality graphite via iron-catalyzed graphitization. The effects of reaction temperature, heating time, and catalyst loading on the graphitization conversion of SCC were investigated. The catalytic graphitization process of SCC was optimized using the response surface method. The results show that when the reaction temperature is 1520 °C, the heating time is 85.24 min, and the catalyst loading is 46.15 wt%, the graphitization degree of the sample is 97.61 %. The samples prepared under the optimal conditions were characterized using XRD, Raman, SEM, and TEM. The results reveal that the catalytic graphitization process significantly influences the conversion of microcrystalline structures in SCC into graphite structures. The iron-catalyzed transformation of microcrystalline carbon was analyzed to elucidate the graphitization transformation mechanism. This study offers an effective pathway for the high-value utilization of SCC. It also serves as a technical reference for the catalytic graphitization conversion of carbon materials. [ABSTRACT FROM AUTHOR]

Sol-gel electrospinning process was used to prepare electrospun carbon nanofibers (ECNFs) from polyacrylonitrile and graphite nanoplatelets. The nanofibers of as-electrospun carbon were calcinated in argon from room temperature to 500 °C for 1h. Scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffractometry (XRD) were used to characterize the synthesized ECNFs. The smooth ECNFs with a diameter of 129 ± 43 nm comprised conical platelets of 30–200 µm length. The plane-layered nanofibers contained crystallites along the long fiber axis and were mainly parallel. [ABSTRACT FROM AUTHOR]

[Display omitted] • The sulfonation time of PP fibers is reduced by 50 % due to the acid soaking process applied prior to sulfonation. • The soak treatment was carried out at temperature about dozens of degree lower than that of sulfonation process. • The pretreatment of the precursors enhanced the mechanical properties of PP-based carbon fibers from 286.4 MPa to 399.6 MPa. Polyolefin fibers have received wide attention as the precursor for low-cost carbon fiber, and cross-linking of linear polyolefin by strong acid has been proven to be an effective way to stabilize the precursor fiber prior to carbonization. However, the conventional temperature used in sulfonation process is too high and could result in severe decomposition of the linear chain of the polymer, which further deteriorated the mechanical properties of the as-prepared carbon fiber. Thus, reducing the duration of sulfonation process operated at high temperature may alleviate the degradation behavior, conferring the polyolefin-based carbon fibers with better performance. In this paper, polypropylene (PP) fibers were soaked in sulfuric acid at 50 °C–90 °C, before the conventional preparation protocol of PP-based carbon fiber. The structural evolution from PP to carbon fiber were characterized by Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy. The mechanical and conductive properties of carbonized fibers where further measured. The results showed that the soak in sulfuric acid resulted in swelling of PP fibers in diameter direction, as well as reducing the crystallinity of the fibers, both of which were physical transformation, and could be easily controlled by soak temperature. The subsequent sulfonation at conventional temperature was fastened for the soaked PP fibers, and the duration of sufficient sulfonation were almost reduced by half. The obtained carbon fibers exhibited better thermal conductivity and mechanical properties, which were enhanced by 25 % and 40 %, respectively, compared with that without soak pretreatment. [ABSTRACT FROM AUTHOR]

Soot from the thermochemical conversion of solid and liquid fuels can be infused with metallic heteroatoms originating from the fuel – these heteroatoms alter the nanostructure and the reactivity of the soot. Here, we investigate the spatial distribution of metallic heteroatoms in soot generated by biomass gasification, using aberration-corrected Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy (STEM-EELS). The technique allowed for the mapping of heteroatom distribution in soot at the nanoscale, and thereby for the direct correlation of heteroatom concentration with the graphitic nanostructure. Spherical soot particles were coated with a thin layer of silicon, possibly in the form of quartz that may be linked to minor distortions of the nanostructure of the graphitic shell of the particles. Further results on non-spherical soot and inorganic-carbon fused aggregates suggest that the chemistry of formation was affected by the presence of gaseous ash-forming elements, especially calcium, with carbon-oxygen functional groups forming as intermediates in the graphite-inorganic reaction; i.e., prior to the formation of the thermodynamically stable carbonate bonds. The analytical approach demonstrated here can potentially help select fuel additives or aid in the design of fuel blends that minimize the formation of similar, hybrid carbon nanoparticles in combustion or gasification systems. Image 1 • Metal infused soot particles were analyzed with aberration-corrected STEM-EELS. • Spherical soot particles were coated with silicon and oxygen, possibly quartz. • Calcium affect the graphitic structure of non-spherical soot. • Carbon-oxygen functional groups could be detected in non-spherical soot. • STEM-EELS can help understand particle formation mechanisms. [ABSTRACT FROM AUTHOR]

Effects of additions of 0.00064, 0.001 and 0.0042 wt.% Bi on the graphite structure in the section thicknesses of 3, 12, 25, 38, 50, 75 and 100 mm of spheroidal graphite cast iron castings containing 2.11 wt.% Si and rare earth (RE) elements (Ce + La + Nd + Pr + Sm + Gd) in the range from 0.00297 to 0.00337 wt.% were analyzed in this paper. Addition of Bi was not necessary for obtaining high nodule count and nodularity higher than 80% in section thicknesses of 3, 12 and 25 mm. RE elements showed a beneficial effect on the nodule count and nodularity in these sections. Nodularity was below 80% in section thicknesses of 38, 50, 75 and 100 mm when Bi was not added. Detrimental effect of RE elements on graphite morphology in these sections was neutralized by adequate addition of Bi. Addition of 0.001 wt.% Bi (ratio of RE/Bi = 3.27) was enough to achieve nodularity above 80% in the section thickness of 38 mm. Nodularity was increased above 80% in section thicknesses of 50, 75 and 100 mm by addition of 0.0042 wt.% Bi (ratio of RE/Bi = 0.78). At the same time, Bi significantly increased the nodule count. Nodularity above 80% and the high nodule count in the section thicknesses of 75 and 100 mm were also achieved by using an external metallic chill in the mold. In this case, addition of Bi was not required.

Understanding the nucleation and growth process of carbon nanotubes (CNTs) is important for guiding their efficient and controllable synthesis in industry. However, the intrinsic mechanism that controls the formation of carbon nanotubes is still controversial. Here, using in‐situ transmission electron microscopy (TEM), we demonstrate the dynamic catalytic growth of multilayered graphite crystallites and single‐walled carbon nanotubes (SWCNTs) from the Co2C catalyst nanoparticles (NPs) at the atomic resolution. The dissociative carbon atoms arrive at the nucleation sites on the surface of small and large NPs by the surface and bulk diffusion, respectively. These two different diffusion modes are found to be the essential prerequisite for growing single‐walled carbon nanotubes (SWCNTs) or multilayered graphite crystallites. The small NPs utilize crystal self‐rotation to expose the (111) plane for efficiently capturing carbon atoms, while the large NPs use self‐reshaping on (111) facets to provide atomic steps as active nucleation sites. Density functional theory (DFT) calculations indicate that the observations are in good agreement with the growth mechanism of graphite structures involving the preferential selectivity of crystal facets. Our results may open up the possibility of adjusting the size and crystal orientation of cobalt‐based catalyst particles to efficiently synthesize the SWCNTs with high quality. [ABSTRACT FROM AUTHOR]

A kind of silicon-and-boron-modified phenolic–formaldehyde resin (SBPF) with excellent thermal stability was fabricated via a simple two-step method and used for the matrix of ablation materials. The structure and thermal stability of the modified phenolic–formaldehyde resins (PFs) were characterised. The results showed that boron and silicon elements have been incorporated into SBPF in the form of a chemical bond. Meanwhile, the cured products showed an increase in graphite structure and a decrease in disordered structure due to the incorporation of boron and silicon. Compared with the ordinary phenolic resin, the initial thermal degradation temperature and charring yield at 800°C of SBPF increased by 73°C and 15 wt%, respectively. Further, the modified PFs, nano-Al(2)O(3) powders, glass powders and vitreous silica fibres were used to obtain a novel ceramizable phenolic moulding composite. The morphology, chemical composition and ablative characteristics of the composites were explored. The results showed that a compact and homogeneous SiO(2)–Al(2)O(3) layer formed on the ablated surface and protected the carbonised matrix and fibres from further oxidation. Compared with the ordinary PF composites, the SBPF composites showed a highly decreased linear/mass ablation rates, indicating the synergistic effect of boron and silicon modification on the enhanced ablation property.

Effects of additions of 0.00064, 0.001 and 0.0042 wt.% Bi on the graphite structure in the section thicknesses of 3, 12, 25, 38, 50, 75 and 100 mm of spheroidal graphite cast iron castings containing 2.11 wt.% Si and rare earth (RE) elements (Ce + La + Nd + Pr + Sm + Gd) in the range from 0.00297 to 0.00337 wt.% were analyzed in this paper. Addition of Bi was not necessary for obtaining high nodule count and nodularity higher than 80% in section thicknesses of 3, 12 and 25 mm. RE elements showed a beneficial effect on the nodule count and nodularity in these sections. Nodularity was below 80% in section thicknesses of 38, 50, 75 and 100 mm when Bi was not added. Detrimental effect of RE elements on graphite morphology in these sections was neutralized by adequate addition of Bi. Addition of 0.001 wt.% Bi (ratio of RE/Bi = 3.27) was enough to achieve nodularity above 80% in the section thickness of 38 mm. Nodularity was increased above 80% in section thicknesses of 50, 75 and 100 mm by addition of 0.0042 wt.% Bi (ratio of RE/Bi = 0.78). At the same time, Bi significantly increased the nodule count. Nodularity above 80% and the high nodule count in the section thicknesses of 75 and 100 mm were also achieved by using an external metallic chill in the mold. In this case, addition of Bi was not required. [ABSTRACT FROM AUTHOR]

The effect of minerals on the high-temperature graphitization process of coke was thoroughly investigated using by X-ray diffraction (XRD), Raman spectroscopy (Raman), scanning electron microscope (SEM), physical adsorption instrument, etc. The structure-activity relationship between the microstructure of coke-based graphite and lithium storage performances was identified. The findings demonstrate that the microstructure of coke-based graphite is related to the mineral content and the final graphitization temperature affects the Si or Fe catalytic graphitization of coke. The appropriate amount of minerals as the catalyst can reduce the interlayer spacing, improve the graphitization degree and increase the crystallite size of the coke graphitization sample. The catalytic graphitization of coke involves the carbide transition, which is further confirmed by XRD and SEM-EDS analysis. By proper adding the mineral to the coke during the graphitization process, it is clear that the electrochemical performances of the synthetic graphite as anode for lithium-ion batteries can be improved obviously. Coke-based graphite DCG-20Si-2800 and DCG-30Fe-2800 as anode material show good comprehensive electrochemical performances. And the reversible specific capacities of both at 0.1 C are as high as 353.9 mAh/g and 361.9 mAh/g, respectively, which are quite close to the theoretical capacity of graphite (1 C = 372 mAh/g). Thus, the study successfully reveals the law of mineral catalysis in the graphitization process of coke and demonstrates the feasibility of coke-based graphite products as anode material. It can be expected that coke can be useful sources of artificial graphite if the graphitization process is adequately improved. [Display omitted] • The minerals in coke play a catalytic role in high-temperature graphitization. • Carbide transformation was demonstrated in the catalytic graphitization of coke. • Coke-based graphite show high crystallinity and excellent lithium storage properties. [ABSTRACT FROM AUTHOR]

Different matrix and graphite morphologies were generated by a special heat treatment in three chemically different series of flake graphite cast iron samples. As cast, furnace cooled and air cooled samples were investigated. The length of graphite particles and the pearlite volume of samples were determined by metallographic examination and these parameters were compared with the nondestructively measured magnetic parameters. Magnetic measurements were performed by the method of Magnetic Adaptive Testing, which is based on systematic measurement and evaluation of minor magnetic hysteresis loops. It was shown that linear correlation existed between the magnetic quantities and the graphite length, and also between the magnetic quantities and the relative pearlite content in the investigated cast iron. A numerical expression was also determined between magnetic descriptors and relative pearlite content, which does not depend on the detailed experimental conditions. [ABSTRACT FROM AUTHOR]

Electron shuttles (ES) can mediate long-distance electron transfer between extracellular respiratory bacteria (ERB) and the surroundings. However, the effects of graphite structure in ES on the extracellular electron transfer (EET) process remain ambiguous. This work investigated the function of graphite structure in the process of nitrobenzene (NB) degradation by Geobacter sulfurreducens PCA, in which highly aromatic carbon nanotubes (CNTs) was studied as a typical ES. The results showed that the addition of 1.5 g L−1 of CNTs improved the NB biodegradation up to 81.2%, plus 18.8% NB loss due to the adsorption property of CNTs, achieving complete removal of 200 μM NB within 9 h. The amendment of CNTs greatly increased the EET rate, indicating that graphite structure exhibited excellent electron shuttle performance. Furthermore, Raman spectrum proved that CNTs obtained better graphite structure after 90 h of cultivation with strain PCA, resulting in higher electrochemical performance. Also, CNTs was perceived as the "Contaminant Reservoir", which alleviated the toxic effect of NB and shortened the distance of EET process. Overall, this work focused on the effects of material graphite structure on the EET process, which enriched the understanding of the interaction between CNTs and ERB, and these results might promote their application in the in-situ bioremediation of nitroaromatic-polluted environment. [Display omitted] • Carbon nanotubes (CNTs) coupled with Geobacter for fast nitrobenzene (NB) reduction. • CNTs with graphite structure facilitated extracellular electron transfer process. • CNTs achieved the recovery of sp2 network after cultivation with Geobacter. • CNTs with higher graphitization extent showed better electrochemical performance. • CNTs acted as "Contaminant Reservoir" and promoted NB biodegradation. [ABSTRACT FROM AUTHOR]

Abstract: To investigate the effects of introducing the iron compound on the carbonization behavior polyacrylonitile (PAN)-based electrospun nanofibers were carbonized with or without iron(III) acetylacetonate (AAI) over the temperature range of 900–1500°C in nitrogen atmosphere. The morphological characteristics of the carbon nanofibers were investigated using X-ray diffractometer (XRD), Raman spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The electrical conductivity of the carbon nanofiber web was measured by four-point probe method. The iron catalyst had a profound effect on the crystal structure of the carbonized nanofiber. In the presence of AAI the nanofibers carbonized at 1300°C developed graphite structure, which could be obtained at the temperature higher than 2000°C in the absence of the catalyst. The in-plane size of the graphite crystals (L a) was measured to be about 6.5nm by Raman spectroscopy and the (002) spacing by XRD was 0.341nm. [Copyright &y& Elsevier]

Functionalization of graphite is crucial for efficient and effective exfoliation to graphene. When negative charges are fixed to the edges of natural graphite, the resulting anionic graphite shows negative charging in a polar solvent. This enhanced negative charging is assumed to contribute the exfoliation of graphite during liquid-phase exfoliation (LPE). In this study, we prepared large anionic graphite flakes (~10 μm) by salt-assisted ball milling, as well as natural graphite flakes of the same size for comparison. During the LPE process, centrifugation speed and solvent type have dominant effects on graphene concentration and quality (e.g., size and thickness), so we investigated these factors for anionic graphite flakes in detail. The anionic graphite showed higher exfoliation efficiency in every type of solvent (isopropanol, methyl ethyl ketone, acetone, and water-based cosolvent) compared with the natural graphite. Monolayer graphene, with an average size of 80–200 nm, was obtained with relatively high yield (>10%) at only 3 min of sonication. The small size of graphene was due to edge fragmentation during the LPE process. The recyclability of the sediment and the characterization of the exfoliated powders for anionic graphene were also investigated. [ABSTRACT FROM AUTHOR]