A combination of large void volume and rich microporous structure enables expanded graphite (EG) to possess excellent adsorption properties. Furthermore, it is discovered to be hydrophilic with the ...capability of adsorbing NO.sub.x. The ball milling method was applied in preparation of the MnO.sub.x/TiO.sub.2 modified by expanded graphite catalysts with the aim to improve SCR activity and resistance to H.sub.2O and SO.sub.2. An optimal SCR performance was obtained over the catalysts with 5 wt% EG doping. Subsequently, an investigation was conducted by XPS, NH.sub.3-TPD, H.sub.2-TPR into the understanding of the SCR catalytic performance of MnO.sub.x/TiO.sub.2 at low-temperature. As revealed by the investigation results, the catalyst modified by EG had more Mn.sup.4+ species and could absorb more oxygen, which allowed it to present more surface acid sites that could boost SCR activity. In addition, it was discovered that the introduction of EG could facilitate the improvement on the resistance to H.sub.2O and SO.sub.2.
The isothermal crystallization properties of polypropylene/graphite nanosheet (PP/GN) nanocomposites under supercritical Nsub.2 were systematically studied by a self-made in situ high-pressure ...microscope system. The results showed that the GN caused irregular lamellar crystals to form within the spherulites due to its effect on heterogeneous nucleation. It was found that the grain growth rate exhibits a decreasing and then increasing trend with the enhancement of Nsub.2 pressure. Using the secondary nucleation model, the secondary nucleation rate for spherulites of PP/GN nanocomposites was investigated from an energy perspective. The increase in free energy introduced by the desorbed Nsub.2 is the essential reason for the increase in the secondary nucleation rate. The results from the secondary nucleation model were consistent with those acquired through isothermal crystallization experiments, suggesting that the model can accurately predict the grain growth rate of PP/GN nanocomposites under supercritical Nsub.2 conditions. Furthermore, these nanocomposites demonstrated good foam behavior under supercritical Nsub.2.
The experimental results on etching of diamond crystals with octahedral and cubooctahedral habits at a temperature of 1000°Ð¡ in wet argon are presented. It is found that at a low partial pressure, ...Ð.sub.2Ð can act as an initiator (catalyst) of the surface graphitization of diamonds at the Ð -Т-parameters of thermodynamic stability of graphite. The limiting stage of the diamond etching process in the presence of graphite on diamonds is the stage of graphite coating oxidation. Since the outer graphite coating is oxidized, there is no dependence of the etching (oxidation) rate on the morphology of diamond crystals.
Graphite, commonly including artificial graphite and natural graphite (NG), possesses a relatively high theoretical capacity of 372 mA h g–1 and appropriate lithiation/de‐lithiation potential, and ...has been extensively used as the anode of lithium‐ion batteries (LIBs). With the requirements of reducing CO2 emission to achieve carbon neutral, the market share of NG anode will continue to grow due to its excellent processability and low production energy consumption. NG, which is abundant in China, can be divided into flake graphite (FG) and microcrystalline graphite (MG). In the past 30 years, many researchers have focused on developing modified NG and its derivatives with superior electrochemical performance, promoting their wide applications in LIBs. Here, a comprehensive overview of the origin, roles, and research progress of NG‐based materials in ongoing LIBs is provided, including their structure, properties, electrochemical performance, modification methods, derivatives, composites, and applications, especially the strategies to improve their high‐rate and low‐temperature charging performance. Prospects regarding the development orientation as well as future applications of NG‐based materials are also considered, which will provide significant guidance for the current and future research of high‐energy‐density LIBs.
A comprehensive overview of natural graphite‐based materials in ongoing lithium‐ion batteries is presented, covering fundamental mechanisms, detailed applications, and an outlook of natural graphite‐based materials, from not only the aspects of structure and properties, modifications, derivatives, and composites, but also perspectives in terms of natural graphite in hybrid lithium‐ion/lithium‐metal cells and all‐solid‐state lithium batteries.
Most analysis of graphite morphology in cast iron-carbon alloys is performed on samples cooled to room temperature. This raises the concern that the crystallization of graphite is obscured by ...subsequent recrystallization and growth in solid state. To bring clarity to this issue, the authors used Field Emission Gun Scanning Electron Microscopy on deep-etched interrupted solidification (quenched) specimens to reveal the morphology of graphite growing in contact with the liquid at the very beginning of solidification.
To understand the complexity of graphite crystallization in iron alloys, the analysis included evidence from the crystallization of materials with analogous hexagonal structure, such as of snowflakes and metamorphic graphite, and from the crystallization of diamond cubic structure silicon crystals in aluminum-based alloys. Information from research discussing graphite produced through gas-solid (chemical vapor deposition) and solid-solid (graphite in steel) transformations was also exploited.
The large variety of graphite solidification morphologies described in this and earlier papers derives from the complexities of its faceted growth during crystallization, a diffusion-limited crystal growth process, in the presence of anisotropic surface energy and anisotropic attachment kinetics. It was confirmed that the basic building blocks of the graphite aggregates are hexagonal faceted graphite platelets generated through the growth of graphene layers. As solidification advances, the platelets thicken through layer growth through two-dimensional or screw dislocation nucleation. Depending on bulk composition, local supersaturation and undercooling, the platelets aggregate through a variety of mechanisms including tiled-roof and foliated crystals and dendrites, curved-circumferential, cone-helix, helical (macro-spiral), and polyhedral pyramidal (or conical) sectors growth. The final graphite shape of graphite spheroids is affected by the crystallography of the nucleus, as it affects the initial growth of the graphite platelets.
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Recently, the Josephson diode effect (JDE), in which the superconducting critical current magnitudes differ when the currents flow in opposite directions, has attracted great interest. In particular, ...it was demonstrated that gate-defined Josephson junctions based on magic-angle twisted bilayer graphene showed a strong nonreciprocal effect when the weak-link region is gated to a correlated insulating state at half filling (two holes per moiré cell). However, the mechanism behind such a phenomenon is not yet understood. In this Letter, we show that the interaction-driven valley polarization, together with the trigonal warping of the Fermi surface, induce the JDE. The valley polarization, which lifts the degeneracy of the states in the two valleys, induces a relative phase difference between the first and the second harmonics of the supercurrent and results in the JDE. We further show that the nontrivial current phase relation, which is responsible for the JDE, also generates the asymmetric Shapiro steps.
Carbon materials particularly in the form of sparkling diamonds have held mankind spellbound for centuries, and in its other forms, like coal and coke continue to serve mankind as a fuel material, ...like carbon black, carbon fibers, carbon nanofibers and carbon nanotubes meet requirements of reinforcing filler in several applications. All these various forms of carbon are possible because of the element's unique hybridization ability. Graphene (a single two-dimensional layer of carbon atoms bonded together in the hexagonal graphite lattice), the basic building block of graphite, is at the epicenter of present-day materials research because of its high values of Young's modulus, fracture strength, thermal conductivity, specific surface area and fascinating transport phenomena leading to its use in multifarious applications like energy storage materials, liquid crystal devices, mechanical resonators and polymer composites. In this review, we focus on graphite and describe its various modifications for use as modified fillers in polymer matrices for creating polymer–carbon nanocomposites.
The potentiality of the βsub.12 borophene (βsub.12) and pristine graphene (GN) nanosheets to adsorb tetrahalomethanes (CXsub.4; X = F, Cl, and Br) were investigated using density functional theory ...(DFT) methods. To provide a thorough understanding of the adsorption process, tetrel (XC-Xsub.3∙∙∙βsub.12/GN)- and halogen (Xsub.3C-X∙∙∙βsub.12/GN)-oriented configurations were characterized at various adsorption sites. According to the energetic manifestations, the adsorption process of the CXsub.4∙∙∙βsub.12/GN complexes within the tetrel-oriented configuration led to more desirable negative adsorption energy (Esub.ads) values than that within the halogen-oriented analogs. Numerically, Esub.ads values of the CBrsub.4∙∙∙Br1@βsub.12 and T@GN complexes within tetrel-/halogen-oriented configurations were −12.33/−8.91 and −10.03/−6.00 kcal/mol, respectively. Frontier molecular orbital (FMO) results exhibited changes in the Esub.HOMO, Esub.LUMO, and Esub.gap values of the pure βsub.12 and GN nanosheets following the adsorption of CXsub.4 molecules. Bader charge transfer findings outlined the electron-donating property for the CXsub.4 molecules after adsorbing on the βsub.12 and GN nanosheets within the two modeled configurations, except the adsorbed CBrsub.4 molecule on the GN sheet within the tetrel-oriented configuration. Following the adsorption process, new bands and peaks were observed in the band structure and density of state (DOS) plots, respectively, with a larger number in the case of the tetrel-oriented configuration than in the halogen-oriented one. According to the solvent effect affirmations, adsorption energies of the CXsub.4∙∙∙βsub.12/GN complexes increased in the presence of a water medium. The results of this study will serve as a focal point for experimentalists to better comprehend the adsorption behavior of βsub.12 and GN nanosheets toward small toxic molecules.
