Influence of bond defects on coiling of graphite

Milev, Adriyan; Tran, Ngoc Quang; Kannangara, Kamali; Wilson, Michael

doi:10.1016/j.stam.2006.11.010

Cited by 22 publications

(12 citation statements)

References 18 publications

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“…The Raman profiles exhibited in Figure 3d agree well with the XPS results where the intensity of the peak associated with defects at around 1350 cm −1 is stronger in DHPCs, giving rise to an increased I D /I G ratio, a widely used indicator to describe the relatively defective content in carbon materials. 42,43 Then, C K-edge NEXAFS was further used to investigate the structural feature (Figure 3e). Compared to NHPCs, DHPCs give a weak shoulder feature around 284.5 eV associated with edge characters (Figure 3e,f), indicative of the increased degree of graphitization in localized regions due to annealing at higher temperatures.…”

Section: Resultsmentioning

confidence: 99%

Intrinsic Defect-Rich Hierarchically Porous Carbon Architectures Enabling Enhanced Capture and Catalytic Conversion of Polysulfides

Guan

et al. 2020

ACS Nano

103

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Despite their promising potential, the real performance of lithium-sulfur batteries is still heavily impeded by the notorious shuttle behavior and sluggish conversion of polysulfides. Complex structures with multiple components have been widely employed to address these issues by virtue of their strong polarity and abundant surface catalytic sites. Nevertheless, the tedious constructing procedures and high cost of these materials make the exploration of alternative high-performance sulfur hosts increasingly important. Herein, we report an intrinsic defect-rich hierarchically porous carbon architecture with strong affinity and high conversion activity toward polysulfides even at high sulfur loading. Such an architecture can be prepared using a widely available nitrogen-containing precursor through a simple yet effective in situ templating strategy and subsequent nitrogen removal procedure. The hierarchical structure secures a high sulfur loading, while the intrinsic defects strongly anchor the active species and boost their chemical conversion because of the strong polarity and accelerated electron transfer at the defective sites. As a result, the lithium-sulfur batteries with this carbon material as the sulfur host deliver a high specific capacity of 1182 mAh g–1 at 0.5 C, excellent cycling stability with a capacity retention of 70% after 500 cycles, and outstanding rate capability, one of the best results among pure carbon hosts. The strategy suggested here may rekindle interest in exploring the potential of pure carbon materials for lithium-sulfur batteries as well as other energy storage devices.

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Section: Resultsmentioning

confidence: 99%

Intrinsic Defect-Rich Hierarchically Porous Carbon Architectures Enabling Enhanced Capture and Catalytic Conversion of Polysulfides

Guan

et al. 2020

ACS Nano

103

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“…Transmission Electron Microscopy examination (not shown) of ball-milled graphite reveals morphological changes similar to those we already reported in the literature. 24,27 During milling, the shear and impact forces continuously bend, fracture and displace the graphite sheets relative to each other and the ABAB. .…”

Section: Evolution Of Disorder During Millingmentioning

confidence: 99%

“…Elsewhere some of us demonstrated that during annealing in argon the system is driven to minimize the increased free energy by relief of the bond distortion and conjugation of the double in-plane bonds. 27,47 Besides, the stress accumulated during milling is minimised, at least in part, and by folding, corrugation and sometimes coiling of the graphene sheets. 24,27,47,48 To investigate the temperature stability of the magnetic susceptibility, sample G30 was heated to 1000 1C in argon (Ar) for 1 hour and after cooling down under inert gas conditions the susceptibility of the material was measured in the temperature interval 2-200 K (Fig.…”

Section: Modifications Of the Graphite Andmentioning

confidence: 99%

Defect induced electronic states and magnetism in ball-milled graphite

Milev

Dissanayake

Kannangara

et al. 2013

Phys. Chem. Chem. Phys.

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The electronic structure and magnetism of nanocrystalline graphite prepared by ball milling of graphite in an inert atmosphere have been investigated using valence band spectroscopy (VB), core level near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and magnetic measurements as a function of the milling time. The NEXAFS spectroscopy of graphite milled for 30 hours shows simultaneous evolution of new states at ~284.0 eV and at ~290.5 eV superimposed upon the characteristic transitions at 285.4 eV and 291.6 eV, respectively. The modulation of the density of states is explained by evolution of discontinuities within the sheets and along the fracture lines in the milled graphite. The magnetic measurements in the temperature interval 2-300-2 K at constant magnetic field strength show a correlation between magnetic properties and evolution of the new electronic states. With the reduction of the crystallite sizes of the graphite fragments, the milled material progressively changes its magnetic properties from diamagnetic to paramagnetic with contributions from both Pauli and Curie paramagnetism due to the evolution of new states at ~284 and ~290.5 eV, respectively. These results indicate that the magnetic behaviour of ball-milled graphite can be manipulated by changing the milling conditions.

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“…However, if X-ray diffraction gives accurate crystallographic information, spectroscopic methods give quantitative information on carbon content and the ratio of sp 2 /sp 3 bonds [1,2]. It is shown that in-plane sp 2 bonds are strained and distorted after ball milling because sp 3 bonds are introduced [3]. Much of what we know about the microstructures of these materials is obtained by use of picoscope [4].…”

Section: Introductionmentioning

confidence: 99%

Spatial 3d Direct Visualization of Atoms, Molecules and Chemical Bonds

Kucherov¹,

Rud²,

Gubanov³

et al. 2020

AJAC

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The paper presents the further development of direct visualization of individual atoms, molecules with chemical bonds by spatial 3d electron cloud densitometry. Direct visualization of small objects studied by chemistry is made possible by the discovery of the plane wave amplitude deformation in accordance with the electron cloud density. Accordance with this affect, an atom begins to illuminate, depicting its own form! A quantum mechanical theory of the effect is given. As a result, it was possible to trace a chemical reaction with a change in the chemical bonds, geometry molecules, and distances between the atoms. The spatial 3d picoscope is used to show the structure of crystalline graphite formed by the sp 2 chemical bonds of carbon atoms, and a system of weak π-bonds that connects the layers of graphite. This device confirmed the flat structure of single-layer graphene and allowed to detect a two-layer hexagonal diamond system that was previously un known. This material is proposed to designate gubanite. A scan be seen from the spatial 3d snapshot, as the graphene layers converge, the upper graphene π-electron clouds connect to the lower graphene π-electron clouds to form a two-layer diamond gubanite, the spatial 3d model of which is shown. It should lead to the appearance of visual chemistry.

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Influence of bond defects on coiling of graphite

Cited by 22 publications

References 18 publications

Intrinsic Defect-Rich Hierarchically Porous Carbon Architectures Enabling Enhanced Capture and Catalytic Conversion of Polysulfides

Intrinsic Defect-Rich Hierarchically Porous Carbon Architectures Enabling Enhanced Capture and Catalytic Conversion of Polysulfides

Defect induced electronic states and magnetism in ball-milled graphite

Spatial 3d Direct Visualization of Atoms, Molecules and Chemical Bonds

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