Ball-milled Graphite Research Articles

Wrinkled reduced graphene oxide nanosheets for highly sensitive and easy recoverable NH3 gas detector

Highly wrinkled reduced graphene oxide nanosheets were prepared by chemical exfoliation of ball-milled graphite powder. This material showed high sensitivity and simple recovery ability for NH3 gas detection.

<I>In Situ</I> Synthesis and Cell Performance of a Si/C Core–Shell/Ball-Milled Graphite Composite for Lithium Ion Batteries

A high-capacity silicon-carbon core-shell (Si/C) supported by ball-milled graphite (BMG) was synthesized in situ using a hydrosilylation reaction and tested as an anode material for lithium ion batteries (LIBs) in the investigation of the effects of dual buffer layers of carbon shell and BMG. The Si/C/BMG sample effectively absorbed high volumetric expansion/contraction generated during charge/discharge process due to the assistance of dual elastic buffers of carbon shell and BMG. As a result, after 50 charge/discharge cycles, the Si/C/BMG electrodes still had a very high capacity of 1615 mAh/g, whereas raw Si, Si/C, and a mechanical mixture of Si/C and BMG were less than 500 mAh/g. The results of various electrochemical characterization techniques revealed that the dual buffer layers were favorable in decreasing electron and ion transfer resistance. It was also shown from ex situ TEM results that the carbon layers behaved as anti-amorphization layers decreasing the amorphization rate of crystalline Si during the alloying/dealloying of Li with Si.

Edge‐Selectively Sulfurized Graphene Nanoplatelets as Efficient Metal‐Free Electrocatalysts for Oxygen Reduction Reaction: The Electron Spin Effect

To replace precious platinum (Pt)-based electrocatalysts for cathodic oxygen reduction reaction (ORR), edge-selectively sulfurized graphene nanoplatelets (SGnP) are synthesized as efficient metal-free electrocatalysts simply by ball-milling pristine graphite in the presence of sulfur (S8 ). The resultant SGnPs exhibit remarkable electrocatalytic activity toward ORR with better tolerance to methanol crossover/CO poisoning effects and longer-term stability than those of pristine graphite and commercial Pt/C electrocatalysts. Edge-Selectively Sulfurized Graphene Nanoplatelets as Efficient Metal-Free Electrocatalysts for Oxygen Reduction Reaction: The Electron Spin Effect.

Direct nitrogen fixation at the edges of graphene nanoplatelets as efficient electrocatalysts for energy conversion.

Nitrogen fixation is essential for the synthesis of many important chemicals (e.g., fertilizers, explosives) and basic building blocks for all forms of life (e.g., nucleotides for DNA and RNA, amino acids for proteins). However, direct nitrogen fixation is challenging as nitrogen (N2) does not easily react with other chemicals. By dry ball-milling graphite with N2, we have discovered a simple, but versatile, scalable and eco-friendly, approach to direct fixation of N2 at the edges of graphene nanoplatelets (GnPs). The mechanochemical cracking of graphitic C−C bonds generated active carbon species that react directly with N2 to form five- and six-membered aromatic rings at the broken edges, leading to solution-processable edge-nitrogenated graphene nanoplatelets (NGnPs) with superb catalytic performance in both dye-sensitized solar cells and fuel cells to replace conventional Pt-based catalysts for energy conversion.

Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal-free eletrocatalysts for oxygen reduction reaction

A series of edge-selectively halogenated (X = Cl, Br, I) graphene nanoplatelets (XGnPs = ClGnP, BrGnP, IGnP) were prepared simply by ball-milling graphite in the presence of Cl2, Br2 and I2, respectively. High BET surface areas of 471, 579 and 662 m2/g were observed for ClGnP, BrGnP and IGnP, respectively, indicating a significant extent of delamination during the ball-milling and subsequent workup processes. The newly-developed XGnPs can be well dispersed in various solvents, and hence are solution processable. Furthermore, XGnPs showed remarkable electrocatalytic activities toward oxygen reduction reaction (ORR) with a high selectivity, good tolerance to methanol crossover/CO poisoning effects, and excellent long-term cycle stability. First-principle density-functional calculations revealed that halogenated graphene edges could provide decent adsorption sites for oxygen molecules, in a good agreement with the experimental observations.

Microstructure and Anti-Friction Effect of Ball-Milled Expanded Graphite

Expanded graphite (EG) was ball-milled in a high-energy mill (planetary-type) under an air atmosphere. The products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The anti-friction effect of milled EG used as lubricating additive was investigated. After ball-milling, the relatively ordered graphene planes of original EG become deformed, and the d002 spacing becomes broadened. The milled EG used as lubricating additive have an anti-friction effect, and the effect is more marked than that of original EG.

(Invited) Few-Layer Graphenes from Ball-Milling of Graphite with Triazine Derivatives

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Stable Dispersions of Graphene Layers From Ball-Milling of Graphite with Triazine Derivatives

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Morphological and physical investigation of carbon nanotube and graphene buffers used in high capacity lithium ion battery anodes

To investigate the effects of carbon nanotube (CNT) and graphene buffers for high capacity anode materials in lithium ion batteries, cupric oxide (CuO) nanoparticles supported on ball-milled graphite (BMG), were coated on either CNTs or graphene layers, which were reinforced with stainless steel gauze. Morphological buffer changes observed thoroughly by SEM indicated that volumetric expansion occurred in the CuO/BMG electrode containing the CNT buffer was smaller than in the electrode containing graphene as a buffer layer. This led the CuO/BMG–CNT electrode to remain high capacity retention (799mAhg−1) after 30 charge/discharge cycles, whereas the CuO/BMG and CuO/BMG–graphene electrodes showed 540 and 741mAhg−1, respectively. Due to higher volumetric expansion of the graphene buffer, the CuO/BMG–graphene showed large irreversible capacity and resistance, even though it had high initial capacity for lithium ion storage.

Disorder in ball-milled graphite revealed by Raman spectroscopy

High-energy ball milling has been used to produce nanocrystalline and amorphous structures in nature graphite, but Raman spectroscopy analysis shows that the structure of the amorphous phase produced by ball milling is less disordered than the amorphous structures in ion-beam bombarded graphite and sputtered amorphous carbon. The band intensity ratio (ID/IG) increases first and then drops to 1.1 after 40h of milling treatment, and remains constant during extended milling up to 100h. Electron microscopy observation and surface area measurement show that the formation of some nanosized clusters during the extended milling period might be responsible for the less disordered structure in the milled graphite.

Production of high quality single- or few-layered graphene by solid exfoliation of graphite in the presence of ammonia borane

A solid exfoliation method is developed for the synthesis of single- or few-layered (≤5 layers) graphene by ball milling of graphite with ammonia borane. Nearly quantitative yield in which ca. 25% is single-layered graphene can be obtained. We believe that this highly efficient method will offer a facile approach for the preparation of high quality and large quantity graphene.

Defect induced electronic states and magnetism in ball-milled graphite

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.

Mechanochemically driven solid-state Diels–Alder reaction of graphite into graphene nanoplatelets

A mechanochemically driven solid-state Diels–Alder reaction is demonstrated via dry ball-milling graphite as the diene in the presence of maleic anhydride or maleimide as the dienophile. On the basis of various characterizations, the Diels–Alder adducts are edge-selectively functionalized and subsequently delaminated into graphene nanoplatelets.

Large-Scale Production of Edge-Selectively Functionalized Graphene Nanoplatelets via Ball Milling and Their Use as Metal-Free Electrocatalysts for Oxygen Reduction Reaction

Edge-selectively functionalized graphene nanoplatelets (EFGnPs) with different functional groups were efficiently prepared simply by dry ball milling graphite in the presence of hydrogen, carbon dioxide, sulfur trioxide, or carbon dioxide/sulfur trioxide mixture. Upon exposure to air moisture, the resultant hydrogen- (HGnP), carboxylic acid- (CGnP), sulfonic acid- (SGnP), and carboxylic acid/sulfonic acid- (CSGnP) functionalized GnPs readily dispersed into various polar solvents, including neutral water. The resultant EFGnPs were then used as electrocatalysts for oxygen reduction reaction (ORR) in an alkaline electrolyte. It was found that the edge polar nature of the newly prepared EFGnPs without heteroatom doping into their basal plane played an important role in regulating the ORR efficiency with the electrocatalytic activity in the order of SGnP > CSGnP > CGnP > HGnP > pristine graphite. More importantly, the sulfur-containing SGnP and CSGnP were found to have a superior ORR performance to commercially available platinum-based electrocatalyst.

Nano-polycrystalline diamond formation under ultra-high pressure

Well-crystallized graphite and high energy ball-milled graphite were treated under 16GPa and temperatures up to 2500°C. Our experiments indicated that the ball-milled graphite can completely transform to nano-polycrystalline diamond (NPD) at 2100°C, while the well-crystallized graphite required 2500°C. The samples were characterized by X-ray diffraction, optical microscope, scanning electron microscope, and Vickers indenter hardness test. We found that high pressure not only made the conversion of graphite to NPD thermodynamically preferred, but also reduced the needed activation energy barrier. By analyzing thermodynamics and kinetics of the transformation, we suggested a low boundary for NPD forming region based on the phase diagram of carbon, and the formation mechanisms of Nano-polycrystalline diamond.

Performances of high voltage electrochemical capacitor using ball-milled graphite/Mn3O4 composite electrodes

A novel ball-milled graphite/Mn3O4 composite has been prepared directly through the reaction between high-energy ball-milled graphite and potassium permanganate under microwave irradiation. The microstructure and morphology of the composite have been investigated by X-ray diffraction and transmission electron microscopy. Three-electrode investigations show that the ball-milled graphite/Mn3O4 composite has a high potential window (ΔE=1.9V) in 1M Na2SO4 aqueous solution. A symmetric electrochemical capacitor has been built using graphite/Mn3O4 composite with 1M Na2SO4. This system exhibits ideal supercapacitive properties and stable cycle behavior while the cell voltage is set to as high as 1.8V.

SnO2 Nanoparticles Distributed on Multi-Walled Carbon Nanotubes and Ball-Milled Graphite as Anode Materials of Lithium Ion Batteries

SnO2 nanoparticles were supported on ball-milled graphite (BMG) or carbon nanotubes (CNTs) using a chemical reduction method with ethylene glycol, and the electrochemical properties of the nanocomposites were evaluated as anode active materials of lithium-ion batteries. The BMG and CNTs contributed to an increase in both the capacity enhancement and cyclic stability compared to that of commercial graphite. In particular, the mixture electrode of SnO2/BMG:SnO2/CNT = 3:1 (in weight ratio) showed higher performance in the reversible capacity and cyclic stability than did the SnO2/BMG and SnO2/CNT electrodes. This might be resulted from the network formation for excellent electronic path by CNT distributed on SnO2/BMG composites.

Preparation of Nano-Sized Graphite-Supported CuO and Cu-Sn as Active Materials in Lithium Ion Batteries

Nano-sized Cu-Sn and Cu oxide particles supported on ball-milled graphite were synthesized, and their electrochemical characteristics for use as anode active materials in lithium-ion batteries were investigated. The samples were also characterized via FE-SEM, XRD, and TGA. Most of the Cu oxides on BMG were monoclinic CuO crystals, whereas the Cu-Sn particles were composed of hexagonal Cu3Sn and tetragonal SnO2 crystals. These particles may contribute to an increase in the reversible capacity of lithium ion batteries.

Nanographene-based tyrosinase biosensor for rapid detection of bisphenol A

Hydrophilic nanographene (NGP) prepared by ball milling of graphite was used as the support to construct a novel tyrosinase biosensor for determination of bisphenol A (BPA). The performances of the nanographene-based tyrosinase biosensor were systematically compared with those of multiwall carbon nanotubes (MWNTs) modified tyrosinase biosensors. The results indicated that the nanographene-based tyrosinase biosensor provided significant advantages over MWNTs-based tyrosinase biosensor in term of response, repeatability, background current and limit of detection (LOD), which could be attributed to its larger specific surface area and unique hierarchical tyrosinase-NGP nanostructures. The nanographene-based tyrosinase biosensor displayed superior analytical performance over a linear range from 100nmolL−1 to 2000nmolL−1, with LOD of 33nmolL−1 and sensitivity of 3108.4mAcm−2M−1. The biosensor was further used for detecting BPA (leaching from different vessels) in tap water, and the accuracy of the results was validated by high performance liquid chromatography (HPLC). The nanographene-based tyrosinase biosensor proved to be a promising and reliable tool for rapid detection of BPA leached from polycarbonate plastic products and for on-site rapid analysis of emergency pollution affairs of BPA.

Ball-Milled Graphite as an Electrode Material for High Voltage Supercapacitor in Neutral Aqueous Electrolyte

Amorphous carbonaceous material with specific surface area of 422 m2 g−1 has been prepared from natural flake graphite by high-energy ball-milling under air atmosphere. Milling treatment introduces abundant oxygen functional groups (carboxyl and alkoxy) to the graphite surface, and oxygen content reaches as high as 11.5 atom% after 75 h milling. The ball-milled graphite exhibits a three electrode stable potential window of 1.8 V in 1 mol L−1 Na2SO4 aqueous electrolyte. Symmetric supercapacitor based on ball-milled graphite shows a stable charge/discharge cycle behavior when cell voltage is set as high as 1.6 V with a specific capacitance of 81 F g−1. The high utilization ratio (89%) of potential window for this system is attributed to the more negative value of E0V (electrodes potential when the cell voltage is set to 0 V).