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Despite the intense interest in nanocarbon for a variety of engineering applications, many details of their relative thermodynamic stabilities remain mysterious. Here, a unified thermodynamic model for the thermodynamic stabilities of nanocarbon in different polymorphs is presented based on energetic contributions of surface energy and surface stress on total Gibbs free energy of systems. Through...
The structural and electronic properties of bulk graphite were compared using density functional theory calculations with the local density (LDA) and generalized gradient (GGA) approximations to determine the relative ability of each to model this material. The GGA fails to generate interplanar bonding, but the LDA does, even though the band structures obtained from both approximations were essentially...
A stage-2 HoCl 3 -GIC has been synthesized and characterized by XRD experiments and magnetic measurements. EDS and 00l X-ray analyses lead to the chemical formula C 23.8 HoCl 3.7. The c-axis repeat distance is 1313±5pm, and the stacking sequence of intercalated HoCl 3 along the c-axis corresponds to the layer sandwich Cl–Ho–Cl, where the distance between Ho and Cl layers...
Carbon black pastes were found to be effective as coatings for improving the performance of thermal gap-filling materials, including flexible graphite, aluminum and copper. The thermal contact conductance across copper mating surfaces was increased by up to 180%. A fluidic form of carbon black paste (based on polyethylene glycol) was more effective than a thixotropic form (based on polyol esters)...
A novel and inexpensive chemical route leading to obtain macroscopic quantities of room temperature magnetic carbon is reported. This route consists of a controlled etching on the graphite structure, performed by a redox reaction in a closed system between graphite and CuO. X-ray diffraction suggests that this modified graphite could be represented by the coexistence of a matrix of pristine graphite...
Through the tight-binding model, the effect of electric field on electronic and optical properties of a zigzag (an armchair) H-terminated nanographite ribbon is studied. The effective electric field shifts the Fermi level (E F ), modifies the energy dispersions, alters the subband spacing, produces the new edge state, changes the band gap, and causes the semiconductor–metal transitions. First,...
One of the most important parameters characterizing the performance of brake materials is their formulation. Therefore, the precise analysis of brake materials is needed both to investigate formulation-performance relationship, and to maintain quality control. A typical brake composite contains more than ten phases (components), either crystalline or amorphous. Combinations of X-ray diffraction (XRD),...
The solid state reactor is an advanced reactor concept that takes advantage of newly developed materials with enhanced heat transfer characteristics to provide an inherently safe, self-regulated heat source. High conductivity graphite foam, developed and produced at Oak Ridge National Laboratory, is being evaluated as a candidate material for the core of basic heat source modules.Irradiation studies...
Nano-structural graphite prepared by ball milling under H 2 or Ar atmosphere was studied as an electrode for electric double layer capacitors (EDLCs) by means of a conventional 2-electrode galvanostatic method. Especially, the product prepared under H 2 atmosphere using zirconia balls revealed 500m 2 g −1 surface area and showed 12Fg −1 specific capacitance,...
Diamond crystals with high nitrogen concentration, 1000–2000ppm, have been successfully synthesized from the system of powder catalyst (Fe–Ni)–C-additive NaN 3 in a cubic anvil high-pressure and high-temperature apparatus. The synthetic diamond crystals are cubo-octahedral or octahedral shape with a green or dark green color. The FTIR spectra of the diamond synthesized indicate that its nitrogen...
The thermal expansion coefficient (CTE) of Gilsocarbon graphite samples has been measured using strain gauges whilst the samples were subject to either tensile or compressive static loading. Compressive loading increased the CTE from ∼5.4×10 −6 K −1 to ∼8×10 −6 K −1 for a compressive load of −50MPa, whilst tensile loading decreased the CTE to ∼4×10 −6 K ...
Fatigue behaviour of polycrystalline, isotropic graphite FU2590 (porosity 13vol%) and of FU2590 infiltrated with the aluminium alloy AlSi7Mg (FU2590/AlSi7Mg) is investigated. The interpenetrating graphite–aluminium composite is produced by squeeze casting infiltration, where the open porosity of FU2590 (10–11vol%) is infiltrated with AlSi7Mg. Fully reversed bending fatigue tests at cycling frequency...
Platelet graphite nanofibers are materials produced from the decomposition of carbon monoxide and hydrogen over iron powders. The surface consists of terminated graphite edges, differing from traditional graphite materials in which basal plane graphite surfaces dominate. The 3-dimensional morphology and crystal face exposure on the nanofiber surface was determined by selected area electron diffraction...
Comparative studies of first- and second-order Raman spectra of multi-walled carbon nanotubes (MWCNT) and three other graphitic materials – carbon fiber, powdered graphite and highly ordered pyrolytic graphite – are reported. Three laser excitation wavelengths were used: 514.5, 785 and 1064nm. In first-order Raman spectra, the positions of the bands D, G and D′ (1100–1700cm −1 ) presented...
The present study highlights the electrochemical performance of two series of fluorinated graphites used as the cathode in primary lithium batteries. These compounds were prepared under fluorine gas at room temperature using a catalytic atmosphere made of boron or chlorine fluoride, and then thermally treated between 100 and 600°C. The electrochemical properties are correlated to a complete physico-chemical...
The strain induced by electrochemical charging was studied for a series of carbon materials in two different aprotic electrochemical double layer capacitor electrolytes: 1M tetraethylammoniumtetrafluoroborate in propylene carbonate and in acetonitrile. Five different carbon samples were investigated: a powder of mesocarbon microbeads (MCMB), a high surface area graphite, an activated carbon (AC)-based...
Crystalline graphite with compound curvature has been produced by precipitation of carbon from metal carbide solutions. Nearly spherical graphitic shells hundreds of microns thick have been synthesized on top of millimeter-sized spherical transition metal cores in high vacuum. Raman spectroscopy, backscatter electron diffraction and X-ray analysis shows the shell to be composed of highly crystalline...
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