摘要:

A new approach to study of micro texture and structure of graphite intercalation compounds (GICs) is shown using high resolution transmission electron microscopy (TEM) combined with image analysis and fuzzy reasoning. As a result of application of the frequency analysis using 2-dimensional (2D) fast Fourier transform (FFT) to the CuCl2-GICs, a characteristic power spectrum pattern called streak, which is similar to an electron diffraction pattern, is obtained. The images correspond to the specific frequencies are reconstructed by 2D inverse FFT (IFFT). Then the stage structure of CuCl2-GICs is investigated.

ISSN:1058-725X    

DOI:10.1080/10587250008025473

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The Hall effect, Shubnikov-de Haas effect (SdH), and electrical conductivity have been studied in the temperature range 0.3–4.2 K in magnetic fields up to 8 T in acceptor type graphite intarcalated compounds (GICs) of low stages and in low density carbon materials (graphite foils), produced by the thermal destruction of GICs. The parameters of the energy spectrum of carriers were determined. For graphite foils (GFs) the negative magnetoresistance and logarithmic dependence of the electrical conductivity on temperature was found at low temperatures. These data testify to weak localization beyond the diffusion limit.

ISSN:1058-725X    

DOI:10.1080/10587250008025474

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The present work means to study the infrared spectra and to determinate energy spectra parameters of current carriers for graphite intercalation compounds of low stages with sulfur acid in the presence of different oxidizers, where oxidizers are K2Cr2O7, KMnO4, Ce(SO4)24(NH4)2SO4·2H2O, (NH4)2S2O8, and for low density graphite materials (flexible graphite foils) produced on their base.

ISSN:1058-725X    

DOI:10.1080/10587250008025475

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We report the band structures of first stage potassium intercalated graphyne using the optimized geometries. The calculation was carried out using the full-potential linear-combination-of-atomic-orbitals method. The optimized distance between two graphyne layers sandwiching the intercalate layer is shorter than typical graphite intercalation compounds. These intercalation compounds are metallic. The character of the band around the Fermi level at ⌜ point is C2pz. The band with the character of K4slies about 2.4 eV higher than the Fermi level at ⌜ point for the compound intercalating one potassium in a unit cell, while that lies about 0.89 eV higher than the Fermi level at ⌜ point for intercalating two potassium in a unit cell. Further we refer the amount of charge transfer between potassium and carbon atoms.

ISSN:1058-725X    

DOI:10.1080/10587250008025476

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We have theoretically studied the structure and electronic state of the sodium-hydrogen-graphite ternary intercalation compound based on the first-principles calculation. As concerns the structure, it is suggested that intercalated hydrogen is in the H2molecular form. As for the electronic state, both the antibonding π*-bands of graphite and 1sσ* band of H2with a small dispersion form the metallic states.

ISSN:1058-725X    

DOI:10.1080/10587250008025477

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

An Sc based borocarbide Sc2B1.1C3.2with a two-dimensional graphite-like network has been synthesized by a solid state chemical reaction route. Crystals have been grown by floating-zone method at different speeds and growth direction could be assigned to be parallel to ⟨110⟩axis.

ISSN:1058-725X    

DOI:10.1080/10587250008025478

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The paper deals with the synthesis of ZnCl2-CrO3-H2SO4-graphite bi-intercalation compound (ZnCl2-CrO3-H2SO4-GBC). For observing the concentration profiles of intercalates in both ZnCl2-GIC and ZnCl2-CrO3-GBC the energy dispersive X-ray (EDX) analysis coupled with the scanning electron microscopy (SEM) were used. The X-ray diffraction (XRD) analysis and the cyclic voltammetric (CV) measurements were used to investigate the transformation of the starting ZnCl2-GIC to the ternary ZnCl2-CrO3-GIC followed by the successive electrochemical intercalation of H2SO4resulting in the quaternary ZnCl2-CrO3-H2SO4-GBC. The present results argue for the formation of co-intercalation domains embedded in the lattice of bi-intercalation compound.

ISSN:1058-725X    

DOI:10.1080/10587250008025479

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Based on first-principles calculations, structure optimization of Pd intercalated graphite is performed and the equilibrium values for lattice constants are obtained, in agreement with experimental values. In graphite the carbon atoms within the basal plane are bound together by strong covalent σ-bonds, while atoms in adjacent layers are weakly bound by Van der Waals bonds, results in semimetal. Being intercalated with Pd, due to Pd-4d and C-2p hybridizations, partial charge transfers occur from Pd to C, which increase the density of states at Fermi level and make the compound metallic-like; the heat of formation is found to be 2.45eV for per Pd atom intercalation.

ISSN:1058-725X    

DOI:10.1080/10587250008025480

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Activated carbon fibers (ACFs) are microporous systems comprised of a random network of nano-sized graphites. We investigated the structure and electronic properties of fluorinated ACFs in order to clarify the effects of fluorine-introducedsp3-carbon sites on the electronic state of the nano-sized π-electron system. The orbital diamagnetism is monotonically reduced with increasingF/C, suggesting that introducedsp3carbon sites make the extended π-conjugated system reduced. In the intermediate fluorine concentration region, the localized spin concentration is enhanced by fluorination, reaching a maximum atF/C∼ 0.8, whereas it tends to be lowered in the high concentration region. The enhancement in the spin concentration is explained in terms of the local destruction of the π-conjugated system at interior carbon sites by fluorine-inheritedsp3-carbon sites.

ISSN:1058-725X    

DOI:10.1080/10587250008025481

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Novel graphite biintercalation compound with layers of SmCl3and ErCl3is synthetized by the one-zone vapour method. A well defined stage-3 SmCl3graphite intercalation compound with the c-axis repeat distance Ic= 16.60 ± 0.07 Å is used as the host matrix. The X-ray diffraction shows a creation of a new compound with Ic= 19.70 ± 0.05Å. Based on these data a … G-SmCl3-G-ErCl3… stacking sequence is proposed. The electron diffraction shows a-axis of the intercalated layer is rotated with respect to the graphene a-axis by 42°, and 19°, 42° for SmCl3and ErCl3layers, respectively. The parameters of the lattices obtained are aSmC13=7.37 Å, aErCl3= 6.75 Å, and bErC13= 11.73 Å.

ISSN:1058-725X    

DOI:10.1080/10587250008025482

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor