摘要:

Carbon materials (A-1, A-2 and A-3 derived from pitch cokes) with different graphitization degree, were allowed to react with potassium. The hydrogen-sorption behavior at 77 K, electrical resistivity. ESR and Raman spectra of the resulting compounds with the composition of KC60were determined. The sorbed amount at saturation, (nH2/nK)sat, was 0.55 and 1.43 for KC60s prepared from A2 (d002= 0.3377 nm) and A3 (d002= 0.3361 nm), respectively. No H2sorption was observed for KC60from A-1 (d002=0.342 nm). Temperature dependence of the resistivity of KC60s from A-2 and A-3 showed metallic behavior, contrary to semiconductive one for the host materials. However, KC60(A-1) showed semiconductive temperature dependence, similarily to the host material. Raman spectra of KC60s from A-2 and A-3 showed doublet structure, similarly to that of K-GICs from HOPG, characteristic for graphite intercalation compounds with stage n > 2. On the contrary, KC60(A-1) gave single peak at around 1597 cm−1. Those facts suggest that potassium exists in the interlayer spaces for KC60s (A-2, A-3), but not for KC60(A-1). It was also shown that g-factor of ESR spectra of KC60can be useful to predicting the H2-sorption behavior.

ISSN:1058-725X    

DOI:10.1080/10587250008025443

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The intercalation of sodium-potassium alloys into graphite leads, at room temperature, to compounds close to KC8. Graphite powder fits to large amounts of the alloy: up to compositions close to MC2, but the stable state is a mixture of KC8and alloy excess. In spite of the presence of large quantities of free alloy, liquid at room temperature, the powder does not agglomerate and constitutes an important solid reservoir for alkali metals.

ISSN:1058-725X    

DOI:10.1080/10587250008025444

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The chemical reactions of halogen molecules on a nano-graphite cluster are calculated using a semi-empirical calculational method. A real time calculation of the chemical reaction of halogen molecules up to 200 fs which is performed by the dynamic reaction coordinates (DRC) method of the quantum chemistry library shows that the iodine molecule exhibits a special reaction involving the removal of hydrogen atoms from edge carbon atoms. This result might be relevant to recent experiments on the graphitization of pitch at a low temperature of 400°C. We discuss the deformation of the nano-graphite cluster upon the intercalation of halogen atoms.

ISSN:1058-725X    

DOI:10.1080/10587250008025445

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Physical properties of fluorine-graphite intercalation compounds (GICs), namely semi-metal-metal and metal-insulator transitions and localization effects, are discussed based on13C and19F NMR data. NMR view on the nature of C-F bonding in fluorine-GICs and graphite fluorides is presented.

ISSN:1058-725X    

DOI:10.1080/10587250008025446

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Physical properties of the new compound Sc2B1.1C3.2, with-[B1/3C2/3]∝- graphite-like layers, were investigated and similarities to GICs observed, i. e. quadratic temperature dependence of resistivity and paramagnetic orbital susceptibility. Interestingly, it was indicated that 2D Anderson localization occurs at low temperatures. This was attributed to possible disorder in the -[B1/3C2/3]∝-layers.

ISSN:1058-725X    

DOI:10.1080/10587250008025447

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A basic nature of cubic Ag4Hf3S8for electrochemical Li insertion was examined with relation to cell properties and Rietveld analyses forex-situX-ray powder diffraction patterns observed at several discharge steps. The composition dependence of cell voltage curves observed in the closed type Li/lM-LiPF6in PC/Ag4Hf3S8cell showed a long plateau at around 2.2–2.0 V up to LixAg4Hf3S8(x ≤ 3). The cell voltage decreased with an increase of Li intercalation and final lithiated phase was assigned to cubic LixAgyHf3S8(x > 3, × + y = 7). The electrochemical lithiation of Ag4Hf3S8at low constant current densities proceeded topochemically. The structures of lithiated phases were solved without changing the space groupP4332 (No. 212) for Ag4Hf3S8host, indicating that Hf3S8framework structure was kept through the lithiation.

ISSN:1058-725X    

DOI:10.1080/10587250008025448

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Carbon onions were produced in a transmission electron microscope by electron beam irradiation of amorphous carbon with Pd clusters. High-resolution electron microscopy showed Pd atoms were intercalated between the graphite onion sheets, and the structural model for the intercalation was proposed. HREM images and diffraction patterns calculated for the model agrees well with the observed ones. The present work indicates that the electron-beam irradiation to amorphous carbon with Pd clusters is an effective method for the formation of intercalated onions.

ISSN:1058-725X    

DOI:10.1080/10587250008025449

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

RbC24and CsC24were allowed to react with isoprene, styrene or 1,3-butadiene. RbC24expanded slowly along the c-axis direction through contact with these unsaturated hydrocarbons. Monomer molecules are considered to be introduced into the interlayer of RbC24and polymerized. In the case of CsC24, isoprene was polymerized in a similar manner as RbC24and KC24, whereas the reactivity of styrene and 1,3-butadiene was low. The different reactivities are explained on the basis of the activity of polymerization initiators. The reactivity of monomers to polymerize in a certain GIC is in the following order: isoprene > 1.3-butadiene > styrene, which is the reverse order of reactivity recognized in the conventional polymerization.

ISSN:1058-725X    

DOI:10.1080/10587250008025450

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

CucCo1-cCl2-FeCl3graphite bi-intercalation compounds (GBIC's) have a c-axis stacking sequence of -G-I1-G-I2-G-I1-G-I2-G- (G = graphite layer, I1= CucCo1-cCl2layer, and I2= FeCl3layer). These compounds undergo magnetic phase transitions at Th, Tcu, Tcl, TSG, and TRSG(Th>Tcl>TRSG=TSG). depending on the Cu concentration. The phase transition at This related to a helical spin order. The phase transitions at Tcuand Tclare associated with a spin order of CucCo1-cCl2layers. The re-entrant spin glass phase below TRSGfor c≤0.4 and the spin glass phase below TSGfor c≥0.5 are due to the spin frustration effect occurring in FeCl3layers. The nature of these phases has been studied using SQUID DC magnetization and SQUID AC magnetic susceptibility.

ISSN:1058-725X    

DOI:10.1080/10587250008025451

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Electrochemically intercalated graphite with H2SO4was thermally expanded at 1000°C. Exfoliated samples of GIC-H2SO4with different times of expansion revealed different expansion volumes. Both the surface area and the chemical character of samples also depend on the exfoliation time. A low density of the exfoliated graphite is demanded for the oil sorption. The oil sorption is restricted by the surface area and the bulk density.

ISSN:1058-725X    

DOI:10.1080/10587250008025452

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor