摘要:

Recently, we have successfully synthesized new type of high-Tcsuperconductors of (HgX2)0.5Bi2Sr2Cam-1CumOy(X˭Br, I, and m = 1,2) by means of intercalation technique. From the X-ray diffraction(XRD) and X-ray absorption spectroscopy(XAS) analyses, we found that the intercalated mercuric halides are stabilized as the isolated gaseous molecules in the interlayer space of superconducting lattice, leading to an increase of basal spacing. A small amount of charge transfer between guest molecule and host lattice could be observed upon intercalation with a slight depression ofTc. For the extension of metal halide intercalation into high-Tc, superconductor, we have developed new type of hybridized superconducting nanohybrid with periodic stacking of organic and superconducting layer by stepwise synthetic approach, where organic compounds are stabilized in the form of organicinorganic complex salt in-between Bi-O double layers of Bi-based high-Tccuprates. The synthetic strategy proposed here can be applicable to many other layered systems.

ISSN:1058-725X    

DOI:10.1080/10587259808045337

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Confocal Raman Microspectrometry is shown to be a powerful technique to study electrochemical devices under working conditions with a spatial resolution of about l μm3. This is first illustrated on a Li/P(EO)20, LiTFSI/Li symmetrical cell where salt concentration gradients in the polymer electrolyte are measured as a function of current density and time. These data give access to transport properties of the polymer electrolyte, namely transport numbers and diffusion coefficients. A second example is provided by electrostatic supercapacitors using activated carbon fabrics of high specific surface area and proton conducting liquid electrolytes. A mapping of a carbon fiber and of the surrounding electrolyte is recorded for ± IV polarizations. The relative intensity and the frequencies of the D and G Raman lines of carbon are found to be very sensitive to the carbon charge.

ISSN:1058-725X    

DOI:10.1080/10587259808045338

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Through Raman spectroscopy studies, we show that mechanical grinding generates an increasing amount of unorganized carbon at a rate depending on the type of grinding mode used (Shear and Shock-type grinding). The first-order Raman spectrum for pure unground graphite has a well-known G sharp band at 1579 cm−1, which corresponds to the E2gvibration while the ground samples present a broadened G band accompanied by new components at about 1610 cm−1(D′), 1510 cm−1(D″) and 1348 cm−1(D), usually explained as arising from disorder and defects1. Shock-type grinding produces a faster disorder increase than shear-type grinding. The latter preserves part of the graphitic character. The general effect of mechanical milling remains however opposite to that of Thermal Treatment (Graphitization).

ISSN:1058-725X    

DOI:10.1080/10587259808045339

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Graphite fragments on a nanometer scale can present a distinctive edge state depending on the edge shape. By examining the electronic band structure of graphite ribbons within the Pariser-Parr-Pople model, we study the effect of the electron-electron interaction on the edge state. Depending on the ribbon widthN, the long-range Coulomb interaction affects the edge state of narrow ribbons. The characteristics of the edge state, however, still persist in zigzag ribbons of a few nanometer width. Recent experimental approaches to synthesize nanographite are also introduced.

ISSN:1058-725X    

DOI:10.1080/10587259808045340

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

XPS, UPS and STM are used to characterize a second stage NaOxCycompound. The charge distribution and the cleavage localization are discussed.

ISSN:1058-725X    

DOI:10.1080/10587259808045341

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

XPS, UPS and STM are used to characterize a first stage CsOxCycompound. The charge distribution and the cleavage localization are discussed.

ISSN:1058-725X    

DOI:10.1080/10587259808045342

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The ultraviolet photoelectron spectra measurements for 1st and 2nd stage potassium-oxygen-graphite intercalation compounds (KOx-GICs) were carried out for the electronic structure around the Fermi levelEF. The dependence of the photoelectron spectra upon the incident photon energy suggests the presence of the oxygen electronic states aroundEF. The temperature dependence of the thermoelectric power (TEP) of KOx-GICs reveals the positive TEP below around 150 K for 1st stage compound, which suggests the contribution of hole carriers to the transport properties in contrast to the expectation of negative TEP endorsed by the donor type character of KOx-GICs. These experimental findings prove the contribution of intercalate to the electronic structure and transport properties.

ISSN:1058-725X    

DOI:10.1080/10587259808045343

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

CuCl2graphite intercalation compounds (GICs) having CuCI2magnetic intercalate layers are expected to give novel magnetic layer effect on their transport phenomena, through the π-d interaction. We investigate the transport properties of stage 1–4 CuCl2GICs by means of c-axis magnetoresistance (MR) and thermoelectric powers. In stage-1 compound, anomalously large MR is observed for the field perpendicular to the c-axis, indicating a remarkable difference in the magnetic field direction dependence from that of in-plane MR governed by the cyclotron motion of the carriers. This implies the important role of the magnetic layers in the c-axis hopping process. The c-axis thermoelectric power shows an anomalous change around 70–100 K where a short range order hump appears in the magnetic susceptibility.

ISSN:1058-725X    

DOI:10.1080/10587259808045344

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A general theory on the c-axis resistivityρcand longitudinal magneto-resistance δρc/ρ0in graphite intercalation compounds (GICs) is presented and theory provides a reasonable explanation for the observed results of MoCl5GICs.

ISSN:1058-725X    

DOI:10.1080/10587259808045345

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We have examined the c axis electrical resistivity ρCof high stage (5 ≤ s ≤ 12) GaCl3intercalated graphite from 4.2 ≤ T ≤ 295 K. All materials are highly anisotropic. There is a progressive change from “metallic” behaviour with dρc/dT > 0 over the full T range to semiconductor-like (dρc/dT < 0) as s rises. It is shown that interstratification and intercalate layer crystallization strongly influence ρC(T).

ISSN:1058-725X    

DOI:10.1080/10587259808045346

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor