摘要:

The interplay between d cationic levels and sp anionic band may result in a partial depopulation of the latter. The holes that are created may associate and lead to anionic catenation with a possible cut-off of the top of the sp band. In any case electrons transferred through an intercalation process will be accepted on levels which are largely anionic in character. Holes at the top of sp bands are at the origin of a nice soft chemistry of the redox type. Their neutralization by electrons allows to stabilize unusual structural types.

ISSN:1058-725X    

DOI:10.1080/10587259808045307

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Intercalation of alkali metals into graphite and other carbon matrices with large volume decrement is favored by high pressures: the temperature of the reaction decreases and the amount of intercalated metal increases 2 to 3 times in comparison with the compounds obtained under traditional conditions. Superdense alkali metal in carbon matrices exposes unusual valence state with high degree of p- and d-states in chemical bonding.

ISSN:1058-725X    

DOI:10.1080/10587259808045308

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

LiC2, the super-dense high pressure phase of lithium intercalated graphite retains a high Li density upon pressure release; it stabilizes at LiC2.18if 0.5 at.% boron-substituted graphite is used for synthesis. We investigate it's in-plane structure and thermal decomposition using high resolution X-ray powder diffraction. This yields a 2⨿3 hexagonal cell with a = 8.54 Å and c = 3.71 Å. LiC2.18is stable indefinitely at ambient T and P. Above 100°C, a decomposition product LiC3.4–3.8is observed, corresponding to the stable phase at ambient conditionswithoutboron. In both cases, we attribute the decomposition to Li diffusion with formation of (meta)stable Li7clusters; we speculate that the boron impurity impedes this process and thereby ‘pins’ the denser of the two superlattices.

ISSN:1058-725X    

DOI:10.1080/10587259808045309

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

First stage intercalation compounds were obtained using vapor reaction of heavy alkali metals (M ˭ K, Rb and Cs) with BXC1−xplatelets (x=0.1 and x=0.25). Depending on the value of x, M(B0.1C0.9)8±1and M(B0.25C0.75)10±1compounds were formed. Intensity calculations of the001lines suggested domains of M(BXC1−x)5first stage dense structure. As formed B0.25C0.75was incompletely intercalated by cesium from its liquid ammonia solution whereas extended intercalation was obtained with heat treated B0.25C0.75host (T=1600°C) giving a first stage Cs(B0.25C0.75)12derivative.

ISSN:1058-725X    

DOI:10.1080/10587259808045310

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Intercalation into graphite of electron donors is discussed, regarding the nature of the chemical species to be intercalated. In the binary compounds, the intercalated sheets are always mono-layered, while, in the ternaries, they are poly-layered, as soon as the electronegativities of both intercalated elements exhibit a sizeable difference. In the case of the ternary compounds, the intercalated sheets can be regarded as 2D slices of the corresponding bulk binary compounds. These slices are subjected to various distortions, that are caused by the presence of the adjacent graphene planes

ISSN:1058-725X    

DOI:10.1080/10587259808045311

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In a first part a thermodynamic explanation of the differences between the binary sodium GICs and those of the other alkali metals (low stages lack, octal structures at the high stages) is proposed. The second part mainly concerns the cointercalation of sodium and its halides leading to ternary GICs. Their composition and structure are connected to the reaction temperature and to the structure and lattice energy of the free halides.

ISSN:1058-725X    

DOI:10.1080/10587259808045312

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

New first stage ternary graphite-potassium-chalcogen compounds were synthesized. They are very rich in alkali metal : their chemical formulas are close to KC3AX(A = sulphur or selenium). We studied their structural arrangement by X-ray diffraction. We calculated the charge transfers and measured the electrical resistivities.

ISSN:1058-725X    

DOI:10.1080/10587259808045313

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

New first stage ternary compounds associating potassium and phosphorous were synthesized in liquid potassium containing a few atomic percent of red phosphorous. The structural arrangement of these alkali metal rich phases was studied by X-Ray diffraction. Electrical measurements parallel and perpendicular to the c-axis were carried out between room temperature and 4.2 K.

ISSN:1058-725X    

DOI:10.1080/10587259808045314

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The paper deals with the synthesis and structure of FeCl3-CrO3-graphite bi-intercalation compound (FeCl3-CrO3-GBC) prepared during the subsequent intercalation of chromium trioxide into stage-2 FeCl3-GIC/graphite system. From the results of the X-ray diffraction measurements and the scanning electron microscopy coupled with energy dispersive X-ray analysis it was concluded that the product consists of a mixture of saturated FeCl3-CrO3-GBC and stage-2 FeCl3-GIC. Based on the model of the transformation from stage-2 FeCl3-GIC/graphite system to FeCl3-CrO3-GBC, it can be understood that upon the subsequent intercalation process CrO3is intercalated in the interlayer spacings of graphite both free and occupied by FeCl3. Due to the latter invasion the double-layer co-intercalation domain is formed whereas a part of FeCl3is displaced to the zone of the pristine graphite present in the host FeCl3-GIC.

ISSN:1058-725X    

DOI:10.1080/10587259808045315

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

KC24was reacted with dehydrated benzene for a week at room temperature and then for a month at 70°C. The ternary K-Bz-GIC obtained at room temperature decomposed very slowly, when the sample was immersed in water. In case the ternary compound was heat treated at 70°C, the stability in water was very high. This unusual stability is due to the oligomerization of benzene, and hence we abbreviate the heat treated ternary compound as K-(Bz)n-GIC. The thermostability of K-(Bz)n-GIC was evaluated by XRD measurements and elemental analyses; the sample decomposed partly at 200°C and thoroughly decomposed to graphite at 200–400°C. The reaction of K-(Bz)n-GIC with NH3and Cl2gas are also discussed.

ISSN:1058-725X    

DOI:10.1080/10587259808045316

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor