Alkali Metal-graphite Compounds Research Articles

A Study of the Temperature-Dependence of Low-Frequency, Raman-Active Phonons in Stage-2 Graphite-K and Graphite-Rb Intercalation Compounds

ABSTRACTWe report results from a Raman scattering study of stage 2 Graphite-Rb and Graphite-K in the low frequency region (ω < 150 cm-1) as a function of temperature (80K < T < 300K). Four features are seen in the 80K spectra and are interpreted in terms of a Born– von Kármán lattice dynamics model. The temperature-dependence of the Raman spectra is discussed in connection with reported phase transitions in stage 2 alkalimetal graphite compounds.

Basal plane resistivity of alkali metal-graphite compounds

We present a comprehensive series of measurements of the basal plane electrical resistivity of well defined first to tenth stage heavy alkali metal-graphite binary compounds, first to third stage lithium-graphites, and some high stage sodium-graphite binaries, using highly oriented pyrographite. Maximum conductivity for all the heavy alkali metal compounds occurs for the fifth stage, while the value for first stage LiC6 is considerably lower. Transitions have been found in the case of the heavy alkali metal compounds for high stages bearing striking resemblance to the well known lambda transitions of the graphite-nitric acid products. The temperature dependence above and below the anomalies has been analyzed. The effect of intercalation-desorption order has been shown.

Polymérization anionique de l'isoprène par les insertions ternaires graphite–métal alcalin–solvant

AbstractThe examination by HR–NMR of the microstructure of polyisoprenes synthesized in the presence of alkali metal–graphite compounds reveals that the polymerization has an anionic character. The microstructure of the polymers depends on the nature of the active centers, which depends on the solvent used in the preparation of the graphite compounds or as polymerization medium. With powdered alkali metal–graphite compounds, the propagation does not differ from the anionic one occurring in a homogeneous medium. Except for K–graphite, an enhancement of the 1–4 addition mode is observed if grains of Li or Na–graphite are used in mass polymerization. This change in the microstructure could be explained by the competition between the rate of propagation and the rate of diffusion of the growing chains from the grains to the homogeneous phase of the polymerization medium.