Интеркаляционные соединения графита: структура, свойства и применение.

In the area of solid state chemistry. graphite intercalation compounds are materials prepared by intercalation of diverse guests into graphite. The materials have the formula (guest)Cn where n can range from 8 to 40's. The distance between the carbon layers increases significantly upon insertion of the guests. Common guests are reducing agents such as alkali metals. Strong oxidants, such as arsenic pentafluoride also intercalate into graphite. Intercalation involves electron transfer into or out of the host. The properties of these materials differ from those of the parent graphite.

The intercalation compounds graphite bisulfate and graphite perchlorate can be prepared by treating graphite with strong oxidizing agents in the presence of strong acids. In contrast to the potassium and calcium graphites, the carbon layers are oxidized in this process:
48 C + 0.25 O2 + 3 H2SO4 → [C24]+[HSO4]−·2H2SO4 + 0.5 H2O

In graphite perchlorate, planar layers of carbon atoms are 794 picometers apart, separated by |ClO4− ions. Cathodic reduction of graphite perchlorate is analogous to heating |KC8, which leads to a sequential elimination of |HClO4. Both graphite bisulfate and graphite perchlorate are better conductors as compared to graphite, as predicted by using a positive hole mechanism. Reaction of graphite with |[O2]+[AsF6]− affords the salt |[C8]+[AsF6]−. It proved to be a particularly fertile system on which to study phase transitions. A stage n magnetic graphite intercalation compounds has n graphite layers separating successive magnetic layers. As the stage number increases the interaction between spins in successive magnetic layers becomes weaker and 2D magnetic behaviour may arise.

Chlorine and bromine reversibly intercalate into graphite. Iodine does not. Fluorine reacts irreversibly. In the case of bromine, the following stoichiometries are known: |C {n}Br for n = 8, 12, 14, 16, 20, and 28. Because it forms irreversibly, carbon monofluoride is often not classified as an intercalation compound. It has the formula |(CF) {x}|. It is prepared by reaction of gaseous fluorine with graphitic carbon at 215–230 °C. The color is greyish, white, or yellow. The bond between the carbon and fluorine atoms is covalent. Tetracarbon monofluoride (|C4F) is prepared by treating graphite with a mixture of fluorine and hydrogen fluoride at room temperature. The compound has a blackish blue color. Carbon monofluoride is not electrically conductive. It has been studied as a cathode material in one type of primary (non rechargeable) lithium batteries. Graphite oxide is an unstable yellow solid.

Graphite intercalation compounds have fascinated materials scientists for many years owing to their diverse electronic and electrical properties.

Among the superconducting graphite intercalation compounds, |CaC6 exhibits the highest critical temperature Tc = 11.5 K, which further increases under applied pressure (15.1 K at 8 GPa). Analysis of pure |CaC6 using a high quality ultraviolet light revealed to conduct angle resolved photoemission spectroscopy measurements. The opening of a superconducting gap in the π* band revealed a substantial contribution to the total electron–phonon coupling strength from the π* interlayer interband interaction. Another potassium graphite compound, |KC24, has been used as a neutron monochromator. A new essential application for potassium graphite was introduced by the invention of the potassium ion battery. Like the lithium ion battery, the potassium ion battery should use a carbon based anode instead of a metallic anode. In this circumstance, the stable structure of potassium graphite is an important advantage.