Intercalation compounds

Intercalation compounds

Crystalline or partially crystalline solids consisting of a host lattice containing voids into which guest atoms or molecules are inserted. Candidate hosts for intercalation reactions may be classified by the number of directions (0 to 3) along which the lattice is strongly bonded and thus unaffected by the intercalation reaction. Isotropic, three-dimensional lattices (including many oxides and zeolites) contain large voids that can accept multiple guest atoms or molecules. Layer-type, two-dimensional lattices (graphite and clays) swell up perpendicular to the layers when the guest atoms enter. The chains in one-dimensional structures (polymers such as polyacetylene) rotate cooperatively about their axes during the intercalation reaction to form channels that are occupied by the guest atoms. In the intercalation family based on solid C60 (buckminsterfullerene), the zero-dimensional host lattice consists of 60-atom carbon clusters with strong internal bonding but weak intercluster bonding. These clusters pack together like hard 1-nm-diameter spheres, creating interstitial voids which are large enough to accept most elements in the periodic table. The proportions of guest and host atoms may be varied continuously in many of these materials, which are therefore not true compounds. Many ternary and quaternary substances, containing two or three distinct guest species, are known. The guest may be an atom or inorganic molecule (such as an alkali metal, halogen, or metal halide), an organic molecule (for example, an aromatic such as benzene, pyridine, or ammonia), or both. See Crystal structure

Many applications of intercalation compounds derive from the reversibility of the intercalation reaction. The best-known example is pottery: Water intercalated between the silicate sheets makes wet clay plastic, while driving the water out during firing results in a dense, hard, durable material. Many intercalation compounds are good ionic conductors and are thus useful as electrodes in batteries and fuel cells. A technology for lightweight rechargeable batteries employs lithium ions which shuttle back and forth between two different intercalation electrodes as the battery is charged and discharged: vanadium oxide (three-dimensional) and graphite (two-dimensional). Zeolites containing metal atoms remain sufficiently porous to serve as catalysts for gas-phase reactions. Many compounds can be used as convenient storage media, releasing the guest molecules in a controlled manner by mild heating.

References in periodicals archive ?
The intercalated flake graphite when subjected to high temperatures (around 1000AC) expands due to the breakdown of intercalation compounds, which form gaseous products that exerts pressure on graphite layers and pushes them apart
Henry, and P Willmann, "Electrochemical synthesis of binary graphite-lithium intercalation compounds," Materials Research Bulletin, vol.
Graphite intercalation compounds (GICs), formed by inserting ionic species into the lattice of the graphite structure, are typically layered materials consisting of intercalate guest and graphite layers [7, 8].
Fedorov, "The synthesis and properties of highly exfoliated graphites from fluorinated graphite intercalation compounds," Carbon, vol.
Most practical methods of disintegration of HTR fuel elements studied in the past made use of the fact that graphite forms so-called intercalation compounds with certain elements, accompanied by enlargement of the C-spacing of graphite lattice [5-7].
Other less common but noteworthy liquid exfoliation methods include intercalation of graphite with alkaline [25] or halogen salts [26] to form graphite intercalation compounds (GICs).
Tiralti, "Intercalation compounds of hydrotalcite-like anionic clays with anti-inflammatory agents, II: uptake of diclofenac for a controlled release formulation," AAPS PharmSciTech, vol.
Molecular Crystals and Liquid Crystals Science and Technology, Section A: Molecular Crystals and Liquid Crystals, v340, ISIC 10-10th International Symposium on Intercalation Compounds, 113 (2000).
Such motion may be facilitated by lattice distortions in the hexagonal hydrogen planes in a manner similar to that observed in graphite intercalation compounds.
J.D.: Lithium-ion batteries use intercalation compounds as electrode materials.
Eleven chapters specifically discuss nanocomposites of polymers and inorganic particles, hybrid organic/inorganic particles, intercalation compounds and clay nanocomposites, porous hybrid materials, sol-gel processing of hybrid organic-inorganic materials based on polysilsesquioxanes, natural and artificial hybrid materials, medical applications, optical applications,electronic and electrochemical applications, and inorganic/organic hybrid coatings.
Lithium intercalates in the structure of graphite to form Li-C compounds with varying stoichiometry, depending on voltage, which are known as graphite intercalation compounds (GIC).