Графит

Химические свойства

Graphite is crystallized carbon and usually appears as soft, black scales. There are two types of graph ite, natural and artificial (activated). Natural and synthetic graphite may be mixed with each other or contain other additives.

Вхождение

Graphite is usually found in metamorphic rocks as veins, lenses, and pockets and as thin laminae disseminated in gneisses, schists, and phyllites. Depending upon the mode of occurrence and origin, it is graded into three forms: flake graphite found in metamorphosed rocks as vein deposits, crystalline graphite found as fissure-filled veins, and cryptocrystalline graphite formed in metamorphosed coal beds. Natural graphite occurs in many parts of the world in fair abundance and it has been used in various applications.
In nature, graphite is found usually in association with feldspars, mica, quartz, pyroxene, rutile, pyrites, and apatite. These impurities are associated with vein graphite. The impurities with amorphous graphite are shale, slate, sandstone, quartz, and limestone. Graphite is found in almost every country, but Ceylon, Madagascar, Mexico, western Germany, and Korea all possess particularly plentiful reserves. Major industrial producers of graphite are South Korea, the largest producer in the world, followed by Austria.

Использование

High-temperature lubricant, crucible container for handling molten metals such as Mg, Al, Zn, Ga, Sb, and Bi

Использование

For "lead" pencils, refractory crucibles, stove polish; as pigment, lubricant, graphite cement; for matches and explosives, commutator brushes, anodes, arc-lamp carbons, electroplating; polishing Compounds, rust and needle-paper; coating for cathode ray tubes; moderator in nuclear piles.

Определение

An allotrope of CARBON. Graphite is a good conductor of heat and electricity. The atoms are arranged in layers which cleave easily and graphite is used as a solid lubricant.

Общее описание

A mineral form of the element carbon. Hexagonal crystals or thin leaf-like layers. Steel-gray to black with a metallic luster and a greasy feel. An electrical conductor. Used for high-temperature crucibles, as a lubricant and in "lead" pencils.

Профиль реактивности

GRAPHITE is non-flammable in bulk form, but combustible. A reducing agent. Mixtures of graphite dust and air are explosive when ignited.Reacts violently with very strong oxidizing agents such as fluorine, chlorine dioxide, and potassium peroxide. Almost inert chemically when in bulk form. Keep away from ignition sources and oxidizing agents.

Угроза здоровью

Pure synthetic graphite acts as an inert or nuisance dust.

Промышленное использование

Graphite is a form of carbon. It was formerlyknown as black lead, and when first used forpencils was called Flanders’ stone. It is a naturalvariety of elemental carbon with a grayishblackcolor and a metallic tinge.
Carbon and graphite have been used inindustry for many years, primarily as electrodes,arc carbons, brush carbons, and bearings.In the last decade or so, development ofnew types and emergence of graphite fibers asa promising reinforcement for high-performancecomposites have significantly increasedthe versatility of this family of materials.

Возможный контакт

Natural graphite is used in foundry facings, steel making lubricants, refractories, crucibles, pencil “lead,” paints, pigments, and stove polish. Artificial graphite may be substituted for these uses with the excep tion of clay crucibles; other types of crucibles may be pro duced from artificial graphite. Additionally, it may be used as a high temperature lubricant or for electrodes. It is uti lized in the electrical industry in electrodes, brushes, con tacts, and electronic tube rectifier elements; as a constituent in lubricating oils and greases; to treat friction elements, such as brake linings; to prevent molds from sticking together; and in moderators in nuclear reactors. In addition, concerns have been expressed about synthetic graphite in fibrous form. Those exposed are involved in production of graphite fibers from pitch or acrylonitrile fibers and the manufacture and use of composites of plastics, metals, or ceramics reinforced with graphite fibers.

Перевозки

UN1362 Carbon, activated, Hazard Class: 4.2; Labels: 4.2-Spontaneously combustible material, International.

Методы очистки

Treat graphite with hot 1:1 HCl. Then filter, wash and the dried powdered is heated in an evacuated quartz tube at 1000o until a high vacuum is obtained. Cool this and store it in an atmosphere of helium [Craig et al. J Phys Chem 60 1225 1956].

Несовместимости

Graphite is a strong reducing agent and reacts violently with oxidizers, such as fluorine, chlorine trifluoride, and potassium peroxide. Forms an explosive mixture with air. May be spontaneously combustible in air.

Утилизация отходов

Do not incinerate. Carbon (graphite) fibers are difficult to dispose of by incineration. Waste fibers should be packaged and disposed of in a land fill authorized for the disposal of special wastes of this nature, or as otherwise may be required by law.