Graphite, Applications of Artificial

Abstract

AbstractGraphite, with its exceptional strength and thermal stability at high temperatures, is a prime candidate material for many aerospace and nuclear applications. Its properties, through process modifications, are tailorable to meet an array of design criteria for survival under extremely harsh environmental operations. Aerospace and nuclear reactor applications of graphite demand high reliability and reproducibility of properties, physical integrity of product, and product uniformity. The manufacturing processes require significant additional quality assurance steps that result in high cost. Carbon and graphite exhibit excellent resistance to the corrosive actions of acids, alkalies, and organic and inorganic compounds, an attribute that has fostered the use of graphite in process equipment. Graphite is used extensively in the steel, food, petroleum, pharmaceutical, and metal finishing industries. The high thermal conductivity and thermal stability of graphite have made it a useful material in heat exchangers. Manufactured carbon and graphite exhibit varying degrees of porosity. Equipment fabricated from these materials must be operated at atmospheric pressure, or some degree of leakage must be tolerated. The resistance of graphite to thermal shock, its stability at high temperatures, and its resistance to corrosion permit its use as self‐supporting vessels to contain reactions at elevated temperatures (800–1700 °C), eg, self‐supporting reaction vessels for the direct chlorination of metal and alkaline‐earth oxides. For applications where fluids under pressure must be retained, imperviousness is attained by blocking the pores of the graphite or carbon material with themosetting resins. Impervious graphite shells and tubes are used in numerous applications for transferring thermal energy, eg, boiling, cooling, or condensing. Several grades of low density porous carbon and graphite are commercially available. Porous carbon and graphite are used in filtration of hydrogen fluoride streams, caustic solutions, and in aeration of waste sulfite liquors from pulp and paper manufacture. Carbon–graphite possesses lubricity, strength, dimensional stability, thermal stability, and ease of machining, a combination of properties that has led to its use in a wide variety of mechanical applications for supporting rotating or sliding loads in contact. Its principal applications are in bearings, seals, and vanes. With the exception of carbon use in the manufacture of aluminum, the largest use of carbon and graphite is as in electric‐arc furnaces. In general, graphite electrodes are restricted to open‐arc furnaces used in steel production. Because of their unique combination of physical and chemical properties, manufactured carbons and graphites are widely used in several forms in high temperature processing of metals, ceramics, glass, and fused quartz. Industrial carbons and graphites are available in a broad range of shapes and sizes. Various forms of carbon, semigraphite, and graphite materials have found wide application in the metals industry, particularly in connection with the production of iron, aluminum, and ferroalloys.