Manufacture of high density, high strength isotropic graphite

摘要

Methods of producing high density, high strength, homogeneous graphite articles having densities of 2 or more and isotropic ratios of about 1.05 or less are disclosed. These methods achieve densification to levels above 2 g/cc yet take greatest advantage of increases in all structural properties and maintain isotropic quality. They involve impregnation of pre-formed isotropic graphite substrates of high density, having an isotropic ratio of 1.05 or less, 15 to 35 percent total porosity of which at least 50 percent is interconnected and open to the surface, average pore diameters of 1.5 to 5 microns, and narrow pore size distributions. A vacuum is drawn on the substrate after which it is contacted with highly fluid impregnant such as petroleum or coal tar pitch and then carbonized, baked and graphitized under conditions correlated to increase density without detectably modifying graphite matrix structure. This variable correlation assures maximum strength increase commensurate with density increase and avoids degradation of desirable properties such as isotropic ratio.