Document Type and Number:
Japanese Patent JPS4817595
Kind Code:
B1
Abstract:
1,219,714. High density isotropic graphite. UNITED STATES ATOMIC ENERGY COMMISSION. 26 March, 1969 [15 April, 1968], No. 15743/69. Heading C1A. A high density isotropic graphite body is prepared by first wet blending a mixture of graphite having an average particle size of less than 5 microns and pitch, shaping the mixture so as to give a body of density in the range 1À70-1À95 gms./c.c., by die pressing the initial mixture after screening to a desired particle size to form an anisotropic graphite billet, comminuting said billet into particles of said preselected size e.g. 200 mesh U.S. and isostatically pressing these comminuted particles into a body of the desired density then carbonizing the isotropic body whilst in the die so as to maintain the said density and then impregnating with pitch by isostatic pressing at a pressure of at least 4500 p.s.i. and a temperature of 200‹ C., heating the impregnated body whilst submerged in pitch to carbonize the pitch, repeating the impregnation and carbonization step until the body has a density of at least 1À95 gms./c.c. and then finally graphitizing the body e.g. at a temperature of 3000‹ C. If desired, solvent e.g. benzene, may be added to the graphite-pitch mixture. The product of the process is a graphite having a density of at least 1À95 g./c.c. a gas (helium) permeability of below 2 x 10-4 cm.2 /sec. the product being 100% graphite and has essentially the same coefficient of thermal expansion along any of its axes. The tensile strength, compressive strength, average pore size and isotropic ratio are given. The graphite powder used may have a particle size from less than 5 microns to 0À03 micron and comprise 85 parts by weight of 5 micron particles and 15 parts by weight of 0À03 micron particles to which mixture 25 parts per hundred of pitch are added. The purity of the graphite flour used is listed. The pitch may have a softening point of 140‹ C.
Application Number:
JP2895169A
Publication Date:
May 30, 1973
Filing Date:
April 14, 1969
Export Citation:
International Classes:
B01J2/28; C01B31/00; C04B35/52; C04B35/532