Method of making shaped carbonaceous bodies

Shaped graphitic or graphite-like carbonaceous bodies are produced by forming binder-coated particles of a carbonaceous filler in a slurry, shaping the slurry or paste of the particles to the desired configuration, drying and cokefying the shaped body. The system is suitable for the production of graphitic structures for use in high-temperature gas-cooled nuclear reactors, as casting molds and the like. The present invention starts with the assumption that binder-coated filler particles are available, the particles having been coated uniformly (e.g. as described in U.S. Pat. No. 4,009,143.

FIELD OF THE INVENTION 
Our present invention relates to a method of producing, without pressure, 
shaped carbonaceous bodies and, more particularly, to the production 
without pressure of graphitic or graphite-like bodies (synthetic-graphite 
bodies) having good mechanical properties at relatively low cost, said 
bodies consisting of binder-coated filler particles. 
BACKGROUND OF THE INVENTION 
In the art of forming carbonaceous bodies, it is frequently desirable to 
use carbonaceous materials which may be waste products or byproducts of 
other processes as a source of graphitic carbon although the carbonaceous 
material may be in an amorphous or nongraphitic state. For example, 
petroleum coke, carbon black and even electro graphite or natural graphite 
are desirable sources of graphitic material for the production of shaped 
graphite or graphite-like bodies. 
Graphite bodies have been employed heretofore for many purposes and in 
various industries. For example, high-temperature gas-cooled nuclear 
reactors may make use of graphitic bodies for the structure of the 
nuclear-reactor core, as sheaths for nuclear-fuel elements, as enclosures 
for fertile elements in breeder reactions, and as components of nuclear 
fuel or breeder particles. In the metallurgical industry and in the 
glass-making field, graphite molds or molds lined with graphite or 
graphite-like materials are used for casting. In general, graphitic bodies 
have been employed whenever hightemperature processes may be involved 
because they have a refractory and generally inert character. In nuclear 
reactors especially, they have proved to be desirable because of the 
neutron cross-section of graphitic materials and their reduced tendency to 
produce reaction products which interfere with the operation of a nuclear 
reactor. 
Common methods of producing graphite-like bodies involve the extrusion of 
ram-pressing of synthetic graphite or graphite-like products to shape them 
into the desired configuration. These systems frequently require 
after-treatment of the graphite-like bodies and make use of relatively 
expensive equipment because it has been difficult heretofore to impart a 
well-defined shape to the graphitic materials and at the same time provide 
high compressive strength and other desirable mechanical properties. 
OBJECTS OF THE INVENTION 
It is, therefore, the principal object of the present invention to provide 
a method of making shaped bodies of synthetic graphite or materials 
similar to synthetic graphite, i.e. to produce graphite-like bodies, 
whereby the disadvantages of earlier systems can be avoided and, without 
using pressure, relatively intricate bodies can be made with good 
mechanical characteristics at relatively low cost. 
It is another object of the invention to provide an improved method of 
making graphite-like bodies of uniform or homogeneous cross-section, 
highly compressive strength and complex configuration without the 
disadvantages of ram-press systems as described above. 
Yet another object of the invention is to provide a method of making shaped 
carbonaceous, especially graphite-like bodies for use in nuclear reactors 
and as casting molds, without the use of pressure and with high structural 
strength. 
It is also an object to advance the principles set forth in the 
above-mentioned applications. 
SUMMARY OF THE INVENTION 
These objects and others which will become apparent hereinafter are 
attained, in accordance with the present invention, in a system for 
producing graphite-like bodies (synthetic-graphite bodies) which comprises 
the steps of forming a viscous slurry of particles in a liquid medium, 
e.g. as a flowable or kneadable mass, shaping this mass to the desired 
configuration, drying the mass and thereafter cokefying the mass, the 
solids of which consist of particles of a carbonaceous filler coated with 
a carbonizable binder. The present invention starts with the assumption 
that binder-coated filler particles are available, the particles having 
been coated uniformly (e.g. as described in our application Ser. No. 
267,480 now U.S. Pat. No. 4,009,143). 
According to a feature of the invention, the proportion of the liquid in 
which the binder is soluble and which is miscible with the slurrying 
liquid, should be between 5 and 20% by volume of the liquid mixture. 
During drying, the mass, which is preferably shaped in a mold, produces a 
solid "green" body which, upon cokefying at temperatures of 800.degree. C 
and above, yields a homogeneous rigid structure of the configuration 
originally imparted to the shapable mass. The latter can be employed as a 
more or less flowable or viscous product which may be sufficently fluid to 
be cast or may be somewhat more pasty so as to be shapable by manipulative 
molding or kneading as in the case of clay. 
According to another feature of the invention, the mass includes a liquid 
phase in which the binder is only limitably soluble and swellable, the 
liquid phase, e.g. water, serves as a vehicle for shaping the particulate 
mass. Advantageously, the powder is obtained by drying the slurry of a 
binder and the aforementioned filler solids as described above. 
Preferably the filler materials, such as electrically-produced synthetic 
graphite, natural graphite, milled petroleum coke and carbon black are 
mixed with binders such as pitch, tar and phenol-formaldehyde resins by 
dissolving the binder first in a liquid in which the filler is slurried 
and then introducing this produced slurry into a carrier liquid in which 
the binder is insoluble or only partly soluble to produce an emulsion of 
the binder in the form of the coating upon the solid particles which 
settle and, after decanting of the excess liquid, form a slurry as 
described in application Ser. No. 267,480 filed 29 June 1972 (now U.S. 
Pat. No. 4,009,143) in which we are coinventors, to produce particles in 
which the solid grains are substantially uniformly coated with the binder, 
the starting point of the present invention. 
The shaped bodies produced in accordance with the present invention have an 
exceptionally high degree of homogeneity. 
Another advantage of the process according to the present invention is that 
nearly the whole porosity of the finished body is open and thus the body 
is suitable as an impregnatable structure for any purpose in which 
impregnation is desired. For example, it may be desirable to impregnate 
the body with conductive substances in order to increase the electrical 
conductivity, synthetic graphite bodies prepared with binders being 
notoriously of poor conductivity. 
It is important to note, in accordance with this invention, that the system 
obtains bodies of relatively high density and strength without the 
application of any pressure other than the self-packing or gravitational 
pressure resulting when the slurry is filled into a mold. 
We have now found that it is not necessary to press the particles into 
shape in an extrusion press, with rams or the like in order to obtain 
bodies of high density and high structural strength. Rather, the present 
invention teaches that it is possible to provide shaped bodies from such 
coated particles in a simple and economical way when the coated particles 
are slurried and are introduced as a wet or moist mass, as a slurry, into 
forms or molds and only then dried. It is indeed surprising that the 
slurrying of the particles into the mold, without application of pressure, 
can give rise to bodies which upon cokefication, form bodies equal to 
those produced under elevated pressures. 
According to a feature of the invention, the proportion of the liquid in 
which the binder is soluble and which is miscible with the slurrying 
liquid should be between 5 and 20% by volume of the liquid mixture.

SPECIFIC DESCRIPTION 
A slurry receptacle or vessel 52, is selectively supplied with a slurry 
through a line 60 from a process corresponding to that described in 
application Ser. No. 267,480 (U.S. Pat. No. 4,009,143), or a slurry from a 
vessel 50 in which a dry binder-coated powder is mixed with a liquid 
containing a solvent in which the binder is partially soluble, delivered 
by line 51, the slurry being introduced into a porous-wall form 53. 
Preferably the liquid phase of the slurry is water containing 5 to 20 
volume percent methanol. In the form 53, the slurry is settled by a 
vibrator 54, the excess liquid draining through the walls or being 
decanted, the contents of the mold being then degassed by heating it to a 
temperature of 70.degree. C. 
As represented at 54'. the liquid phase is removed and the mold or form 
containing the particles from which the liquid has been removed is 
introduced into a drying and hardening oven 55 and then introduced into a 
furnace 56 where coking occurs as described in CARBON AND GRAPHITE 
HANDBOOK, CHAS. L. MANTELL. INTERSCIENCE PUBLISHERS, NEW YORK, 1968. The 
product is removed from the mold and constitutes the desired graphite 
body. 
SPECIFIC EXAMPLES 
EXAMPLE I 
100 Grams of a slurry formed in accordance with the method of application 
Ser. No. 267,480 (now U.S. Pat. No. 4,009,143), is filled into a form with 
porous walls capable of allowing the degassing of the slurry. The 
proportion of binder in the slurry amounted to 40% by weight. After 
vibration and heating to 70.degree. C, the solids of the slurry were 
separated from the liquid phase. The resulting mass was then dried at 
150.degree. C and coked at a temperature of 800.degree. C. 
EXAMPLE II 
75 Grams of a dry slurry produced by the method described in application 
Ser. No. 267,480 (now U.S. Pat. No. 4,009,143) are made into a pasty mass 
by the addition of 15 volume percent of methanol containing water. The 
paste is thoroughly blended and shaped in a mold having walls permeable to 
gas without pressure and thereafter the mold is heated to 70.degree. C. In 
the mold the mass is setting up from the liquid phase and the body in the 
mold is then dried at about 105.degree. C and is then coked at a 
temperature above 800.degree. C. Cokefication is completed when the 
volatile components of heating of the phenol-formaldehyde resin are no 
longer given off. (Cokefication was carried out as described in Carbon and 
graphite Handbook, Charles L. Mantell, Intersicent Publishers, New York, 
1968). The body is found to have a homogeneous structure, high mechanical 
strength and faithful conformity to the mold.