Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/042—Electrodes formed of a single material
  • C25B11/043—Carbon, e.g. diamond or graphene
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
  • C04B35/528—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
  • C04B35/528—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components
  • C04B35/532—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components containing a carbonisable binder

Definitions

• the method includes a further step of heating the dried article in an oxidizing atmosphere to 260300 C. at a heating rate of 0.2-3 C./ min. prior to the carbonization step.
• a further step of graphitising is also disclosed.
• This invention relates to the production of formed articles of carbon and more particularly to a new method for producing formed carbon articles by magmatic casting (similar to slurry casting or slip casting in ceramics and hereinafter referred to as slurry casting).
• moulding and extruding are practiced as methods for forming formed carbon articles, suitable blends of coke as an aggregate and pitches as binders or bonding agents being used as starting materials.
• suitable blends of coke as an aggregate and pitches as binders or bonding agents being used as starting materials.
• Examples of products thus produced are electrodes, refractory materials, electrical brushes, and various carbon tubes and plpes.
• Another object of the invention is to provide a method for producing formed articles of carbon in which the porosity, density, hardness, and other properties of the formed articles after baking can be readily controlled as desired.
• Still another object of the invention is to provide a method as stated above which is applicable to the production of a wide range of formed articles, including articles of thin thicknesses as small as 1.0 mm.
• a method of the above stated character which is characterised by the steps of preparing a slurry containing as its principal carbon material a modified pitch of a softening point above degrees C. prepared by treatment of coal tar pitches, petroleum asphalts, and other pitch-like substances resulting as industrial byproducts, casting this slurry into a formed article, drying the article, then heating the same in an oxidising atmosphere if necessary, then carbonising the article in an inert gas, and graphitising the same if necessary.
• modified pitches is herein used to include collectively pitches of softening temperatures above 170 degrees C., preferably above 200 degrees C. These modified pitches are prepared by subjecting coal tar pitches, petroleum asphalts, and other pitch-like substances resulting as industrial byproducts to heat treatment, extraction by solvent, and treatment with various substances such as ozone, oxygen, oxides of nitrogen halogens, sulphur, and sulphur compounds. In some cases, pitches having functional groups of high thermal reactivity such as halogens and/or oxygen-containing groups are included in the modified pitches as referred to hereinabove.
• the temperature herein referred to as the softening temperature is that at which sample powder particles of a diametric size of the order of 0.1 mm. within a sealed tube in a micro melting point apparatus melt and assume a spherical shape.
• modified pitches stable slurries can be very easily made by ball milling or some other process.
• the specific gravities of these pitches are lower than those of ceramic starting materials.
• these pitches when they are subjected to baking process after being formed into a desired shape can be rendered by heating in air to a temperature of from 260 to 300 degrees C. at a temperature rise rate of the order of from 0.2 to 3 degrees C./min. into a state, wherein the pitches can fully with stand carbonisation and graphitisation treatment in an inert gas phase as a temperature higher than the above mentioned temperature without exhibiting any definite melting or deformation.
• modified pitches can be readily prepared to have different softening points by various treatment processes.
• the preferable processes are dry distillation, oxidation, and chlorine treatment.
• the preferable processes are dry distillation, oxidation, and chlorine treatment.
• oxygen in a quantity of the order of 25 percent can be easily introduced into a pitch to improve the thermal reactivity thereof.
• a pitch in powder form in an atmosphere of chlorine By slowly heating a pitch in powder form in an atmosphere of chlorine and thus treating the pitch at temperatures up to 250 degrees C. to cause it to contain chlorine, a modified pitch having a softening point above 150 degrees C. and no clearly discernible melting point can be readily produced.
• the value of the softening point of a modified pitch for slurry preparation has a great influence on the porosity and hardness of the formed article after baking. According to results I have so far obtained, a minimum value of 8 percent and a maximum value of 65 percent can be obtained for porosity by water immersion, and there is a possibility of extending even further the limits of this range.
• a slurry suitable for the method of the invention may be composed, of course, of only water and a modified pitch
• additives such as an alcohol for improving the wetness of the modified pitch during ball milling
• additives such as emulsions of phenolic and other thermosetting resins, water glass, and phosphoric acid or salts thereof is highly effective in increasing the strength of the product after baking.
• mixtures such as mixtures of modified pitches which do not exhibit softening points and modified pitches of low softening points and mixtures of modified pitches of low softening points and carbon in a fine powder form as, for example, colloidal graphite, carbon black, and raw coke powder can also be used.
• modified pitches and other carbon materials can be ground most readily by wet grinding, and a fully stable slurry can be produced in a time of the order of three hours by ball milling. I have carried out long-period grinding and mixing up to 50 hours without any particularly deleterious effect on the characteristics of the products.
• slurry concentration is an important factor determining the rate of success in casting and thickness of the objective formed articles, I have found that a practical concentration by weight is in the range of from to 50 percent and that a concentration particularly of from to percent facilities the practice of the method of the invention.
• the shapes of the carbon articles which can be formed by this method range widely from simple shapes such as sheets and plates, bars, tubes, and crucibles to complicated shapes such as those vessels made in split moulds and asymmetrical vessels. Thin articles of thickness of the order of 1.0 mm. can be readily produced.
• Example 1 500 grammes (g) of a coal-tar pitch of a softening point (hereinafter abbreviated S.P.) of degrees C. is subjected to dry distillation for 60 minutes at 400 degrees C. as air is blown thereagainst. The resulting residue is heated in powder form in air to 200 degrees C. to prepare a modified pitch of an S.P. of from 198 to 210 degrees C.
• S.P. softening point
• 25 g. of the modified pitch thus prepared is ground for 8 hours in a ball mill together with g. of water and 20 g. of ethyl alcohol thereby to prepare a slurry.
• a slurry prepared in the above described manner was cast with a pouring time of 5 seconds by means of a separately prepared gypsum plaster mould into a small crucible with a wall thickness of 3 mm. After thorough drying at room temperature and then at 100 degrees C., the crucible was heated in air to 300 degrees C. at a temperature rise rate of 0.2 degree C./ min. Thereafter, the crucible was heated at a rate of 5 degrees C./min. to 1,400 degrees C. in an atmosphere of nitrogen gas to carbonise the same.
• the resulting diametric shrinkage after the carbonisation process was 22 percent, and a formed article in the shape of a crucible of a porosity of 9.2 percent and a bulk specific gravity of 1.50 was obtained.
• Example 2 A pitch produced industrially as a byproduct of thermal decomposition of naphtha was subjected to dry distillation at 400 degrees C. in nitrogen gas. The resulting residue of dry distillation was ground and then heated to 200 degrees C. in chlorine gas, whereupon a modified pitch containing approximately 10 percent of chlorine and having a softening point of 250 degrees C. was obtained.
• the slurry thus prepared was cast into a small evaporating dish of a thickness of approximately 1.2 mm. with a pouring time of 3 seconds by means of a gypsum plaster mould.
• the evaporating dish was baked to a temperature of 1,400 degrees C. under conditions similar to those of Example 1.
• Example 3 500 g. of a coal-tar pitch (S.P. 85 degrees C.) was heated to 460 degrees C. at a rate of 3 degrees C./min. as nitrogen gas was blown thereagainst. The resulting residue was ground and then subjected to ozone oxidation at room temperature for 10 hours and thereafter to air oxidation up to a temperature of 200 degrees C., whereupon a modified pitch containing 20 percent of oxygen and exhibiting no softening point up to 360 degrees C. was obtained. This modified pitch was used to prepare a slurry in the same manner as set forth in Example 1.
• a coal-tar pitch S.P. 85 degrees C.
• the slurry thus prepared was cast into a pot of a height of approximately 6 cm. and a thickness of approximately 3 mm. by means of a gypsum plaster mould with a pouring time of 5 seconds. After thorough drying, the cast pot was heated to 220 degrees C. at a rate of 2 degrees C./ min. in nitrogen gas and then to 1,400 degrees C. at a rate of 5 degrees C./min. thereby to carbonise the same.
• a method of producing formed articles of carbon which comprises: preparing a slurry having 5 to 50 per cent by weight solids content by ball milling an admixture containing as the principal carbon starting material thereof a pitch having a softening point higher than 170 degrees C., water, and 50 to 80 percent by weight, based on the weight of pitch in the slurry, of ethyl alcohol; forming said slurry into an article by slurry casting in a porous gypsum plaster mold; drying said article thus formed; and carbonizing the article in an inert gas phase; said method being further characterized, when the softening point of the pitch is lower than 300 degrees C., by the additional step of heating the article in an oxidizing atmosphere to a temperature of from 260 to 300 degrees C. at a temperature rise rate of the order of from 0.2 to 3 degrees C./ min. prior to the carbonization step.

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Cited By (10)

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• 1965
  • 1965-07-13 SE SE9227/65A patent/SE307704B/xx unknown
• 1969
  • 1969-01-27 US US794361*A patent/US3565980A/en not_active Expired - Lifetime
  • 1969-01-30 DE DE1904381A patent/DE1904381C3/de not_active Expired
  • 1969-01-30 FR FR6901971A patent/FR2001049A1/fr not_active Withdrawn
  • 1969-01-31 SU SU1302096A patent/SU413667A3/ru active
  • 1969-01-31 GB GB5316/69A patent/GB1248507A/en not_active Expired

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