EP0084059A1 - Composite of tib2-graphite - Google Patents
Composite of tib2-graphiteInfo
- Publication number
- EP0084059A1 EP0084059A1 EP82902609A EP82902609A EP0084059A1 EP 0084059 A1 EP0084059 A1 EP 0084059A1 EP 82902609 A EP82902609 A EP 82902609A EP 82902609 A EP82902609 A EP 82902609A EP 0084059 A1 EP0084059 A1 EP 0084059A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- article
- tib
- temperature
- dispersion
- carbon
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 239000002131 composite material Substances 0.000 title claims abstract description 36
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 18
- 239000010439 graphite Substances 0.000 title claims abstract description 18
- 229910033181 TiB2 Inorganic materials 0.000 claims abstract description 60
- QYEXBYZXHDUPRC-UHFFFAOYSA-N B#[Ti]#B Chemical compound B#[Ti]#B QYEXBYZXHDUPRC-UHFFFAOYSA-N 0.000 claims abstract description 51
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 43
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 41
- 239000006185 dispersion Substances 0.000 claims abstract description 40
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000011230 binding agent Substances 0.000 claims abstract description 25
- 239000006229 carbon black Substances 0.000 claims abstract description 21
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 17
- 150000001639 boron compounds Chemical class 0.000 claims abstract description 16
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000002156 mixing Methods 0.000 claims abstract description 11
- 239000004033 plastic Substances 0.000 claims abstract description 11
- 238000000465 moulding Methods 0.000 claims abstract description 6
- 238000001125 extrusion Methods 0.000 claims abstract description 4
- 238000005087 graphitization Methods 0.000 claims abstract 2
- 238000000034 method Methods 0.000 claims description 53
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 claims description 44
- 238000006243 chemical reaction Methods 0.000 claims description 31
- 239000000203 mixture Substances 0.000 claims description 31
- 238000010438 heat treatment Methods 0.000 claims description 30
- 239000000571 coke Substances 0.000 claims description 27
- 239000002245 particle Substances 0.000 claims description 22
- 239000011301 petroleum pitch Substances 0.000 claims description 22
- 239000011295 pitch Substances 0.000 claims description 22
- 230000000630 rising effect Effects 0.000 claims description 19
- 239000000376 reactant Substances 0.000 claims description 17
- 238000005470 impregnation Methods 0.000 claims description 16
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims description 14
- 239000007788 liquid Substances 0.000 claims description 14
- 239000011294 coal tar pitch Substances 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 238000002844 melting Methods 0.000 claims description 6
- 230000008018 melting Effects 0.000 claims description 6
- 238000007493 shaping process Methods 0.000 claims description 6
- 235000013312 flour Nutrition 0.000 claims description 5
- 238000010000 carbonizing Methods 0.000 claims description 4
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical compound [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 claims description 3
- 239000002008 calcined petroleum coke Substances 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 229920001971 elastomer Polymers 0.000 claims description 2
- 230000003014 reinforcing effect Effects 0.000 claims description 2
- 230000009850 completed effect Effects 0.000 claims 2
- 238000011065 in-situ storage Methods 0.000 claims 2
- 229910004844 Na2B4O7.10H2O Inorganic materials 0.000 claims 1
- 239000012300 argon atmosphere Substances 0.000 claims 1
- 238000000227 grinding Methods 0.000 claims 1
- 239000011440 grout Substances 0.000 claims 1
- PEYVWSJAZONVQK-UHFFFAOYSA-N hydroperoxy(oxo)borane Chemical compound OOB=O PEYVWSJAZONVQK-UHFFFAOYSA-N 0.000 claims 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 claims 1
- 239000002006 petroleum coke Substances 0.000 abstract description 4
- 238000005755 formation reaction Methods 0.000 abstract 1
- 210000004027 cell Anatomy 0.000 description 17
- INAHAJYZKVIDIZ-UHFFFAOYSA-N boron carbide Chemical compound B12B3B4C32B41 INAHAJYZKVIDIZ-UHFFFAOYSA-N 0.000 description 10
- 229910052580 B4C Inorganic materials 0.000 description 9
- 239000000463 material Substances 0.000 description 6
- 239000011159 matrix material Substances 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 229910003481 amorphous carbon Inorganic materials 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910001610 cryolite Inorganic materials 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 229910021538 borax Inorganic materials 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 239000011329 calcined coke Substances 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- -1 however Substances 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 239000005011 phenolic resin Substances 0.000 description 2
- 229920001568 phenolic resin Polymers 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000004328 sodium tetraborate Substances 0.000 description 2
- 235000010339 sodium tetraborate Nutrition 0.000 description 2
- 229910052715 tantalum Inorganic materials 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 230000008016 vaporization Effects 0.000 description 2
- 238000009736 wetting Methods 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229920001732 Lignosulfonate Polymers 0.000 description 1
- 229910004835 Na2B4O7 Inorganic materials 0.000 description 1
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- RQMIWLMVTCKXAQ-UHFFFAOYSA-N [AlH3].[C] Chemical compound [AlH3].[C] RQMIWLMVTCKXAQ-UHFFFAOYSA-N 0.000 description 1
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 1
- 239000003830 anthracite Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000011305 binder pitch Substances 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 150000001642 boronic acid derivatives Chemical class 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000011336 carbonized pitch Substances 0.000 description 1
- 210000002421 cell wall Anatomy 0.000 description 1
- 239000003610 charcoal Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- UQGFMSUEHSUPRD-UHFFFAOYSA-N disodium;3,7-dioxido-2,4,6,8,9-pentaoxa-1,3,5,7-tetraborabicyclo[3.3.1]nonane Chemical compound [Na+].[Na+].O1B([O-])OB2OB([O-])OB1O2 UQGFMSUEHSUPRD-UHFFFAOYSA-N 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000010952 in-situ formation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000002045 lasting effect Effects 0.000 description 1
- 229920005610 lignin Polymers 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 239000011331 needle coke Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 238000005580 one pot reaction Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000013618 particulate matter Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 239000006253 pitch coke Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 239000003039 volatile agent Substances 0.000 description 1
Classifications
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- 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
- C04B35/58—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 borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/5805—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 borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on borides
- C04B35/58064—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 borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on borides based on refractory borides
- C04B35/58071—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 borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on borides based on refractory borides based on titanium borides
-
- 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
-
- 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
-
- 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
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/64—Burning or sintering processes
-
- 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
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/64—Burning or sintering processes
- C04B35/645—Pressure sintering
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
Definitions
- Aluminum metal has been produced for 90 years in the Hall cell by electrolysis of alumina in a molten cryolite salt electrolyte bath operating at temperatures in the range of 900o-1000oC.
- the reactivity of the molten cryolite, the need for excellent electrical conductivity, and cost considerations have limited the choice of materials for the electrodes and cell walls to the various allotropic forms of carbon.
- the Hall cell is a shallow vessel, with the floor forming the cathode, the side walls being a rammed coke-pitch mixture, and the anode being a block suspended in the bath at an anode-cathode separation of a few centimeters.
- the anode is typically formed from a pitch-calcined petroleum coke blend, prebaked to form a monolithic block of amorphous carbon.
- the cathode is typically formed from a pre-baked, pitch-calcined anthracite or coke blend, with cast-in-place iron over steel bar electrical conductors in grooves in the bottom side of the cathode.
- the ancde-cathode spacing is usually about 4-5 cm., and attempts to lower this distance result in an electrical discharge from the cathode to the anode through aluminum droplets suspended in the bath.
- the molten aluminum is present as a pad in the cell, but is not a quiescent pool due to the factors of preferential wetting of the carbon cathode surface by the cryolite melt in relation to the molten aluminum, causing the aluminum to form droplets, and the erratic movements of the molten aluzd-num from the strong electromagnetic forces generated by the high current density.
- the wetting of a solid surface in contact with two immiscible liquids is a function of the surface free energy of the three surfaces, in which the carbon cathode is a low energy surface and consequently is not readily wet by the liquid aluminum.
- the angle of a droplet of aluminum at the cryolite-aluminum-carbon junction is governed by the relationship where ⁇ 12 , ⁇ 13 , and ⁇ 23 are the surface free energies at the aluminum carbon, cryolite-carbon, and cryolite-aluminu ⁇ a boundaries, respectively.
- the cathode were a high energy surface, such as would occur if it were a ceramic instead of carbon, it would have a higher contact angle and better wettability with the liquid aluminum. This in turn would tend to smooth out the surface of the liquid aluminum pool and lessen the possibility of interelectrode discharge allowing the anode-cathode distance to be lowered and the thermodynamic efficiency of the cell improved, by decreasing the voltage drop through the bath.
- amorphous carbon is a low energy surface, but also is quite durable, lasting for several years duration as a cathode, and relatively inexpensive.
- a cathode or a cathode component such as a TiB 2 stud which has better wettability and would permit closer anode-cathode spacing could improve the thermodynamic efficiency and be very cost-effective.
- Titanium Diboride TiB 2 has been proposed for use as a cathodic element in Hall cells, giving an improved performance oyer the amorphous carbon and semi-graphite cathodes presently used. It had previously been known that Titanium Diboride (TiB 2 ) was useful as a cathode component in the electrolytic production of aluminum, when retrofitted in the Hall cell as a replacement for the carbon or semi-graphite form.
- the electrical efficiency of the cell was improved due to better conductivity, due mainly to a closer anodecathode spacing; and the corrosion resistance was improyed, probably due to increased hardness, chemical inertness and lower solubility as compared to the carbon and graphite fonts.
- TiB 2 -carbon composite which shows excellent performance as a cathode or cathode component in Hall aluminum cells.
- the method is markedly more economical, and also produces an unexpectedly improved cathode when its performance is compared to the traditional carbonaceous material.
- the method involyes the use of a titania (TiO 2 ) -graphite composite structure as a starting material. TiO 2 is dispersed in the mixture of coke particles and flour, then wetted and dispersed in a carbonizable liquid binder to form a plastic mass.
- the binder is preferably a coal tar pitch, however, petroleum pitches, phenolic resins, lignin sulfonate, and other carbonizable binders may also be used.
- the coke particles most useful are selected size ranges of calcined delayed petroleum coke, made by heating a heavy hydrocarbon fraction to about 500o-510oC and holding the material in a coker drum for about 18 hours, while taking the gas oils vaporizing off to a combination tower for separation and recycling. The solid coke re-sidue remaining is removed, xihen calcined at approximately 1200o-1300oC to form the calcined coke useful in Hall cell electrodes or electrode components, and for conversion to graphite.
- Regular coke is isotropic with a coefficient of thermal expansion (CTE) characteristic of from 10 to 30 x 10 -7 cm/cm/oC, over the range of 0o to 50oC, relatively uniform on all 3 geometric axes in physical properties, while an acicular or needle coke will generally be anisotropic having a CTE characteristic which is variant on the axes and less than 10 x 10 -7 cm/cm/oC on the principal axis.
- Coke flour may also be included, using a particle size range with about 50% passing a 79 mesh/cm (200 mesh per in.) screen.
- the filler carbon in the original formed article may also be obtained from other common sources, such as pitch coke, charcoal and metallurgical cokes from coal, with a mean particle diameter of about 3 mm being preferable, ana a high surface area/wt. ratio.
- the plastic mass is then molded or extruded to form the desired shape and baked on a cycle rising to 700o-1100oC oyer a period of 1 to 10 days to carbonize the binder, forming a solid C-TiO 2 composite.
- the baked carbon-TiO 2 composite shape produced is a structure containing TiO 2 and particulate carbon firmly bound in the matrix of carbonized pitch.
- the structure is highly porous due to the inherent porosity of the coke, incomplete packing, and the volatilization of about 30-40% of the initial weight of the pitch, and is specially formulated for high porosity.
- the baked composite shape is then impregnated in a pressure vessel under alternate cycles of vacuum and about 7 x 10 3 Pa (100 PSI) pressure with a boron compound alor.e or with a dispersion of B 2 O 3 and carbon black or other micronized carbon in H 2 O.
- a boron compound alor.e or with a dispersion of B 2 O 3 and carbon black or other micronized carbon in H 2 O Either B 2 O 3 or H 3 BO 3 may be used as B 2 O 3 is hydrolyzec to H 3 BO 3 in H 2 O by the reaction:
- the article may be impregnated with molten B 2 O 3 or boric acid or with a oarbcn black dispersion in a molten boron compound.
- a further modificaticn of the above procedure consists of mixing stoichiometric amounts of TiO 2 , carbon black and B 2 O 3 , heating the mixture to melt the B 2 O 3 , dispersing the TiO 2 and carbon in the molten B 2 O 3 , cooling, allowing the paste to harden to a solid, milling the solid to a powder, dispersing the powder in a binder, then using this dispersion as an impregnant.
- the boron compound ana carbon black may be dispersed in a molten pitch or other carbonizable binder such as a petroleum pitch with a 110o- 120°C softening point, and the resulting dispersion used as an impregnant.
- a molten pitch or other carbonizable binder such as a petroleum pitch with a 110o- 120°C softening point
- Each impregnating cycle will nomally require a bake to the 700o-1100oC range, carbonizing the binder.
- the process may also be used by mixing boron carbide (B 4 C) with coke particles and binder in the initial mix, baking, then impregnating the resulting baked piece with a TiO 2 -carbon black dispersion in a carbonizable binder.
- B 4 C boron carbide
- the unique aspect of the process provides a method whereby TiB 2 is formed during subsequent heat treatment to a temperature above 2000oC, while the carbon is being made graphitic.
- the carbon black or similar finely divided carbon acts as the reductant to minimize consumption of the article matrix during the reaction of TiO 2 and B 2 O 3 to form TiB 2 .
- the article After drying, the article is heated to the reaction temperature for the formation of TiB 2 , in the range of 1200o-1800oC.
- the reaction starts to take place at about 800oC but is quite slow below 1200oC and reaches a high reaction rate at about 1750oC.
- the heat treatment may be done in stages, with re-impregnation and reheating cycles to build up the desired concentration of TiB 2 . Due to the loss of the carbon black ana possibly a portion of the binder and coke as CO during the TiB 2 forming reaction, the article may develop excess porosity and consequently have low strength and be poor in other physical properties.
- a carbonizable binder preferably a petroleum pitch with a softening point in the 110o-123 range, although lignin sulfo ⁇ ate, phenolic resins and other pitches may be used, under about
- the article After impregnation, the article is again heated to the 600o to 1100oC range over a period of 2 to 10 days to carbonize the pitch, sealing the surface and strengthening the article.
- the last step in the process will generally include heating the article to 2000oC or higher, converting the carbon to the graphitic form.
- the temperature range preferred is about 2400o- 2500oC, although for particular processes any point in the 2000o- 3000o range may be used.
- a cathode shape is made by mixing coke particles with a mean diameter of 3 mm, coal tar pitch having a softening point of approximately 110o-120oC and TiO 2 in a high-shear heated mixer. The mix is heated to approximately 175 oand the coke and TiO 2 are well dispersed in the molten pitch.
- the cathodic element is molded at about 14 x 10 6
- Pa (2000 PSI) pressure then baked on a cycle rising to 720o in six days. After removal from the oven the shape is placed in an autoclave and impregnated with a dispersion of a rubber reinforcing grade of carbon black and B 2 O 3 in H 2 O, then removed and dried slowly to vaporize the H 2 O without loss of B 2 O 3 . The piece is next heated to 1500oC, at which temperature the TiO 2 and B 2 O 3 react, releasing CO. These gas-producing steps are carried out slowly in order to avoid fissuring due to too rapid gas evolution.
- the piece is then re-impregnated, using a petroleum pitch with a softening point of from 110o-120oC, baked to carbonize the pitch on a six day cycle, the temperature rising to 720oC, which fills the porosity left by theTiB 2 forming reaction, then graphitized by heating to 2400oC.
- a mixture is prepared haying the following composition: B 2 O 3 38 wt. %
- a conventional carbon body which has a high pore volume and is well suited for impregnation, is made from the following composition, by wt. :
- Example 4 The mix is blended, shaped and baked as in Example 1. The article is then impregnated under cycles cf vacuum and pressure above the melting point of B 2 O 3 with the mix prepared in Example 2, heated slowly to a TiB forming temperature above 1200oC, preferably 1750 , held at that temperature for one to four hours, cooled and impregnated with the same petroleum pitch under alternate cycles of vacuum and pressure as above, re-baked as above, and heat treated to a temperature of 2100o or higher.
- Example 4 Example 4
- a cathode shape is formed from pitch, coke, and TiO 2 and baked as in Example 1. It is then impregnated with a dispersion of carbon black in molten B 2 O 3 at 7 x 10 3 Pa (100 PSI). After impregnation, it is heated to 1500 for one hour to form TiB 2 , then cooled, impregnated with petroleum pitch under cycles of vacuum and 7 x 10 3 Pa at 250°C, re-baked for six days, the temperature reaching 720oC, then graphitized by heating to 2300°C.
- Example 5 A mixture is prepared having the following composition:
- a cathodic element for a Hall cell is formed by molding the dispersion trader about 1.4 x 10 7 Pa (2000 PSI) and baked on a cycle rising to about 800oC in six days. After cooling to ambient temperature, the element is impregnated with a dispersion of 30% TiO 2 by wt. (ceramic pigment grade) in petroleum pitch (S.P. 110o- 120°C) at 240°C under alternate cycles of vacuum and 6.9 x 10 5 Pa (100 PSI) pressure.
- Blends of the following dry ingredients are mixed in parts by wt. :
- Theoretical % TiB 2 in composite 1 2 8% 57% 79% 77% 1Assuming a 75-80% coke yield from the pitch during the bake cycle from ambient to 700o-1100oC. 2Assuming complete conversion of TiO 2 to TiB 2 .
- TheTiO 2 and coke are charged into a sigma type mixer heated to about 160°-175°C and thoroughly blended while being heated. When the dry blend has reached about 160oC, the pitch is added, melted, and the solid ingredients wetted by the molten pitch. After thorough mixing, the plastic mass is cooled and molded to the desired shape of the article.
- the article is baked on a slowly rising temperature cycle, reaching 720°C in a period of 6 days, and removed from the furnace and cooled. After re-heating to about 500°C, the article, at that temperature or higher, is impregnated with moltenB 2 O 3 , under 6.9 x 10 5 Pa pressure to a final pickup of sufficient boron-containing material to form the surface layer of TiB on further heat treatment.
- the TiO 2 -C composites of Example 6 are prepared and impregnated with molten H 3 BO 3 instead of B 2 O 3 , and further treated as in the Example.
- the TiO 2 -C composites of Example 6 are prepared and impregnated with a water solution of B 2 O 3 .
- B 2 O 3 is hydrated to H 3 BO 3 in water and thus the two are interchangeable.
- the article is impregnated under 1.7-6.9 x 10 5 Pa of pressure, dried at about 100oC, heat treated @ 1200o-2000oC and the process repeated to build up the desired amount of B compound in the structure of the article.
- Heat drives the reaction of TiO 2 and H 3 BO 3 , forming TiB by the overall reaction: TiO 2 + 2 H 3 BO 3 + 5 C ⁇ TiB 2 + 3 H 2 O + 5 CO.
- the article may be re-impregnated and re-baked to produce the TiB 2 -carbon composite, but if aTiB 2 -graphite composite is the desired end product, the article is further heated to 2200oC or higher, which temperature will convert the amorphous C to semigraphite or graphite.
- a re-impregnation under alternate cycles of vacuum and pressure step with pitch or a dispersion of TiO 2 or boron compound or with a mixture of both of the reactants (TiO 2 and a boron cog ⁇ pound) dispersed in a liquid carbonizable binder or impregnant may be used to seal this remaining porosity and densify the article.
- The. preferred impregnant is a petroleum pitch having a melting point in the 100o-120oC range used at about 165°-250°C.
- B 4 C (10 g) is dispersed with calcined delayed petroleum coke particles (90 g) having a mean diameter of 3 mm in a sigma mixer and heated to about 170oC, coal tar pitch (25 g) with a softening point of 110oC is added, and melted, and a plastic dispersion is formed.
- a cathodic element is molded under about 1.4 x 10 7 Pa (2000 PSI), baked on a cycle with the temperature rising to 800oC in six days. After baking, the element is cooled, then impregnated with a dispersion of TiO in petroleum pitch (30% by wt.) at 240°C with 6.9 x 10 5 Pa (100 PSI).
- the impregnation step is repeated with alternate vacuum and pressure cycles. After impregnation, the element is heated to 720oC over a six day period, then cooled. The impregnation-bake cycle is repeated several times to build up the requiredTiO 2 concentration firmly bound in the carbon matrix in the pore volume of the element. After baking, the element is further heated to 1750oC, which converts the reactants to TiB 2 . The reaction produces CO as shown, and to seal porosity resulting from the loss of C from the matrix, the element is impregnated with petroleum pitch and baked as above to seal the porosity and strengthen the structure.
- the element may be re-impregnated with the TiO 2 dispersion, baked, and re-heated as above. After heating to 1750oC, to form TiB 2 , the element is further heated to 2250oC to convert the carbon matrix to graphite.
- the final cathodic element has TiB 2 concentrated primarily on or near the surface.
- the process disclosed uses the reactions forming TiB 2 from TiO 2 , and B 4 C, B 2 O 3 , or other boron compounds to form a TiB 2 -graphite composite.
- the process may also be used to form other such composite structures from reactants forming refractory materials.
- the reactions are as follows:
- the process is in general the generalized reaction taking place at temperatures in the range of 800o-3000oC of: MO + B 2 O 3 + C ⁇ MB + CO (where M is a metal) or MO + B 4 C + C ⁇ MB + CO or MO + N + C ⁇ MN + CO (where N is a non-metal)
- EXAMPLE 10 The article of Example 6, after baking, is impregnated with a dispersion of B 4 C in petroleum pitch with a softening point of 110o- 120oC, at 240oC under several cycles of vacuum and pressure of 6.9 x 10 5 Pa (100 PSI). After impregnation, the article is re-baked as above, then further heated to 1750oC to drive the TiB 2 -forming reaction to completion, re-impregnated with petroleum pitch and re-baked, then heated to 2250oC to form the graphite-TiB 2 composite.
- the process is useful for the formation of a large number of composite structures containing the end product of a reaction occurring at high temperatures in the presence of carbon, whether it enters the reaction or not.
- the reaction may occur with a number of boron compounds including borax and borates, however B 2 O 3 and H 3 BO 3 are the most economical and available compounds.
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Abstract
Des articles composites en graphite et diborure de titane sont produits en mélangeant du TiO2, du coke de pétrole et un liant pour former une dispersion plastique. Des articles sont façonnés par moulage ou extrusion et sont cuits pour carboniser le liant et former un composite TiO2-carbone cuit. L'article est imprégné avec un composé de bore fondu ou dispersé, ou avec un composé de bore mélangé avec du noir de charbon, puis chauffé pour produire une réaction de formation de TiB2. L'article est encore chauffé jusqu'à une température de graphitisation pour former un composite de graphite-TiB2 utile comme composant cathodique dans une cellule de Hall de réduction d'aluminium.Composite articles of graphite and titanium diboride are produced by mixing TiO2, petroleum coke and a binder to form a plastic dispersion. Articles are shaped by molding or extrusion and are baked to carbonize the binder and form a baked TiO2-carbon composite. The article is impregnated with a molten or dispersed boron compound, or with a boron compound mixed with carbon black and then heated to produce a TiB2 formation reaction. The article is further heated to a graphitization temperature to form a graphite-TiB2 composite useful as a cathode component in an aluminum reduction Hall cell.
Description
Claims
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/287,129 US4465581A (en) | 1981-07-27 | 1981-07-27 | Composite of TiB2 -graphite |
US06/287,124 US4439382A (en) | 1981-07-27 | 1981-07-27 | Titanium diboride-graphite composites |
US287124 | 1988-12-20 | ||
US287129 | 1994-08-08 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0084059A1 true EP0084059A1 (en) | 1983-07-27 |
EP0084059A4 EP0084059A4 (en) | 1984-05-17 |
Family
ID=26964271
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19820902609 Withdrawn EP0084059A4 (en) | 1981-07-27 | 1982-07-22 | Composite of tib2-graphite. |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0084059A4 (en) |
JP (1) | JPS58501173A (en) |
BR (1) | BR8207804A (en) |
WO (1) | WO1983000347A1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CH654031A5 (en) * | 1983-02-10 | 1986-01-31 | Alusuisse | METHOD FOR PRODUCING SOLID CATHODES. |
WO1994028201A1 (en) * | 1993-05-24 | 1994-12-08 | Maloe Nauchno-Proizvodstvennoe Predpriyatie 'mms' | Process for producing an aluminium-strontium alloy |
CN1195900C (en) | 1998-11-17 | 2005-04-06 | 艾尔坎国际有限公司 | Wettable and erosion/oxidation-resistant carbon-composite materials |
WO2003006373A1 (en) * | 2001-07-09 | 2003-01-23 | Showa Denko K.K. | Graphite fine powder, and production method and use thereof |
JP5554117B2 (en) * | 2010-03-30 | 2014-07-23 | 日本電極株式会社 | Cathode carbon block for aluminum refining and method for producing the same |
CN102660757B (en) * | 2012-05-23 | 2015-01-21 | 深圳市新星轻合金材料股份有限公司 | Preparation technology for inert anode material or inert cathode coating material for aluminum electrolysis |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3351428A (en) * | 1962-01-29 | 1967-11-07 | Kaiser Aluminium Chem Corp | Process for the production of refractory hard metal materials |
US3676371A (en) * | 1969-01-30 | 1972-07-11 | Conradty Fa C | High output electrode with stabilized electric arc |
WO1982001018A1 (en) * | 1980-09-11 | 1982-04-01 | Lakes Carbon Corp Great | Titanium diboride-graphite composites |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3314876A (en) * | 1960-11-28 | 1967-04-18 | British Aluminium Co Ltd | Method for manufacturing solid current conducting elements |
DE1251962B (en) * | 1963-11-21 | 1967-10-12 | The British Aluminium Company Limited, London | Cathode for an electrolytic cell for the production of aluminum and process for the production of the same |
-
1982
- 1982-07-22 BR BR8207804A patent/BR8207804A/en unknown
- 1982-07-22 JP JP50262682A patent/JPS58501173A/en active Pending
- 1982-07-22 WO PCT/US1982/001003 patent/WO1983000347A1/en not_active Application Discontinuation
- 1982-07-22 EP EP19820902609 patent/EP0084059A4/en not_active Withdrawn
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3351428A (en) * | 1962-01-29 | 1967-11-07 | Kaiser Aluminium Chem Corp | Process for the production of refractory hard metal materials |
US3676371A (en) * | 1969-01-30 | 1972-07-11 | Conradty Fa C | High output electrode with stabilized electric arc |
WO1982001018A1 (en) * | 1980-09-11 | 1982-04-01 | Lakes Carbon Corp Great | Titanium diboride-graphite composites |
Non-Patent Citations (1)
Title |
---|
See also references of WO8300347A1 * |
Also Published As
Publication number | Publication date |
---|---|
BR8207804A (en) | 1983-07-19 |
JPS58501173A (en) | 1983-07-21 |
WO1983000347A1 (en) | 1983-02-03 |
EP0084059A4 (en) | 1984-05-17 |
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