# US 4,396,482 A · Composite cathode > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,396,482 A - Document ID: US4396482A - Status: Granted - Kind: A - Application number: 06/307,374 - Filed: 1981-10-01 - Granted: 1983-08-02 - Earliest claimed: 1980-07-21 - Assignees: Aluminum Company of America - Inventors: Subodh K. Das; Perry A. Foster, Jr.; Gregory J. Hildeman - Web page: https://patentgrep.com/patent/US4396482A ## CPC - C04B 35/6303: {Inorganic additives} - C04B 35/56: based on carbides {or oxycarbides (containing free metal binder C22C29/00)} - C04B 35/58: based on borides, nitrides, {i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides} or silicides {(containing free binder metal C22C29/00)} - C04B 35/5805: {based on borides} - C04B 35/58071: {based on titanium borides} - C04B 35/58078: {based on zirconium or hafnium borides} - C04B 35/58085: {based on silicides} - C04B 41/5053: {non-oxide ceramics (carbon or carbonisable materials C04B41/5001)} - C04B 41/5133: {with a composition mainly composed of one or more of the refractory metals} - C04B 41/87: Ceramics - C04B 41/88: Metals - C25C 3/08: Cell construction, e.g. bottoms, walls, cathodes - C04B 2235/666: Applying a current during sintering, e.g. plasma sintering [SPS], electrical resistance heating or pulse electric current sintering [PECS] - C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE - C25C: PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR ## Abstract An improved electrolytic cell is provided for production of a metal such as aluminum by electrolysis of a compound of the metal in a solvent or bath such as molten salt. Electrolysis is carried out by passing a current from an anode to a cathode between which the solvent bath is situated. The cathode comprises a base cathode and cathode extension surfaces comprising graphite and at least 90% refractory hard metal such as titanium diboride. The cathode extension surfaces are produced from a mixture comprising at least 90% refractory hard metal and a carbonaceous binder with little or substantially no particulate carbonaceous material and graphitizing said mixture above 2350.degree. C. to graphitize the carbonaceous material therein to exhibit the graphitic structure. ## Claims ### Claim 1 In an electrolytic cell for the production of molten metal and including an anode and a base cathode spaced from said anode for passage of electric current therebetween through an electrolyte, and means to collect molten metal upon said base cathode, the improvement wherein one or more cathode surfaces extends outwardly from said base cathode toward said anode, said cathode surface being provided as a graphitized composite comprising graphite impregnated with at least 85% refractory hard metal and produced from a composite mixture comprising said refractory hard metal and a carbonaceous binder and graphitizing said composite mixture at a temperature of at least 2350.degree. C. in a non-oxidizing atmosphere to convert carbonaceous material therein to the graphitic structure. ### Claim 2 (depends on 1) The improvement according to claim 1 wherein said cathode base is arranged to collect in a pool molten metal produced in said cell and said extending cathode surfaces extend sufficiently from said cathode base to project through said molten metal pool into the electrolyte bath region of said cell. ### Claim 3 (depends on 2) The improvement according to claim 2 wherein said extending cathode surface includes a hollow portion adapted for holding an additional pool of molten metal. ### Claim 4 (depends on 1) The improvement according to claim 1 wherein said composite surface region is provided as an outward layer over a substantially carbonaceous core. ### Claim 5 (depends on 1) The improvement according to claim 1 wherein a plurality of such cathode surface regions extends from a cathode base toward each anode. ### Claim 6 (depends on 1) The improvement according to claim 1 wherein said electrolytic cell is a Hall-type cell suitable for producing aluminum. ### Claim 7 (depends on 1) The improvement according to claim 1 wherein said refractory hard metal is selected from the carbides, silicides, borides and nitrides of the fourth, fifth and sixth groups of the Periodic Table. ### Claim 8 (depends on 1) The improvement according to claim 1 wherein said refractory hard metal is selected from the borides of titanium and zirconium. ### Claim 9 (depends on 1) The improvement according to claim 1 wherein said refractory hard metal in said composite mixture comprises TiB.sub.2 provided in particulate form passing through a 325 mesh screen. ### Claim 10 (depends on 1) The improvement according to claim 1 wherein said composite mixture contains less than 5% particulate carbonaceous material. ### Claim 11 (depends on 1) The improvement according to claim 1 wherein said composite mixture contains less than 2% particulate carbonaceous material. ### Claim 12 (depends on 1) The improvement according to claim 1 wherein said composite mixture contains less than 1% particulate carbonaceous material. ### Claim 13 (depends on 1) The improvement according to claim 1 wherein said cathode surface contains at least 90% refractory hard metal. ### Claim 14 (depends on 1) The improvement according to claim 1 wherein said cathode surface contains over 95% refractory hard material and said composite mixture comprising said refractory hard material and said carbonaceous binder contains less than 2% particulate carbonaceous material. ### Claim 15 (depends on 14) The improvement according to claim 14 wherein substantially all of said graphite in said cathode surface is derived from said carbonaceous binder. ### Claim 16 (depends on 1) The improvement according to claim 1 wherein said graphitizing is carried out above 2400.degree. C. ### Claim 17 (depends on 1) The improvement according to claim 1 wherein said graphitizing is carried out above 2600.degree. C. ### Claim 18 (depends on 1) The improvement according to claim 1 wherein said graphitic structure exhibits an L.sub.c dimension greater than 400 A and a d.sub.002 dimension less than 3.4 A. ### Claim 19 (depends on 1) The improvement according to claim 1 wherein said graphite structure contains at least 98% refractory hard metal. ### Claim 20 In an electrolytic cell for the production of molten metal and including an anode and a base cathode spaced from said anode for passage of electric current therebetween through an electrolyte, and means to collect molten metal upon said base cathode, the improvement wherein one or more cathode surfaces extends outwardly from said base cathode toward said anode, said cathode surface being provided as a graphitized composite comprising graphite impregnated with at least 85% refractory hard metal selected from the carbides, silicides, borides and nitrides of the fourth, fifth and sixth groups of the Periodic Table and produced from a composite mixture comprising said refractory hard metal and a carbonaceous binder and graphitizing said composite mixture at a temperature of above 2400.degree. C. in a non-oxidizing atmosphere to convert carbonaceous material therein to the graphitic structure exhibiting an L.sub.c dimension greater than 400 A and a d.sub.002 dimension less than 3.4 A.