CA1069461A - Electrodes for aluminum reduction cells - Google Patents
Electrodes for aluminum reduction cellsInfo
- Publication number
- CA1069461A CA1069461A CA238,051A CA238051A CA1069461A CA 1069461 A CA1069461 A CA 1069461A CA 238051 A CA238051 A CA 238051A CA 1069461 A CA1069461 A CA 1069461A
- Authority
- CA
- Canada
- Prior art keywords
- oxide
- metal
- electronic conductive
- nb2o5
- ta2o5
- 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.)
- Expired
Links
- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 33
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 27
- 230000009467 reduction Effects 0.000 title abstract description 9
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 42
- 239000000203 mixture Substances 0.000 claims abstract description 27
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims abstract description 25
- 150000003839 salts Chemical class 0.000 claims abstract description 24
- 229910052574 oxide ceramic Inorganic materials 0.000 claims abstract description 23
- 239000011224 oxide ceramic Substances 0.000 claims abstract description 23
- 238000004519 manufacturing process Methods 0.000 claims abstract description 9
- 229910052751 metal Inorganic materials 0.000 claims description 68
- 239000002184 metal Substances 0.000 claims description 68
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Inorganic materials O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 claims description 42
- PBCFLUZVCVVTBY-UHFFFAOYSA-N tantalum pentoxide Inorganic materials O=[Ta](=O)O[Ta](=O)=O PBCFLUZVCVVTBY-UHFFFAOYSA-N 0.000 claims description 35
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 23
- 239000002131 composite material Substances 0.000 claims description 16
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 16
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 14
- 239000011135 tin Substances 0.000 claims description 13
- 229910052760 oxygen Inorganic materials 0.000 claims description 12
- 239000002585 base Substances 0.000 claims description 11
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 11
- 125000004430 oxygen atom Chemical group O* 0.000 claims description 11
- 239000010955 niobium Substances 0.000 claims description 10
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 9
- 125000004429 atom Chemical group 0.000 claims description 9
- 239000000470 constituent Substances 0.000 claims description 9
- -1 aluminum sodium fluoride Chemical compound 0.000 claims description 8
- 150000002500 ions Chemical group 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 229910001887 tin oxide Inorganic materials 0.000 claims description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titanium dioxide Inorganic materials O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 7
- 239000011787 zinc oxide Substances 0.000 claims description 7
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 6
- 150000002739 metals Chemical class 0.000 claims description 6
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 claims description 6
- 239000000654 additive Substances 0.000 claims description 5
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 claims description 5
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(III) oxide Inorganic materials [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 claims description 5
- 229910052746 lanthanum Inorganic materials 0.000 claims description 5
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 claims description 5
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 claims description 4
- 239000005751 Copper oxide Substances 0.000 claims description 4
- 229910000431 copper oxide Inorganic materials 0.000 claims description 4
- 238000002844 melting Methods 0.000 claims description 4
- 230000008018 melting Effects 0.000 claims description 4
- 150000004767 nitrides Chemical class 0.000 claims description 4
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 claims description 4
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 4
- 229910021332 silicide Inorganic materials 0.000 claims description 4
- 230000000996 additive effect Effects 0.000 claims description 3
- 229910052783 alkali metal Inorganic materials 0.000 claims description 3
- 150000001340 alkali metals Chemical class 0.000 claims description 3
- 239000000919 ceramic Substances 0.000 claims description 3
- 229910003437 indium oxide Inorganic materials 0.000 claims description 3
- 150000001247 metal acetylides Chemical class 0.000 claims description 3
- 229910000484 niobium oxide Inorganic materials 0.000 claims description 3
- MUMZUERVLWJKNR-UHFFFAOYSA-N oxoplatinum Chemical compound [Pt]=O MUMZUERVLWJKNR-UHFFFAOYSA-N 0.000 claims description 3
- 229910003446 platinum oxide Inorganic materials 0.000 claims description 3
- 229910052723 transition metal Inorganic materials 0.000 claims description 3
- 150000003624 transition metals Chemical class 0.000 claims description 3
- 229910002230 La2Zr2O7 Inorganic materials 0.000 claims description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 2
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 2
- 229910001936 tantalum oxide Inorganic materials 0.000 claims description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims 3
- 229910052593 corundum Inorganic materials 0.000 claims 2
- 229910001845 yogo sapphire Inorganic materials 0.000 claims 2
- 229910017582 La2Ti2O7 Inorganic materials 0.000 claims 1
- 229910002338 LaNbO4 Inorganic materials 0.000 claims 1
- 229910003379 Sm2Zr2O7 Inorganic materials 0.000 claims 1
- 229910000410 antimony oxide Inorganic materials 0.000 claims 1
- VTRUBDSFZJNXHI-UHFFFAOYSA-N oxoantimony Chemical compound [Sb]=O VTRUBDSFZJNXHI-UHFFFAOYSA-N 0.000 claims 1
- 235000010210 aluminium Nutrition 0.000 abstract 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 23
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 17
- 229910052727 yttrium Inorganic materials 0.000 description 17
- 229910052802 copper Inorganic materials 0.000 description 15
- 239000010949 copper Substances 0.000 description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 14
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 14
- 239000011248 coating agent Substances 0.000 description 14
- 238000000576 coating method Methods 0.000 description 14
- 230000007797 corrosion Effects 0.000 description 14
- 238000005260 corrosion Methods 0.000 description 14
- 229910052697 platinum Inorganic materials 0.000 description 14
- 239000000843 powder Substances 0.000 description 14
- 229910052719 titanium Inorganic materials 0.000 description 14
- 239000010936 titanium Substances 0.000 description 14
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 13
- 238000000354 decomposition reaction Methods 0.000 description 12
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 12
- 229910052759 nickel Inorganic materials 0.000 description 12
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 11
- 229910001610 cryolite Inorganic materials 0.000 description 11
- 229910052738 indium Inorganic materials 0.000 description 11
- 229910052742 iron Inorganic materials 0.000 description 11
- 229910052799 carbon Inorganic materials 0.000 description 10
- 229910052804 chromium Inorganic materials 0.000 description 10
- 239000011651 chromium Substances 0.000 description 10
- 229910052718 tin Inorganic materials 0.000 description 10
- 229910052725 zinc Inorganic materials 0.000 description 10
- 239000011701 zinc Substances 0.000 description 10
- 239000011133 lead Substances 0.000 description 9
- 229910052763 palladium Inorganic materials 0.000 description 9
- 229910052726 zirconium Inorganic materials 0.000 description 9
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 8
- 239000010948 rhodium Substances 0.000 description 8
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 7
- 229910017052 cobalt Inorganic materials 0.000 description 7
- 239000010941 cobalt Substances 0.000 description 7
- 229920001971 elastomer Polymers 0.000 description 7
- 229910052732 germanium Inorganic materials 0.000 description 7
- 229910052735 hafnium Inorganic materials 0.000 description 7
- 229910052703 rhodium Inorganic materials 0.000 description 7
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 7
- 229910010271 silicon carbide Inorganic materials 0.000 description 7
- 239000000758 substrate Substances 0.000 description 7
- 229910052715 tantalum Inorganic materials 0.000 description 7
- 229910052721 tungsten Inorganic materials 0.000 description 7
- 229910052797 bismuth Inorganic materials 0.000 description 6
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 229910052702 rhenium Inorganic materials 0.000 description 6
- 229910045601 alloy Inorganic materials 0.000 description 5
- 239000000956 alloy Substances 0.000 description 5
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 5
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 5
- 229910052747 lanthanoid Inorganic materials 0.000 description 5
- 150000002602 lanthanoids Chemical class 0.000 description 5
- 229910052745 lead Inorganic materials 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 229910052758 niobium Inorganic materials 0.000 description 5
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
- 229910052776 Thorium Inorganic materials 0.000 description 4
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 4
- 239000004020 conductor Substances 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 229910052741 iridium Inorganic materials 0.000 description 4
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 4
- 229910052748 manganese Inorganic materials 0.000 description 4
- 239000011572 manganese Substances 0.000 description 4
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 4
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 4
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 4
- 229910052707 ruthenium Inorganic materials 0.000 description 4
- 239000007921 spray Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 229910052716 thallium Inorganic materials 0.000 description 4
- 229910001928 zirconium oxide Inorganic materials 0.000 description 4
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 3
- 229910052787 antimony Inorganic materials 0.000 description 3
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 229910052788 barium Inorganic materials 0.000 description 3
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000006698 induction Effects 0.000 description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 229910052709 silver Inorganic materials 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 3
- BKVIYDNLLOSFOA-UHFFFAOYSA-N thallium Chemical compound [Tl] BKVIYDNLLOSFOA-UHFFFAOYSA-N 0.000 description 3
- ZSLUVFAKFWKJRC-IGMARMGPSA-N 232Th Chemical compound [232Th] ZSLUVFAKFWKJRC-IGMARMGPSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 229910052768 actinide Inorganic materials 0.000 description 2
- 150000001255 actinides Chemical class 0.000 description 2
- 229910052793 cadmium Inorganic materials 0.000 description 2
- 229910000428 cobalt oxide Inorganic materials 0.000 description 2
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 2
- 239000000306 component Substances 0.000 description 2
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 2
- 229910000457 iridium oxide Inorganic materials 0.000 description 2
- 235000013980 iron oxide Nutrition 0.000 description 2
- PLDDOISOJJCEMH-UHFFFAOYSA-N neodymium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Nd+3].[Nd+3] PLDDOISOJJCEMH-UHFFFAOYSA-N 0.000 description 2
- 229910000480 nickel oxide Inorganic materials 0.000 description 2
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 2
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 2
- HBEQXAKJSGXAIQ-UHFFFAOYSA-N oxopalladium Chemical compound [Pd]=O HBEQXAKJSGXAIQ-UHFFFAOYSA-N 0.000 description 2
- 229910003445 palladium oxide Inorganic materials 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- 239000010937 tungsten Substances 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 2
- QYEXBYZXHDUPRC-UHFFFAOYSA-N B#[Ti]#B Chemical compound B#[Ti]#B QYEXBYZXHDUPRC-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229910002244 LaAlO3 Inorganic materials 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 229910052772 Samarium Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- ZMIGMASIKSOYAM-UHFFFAOYSA-N cerium Chemical compound [Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce] ZMIGMASIKSOYAM-UHFFFAOYSA-N 0.000 description 1
- 229910000420 cerium oxide Inorganic materials 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 description 1
- 230000002844 continuous effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- YBMRDBCBODYGJE-UHFFFAOYSA-N germanium oxide Inorganic materials O=[Ge]=O YBMRDBCBODYGJE-UHFFFAOYSA-N 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 229910052740 iodine Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 1
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 1
- PVADDRMAFCOOPC-UHFFFAOYSA-N oxogermanium Chemical compound [Ge]=O PVADDRMAFCOOPC-UHFFFAOYSA-N 0.000 description 1
- SJLOMQIUPFZJAN-UHFFFAOYSA-N oxorhodium Chemical compound [Rh]=O SJLOMQIUPFZJAN-UHFFFAOYSA-N 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 229910052705 radium Inorganic materials 0.000 description 1
- HCWPIIXVSYCSAN-UHFFFAOYSA-N radium atom Chemical compound [Ra] HCWPIIXVSYCSAN-UHFFFAOYSA-N 0.000 description 1
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 description 1
- 229910003450 rhodium oxide Inorganic materials 0.000 description 1
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 1
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 1
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 229910052714 tellurium Inorganic materials 0.000 description 1
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 1
- CMJCEVKJYRZMIA-UHFFFAOYSA-M thallium(i) iodide Chemical compound [Tl]I CMJCEVKJYRZMIA-UHFFFAOYSA-M 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- WQJQOUPTWCFRMM-UHFFFAOYSA-N tungsten disilicide Chemical compound [Si]#[W]#[Si] WQJQOUPTWCFRMM-UHFFFAOYSA-N 0.000 description 1
- 229910021342 tungsten silicide Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Landscapes
- Compositions Of Oxide Ceramics (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The invention relates to a method for producing alumi-num by molten salt electrolysis of aluminum oxide and in parti-cular to an electrode used in the aluminum reduction cell wherein an electrode base, at least in that portion which is brought into contact with the molten salt bath, is coated with a composition comprising at least 50% by weight of electronic conductive oxide ceramics, or said portion of the electrode is made of said com-position.
The invention relates to a method for producing alumi-num by molten salt electrolysis of aluminum oxide and in parti-cular to an electrode used in the aluminum reduction cell wherein an electrode base, at least in that portion which is brought into contact with the molten salt bath, is coated with a composition comprising at least 50% by weight of electronic conductive oxide ceramics, or said portion of the electrode is made of said com-position.
Description
The present invention relates to the manufacture of aluminum by molten salt electrolysis of aluminum oxide using a particular electrode. More particularly, it relates to the use in aluminum reduction cells of an electrode, specifically an anode.
It is known to manufacture aluminum by molten salt electrolysis of aluminum oxide dissolved in a bath of composite fluoride of aluminum and sodium (AlF3-3NaF) or so-called cryolite, using a carbon anode. Usually, the above electrolysis process is conducted at about 900 - 1000C. When the car~on ~node is used to manufacture aluminum, the carbon anode is consumed by oxidation due to oxygen produced by the decomposition of aluminum oxide by the amount of about 330 kg theoretically and 400 - 450 kg actually, per ton of aluminum. For this reason, it is neces~
sary to continuously adjust the position of the electrode to maintain it at a constant level, and it is also required to replace the anode before it is completely consumed. These are ; operational and economical defects.
As an approach to overcome the above difficulties, various non-consumable anodes have been recently developed. For example, it has been known to use an oxygen ion-conductive anode consisting mainly of zirconium oxide (British Patent 1,152,124)~
This method, however, is disadvantageous in that it requires an apparatus for removing oxygen produced and the operation is com-plex~ It has also been proposed to use an anode consisting of an electronic conductive metal oxide comprising at least 80~ by weight o tin oxide ~British Patent 1~295,117). This method lS
also disadvantageous in that the anode has poor chemical resis tance to the molten salt.
The present invention pxovides in the molten salt electrolysis of aluminum oxide the use of a so-called non-consumable electrode which does not react with the oxygen produced ~
~: .
.
~L~694~L
and which has chemical resistance to the molten salt.
After extensive research and investigation to find ou~ such a non-consumable electrode for use in the molten salt electrolysis of aluminum oxide, the inventors have found that the oxides which have general formulas of X Y 2 (where X is a monovalent metal, Y is a trivalent metal, and O is an oxygen atom), X2 Y2 7 (where X is a trivalent metal, Y is a tetra-valent metal, and 0 is an oxy~en atom), X Y O4 (where X i5 a trivalent or tetravalent metal, Y is a pentavalent or tetra-valent metal, and O is an oxygen atom, and Y is selected frompantavalent metals when X is a trivalent metal while Y is selected from tetravalent metal when X is a tetravalent metal), f~( ) xAi~ f (Bj) XBj} 3 (where Ai and Bj are metal atoms, XAi, XBj are molar fractions of Ai and Bj constituents, O is an oxygen atom, k and Q are numbers of metal constituents constitutingAi andBj, respectively, and constituent ions at positions A and B satisfy the requirements k ~ ~ X - 1, ~ XBj - 1, 0 ~ XAi _ , Bj (wherein if XAi = 1, then 0 < XBj ~ 1 and if XBj = 1 k then 0 ~ XAi < 1)~ ~lXAi ~Ai nA 9 ~ lXBj n~
k ~ .
n~, nA ~ n~ 6~ ~ lrAi XAi r~ ~lrBj XB; r~
0.8 < ~ A o < 1.1 (wherein X~i and XBj are molar fractions of the atoms, nAi and n~j are valances of the atoms, rAi and RBj are ion radii of ~he atoms and rO is ion -:
radium of oxygen)3 ~ Ax Oy Ta2 05 (where A is a divalent, tri-valent or tetravalent metal, 0 is an oxygen atom, and if A is a ~ --' ~'., '
It is known to manufacture aluminum by molten salt electrolysis of aluminum oxide dissolved in a bath of composite fluoride of aluminum and sodium (AlF3-3NaF) or so-called cryolite, using a carbon anode. Usually, the above electrolysis process is conducted at about 900 - 1000C. When the car~on ~node is used to manufacture aluminum, the carbon anode is consumed by oxidation due to oxygen produced by the decomposition of aluminum oxide by the amount of about 330 kg theoretically and 400 - 450 kg actually, per ton of aluminum. For this reason, it is neces~
sary to continuously adjust the position of the electrode to maintain it at a constant level, and it is also required to replace the anode before it is completely consumed. These are ; operational and economical defects.
As an approach to overcome the above difficulties, various non-consumable anodes have been recently developed. For example, it has been known to use an oxygen ion-conductive anode consisting mainly of zirconium oxide (British Patent 1,152,124)~
This method, however, is disadvantageous in that it requires an apparatus for removing oxygen produced and the operation is com-plex~ It has also been proposed to use an anode consisting of an electronic conductive metal oxide comprising at least 80~ by weight o tin oxide ~British Patent 1~295,117). This method lS
also disadvantageous in that the anode has poor chemical resis tance to the molten salt.
The present invention pxovides in the molten salt electrolysis of aluminum oxide the use of a so-called non-consumable electrode which does not react with the oxygen produced ~
~: .
.
~L~694~L
and which has chemical resistance to the molten salt.
After extensive research and investigation to find ou~ such a non-consumable electrode for use in the molten salt electrolysis of aluminum oxide, the inventors have found that the oxides which have general formulas of X Y 2 (where X is a monovalent metal, Y is a trivalent metal, and O is an oxygen atom), X2 Y2 7 (where X is a trivalent metal, Y is a tetra-valent metal, and 0 is an oxy~en atom), X Y O4 (where X i5 a trivalent or tetravalent metal, Y is a pentavalent or tetra-valent metal, and O is an oxygen atom, and Y is selected frompantavalent metals when X is a trivalent metal while Y is selected from tetravalent metal when X is a tetravalent metal), f~( ) xAi~ f (Bj) XBj} 3 (where Ai and Bj are metal atoms, XAi, XBj are molar fractions of Ai and Bj constituents, O is an oxygen atom, k and Q are numbers of metal constituents constitutingAi andBj, respectively, and constituent ions at positions A and B satisfy the requirements k ~ ~ X - 1, ~ XBj - 1, 0 ~ XAi _ , Bj (wherein if XAi = 1, then 0 < XBj ~ 1 and if XBj = 1 k then 0 ~ XAi < 1)~ ~lXAi ~Ai nA 9 ~ lXBj n~
k ~ .
n~, nA ~ n~ 6~ ~ lrAi XAi r~ ~lrBj XB; r~
0.8 < ~ A o < 1.1 (wherein X~i and XBj are molar fractions of the atoms, nAi and n~j are valances of the atoms, rAi and RBj are ion radii of ~he atoms and rO is ion -:
radium of oxygen)3 ~ Ax Oy Ta2 05 (where A is a divalent, tri-valent or tetravalent metal, 0 is an oxygen atom, and if A is a ~ --' ~'., '
- 2 ~
.", ,~.,,.i . :
~g~
divalent metal, then x=y=l, if A is a trivalent metal, then x=~
y=3,and if A is a tetravalent metal then x=1, y=2), and A~ Oy-Nb2 5 (where A is a divalent, trivalent or tetravalent metal, O is an oxygen atom, and if A is a divalent metal, then x=y=l, if A is a trivalent metal, then x=2, y=3 and if A is a tetra-valent metal then x=l, y-2), exhibit high electronic conduc-tivity at the temperature of about 900 to 1000C, present catalytic action to the yeneration of oxygen and exhibit chemi-cal resistance to the molten salt. In this way, a non consumable 10 electrode for aluminum reduction cells has been established.
Accordingly the present invention provides a method for producing aluminum by molten salt electrolysis of aluminum oxide which comprises electrolyzing aluminum oxide dissolved in a molten salt containing aluminum sodium fluoride as main com-ponent by passing a direct current from an anode to a cathode disposed in said molten salt wherein at least that portion of ;~
' . :
' . ~ :
~L~6~
at least one of the anode a~d cathode which is brought into contact wi~h a molten salt bath is made or covered with a composition including at least 50% by weight of one or more oxides which have chemical resistance to the molten salt and electronic cond~lctivity and gen~ral formulas of X Y O~ (where X, Y and O are the same as those described above), X2 Y2 7 (where X, Y and O are the same as those described above), X Y
O4 ~where X, Y and O are the same as those described above), . 10 ~ ~ (where symbols and con-stituent ion conditions at positions A and B are the same as those described above), Ax y Ta2 5 (where symbols and con- ~
ditions for A, x, y are the same as those described above) and ~;
Ax y Nb2 5 (where symbols and conditions for A, x, y are the same as those described above) and up to 50~ by weight of an additive selected from oxides, carbides, nitrides, borides and -~
silicides of alkali metals, alkaline earth me~als, transition .~
: metals, platinum group metals and rare earth elements. ~ : :
The electrode used in the method according to the :~
pxesent invention has at least that portion thereof which is brought into contact with ~he molten salt bath coated with or entirely formed by the composition which includes at least about 50~ by weight of one or more oxides represented by the general ~ :
~ormulas X Y 2 (where X, Y, O are the same as those described above~, X2 Y~ O7 (where X, Y and O are the same as those des- ::
cribed above), X Y O4 ~where X, ~, O are the same as those des-{ ~ l(Ai) xAi} f 1 (Bj) XBj } 3 (where the symbols ' ' ~ 4 -~ " . . .
;
.~. ..... . . ...... .. .
~9~
1 and constituent ion conditions at positions A and are the same as those described above), Ax y ~a2 5 (where the symbols and the conditions for A, x, y are the same as those described above), and Ax y Nb2 5 (where the symbols and -the condi-tions for A, x, y are the same as those described above).
Those oxides which are represented by the general formula X Y 2 are usually called as dela-10 fossi-te structure oxides wherein X is a monovalent ..
metal such as platinum, palladium, silver and copper, ~:
Y is a trivalent metal such as cobalt, yttrium, indium, chromium~ nickel, rhodium, lead, iron and a lanthanide element. ~hose oxides which are represent-ed by the general formula X2 Y2 7 are called as pyrochlore structure oxides wherein X is a trivalent metal such as bismuth, yttrium5 indium, thallium and a lanthanide element such as lanthanum, cerium, praseodymium, neodymlum, samarium~and the like, and Y is a tetravalent metal such as tin, germanium, titanium, zirconium, platinum, ruthenium, iridium, rhodium, hafnium and osmium. ~hose oxides which are represented by the general formula X Y 04 are called . :
as scheelite structure oxides wherein X is a trivalent `-~-metal such as bismuth, a lanthanide element and yttrium or a tetravaleht metal such as zirconium, hafnium~ tin and thorium~ and Y is a pentavalent metal such as niobium,:tantalum, antimony and vanadium or a tetravalent metal such as:germanium and tin ~if X
~0 is a trivalent~metal Y is~selected from pentavalent .
~IL06914G~L
1 metals while if X is a tetravalent metal Y is select-ed from tetravalent metals). ~hose oxides which are represented by the general formula ~ ~1 ( ) XAi~ ~ ~ (Bj) XBj~ 03 are called as composite perovskite structure oxides wherein Ai is a metal such as a lanthanide element, an actinide element, yttrium, thallium, silver, bismuth, lead, barium, zirconium, cadmium and hafnium, and ~j is a metal such as a lanthanide element, an actinide element, aluminum, gallium, indium, li-thium, potassium, silicon, germanium, tin, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, silber .:
molybden.um, ruthenium, rhodium, palladium, antimony, 15 tellurium, hafnium, tantalum, tungsten, rhenium, iridium, .
- : .
thallium, thorium and platinum. Those oxides which are represented by the general formula AxOy . ~a2 5 -are called as rutile structure oxides and those re~
Y Ax y ~b2 5 are called as columbite 20 structure oxides, wherein A is a divalent metal such cobalt, nickel, zinc, copper, magnesium, cal~
cium, manganese, tin, iron and lead, and preferably cobalt, nickel, zinc, tin and iron, or a trivalent ~.
metal such as iron, chromium, aluminum; indium, manganese, cobalt, nickel and rhodium, and:preferably iron, chromium,~aluminum,:indium, or a tetravalent ~: metal such as tin, titaniumt germanium, silicon, i : zirconium and hafnium, and preferably tint titanium ! ,.. ''' and zirconium.
' ' -~ - 6 - : :
... ' - . , - . . - . ~ . ~ . . -. . . . . . - .. .. . ...... .
- .. , . . . - ... . . . . .
1~99~
1 More particularly, the oxide represented by the general formula XY02 includes PtCo02, PtRh02, PdCo02, PdRh02, PdNi02, AgIn02, AgCo02, AgRh02; the oxlde represented b~y the general formula X2Y207 include~ Bi2Rh207, ~i2I~207~ Bi2RU2 7' 2 2 7 2 2 7~ a2Ir27~ ~a2$n27, ~a2Zr2079 ~a2Ge27 La2Ru207, La20s207~ Y2Ti2o7~ Y2~I~27' Y2Sn2 7' Y2Zr207, Y2Ge207, Y2Ru207~ Y2S27' Y2Ir2 7' --2 2 7' 2Sn27~ Ce2Zr207~ Ce2Ge207, Ce2Ru207 9 2 2 7 9 ~?2Xf`27, Ce2Ir207 ~ In2Ge207, In2Sn20 ~a Pt27' Y2Pt27~ Pr2zr2o7~ Pr2Sn2o7, 2 2 7 2 2 7' m2Zr207~ Sm2Sn27 (while pure oxides such as ~a2$n27 and Y2Zr27 usually have low elect-ronic conductivity and it may be difficult to use them . ~
15 as an electronic conductive material, they can be :
rendered highly conducti~e by having certain consti- ~ .
tuent added thereto. For example, by adding 5 mole % of ZnO and 5 mole ~O of Cu0 to ~a2Sn207, it is possible to improve the conductivity by the ~actor of a-t least 1000 times~ Since it is common practice to represent such a conductivity-imparted oxide by 07 9 they are represented herein in accordance with the common practice.); the oxide represented by the general formula XY04 includes ZrGe04, ThGe04, ZrSnO4, ~aTaO4, ~aNbO4, YTaO4, Y~b04? the~oxide - represented by the general formula :
(Ai)XA~ 3)XBJ} 03 incl~des ~' . . : .
:
.
46~
1 . ~ ( Bl ) 2 ( B2 ) 13
.", ,~.,,.i . :
~g~
divalent metal, then x=y=l, if A is a trivalent metal, then x=~
y=3,and if A is a tetravalent metal then x=1, y=2), and A~ Oy-Nb2 5 (where A is a divalent, trivalent or tetravalent metal, O is an oxygen atom, and if A is a divalent metal, then x=y=l, if A is a trivalent metal, then x=2, y=3 and if A is a tetra-valent metal then x=l, y-2), exhibit high electronic conduc-tivity at the temperature of about 900 to 1000C, present catalytic action to the yeneration of oxygen and exhibit chemi-cal resistance to the molten salt. In this way, a non consumable 10 electrode for aluminum reduction cells has been established.
Accordingly the present invention provides a method for producing aluminum by molten salt electrolysis of aluminum oxide which comprises electrolyzing aluminum oxide dissolved in a molten salt containing aluminum sodium fluoride as main com-ponent by passing a direct current from an anode to a cathode disposed in said molten salt wherein at least that portion of ;~
' . :
' . ~ :
~L~6~
at least one of the anode a~d cathode which is brought into contact wi~h a molten salt bath is made or covered with a composition including at least 50% by weight of one or more oxides which have chemical resistance to the molten salt and electronic cond~lctivity and gen~ral formulas of X Y O~ (where X, Y and O are the same as those described above), X2 Y2 7 (where X, Y and O are the same as those described above), X Y
O4 ~where X, Y and O are the same as those described above), . 10 ~ ~ (where symbols and con-stituent ion conditions at positions A and B are the same as those described above), Ax y Ta2 5 (where symbols and con- ~
ditions for A, x, y are the same as those described above) and ~;
Ax y Nb2 5 (where symbols and conditions for A, x, y are the same as those described above) and up to 50~ by weight of an additive selected from oxides, carbides, nitrides, borides and -~
silicides of alkali metals, alkaline earth me~als, transition .~
: metals, platinum group metals and rare earth elements. ~ : :
The electrode used in the method according to the :~
pxesent invention has at least that portion thereof which is brought into contact with ~he molten salt bath coated with or entirely formed by the composition which includes at least about 50~ by weight of one or more oxides represented by the general ~ :
~ormulas X Y 2 (where X, Y, O are the same as those described above~, X2 Y~ O7 (where X, Y and O are the same as those des- ::
cribed above), X Y O4 ~where X, ~, O are the same as those des-{ ~ l(Ai) xAi} f 1 (Bj) XBj } 3 (where the symbols ' ' ~ 4 -~ " . . .
;
.~. ..... . . ...... .. .
~9~
1 and constituent ion conditions at positions A and are the same as those described above), Ax y ~a2 5 (where the symbols and the conditions for A, x, y are the same as those described above), and Ax y Nb2 5 (where the symbols and -the condi-tions for A, x, y are the same as those described above).
Those oxides which are represented by the general formula X Y 2 are usually called as dela-10 fossi-te structure oxides wherein X is a monovalent ..
metal such as platinum, palladium, silver and copper, ~:
Y is a trivalent metal such as cobalt, yttrium, indium, chromium~ nickel, rhodium, lead, iron and a lanthanide element. ~hose oxides which are represent-ed by the general formula X2 Y2 7 are called as pyrochlore structure oxides wherein X is a trivalent metal such as bismuth, yttrium5 indium, thallium and a lanthanide element such as lanthanum, cerium, praseodymium, neodymlum, samarium~and the like, and Y is a tetravalent metal such as tin, germanium, titanium, zirconium, platinum, ruthenium, iridium, rhodium, hafnium and osmium. ~hose oxides which are represented by the general formula X Y 04 are called . :
as scheelite structure oxides wherein X is a trivalent `-~-metal such as bismuth, a lanthanide element and yttrium or a tetravaleht metal such as zirconium, hafnium~ tin and thorium~ and Y is a pentavalent metal such as niobium,:tantalum, antimony and vanadium or a tetravalent metal such as:germanium and tin ~if X
~0 is a trivalent~metal Y is~selected from pentavalent .
~IL06914G~L
1 metals while if X is a tetravalent metal Y is select-ed from tetravalent metals). ~hose oxides which are represented by the general formula ~ ~1 ( ) XAi~ ~ ~ (Bj) XBj~ 03 are called as composite perovskite structure oxides wherein Ai is a metal such as a lanthanide element, an actinide element, yttrium, thallium, silver, bismuth, lead, barium, zirconium, cadmium and hafnium, and ~j is a metal such as a lanthanide element, an actinide element, aluminum, gallium, indium, li-thium, potassium, silicon, germanium, tin, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, silber .:
molybden.um, ruthenium, rhodium, palladium, antimony, 15 tellurium, hafnium, tantalum, tungsten, rhenium, iridium, .
- : .
thallium, thorium and platinum. Those oxides which are represented by the general formula AxOy . ~a2 5 -are called as rutile structure oxides and those re~
Y Ax y ~b2 5 are called as columbite 20 structure oxides, wherein A is a divalent metal such cobalt, nickel, zinc, copper, magnesium, cal~
cium, manganese, tin, iron and lead, and preferably cobalt, nickel, zinc, tin and iron, or a trivalent ~.
metal such as iron, chromium, aluminum; indium, manganese, cobalt, nickel and rhodium, and:preferably iron, chromium,~aluminum,:indium, or a tetravalent ~: metal such as tin, titaniumt germanium, silicon, i : zirconium and hafnium, and preferably tint titanium ! ,.. ''' and zirconium.
' ' -~ - 6 - : :
... ' - . , - . . - . ~ . ~ . . -. . . . . . - .. .. . ...... .
- .. , . . . - ... . . . . .
1~99~
1 More particularly, the oxide represented by the general formula XY02 includes PtCo02, PtRh02, PdCo02, PdRh02, PdNi02, AgIn02, AgCo02, AgRh02; the oxlde represented b~y the general formula X2Y207 include~ Bi2Rh207, ~i2I~207~ Bi2RU2 7' 2 2 7 2 2 7~ a2Ir27~ ~a2$n27, ~a2Zr2079 ~a2Ge27 La2Ru207, La20s207~ Y2Ti2o7~ Y2~I~27' Y2Sn2 7' Y2Zr207, Y2Ge207, Y2Ru207~ Y2S27' Y2Ir2 7' --2 2 7' 2Sn27~ Ce2Zr207~ Ce2Ge207, Ce2Ru207 9 2 2 7 9 ~?2Xf`27, Ce2Ir207 ~ In2Ge207, In2Sn20 ~a Pt27' Y2Pt27~ Pr2zr2o7~ Pr2Sn2o7, 2 2 7 2 2 7' m2Zr207~ Sm2Sn27 (while pure oxides such as ~a2$n27 and Y2Zr27 usually have low elect-ronic conductivity and it may be difficult to use them . ~
15 as an electronic conductive material, they can be :
rendered highly conducti~e by having certain consti- ~ .
tuent added thereto. For example, by adding 5 mole % of ZnO and 5 mole ~O of Cu0 to ~a2Sn207, it is possible to improve the conductivity by the ~actor of a-t least 1000 times~ Since it is common practice to represent such a conductivity-imparted oxide by 07 9 they are represented herein in accordance with the common practice.); the oxide represented by the general formula XY04 includes ZrGe04, ThGe04, ZrSnO4, ~aTaO4, ~aNbO4, YTaO4, Y~b04? the~oxide - represented by the general formula :
(Ai)XA~ 3)XBJ} 03 incl~des ~' . . : .
:
.
46~
1 . ~ ( Bl ) 2 ( B2 ) 13
3 3 ( A = ~a, Y, 13i Bl = Ni, Co, ~u, Zn, Pd ~ B2 = Ta, Nb 2 - A(Bl)~(B2 )13 ( A = I~a, Y, Bi . .. ::
= Ni, Co, Cu, Zn, Pd ~ B2 = W, Re 3. A(}31)1(B2)1 3 ( A = ~a, Y, :E3i : .
' Bl ~ Ni, Co, Cu, Zn, Pd . ~::
~ B2 ~ Zr, H~, Tl, Sn, Ge, ~h, Pt, Ir, Ru ~:
= Ni, Co, Cu, Zn, Pd ~ B2 = W, Re 3. A(}31)1(B2)1 3 ( A = ~a, Y, :E3i : .
' Bl ~ Ni, Co, Cu, Zn, Pd . ~::
~ B2 ~ Zr, H~, Tl, Sn, Ge, ~h, Pt, Ir, Ru ~:
4. A(Bl)l(B2)103 ( A = 1a, Y, Bi = In, Al, :Fe, Cr, Mn, Y, Rh 2 = In, Al, ~e, Cr, Mn, Y, Rh provided that A is yttrium, 131 and B2 . .
are not yttr l.um.
are not yttr l.um.
5 . A ( Bl )l ( B2 )1~;
. ~ 2 ~ 2 ~ A = ~a, Y, :Bi 1 Bl = Ag, Tl, I,i, K
:B2 = Ta, Nb :
.~ : :
, : ~ .
, .. , .. .... - . .. ",, ... -.. , .,, . , , .. .. ,... , ,,,.. , ,. ,. , , .... , . . - :
~9~6~
. ~ 2 ~ 2 ~ A = ~a, Y, :Bi 1 Bl = Ag, Tl, I,i, K
:B2 = Ta, Nb :
.~ : :
, : ~ .
, .. , .. .... - . .. ",, ... -.. , .,, . , , .. .. ,... , ,,,.. , ,. ,. , , .... , . . - :
~9~6~
6 A(Bl ) 2 (B2 )~3 ~A = Pb, Ba, Cd Bl = Ag, Tl ~ B2 = W, Re
7-A( 31)1(B2)3 3 4 4 :
A = Pb, Ba, Cd Bl = Ag9 Tl I B2 = Ta, l~b - . .
A = Pb, Ba, Cd Bl = Ag9 Tl I B2 = Ta, l~b - . .
8 A ( Bl ) 1 ( B2 ) 13 ( A = Pb, Ba~ Cd '~ ~1 = Ni, Co, Cu, Zn, Pd : ~ 3 3 . ~ ~ , , , ( A = Pb, Bat Cd Bl = Nl, ~Co, Cu, Zn, Pd ~;
~, :
10 . A ( Bl ) 2 ( B2 ) 103 ~: ( A ~ Pb, Ba, Cd;
a, In, Al,~ Fe, Cr, 1~, Y, :Rh ~B2 = W, Re :
,: :
, ~
, : : : :: , .: .
~, :
10 . A ( Bl ) 2 ( B2 ) 103 ~: ( A ~ Pb, Ba, Cd;
a, In, Al,~ Fe, Cr, 1~, Y, :Rh ~B2 = W, Re :
,: :
, ~
, : : : :: , .: .
9 ~
.
: ' , ,:
" , ~6;3 694~
1 ) ( 2 ) 1 3 (A = Pb, Ba, Cd Bl = ~a, In, Al~ Fe, Cr, Mn, Y
B2 = Ta, Nb ( Bl ) 1 ( B2 ) 33 A = Ag 7 Tl Bl = Ni, aO ~ cu ~ Zn, Pd ~ B W Re 13 . A ( Bl ) 1 ( B2 ) 23 A = Ag, Tl ~ .
a, In, Al, Fe, Cr, r~, Y, Rh ~ B2 = W, Re 14- A(Bl)l(E32)13 - . .... .
A = Ag, Tl Bl = Zr, Hf, Ti, Sn9 Ge, Th, Pt, Ir, Ru ~ B2 = W, Re 15.(Al)l(A2)1B03 . : 2 2 Al = Ag9 Tl A2 = Bi, I,a, Y
B = Zr 9 Hf, Ti, Sn, Ge, Th, Pt, Xr, Ru ::
. .
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.
: ' , ,:
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1 ) ( 2 ) 1 3 (A = Pb, Ba, Cd Bl = ~a, In, Al~ Fe, Cr, Mn, Y
B2 = Ta, Nb ( Bl ) 1 ( B2 ) 33 A = Ag 7 Tl Bl = Ni, aO ~ cu ~ Zn, Pd ~ B W Re 13 . A ( Bl ) 1 ( B2 ) 23 A = Ag, Tl ~ .
a, In, Al, Fe, Cr, r~, Y, Rh ~ B2 = W, Re 14- A(Bl)l(E32)13 - . .... .
A = Ag, Tl Bl = Zr, Hf, Ti, Sn9 Ge, Th, Pt, Ir, Ru ~ B2 = W, Re 15.(Al)l(A2)1B03 . : 2 2 Al = Ag9 Tl A2 = Bi, I,a, Y
B = Zr 9 Hf, Ti, Sn, Ge, Th, Pt, Xr, Ru ::
. .
'` ~ '. :''' ', : ~ ,-.,. ~' - :.'.':
- 10 _ , . . '.
, "',' . '.
~69~
6. (Al) (A2)l(Bl)l(B2)l3 Al = Ag, Tl A2 = La, Y, Bi ¦ Bl = In, Al 7 Fe, Cr, Mn ~B2 = Ta, Nb .
1 Pre~erably, a perovskite structure composite oxide such as ~a(Ni2Ta )03, La(Ni2Nb )03, ~a(Pd2Tal)03, ~a(Pd2Nbl)03, Y(Ni2~al)03, Y(Ni2Nbl)03, Y(Pd2Ta )03, Y(Pd2~bl)03, Bi(Ni2Tal)03, ~i(NilZr )03, La(NilPtl)03, (Ni Ptl)03, La(InlY )03, ~a(In Al )03, La(Pd1Snl)03, Y(Pd Snl)03, ~i(Pd Snl)03, (Ag1Bi )ZrO3, (Ag_Y_)SnO3, (AglLal)(InlTal)3~ (Agl~il)(InlNbl) 3, 1 1 3 ~a(Yl~nl)03, 1a(Fe1Inl)03, La(Fel~ 1)03 may be select-ed. The oxides represented by the general formulas x y Ta205 and AxOy-Nb205 lnclude CoO-Ta205, ~oO-~b205, NiO-Ta205, NiO-Nb205~ ZnO Ta205, ZnO Nb205~ ~ ' SnO Ta205, SnO Nb205, FeO Ta205~ ~eO Nb205~ Fe23 Ta23 Fe203-Nb205~ Cr23-Ta205~Cr203 Nb205, 2 3 2 5 ~: ~ A123 ~b25~ In2o3 Ta2o5~In2o3.~b2o5~ 2 2 5 2 ~b25~ Ti2 Ta2st~Ti2-Nb205~ ZrO2-Ta O
2rO2-Nb205. (While pure composit~e oxide such as A1203-Ta205 usually has B low electronic~conductivity and it is difficul-t to use it as an electronic ; -:
.
' - 11 - :
6~L
conductive material, it may be ~endered hi~hl~ conductive by having certain constituent added thereto~ Since it is a common practice to represent such a conductivity-imparted oxide by A1~03.Ta205, it is represented herein in accordance with the common practice.) The oxides of the present invention as represented by the general formulas XY02, X2Y207, XY04, { ~ (~i)XA~ ~ ~ (Bj)XBj} 03, AXy'Ta2S and AxOy.Nb205 are electronic conductive and are different from the known ion-conductive electrode in their electro-conductive modes and also different from a tin oxide electrode in their crystal structures and hence they provide an electrode of a novel composi-tion. The electrode made of such electronic conductive oxide ceramics exhibits excellent effect of high conductivity under electrolysis conduction and high resistance to a molten salt bath containing cryolite as main component~
The electrode used in the method of the present invention is prepared by forming at leas~ that portion thereof which is ; 20 brought into contact with the molten salt by composition includ-ing at least 50% by weight, preferably at least 75% by weight of an oxide selected from those represented by XY02, X2Y207, XY04, (Ai ) X ~ ~ ~ (B j ) XB~3 03~ AxOy Ta2 5' x y 2 5 .
mixture thereof.
In the manufacture of the electrode used in the method ' ~ -12-4 ~
1 the present invention, in order to enhance the density of the electrode, heat resistance, thermal-shock resistance, resistance to molten bath, and elec-tric conductivity, spinel structure oxide or perovskite structure may be mixed to the electronic conductive oxide ceramics, as required. The content of the addi-ti~e is usually not more than 50% by weight 9 and oxides, carbides, nitrides, borides and silicides of alkali metals, alkaline earth metals, transition metals, platinum group metals and rare earth elements may be mixed thereto as required. The amount of such additives is usually not more than 50% by weight because the elec-tric conductivity~ resistance to bath and resistance to oxidation are deteriorated above 50% by ~eight. ~he particularly preferred additives are oxides of transition metals such as manganese oxide, nickel oxide, cobalt oxide and iron oxide, or oxides of platinum group metals such as ruthenium oxide, palladium oxide, platinum oxide, rhodium oxide and iridium oxide, or oxides of rare earth elements such as yttrium oxide, cerium oxide, neodymium oxide and lanthanum oxide, or titanium nitride, tita-nium boride, lanthanum boride, zirconium boride and :
tungsten silicide.
~n optimum condition for the electrical resistance of the electronic conductiue oxide ceramics used for the electrode depends on the shape of the -electrode, that is, the thickness of the coating, and the material thereof preferably has the con-ductivity o at least about 0.1 Q 1 cm 1 (at loooa ) .
- .. - , ; . ~ . . . . :. : : .
- - . . : :: : - , . . : -~ ~ ', . A
The electronic conductive oxide ceramics for coating or forming the electrode o~ the present invention has a melting point higher than the operating temperature of an electrolytic cell, usually at or higher than about 1000C and preferably at or higher than 1200DC.
The electrode used in the method of the present inven-tion may be prepared by forming a coating including the above oxide ceramics on a surface of an electrode base of a conductive .
material such as a metal or alloy e.g. titanium, nickel or copper, carbon, graphite or such as a carbide, nitride, boride, or silicide of titanium, molybdenum or tungsten, or the electrode may be entirely made of the composition including the above ~ oxide cera~ics.
; In coating the surface of the electrode with the oxide ceramics, the composition including the composition as represented by the general formula XYO2, X2Y2O7, XYO4, ~ ~l( ) Ai ~ Bi)XB~} 3' AXOy-Ta2O5 or AXOy.Nb2O5 may be flame sprayed or plasma sprayed and then heat treated as - .
20 . required, or it may be electroplated. Alternatively, inorganic ~:
or organic metal compounds which may form the oxide or the above , structure when it is sintered may be applied, dipped, sprayed : or deposited by thermal decomposition,followed by sintering, .
or an electrode base made of an alloy which forms the oxide of the above structure when it is oxidized or an electrode base , ~ coated with such an alloy is prepared and then ' ;' '`
. .
: . ' :
~ 30 ;~ ;
, ~.
1~6946~
it is oxidized. It should be understood that in coating the electrode base with the oxide ceramics, an internal layer of an oxide of platinum group metal may be provided therebetween to enhance the adhesiveness of the oxide ceramics to the base.
In practicing the present invention, the oxide as represented by the general formula XYO2, X2Y2O7, XYO4, ~ ~ (Ai)XAil ~ ~ (Bj)XBj~ 3~ Axy-Ta2s~ or AxOy-Nb2O5 may be preferably prepared by sintering a mixture of appropriate composition such as oxide, hydroxide, chloride, sulfate, nitrate, carbonate or oxalate of said metal, usually at 500C or higher and preferably at 800C - 2500C. The sintering may be conducted in a high frequency induction heating furnace or a resistance heating furnace at 500C or higher and preferably at 800 - 2500C under reduced pressure, atmospheric pr~ssure or elevated pressure and preferably by hot pressing under 50 - lO00 kg/c 2 .
When the electrode is used in an aluminum reduction cell, the connection between the electrode and a conductor stud .
need not be specified but conventional means may be used. That -is, the connection by threading, welding, molding or casting may be used or the connection may be made through a low melting point metal such as aluminum, tin or copper, or alloy or metal-lic compound thereof.
For uniformity of voltage and reduction .'~ ~ ;.
- :' ; ~3694~;~
in corrosion o~ the sur,face, i~ :is use,ful to coat the surface of the non consumable anode o~ the present invention, except ~ -that portion thereof required to make the electric current to flow, with an anti-corrosi~e insulating material such as 2' 24~ MgA12O4, LaAlO3 or La2Zr2O7~
The most general use of the non-consumable electrode of the present invention thus obtained is to replace convention-al carbon electrode at least in its portion in contact with the molten salt bath in the electrolysis of aluminum oxide dissolved in a molten cryolite bath into aluminum.
Referring to the accompanying drawing, an application in which the electrode of the present invention is used as an anode for manufacturing aluminum is explained.
Fig. 1 shows an example of the anode used in the method of the present invention. In Fig. 1, a conductive bar 1 is ' embedded in an anode base 2 made of a conductive material having ~ ' a melting point higher than electrolysis temperature, such as a -metal, an alloy, carbon or graphite. On a surface of the anode -base 2 a coating 3 of the electronic conductive oxide ceramics in accordance with thepresent invention is formed by an appropriate method to complete the anode. - ', In Fig. 2, an anode 4 is entirely made of the , electronic conductive oxide ceramics of the present in~ention, ' -iA which the conductive bar 1 is embedded to complete the anode. ~
' ,".
' 30 .
~69~6~
Fi~. 3 shows a schematlc diagram for conducting actual electrolysis while disposing the anode of the present invention in reduction cell. The reduction cell comprises an outer shell made of steel, a lining 5 of appropriate insulating material, and a lining 6 of carbonacious material, carbide, boride or the ceramics of the present invention. The molten aluminum precipitates at the bottom of molten electrolyte 9 and top surface of the molten electrolyte 9 is covered with a crust 10. The anode 4 of the present invention suspended from the conductive bar 1 is positioned in the molten electrolyte 9 to be appropriately spaced from the surface of the precipitated aluminum. The conductive bar 1 is movably connected to a bus bar 11.
With the electrolytic cell thus constructed, aluminum is separated as electric current is passed.
While the application to the anode has been illustrated, it should be understood that the electrode of the present invention may also used as a cathode for the aluminum reduction cell.
The anode used in the method according to the present invention has the following advantages over the prior art carbon anode; tl~ since the novel electrode of the present invention is not consumed unlike the prior art carbon anode, the replacement period may be set to more than several months, usually one hal~ to one year, thus the number of times for the replacement of the electrodes is considerably reduced, (2~ since it is not oxidation-consumed unlike the carbon anode, : ,.
. ' .
.. . . . .. ..
~L~69~6~
1 the frequency of adjus-ting the distance between the anode and the precipitated aluminum can be material-ly reduced thereby the electrolysis operation is simplified, manufacturing cost is reduced and the possibility of misoperation of the operator is mi.nimized.
Example 1 .
Powder of oxide mixture consisting of ~.
55.4 parts by weight of palladium oxide, 5.0 parts by weight of platinum oxide and 39.6 parts by weight of cobalt oxide was dry-blended in a ball mill for 15 hours and then formed by a rubber press under ; pressure (1000 kg/cm2), and sintered in a silicon . carbide resistor electric furnace at 90QC for 24 - 15 hours to prepare an electrode mainly consisting of~.
delafossite structure oxide OI PdCoO2, PtCoO2. The :.
-sintered anode was hard and solid and showed the : :
. .
conductivity of 100 Q 1 cm 1 at 1000C. ~hen, the ~ ~:
anode was drilled and copper was cast therein and :
20 a platinum ]ead wire was connected thereto to complete -:
an electrolysis anode. - ~. .
~ he anode prepared in the above manner was used with a cryolite bath mai.ntained at 950C
: ~ : and containing saturated aluminum oxide, and the ;
electrolysis was continuously conducted for 3 months a-t a current~density of lA/cm2 and voltage of 4.0 volts while sequ.entially adding alumlnum oxide. ~he decomposition voltage was 2.2 volts, which was close to a theoretlcal value and the overvoltage was low.
,~ ' .'.
~ ~ - 18 -..
.
- - . . . ... .. . .. .
1~69~6~
1 The current ef~iciency was 95% and it was observed that there occurred no corrosion o~ the anode during the electrolysis.
~xample 2 A titanium subs-trate, which had been fully cleaned, was palladium plated by alkaline aqueous solution including paliadium chloride while passing - current of 0.2 A/cm2 for 10 minutes. It was then dipped in aqueous solution of cobalt chloride and -cobalt plated at current density of 0.1 A/cm2 until the weight ratio of palladiurn to cobalt of 1.81 was attained. ~he titanium piece having two plated layers - thereon was oxidation-treated in a silicon carbide re-sistor electric furnace at 900C for 100 hours. To the resulting titanium piece having delafossite structure oxide coating of PdCoO2, a platinum lead wire was at-tached to complete an anode for the electrolysis.
The anode prepared in the above manner was used under the same conditions as in Exarnple 1 to conduct continuous electrolysis of alurninum oxide for 3 months. The decomposition voltage was 2.2 V, the current efficiency was 95% and there was no corrosion;and strip-off of the anode during the ,~ electrolysis.
Example 3 Powder of oxide rnixture consisting of 48.9 - parts by weight of lanthanum oxidej 45.1 parts by weight of tin oxide, 2.0 parts by weig~t ¢f zinc ~'.~' ~.:
4~1 1 oxide, 2.0 parts by weight of niobium oxide and 2.0 parts by weight of copper oxide was dry blended in a ball mill for 15 hours and then formed by a rubber press under pressure (1000 kg/cm2) and sintered in a silicon carbide resistor electric furnace at 1200C
for 24 hours to prepare an electrode mainly consis-t-ing of pyrochlore structure oxide of ~a2Sn207. The sintered anode was hard and solid and showed the conductivity o-f 1 Q 1 cm 1 at 1000C. Then the anode was drilled and copper was casted thereinto, and a platinum lead wire was connected to complete an anode for the electrolysis.
~ he anode thus constructed was used under the same conditions as in Bxample 1 to conduct con-tinuous electrolysis of aluminum oxide for ~ months.
~he decomposition voltage was 2~2 V, the current efficiency was 95% and there was no corrosion of the anode during the electrolysis.
,~
Example 4 Powder of oxide mixture consisting of 44.4 parts by weight of zirconium oxide, 3.7 parts by ~eight of germanium oxide, 48.9 parts by weight of tin oxide, 2~0 parts by weight of copper oxide and 1.0 parts by weight of indium oxide was dry blended in a ball mill for 15 hours and then formed by a ~- rubber press under pressure (200 kg/cm2) and sintered in a silicon carbide resistor electric furnace at ~ -1200C for 24 hours. The resulting sintered material of scheelite structure oxide mainly _ 20 -' ' ., :: . .. - :
6~
1 consisting of ZrGeO4, ZrSnO4 was milled by a vibrat-ing mill into particles of less than 5 ~. In a sepa-rate step, a titanium substrate 7 whieh had been fully cleaned, was platinum plated by aqueous solution of chloroplatinic acid while passing current of 0.05 ~/cm2 for 30 minutes. To the platinum plated titanium substrate, the milléd scheeli-te structure o~ide powder was applied by a plasma spray uni-t to eomplete an anode for the electrolysis.
The anode thus constructed was used under the same conditions as in ~xample 1 to conduct continuous electrolysis of aluminum oxide for 3 months. The decomposition voltage was 2.2 V, the current efficiency ~as 92%, and there was no appre-ciable corrosion and strip-off of the anode after the electrolysis.
' ~xample 5 Powder of oxide mixture eonsisting of 48.9 parts by weight of lanthanum oxide, 45.1 parts by weight of tin oxide, 2.0 parts by weight of ~inc oxide, 2.0 parts by weight o~ niobium oxide and 2.0 parts by weight of copper oxide was dry blended in a ball mill for 15 hours,-and then formed by an oil pressure press under pressure (200 kg/cm2) and pre-25 sintered in a silicon carbide resistor electric -furnaee at 1000C for 24 hours to produce a sintered -., - .
materlal, which was then milled into particles of less than 5 ~ size and -formed into a shape shown by 6 in Fig. 3 by a rubber press under pressure (1000 kg/cm2).
-~6~
1 Then it was sintered in the ~.ilicon carbide resi~tor electric furnace at 1200C for 40 hours to prepare a cathode mainly consisting of pyrochlore structure oxide of ~a2Sn207 .
The sintcred body was then drilled and copper was casted therein, which was then connected to a titanium rod to complete an cathode for the electrolysis.
The cathode thus constructed and a carbon anode were used with a cryolite bath maintained at 950a and containing saturated aluminum oxide to conduct the electrolysis of aluminum oxide continu-ously for one month at a current density of lA/cm2, voltage of 4.5 V while sequentially adding aluminum oxide and replacing the graphite anode at a ~ixed interval. The corrosion of the cathode by the electrolyte bath and the molten aluminum was not observed.
'.
Example 6 Powder of oxide mixture consisting of 53.6 parts by weight of lan-thanum oxide, 18.6 parts by ~
weight of yttrium oxide, 22.8 parts by weight of ~ :
indium oxide and 5.0 parts by weight of tantalum oxide was dry blended in a ball mill for 15 hours . 25 and then formed by a rubber press under pressure - (1000 kg/cm2) and sintered in a silicon carbide ~ :
resistor electric fur~ace at 1400C for 24 hours to prepare an electrode malnly consisting `of composite :..
- . -: . . - . . :
- - . . . -lL06~14G~
1 perovskite structure oxide of l.aYlInl03.
The sintered anode was hard and ~olid, and showed the conductivity of 1 Q~l cm 1 at 1000C. The anode was then drilled and copper was casted therein and a platlnum lead wire was connec-ted there-to to complete an anode for the electrolysis.
The anode thus constructed was used with a cryolite bath maintained at 950C and containing saturated aluminum oxide to conduct the electrolysis of the aluminum oxide at a current density of lA/cm2 and voltage of 4.0 V continuously for 3 months while sequentially adding aluminum oxide. The decomposi-tion voltage was 2.2 V which was close to a theore-tical value and the overvoltage was low. The current efficiency was 95%, and there was no corrosion of the anode during the electrolysisO
: ' `" ~' Example 7 ~ ~ Mixture cons3sting of 55.7 parts by weight i of lanthanum oxide, 17.1 parts by weight of nickel oxide, 25.2 parts by weight of tantalum pentoxide and 2.0 parts by weight o~ niobium pentoxide and a small amount of water~were wet blended in a ball mill for 24 hours~and sintered in a silicon carbide re-sistor electric furnace at 1300a for 24 hours. ~he sintered material was~milled into particles of less than 400 'raylor mesh size. The particles were then applied onto a nickel metal subs-trate by a plasma spray unit. In this~manner an anorle having a ~- - 23 ~ - ~
. . ~ . . .
..
- , , . . , . . - - - - . .. - , . .
- . . ~ . - - ~ . .. ... , .. - .. ~ . . . : . . -1 coating mainly consi.sting of composite perovskite structure oxide of ~a(Ni2Tal)03 on a nickel subst-rate was manufactured. The anode thus constructed was used with a cryolite bath maintained at 950C
and containing saturated aluminum oxide to conduct the electrolysis of aluminum oxide at a current density of 1 A/cm2 and voltage of 5.0 V continuously for one month while sequentially adding aluminum oxide. ~he decomposition voltage approximately corresponded to a theoretical valueO The current eficiency was 95% and there was no appreciable corrosion and strip-of of the anode coating after the electrolysis.
Example 8 ~ 15 A titanium substrate which had been fully - cleaned was platinum plated using aqueous bath of chloroplatlnic acid to prepare an anode base having i platinum coating layer.
On the surface of the above anode base, powder of composite perovskite structure of ~a(YlInl)03 manufactured in the same manner as EYample 1 was applled uslne a plasma spray device.
The titanium anode having the composite perovskite coating and the plat mum internal layer was then -used to continuously~conduct~the electrolysis of aluminum o~ide for one month. ~he decomposition ~ :
voltage was 2~2 V and -the current efficlency was 95%
- . ~ .
:
- 2L~ - ~
- : - - . i .: .,: , ,: . . , . : , , ~LO~9~
1 and there was no corrosion and strip-off of the anode during the electrolysis.
Example 9 Powder of o~ide mixture consisting of 65.4 parts by weight of tantalum pentoxide 9 2~.6 parts by weight of ferric oxide, 10~0 parts by weight of stannic oxide and 1.0 parts by weight of - -an-timony trioxide were dry blended in a ball mill for 15 hours, and then formed by a rubber press under pressure (1000 kg/cm2) and sintered in a high fre-quency induction heating furnace at 1450C for 5 hours to prepare an electrode mainly consisting of composite oxide having a structure of ~e203-Ta205.
The sintered anode was hard and solid and showed the 15 conductivity of 1.0 Q 1 cm 1 at 1000C. The anode ~
- was then drilled and copper was cast therein and a ~ --platinum lead wire was connected thereto to complete an anode for the elec-trolysis.
The anode thus constructed was used with a cryolite bath maintained at 950C and containing aluminum oxide to conduct continuous electrolysis for three months at a current density of 1 A/cm2 and voltage of 5.0 V while sequentially adding aluminum oxide. The decomposition voltage was 2.2 which approximately corresponded to a theoretical value and the overvoltage uas low. The current ef-ficiency was 90~0 and.there was no corrosion of the anode during the electrolysis.
,. ":, ', ~6~
1 Example 10 Powder of oxide mixture consisting of 70.8 parts by weight of tantalum pentoxide, 25.~ parts by weight of stannic oxide, 1.3 parts by weight of zinc oxide and 2.6 parts by weight of ferric oxide was wet blended in a ball mill for 15 hours and -then sintered in a silicon carbide resistor electric ~ur-nace at 1500C for 20 hours. The sintered product was milled into particles of less than 200 Taylor mesh size. The powder was then applied onto a nlckel substrate by a plasma spray device to prepare an anode having a coating mainly consisting of com-posite oxide having the structure of SnO2-Ta205.
The anode thus constructed was used with a cryolite bath maintained at 950a and containing saturated aluminum oxide to conduct con-tlnuous electrolysis of aluminum oxide for three months at a current denslty of 0.9 A/cm2 and voltage of 5.0 V while sequentially adding aluminum oxide.
The decomposition voltage was approximately equal to a theoretical value and the overvoltage was low.
There was no appreciable corrosion and strip-off of ~ the anode coating.
- Example 11 Powder of oxide mixture consisting of ~5.1 - parts by weight of niobium pentoxide, 45.9 parts by weight of tantalum pentoxidej 16.4 parts by weigh-t of nickel monoxide and 2.6 parts by weight of ferric .
oxide was used in the same manner as Example 1 to _ 26 -' .:
.
~6~61 1 prepare sintered a.nodes mainly consisting of compo-site oxide having the structure of NiO-Ta205 and NiO-Nb205-Powder of oxide mixture consisting of 72.5 parts by weight of lanthanum oxide, and 27.5 pa.rtsby weight. o zirconium oxide was milled in a ball mill for 10 hours and then sintered at lsooa for five hours and then milled in~o particles of less than 200 ~aylor mesh si~e. The pyrochlore structure composite oxide of ~a2Zr207 thus prepared was plasma sprayed on the above sintered anode except the bot~ . ;.
: tom surface thereof. In this manner, the anode made of NiO-Ta205 and ~iO.Nb205 having the coating o-f low , :. .
conductivity ~a2Zr207 on the sides thereof was pre~
pared. The similar electrolysis to that of ~xample 1 was conducted using the above anodes. ~here was :
no appreciable corrosion and resolution of the anode .~ base and the anode side and the decomposition voltage - ~
~- was approximately equal to the theoretical value and .~ : .
20 the overvoltage was low, and hence the excellent -property of non-consumable anode was proved. :.
Example 12 . Powder of oxide mixture consisting of 39.2 , . .
parts by weight of lanthanum oxide, 14.8 parts by 25 weight of zirconium oxide, 10.6 parts by weight of .
ferric oxide, 29.4 parts by weight of tantalum pentoxide, 5.0 parts by welght of tin oxide and 1.0 part by weigh1; o~antimony oxlde was:used in the same manner as Example 1 to prepare a sintered "' - - ~7 -.
.. . .. ., .. .. ... . . ~ .
~06~6~
1 anode mainly consisting of composite oxide having the structures of ~a203 ZrO2 and Fe203-Ta205- The anode thus constructed was used with a cryolite bath maintained at 950C and containing saturated aluminum oxide to conduct continuous electrolysis for three months at a current density of 0.9 A/cm2 and a voltage o-5.0 V while sequentially addin~ aluminum oxide.
The decomposi-tion voltage was approximately equal to a theoretical value and the overvoltage was low.
There was no appreciable corrosion and strip-off of the anode coating.
Example 13 Powder of the composite oxide having the structure of Fe20~.~a205 prepared in Example 9 was formed into a shape as shown by 6 in Fig. 3 by a rubber press under pressure (1000 kg/cm2). Then it was sintered in a high frequency induction heat- ~-ing furnace at 1500C for 24 hours to prepare a ; cathode mainly consisting of composite o~ide having the structure of Fe20~ Ta205. The sintered elect-rode was then drilled and copper was cast therein and a nickel rod was connected thereto to complete an cathode for the electrolysis.
The cathode thus constructed was used with a cryolite bath maintained~at 950C and containing saturated aluminum oxide and a carbon anode to conduct the electrolysis continuously for one month at a current~density of 1 A/cm2 and a voltage of 4.6 V while sequentially adding aluminum oxide and lO~
1 replacing the graphite anode at a fixed time interval.
~he corrosion of the cathode by the molten aluminum a~ter the electrolysis was observed to be slight.
.~:
~.,'~,.
:
- 29 - :
, "',' . '.
~69~
6. (Al) (A2)l(Bl)l(B2)l3 Al = Ag, Tl A2 = La, Y, Bi ¦ Bl = In, Al 7 Fe, Cr, Mn ~B2 = Ta, Nb .
1 Pre~erably, a perovskite structure composite oxide such as ~a(Ni2Ta )03, La(Ni2Nb )03, ~a(Pd2Tal)03, ~a(Pd2Nbl)03, Y(Ni2~al)03, Y(Ni2Nbl)03, Y(Pd2Ta )03, Y(Pd2~bl)03, Bi(Ni2Tal)03, ~i(NilZr )03, La(NilPtl)03, (Ni Ptl)03, La(InlY )03, ~a(In Al )03, La(Pd1Snl)03, Y(Pd Snl)03, ~i(Pd Snl)03, (Ag1Bi )ZrO3, (Ag_Y_)SnO3, (AglLal)(InlTal)3~ (Agl~il)(InlNbl) 3, 1 1 3 ~a(Yl~nl)03, 1a(Fe1Inl)03, La(Fel~ 1)03 may be select-ed. The oxides represented by the general formulas x y Ta205 and AxOy-Nb205 lnclude CoO-Ta205, ~oO-~b205, NiO-Ta205, NiO-Nb205~ ZnO Ta205, ZnO Nb205~ ~ ' SnO Ta205, SnO Nb205, FeO Ta205~ ~eO Nb205~ Fe23 Ta23 Fe203-Nb205~ Cr23-Ta205~Cr203 Nb205, 2 3 2 5 ~: ~ A123 ~b25~ In2o3 Ta2o5~In2o3.~b2o5~ 2 2 5 2 ~b25~ Ti2 Ta2st~Ti2-Nb205~ ZrO2-Ta O
2rO2-Nb205. (While pure composit~e oxide such as A1203-Ta205 usually has B low electronic~conductivity and it is difficul-t to use it as an electronic ; -:
.
' - 11 - :
6~L
conductive material, it may be ~endered hi~hl~ conductive by having certain constituent added thereto~ Since it is a common practice to represent such a conductivity-imparted oxide by A1~03.Ta205, it is represented herein in accordance with the common practice.) The oxides of the present invention as represented by the general formulas XY02, X2Y207, XY04, { ~ (~i)XA~ ~ ~ (Bj)XBj} 03, AXy'Ta2S and AxOy.Nb205 are electronic conductive and are different from the known ion-conductive electrode in their electro-conductive modes and also different from a tin oxide electrode in their crystal structures and hence they provide an electrode of a novel composi-tion. The electrode made of such electronic conductive oxide ceramics exhibits excellent effect of high conductivity under electrolysis conduction and high resistance to a molten salt bath containing cryolite as main component~
The electrode used in the method of the present invention is prepared by forming at leas~ that portion thereof which is ; 20 brought into contact with the molten salt by composition includ-ing at least 50% by weight, preferably at least 75% by weight of an oxide selected from those represented by XY02, X2Y207, XY04, (Ai ) X ~ ~ ~ (B j ) XB~3 03~ AxOy Ta2 5' x y 2 5 .
mixture thereof.
In the manufacture of the electrode used in the method ' ~ -12-4 ~
1 the present invention, in order to enhance the density of the electrode, heat resistance, thermal-shock resistance, resistance to molten bath, and elec-tric conductivity, spinel structure oxide or perovskite structure may be mixed to the electronic conductive oxide ceramics, as required. The content of the addi-ti~e is usually not more than 50% by weight 9 and oxides, carbides, nitrides, borides and silicides of alkali metals, alkaline earth metals, transition metals, platinum group metals and rare earth elements may be mixed thereto as required. The amount of such additives is usually not more than 50% by weight because the elec-tric conductivity~ resistance to bath and resistance to oxidation are deteriorated above 50% by ~eight. ~he particularly preferred additives are oxides of transition metals such as manganese oxide, nickel oxide, cobalt oxide and iron oxide, or oxides of platinum group metals such as ruthenium oxide, palladium oxide, platinum oxide, rhodium oxide and iridium oxide, or oxides of rare earth elements such as yttrium oxide, cerium oxide, neodymium oxide and lanthanum oxide, or titanium nitride, tita-nium boride, lanthanum boride, zirconium boride and :
tungsten silicide.
~n optimum condition for the electrical resistance of the electronic conductiue oxide ceramics used for the electrode depends on the shape of the -electrode, that is, the thickness of the coating, and the material thereof preferably has the con-ductivity o at least about 0.1 Q 1 cm 1 (at loooa ) .
- .. - , ; . ~ . . . . :. : : .
- - . . : :: : - , . . : -~ ~ ', . A
The electronic conductive oxide ceramics for coating or forming the electrode o~ the present invention has a melting point higher than the operating temperature of an electrolytic cell, usually at or higher than about 1000C and preferably at or higher than 1200DC.
The electrode used in the method of the present inven-tion may be prepared by forming a coating including the above oxide ceramics on a surface of an electrode base of a conductive .
material such as a metal or alloy e.g. titanium, nickel or copper, carbon, graphite or such as a carbide, nitride, boride, or silicide of titanium, molybdenum or tungsten, or the electrode may be entirely made of the composition including the above ~ oxide cera~ics.
; In coating the surface of the electrode with the oxide ceramics, the composition including the composition as represented by the general formula XYO2, X2Y2O7, XYO4, ~ ~l( ) Ai ~ Bi)XB~} 3' AXOy-Ta2O5 or AXOy.Nb2O5 may be flame sprayed or plasma sprayed and then heat treated as - .
20 . required, or it may be electroplated. Alternatively, inorganic ~:
or organic metal compounds which may form the oxide or the above , structure when it is sintered may be applied, dipped, sprayed : or deposited by thermal decomposition,followed by sintering, .
or an electrode base made of an alloy which forms the oxide of the above structure when it is oxidized or an electrode base , ~ coated with such an alloy is prepared and then ' ;' '`
. .
: . ' :
~ 30 ;~ ;
, ~.
1~6946~
it is oxidized. It should be understood that in coating the electrode base with the oxide ceramics, an internal layer of an oxide of platinum group metal may be provided therebetween to enhance the adhesiveness of the oxide ceramics to the base.
In practicing the present invention, the oxide as represented by the general formula XYO2, X2Y2O7, XYO4, ~ ~ (Ai)XAil ~ ~ (Bj)XBj~ 3~ Axy-Ta2s~ or AxOy-Nb2O5 may be preferably prepared by sintering a mixture of appropriate composition such as oxide, hydroxide, chloride, sulfate, nitrate, carbonate or oxalate of said metal, usually at 500C or higher and preferably at 800C - 2500C. The sintering may be conducted in a high frequency induction heating furnace or a resistance heating furnace at 500C or higher and preferably at 800 - 2500C under reduced pressure, atmospheric pr~ssure or elevated pressure and preferably by hot pressing under 50 - lO00 kg/c 2 .
When the electrode is used in an aluminum reduction cell, the connection between the electrode and a conductor stud .
need not be specified but conventional means may be used. That -is, the connection by threading, welding, molding or casting may be used or the connection may be made through a low melting point metal such as aluminum, tin or copper, or alloy or metal-lic compound thereof.
For uniformity of voltage and reduction .'~ ~ ;.
- :' ; ~3694~;~
in corrosion o~ the sur,face, i~ :is use,ful to coat the surface of the non consumable anode o~ the present invention, except ~ -that portion thereof required to make the electric current to flow, with an anti-corrosi~e insulating material such as 2' 24~ MgA12O4, LaAlO3 or La2Zr2O7~
The most general use of the non-consumable electrode of the present invention thus obtained is to replace convention-al carbon electrode at least in its portion in contact with the molten salt bath in the electrolysis of aluminum oxide dissolved in a molten cryolite bath into aluminum.
Referring to the accompanying drawing, an application in which the electrode of the present invention is used as an anode for manufacturing aluminum is explained.
Fig. 1 shows an example of the anode used in the method of the present invention. In Fig. 1, a conductive bar 1 is ' embedded in an anode base 2 made of a conductive material having ~ ' a melting point higher than electrolysis temperature, such as a -metal, an alloy, carbon or graphite. On a surface of the anode -base 2 a coating 3 of the electronic conductive oxide ceramics in accordance with thepresent invention is formed by an appropriate method to complete the anode. - ', In Fig. 2, an anode 4 is entirely made of the , electronic conductive oxide ceramics of the present in~ention, ' -iA which the conductive bar 1 is embedded to complete the anode. ~
' ,".
' 30 .
~69~6~
Fi~. 3 shows a schematlc diagram for conducting actual electrolysis while disposing the anode of the present invention in reduction cell. The reduction cell comprises an outer shell made of steel, a lining 5 of appropriate insulating material, and a lining 6 of carbonacious material, carbide, boride or the ceramics of the present invention. The molten aluminum precipitates at the bottom of molten electrolyte 9 and top surface of the molten electrolyte 9 is covered with a crust 10. The anode 4 of the present invention suspended from the conductive bar 1 is positioned in the molten electrolyte 9 to be appropriately spaced from the surface of the precipitated aluminum. The conductive bar 1 is movably connected to a bus bar 11.
With the electrolytic cell thus constructed, aluminum is separated as electric current is passed.
While the application to the anode has been illustrated, it should be understood that the electrode of the present invention may also used as a cathode for the aluminum reduction cell.
The anode used in the method according to the present invention has the following advantages over the prior art carbon anode; tl~ since the novel electrode of the present invention is not consumed unlike the prior art carbon anode, the replacement period may be set to more than several months, usually one hal~ to one year, thus the number of times for the replacement of the electrodes is considerably reduced, (2~ since it is not oxidation-consumed unlike the carbon anode, : ,.
. ' .
.. . . . .. ..
~L~69~6~
1 the frequency of adjus-ting the distance between the anode and the precipitated aluminum can be material-ly reduced thereby the electrolysis operation is simplified, manufacturing cost is reduced and the possibility of misoperation of the operator is mi.nimized.
Example 1 .
Powder of oxide mixture consisting of ~.
55.4 parts by weight of palladium oxide, 5.0 parts by weight of platinum oxide and 39.6 parts by weight of cobalt oxide was dry-blended in a ball mill for 15 hours and then formed by a rubber press under ; pressure (1000 kg/cm2), and sintered in a silicon . carbide resistor electric furnace at 90QC for 24 - 15 hours to prepare an electrode mainly consisting of~.
delafossite structure oxide OI PdCoO2, PtCoO2. The :.
-sintered anode was hard and solid and showed the : :
. .
conductivity of 100 Q 1 cm 1 at 1000C. ~hen, the ~ ~:
anode was drilled and copper was cast therein and :
20 a platinum ]ead wire was connected thereto to complete -:
an electrolysis anode. - ~. .
~ he anode prepared in the above manner was used with a cryolite bath mai.ntained at 950C
: ~ : and containing saturated aluminum oxide, and the ;
electrolysis was continuously conducted for 3 months a-t a current~density of lA/cm2 and voltage of 4.0 volts while sequ.entially adding alumlnum oxide. ~he decomposition voltage was 2.2 volts, which was close to a theoretlcal value and the overvoltage was low.
,~ ' .'.
~ ~ - 18 -..
.
- - . . . ... .. . .. .
1~69~6~
1 The current ef~iciency was 95% and it was observed that there occurred no corrosion o~ the anode during the electrolysis.
~xample 2 A titanium subs-trate, which had been fully cleaned, was palladium plated by alkaline aqueous solution including paliadium chloride while passing - current of 0.2 A/cm2 for 10 minutes. It was then dipped in aqueous solution of cobalt chloride and -cobalt plated at current density of 0.1 A/cm2 until the weight ratio of palladiurn to cobalt of 1.81 was attained. ~he titanium piece having two plated layers - thereon was oxidation-treated in a silicon carbide re-sistor electric furnace at 900C for 100 hours. To the resulting titanium piece having delafossite structure oxide coating of PdCoO2, a platinum lead wire was at-tached to complete an anode for the electrolysis.
The anode prepared in the above manner was used under the same conditions as in Exarnple 1 to conduct continuous electrolysis of alurninum oxide for 3 months. The decomposition voltage was 2.2 V, the current efficiency was 95% and there was no corrosion;and strip-off of the anode during the ,~ electrolysis.
Example 3 Powder of oxide rnixture consisting of 48.9 - parts by weight of lanthanum oxidej 45.1 parts by weight of tin oxide, 2.0 parts by weig~t ¢f zinc ~'.~' ~.:
4~1 1 oxide, 2.0 parts by weight of niobium oxide and 2.0 parts by weight of copper oxide was dry blended in a ball mill for 15 hours and then formed by a rubber press under pressure (1000 kg/cm2) and sintered in a silicon carbide resistor electric furnace at 1200C
for 24 hours to prepare an electrode mainly consis-t-ing of pyrochlore structure oxide of ~a2Sn207. The sintered anode was hard and solid and showed the conductivity o-f 1 Q 1 cm 1 at 1000C. Then the anode was drilled and copper was casted thereinto, and a platinum lead wire was connected to complete an anode for the electrolysis.
~ he anode thus constructed was used under the same conditions as in Bxample 1 to conduct con-tinuous electrolysis of aluminum oxide for ~ months.
~he decomposition voltage was 2~2 V, the current efficiency was 95% and there was no corrosion of the anode during the electrolysis.
,~
Example 4 Powder of oxide mixture consisting of 44.4 parts by weight of zirconium oxide, 3.7 parts by ~eight of germanium oxide, 48.9 parts by weight of tin oxide, 2~0 parts by weight of copper oxide and 1.0 parts by weight of indium oxide was dry blended in a ball mill for 15 hours and then formed by a ~- rubber press under pressure (200 kg/cm2) and sintered in a silicon carbide resistor electric furnace at ~ -1200C for 24 hours. The resulting sintered material of scheelite structure oxide mainly _ 20 -' ' ., :: . .. - :
6~
1 consisting of ZrGeO4, ZrSnO4 was milled by a vibrat-ing mill into particles of less than 5 ~. In a sepa-rate step, a titanium substrate 7 whieh had been fully cleaned, was platinum plated by aqueous solution of chloroplatinic acid while passing current of 0.05 ~/cm2 for 30 minutes. To the platinum plated titanium substrate, the milléd scheeli-te structure o~ide powder was applied by a plasma spray uni-t to eomplete an anode for the electrolysis.
The anode thus constructed was used under the same conditions as in ~xample 1 to conduct continuous electrolysis of aluminum oxide for 3 months. The decomposition voltage was 2.2 V, the current efficiency ~as 92%, and there was no appre-ciable corrosion and strip-off of the anode after the electrolysis.
' ~xample 5 Powder of oxide mixture eonsisting of 48.9 parts by weight of lanthanum oxide, 45.1 parts by weight of tin oxide, 2.0 parts by weight of ~inc oxide, 2.0 parts by weight o~ niobium oxide and 2.0 parts by weight of copper oxide was dry blended in a ball mill for 15 hours,-and then formed by an oil pressure press under pressure (200 kg/cm2) and pre-25 sintered in a silicon carbide resistor electric -furnaee at 1000C for 24 hours to produce a sintered -., - .
materlal, which was then milled into particles of less than 5 ~ size and -formed into a shape shown by 6 in Fig. 3 by a rubber press under pressure (1000 kg/cm2).
-~6~
1 Then it was sintered in the ~.ilicon carbide resi~tor electric furnace at 1200C for 40 hours to prepare a cathode mainly consisting of pyrochlore structure oxide of ~a2Sn207 .
The sintcred body was then drilled and copper was casted therein, which was then connected to a titanium rod to complete an cathode for the electrolysis.
The cathode thus constructed and a carbon anode were used with a cryolite bath maintained at 950a and containing saturated aluminum oxide to conduct the electrolysis of aluminum oxide continu-ously for one month at a current density of lA/cm2, voltage of 4.5 V while sequentially adding aluminum oxide and replacing the graphite anode at a ~ixed interval. The corrosion of the cathode by the electrolyte bath and the molten aluminum was not observed.
'.
Example 6 Powder of oxide mixture consisting of 53.6 parts by weight of lan-thanum oxide, 18.6 parts by ~
weight of yttrium oxide, 22.8 parts by weight of ~ :
indium oxide and 5.0 parts by weight of tantalum oxide was dry blended in a ball mill for 15 hours . 25 and then formed by a rubber press under pressure - (1000 kg/cm2) and sintered in a silicon carbide ~ :
resistor electric fur~ace at 1400C for 24 hours to prepare an electrode malnly consisting `of composite :..
- . -: . . - . . :
- - . . . -lL06~14G~
1 perovskite structure oxide of l.aYlInl03.
The sintered anode was hard and ~olid, and showed the conductivity of 1 Q~l cm 1 at 1000C. The anode was then drilled and copper was casted therein and a platlnum lead wire was connec-ted there-to to complete an anode for the electrolysis.
The anode thus constructed was used with a cryolite bath maintained at 950C and containing saturated aluminum oxide to conduct the electrolysis of the aluminum oxide at a current density of lA/cm2 and voltage of 4.0 V continuously for 3 months while sequentially adding aluminum oxide. The decomposi-tion voltage was 2.2 V which was close to a theore-tical value and the overvoltage was low. The current efficiency was 95%, and there was no corrosion of the anode during the electrolysisO
: ' `" ~' Example 7 ~ ~ Mixture cons3sting of 55.7 parts by weight i of lanthanum oxide, 17.1 parts by weight of nickel oxide, 25.2 parts by weight of tantalum pentoxide and 2.0 parts by weight o~ niobium pentoxide and a small amount of water~were wet blended in a ball mill for 24 hours~and sintered in a silicon carbide re-sistor electric furnace at 1300a for 24 hours. ~he sintered material was~milled into particles of less than 400 'raylor mesh size. The particles were then applied onto a nickel metal subs-trate by a plasma spray unit. In this~manner an anorle having a ~- - 23 ~ - ~
. . ~ . . .
..
- , , . . , . . - - - - . .. - , . .
- . . ~ . - - ~ . .. ... , .. - .. ~ . . . : . . -1 coating mainly consi.sting of composite perovskite structure oxide of ~a(Ni2Tal)03 on a nickel subst-rate was manufactured. The anode thus constructed was used with a cryolite bath maintained at 950C
and containing saturated aluminum oxide to conduct the electrolysis of aluminum oxide at a current density of 1 A/cm2 and voltage of 5.0 V continuously for one month while sequentially adding aluminum oxide. ~he decomposition voltage approximately corresponded to a theoretical valueO The current eficiency was 95% and there was no appreciable corrosion and strip-of of the anode coating after the electrolysis.
Example 8 ~ 15 A titanium substrate which had been fully - cleaned was platinum plated using aqueous bath of chloroplatlnic acid to prepare an anode base having i platinum coating layer.
On the surface of the above anode base, powder of composite perovskite structure of ~a(YlInl)03 manufactured in the same manner as EYample 1 was applled uslne a plasma spray device.
The titanium anode having the composite perovskite coating and the plat mum internal layer was then -used to continuously~conduct~the electrolysis of aluminum o~ide for one month. ~he decomposition ~ :
voltage was 2~2 V and -the current efficlency was 95%
- . ~ .
:
- 2L~ - ~
- : - - . i .: .,: , ,: . . , . : , , ~LO~9~
1 and there was no corrosion and strip-off of the anode during the electrolysis.
Example 9 Powder of o~ide mixture consisting of 65.4 parts by weight of tantalum pentoxide 9 2~.6 parts by weight of ferric oxide, 10~0 parts by weight of stannic oxide and 1.0 parts by weight of - -an-timony trioxide were dry blended in a ball mill for 15 hours, and then formed by a rubber press under pressure (1000 kg/cm2) and sintered in a high fre-quency induction heating furnace at 1450C for 5 hours to prepare an electrode mainly consisting of composite oxide having a structure of ~e203-Ta205.
The sintered anode was hard and solid and showed the 15 conductivity of 1.0 Q 1 cm 1 at 1000C. The anode ~
- was then drilled and copper was cast therein and a ~ --platinum lead wire was connected thereto to complete an anode for the elec-trolysis.
The anode thus constructed was used with a cryolite bath maintained at 950C and containing aluminum oxide to conduct continuous electrolysis for three months at a current density of 1 A/cm2 and voltage of 5.0 V while sequentially adding aluminum oxide. The decomposition voltage was 2.2 which approximately corresponded to a theoretical value and the overvoltage uas low. The current ef-ficiency was 90~0 and.there was no corrosion of the anode during the electrolysis.
,. ":, ', ~6~
1 Example 10 Powder of oxide mixture consisting of 70.8 parts by weight of tantalum pentoxide, 25.~ parts by weight of stannic oxide, 1.3 parts by weight of zinc oxide and 2.6 parts by weight of ferric oxide was wet blended in a ball mill for 15 hours and -then sintered in a silicon carbide resistor electric ~ur-nace at 1500C for 20 hours. The sintered product was milled into particles of less than 200 Taylor mesh size. The powder was then applied onto a nlckel substrate by a plasma spray device to prepare an anode having a coating mainly consisting of com-posite oxide having the structure of SnO2-Ta205.
The anode thus constructed was used with a cryolite bath maintained at 950a and containing saturated aluminum oxide to conduct con-tlnuous electrolysis of aluminum oxide for three months at a current denslty of 0.9 A/cm2 and voltage of 5.0 V while sequentially adding aluminum oxide.
The decomposition voltage was approximately equal to a theoretical value and the overvoltage was low.
There was no appreciable corrosion and strip-off of ~ the anode coating.
- Example 11 Powder of oxide mixture consisting of ~5.1 - parts by weight of niobium pentoxide, 45.9 parts by weight of tantalum pentoxidej 16.4 parts by weigh-t of nickel monoxide and 2.6 parts by weight of ferric .
oxide was used in the same manner as Example 1 to _ 26 -' .:
.
~6~61 1 prepare sintered a.nodes mainly consisting of compo-site oxide having the structure of NiO-Ta205 and NiO-Nb205-Powder of oxide mixture consisting of 72.5 parts by weight of lanthanum oxide, and 27.5 pa.rtsby weight. o zirconium oxide was milled in a ball mill for 10 hours and then sintered at lsooa for five hours and then milled in~o particles of less than 200 ~aylor mesh si~e. The pyrochlore structure composite oxide of ~a2Zr207 thus prepared was plasma sprayed on the above sintered anode except the bot~ . ;.
: tom surface thereof. In this manner, the anode made of NiO-Ta205 and ~iO.Nb205 having the coating o-f low , :. .
conductivity ~a2Zr207 on the sides thereof was pre~
pared. The similar electrolysis to that of ~xample 1 was conducted using the above anodes. ~here was :
no appreciable corrosion and resolution of the anode .~ base and the anode side and the decomposition voltage - ~
~- was approximately equal to the theoretical value and .~ : .
20 the overvoltage was low, and hence the excellent -property of non-consumable anode was proved. :.
Example 12 . Powder of oxide mixture consisting of 39.2 , . .
parts by weight of lanthanum oxide, 14.8 parts by 25 weight of zirconium oxide, 10.6 parts by weight of .
ferric oxide, 29.4 parts by weight of tantalum pentoxide, 5.0 parts by welght of tin oxide and 1.0 part by weigh1; o~antimony oxlde was:used in the same manner as Example 1 to prepare a sintered "' - - ~7 -.
.. . .. ., .. .. ... . . ~ .
~06~6~
1 anode mainly consisting of composite oxide having the structures of ~a203 ZrO2 and Fe203-Ta205- The anode thus constructed was used with a cryolite bath maintained at 950C and containing saturated aluminum oxide to conduct continuous electrolysis for three months at a current density of 0.9 A/cm2 and a voltage o-5.0 V while sequentially addin~ aluminum oxide.
The decomposi-tion voltage was approximately equal to a theoretical value and the overvoltage was low.
There was no appreciable corrosion and strip-off of the anode coating.
Example 13 Powder of the composite oxide having the structure of Fe20~.~a205 prepared in Example 9 was formed into a shape as shown by 6 in Fig. 3 by a rubber press under pressure (1000 kg/cm2). Then it was sintered in a high frequency induction heat- ~-ing furnace at 1500C for 24 hours to prepare a ; cathode mainly consisting of composite o~ide having the structure of Fe20~ Ta205. The sintered elect-rode was then drilled and copper was cast therein and a nickel rod was connected thereto to complete an cathode for the electrolysis.
The cathode thus constructed was used with a cryolite bath maintained~at 950C and containing saturated aluminum oxide and a carbon anode to conduct the electrolysis continuously for one month at a current~density of 1 A/cm2 and a voltage of 4.6 V while sequentially adding aluminum oxide and lO~
1 replacing the graphite anode at a fixed time interval.
~he corrosion of the cathode by the molten aluminum a~ter the electrolysis was observed to be slight.
.~:
~.,'~,.
:
- 29 - :
Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for producing aluminum by molten salt electrolysis of aluminum oxide which comprises electrolyzing aluminum oxide dissolved in a molten salt containing aluminum sodium fluoride as main component by passing a direct current from an anode to a cathode disposed in said molten salt, wherein at least a portion of at least one of said anode and said cathode that is brought into contact with said molten salt is made of or covered with a composition which includes at least about 50%
by weight of electronic conductive oxide ceramics selected from one or a combination of oxides represented by general formulas XYO2 (wherein X is a monovalent metal, Y is a trivalent metal and O is an oxygen atom); X2Y207 (wherein X is a trivalent metal, Y is a tetravalent metal and O is an oxygen atom); XYO4 (wherein X is a trivalent or tetravalent metal, Y is a pentavalent or tetravalent metal and O is an oxygen atom, and when X is a tri-valent metal then Y is selected from pentavalent metals, and when X is a tetravalent metal then Y is selected from tetravalent metals); (where Ai and Bj are metal atoms, XAi and XBj are molar fractions of Ai and Bj constituents, respectively, O is an oxygen atom, k and ? represent the numbers of metal constituents constituting Ai and Bj, respectively and constituent ions at positions A and B meet the requirements of , , 0<XAi?1, 0<XBj?1 wherein if XAi = 1 then 0<XBj<1 and if XBj = 1 then 0<XAi<1), , ?B, ?A + ?B = 6, , , 0.8 1.1 [wherein XAi and XBj are molar fractions of the atoms, nAi and nBj are valences of the atoms, rAi and rBj are ion radii of the atoms, and ro is ion radius of oxygen)]; AxOy?Ta205 (wherein A is a divalent, tri-valent or tetravalent metal, O is an oxygen atom, and when A is a divalent metal, then x=y=1, when A is a trivalent metal, then x=2, y=3, and when A is a tetravalent metal, then x=1, y=2);
and AxOy?Nb205 (wherein A is a divalent, trivalent or tetra-valent metal, O is an oxygen atom and when A is a divalent metal, then x-y=1, and when A is a trivalent metal, then x=2, y=3, and when A is a tetravalent metal, then x=1, y=2), and up to 50%
by weight of an additive selected from oxides, carbides, nitrides, borides and silicides of alkali metals, alkaline earth metals, transition metals, platinum group metals and rare earth elements.
by weight of electronic conductive oxide ceramics selected from one or a combination of oxides represented by general formulas XYO2 (wherein X is a monovalent metal, Y is a trivalent metal and O is an oxygen atom); X2Y207 (wherein X is a trivalent metal, Y is a tetravalent metal and O is an oxygen atom); XYO4 (wherein X is a trivalent or tetravalent metal, Y is a pentavalent or tetravalent metal and O is an oxygen atom, and when X is a tri-valent metal then Y is selected from pentavalent metals, and when X is a tetravalent metal then Y is selected from tetravalent metals); (where Ai and Bj are metal atoms, XAi and XBj are molar fractions of Ai and Bj constituents, respectively, O is an oxygen atom, k and ? represent the numbers of metal constituents constituting Ai and Bj, respectively and constituent ions at positions A and B meet the requirements of , , 0<XAi?1, 0<XBj?1 wherein if XAi = 1 then 0<XBj<1 and if XBj = 1 then 0<XAi<1), , ?B, ?A + ?B = 6, , , 0.8 1.1 [wherein XAi and XBj are molar fractions of the atoms, nAi and nBj are valences of the atoms, rAi and rBj are ion radii of the atoms, and ro is ion radius of oxygen)]; AxOy?Ta205 (wherein A is a divalent, tri-valent or tetravalent metal, O is an oxygen atom, and when A is a divalent metal, then x=y=1, when A is a trivalent metal, then x=2, y=3, and when A is a tetravalent metal, then x=1, y=2);
and AxOy?Nb205 (wherein A is a divalent, trivalent or tetra-valent metal, O is an oxygen atom and when A is a divalent metal, then x-y=1, and when A is a trivalent metal, then x=2, y=3, and when A is a tetravalent metal, then x=1, y=2), and up to 50%
by weight of an additive selected from oxides, carbides, nitrides, borides and silicides of alkali metals, alkaline earth metals, transition metals, platinum group metals and rare earth elements.
2. A method according to claim 1, wherein at least that portion of the electrode base which is brought into contact with the molten salt bath is coated with the composition includ-ing at least about 50% by weight of electronic conductive oxide ceramics.
3. A method according to claim 1, wherein at least that portion of the electrode which is brought into contact with the molten salt bath is entirely made of the composition includ-ing at least about 50% by weight of electronic conductive oxide ceramics.
4. A method according to claim 1, wherein said compo-sition includes at least 75% by weight of electronic conductive oxide ceramics.
5. A method according to Claim 1, where-in conductivity of the electronic conductive oxide ceramics is at least 0.1 .OMEGA.-1 cm-1 at 1000°C.
6. A method according to Claim 1, where-in melting point of the electronic conductive oxide ceramics is at or above 1200°C.
7. A method according to Claim 1, wherein the electronic conductive oxide ceramics is a de-lafossite structure oxide selected from the group consisting of PtCoO2, PtRhO2, PdCoO2, PdRhO2, PdNiO2, AgInO2, AgCoO2 and AgRhO2.
8. A method according to Claim 1, wherein the electronic conductive oxides ceramics is a pyrochlore structure oxide selected from the group consisting of Bi2Rh2O7, Bi2Ir2O7, Bi2Ru2O7, BiSn2O7, La2Ti2O7, La2Ir2O7, La2Sn2O7, La2Zr2O7, La2Ge2O7, La2Ru2O7, La2Os2O7, Y2Ti2O7, Y2Hf2O7, Y2Sn2O7, Y2Zr2O7, Y2Ge2O7, Y2Ru2O7, Y2Os2O7, Y2Ir2O7, Ce2Ti2O7, Ce2Sn2O7, Ce2Zr2O7, Ce2Ge2O7, Ce2Ru2O7, Ce2Os2O7, Ce2Hf2O7, Ce2Ir2O7, In2Ge2O7, In2Sn2O7, La2Pt2O7, Y2Pt2O7, Pr2Zr2O7, Pr2Sn2O7, Nd2Zr2O7, Nd2Sn2O7, Sm2Zr2O7, and Sn2Sm2O7.
9. A method according to Claim 1, wherein the electronic conductive oxides ceramics is a scheelite structure oxide selected from the group consisting of ZrGeO4, ThGeO4, ZrSnO4, LaTaO4, LaNbO4, YTaO4 and YNbO4.
10. A method according to Claim 1, wherein the electronic conductive oxide ceramics is a compo-site perovskite structure oxide selected from the group consisting of La(Ni?Ta?)O3, La(Ni?Nb?)O3, La(Pd?Ta?)O3, La(Pd?Nb?)O3, Y(Ni?Ta?)O3, Y(Ni?Nb?)O3, Y(Pd?Ta?)O3, Y(Pd?Nb?)O3, Bi(Ni?Ta?)O3, Bi(Ni?Zr?)O3, La(Ni?Pt?)O3, Y(Ni?Pt?)O3, La(In?Y?)O3, La(In?Al?)O3, La(Pd?Sn?)O3, Y(Pd?Sn?)O3, Bi(Pd?Sn?)O3, (Ag?Bi?)ZrO3, (Ag?Y?)SnO3, (Ag?La?)(In?Ta?)O3, (Ag?Bi?)(In?Nb?)O3, La(Y?Fe?)O3, La(Y?Mn?)O3, La(Fe?In?)O3 and La(Fe?Mn?)O3.
11. A method according to Claim 1, wherein the electronic conductive oxide ceramics is a rutile structure oxide selected from the group consisting of CoO?Ta2O5, NiO?Ta2O5, ZnO?Ta2O5, SnO?Ta2O5, FeO?Ta2O5, Fe2O3?Ta2O5, Cr2O3?Ta2O5, Al2O3?Ta2O5, In2O3?Ta2O5, SnO2?Ta2O5, TiO2?Ta2O5 and ZrO2?Ta2O5.
12. A method according to Claim 17 wherein the electronic conductive oxide ceramics is a columbite structure oxide selected from the group consisting of CoO?Nb2O5, NiO?Nb2O5, ZnO?Nb2O5, SnO?Nb2O5, FeO?Nb2O5, Fe2O3?Nb2O5, Cr2O3?Nb2O5, Al2O3?Nb2O5, In2O3?Nb2O5, SnO2?Nb2O5, TiO2?Nb2O5 and ZrO2?Nb2O5.
13. A method according to Claim 1, wherein the electronic conductive oxide ceramics is selected from delafossite structure oxides including PdCoO2, PtCoO2, pyrochlore structure oxides including La2Sn207, La2Zr207, scheelite structure oxides including ZrGe04, ZrSn04, composite perovskite struc-ture oxides including LaY?In?03, LaNi?Ta?0, rutile structure oxides including Fe203?Ta205, NiO?Ta205 and Sn02?Ta205, columbite structure oxides including NiO?Nb205 and mixture thereof.
14. A method according to Claim 13, wherein platinum oxide, zinc oxide, niobium oxide, copper oxide, indium oxide, tantalum oxide, antimony oxide, ferric oxide or tin oxide is added to the electronic conductive oxide ceramics as an additive.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP49122916A JPS5148708A (en) | 1974-10-23 | 1974-10-23 | Aruminiumuno denkaiseizonimochiirudenkyoku |
| JP5501575A JPS51129807A (en) | 1975-05-07 | 1975-05-07 | Electrodes for electrolytic production of aluminium |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1069461A true CA1069461A (en) | 1980-01-08 |
Family
ID=26395842
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA238,051A Expired CA1069461A (en) | 1974-10-23 | 1975-10-21 | Electrodes for aluminum reduction cells |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1069461A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116334695A (en) * | 2023-02-20 | 2023-06-27 | 郑州机械研究所有限公司 | Method for preparing silver-copper composite material by fused salt electrolysis and silver-copper composite material |
-
1975
- 1975-10-21 CA CA238,051A patent/CA1069461A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116334695A (en) * | 2023-02-20 | 2023-06-27 | 郑州机械研究所有限公司 | Method for preparing silver-copper composite material by fused salt electrolysis and silver-copper composite material |
| CN116334695B (en) * | 2023-02-20 | 2025-07-18 | 中国机械总院集团郑州机械研究所有限公司 | Method for preparing silver-copper composite material by fused salt electrolysis and silver-copper composite material |
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