Sintered refractory block based on silicon carbide with a silicon nitride bond
AssigneeSaint-Gobain Centre De Recherches Et D'Etudes Europeen
InventorsEric Jorge, Olivier Marguin
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Abstract
A sintered refractory block based on silicon carbide (SiC) with a silicon nitride (Si3N4) bond, for the manufacture of a aluminium electrolysis vessel, characterized in that it comprises, expressed in percentage by weight, at least 0.05% boron and/or between 0.05 and 1.2% calcium.
Claims25
A refractory block based on silicon carbide (SiC) reactively sintered between 1100° C. and 1700° C. to form a silicon nitride binder (Si3N4), including a boron compound, the boron compound being selected from the group consisting of CaB6 and oxides, carbides, nitrides, fluorides containing boron, a percentage by weight of boron being in a range of 0.05% to 1.5%, and a Si3N4/SiC weight ratio being in a range of 0.05 to 0.45, a porosity of the sintered block being 10% or more.
A refractory block sintered between 1100° C. and 1700° C. based on silicon carbide (SiC) with a silicon nitride binder (Si3N4), at least one boron compound, and optionally at least one calcium compound, the boron compound being selected from the group consisting of CaB6 and oxides, carbides, nitrides, fluorides containing boron, a total amount of calcium and boron being in a range of 0.05% to 1.5%, a Si3N4/SiC weight ratio being in a range of 0.1 to 0.2, a porosity of the sintered material being 10% or more.
A method of fabricating a refractory block based on silicone carbide (SiC), with a silicon nitride binder (Si3N4), intended in particular for fabricating an aluminum electrolysis cell, said method comprising the following steps in succession:
- a) preparing a charge comprising a particulate mixture comprising a silicon carbide granulate, silicon and at least one boron compound, and optionally at least one calcium compound, the boron compound being selected from the group consisting of CaB6 and oxides, carbides, nitrides, fluorides containing boron, a binder optionally being added to said particulate mixture;
- b) forming said charge in a mold;
- c) compacting said charge in the mold to form a preform;
- d) unmolding said preform;
- e) drying said preform, preferably in air or a moisture-controlled atmosphere;
- and
- f) firing said preform in a reducing atmosphere of nitrogen at a temperature in the range 1100° C. to 1700° C.;
- wherein said silicon is able to react during step f) so as to generate Si3N4, said boron and/or calcium compound being added in a quantity which is determined such that the refractory block obtained at the end of step f) includes a total amount of calcium and boron in a range 0.05% to 1.5%.
Dependencies are inferred from the claim text.