Electrolytic Al production with reactive sintered ceramic components of boride-oxide phases

Claim 1

A component of an electrolytic aluminum production cell which in use is normally in contact with molten aluminum or in electrical contact with another component which is normally in contact with molten aluminum, characterized in that it has a surface and/or inner portion made of a reaction sintered oxide-boride ceramic consisting essentially of a fine-grained, homogeneous, intimate interdispersion of: (a) 10-90 mole percent of boride phase or phases having a maximum grain size substantially not greater than 15 μm and being boride of one or more of the elements of Groups 4b, 5b and 6b, and (b) 10-90 mole percent of oxide phase or phases having a maximum grain size substantially not greater than 15 μm and being predominantly Al 2 O 3 ; which ceramic is prepared by the process comprising: (c) admixing particulate reactants of maximum particle size substantially not greater than 150 μm and being elements, compounds, intermetallic compounds, alloys or combination thereof in stoichiometric proportions to substantially form the boride and oxide phases, and (d) shaping and heating the admixture to form the reaction sintered ceramic, the heating being done in nonreactive atmosphere and at temperature at which the reaction and sintering occurs between the reactants to substantially form the boride and oxide phases.