US4333813A — Cathodes for alumina reduction cells

Claim 1

Independent Claim 144 words

A cathode for an alumina reduction cell, said cathode comprising a carbonaceous bed and a composite tile, said composite tile being characterized by a layer of an RHM material bonded to a base layer of a graphitic material, said RHM material comprising a hot pressed mixture of titanium diboride and aluminum nitride powders, said composite tile being further characterized by the bond between said layer of an RHM material and said base layer of a graphitic material, said bond having been produced simultaneously as said layer of an RHM material is formed by hot pressing said mixture of said powders directly against said base layer of a graphitic material, said base layer of a graphitic material being bonded to said carbonaceous bed by means of a carbonaceous cement, said layer of an RHM material thereby providing a molten aluminum contacting surface of said cathode.

Claim 2

Dependent Claim 144 words

A cathode for an alumina reduction cell, said cathode comprising a carbonaceous bed and a composite tile, said composite tile being characterized by a layer of an RHM material bonded to a base layer of a graphitic material, said RHM material comprising a hot pressed mixture of titanium diboride and aluminum nitride powders, said composite tile being further characterized by the bond between said layer of an RHM material and said base layer of a graphitic material, said bond having been produced simultaneously as said layer of an RHM material is formed by hot pressing said mixture of said powders directly against said base layer of a graphitic material, said base layer of a graphitic material being bonded to said carbonaceous bed by means of a carbonaceous cement, said layer of an RHM material thereby providing a molten aluminum contacting surface of said cathode.

Claim 3

Dependent Claim 66 words

The cathode of claim 1 wherein said carbonaceous bed includes a recess and said composite tile is set within said recess and bonded to said carbonaceous bed by means of a graphitic cement with the interface between said layer of an RHM material and said base layer of a graphitic material being disposed within said recess and below the adjacent exterior surface of said carbonaceous bed.

Claim 4

Dependent Claim 20 words

The cathode of claim 1 wherein said carbonaceous bed is constructed from graphite blocks joined together with a carbonaceous cement.

Claim 5

Dependent Claim 18 words

The cathode of claim 1 wherein said layer of an RHM material is reinforced with fibers or particles.

Claim 6

Dependent Claim 26 words

The cathode of claim 4 wherein said fibers or particles are formed of a material selected from the group consisting of carbon, graphite and silicon carbide.

Claim 7

Dependent Claim 150 words

A construction block for constructing a cathode for an alumina reduction cell, said construction block comprising a carbonaceous block and a composite tile, said composite tile being characterized by a layer of an RHM material bonded to a base layer of a graphitic material, said RHM material comprising a hot pressed mixture of titanium diboride and aluminum nitride powders, said composite tile being further characterized by the bond between said layer of an RHM material and said base layer of a graphitic material, said bond having been produced simultaneously as said layer of an RHM material is formed by hot pressing said mixture of said powders directly against said base layer of a graphitic material, said base layer of a graphitic material being bonded to said carbonaceous block by means of a carbonaceous cement, said layer of an RHM material thereby providing a molten aluminum contacting surface of said cathode.

Claim 8

Dependent Claim 150 words

A construction block for constructing a cathode for an alumina reduction cell, said construction block comprising a carbonaceous block and a composite tile, said composite tile being characterized by a layer of an RHM material bonded to a base layer of a graphitic material, said RHM material comprising a hot pressed mixture of titanium diboride and aluminum nitride powders, said composite tile being further characterized by the bond between said layer of an RHM material and said base layer of a graphitic material, said bond having been produced simultaneously as said layer of an RHM material is formed by hot pressing said mixture of said powders directly against said base layer of a graphitic material, said base layer of a graphitic material being bonded to said carbonaceous block by means of a carbonaceous cement, said layer of an RHM material thereby providing a molten aluminum contacting surface of said cathode.

Claim 9

Dependent Claim 67 words

The construction block of claim 6 wherein said carbonaceous block includes a recess and said composite tile is set within said recess and bonded to said carbonaceous block by means of a graphitic cement with the interface between said layer of an RHM material and said base layer of a graphitic material being disposed within said recess and below the adjacent exterior surface of said carbonaceous block.

Claim 10

Dependent Claim 14 words

The construction block of claim 6 wherein said carbonaceous block is made of graphite.

Claim 11

Dependent Claim 19 words

The construction block of claim 6 wherein said layer of an RHM material is reinforced with fibers or particles.

Claim 12

Dependent Claim 27 words

The construction block of claim 9 wherein said fibers or particles are formed of a material selected from the group consisting of carbon, graphite and silicon carbide.

Claim 13

Dependent Claim 144 words

An alumina reduction cell having a drained cathode which comprises a carbonaceous bed and a composite tile, said composite tile being characterized by a layer of an RHM material bonded to a base layer of a graphitic material, said RHM material comprising a hot pressed mixture of titanium diboride and aluminum nitride powders, said composite tile being further characterized by the bond between said layer of an RHM material and said base layer of a graphitic material, said bond having been produced simultaneously as said layer of an RHM material is formed by hot pressing said mixture of said powders directly against said base layer of a graphitic material, said base layer of a graphitic material being bonded to said carbonaceous bed by means of a carbonaceous cement, said layer of an RHM material thereby providing a molten aluminum contacting surface of said cathode.

Claim 14

Dependent Claim 144 words

An alumina reduction cell having a drained cathode which comprises a carbonaceous bed and a composite tile, said composite tile being characterized by a layer of an RHM material bonded to a base layer of a graphitic material, said RHM material comprising a hot pressed mixture of titanium diboride and aluminum nitride powders, said composite tile being further characterized by the bond between said layer of an RHM material and said base layer of a graphitic material, said bond having been produced simultaneously as said layer of an RHM material is formed by hot pressing said mixture of said powders directly against said base layer of a graphitic material, said base layer of a graphitic material being bonded to said carbonaceous bed by means of a carbonaceous cement, said layer of an RHM material thereby providing a molten aluminum contacting surface of said cathode.

Claim 15

Dependent Claim 68 words

The alumina reduction cell of claim 11 wherein said carbonaceous bed includes a recess and said composite tile is set within said recess and bonded to said carbonaceous bed by means of a graphitic cement with the interface between said layer of an RHM material and said base layer of a graphitic material being disposed within said recess and below the adjacent exterior surface of said carbonaceous bed.

Claim 16

Dependent Claim 22 words

The alumina reduction cell of claim 12 wherein said carbonaceous bed is constructed from graphite blocks joined together with a graphitic cement.

Claim 17

Dependent Claim 43 words

The alumina reduction cell of claims 11, 12 or 13 wherein said molten aluminum contacting surface provided by said layer of an RHM material is inclined from the horizontal to facilitate the drainage of molten aluminum from said layer of an RHM material.

Claim 18

Dependent Claim 35 words

The alumina reduction cell of claims 11, 12 or 13 wherein said drained cathode is provided with one or more channels to facilitate the drainage of molten aluminum from said layer of an RHM material.

Claim 19

Dependent Claim 41 words

The alumina reduction cell of claims 11, 12 or 13 which further comprises interior sidewalls made of a graphitic material, said interior sidewalls being adapted to contact and contain the electrolytic bath necessary for the operation of said alumina reduction cell.

Claim 20

Dependent Claim 22 words

The alumina reduction cell of claim 16 wherein said interior sidewalls are constructed from graphite blocks joined together with a graphitic cement.

Claim 21

Dependent Claim 23 words

The alumina reduction cell of claims 11, 12 or 13 wherein said layer of an RHM material is reinforced with fibers or particles.

Claim 22

Dependent Claim 28 words

The alumina reduction cell of claim 18 wherein said fibers or particles are formed of a material selected from the group consisting of carbon, graphite and silicon carbide.

Claim 23

Dependent Claim 95 words

A composite tile, said composite tile being characterized by a layer of an RHM material bonded to a base layer of a graphitic material, said RHM material comprising a hot pressed mixture of titanium diboride and aluminum nitride powders, said composite tile being further characterized by the bond between said layer of an RHM material and said base layer of a graphitic material, said bond having been produced simultaneously as said layer of an RHM material is formed by hot pressing said mixture of said powders directly against said base layer of a graphitic material.

Claim 24

Dependent Claim 95 words

A composite tile, said composite tile being characterized by a layer of an RHM material bonded to a base layer of a graphitic material, said RHM material comprising a hot pressed mixture of titanium diboride and aluminum nitride powders, said composite tile being further characterized by the bond between said layer of an RHM material and said base layer of a graphitic material, said bond having been produced simultaneously as said layer of an RHM material is formed by hot pressing said mixture of said powders directly against said base layer of a graphitic material.

Claim 25

Dependent Claim 32 words

The composite tile of claim 20 wherein the volumetric proportion of tianium diboride to aluminum nitride in said mixture of said powders is in the range of about 2:3 to about 3:2.

Claim 26

Dependent Claim 25 words

The composite tile of claim 21 wherein the volumetric proportion of titanium diboride to aluminum nitride in said mixture of said powders is about 1:1.

Claim 27

Dependent Claim 29 words

The composite tile of claims 20, 21 or 22 wherein said mixture of said powders has been hot pressed to at least about 85 percent of its theoretical density.

Claim 28

Dependent Claim 25 words

The composite tile of claim 22 wherein said mixture of said powders has been hot pressed to a density of at least about 3.7 gm/cc.

Claim 29

Dependent Claim 71 words

The composite tile of claims 20, 21 or 22 wherein said graphitic material is a graphite characterized by coefficients of thermal expansion within the range of about 5×10 -6 /°C. to about 8.5×10 -6 /°C. in all directions parallel to the plane of said composite tile and by a specific room temperature resistivity of less than about 1.0×10 -2 ohm-cm in the direction normal to the plane of said composite tile.

Claim 30

Dependent Claim 101 words

The composite tile of claim 22 wherein said RHM material is characterized by coefficients of thermal expansion within the range of about 5×10 -6 to about 7×10 -6 /°C. in all directions parallel to the plane of said composite tile and said graphitic material is a graphite characterized by coefficients of thermal expansion within the range of about 7×10 -6 to about 8.5×10 -6 /°C. in all directions parallel to the plane of said composite tile and by a specific room temperature resistivity of less than about 4×10 -3 ohm-cm in the direction normal to the plane of said composite tile.

Claim 31

Dependent Claim 55 words

The composite tile of claims 20, 21 or 22 wherein said layer of an RHM material is within the range of about 0.250 to about 0.375 (0.508 to 0.953 centimeters) inch thick and said base layer of a graphitic material is within the range of about 0.750 to 1.00 inch (1.928 to 2.540 centimeters) thick.

Claim 32

Dependent Claim 22 words

The composite tile of claims 20, 21 or 22 wherein said layer of an RHM material is reinforced with fibers or particles.

Claim 33

Dependent Claim 27 words

The composite tile of claim 28 wherein said fibers or particles are formed of a material selected from the group consisting of carbon, graphite and silicon carbide.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1985-06-07	1985-12-07	1986-06-08	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1989-06-07	1989-12-07	1990-06-08	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1993-06-07	1993-12-07	1994-06-08	$7700.00	Window Closed / Lapsed

Cathodes for alumina reduction cells

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