Alcan International Limited

David N Mitchell

Adam J Gesing

Ernest W Dewing

Douglas N Reesor

Aniket Pant

Douglas J Wheeler

Peter Alexander Wales

Prasad S Apte

Robert M Kimber

Raymond Y Roy

Joseph K Walker

Donald L De Respiris

A process for preparing a heat-treated body from a material (preferably a dielectric ceramic) that does not couple well with microwaves while nevertheless using microwave energy for the heating step. The process involves the use of a microwave susceptor (i.e. a material that couples well with microwaves) as a means for generating heat in the material. To avoid contamination of the final product, a susceptor is chosen which is converted, during the heating step, to a substance which is substantially the same as the material itself, both the susceptor and the material are converted to the same desired final product, or the material is converted to a substance substantially the same as the susceptor. The resulting substantially pure heat-treated (and preferably sintered) bodies can be used for a variety of purposes, e.g. as substrates for micro-electronic devices. The process can also be used for joining bodies of non-susceptor materials without contaminating the resulting joint.

Process for heating materials by microwave energy

In an aluminium reduction cell including a cell lining and embedded therein at least one cathode current collector including a high temperature section comprising an electrically conducting refractory material such as titanium diboride, generally in conjunction with molten aluminium metal, corrosion is a problem. The invention provides a substance to protect the collector section. The substance may be a liquid impermeable layer e.g. particulate material impregnated with a molten fluoride-or chloride-containing salt mixture; for a getter such as particulate aluminium to react chemically with gaseous corrosive species. Combinations of these substances may be used, optionally in conjunction with a solid layer such as an alumina or aluminium metal tube.

Aluminium reduction cell

A lining to support the liquid contents of an aluminium electrolytic reduction cell includes an upper layer which is penetrated by electrolyte during operation of the cell, consisting essentially of unbonded alumina, including a substantially close-packed array of alumina shapes, the gaps between the shapes being substantially filled with particulate alumina in one or more fractions having discrete particle size ranges, including a fraction having an average particle diameter not more than 20% of the average diameter of the shapes, the layer having a bulk density of at least 2.0 g/cc.

Linings for aluminium reduction cells

An aluminium reduction cell includes a potlining 16, which may be of alumina, with cathode current collectors 24, 32 embedded therein. The cell floor has an array of depressions 22 with at least one collector at the bottom of each depression. The depressions are filled with metal-wettable bodies 20, e.g. 5-20 mm diameter balls of titanium diboride, sized to prevent the entry of electrolyte or sludge. The depressions may be elongate in a direction perpendicular to the horizontal magnetic field in the cell.

Aluminium reduction cells

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Kingston, Canada

David N Mitchell