Alcan International Limited

Prasad S Apte

Aniket Pant

Raymond Y Roy

Robert M Kimber

Harry Sang

Lorne D Kenny

David N Mitchell

Dan Fern

Mark C Patterson

Bryn Chamberlain

A method of heating a workpiece assembly and a load assembly suitable for heating by the method. The method involves heating the workpiece assembly in a microwave cavity surrounded by one or more rings made of electrically conductive material. The rings fix the electrical field in such a way that uniform heating of the workpiece assembly can be achieved. Large workpieces or assemblies can be heated and, if sinterable, sintered in this way without the problems normally caused by lack of uniform fields when microwaves are used to heat large loads.

Microwave heating of workpieces

A process for coloring a metal surface and colored metal products thus produced. The process involves forming a layer of a metal oxide on a surface of the metal to be colored and then bringing about permanent plastic deformation of the surface. If the oxide layer is of a suitable thickness (e.g. 500.ANG.-1 .mu.m) and the deformation is sufficiently high (preferably producing a reduction in thickness of the metal article by 30% or more), the resulting metal article exhibits an attractive color (usually a dichroic pastel color). The article can then be fabricated into finished articles, e.g. beverage cans, in the usual way.

Process for coloring metal surfaces

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

A process and apparatus for heating bodies to high temperatures at high pressures. The process involves locating the body in a chamber capable of acting as a resonant cavity for microwave radiation of a predetermined frequency. The body is then irradiated in the cavity with microwave energy of the predetermined frequency for a time sufficient to raise the temperature of the body to a suitable high temperature. Then, either subsequently or simultaneously, a fluid at high pressure is introduced into the cavity to pressurize the body. The apparatus provides the equipment necessary for the operation of the process. The process and apparatus can be used for sintering and/or hot isostatic pressing of bodies made of ceramic powders and for similar purposes.

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Kingston, Canada

Prasad S Apte