Method for producing metal foams and furnace for producing same

Abstract

A method for producing a metal structure comprising the following steps: providing a metal-coated polymer substrate; heating the metal-coated polymer substrate in a hot zone, in which a temperature of at least 600° C. prevails and in which an atmosphere essentially composed of water vapor or of a mixture of water vapor and neutral gas is maintained, so as to remove the polymer substrate and form a metal structure; and cooling the metal structure in a cooling zone.

Description

[0001] The present invention generally relates to a method for producing metal foams from metal-coated polymer structures and to a furnace for producing metal foams.[0002] The production of metal foams for the manufacturing of batteries is currently an important issue. In particular, nickel foam is largely used in the manufacture of batteries.[0003] Conventionally, nickel foam is produced by firstly depositing nickel on a polymer foam substrate, e.g. polyurethane foam, and then, subjecting the nickel-coated polymer substrate to a thermal treatment. Such a thermal treatment is generally carried out in a continuous belt furnace with three zones. The nickel-coated polymer substrate, laid on the conveyor belt, firstly travels through an oxidizing zone in which it is exposed to a high temperature and to free oxygen, whereby the polymer is burned. The polymer substrate is thus removed, leaving an oxidized nickel foam structure. Next to the oxidizing zone is a reducing and annealing zone, ...

AI Technical Summary

Benefits of technology

[0009] After the polymer has been removed, a metal structure remains. It shall be noted that the water vapor is, under the conditions employed, only oxidizing to carbon and the metal is not oxidized. As the metal is not oxidized during removal of the polymer, no specific reducing treatment is needed. In particular, the metal structure is not exposed to an atmosphere containing high concentrations of hydrogen. This means that the conventional reducing step in pure or highly concentrated hydrogen is not required any more. In fact, in the method according to the present invention the use of hydrogen is not required at all. The manufacturing costs are thus reduced and the risks involved with the use of pure or highly concentrated hydrogen are eliminated.

[0034] In a preferred embodiment, the furnace comprises a sliding surface extending through the hot zone and the cooling zone, on which the metal-coated polymer substrate is made to slide. Guiding means installed outside and / or inside the furnace may e.g. comprise a first roll arranged before the hot zone and a second roll arranged about the exit of the cooling zone. As the rolls rotate, the metal-coated polymer substrate progresses in the furnace by sliding on the sliding surface. The sliding surface may be formed by the upper surface of a sliding plate extending through the hot zone and the cooling zone. Th sliding plate is pref rably perforated to allow for an easy access of the water vapor to the strip, and for efficient evacuation of the reaction products.

Problems solved by technology

The production of metal foams for the manufacturing of batteries is currently an important issue.

Firstly, burning the polymer in free oxygen allows the removal of the polymer substrate, but it unfortunately also causes oxidation of the metallic nickel.

The oxidized nickel structure must then be reduced in a reducing atmosphere after the polymer removal, which complicates the treatment; Furthermore, the oxidized nickel structure is very brittle and fragile.

The conveyor belt has a negative influence on the energy balance of the process since not only the comparatively light nickel structure needs to be heated and cooled but also the comparatively heavy conveyor belt structure.

Another drawback of this process is the use of pure hydrogen, which increases the production costs and which is dangerous to handle.

% resulting in an over oxidation of the metal.

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