High porosity metal biporous foam

Abstract

An environmentally friendly process for producing metal biporous foam by using filamentary metal powders such as nickel or copper. The filamentary metal powders are initially wet when combined with a suitable foam former such as methylcellulose. Because the filamentary metal powder is wet, it does not extract water from the foam structure thereby ensuring a highly porous metal foam having both high macroporosity and microporosity.

Description

TECHNICAL FIELD [0001] The present invention relates to porous foams in general and to porous metal foams in particular. BACKGROUND OF THE INVENTION [0002] Porous metal foams are used in many industrial and consumer applications. Examples include filters, strong and lightweight supports, internal combustion engine exhaust collectors, pollution controls, fuel cells, catalysts, cushioning and absorbing material, electrodes for primary and secondary batteries, etc. Demand for finer porosity, greater surface area, varying metal content and other physical and chemical parameters is driving increased research and development of improved porous metal foams and methods for producing them. [0003] For energy applications, such as alkaline cells, nickel-metal hydride batteries, lithium ion cells and fuel cells, porous metal foams act as electrodes. Typically pasted and activated with the appropriate materials, the foams are both electrodes and conduits for the electrolytes. Depending on the ph...

AI Technical Summary

Benefits of technology

[0018] There is provided a method for producing metal biporous foams by utilizing a solution of filamentary metal powders. A thickened cellulose based foam precursor and the wet metal powder mixture solution are mixed together. Foaming of the precursor is caused to occur. Once completed the resultant foam is moderately dried to form a green cake. The green cake is sintered in a reducing atmosphere.

Problems solved by technology

Manufacturing foam by means of chemical reactions generating a gas results in a variation in the size of the bubbles or porosity or texture of the foam through its height due to the weight of material above the forming bubble.

However, these latter methods tend to be violent and will damage the delicate structure of the metal powders contemplated by present invention.

Unfortunately this method degrades the initial foam and cannot be used when using metal powders.

The organics present a fire and environmental issue.

Moreover, there is no control over bubble size.

Adding the metal as dry powder draws water from the foam structure causing it to collapse.

It also incorporates into the mixture a pocket of air surrounding each particle or agglomeration of particles which later contributes to the microstructure of the foam to an uncontrolled extent.

There are fire and environmental issues caused by this process.

Volatization of the combined hydroxide functional siloxene and the hydride functional siloxane leads to environmental concerns.

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