Control of interfaces in Al-C fibre composites

The interface of Al-C fibre composite was modified by coating a silver layer on the surface of carbon fibres prior to making composites, in an attempt to improve the wettability between molten aluminium and carbon fibres during infiltration. An electroless plating technique was adopted and perfected to provide a homogeneous silver coating on the carbon fibre surface. Al-C fibre composites were prepared using a liquid infiltration technique in a vacuum. It was found that silver coating promoted the wetting between aluminium and carbon fibres, particularly with polyacrylonitrile-base carbon fibres. However, due to rapid dissolution of silver in molten aluminium, it was believed that the improved infiltration was not due to the wetting behaviour between molten aluminium and silver. The cleaning of the fibre surface and the preservation of the cleaned carbon surface with silver coating was considered to be the prime reason for the improved wettability. Interfacial reactions between aluminium and carbon fibres were observed. Amorphous carbon was found to react more with aluminium than graphitic carbon. This is believed to be because of the inertness of the graphitic basal planes.