STUDIES ON NICKEL COATED CARBON-FIBERS AND THEIR COMPOSITES

Uniform and continuous coating of nickel was given to the carbon fibres by cementation, electroless or electroplating techniques. The coating thickness was ranged between 0.2 and 0.6 μm for all the three methods used. Coating thickness less than 0.2 μm showed discontinuous coating of nickel over the fibre surface. Beyond 0.6 μm thickness, nickel deposited in den-drite form over the continuous coating. For continuously coated fibres, the ultimate tensile properties of electroless coated fibres were near to uncoated carbon fibres suggesting adherent and defect free coating; while fibres coated by electrolytic and cementation process exhibited lower ultimate tensile strength (UTS) properties. The tensile fracture of the cementation coated fibres suggested degradation of the fibres. In composites, prepared by dispersing the coated fibres in pure aluminium matrix, no appreciable fibre-metal interaction was observed. NiAl3 intermetallics were observed around and adjacent to the carbon fibres. Sometimes carbon fibres were found embedded in massive NiAl3 intermetallics suggesting that fibre surface can also act as nucleating centre for these precipitates. © 1990 Chapman and Hall Ltd.