Atomic force microscopy of ion-beam modified carbon fibers

Several commercial PAN and pitch based carbon fibers were modified by a low voltage ion source of nitrogen or oxygen in the range of 400-1000 eV. The fiber reinforced epoxy composites made from the treated fibers were found to have higher interfacial strength than those made from the untreated ones. The improvement of adhesive strengths obtained from the transverse tensile stress measurement reached as high as three to four folds of the original fibers. This result could be explained from increased roughness and enhanced surface functionalities. The scanning electron microscope, which traditionally is used for surface characterization, fails to detect the mild surface alteration caused by the bombardment of the low-energy ion beams. Thus, the atomic force microscope (AFM) with near-atomic resolution might provide us the information needed for the understanding of ion-modified morphology. In the present investigation, the AFM instrument, manufactured by TopoMetrix is used in the characterization of the modified fibers. Preliminary AFM results indicate significant morphology and topography changes on the treated surfaces.