A Martinez-Alonso | PubMed Health

PubMed2000

Adhesion artefacts in atomic force microscopy imaging

Artefacts that affect contrast and arise from adhesion forces in atomic force microscopy images of aramid fibres (both fresh and plasma-treated) are investigated. It is demonstrated that these stem not only from variations in the chemical composition of the surface but also from certain topographical features (which may appear hidden or enhanced in the images), resulting in changes in the lateral forces that are detected by the cantilever and are comparable to the vertical forces. It is also shown that both types of contribution to the forces can be uncoupled to yield images free from these artefacts, thus allowing more accurate quantitative measurements. These artefactual effects are also generally applicable to many other materials.

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PubMed1997

Zeta Potential as a Tool to Characterize Plasma Oxidation of Carbon Fibers

Two different types of carbon fibers (ultrahigh modulus and high strength carbon fibers) were surface-treated in an oxygen plasma under equivalent conditions. Changes in the fiber surface chemistry were followed by electrokinetic measurements (zeta potential). The oxygen plasma treatment resulted in a displacement of the isoelectric point of carbon fibers toward lower pHs, evidence of an increase in the surface acidity. The possible simultaneous formation of basic functional groups was also inferred and supported by results obtained by inverse gas chromatography and wettability measurements. Differences were more evident with ultrahigh modulus carbon fibers than with high strength carbon fibers. It is concluded that the measurement of the electrokinetic properties constitutes a useful technique to follow the evolution of the surface chemical characteristics of different types of carbon fibers. Copyright 1997Academic Press

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