P.E. Vickers et al. Carbon 38(2000)675-689 687 0.120.140.16 0.18 Heteroatom Content Fig. 7. Dispersive energy(y)vs heteroatom content(XPS). A, O/C, O,(N+O/C) ontact angle measured for the untreated fibres(eds >90) little difference as a result of oxidation, actually consistent correlates well with the IGC and XPS data, which show with the IGC data, where the y s is reduced after oxidation very low oxygen content and very low interaction with This reduction is not so likely to be observed with DCAA, polar molecules, respectively. It is interesting to note here because the contact angle is a measure of a combination of that SIMS(Fig. 2) showed only a very small increase in all energy sites on the surface, in contrast to the infinite oxygen content at the surface. This is surprising consider- dilution method employed in IGC, which as stated above, ing that the surface sensitivity of the techniques is IGC- probes the high-energy sites. It follows that the untreated DCAA>SIMS>XPS Glycerol, a moderately polar mole and the treated fibres are chemically and/or energetically cule, also shows a lower advancing contact angle after heterogeneous in nature. Although dCAa failed to detect oxidation, and slight increase in receding contact angle, significant changes in the dispersive properties of the actually consistent with a less rough or a chemically less carbon fibres upon treatment, it proved to be a very heterogeneous surface. The latter is more likely here, convenient way to monitor the changes in the acid-base AFM results have previously shown the roughness characteristics induced by the electrochemical treatment as increase during oxidation [5]. The contact angle made with judged by the y, values reported in Table 9. More I-bromonaphthalene, a non-polar molecule, exhibits very mportantly, the raw dCaa data in Table 8 indicate lower 12 0000.040 0.12 0.16 50100150 250 Heteroatom Content Treatment (%) Fig. 9. Graph of a measure of y, vs. O-C and(N+O)-C Fig. 8. Graph of a measure of y. vS, oxidation treatment. measured by XPsP.E. Vickers et al. / Carbon 38 (2000) 675 –689 687 d Fig. 7. Dispersive energy (g ) vs. heteroatom content (XPS). m, O/C; h, (N1O/C). s contact angle measured for the untreated fibres (u .908) little difference as a result of oxidation, actually consistent adv d correlates well with the IGC and XPS data, which show with the IGC data, where the g is reduced after oxidation. s very low oxygen content and very low interaction with This reduction is not so likely to be observed with DCAA, polar molecules, respectively. It is interesting to note here because the contact angle is a measure of a combination of that SIMS (Fig. 2) showed only a very small increase in all energy sites on the surface, in contrast to the infinite oxygen content at the surface. This is surprising consider- dilution method employed in IGC, which as stated above, ing that the surface sensitivity of the techniques is IGC¯ probes the high-energy sites. It follows that the untreated DCAA.SIMS.XPS. Glycerol, a moderately polar mole- and the treated fibres are chemically and/or energetically cule, also shows a lower advancing contact angle after heterogeneous in nature. Although DCAA failed to detect oxidation, and slight increase in receding contact angle, significant changes in the dispersive properties of the actually consistent with a less rough or a chemically less carbon fibres upon treatment, it proved to be a very heterogeneous surface. The latter is more likely here, as convenient way to monitor the changes in the acid–base AFM results have previously shown the roughness to characteristics induced by the electrochemical treatment as p increase during oxidation [5]. The contact angle made with judged by the g values reported in Table 9. More s 1-bromonaphthalene, a non-polar molecule, exhibits very importantly, the raw DCAA data in Table 8 indicate lower AB Fig. 9. Graph of a measure of g s vs. O–C and (N1O)–C AB Fig. 8. Graph of a measure of g vs. oxidation treatment. measured by XPS. s