The surface topographies of the PEEK MWCNT samples treated
To study the effect of NaBH4 on the surface morphology of swelled PEEK/MWCNT composites and demonstrate the PF-543 of NaBH4 on the surface, the swelled samples were put into 0.1 M NaOH and x M NaBH4–0.1 M NaOH (x = 0.1, 0.3, 0.5) solutions at 40 °C for 15 min respectively. Fig. 2(c)–(f) shows the surface morphology of the samples before and after treated by NaBH4–NaOH solutions. Fig. 2(c) is the magnification of Fig. 2(b). Comparing Fig. 2(d)–(f) with Fig. 2(c), after being treated by x M NaBH4–0.1 M NaOH, the surface morphology of the samples wasn't changed and the interconnected micro-pores were still well remained. Surprisingly, no significant NaBH4 or NaOH crystalline particles were observed. To confirm the absorption of NaBH4, EDS (full-screen scanning model) was used to analyze the surface composition of the samples before and after treating by NaBH4–NaOH solutions. Because it is hard to accurately divide the boron peak and carbon peak in EDS spectrum, we used Na element to illustrate the absorption of NaBH4. For the sample without treating by NaBH4–NaOH, Na element wasn't detected on the surface. However, after the swelled samples were treated by 0.1 M NaOH, 0.1 M NaBH4–0.1 M NaOH, 0.3 M NaBH4–0.1 M NaOH and 0.5 M NaBH4–0.1 M NaOH, the amount of Na element on the surface was 0.62 at.%, 1.01 at.%, 1.80 at.%, and 3.09 at.% respectively. Because the concentration of NaOH was the same for all solutions, the increased amount of Na came from NaBH4 absorbed on the surface. To directly demonstrate B element on the surface, the samples treated by 0.5 M NaBH4–0.1 M NaOH was analyzed by XPS. As shown in Fig. 3, the amount of B element was 7.6 at.% (Fig. 3(a)). And to further study the phase composition on the surface of PEEK/MWCNT with 0.5 M NaBH4–0.1 M NaOH treatment, the sample was analyzed by XRD under grazing-incidence mode. As shown by curve (1) in Fig. 3(b), the four main peaks at 19, 21, 23, and 29° correspond to PEEK. No crystallization peaks of NaBH4 and NaOH were appeared, it might be because the adsorption film was too thin. So we imitated the process by spreading 0.5 M NaBH4–0.1 M NaOH on a sheet of glass, and gathered the powder after blow-drying. The powder was analyzed by XRD under normal wide-angle mode. As shown by curve (2) in Fig. 3(b), the peaks at 25, 29, and 41° correspond to the diffraction of NaBH4 (JCPDS, 74-1891). Besides, the peaks at 14 and 17° correspond to Na2B2O4 (JCPDS, 22-1344). And other small peaks might be correspond to NaOH·xH2O. So we deduced that NaBH4 was absorbed on the surface of NaBH4–NaOH treated PEEK/MWCNT composites.