Search

Abstract: To improve the interfacial properties between carbon fibers and epoxy matrix, the fibers were treated by an ammoniac medium, which consisted of supercritical water, ethanol and triethylene tetramine. The images of atomic force microscopy and scanning electron microscope indicate that coating layers are formed on the surfaces of treated fibers. The results of X-ray photoelectron spectroscopy demonstrate that N content on the surfaces of carbon fibers increases and the main ammoniac groups of the coating layers are amino and imino groups. The mechanical measurements indicate that both interlaminar and interface shear strength of carbon fibers are significantly increased after amination. [Copyright &y& Elsevier]

Abstract: In order to improve the interfacial properties between carbon fibers and epoxy matrix, supercritical water and hydrogen peroxide were used as oxidation medium for the oxidation treatment for carbon fibers. Analysis results of X-ray photoelectron spectroscopy suggest that the oxygen content on the carbon fibers’ surfaces increases by these oxidation treatments. Scanning electron microscope and atomic force microscopy images indicate that the surface appearance of oxidized carbon fibers obviously changed. The maximal interlaminar shear strength and interface shear strength of carbon fiber/epoxy resin composite in which the fibers were treated by the supercritical water and hydrogen peroxide systems reaches 70.46MPa and 106.66MPa, increases by 13.4% and 29.6% respectively compared with untreated carbon fibers. [Copyright &y& Elsevier]

Abstract: The polyacrylonitrile-based (PAN-based) carbon fibers with progressive amounts of the oxidation treatment have been investigated using a number of surface analytical methods. The chemical content and structure of oxidated fibers have been interrogated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM), then compared to the untreated ones. The value of oxygen content increased from 4.71% to 18.84%, meanwhile, the grooves on the surfaces of the carbon fibers were deepened gradually after treatments. The results of dynamic contact angle (DCA) measurements suggest that the increase in carbon fiber surface tension is mainly because of the polar component of surface tension. After treated with increasing amounts of oxidants, the monofilament tensile strength decreased less than 3.1%. [Copyright &y& Elsevier]

• Systematic analysis of PLA ablated by femtosecond laser was first explored. • The surface microstructure displayed a dependence on the fs laser parameters. • The photo-thermal oxidation was proved as the dominant reaction on the surface. • The degradation in PLA matrix was also observed during the surface ablation. The effects of femtosecond laser ablation on the surface morphology, surface chemical composition, and matrix properties of poly-lactic acid (PLA) were explored in this paper, since the analysis of the different energy density range is crucial in evaluating to what extent material properties change during the micromachining. Scanning electron microscopy (SEM) analysis found that different surface microstructures, i.e., the convex microstructure and the through hole, were generated by single and multiple pulses femtosecond laser ablations, respectively. The photo-thermal features appeared on the PLA surface displayed a dependence on the femtosecond laser pulse number or fluence. The surface affected by femtosecond laser ablation was also analyzed using Fourier transforms infrared (FTIR) as well as X-ray photoelectron spectroscopy (XPS), which indicated that an oxidation reaction had occurred during the micromachining. The ablation of PLA surface resulted in a decreased molecular weight and an increase of polydispersity, which was consistent with a drop in transition temperature (T m). Therefore, the substrate also degraded although the micromachining process was only performed on the surface. The variation in PLA surface microstructures, chemistry, and matrix performance resulted from different laser parameters were related to the laser-matter interaction effects. [ABSTRACT FROM AUTHOR]