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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: 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]

Abstract: Four kinds of polyacrylonitrile-based carbon fibers were cleaned by three methods and were characterized by X-ray photoelectron spectroscopy, monofilament tensile strength test and atomic force microscopy (AFM). Experimental results of these tests reveal that the method using supercritical acetone or subcritical potassium hydroxide aqueous solution act as the processing medium shows a better cleaning effect compared to the traditional method, Soxhlet extraction with acetone. The method using supercritical acetone is more appropriate to wipe off the oxygenated contaminants on carbon fibers’ surfaces and causes a relatively smaller damage to the bulk strength of each carbon fiber. As far as treating method using the subcritical alkali aqueous solution, it can thoroughly remove silicious contaminants on the surfaces of treated fibers. [Copyright &y& Elsevier]

Abstract: Carbon fiber reinforced composite materials can be enhanced by introducing oxygen-containing groups on the surface of the reinforcing fibers to improve the interface bonding strength between carbon fibers and polymer matrix. While the addition of oxygen-containing groups has been shown to effectively increase the interfacial interaction between fibers and matrix, the treatments tend to consume the carbon fiber tensile strength. In this work, the surface of carbon fibers is oxidized by a chemical oxidation method which employs a strong oxidant of K2S2O8 and a catalyst of AgNO3 to effectively creating carboxyl and hydroxy functionalized surface and the reaction is shown that it can preserve the tensile strength and morphology of the carbon fibers. The surface oxidation is investigated by X-ray photoelectron spectroscopy, which shows that the relative surface coverage by oxygen atoms is increased from an initial 4.49% up to a maximum of 14.11% while the results of single fiber tensile strength tests demonstrate that the reaction did not lead to any obvious decrease in the fiber tensile strength. After oxidation, the interfacial shear strength (IFSS) improved from 59.52 to 96.73MPa, with a increase of 62.5%. [Copyright &y& Elsevier]

Highlights: [•] A new chemical grafting method for carbon fibers was proposed. [•] The oxidation system adopts K2S2O8 and AgNO3. [•] The interfacial shear strength (IFSS) of carbon fiber increased by 61%, and the interfacial adhesion increased with dendritic generation number. [•] The tensile strength of carbon fiber does not decrease distinctly. [•] The treatment conditions are mild and convenient. [ABSTRACT FROM AUTHOR]