XPS Analysis of Carbon Fiber Surfaces-Anodized and Interfacial Effects in Fiber-Epoxy Composites

Density Functional Theory Study of Adhesion Mechanism between Epoxy Resins Cured with 4,4'-Diaminodiphenyl Sulfone and 4,4'-Diaminodiphenylmethane and Carboxyl Functionalized Carbon Fiber

The molecular mechanism of adhesion of two epoxy resins based on diglycidylether of bisphenol A (DGEBA) cured with 4,4'-diaminodiphenyl sulfone (DDS) and 4,4'-diaminodiphenylmethane (DDM) to the carbon fiber (CF) surface is investigated by employing density functional theory (DFT) calculations. The CF surface was modeled by the armchair-edge structure of graphite functionalized with carboxyl (COOH) groups. Two adhesion interfaces were constructed using the CF surface: one with the DGEBA-DDS molecule (CF/DGEBA-DDS interface) and the other with the DGEBA-DDM molecule (CF/DGEBA-DDM interface). The interfacial properties were analyzed by calculating the maximum adhesion stress (Smax) at the interface. The adhesion stress-displacement curve revealed that Smax is 1160.37 MPa, higher for the CF/DGEBA-DDS interface compared to the CF/DGEBA-DDM interface, which is 1060.48 MPa. The energy decomposition analysis showed a similar DFT contribution to adhesion stress for both interfaces, but the dispersion contribution is more significant at the CF/DGEBA-DDS interface. The crystal orbital Hamilton population (COHP) analysis revealed distinct interfacial interactions despite similar DFT contributions. Hydrogen bonding (H-bonding) between the functional groups at both interfaces including feeble OH-π interactions between the benzene rings of epoxy resins and COOH groups on the CF surface were observed. The orbital interaction energies calculated from integrated COHP, i.e., IpCOHP, revealed that the CF/DGEBA-DDS interface has six H-bonding interactions with large absolute IpCOHP values (>1 eV), whereas the CF/DGEBA-DDM interface has five. The interaction between the amine group of the DGEBA-DDM molecule and the CF surface has a large IpCOHP value among all interactions. The sulfone group being at the center of the DDS molecule and its strong surface interaction positioned the DGEBA-DDS molecule closer to the CF surface than the DGEBA-DDM molecule, enhancing dispersion interaction at the CF/DGEBA-DDS interface. Hence, the CF surface exhibits a stronger affinity toward the DGEBA-DDS molecule than the DGEBA-DDM molecule through dispersion interaction.

Synthesis of SiO2 Nanoparticle Epoxy Resin Composite and Silicone-Containing Epoxy Resin for Coatings

Due to its unique properties, including strong adhesion force, high heat resistivity, high insulation properties, and strong mechanical properties, epoxy resin is the most commonly used material for a variety of applications, including adhesives, electronic devices for coatings, and somewhere as a matrix for reinforcement of composites as a fiber network. To boost their properties, different other materials are also inserted in their structure and made its composites; silicon is one of them. Corrosion is serious for marine equipment and causes economic loss. To overcome such issues, different types of coating materials are developed. In this review, current methods for coatings of different materials using a silicon dioxide epoxy nanocomposite are discussed in diversity with the currently followed synthetic routes for the preparation of nanosilica epoxy composites and enhanced properties.

Corrosion Behavior of AA2055 Aluminum-Lithium Alloys Anodized in the Presence of Sulfuric Acid Solution

The aim of this work was to evaluate the corrosion behavior of the AA2055 Aluminum-lithium alloy anodized in a sulfuric acid (H2SO4) bath, varying the current density of 0.19 and 1 A·cm−2 and why the sealing solution was water (H2O) and sodium dichromate (Na2Cr2O7). Anodized samples were exposed to a 10 vol.% H2SO4 solution and the electrochemical technique used was electrochemical impedance spectroscopy. Scanning electron microscopy and X-ray photoelectron spectroscopy were employed to characterization of the anodizing layer, determinate morphology and thickness of coatings. The Na2Cr2O7 sealing solution tends to increase the charge transfer resistance and produces a more homogeneous and compact passive oxide layer, and imparts a corrosion inhibition protection to the AA2055. SEM observations indicated that the morphology and thickness of the anodic films formed on AA2055 aluminum-lithium alloy anodized have the best results for both current densities.

Controllable growth of uniform carbon nanotubes/carbon nanofibers on the surface of carbon fibers

Controllable growth of CNTs/CNFs on carbon fiber surface without degradation of tensile strength of carbon fibers.

Facile and efficient route to polyimide-TiO2 nanocomposite coating onto carbon fiber

Polyamic acid-TiO(2) hybrid colloid emulsion with an average particle size of 200 nm was formed by dispersing nano-TiO(2) into polyamic acid colloidal emulsion. The polyimide-TiO(2) nanocomposite was coated onto carbon fiber by electrophoretic deposition. The primary properties of polyamic acid-TiO(2) hybrid colloid emulsion and polyimide-TiO(2) nanocomposite coating onto carbon fiber were characterized using laser scattering, ZetaPlus particle sizing, transmission electron microscopy, field-emission scanning electron microscope, Fourier transforms infrared spectroscopy, and X-ray Diffraction analysis. The results indicated that the small amount of nano-TiO(2) would be effectively dispersed in polyamic acid colloidal particles. The polyimide-TiO(2) hybrid nanocomposite coating carbon fiber sheet displayed an excellent photodegradation performance of methyl orange, which could be degraded more than 70 wt % after 10 cycles.

Adsorption of toluene on carbon nanofibers prepared by electrospinning

This paper reports the novel results of activated carbon nanofibers (ACNF) used to improve the toluene adsorption capacity. The ACNF was prepared by stabilization, carbonization and activation after electrospinning the polymer solution of polyacrylonitrile (PAN) in N, N-dimethylformamide. The average diameter of the ACNF was approximately 300 nm, ranging from 200 to 500 nm. The toluene adsorption capacity of ACNF10 activated at 1000 degrees C increased to 65 g-toluene/100 g-ACNF. This was attributed to the high specific surface area (1403 m(2)/g), large micropore volume (0.505 cm(3)/g), and narrow average pore diameter (6.0 A). The oxygen to carbon ratio (O/C ratio) in ACNF10 was 1.8%. This O/C ratio appears to induce a higher toluene adsorption capacity, which originates from a non-polar interaction between the ACNF surface and toluene. In conclusion, the electrospun ACNF prepared in this study promotes the adsorption of toluene through the high specific surface area, large pore volume, narrow pore diameter and low O/C ratio.

X-ray diffraction and X-ray photoelectron spectroscopy studies of Ni-P deposited onto carbon fiber surfaces: impact properties of a carbon-fiber-reinforced matrix

In this work, the Ni-P coating on carbon fiber surfaces was carried out in order to improve the impact resistance of carbon fibers-reinforced epoxy matrix composites. The fiber surfaces and the fracture behaviors of composites were measured in terms of X-ray diffraction spectrometry (XRD), X-ray photoelectron spectrometry (XPS), scanning electron microscopy (SEM), and falling weight impact testing. From the XRD and XPS measurements, it was observed that Ni-P coating of carbon fibers led to an increase in two phases, i.e., microcrystalline and amorphous, mainly due to the increase of NiP(2), Ni(3)P, and Ni metal. Energy adsorbed by composites through the various fracture mechanisms was seen to be the characteristic distinguishing between nontreated and treated fiber-reinforced composite systems. The Ni-P alloy technique to improve the impact resistance of the composites was shown to be the modification of fiber-epoxy resin interfaces.

Interlaminar and Ductile Characteristics of Carbon Fibers-Reinforced Plastics Produced by Nanoscaled Electroless Nickel Plating on Carbon Fiber Surfaces

In this work, a new method based on nanoscaled Ni-P alloy coating on carbon fiber surfaces is proposed for the improvement of interfacial properties between fibers and epoxy matrix in a composite system. Fiber surfaces and the mechanical interfacial properties of composites were characterized by atomic absorption spectrophotometer (AAS), scanning electron microscopy (SEM), X-ray photoelectron spectrometry (XPS), interlaminar shear strength (ILSS), and impact strength. Experimental results showed that the O(1s)/C(1s) ratio or Ni and P amounts had been increased as the electroless nickel plating proceeded; the ILSS had also been slightly improved. The impact properties were significantly improved in the presence of Ni-P alloy on carbon fiber surfaces, increasing the ductility of the composites. This was probably due to the effect of substituted Ni-P alloy, leading to an increase of the resistance to the deformation and the crack initiation of the epoxy system.

Effect of Fiber-Polymer Interactions on Fracture Toughness Behavior of Carbon Fiber-Reinforced Epoxy Matrix Composites

The effect of anodic oxidation on high-strength polyacrylonitrile-based carbon fibers has been studied in terms of fiber surface energetics and fracture toughness of the composites. According to contact angle measurements based on the wicking rate of a test liquid, anodic oxidation leads to an increase in surface free energy, mainly due to the increase of its specific (or polar) component. For the carbon-fiber-reinforced epoxy resin matrix system, a direct linear relationship is shown between the specific component and the critical stress intensity factor measured by the single edge notched beam fracture toughness test. From a surface-energetic point of view, the anodic treatment may be suitable for carbon fibers incorporated in a polar organic matrix, resulting in an increased specific component of the surface free energy. Good wetting plays an important role in improving the degree of adhesion at interfaces between fibers and matrices of the resulting composites. Copyright 2000 Academic Press.