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First-order Raman spectra of virgin and ion irradiated highly oriented pyrolytic graphite were performed along the basal and edge planes. Ion irradiation was performed in the low fluence regime ( 10 12 -10 13 ions cm -2 ) using a 400 keV Ar + beam in order to a introduce controlled amount of defects in the structure. Virgin edge Raman spectra reveal...
High strength, PAN-based carbon fibers were treated with oxygen plasmas and isobutylene plasmas. The effects of exposure time, plasma power and gas pressure on the quantity of acidic functional groups introduced onto the fiber surfaces were examined. NaOH uptake measurements provided a quantitative determination of the surface acidic functions. Plasma treatments were able to generate a three-to-five-fold...
The formation of the surface functional group during oxygen reduction on a platinum-dispersed carbon (Pt/C) electrode has been investigated in an 85% H 3 PO 4 solution at 145°C with concurrent blowings of a mixture of oxygen and nitrogen by using Fourier transform infrared (FTIR) spectroscopy supplemented by AC-impedance spectroscopy. AC-impedance spectra indicated that the reactivity...
The factors that influence oxidation resistance of B 4 C/C composites with self-healing properties during oxidation are discussed in this paper. Isothermal oxidation behavior of B 4 C/C composites with different B 4 C content is examined from 600 to 900°C. Analysis of oxidation kinetics of B 4 C/C composites at the temperature range of 600–900°C showed that nominal...
The oxidation behavior of B 4 C–SiC/C composites of various compositions at temperatures up to 1500°C was analyzed by the thermal gravimetric/differential thermal analysis (TG/DTA) technique and the surface morphology of the composites after isothermal oxidation at 800, 1000 and 1200°C was examined by scanning electron microscopy. The results indicated that the composites exhibited variable...
Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle analyses were performed on unsized and sized carbon fibers to better understand the mechanism of adhesion in carbon fiber/polymer matrix composites. AFM images and surface roughness analyses showed that the sizing changes the surface topography on a microscopic scale. The total surface energy decreased from 70...
The surface chemistry of two active carbons was modified using a microwave device as a heat source. When microwave treatments are conducted in a nitrogen flow, most oxygen-containing groups are removed from the surface of the carbons. This in turn gives rise to a significant increase in the pH of the carbons. Microwave treatment is less time-consuming than conventional heating. Only a few minutes...
The present study concerns anodic oxidation of activated carbon fibers (ACFs) in order to introduce the surface functional groups onto ACF surfaces. The surface oxides of ACFs were measured using titration and FT-IR spectrometry. As a result, it was observed that the amount of adsorption and the adsorption rate of Cr(VI) increase with increases in the surface oxide groups of ACFs, even though both...
The mechanical and surface characteristics of pitch and PAN-based carbon fibres were studied by tensile testing, XPS, SEM analysis and wetting measurements. The pitch-based fibres had two different geometries, with circular and ellipsoidal (ribbon-shaped) cross sections. Plasma oxidation was used to treat the surface of the fibres. The interfacial characteristics of untreated and treated fibres were...
The environmental stabilities of graphite intercalation compounds (GICs) containing bifluoride, nitrate, sulfate, C 8 F 17 SO 3- , N(CF 3 SO 2 ) 2- , or N(CF 2 CF 3 SO 2 ) 2- are determined at 20 o C in air, at 50 o C and 100% relative humidity, and at 20 o C in liquid water...
Two types of carbon fibres, ultra-high modulus (pitch-based) and high strength (PAN-based), were submitted to an oxygen plasma treatment. Single filament tests were performed to evaluate the effects of the treatment on the mechanical properties of the fibres. Weibull analysis of the tensile data revealed no substantial changes in the tensile strength after fibre oxidation. Fragmentation tests performed...
Pitch-based activated carbon fibers (ACFs) were modified with nitric acid and sodium hydroxide. Their physicochemical properties were investigated in terms of N 2 adsorption, mass titration, FTIR and metal adsorption. The specific surface area of the ACFs decreased after oxidation with 1 M nitric acid, but the total acidity increased three times compared to the untreated ACFs, resulting in...
The tensile strength of cement paste was increased by 56% and the modulus and ductility were increased by 39% by using silane-treated carbon fibers and silane-treated silica fume, relative to the values for cement paste with as-received carbon fibers and as-received silica fume. Silane treatment of fibers and silica fume contributed about equally to the strengthening. Silane treatment of fibers and...
Coconut shell-based activated carbon was oxidized in aq. H 2 SO 4 , HNO 3 and H 2 O 2 to induce surface oxygen functional groups on its surface and to increase the mechanical strength of the resultant activated carbon artifact with PVB as a binder. Although all oxidation was confirmed to significantly increase the strength, aq. H 2 O 2 was found...
High-modulus carbon fibres from different precursors were submitted to an oxygen plasma-treatment under similar conditions. Single-fibre epoxy composites were prepared from them, and fragmentation tests were performed in order to characterise fibre-matrix interfacial adhesion. Raman spectroscopy has been used in the present work to map the strain along the fibre during tensile loading of the matrix...
The effect of an oxygen plasma treatment upon the structural and morphological properties of high-modulus carbon fibres has been studied by means of several characterisation techniques. Scanning electron microscopy showed that there were only minor changes of the morphology of the fibres following treatment. X-ray diffraction traces revealed that there were differences in structural parameters between...
Graphite anodes for use in lithium ion batteries were prepared from graphite particles pretreated in a gelatin solution. The content of gelatin in the final anode material was determined from the difference in mass of graphite particles before and after the treatment with gelatin and by thermogravimetric analysis. Forces between a gelatin-coated glass particle and graphite surface were measured in...
Scanning tunneling microscopy (STM) has been employed to monitor the changes in surface structure induced by oxygen plasma treatments of submicron vapor grown carbon fibers (VGCFs). It is shown that the fibers preserve their general smoothness upon plasma oxidation and that the structural changes brought about by this treatment essentially take place only at the atomic scale, where the relatively...
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