Treated Carbon Fiber Research Articles

Hydrogen storage by carbon fibers from cotton

A maximum of 8.75 wt% hydrogen adsorption was observed by carbon fibers which were obtained by the pyrolysis of cotton. Cotton was pyrolysed at 750°C for 3 h in argon atmosphere. Carbon fiber was soaked with 0.1M Ni(NO3)2. This was filtered and dried at 100°C. Finally, metal nitrate treated carbon fibers were heated at 850°C for 3 h in argon atmosphere. Carbon fibers thus obtained were found to absorb hydrogen to the extent of 8.75 wt%. Taguchi optimization technique was adopted to find out the best parameters responsible to give highest hydrogen adsorption. Carbon fibers that showed 8.75 wt% hydrogen adsorption were characterized by SEM, TEM, XRD, and Raman analysis.

Stability of carbon fiber surface functionality at elevated temperatures and its influence on interfacial adhesion

The thermal stability of the surface chemistry of a surface treated carbon fiber, from room temperature to 1000°C, was investigated by X-ray photoelectron spectroscopy. Within a range of temperatures from room temperature to 400°C, the only surface functionalities that decomposed were carboxylic acids and dangling nitrogen containing functionalities like amines, amides or nitriles. Significant amounts of water were desorbed as well. This study enabled the testing of the coherence of the fitting of the C(1s), O(1s) and N(1s) peaks. Particularly, when considering the fitting of in the O(1s) peak, carboxylic acids were shown to be included in a single component peak centered at a binding energy of 532.1eV. The reaction of the carbon fiber surface and an acrylate resin at high temperature, because of the decomposition of carboxylic acids, was highlighted by differential scanning calorimetry. The thermal history of the composite material during its manufacture appeared to be a major influence on the nature of the interactions generated at the fiber–matrix interface and the resulting mechanical properties.

The Effect of Silane Surface Treatment of Carbon Fiber on the Tribological Properties of Bismaleimide(BMI) Composite

Silane surface modification method was used for the surface treatment of carbon fiber to improve the interfacial adhesion of the carbon fiber reinforced bismaleimide(BMI) composite. The surface characteristics of untreated and treated carbon fiber were characterized by Fourier transform infrared (FT-IR) spectroscope. The friction and wear properties of the BMI composites filled with differently surface treated carbon fibers(20 vol%), were investigated on a ring-on-block tribometer. Experimental results revealed that silane treatment largely reduced the friction and wear of CF/BMI composites. Scanning electron microscope (SEM) of worn surfaces of BMI composites showed that surface treated CF/BMI composite had the strongest interfacial adhesion.

Effects of Supercritical Carbon Dioxide on Interfacial Properties of Carbon Fiber

In this paper , a new treatment method based on polyacrylonitrile (PAN) based carbon fiber treated by supercritical carbon dioxide (SCCO2) is proposed. This method aiming to obtain a controlled interface is green and pollutionless . The surface state of carbon fibers both untreated and treated on different temperature was studied by using SEM, AFM and XPS. The results show that SCCO2 can erode the surface of carbon fibers. Roughness of modified carbon fiber is higher than that of the untreated. Interfacial properties of the treated carbon fiber /epoxy microcomposites were improved. Interfacial shear strength (ILSS) of CFRP shows that treated carbon fiber /epoxy at a lower temperature can be increased by 17.35%, which means that an effect of optimized interface is obtained.

Properties of thermo-chemically surface treated carbon fibers and of their epoxy and vinyl ester composites

Carbon fibers were surface treated by a continuous gas phase thermo-chemical treatment. The surface and the mechanical properties of the fibers were investigated before and after treatment and compared to the properties obtained with a conventional industrial electro-chemical surface treatment. The increase of the oxygen atomic content was much sharper, the surface chemistry was better controlled, and the tensile strength of the fibers increased slightly with the thermo-chemical surface treatment. The thermo-chemical surface treatment created a topography which amplitudes were under 10nm, thus creating some mechanical interlocking with the matrix. The electro-chemical surface treatment did not generate such a topography. The improvement of interfacial adhesion with a vinyl ester matrix was limited, revealing that oxidation of the carbon fiber surface alone cannot tremendously improve the mechanical properties of carbon fiber–vinyl ester composites.

The Effect of Arylboronic Acid Treatment of Carbon Fiber on the Mechanical and Tribological Properties of PA66 Composites

PA66 composites filled with surface-treated carbon fiber were prepared by twin-screw extruder in order to study the influence of carbon fiber surface arylboronic acid treatment on the mechanical and tribological behavior of the PA66 composites (CF/PA66). The mechanical property, friction and wear tests of the composites with untreated and treated carbon fiber were performed and the worn surface morphology was analyzed. The results show that the worn surface area of the treated carbon fiber was far smoother than that of the untreated carbon fiber and there formed a bonding adhesion on the carbon fiber surface after treatment. The tensile strength of CF/PA66 composites with surface arylboronic acid treatment was improved. The friction coefficient and wear of arylboronic acid treated CF/PA66 composites were apparently lower than that with untreated carbon fiber. In conclusion, the surface treatment favored the improvement of the higher interface strength and so had good effect on improving the tribological properties of the composites.

Control, Effection and Analysis of Voltage during Dielectric Barrier Discharges Plasma Surface Treated Carbon Fibers

The deposition of coatings on the surface of carbon fiber will be helpful to their applications. However, they are unsuitable to be deposited due to their low surface free energies, poor wettability and poor adhesions. The objective of this work is to modify carbon fibers by Dielectric barrier discharges(DBD)in ambient argon . The chemical and physical changes induced by the treatments on carbon fibers surface are examined using contact angle measurements and X-ray photoelectron spectroscopy (XPS). The interfacial adhesion of CF/EP composites are analyzed by a single fiber composite (SFC) for filament fragmentation test. The contact angles of the plasma-treated samples are visibly reduced than the untreated samples. XPS results reveal that the carbon fibers modified with the DBD at an atmospheric pressure show a significant increase in oxygen-containing groups, such as C–O,C=O and O–C=O. The results of SFC tests show that the treated carbon fibers composites could possess excellent interfacial properties with mixed resins. These results demonstrate that the surfaces of the carbon fibers samples are more active, hydrophilic and rough after plasma treatments using a DBD operating in ambient argon.

Optimum dispersion conditions and interfacial modification of carbon fiber and CNT–phenolic composites by atmospheric pressure plasma treatment

Electric resistance measurements were used to determine the optimal dispersion conditions for carbon nanotubes (CNTs) in phenolic resins. Plasma treatment is frequently used to modify carbon fiber surfaces to improve adhesion of the fibers to matrices. Such treatment might also influence carbon fiber tensile strength. In order to determine the effect of atmospheric pressure plasma treatment on carbon fiber tensile strength and interfacial bonding strength, change in tensile strength of the fiber was studied at different gage lengths before and after the plasma treatment. The wettability of carbon fibers was improved significantly after only 10s of plasma treatment. Such plasma treatment resulted in a decrease in the advancing contact angle from 65° to 28°. Surface energies of carbon fiber and CNT–phenolic composites were measured using the Wilhelmy plate technique, indicating that the work of adhesion between plasma treated carbon fibers and CNT–phenolic composites was higher than it before plasma modification. The interfacial shear strength (IFSS) and apparent modulus were also increased by plasma treatment of the carbon fibers.

Influence of Excilamp Treatment on Characteristics of Carbon Fibers

To activate the surface of carbon fiber for better reinforced composites, the Xe2* excilamp was applied. The scanning electron microscopy (SEM) showed that the surface of Xe2* excilamp-treated carbon fibers was rougher than that of the control. X-ray photoelectron spectroscopy (XPS) analysis indicated that the Excilamp-treated fibers possessed more polar functional groups than the control fibers. After 2 min of irradiation, the wetting rate of treated carbon fibers in epoxy resin in balance increased by about 150% compared with the control, and the short-beam strength of carbon fiber/epoxy composites increased 6.6%.

Electrochemically Pretreated Carbon Microfiber Electrodes as Sensitive HPLC-EC Detectors

The paper focuses on the analysis and detection of electroactive compounds using high-performance liquid chromatography (HPLC) combined with electrochemical detection (EC). The fabrication and utilization of electrochemically treated carbon fiber microelectrodes (CFMs) as highly sensitive amperometric detectors in HPLC are described. The applied pretreatment procedure is beneficial for analytical characteristics of the sensor as demonstrated by analysis of the model set of phenolic acids. The combination of CFM with separation power of HPLC technique allows for improved detection limits due to unique electrochemical properties of carbon fibers. The CFM proved to be a promising tool for amperometric detection in liquid chromatography.

Preparation, Performance and Analysis of Carbon Fibers with Dielectric Barrier Discharges Plasma Surface Treatment

The deposition of coatings on the surface of carbon fiber will be helpful to their appli-cations. However, they are unsuitable to be deposited due to their low surface free energies, poor wettability and poor adhesions. The objective of this work is to modify carbon fibers by Dielect-ric barrier discharges (DBD) in ambient argon. The chemical and physical changes induced by the treatments on carbon fibers surface are examined using contact angle measurements and X-ray photoelectron spectroscopy (XPS). The interfacial adhesion of CF/EP composites are analysised by a single filament pull-out test. The contact angles of the plasma-treated samples are visibly reduced than the untreated samples. XPS results reveal that the carbon fibers modified with the DBD at an atmospheric pressure show a significant increase in oxygen-containing groups, such as C–O,C=O and O–C=O. The results of IFSS tests show that the treated carbon fibers composit-es could possess excellent interfacial properties with mixed resins. These results demonstrate that the surfaces of the carbon fibers samples are more active, hydrophilic and rough after plasma treatments using a DBD operating in ambient argon.

Chemical interaction between carbon fibers and surface sizing

AbstractFunctional groups on the surface of Polyacrylonitrile (PAN)‐based carbon fibers and in fiber surface sizing are likely to react during the curing process of composites, and these reactions could affect the infiltration and adhesion between the carbon fibers and resin. T300B‐3000‐40B fibers and fiber surface sizing were heat‐treated at different temperatures, and the structural changes of both the fiber surface sizing and extracted sizing after heat treatment were investigated by Fourier transform infrared spectroscopy. The results show that the concentration of epoxy groups in both the fiber surface sizing and extracted sizing decreased with increasing heat‐treatment temperature and decreased to zero after treatment at 200°C. The concentration of epoxy groups in the extracted sizing was lower than that of the fiber surface sizing after treatment under the same conditions; this indicated that the rate of reaction between the carbon fibers and fiber surface sizing was higher than the reaction rate of the fiber surface sizing system. X‐ray photoelectron spectroscopy analysis reveals that the content of CO bonds and activated carbon atoms on the surface of the desized treated carbon fibers was the highest when the heat‐treatment temperature was 150°C; this proved the reaction between the carbon fibers and the fiber surface sizing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Influence of molecular weight on performance properties of polyethersulphone and its composites with carbon fabric

The effect of molecular weight (MW) of a polymer on the wettability of fibers and its influence on the performance properties need to be addressed in detail. Specialty polymer, viz. polyethersulphone (PES), with varying MW was selected as a matrix material to develop the composites with carbon fabric (CF). Since carbon fiber is inert towards the matrix, cold remote nitrogen–oxygen plasma (CRNOP) treatment was employed to improve its chemical reactivity, by incorporating functional groups to promote the fiber–matrix adhesion. Evaluation of mechanical and sliding wear properties of polymers and composites led to the conclusion that the CRNOP treatment was beneficial to enhance performance properties. The MW and MFI have inverse relation. MW proved to be a controlling parameter for pristine polymers while melt flow index (MFI) was the decisive parameter for the performance of composites. Perforations and increased roughness on the treated carbon fiber, as observed by the field emission scanning electron microscopy (FESEM), were responsible for the improved fiber–matrix adhesion and hence performance properties.

Influence of mechanically treated carbon fibre additives on structure formation and properties of autoclaved aerated concrete

This work deals with investigations on effect of chemically and thermally resistant carbon fibre (CF) additives of various mechanical treatment on structure formation and properties of autoclaved aerated concrete (AAC). It was established that various methods of CF crushing, such as mixing with sand pulp, chopping, grounding, milling in dry way, milling in wet way cause different fineness of disintegrated CF particles and that along with increase in fineness, the crystallinity of AAC binding material is growing what leads to the following: increase in compressive strength by 6–22%; after exposure at temperature of 700 °C, decrease in thermal deformation by 5–20%; decrease in mass loss by 7–20%. Upon addition of mechanically not treated CF of 0.1%, the flexural strength increases by 29% versus that of AAC without CF additive. The effect of added mechanically treated CF on flexural strength is less than that of not treated CF. Due to increased CF fineness, the flexural strength increment drops from 21% to 4%. Basing on the results obtained, one can draw a conclusion that CF particles resulted in mechanical treatment have an activated surface and can serve as nuclei of crystallization during the hardening of AAC binding material, which contains a mechanically treated CF additive, thus causing increase in crystallinity of hardened binding material and, consequently, improved performance of AAC.

Tribological studies on polyetherimide composites based on carbon fabric with optimized oxidation treatment

Abstract Chemical inertness and hence limited wettability of carbon fibers (CF) with a selected matrix is the major problem for exploiting its full potential as reinforcement. Oxidation of CF with nitric acid is a classical method for treatment of CF which increases oxidative groups on fiber surface leading to enhanced adhesion with the matrix, but at the cost of damage to the fibers leading to reduction in strength. Thus the treatment has to be for optimum time to strike a balance between these opposite effects so that the composite will have best combination of performance properties. In depth studies on this aspect, however, are not reported especially in tribological studies. Hence nitric acid treatment was employed to carbon fabric for various time intervals (15–180 min). Eight composites with untreated and acid treated fabrics were developed based on polyetherimide (PEI) matrix and evaluated for mechanical and abrasive wear properties. It was observed that 90 min treatment time was ideal one to achieve maximum possible enhancement in strength and tribological properties. Fiber–matrix adhesion was improved due to inclusion of oxygenated functional groups as supported by Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and increased surface roughening of fibers as supported by scanning electron microscopic (SEM) studies.

Studies for Wear Property Correlation for Carbon Fabric-Reinforced PES Composites

Polyethersulfone (PES) composites were developed with carbon fabric (CF). Cold remote nitrogen oxygen plasma (CRNOP) treatment was employed to the CF to incorporate functional groups and promote fiber–matrix adhesion. This study includes the effect of PES melt flow index (MFI) on the wettability of CF and its influence on fretting wear performance. Evaluations of fretting wear properties of composites led to the conclusion that the CRNOP treatment proved beneficial to enhance performance properties significantly. Polymer MFI and treatment to CF proved to be the decisive parameters for controlling performance of composites apart from operating parameters. Perforations on the treated carbon fiber, evidently observed by FESEM, improved the fiber–matrix adhesion, and hence the performance properties. Artificial neuron network (ANN) was used for prediction of the wear behavior of composites.

Influence of Neuropeptide Y and antidepressants upon cerebral monoamines involved in depression: An in vivo electrochemical study

Neuropeptide Y (NPY) and its receptors are present in the peripheral as well as the central nervous system (CNS). In vitro data have indicated NPY as an important mediator in the regulation of different diseases e.g. related to obesity, anxiety, depression, pain, memory loss and sleep disorders. In particular, studies of NPY levels in the cerebral spinal fluid (CSF) of depressed patients have shown a significant reduction of NPY levels when compared to control subjects. In addition, decreased concentrations of NPY were measured in the brain of suicide victims. These studies suggest that a reduction in cerebral NPY function may be associated with depressive symptoms. In the present work, a putative interaction between NPY, the catecholaminergic and serotonergic systems has been analysed by means of in vivo Differential Pulse Voltammetry (DPV) with treated carbon fibre micro electrodes (mCFE). It appeared that DPV with mCFE is an efficacious tool to monitor in vivo basal levels of catechols (Peak 2) and indoles (Peak 3) in discrete brain regions of rodents. Furthermore, it is shown that the peptidergic signal (Peak 5) simultaneously recorded with Peaks 2 and 3 in the amygdala could correspond to the oxidation of basal endogenous NPY. In addition, pharmacological treatments performed in vivo with exogenous NPY and with Y1 receptor antagonist BIBP3226 have indicated that these compounds interact positively with endogenous catecholaminergic and serotoninergic systems, in a way similar to that of the antidepressants imipramine and fluoxetine. In addition, the observed decrease of endogenous Peak 5 after treatment with imipramine or fluoxetine could be related to the concomitant stimulation of the catecholaminergic system with consequent reduced need for endogenous NPY. This would imply that NPY could be one of the endogenous chemicals acting on the maintenance of the mood. Thus, an antidepressant therapeutic potential of NPY and related compounds (e.g. BIBP3226) could be proposed.

Effect of heat treatment on carbon fiber surface properties and fibers/epoxy interfacial adhesion

Carbon fiber surface properties are likely to change during the molding process of carbon fiber reinforced matrix composite, and these changes could affect the infiltration and adhesion between carbon fiber and resin. T300B fiber was heat treated referring to the curing process of high-performance carbon fiber reinforced epoxy matrix composites. By means of X-ray photoelectron spectroscopy (XPS), activated carbon atoms can be detected, which are defined as the carbon atoms conjunction with oxygen and nitrogen. Surface chemistry analysis shows that the content of activated carbon atoms on treated carbon fiber surface, especially those connect with the hydroxyl decreases with the increasing heat treatment temperature. Inverse gas chromatography (IGC) analysis reveals that the dispersive surface energy γ S d increases and the polar surface energy γ S sp decreases as the heat treatment temperature increases to 200. Contact angle between carbon fiber and epoxy E51 resin, which is studied by dynamic contact angle test (DCAT) increases with the increasing heat treatment temperature, indicating the worse wettability comparing with the untreated fiber. Moreover, micro-droplet test shows that the interfacial shear strength (IFSS) of the treated carbon fiber/epoxy is lower than that of the untreated T300B fiber which is attributed to the decrement of the content of reactive functional groups including hydrogen group and epoxy group.

Effect of Fiber Acid Treatment on the Dynamic Mechanical Properties of Unsaturated Polyester/Carbon Fiber Unidirectional Composites

In this study, the surface modification of carbon fiber by sulfuric acid is investigated. Atomic Force Microscopy was employed to capture the corresponding changes in the surface roughness of the carbon fiber. Moreover, using treated and untreated fibers, unsaturated polyester unidirectional composite rods were prepared and their flexural properties were determined by three-point bending and dynamic mechanical thermal analysis. The results indicated that the carbon fiber surface roughness increases in all samples. It is also found that treating the fiber decreases the magnitude of loss modulus. Besides, the flexural strength of composites made of the treated carbon fiber significantly increased.

Adsorption of H<sub>2</sub>S and SO<sub>2</sub> on Activated Carbon Fibers Modified by Ammonium Nitrate

The enhancement effect of using PAN-based carbon fibers surface modified by ammonium nitrate for removing SO2 and H2S in moist air at room temperature was characterized and investigated. The pore structure of the samples so prepared was examined by adsorption measurement. Surface groups introduced by treatment with ammonium nitrate was assessed by xray photoelectron spectroscopy. The results show that the amount of sulfur dioxide and hydrogen sulfide adsorbed with the treated carbon fibers are increased by 112% and 93% and ammonium nitrate treatment improved original carbon fibers adsorption performance, not only by introducing nitrogen surface groups, but also by extending the surface area.