Carbon Fiber Samples Research Articles

Sizing effects on the interfacial shear strength of a carbon fibre reinforced two-component thermoplastic polymer

Here carbon fibre surface treatment conditions (current, bath conductivity, and sizing) gave a comprehensive set of 27 unique carbon fibre samples. Examination of the interfacial shear strength (IFSS) in a two-component polymethyl methacrylate resin via the V-notch shear test. Epoxy-sized fibres show a strong dependence on surface treatments and were widely variable (25.6 ± 0.72 to 38.5 ± 2.69 MPa). We suggest the epoxy sizing is soluble in the methylmethacrylate monomer and is removed from the surface before complete polymerisation. Adhesion in epoxy-sized fibres seemed linked to the ratio of oxygen and nitrogen on the fibre surface (determined by XPS). Polyamide-sized fibres possessed a smaller data variation (37.3 ± 3.34 to 33.4 ± 3.18 MPa), suggesting the polyamide-sizing masks the underlying surface chemistry of the fibre induced by the variations in surface treatment. A hybrid of these two outcomes was observed with the polyurethane sized fibres (36.1 ± 2.19 to 28.8 ± 2.82 MPa), suggesting a mixture of effects observed above.

Experimental investigation for the effect of fiber on the mechanical properties of light-weight concrete under dry and wet conditions

Purpose The purpose of this paper is to investigate the effect of steel and carbon fibers on the mechanical properties of light concrete in terms of tension strength, compressive strength and elastic modulus under completely dry and wet conditions. Design/methodology/approach In this study, the lightweight concrete made of Light Expanded Clay Aggregate (LECA) as coarse aggregate and sand as fine aggregate was used. To achieve a compressive strength of at least 20 MPa, microsilica was used 10 percent by weight of cement. In order to compensate for the reduction of tension strength of concrete, steel and carbon fibers were used with three volume ratio of 0.5, 1 and 1.5 percent in concrete. The results of concrete specimens were studied at the age of 7, 28, 42 and 90 days under controlled dry and wet conditions. Findings The results showed that the addition of steel and carbon fibers to the concrete mixture would reduce the drop in slump. Also, the use of steel and carbon fibers plays a significant role in increasing the tension strength of the specimens. Furthermore, the highest increase in tension strength of steel and carbon fiber samples was 83.3 and 50 percent, respectively, than the non-fibrous specimen when evaluated at 90 days of age. Moreover, the steel and carbon fiber increased the water absorption of the samples. Adding steel and carbon fibers to a lightweight concretes mixture containing LECA aggregates plays a significant role in increasing the modulus of elasticity of the samples. The highest increase in the elastic modulus of steel and carbon fibers was 18.9 and 35.4 percent, respectively, than the non-fibrous specimen at 28 days of age. Originality/value In this paper, the authors investigated the mechanical properties of steel fiber and carbon reinforced concrete. Also, according to the conditions of storage of samples and the age of concrete (day), the experiments were carried out on samples.

CATALYSTS OF ACID-BASE PROCESS ON THE BASIS OF THE MODIFIED CARBON FIBER

The functionalization of the carbon fiber based on polyacrylonitrile with sulfur-containing groups of high acidity was carried out in order to obtain the acid-base processes catalysts. Fibers were treated with sulfur vapors in the temperature range of 400-800°C, followed by surface oxidation with 30% hydrogen peroxide solution. Modified samples were investigated by chemical analysis, thermo-programmed desorption with mass spectrometric registration of products, IR spectroscopy and thermogravimetry. It is shown that the obtained materials contain SO3H-functional groups and oxygen-containing groups (carboxyl, lactone, phenolic, etc.) formed in the surface layer during the oxidation of the fiber surface. The chemical analysis showed that the concentration of sulfur in the samples of the modified fiber is 1.6-6.5 mmol/g. The synthesized samples have a satisfactory thermal stability.
 The synthesized catalysts were investigated in the model reaction - gas phase dehydration of isopropyl alcohol. It was found that obtained SO3H-containing carbon fibers were catalytically active and had high propylene selectivity. For all the samples obtained there is a complete conversion of alcohol into propylene. The activity of modified carbon fiber samples in the reaction indicated is a fairly high, temperatures of the total conversion of alcohol into propylene are in the range of 160-190°C. During the study of synthesized catalysts in several cycles of catalysis it have been shown that within repeated use (3 cycles) of all modified fiber samples, the yield of propylene does not decrease, the activity remains stable - the temperature of the dehydration reaction remains unchanged or increases insignificantly (by 5-10ºС). The temperatures of complete conversion of isopropyl alcohol in propylene for synthesized catalysts are lower than the temperatures of destruction maxima of surface sulfogroups. Thus, modified carbon fibers can be used as low-temperature catalysts of acid-base processes, in particular dehydration of alcohols.

Effect of High Temperature and Marine Corrosion on Mineral Bonder in Fibre Retrofit over Epoxy Resin

Objectives: This project investigates the performance of mineral based composite in fibre retrofit under saline water corrosion as well as its behaviour at high temperatures in comparison to epoxy bonder. Methods/Experimental Analysis: Three types Fibre Reinforced Polymer (FRP) materials were used in retrofitting standard cylindrical concrete specimens subjected to various damage levels prior to its retrofit. The specimens were wrapped using epoxy resin and Mineral Based Composite (MBC) bonders before they were tested for their mechanical properties under high temperature. Apart from that, the carbon fibre samples were placed in marine conditions in order to investigate the effect of corrosion. Findings: Carbon fibre proved to be the most efficient retrofit with mineral bonder under various levels of pre-existing damage followed by aramid and e-glass fibres. Further, the MBC mix proportions were varied to accommodate industrial by-products such as class F flyash and metakaolin. The ideal mix proportions was later determined after a series of compressive tests and the finalized ratio was used in FRP retrofits under high temperature (100o C) alongside offshore environmental conditions. Epoxy had detrimental effects and lost its bonding capacity under these conditions whereas mineral composite established itself as a superior bonder. Around 205% strength development was observed in the tensile behaviour of carbon fibre retrofit and 30% replacement of cement with flyash seemed to perform optimally. Under severe temperature and marine corrosion, MBC bonded CFRP retrofit proved to be most durable. Thus, the significance of rehabilitating damaged concrete structures can be carried out globally using mineral based FRP strengthening technique which is sustainable solution. Application: From all the findings, it can be suggested that mineral bonding admixture can be adopted as a potential replacement for harmful epoxy resin under increased deterioration levels. Keywords: Epoxy, FRP Retrofit, Rehabilitation, Sustainability, Temperature, MBC

EXPERIMENTAL FINDING OF FRACTURE TOUGHNESS CHARACTERISTICS AND THEORETICAL MODELING OF CRACK PROPAGATION PROCESSES IN CARBON FIBER SAMPLES UNDER CONDITIONS OF ADDITIVE PRODUCTION

The relevance of the problem stated in this article is that the development of aerospace technology increased the demand for good quality materials. An important issue is ensuring durability in conditions of longterm loads and in conditions of damage development. One of the criteria that ensure the toughness of the material is crack resistance. The aim of the work is to study the interlayer crack resistance (fracture toughness) under loading under conditions of separation and transverse shear, interlayer strength, as well as the effect of temperature on interlayer strength, mechanical tensile properties. A comparison of the values of interlayer crack resistance GIС (separation) and GIIС (shear) and of mechanical tensile properties and interlayer strength of carbon fiber samples is made. The main methods for studying this problem were the short-beam method, the DCB method, the ENF method. The results of the experimental data were compared with modeling the processes of the appearance and development of cracks in the finite element complexes ABAQUS and Ansys based on the VVCT models, cohesive elements. Deviations from the experiment were found and conclusions were drawn that the point of application of the load had to be shifted from the edge of the sample, which will reduce the initial separation and increase the stiffness of the sample. Due to the fact that the cohesion zone model is very sensitive to input parameters, it is necessary to know many parameters and take into account a large number of factors. The practical importance of this work is to show how to use the VCCT model to obtain the critical load of the germination of the first crack. The research technique can be used for further experiments, including simulation further stratification with low inaccuracy.

Lignin as a Functional Green Coating on Carbon Fiber Surface to Improve Interfacial Adhesion in Carbon Fiber Reinforced Polymers.

While intensive efforts are made to prepare carbon fiber reinforced plastics from renewable sources, less emphasis is directed towards elaborating green approaches for carbon fiber surface modification to improve the interfacial adhesion in these composites. In this study, we covalently attach lignin, a renewable feedstock, to a graphitic surface for the first time. The covalent bond is established via aromatic anchoring groups with amine functions taking part in a nucleophilic displacement reaction with a tosylated lignin derivative. The successful grafting procedures were confirmed by cyclic voltammetry, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. Both fragmentation and microdroplet tests were conducted to evaluate the interfacial shear strength of lignin coated carbon fiber samples embedded in a green cellulose propionate matrix and in a commercially used epoxy resin. The microdroplet test showed ~27% and ~65% increases in interfacial shear strength for the epoxy and cellulose propionate matrix, respectively. For the epoxy matrix covalent bond, it is expected to form with lignin, while for the cellulosic matrix hydrogen bond formation might take place; furthermore, plastisizing effects are also considered. Our study opens the gates for utilizing lignin coating to improve the shear tolerance of innovative composites.

Design and Manufacturing Process of Micro Air Vehicles

This paper shows shortly the designing, optimization and manufacturing process of light and compact, carbon fiber MAV. It also covers testing and results. The main purpose was to make an innovative prototype of UAV which is easy to transport, assembly and carry as much high volume payload as possible. The optimization process started from defining the constrains. To gain information needed to choose the best solution and perform optimization, authors made many tests. The material, which was chosen, had to be as light and durable as possible - this characteristics were later checked in tensile test of carbon fiber samples. The main optimization algorithm do initial research about the rest parameters of aircraft. The point was to narrow the range of analyzed chord’s values and find the best motors. For better performance the original airfoil was developed. It works perfectly in low Reynolds number area and has perfect characteristics for high-lift airfoils, compared to similar. It was later checked in CFD. The special manufacturing process of carbon fiber airplane was designed. After all the construction was tested. The successful flight tests confirmed that design process was appropriate and done well. All theoretical assumptions were also right.

MEASUREMENT OF STRAINS IN CARBON-REINFORCED POLYMER COMPOSITE PRODUCTS AT ELEVATED TEMPERATURES USING FIBER-OPTIC SENSORS

The main task of the contribution was the estimation of the possibility of using Fiber Bragg Gratings as a mean of measuring the deformation in standard carbon fiber samples at elevated temperatures. The article presents the results of experiments on the measurement of deformations in a carbon sample using Fiber Bragg Gratings on an optical fiber. Deformations were measured in the process of stretching the sample at different temperatures (range from 20 to 140 °C). It is shown that FBGs integrated into the sample material give more stable, reproducible readings, unlike to inlay on the outer surface. It has been established that the use of several FBGs with different sensitivity to temperature or deformation (created by mechanically decoupling the sensor from the sample) makes it possible to compensate the effect of temperature when measuring deformations. The quantitative results of measurements are provided.

Multi-functional nanotechnology integration for aeronautical structures performance enhancement

Purpose The purpose of this paper is to evaluate the applicative potentiality of functional/self-responsive materials in aeronautics. In particular, the study aims to experimentally validate the enhancement of structural performances of carbon fibers samples in the presence of nanofillers, as multi-walled carbon nanontubes or microcapsules for the self-healing functionality. Design/methodology/approach The paper opted for a mechanical study. Experimental static and dynamic tests on “blank” and modified formulations were performed in order to estimate both strength and damping parameters. A cantilever beam test set-up has been proposed. As a parallel activity, a numerical FE approach has been introduced to assess the correct modeling of the system. Findings The paper provides practical and empirical insights about how self-responsive materials react to mechanical solicitations. It suggests that reinforcing a sample positively affects the samples properties since they, de facto, improve the global structural performance. This work highlights that the addition of carbon nanotubes strongly improves the mechanical properties with a simultaneous slight enhancement in the damping performance. Damping properties are, instead, strongly enhanced by the addition of self-healing components. A balanced combination of both fillers could be adopted to increase electrical conductivity and to improve global performance in damping and auto-repairing properties. Practical implications The paper includes implications for the use of lightweight composite materials in aeronautics. Originality/value This paper fulfills an identified need to study new lightweight self-responsive smart materials for aeronautical structural application.

Carbon Fiber Tow Inspection Technique Using Software Defined Radios

Inline inspection of carbon fiber tow is desired to enable rapid feedback to key fabrication process parameters. The tow is delicate in that it necessitates wireless techniques to remotely probe the tow properties to avoid damage during production. In this article, we investigate the use of software defined radios (SDRs) to measure microwave signal attenuation through the tow. Carbon fiber samples that have undergone different process conditions are measured with the system, and measurements exhibit over 10 dB in variation based on the process conditions. These measurements are correlated against results from conventional physical analysis. The developed system and measurement technique show promise as a method to wirelessly inspect carbon fiber tow using SDR.

Study on energy absorption capacity of carbon fiber tube

In order to study the energy absorbing capacity of carbon fiber pipe in collision, a material test bench was designed with the help of collision sled. The influence of induced holes on the mechanical properties of carbon fiber sample was studied. Through two different ways of collision, the torn and bending energy absorbing capacity of the carbon fiber square tube was obtained, and the way to increase the energy absorption capacity of the carbon fiber square tube was discussed.

Fatigue Testing Method of Test Coupon and Structurally Equivalent Samples of Carbon Fiber Reinforced Polymer for Gas Turbine Engine Parts and Assemblies

The carbon fiber reinforced polymer composite are widely used in industry as major structural materials. They represent the greatest interest for the production of gas turbine engines parts because of their high specific strength. But before adaptation these materials into the structure, it is necessary to conduct a number of tests, both on test coupon and on structurally equivalent samples for determining physical, in particular, fatigue properties of these materials. However, the high cost of manufacturing coupons for such tests has a negative impact on the adaptation of carbon fiber reinforced polymer composite into the composition of final products. In this paper it is presented a method for fatigue tests of test coupon and structurally equivalent samples of carbon fiber reinforced polymer, aimed at reducing the consumption of coupons which are necessary for obtaining fatigue properties. Based on the developed method, a series of carbon fiber coupons was tested and the fatigue limit was obtained. At the same time, the use of coupons was minimized.

Chemical and electrochemical treatment effects on the morphology, structure, and electrochemical performance of carbon fiber with different graphitization indexes

The association of capacitive charging of the double-layer and a faradic redox reaction is desirable on carbon fiber (CF) when oxygen functional groups or other heteroatoms are present on its surface enhancing its capacitive properties. In this work, a systematic study of carbon fiber produced at three different heat treatment temperatures (HTT) of 1000, 1500, and 2000 °C was performed upon two approaches: middle (chemical) and severe (electrochemical) oxidative treatments. Morphological, structural, and surface chemical changes were investigated by field emission gun-scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Electrochemical responses were analyzed by galvanostatic charge/discharge, electrochemical impedance spectroscopy, and cyclic voltammetry. Raman results showed that the electrochemical oxidation promoted structural variation on CF samples independently of their HTT. Concerning the specific capacitance, the results indicated that chemical treatment was more effective for CF1000 than those for CF1500 and CF2000. This behavior may be attributed to higher amount of oxygen on its surface as well as its lower structural ordering. Otherwise, for CF1000, the electrochemical treatment increased its resistivity. However, for CF1500 and CF2000, which present higher graphitization levels and less heteroatom contents, greater capacitance values were observed after their electrochemical oxidative treatment.

Experimental Study of Deformed States of Carbon Plastics Surface Layers in Axial Tension by Digital Images Correlation Method

This paper presents the results of experimental studies of the deformed state distribution evolution of carbon fiber reinforced plastic surface layers under tension. Structural spatial deformation elements evolve as the total deformation increases. The size of the samples of carbon fiber is 250 × 12 × 1.5 mm. The matrix of the composite is the two-component epoxy compound Resin 530+. Filler composite is the unidirectional carbon fabric Tape 530. The layered deformation distribution on the surface of the sample changes into a more uniform distribution. The laminated distribution is characterized by localized deformation foci with dimensions of 2 ÷ 6 mm and a low deformation value. Homogeneous distribution is characterized by finely dispersed regions of local deformations with dimensions less than 1 mm. Local foci of deformations do not merge in the macro-region on the surface of the CFRP, which indicates a uniform distribution of deformations in the composite until destruction. The process of destruction of carbon fiber begins when the total deformation value reaches 1.8%.DOI 10.14258/izvasu(2018)1-10

Mechanical Characterization of Carbon Fibres Recycled by Steam Thermolysis: A Statistical Approach

The recent development of technologies for recycling carbon fibre reinforced plastics (CFRPs) leads to the need to evaluate the mechanical response of recycled carbon fibres. As these fibres are likely to be degraded during the recycling treatment, it is very important to determine their tensile residual properties so as to evaluate their ability as reinforcement for new composite materials. Carbon fibres reclaimed by a steam‐thermal treatment applied to degrade the epoxy resin matrix of a CFRP are here analysed. Two conditions were chosen so as to reach two degradation efficiency levels of the steam thermolysis. Several carbon fibre samples were selected for mechanical testing carried out either on single filaments using single fibre tensile tests or on fibre tows using bundle tensile tests. It is shown that the single fibre tensile test leads to a wide variability of statistical parameters derived from the analysis. Bundle tensile tests results were able to indicate that fibre strength of recycled carbon fibre is similar to corresponding as‐received carbon fibres thanks to a statistically relevant database. Wide number of tested filaments enabled indeed to obtain low scatters.

Flexible Polyaniline/Reduced Graphene Oxide/Carbon Fibers Composites Applied As Electrodes for Supercapacitors

Introduction Reduced graphene oxide has received extraordinary attention due to its many special properties, such as good conductivity, mechanical resistance, high accessible surface area (2630 m2 g-1), and good flexibility. These properties makes it the best candidate for flexible electrode materials. Nevertheless, according the literature, the facile agglomeration of graphene, due to the strong Π-Π interactions between their individual sheets, decreases the performance of graphene based materials [1]. In this context, the carbon fibers have been shown to be an ideal support for reduced graphene oxide (rGO). The carbon fiber (CF) offers the advantage for using as electrodes because its 3D structure decreases the packaging of the graphene sheets. In addition, it is not necessary any substrates or binders to prepare the binary composite rGO/CF. Thus, the use of CF is a plausible strategy to maximize the energy density of supercapacitors due to its high surface area as well as its good thermal and chemical stabilities. On the other hand, Polyaniline (PAni) has been considered as a promising pseudocapacitive material due to its high theoretical specific capacitance, low cost, high conductivity, and easy synthesis. In this work were proposed a combination of both double layer capacitance (binary composite rGO/CF) and ternary composite of PAni/rGO/CF associating the PAni pseudocapacitance to enhance this electrode capacitive response. The rGO/CF and PAni/rGO/CF samples were evaluated electrochemically, aiming their performance as electrodes in supercapacitors. Experimental Part CF samples were produced from polyacrylonitrile (PAN) precursor at heat treatment temperature of 1000 ºC using temperature steps of 330 ºC/h under inert atmosphere of nitrogen, reaching the maximum during 30 min up to its cooling down to room temperature. CF were cut in size of 1 cm2 and previously weighed. The rGO electrodeposition on CF was performed under potentiostatic mode, at a fixed potential of -1.25 V vs. Ag/AgCl/KCl(sat) for 15 min in a 25 mL of the graphene oxide (3mg mL-1) + 0.1 mol L-1 LiClO4 aqueous solution. In sequence, the PAni was electrodeposited on rGO/CF binary composite under galvanostatic mode with current density of 5 mA cm2 for 10 min in 0.5 mol L-1 H2SO4 aqueous with 0.1 mol L-1 aniline. The obtained ternary composite PAni/rGO/CF was washed in acid solution and vacuum dried. The morphological and structural analysis were obtained by Scanning Electronic Microscopy with field emission gun (SEM-FEG) and Raman spectroscopy, respectively. The electrode electrochemical characterizations were studied by cyclic voltammetry (CV) and charge/discharge tests. These measurements were performed in 1.0 mol L-1 H2SO4solution using a conventional three electrode cell. Results and discussion The SEM-FEG images showed aggregates with irregular and flakes-like shape and high particle density on CF substrate, which is a characteristic of the rGO. After electrochemical deposition, an uniform PAni coating was observed on binary rGO/CF composite, as shown in Figure 1 (b). Their Raman spectrum showed the characteristic C-Ṅ+ stretching vibration bands of the radical cations observed between 1319 cm-1 and 1340 cm-1 related to PAni emeraldine salt. The ternary composite CV curves presented a quasi rectangular shape with apparent redox peaks characteristic of emeraldine salt, indicating that the charge storage occurs by two process, the electric double layer and pseudocapacitive reactions. The charge-discharge profile of the PAni/rGO/CF electrodes, carried out at a current density of 1 mA cm-1, showed linear charge/discharge profile which indicates that capacitance is mainly due to electric double layer formation. The curves of the PAni/rGO/CF ternary composite showed a long time of the charge/discharge, improving the capacitance value, probably attributed to the electrode high surface area associated with the PAni pseudocapacitive behavior. Conclusion The PAni/rGO/CF composite electrodes were synthesized by electrochemical polymerization. The ternary composite presented a better performance in terms of specific capacitance and electrochemical reversibility than those of the conventional PAni films. The results showed that this ternary composite has a great potential as new promising electrode for applications in supercapacitors. Acknowledgments This work was supported by FAPESP 2016/13393-9, CAPES 086/2013 e CNPq. References S. Wang et al. Journal of Power Sources 299 (2015) 347-355. Figure 1

Porous TiO2 /BDD/CF Ternary Composite Applied on Brilhant Green Dye Electrochemical Oxidation

Introduction The dye contamination in wastewaters is mainly due to the textile sector which generating large volumes of toxic wastewater. In this context, dye oxidation has been studied using different chemical and electrochemical processes. Particularly, electrochemical technique depends on the high performance of electrode material. Boron doped diamond has appeared as singular material for electrochemical oxidation in wastewater treatment, mainly due to its very large potential widow, that allows reaching high anodic potential for hydroxyl radical (OH•) generation [1]. In this context, carbon fiber (CF) is a great interest substrate to grow BDD films because it exhibits high surface area allowing high active site density in a homogeneous porosity distribution. On the other hand, titanium dioxide (TiO2) is one of the most studied semiconducting oxide for different electrochemical applications because it is stable in both alkaline and acid media, besides its high electrochemically surface area [2]. Thus, ternary and binary composites were produced and characterized considering the constituent materials of carbon fibers (CF), boron doped diamond (BDD), and titanium dioxide (TiO2) as electrodes for electrochemical dye oxidation. Experimental CF samples were produced from polyacrylonitrile (PAN) precursor at heat treatment temperature of 1000 ºC and were cut in 25 x 25 mm2 to produce large electrode area. BDD films were grown on CF substrate by hot filament chemical vapor deposition (HFCVD) the following growth parameters: 750 °C, 30 Torr, 8h and gas mixture of 2/198 % CH4/H2. Boron source was obtained by an additional hydrogen line passing through a bubbler with B2O3 dissolved in methanol by controlling the B/C ppm ratio. TiO2 depositions on BDD/CF substrate was obtained by anodic hydrolysis of TiCl3 under potentiostatic mode, at a fixed potential of 0.75 V for 60 min in a 5 mmol.L-1 TiCl3 + 0.1 mol.L-1 KCl (pH = 2) aqueous solution. All the electrochemical experiments were performed in a conventional three-electrode glass cell, using a platinum wire as a counter electrode an Ag/AgCl/KCl (sat) as the reference electrode. Both composite materials were characterized by field emission gun-scanning electron microscopy (FEG-SEM) images, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). CF, TiO2/CF, and TiO2/BDD/CF were used as electrodes for electrooxidation of the Brilliant Green dye at different current densities using 100 mg L-1 of the Brilliant Green dye in K2SO4 0.1 mol L-1 solution for 300 min. Their efficiency was analyzed by UV/VIS Spectrophotometry and by Total Organic Carbon techniques considering the influence of the electrode characteristics in the degradation process. Results The binary and ternary TiO2/CF and TiO2/BDD/CF composites were firstly analyzed by FEG-SEM images taking into account these two sample considering the TiO2 deposits. The FEG-SEM images for TiO2/CF deposited at 30 min showed a thick TiO2 layer covering the fibers, with CF surface scratches or cracks completely filled by TiO2 film. For ternary composite, after 60 min of deposition the rougher film texture is dominant and homogenous covering all diamond grains. This morphology seems to be suitable to keep the contributions of these constituent material properties for TiO2/BDD/CF composite, mainly related to the BDD importance for electrochemical oxidation processes of organic pollutants. Concerning the Brilhant Green Dye electrochemical oxidation, the results showed that all the electrodes were efficient in the solution discolorization. Also, the organic compound mineralization showed a decrease according to TOC measurements of the electrolyzed samples. Considering the synergism between two good anode materials, BDD and TiO2 for organic electrodegradation, both of them binary and ternary composites presented the good performance. However, the ternary electrode, probably associated to its highest electrode surface area, showed the best performance. Conclusion Anodic hydrolysis of TiCl3 under potentiostatic mode was a suitable procedure to produce binary and ternary composites. In addition, both of them showed satisfactory results in electrolysis processes to degrade the Brilhant Green Dye. Acknowledgments This work was supported by FAPESP, Process 2016/13393-9, CAPES, and CNPq Brazilian Agencies.

Thermal Conductivity and Raman Spectra of Carbon Fibers

Due to its unique physical properties, carbon fiber (CF) has been widely studied for extensive application in aerospace and machinery. In this study, the thermal diffusivity of three kinds of CF sample is characterized by the transient electrothermal technique at room temperature. By subtracting the effect of radiative losses, the effective thermal diffusivity of CFs can be calculated as $$6.46\times 10^{-6}\,\hbox {m}^{2}\cdot \hbox {s}^{-1}$$ , $$6.58\times 10^{-6}\,\hbox {m}^{2}\cdot \hbox {s}^{-1}$$ and $$2.01\times 10^{-4}\,\hbox {m}^{2}\cdot \hbox {s}^{-1}$$ , respectively. For the first time, the emissivity coefficient of carbon fiber is calibrated as 0.78. Combined with Raman spectra and phonon scattering, we found that the better crystalline structure and low defect in CF have an obvious impact on its thermal diffusivity.

Self-sustaining hybrid electrode prepared from polyaniline, carbon nanotubes, and carbon fibers: morphological, structural, and electrochemical analyses

The self-sustaining hybrid electrode was prepared via chemical polymerization of aniline in acid medium containing dispersed carbon nanotubes (CNT), using carbon fiber (CF) as conducting substrate. The ternary composites called PAni/CNT/CF were characterized in order to evaluate their morphologies, structures, and thermal properties. The influence of the polyaniline (PAni) layer in the ternary composite properties was studied considering different deposition times on CF samples (30, 60, and 90 min). The ternary composite morphologies were observed by scanning electron microscopy while thermal structural analyses were obtained using thermogravimetric measurements. The structural features were analyzed by Raman scattering spectroscopy and Fourier transform infrared spectroscopy (FTIR). The possible interactions between PAni and CNT were discussed on the basis of Raman and FTIR spectra. These spectroscopic analyses also confirmed that the PAni present in the composite is in the emeraldine (ES) salt form. Furthermore, the ternary composites were also evaluated by electrochemical measurements such as cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) techniques. The results showed good charge storage capacity for ternary composites, in particular, for PAni/CNT/CF obtained with 90 min of deposition time, which exhibited specific capacitance of around 500 F g−1. Therefore, this electrode was selected to build a prototype of type I supercapacitor. This device presented specific capacitance of around 143 F g−1 after 3200 charge/discharge cycles.

Effect of high pressure hydrogen on the mechanical characteristics of single carbon fiber

In this study, carbon fiber was exposed to a pressure of 7MPa for 24h in high pressure chamber. The tensile test for carbon fiber was conducted to estimate the effect on the high pressure hydrogen in the atmosphere. To determine the tensile strength and Weibull modulus, approximately thirty carbon fiber samples were measured in all cases, and carbon fiber exposed to high pressure argon was evaluated to verify only the effect of hydrogen. Additionally, carbon fiber samples were annealed at 1950°C for 1h for a comparison with normal carbon fiber and then tested under identical conditions. The results showed that the tensile strength scatter of normal carbon fiber exposed to hydrogen was relatively wider and the Weibull modulus was decreased. Moreover, the tensile strength of the annealed carbon fiber exposed to hydrogen was increased, and these samples indicated a complex Weibull modulus because the hydrogen stored in the carbon fiber influenced the mechanical characteristic.